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RFC3010 - NFS version 4 Protocol

王朝other·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

Network Working Group S. Shepler

Request for Comments: 3010 B. Callaghan

Obsoletes: 1813, 1094 D. Robinson

Category: Standards Track R. Thurlow

Sun Microsystems Inc.

C. Beame

Hummingbird Ltd.

M. Eisler

Zambeel, Inc.

D. Noveck

Network Appliance, Inc.

December 2000

NFS version 4 Protocol

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2000). All Rights Reserved.

Abstract

NFS (Network File System) version 4 is a distributed file system

protocol which owes heritage to NFS protocol versions 2 [RFC1094] and

3 [RFC1813]. Unlike earlier versions, the NFS version 4 protocol

supports traditional file Access while integrating support for file

locking and the mount protocol. In addition, support for strong

security (and its negotiation), compound operations, client caching,

and internationalization have been added. Of course, attention has

been applied to making NFS version 4 operate well in an Internet

environment.

Key Words

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this

document are to be interpreted as described in RFC2119.

Table of Contents

1. IntrodUCtion . . . . . . . . . . . . . . . . . . . . . . . . 5

1.1. Overview of NFS Version 4 Features . . . . . . . . . . . . 6

1.1.1. RPC and Security . . . . . . . . . . . . . . . . . . . . 6

1.1.2. Procedure and Operation Structure . . . . . . . . . . . 7

1.1.3. File System Model . . . . . . . . . . . . . . . . . . . 8

1.1.3.1. Filehandle Types . . . . . . . . . . . . . . . . . . . 8

1.1.3.2. Attribute Types . . . . . . . . . . . . . . . . . . . 8

1.1.3.3. File System Replication and Migration . . . . . . . . 9

1.1.4. OPEN and CLOSE . . . . . . . . . . . . . . . . . . . . . 9

1.1.5. File locking . . . . . . . . . . . . . . . . . . . . . . 9

1.1.6. Client Caching and Delegation . . . . . . . . . . . . . 10

1.2. General Definitions . . . . . . . . . . . . . . . . . . . 11

2. Protocol Data Types . . . . . . . . . . . . . . . . . . . . 12

2.1. Basic Data Types . . . . . . . . . . . . . . . . . . . . . 12

2.2. Structured Data Types . . . . . . . . . . . . . . . . . . 14

3. RPC and Security Flavor . . . . . . . . . . . . . . . . . . 18

3.1. Ports and Transports . . . . . . . . . . . . . . . . . . . 18

3.2. Security Flavors . . . . . . . . . . . . . . . . . . . . . 18

3.2.1. Security mechanisms for NFS version 4 . . . . . . . . . 19

3.2.1.1. Kerberos V5 as security triple . . . . . . . . . . . . 19

3.2.1.2. LIPKEY as a security triple . . . . . . . . . . . . . 19

3.2.1.3. SPKM-3 as a security triple . . . . . . . . . . . . . 20

3.3. Security Negotiation . . . . . . . . . . . . . . . . . . . 21

3.3.1. Security Error . . . . . . . . . . . . . . . . . . . . . 21

3.3.2. SECINFO . . . . . . . . . . . . . . . . . . . . . . . . 21

3.4. Callback RPC Authentication . . . . . . . . . . . . . . . 22

4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1. OBTaining the First Filehandle . . . . . . . . . . . . . . 24

4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . . . 24

4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . . . 24

4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . . 25

4.2.1. General Properties of a Filehandle . . . . . . . . . . . 25

4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . . . 26

4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . . . 26

4.2.4. One Method of Constructing a Volatile Filehandle . . . . 28

4.3. Client Recovery from Filehandle EXPiration . . . . . . . . 28

5. File Attributes . . . . . . . . . . . . . . . . . . . . . . 29

5.1. Mandatory Attributes . . . . . . . . . . . . . . . . . . . 30

5.2. Recommended Attributes . . . . . . . . . . . . . . . . . . 30

5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . . 31

5.4. Mandatory Attributes - Definitions . . . . . . . . . . . . 31

5.5. Recommended Attributes - Definitions . . . . . . . . . . . 33

5.6. Interpreting owner and owner_group . . . . . . . . . . . . 38

5.7. Character Case Attributes . . . . . . . . . . . . . . . . 39

5.8. Quota Attributes . . . . . . . . . . . . . . . . . . . . . 39

5.9. Access Control Lists . . . . . . . . . . . . . . . . . . . 40

5.9.1. ACE type . . . . . . . . . . . . . . . . . . . . . . . . 41

5.9.2. ACE flag . . . . . . . . . . . . . . . . . . . . . . . . 41

5.9.3. ACE Access Mask . . . . . . . . . . . . . . . . . . . . 43

5.9.4. ACE who . . . . . . . . . . . . . . . . . . . . . . . . 44

6. File System Migration and Replication . . . . . . . . . . . 44

6.1. Replication . . . . . . . . . . . . . . . . . . . . . . . 45

6.2. Migration . . . . . . . . . . . . . . . . . . . . . . . . 45

6.3. Interpretation of the fs_locations Attribute . . . . . . . 46

6.4. Filehandle Recovery for Migration or Replication . . . . . 47

7. NFS Server Name Space . . . . . . . . . . . . . . . . . . . 47

7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . . 47

7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . . 48

7.3. Server Pseudo File System . . . . . . . . . . . . . . . . 48

7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . . 49

7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . . 49

7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . . 49

7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . . 49

7.8. Security Policy and Name Space Presentation . . . . . . . 50

8. File Locking and Share Reservations . . . . . . . . . . . . 50

8.1. Locking . . . . . . . . . . . . . . . . . . . . . . . . . 51

8.1.1. Client ID . . . . . . . . . . . . . . . . . . . . . . . 51

8.1.2. Server Release of Clientid . . . . . . . . . . . . . . . 53

8.1.3. nfs_lockowner and stateid Definition . . . . . . . . . . 54

8.1.4. Use of the stateid . . . . . . . . . . . . . . . . . . . 55

8.1.5. Sequencing of Lock Requests . . . . . . . . . . . . . . 56

8.1.6. Recovery from Replayed Requests . . . . . . . . . . . . 56

8.1.7. Releasing nfs_lockowner State . . . . . . . . . . . . . 57

8.2. Lock Ranges . . . . . . . . . . . . . . . . . . . . . . . 57

8.3. Blocking Locks . . . . . . . . . . . . . . . . . . . . . . 58

8.4. Lease Renewal . . . . . . . . . . . . . . . . . . . . . . 58

8.5. Crash Recovery . . . . . . . . . . . . . . . . . . . . . . 59

8.5.1. Client Failure and Recovery . . . . . . . . . . . . . . 59

8.5.2. Server Failure and Recovery . . . . . . . . . . . . . . 60

8.5.3. Network Partitions and Recovery . . . . . . . . . . . . 62

8.6. Recovery from a Lock Request Timeout or Abort . . . . . . 63

8.7. Server Revocation of Locks . . . . . . . . . . . . . . . . 63

8.8. Share Reservations . . . . . . . . . . . . . . . . . . . . 65

8.9. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . . 65

8.10. Open Upgrade and Downgrade . . . . . . . . . . . . . . . 66

8.11. Short and Long Leases . . . . . . . . . . . . . . . . . . 66

8.12. Clocks and Calculating Lease Expiration . . . . . . . . . 67

8.13. Migration, Replication and State . . . . . . . . . . . . 67

8.13.1. Migration and State . . . . . . . . . . . . . . . . . . 67

8.13.2. Replication and State . . . . . . . . . . . . . . . . . 68

8.13.3. Notification of Migrated Lease . . . . . . . . . . . . 69

9. Client-Side Caching . . . . . . . . . . . . . . . . . . . . 69

9.1. Performance Challenges for Client-Side Caching . . . . . . 70

9.2. Delegation and Callbacks . . . . . . . . . . . . . . . . . 71

9.2.1. Delegation Recovery . . . . . . . . . . . . . . . . . . 72

9.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . . 74

9.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . . . 74

9.3.2. Data Caching and File Locking . . . . . . . . . . . . . 75

9.3.3. Data Caching and Mandatory File Locking . . . . . . . . 77

9.3.4. Data Caching and File Identity . . . . . . . . . . . . . 77

9.4. Open Delegation . . . . . . . . . . . . . . . . . . . . . 78

9.4.1. Open Delegation and Data Caching . . . . . . . . . . . . 80

9.4.2. Open Delegation and File Locks . . . . . . . . . . . . . 82

9.4.3. Recall of Open Delegation . . . . . . . . . . . . . . . 82

9.4.4. Delegation Revocation . . . . . . . . . . . . . . . . . 84

9.5. Data Caching and Revocation . . . . . . . . . . . . . . . 84

9.5.1. Revocation Recovery for Write Open Delegation . . . . . 85

9.6. Attribute Caching . . . . . . . . . . . . . . . . . . . . 85

9.7. Name Caching . . . . . . . . . . . . . . . . . . . . . . . 86

9.8. Directory Caching . . . . . . . . . . . . . . . . . . . . 87

10. Minor Versioning . . . . . . . . . . . . . . . . . . . . . 88

11. Internationalization . . . . . . . . . . . . . . . . . . . 91

11.1. Universal Versus Local Character Sets . . . . . . . . . . 91

11.2. Overview of Universal Character Set Standards . . . . . . 92

11.3. Difficulties with UCS-4, UCS-2, Unicode . . . . . . . . . 93

11.4. UTF-8 and its solutions . . . . . . . . . . . . . . . . . 94

11.5. Normalization . . . . . . . . . . . . . . . . . . . . . . 94

12. Error Definitions . . . . . . . . . . . . . . . . . . . . . 95

13. NFS Version 4 Requests . . . . . . . . . . . . . . . . . . 99

13.1. Compound Procedure . . . . . . . . . . . . . . . . . . . 100

13.2. Evaluation of a Compound Request . . . . . . . . . . . . 100

13.3. Synchronous Modifying Operations . . . . . . . . . . . . 101

13.4. Operation Values . . . . . . . . . . . . . . . . . . . . 102

14. NFS Version 4 Procedures . . . . . . . . . . . . . . . . . 102

14.1. Procedure 0: NULL - No Operation . . . . . . . . . . . . 102

14.2. Procedure 1: COMPOUND - Compound Operations . . . . . . . 102

14.2.1. Operation 3: ACCESS - Check Access Rights . . . . . . . 105

14.2.2. Operation 4: CLOSE - Close File . . . . . . . . . . . . 108

14.2.3. Operation 5: COMMIT - Commit Cached Data . . . . . . . 109

14.2.4. Operation 6: CREATE - Create a Non-Regular File Object. 112

14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting

Recovery . . . . . . . . . . . . . . . . . . . . . . . 114

14.2.6. Operation 8: DELEGRETURN - Return Delegation . . . . . 115

14.2.7. Operation 9: GETATTR - Get Attributes . . . . . . . . . 115

14.2.8. Operation 10: GETFH - Get Current Filehandle . . . . . 117

14.2.9. Operation 11: LINK - Create Link to a File . . . . . . 118

14.2.10. Operation 12: LOCK - Create Lock . . . . . . . . . . . 119

14.2.11. Operation 13: LOCKT - Test For Lock . . . . . . . . . 121

14.2.12. Operation 14: LOCKU - Unlock File . . . . . . . . . . 122

14.2.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . . 123

14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory . . . 126

14.2.15. Operation 17: NVERIFY - Verify Difference in

Attributes . . . . . . . . . . . . . . . . . . . . . . 127

14.2.16. Operation 18: OPEN - Open a Regular File . . . . . . . 128

14.2.17. Operation 19: OPENATTR - Open Named Attribute

Directory . . . . . . . . . . . . . . . . . . . . . . 137

14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open . . . . . . 138

14.2.19. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access 140

14.2.20. Operation 22: PUTFH - Set Current Filehandle . . . . . 141

14.2.21. Operation 23: PUTPUBFH - Set Public Filehandle . . . . 142

14.2.22. Operation 24: PUTROOTFH - Set Root Filehandle . . . . 143

14.2.23. Operation 25: READ - Read from File . . . . . . . . . 144

14.2.24. Operation 26: READDIR - Read Directory . . . . . . . . 146

14.2.25. Operation 27: READLINK - Read Symbolic Link . . . . . 150

14.2.26. Operation 28: REMOVE - Remove Filesystem Object . . . 151

14.2.27. Operation 29: RENAME - Rename Directory Entry . . . . 153

14.2.28. Operation 30: RENEW - Renew a Lease . . . . . . . . . 155

14.2.29. Operation 31: RESTOREFH - Restore Saved Filehandle . . 156

14.2.30. Operation 32: SAVEFH - Save Current Filehandle . . . . 157

14.2.31. Operation 33: SECINFO - Obtain Available Security . . 158

14.2.32. Operation 34: SETATTR - Set Attributes . . . . . . . . 160

14.2.33. Operation 35: SETCLIENTID - Negotiate Clientid . . . . 162

14.2.34. Operation 36: SETCLIENTID_CONFIRM - Confirm Clientid . 163

14.2.35. Operation 37: VERIFY - Verify Same Attributes . . . . 164

14.2.36. Operation 38: WRITE - Write to File . . . . . . . . . 166

15. NFS Version 4 Callback Procedures . . . . . . . . . . . . . 170

15.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . . 170

15.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . . 171

15.2.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . . 172

15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation . . 173

16. Security Considerations . . . . . . . . . . . . . . . . . . 174

17. IANA Considerations . . . . . . . . . . . . . . . . . . . . 174

17.1. Named Attribute Definition . . . . . . . . . . . . . . . 174

18. RPC definition file . . . . . . . . . . . . . . . . . . . . 175

19. Bibliography . . . . . . . . . . . . . . . . . . . . . . . 206

20. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . 210

20.1. Editor's Address . . . . . . . . . . . . . . . . . . . . 210

20.2. Authors' Addresses . . . . . . . . . . . . . . . . . . . 210

20.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . 211

21. Full Copyright Statement . . . . . . . . . . . . . . . . . 212

1. Introduction

The NFS version 4 protocol is a further revision of the NFS protocol

defined already by versions 2 [RFC1094] and 3 [RFC1813]. It retains

the essential characteristics of previous versions: design for easy

recovery, independent of transport protocols, operating systems and

filesystems, simplicity, and good performance. The NFS version 4

revision has the following goals:

o Improved access and good performance on the Internet.

The protocol is designed to transit firewalls easily, perform well

where latency is high and bandwidth is low, and scale to very

large numbers of clients per server.

o Strong security with negotiation built into the protocol.

The protocol builds on the work of the ONCRPC working group in

supporting the RPCSEC_GSS protocol. Additionally, the NFS version

4 protocol provides a mechanism to allow clients and servers the

ability to negotiate security and require clients and servers to

support a minimal set of security schemes.

o Good cross-platform interoperability.

The protocol features a file system model that provides a useful,

common set of features that does not unduly favor one file system

or operating system over another.

o Designed for protocol extensions.

The protocol is designed to accept standard extensions that do not

compromise backward compatibility.

1.1. Overview of NFS Version 4 Features

To provide a reasonable context for the reader, the major features of

NFS version 4 protocol will be reviewed in brief. This will be done

to provide an appropriate context for both the reader who is familiar

with the previous versions of the NFS protocol and the reader that is

new to the NFS protocols. For the reader new to the NFS protocols,

there is still a fundamental knowledge that is expected. The reader

should be familiar with the XDR and RPC protocols as described in

[RFC1831] and [RFC1832]. A basic knowledge of file systems and

distributed file systems is expected as well.

1.1.1. RPC and Security

As with previous versions of NFS, the External Data Representation

(XDR) and Remote Procedure Call (RPC) mechanisms used for the NFS

version 4 protocol are those defined in [RFC1831] and [RFC1832]. To

meet end to end security requirements, the RPCSEC_GSS framework

[RFC2203] will be used to extend the basic RPC security. With the

use of RPCSEC_GSS, various mechanisms can be provided to offer

authentication, integrity, and privacy to the NFS version 4 protocol.

Kerberos V5 will be used as described in [RFC1964] to provide one

security framework. The LIPKEY GSS-API mechanism described in

[RFC2847] will be used to provide for the use of user password and

server public key by the NFS version 4 protocol. With the use of

RPCSEC_GSS, other mechanisms may also be specified and used for NFS

version 4 security.

To enable in-band security negotiation, the NFS version 4 protocol

has added a new operation which provides the client a method of

querying the server about its policies regarding which security

mechanisms must be used for access to the server's file system

resources. With this, the client can securely match the security

mechanism that meets the policies specified at both the client and

server.

1.1.2. Procedure and Operation Structure

A significant departure from the previous versions of the NFS

protocol is the introduction of the COMPOUND procedure. For the NFS

version 4 protocol, there are two RPC procedures, NULL and COMPOUND.

The COMPOUND procedure is defined in terms of operations and these

operations correspond more closely to the traditional NFS procedures.

With the use of the COMPOUND procedure, the client is able to build

simple or complex requests. These COMPOUND requests allow for a

reduction in the number of RPCs needed for logical file system

operations. For example, without previous contact with a server a

client will be able to read data from a file in one request by

combining LOOKUP, OPEN, and READ operations in a single COMPOUND RPC.

With previous versions of the NFS protocol, this type of single

request was not possible.

The model used for COMPOUND is very simple. There is no logical OR

or ANDing of operations. The operations combined within a COMPOUND

request are evaluated in order by the server. Once an operation

returns a failing result, the evaluation ends and the results of all

evaluated operations are returned to the client.

The NFS version 4 protocol continues to have the client refer to a

file or directory at the server by a "filehandle". The COMPOUND

procedure has a method of passing a filehandle from one operation to

another within the sequence of operations. There is a concept of a

"current filehandle" and "saved filehandle". Most operations use the

"current filehandle" as the file system object to operate upon. The

"saved filehandle" is used as temporary filehandle storage within a

COMPOUND procedure as well as an additional operand for certain

operations.

1.1.3. File System Model

The general file system model used for the NFS version 4 protocol is

the same as previous versions. The server file system is

hierarchical with the regular files contained within being treated as

opaque byte streams. In a slight departure, file and directory names

are encoded with UTF-8 to deal with the basics of

internationalization.

The NFS version 4 protocol does not require a separate protocol to

provide for the initial mapping between path name and filehandle.

Instead of using the older MOUNT protocol for this mapping, the

server provides a ROOT filehandle that represents the logical root or

top of the file system tree provided by the server. The server

provides multiple file systems by gluing them together with pseudo

file systems. These pseudo file systems provide for potential gaps

in the path names between real file systems.

1.1.3.1. Filehandle Types

In previous versions of the NFS protocol, the filehandle provided by

the server was guaranteed to be valid or persistent for the lifetime

of the file system object to which it referred. For some server

implementations, this persistence requirement has been difficult to

meet. For the NFS version 4 protocol, this requirement has been

relaxed by introducing another type of filehandle, volatile. With

persistent and volatile filehandle types, the server implementation

can match the abilities of the file system at the server along with

the operating environment. The client will have knowledge of the

type of filehandle being provided by the server and can be prepared

to deal with the semantics of each.

1.1.3.2. Attribute Types

The NFS version 4 protocol introduces three classes of file system or

file attributes. Like the additional filehandle type, the

classification of file attributes has been done to ease server

implementations along with extending the overall functionality of the

NFS protocol. This attribute model is structured to be extensible

such that new attributes can be introduced in minor revisions of the

protocol without requiring significant rework.

The three classifications are: mandatory, recommended and named

attributes. This is a significant departure from the previous

attribute model used in the NFS protocol. Previously, the attributes

for the file system and file objects were a fixed set of mainly Unix

attributes. If the server or client did not support a particular

attribute, it would have to simulate the attribute the best it could.

Mandatory attributes are the minimal set of file or file system

attributes that must be provided by the server and must be properly

represented by the server. Recommended attributes represent

different file system types and operating environments. The

recommended attributes will allow for better interoperability and the

inclusion of more operating environments. The mandatory and

recommended attribute sets are traditional file or file system

attributes. The third type of attribute is the named attribute. A

named attribute is an opaque byte stream that is associated with a

directory or file and referred to by a string name. Named attributes

are meant to be used by client applications as a method to associate

application specific data with a regular file or directory.

One significant addition to the recommended set of file attributes is

the Access Control List (ACL) attribute. This attribute provides for

directory and file access control beyond the model used in previous

versions of the NFS protocol. The ACL definition allows for

specification of user and group level access control.

1.1.3.3. File System Replication and Migration

With the use of a special file attribute, the ability to migrate or

replicate server file systems is enabled within the protocol. The

file system locations attribute provides a method for the client to

probe the server about the location of a file system. In the event

of a migration of a file system, the client will receive an error

when operating on the file system and it can then query as to the new

file system location. Similar steps are used for replication, the

client is able to query the server for the multiple available

locations of a particular file system. From this information, the

client can use its own policies to access the appropriate file system

location.

1.1.4. OPEN and CLOSE

The NFS version 4 protocol introduces OPEN and CLOSE operations. The

OPEN operation provides a single point where file lookup, creation,

and share semantics can be combined. The CLOSE operation also

provides for the release of state accumulated by OPEN.

1.1.5. File locking

With the NFS version 4 protocol, the support for byte range file

locking is part of the NFS protocol. The file locking support is

structured so that an RPC callback mechanism is not required. This

is a departure from the previous versions of the NFS file locking

protocol, Network Lock Manager (NLM). The state associated with file

locks is maintained at the server under a lease-based model. The

server defines a single lease period for all state held by a NFS

client. If the client does not renew its lease within the defined

period, all state associated with the client's lease may be released

by the server. The client may renew its lease with use of the RENEW

operation or implicitly by use of other operations (primarily READ).

1.1.6. Client Caching and Delegation

The file, attribute, and directory caching for the NFS version 4

protocol is similar to previous versions. Attributes and directory

information are cached for a duration determined by the client. At

the end of a predefined timeout, the client will query the server to

see if the related file system object has been updated.

For file data, the client checks its cache validity when the file is

opened. A query is sent to the server to determine if the file has

been changed. Based on this information, the client determines if

the data cache for the file should kept or released. Also, when the

file is closed, any modified data is written to the server.

If an application wants to serialize access to file data, file

locking of the file data ranges in question should be used.

The major addition to NFS version 4 in the area of caching is the

ability of the server to delegate certain responsibilities to the

client. When the server grants a delegation for a file to a client,

the client is guaranteed certain semantics with respect to the

sharing of that file with other clients. At OPEN, the server may

provide the client either a read or write delegation for the file.

If the client is granted a read delegation, it is assured that no

other client has the ability to write to the file for the duration of

the delegation. If the client is granted a write delegation, the

client is assured that no other client has read or write access to

the file.

Delegations can be recalled by the server. If another client

requests access to the file in such a way that the access conflicts

with the granted delegation, the server is able to notify the initial

client and recall the delegation. This requires that a callback path

exist between the server and client. If this callback path does not

exist, then delegations can not be granted. The essence of a

delegation is that it allows the client to locally service operations

such as OPEN, CLOSE, LOCK, LOCKU, READ, WRITE without immediate

interaction with the server.

1.2. General Definitions

The following definitions are provided for the purpose of providing

an appropriate context for the reader.

Client The "client" is the entity that accesses the NFS server's

resources. The client may be an application which contains

the logic to access the NFS server directly. The client

may also be the traditional operating system client remote

file system services for a set of applications.

In the case of file locking the client is the entity that

maintains a set of locks on behalf of one or more

applications. This client is responsible for crash or

failure recovery for those locks it manages.

Note that multiple clients may share the same transport and

multiple clients may exist on the same network node.

Clientid A 64-bit quantity used as a unique, short-hand reference to

a client supplied Verifier and ID. The server is

responsible for supplying the Clientid.

Lease An interval of time defined by the server for which the

client is irrevocably granted a lock. At the end of a

lease period the lock may be revoked if the lease has not

been extended. The lock must be revoked if a conflicting

lock has been granted after the lease interval.

All leases granted by a server have the same fixed

interval. Note that the fixed interval was chosen to

alleviate the expense a server would have in maintaining

state about variable length leases across server failures.

Lock The term "lock" is used to refer to both record (byte-

range) locks as well as file (share) locks unless

specifically stated otherwise.

Server The "Server" is the entity responsible for coordinating

client access to a set of file systems.

Stable Storage

NFS version 4 servers must be able to recover without data

loss from multiple power failures (including cascading

power failures, that is, several power failures in quick

succession), operating system failures, and hardware

failure of components other than the storage medium itself

(for example, disk, nonvolatile RAM).

Some examples of stable storage that are allowable for an

NFS server include:

1. Media commit of data, that is, the modified data has

been successfully written to the disk media, for

example, the disk platter.

2. An immediate reply disk drive with battery-backed on-

drive intermediate storage or uninterruptible power

system (UPS).

3. Server commit of data with battery-backed intermediate

storage and recovery software.

4. Cache commit with uninterruptible power system (UPS) and

recovery software.

Stateid A 64-bit quantity returned by a server that uniquely

defines the locking state granted by the server for a

specific lock owner for a specific file.

Stateids composed of all bits 0 or all bits 1 have special

meaning and are reserved values.

Verifier A 64-bit quantity generated by the client that the server

can use to determine if the client has restarted and lost

all previous lock state.

2. Protocol Data Types

The syntax and semantics to describe the data types of the NFS

version 4 protocol are defined in the XDR [RFC1832] and RPC [RFC1831]

documents. The next sections build upon the XDR data types to define

types and structures specific to this protocol.

2.1. Basic Data Types

Data Type Definition

_____________________________________________________________________

int32_t typedef int int32_t;

uint32_t typedef unsigned int uint32_t;

int64_t typedef hyper int64_t;

uint64_t typedef unsigned hyper uint64_t;

attrlist4 typedef opaque attrlist4<>;

Used for file/directory attributes

bitmap4 typedef uint32_t bitmap4<>;

Used in attribute array encoding.

changeid4 typedef uint64_t changeid4;

Used in definition of change_info

clientid4 typedef uint64_t clientid4;

Shorthand reference to client identification

component4 typedef utf8string component4;

Represents path name components

count4 typedef uint32_t count4;

Various count parameters (READ, WRITE, COMMIT)

length4 typedef uint64_t length4;

Describes LOCK lengths

linktext4 typedef utf8string linktext4;

Symbolic link contents

mode4 typedef uint32_t mode4;

Mode attribute data type

nfs_cookie4 typedef uint64_t nfs_cookie4;

Opaque cookie value for READDIR

nfs_fh4 typedef opaque nfs_fh4<NFS4_FHSIZE>;

Filehandle definition; NFS4_FHSIZE is defined as 128

nfs_ftype4 enum nfs_ftype4;

Various defined file types

nfsstat4 enum nfsstat4;

Return value for operations

offset4 typedef uint64_t offset4;

Various offset designations (READ, WRITE, LOCK, COMMIT)

pathname4 typedef component4 pathname4<>;

Represents path name for LOOKUP, OPEN and others

qop4 typedef uint32_t qop4;

Quality of protection designation in SECINFO

sec_oid4 typedef opaque sec_oid4<>;

Security Object Identifier

The sec_oid4 data type is not really opaque.

Instead contains an ASN.1 OBJECT IDENTIFIER as used

by GSS-API in the mech_type argument to

GSS_Init_sec_context. See [RFC2078] for details.

seqid4 typedef uint32_t seqid4;

Sequence identifier used for file locking

stateid4 typedef uint64_t stateid4;

State identifier used for file locking and delegation

utf8string typedef opaque utf8string<>;

UTF-8 encoding for strings

verifier4 typedef opaque verifier4[NFS4_VERIFIER_SIZE];

Verifier used for various operations (COMMIT, CREATE,

OPEN, READDIR, SETCLIENTID, WRITE)

NFS4_VERIFIER_SIZE is defined as 8

2.2. Structured Data Types

nfstime4

struct nfstime4 {

int64_t seconds;

uint32_t nseconds;

}

The nfstime4 structure gives the number of seconds and nanoseconds

since midnight or 0 hour January 1, 1970 Coordinated Universal

Time (UTC). Values greater than zero for the seconds field denote

dates after the 0 hour January 1, 1970. Values less than zero for

the seconds field denote dates before the 0 hour January 1, 1970.

In both cases, the nseconds field is to be added to the seconds

field for the final time representation. For example, if the time

to be represented is one-half second before 0 hour January 1,

1970, the seconds field would have a value of negative one (-1)

and the nseconds fields would have a value of one-half second

(500000000). Values greater than 999,999,999 for nseconds are

considered invalid.

This data type is used to pass time and date information. A

server converts to and from its local representation of time when

processing time values, preserving as much accuracy as possible.

If the precision of timestamps stored for a file system object is

less than defined, loss of precision can occur. An adjunct time

maintenance protocol is recommended to reduce client and server

time skew.

time_how4

enum time_how4 {

SET_TO_SERVER_TIME4 = 0,

SET_TO_CLIENT_TIME4 = 1

};

settime4

union settime4 switch (time_how4 set_it) {

case SET_TO_CLIENT_TIME4:

nfstime4 time;

default:

void;

};

The above definitions are used as the attribute definitions to

set time values. If set_it is SET_TO_SERVER_TIME4, then the

server uses its local representation of time for the time value.

specdata4

struct specdata4 {

uint32_t specdata1;

uint32_t specdata2;

};

This data type represents additional information for the device

file types NF4CHR and NF4BLK.

fsid4

struct fsid4 {

uint64_t major;

uint64_t minor;

};

This type is the file system identifier that is used as a

mandatory attribute.

fs_location4

struct fs_location4 {

utf8string server<>;

pathname4 rootpath;

};

fs_locations4

struct fs_locations4 {

pathname4 fs_root;

fs_location4 locations<>;

};

The fs_location4 and fs_locations4 data types are used for the

fs_locations recommended attribute which is used for migration

and replication support.

fattr4

struct fattr4 {

bitmap4 attrmask;

attrlist4 attr_vals;

};

The fattr4 structure is used to represent file and directory

attributes.

The bitmap is a counted array of 32 bit integers used to contain

bit values. The position of the integer in the array that

contains bit n can be computed from the expression (n / 32) and

its bit within that integer is (n mod 32).

0 1

+-----------+-----------+-----------+--

count 31 .. 0 63 .. 32

+-----------+-----------+-----------+--

change_info4

struct change_info4 {

bool atomic;

changeid4 before;

changeid4 after;

};

This structure is used with the CREATE, LINK, REMOVE, RENAME

operations to let the client the know value of the change

attribute for the directory in which the target file system

object resides.

clientaddr4

struct clientaddr4 {

/* see struct rpcb in RFC1833 */

string r_netid<>; /* network id */

string r_addr<>; /* universal address */

};

The clientaddr4 structure is used as part of the SETCLIENT

operation to either specify the address of the client that is

using a clientid or as part of the call back registration.

cb_client4

struct cb_client4 {

unsigned int cb_program;

clientaddr4 cb_location;

};

This structure is used by the client to inform the server of its

call back address; includes the program number and client

address.

nfs_client_id4

struct nfs_client_id4 {

verifier4 verifier;

opaque id<>;

};

This structure is part of the arguments to the SETCLIENTID

operation.

nfs_lockowner4

struct nfs_lockowner4 {

clientid4 clientid;

opaque owner<>;

};

This structure is used to identify the owner of a OPEN share or

file lock.

3. RPC and Security Flavor

The NFS version 4 protocol is a Remote Procedure Call (RPC)

application that uses RPC version 2 and the corresponding eXternal

Data Representation (XDR) as defined in [RFC1831] and [RFC1832]. The

RPCSEC_GSS security flavor as defined in [RFC2203] MUST be used as

the mechanism to deliver stronger security for the NFS version 4

protocol.

3.1. Ports and Transports

Historically, NFS version 2 and version 3 servers have resided on

port 2049. The registered port 2049 [RFC1700] for the NFS protocol

should be the default configuration. Using the registered port for

NFS services means the NFS client will not need to use the RPC

binding protocols as described in [RFC1833]; this will allow NFS to

transit firewalls.

The transport used by the RPC service for the NFS version 4 protocol

MUST provide congestion control comparable to that defined for TCP in

[RFC2581]. If the operating environment implements TCP, the NFS

version 4 protocol SHOULD be supported over TCP. The NFS client and

server may use other transports if they support congestion control as

defined above and in those cases a mechanism may be provided to

override TCP usage in favor of another transport.

If TCP is used as the transport, the client and server SHOULD use

persistent connections. This will prevent the weakening of TCP's

congestion control via short lived connections and will improve

performance for the WAN environment by eliminating the need for SYN

handshakes.

Note that for various timers, the client and server should avoid

inadvertent synchronization of those timers. For further discussion

of the general issue refer to [Floyd].

3.2. Security Flavors

Traditional RPC implementations have included AUTH_NONE, AUTH_SYS,

AUTH_DH, and AUTH_KRB4 as security flavors. With [RFC2203] an

additional security flavor of RPCSEC_GSS has been introduced which

uses the functionality of GSS-API [RFC2078]. This allows for the use

of varying security mechanisms by the RPC layer without the

additional implementation overhead of adding RPC security flavors.

For NFS version 4, the RPCSEC_GSS security flavor MUST be used to

enable the mandatory security mechanism. Other flavors, such as,

AUTH_NONE, AUTH_SYS, and AUTH_DH MAY be implemented as well.

3.2.1. Security mechanisms for NFS version 4

The use of RPCSEC_GSS requires selection of: mechanism, quality of

protection, and service (authentication, integrity, privacy). The

remainder of this document will refer to these three parameters of

the RPCSEC_GSS security as the security triple.

3.2.1.1. Kerberos V5 as security triple

The Kerberos V5 GSS-API mechanism as described in [RFC1964] MUST be

implemented and provide the following security triples.

column descriptions:

1 == number of pseudo flavor

2 == name of pseudo flavor

3 == mechanism's OID

4 == mechanism's algorithm(s)

5 == RPCSEC_GSS service

1 2 3 4 5

-----------------------------------------------------------------------

390003 krb5 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_none

390004 krb5i 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_integrity

390005 krb5p 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_privacy

for integrity,

and 56 bit DES

for privacy.

Note that the pseudo flavor is presented here as a mapping aid to the

implementor. Because this NFS protocol includes a method to

negotiate security and it understands the GSS-API mechanism, the

pseudo flavor is not needed. The pseudo flavor is needed for NFS

version 3 since the security negotiation is done via the MOUNT

protocol.

For a discussion of NFS' use of RPCSEC_GSS and Kerberos V5, please

see [RFC2623].

3.2.1.2. LIPKEY as a security triple

The LIPKEY GSS-API mechanism as described in [RFC2847] MUST be

implemented and provide the following security triples. The

definition of the columns matches the previous subsection "Kerberos

V5 as security triple"

1 2 3 4 5

-----------------------------------------------------------------------

390006 lipkey 1.3.6.1.5.5.9 negotiated rpc_gss_svc_none

390007 lipkey-i 1.3.6.1.5.5.9 negotiated rpc_gss_svc_integrity

390008 lipkey-p 1.3.6.1.5.5.9 negotiated rpc_gss_svc_privacy

The mechanism algorithm is listed as "negotiated". This is because

LIPKEY is layered on SPKM-3 and in SPKM-3 [RFC2847] the

confidentiality and integrity algorithms are negotiated. Since

SPKM-3 specifies HMAC-MD5 for integrity as MANDATORY, 128 bit

cast5CBC for confidentiality for privacy as MANDATORY, and further

specifies that HMAC-MD5 and cast5CBC MUST be listed first before

weaker algorithms, specifying "negotiated" in column 4 does not

impair interoperability. In the event an SPKM-3 peer does not

support the mandatory algorithms, the other peer is free to accept or

reject the GSS-API context creation.

Because SPKM-3 negotiates the algorithms, subsequent calls to

LIPKEY's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality

of protection value of 0 (zero). See section 5.2 of [RFC2025] for an

explanation.

LIPKEY uses SPKM-3 to create a secure channel in which to pass a user

name and password from the client to the user. Once the user name

and password have been accepted by the server, calls to the LIPKEY

context are redirected to the SPKM-3 context. See [RFC2847] for more

details.

3.2.1.3. SPKM-3 as a security triple

The SPKM-3 GSS-API mechanism as described in [RFC2847] MUST be

implemented and provide the following security triples. The

definition of the columns matches the previous subsection "Kerberos

V5 as security triple".

1 2 3 4 5

-----------------------------------------------------------------------

390009 spkm3 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_none

390010 spkm3i 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_integrity

390011 spkm3p 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_privacy

For a discussion as to why the mechanism algorithm is listed as

"negotiated", see the previous section "LIPKEY as a security triple."

Because SPKM-3 negotiates the algorithms, subsequent calls to SPKM-

3's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality of

protection value of 0 (zero). See section 5.2 of [RFC2025] for an

explanation.

Even though LIPKEY is layered over SPKM-3, SPKM-3 is specified as a

mandatory set of triples to handle the situations where the initiator

(the client) is anonymous or where the initiator has its own

certificate. If the initiator is anonymous, there will not be a user

name and password to send to the target (the server). If the

initiator has its own certificate, then using passwords is

superfluous.

3.3. Security Negotiation

With the NFS version 4 server potentially offering multiple security

mechanisms, the client needs a method to determine or negotiate which

mechanism is to be used for its communication with the server. The

NFS server may have multiple points within its file system name space

that are available for use by NFS clients. In turn the NFS server

may be configured such that each of these entry points may have

different or multiple security mechanisms in use.

The security negotiation between client and server must be done with

a secure channel to eliminate the possibility of a third party

intercepting the negotiation sequence and forcing the client and

server to choose a lower level of security than required or desired.

3.3.1. Security Error

Based on the assumption that each NFS version 4 client and server

must support a minimum set of security (i.e. LIPKEY, SPKM-3, and

Kerberos-V5 all under RPCSEC_GSS), the NFS client will start its

communication with the server with one of the minimal security

triples. During communication with the server, the client may

receive an NFS error of NFS4ERR_WRONGSEC. This error allows the

server to notify the client that the security triple currently being

used is not appropriate for access to the server's file system

resources. The client is then responsible for determining what

security triples are available at the server and choose one which is

appropriate for the client.

3.3.2. SECINFO

The new SECINFO operation will allow the client to determine, on a

per filehandle basis, what security triple is to be used for server

access. In general, the client will not have to use the SECINFO

procedure except during initial communication with the server or when

the client crosses policy boundaries at the server. It is possible

that the server's policies change during the client's interaction

therefore forcing the client to negotiate a new security triple.

3.4. Callback RPC Authentication

The callback RPC (described later) must mutually authenticate the NFS

server to the principal that acquired the clientid (also described

later), using the same security flavor the original SETCLIENTID

operation used. Because LIPKEY is layered over SPKM-3, it is

permissible for the server to use SPKM-3 and not LIPKEY for the

callback even if the client used LIPKEY for SETCLIENTID.

For AUTH_NONE, there are no principals, so this is a non-issue.

For AUTH_SYS, the server simply uses the AUTH_SYS credential that the

user used when it set up the delegation.

For AUTH_DH, one commonly used convention is that the server uses the

credential corresponding to this AUTH_DH principal:

unix.host@domain

where host and domain are variables corresponding to the name of

server host and directory services domain in which it lives such as a

Network Information System domain or a DNS domain.

Regardless of what security mechanism under RPCSEC_GSS is being used,

the NFS server, MUST identify itself in GSS-API via a

GSS_C_NT_HOSTBASED_SERVICE name type. GSS_C_NT_HOSTBASED_SERVICE

names are of the form:

service@hostname

For NFS, the "service" element is

nfs

Implementations of security mechanisms will convert nfs@hostname to

various different forms. For Kerberos V5 and LIPKEY, the following

form is RECOMMENDED:

nfs/hostname

For Kerberos V5, nfs/hostname would be a server principal in the

Kerberos Key Distribution Center database. For LIPKEY, this would be

the username passed to the target (the NFS version 4 client that

receives the callback).

It should be noted that LIPKEY may not work for callbacks, since the

LIPKEY client uses a user id/password. If the NFS client receiving

the callback can authenticate the NFS server's user name/password

pair, and if the user that the NFS server is authenticating to has a

public key certificate, then it works.

In situations where NFS client uses LIPKEY and uses a per-host

principal for the SETCLIENTID operation, instead of using LIPKEY for

SETCLIENTID, it is RECOMMENDED that SPKM-3 with mutual authentication

be used. This effectively means that the client will use a

certificate to authenticate and identify the initiator to the target

on the NFS server. Using SPKM-3 and not LIPKEY has the following

advantages:

o When the server does a callback, it must authenticate to the

principal used in the SETCLIENTID. Even if LIPKEY is used,

because LIPKEY is layered over SPKM-3, the NFS client will need to

have a certificate that corresponds to the principal used in the

SETCLIENTID operation. From an administrative perspective, having

a user name, password, and certificate for both the client and

server is redundant.

o LIPKEY was intended to minimize additional infrastructure

requirements beyond a certificate for the target, and the

expectation is that existing password infrastructure can be

leveraged for the initiator. In some environments, a per-host

password does not exist yet. If certificates are used for any

per-host principals, then additional password infrastructure is

not needed.

o In cases when a host is both an NFS client and server, it can

share the same per-host certificate.

4. Filehandles

The filehandle in the NFS protocol is a per server unique identifier

for a file system object. The contents of the filehandle are opaque

to the client. Therefore, the server is responsible for translating

the filehandle to an internal representation of the file system

object. Since the filehandle is the client's reference to an object

and the client may cache this reference, the server SHOULD not reuse

a filehandle for another file system object. If the server needs to

reuse a filehandle value, the time elapsed before reuse SHOULD be

large enough such that it is unlikely the client has a cached copy of

the reused filehandle value. Note that a client may cache a

filehandle for a very long time. For example, a client may cache NFS

data to local storage as a method to expand its effective cache size

and as a means to survive client restarts. Therefore, the lifetime

of a cached filehandle may be extended.

4.1. Obtaining the First Filehandle

The operations of the NFS protocol are defined in terms of one or

more filehandles. Therefore, the client needs a filehandle to

initiate communication with the server. With the NFS version 2

protocol [RFC1094] and the NFS version 3 protocol [RFC1813], there

exists an ancillary protocol to obtain this first filehandle. The

MOUNT protocol, RPC program number 100005, provides the mechanism of

translating a string based file system path name to a filehandle

which can then be used by the NFS protocols.

The MOUNT protocol has deficiencies in the area of security and use

via firewalls. This is one reason that the use of the public

filehandle was introduced in [RFC2054] and [RFC2055]. With the use

of the public filehandle in combination with the LOOKUP procedure in

the NFS version 2 and 3 protocols, it has been demonstrated that the

MOUNT protocol is unnecessary for viable interaction between NFS

client and server.

Therefore, the NFS version 4 protocol will not use an ancillary

protocol for translation from string based path names to a

filehandle. Two special filehandles will be used as starting points

for the NFS client.

4.1.1. Root Filehandle

The first of the special filehandles is the ROOT filehandle. The

ROOT filehandle is the "conceptual" root of the file system name

space at the NFS server. The client uses or starts with the ROOT

filehandle by employing the PUTROOTFH operation. The PUTROOTFH

operation instructs the server to set the "current" filehandle to the

ROOT of the server's file tree. Once this PUTROOTFH operation is

used, the client can then traverse the entirety of the server's file

tree with the LOOKUP procedure. A complete discussion of the server

name space is in the section "NFS Server Name Space".

4.1.2. Public Filehandle

The second special filehandle is the PUBLIC filehandle. Unlike the

ROOT filehandle, the PUBLIC filehandle may be bound or represent an

arbitrary file system object at the server. The server is

responsible for this binding. It may be that the PUBLIC filehandle

and the ROOT filehandle refer to the same file system object.

However, it is up to the administrative software at the server and

the policies of the server administrator to define the binding of the

PUBLIC filehandle and server file system object. The client may not

make any assumptions about this binding.

4.2. Filehandle Types

In the NFS version 2 and 3 protocols, there was one type of

filehandle with a single set of semantics. The NFS version 4

protocol introduces a new type of filehandle in an attempt to

accommodate certain server environments. The first type of

filehandle is 'persistent'. The semantics of a persistent filehandle

are the same as the filehandles of the NFS version 2 and 3 protocols.

The second or new type of filehandle is the "volatile" filehandle.

The volatile filehandle type is being introduced to address server

functionality or implementation issues which make correct

implementation of a persistent filehandle infeasible. Some server

environments do not provide a file system level invariant that can be

used to construct a persistent filehandle. The underlying server

file system may not provide the invariant or the server's file system

programming interfaces may not provide access to the needed

invariant. Volatile filehandles may ease the implementation of

server functionality such as hierarchical storage management or file

system reorganization or migration. However, the volatile filehandle

increases the implementation burden for the client. However this

increased burden is deemed acceptable based on the overall gains

achieved by the protocol.

Since the client will need to handle persistent and volatile

filehandle differently, a file attribute is defined which may be used

by the client to determine the filehandle types being returned by the

server.

4.2.1. General Properties of a Filehandle

The filehandle contains all the information the server needs to

distinguish an individual file. To the client, the filehandle is

opaque. The client stores filehandles for use in a later request and

can compare two filehandles from the same server for equality by

doing a byte-by-byte comparison. However, the client MUST NOT

otherwise interpret the contents of filehandles. If two filehandles

from the same server are equal, they MUST refer to the same file. If

they are not equal, the client may use information provided by the

server, in the form of file attributes, to determine whether they

denote the same files or different files. The client would do this

as necessary for client side caching. Servers SHOULD try to maintain

a one-to-one correspondence between filehandles and files but this is

not required. Clients MUST use filehandle comparisons only to

improve performance, not for correct behavior. All clients need to

be prepared for situations in which it cannot be determined whether

two filehandles denote the same object and in such cases, avoid

making invalid assumptions which might cause incorrect behavior.

Further discussion of filehandle and attribute comparison in the

context of data caching is presented in the section "Data Caching and

File Identity".

As an example, in the case that two different path names when

traversed at the server terminate at the same file system object, the

server SHOULD return the same filehandle for each path. This can

occur if a hard link is used to create two file names which refer to

the same underlying file object and associated data. For example, if

paths /a/b/c and /a/d/c refer to the same file, the server SHOULD

return the same filehandle for both path names traversals.

4.2.2. Persistent Filehandle

A persistent filehandle is defined as having a fixed value for the

lifetime of the file system object to which it refers. Once the

server creates the filehandle for a file system object, the server

MUST accept the same filehandle for the object for the lifetime of

the object. If the server restarts or reboots the NFS server must

honor the same filehandle value as it did in the server's previous

instantiation. Similarly, if the file system is migrated, the new

NFS server must honor the same file handle as the old NFS server.

The persistent filehandle will be become stale or invalid when the

file system object is removed. When the server is presented with a

persistent filehandle that refers to a deleted object, it MUST return

an error of NFS4ERR_STALE. A filehandle may become stale when the

file system containing the object is no longer available. The file

system may become unavailable if it exists on removable media and the

media is no longer available at the server or the file system in

whole has been destroyed or the file system has simply been removed

from the server's name space (i.e. unmounted in a Unix environment).

4.2.3. Volatile Filehandle

A volatile filehandle does not share the same longevity

characteristics of a persistent filehandle. The server may determine

that a volatile filehandle is no longer valid at many different

points in time. If the server can definitively determine that a

volatile filehandle refers to an object that has been removed, the

server should return NFS4ERR_STALE to the client (as is the case for

persistent filehandles). In all other cases where the server

determines that a volatile filehandle can no longer be used, it

should return an error of NFS4ERR_FHEXPIRED.

The mandatory attribute "fh_expire_type" is used by the client to

determine what type of filehandle the server is providing for a

particular file system. This attribute is a bitmask with the

following values:

FH4_PERSISTENT

The value of FH4_PERSISTENT is used to indicate a persistent

filehandle, which is valid until the object is removed from the

file system. The server will not return NFS4ERR_FHEXPIRED for

this filehandle. FH4_PERSISTENT is defined as a value in which

none of the bits specified below are set.

FH4_NOEXPIRE_WITH_OPEN

The filehandle will not expire while client has the file open.

If this bit is set, then the values FH4_VOLATILE_ANY or

FH4_VOL_RENAME do not impact expiration while the file is open.

Once the file is closed or if the FH4_NOEXPIRE_WITH_OPEN bit is

false, the rest of the volatile related bits apply.

FH4_VOLATILE_ANY

The filehandle may expire at any time and will expire during

system migration and rename.

FH4_VOL_MIGRATION

The filehandle will expire during file system migration. May

only be set if FH4_VOLATILE_ANY is not set.

FH4_VOL_RENAME

The filehandle may expire due to a rename. This includes a

rename by the requesting client or a rename by another client.

May only be set if FH4_VOLATILE_ANY is not set.

Servers which provide volatile filehandles should deny a RENAME or

REMOVE that would affect an OPEN file or any of the components

leading to the OPEN file. In addition, the server should deny all

RENAME or REMOVE requests during the grace or lease period upon

server restart.

The reader may be wondering why there are three FH4_VOL* bits and why

FH4_VOLATILE_ANY is exclusive of FH4_VOL_MIGRATION and

FH4_VOL_RENAME. If the a filehandle is normally persistent but

cannot persist across a file set migration, then the presence of the

FH4_VOL_MIGRATION or FH4_VOL_RENAME tells the client that it can

treat the file handle as persistent for purposes of maintaining a

file name to file handle cache, except for the specific event

described by the bit. However, FH4_VOLATILE_ANY tells the client

that it should not maintain such a cache for unopened files. A

server MUST not present FH4_VOLATILE_ANY with FH4_VOL_MIGRATION or

FH4_VOL_RENAME as this will lead to confusion. FH4_VOLATILE_ANY

implies that the file handle will expire upon migration or rename, in

addition to other events.

4.2.4. One Method of Constructing a Volatile Filehandle

As mentioned, in some instances a filehandle is stale (no longer

valid; perhaps because the file was removed from the server) or it is

expired (the underlying file is valid but since the filehandle is

volatile, it may have expired). Thus the server needs to be able to

return NFS4ERR_STALE in the former case and NFS4ERR_FHEXPIRED in the

latter case. This can be done by careful construction of the volatile

filehandle. One possible implementation follows.

A volatile filehandle, while opaque to the client could contain:

[volatile bit = 1 server boot time slot generation number]

o slot is an index in the server volatile filehandle table

o generation number is the generation number for the table

entry/slot

If the server boot time is less than the current server boot time,

return NFS4ERR_FHEXPIRED. If slot is out of range, return

NFS4ERR_BADHANDLE. If the generation number does not match, return

NFS4ERR_FHEXPIRED.

When the server reboots, the table is gone (it is volatile).

If volatile bit is 0, then it is a persistent filehandle with a

different structure following it.

4.3. Client Recovery from Filehandle Expiration

If possible, the client SHOULD recover from the receipt of an

NFS4ERR_FHEXPIRED error. The client must take on additional

responsibility so that it may prepare itself to recover from the

expiration of a volatile filehandle. If the server returns

persistent filehandles, the client does not need these additional

steps.

For volatile filehandles, most commonly the client will need to store

the component names leading up to and including the file system

object in question. With these names, the client should be able to

recover by finding a filehandle in the name space that is still

available or by starting at the root of the server's file system name

space.

If the expired filehandle refers to an object that has been removed

from the file system, obviously the client will not be able to

recover from the expired filehandle.

It is also possible that the expired filehandle refers to a file that

has been renamed. If the file was renamed by another client, again

it is possible that the original client will not be able to recover.

However, in the case that the client itself is renaming the file and

the file is open, it is possible that the client may be able to

recover. The client can determine the new path name based on the

processing of the rename request. The client can then regenerate the

new filehandle based on the new path name. The client could also use

the compound operation mechanism to construct a set of operations

like:

RENAME A B

LOOKUP B

GETFH

5. File Attributes

To meet the requirements of extensibility and increased

interoperability with non-Unix platforms, attributes must be handled

in a flexible manner. The NFS Version 3 fattr3 structure contains a

fixed list of attributes that not all clients and servers are able to

support or care about. The fattr3 structure can not be extended as

new needs arise and it provides no way to indicate non-support. With

the NFS Version 4 protocol, the client will be able to ask what

attributes the server supports and will be able to request only those

attributes in which it is interested.

To this end, attributes will be divided into three groups: mandatory,

recommended, and named. Both mandatory and recommended attributes

are supported in the NFS version 4 protocol by a specific and well-

defined encoding and are identified by number. They are requested by

setting a bit in the bit vector sent in the GETATTR request; the

server response includes a bit vector to list what attributes were

returned in the response. New mandatory or recommended attributes

may be added to the NFS protocol between major revisions by

publishing a standards-track RFCwhich allocates a new attribute

number value and defines the encoding for the attribute. See the

section "Minor Versioning" for further discussion.

Named attributes are accessed by the new OPENATTR operation, which

accesses a hidden directory of attributes associated with a file

system object. OPENATTR takes a filehandle for the object and

returns the filehandle for the attribute hierarchy. The filehandle

for the named attributes is a directory object accessible by LOOKUP

or READDIR and contains files whose names represent the named

attributes and whose data bytes are the value of the attribute. For

example:

LOOKUP "foo" ; look up file

GETATTR attrbits

OPENATTR ; access foo's named attributes

LOOKUP "x11icon" ; look up specific attribute

READ 0,4096 ; read stream of bytes

Named attributes are intended for data needed by applications rather

than by an NFS client implementation. NFS implementors are strongly

encouraged to define their new attributes as recommended attributes

by bringing them to the IETF standards-track process.

The set of attributes which are classified as mandatory is

deliberately small since servers must do whatever it takes to support

them. The recommended attributes may be unsupported; though a server

should support as many as it can. Attributes are deemed mandatory if

the data is both needed by a large number of clients and is not

otherwise reasonably computable by the client when support is not

provided on the server.

5.1. Mandatory Attributes

These MUST be supported by every NFS Version 4 client and server in

order to ensure a minimum level of interoperability. The server must

store and return these attributes and the client must be able to

function with an attribute set limited to these attributes. With

just the mandatory attributes some client functionality may be

impaired or limited in some ways. A client may ask for any of these

attributes to be returned by setting a bit in the GETATTR request and

the server must return their value.

5.2. Recommended Attributes

These attributes are understood well enough to warrant support in the

NFS Version 4 protocol. However, they may not be supported on all

clients and servers. A client may ask for any of these attributes to

be returned by setting a bit in the GETATTR request but must handle

the case where the server does not return them. A client may ask for

the set of attributes the server supports and should not request

attributes the server does not support. A server should be tolerant

of requests for unsupported attributes and simply not return them

rather than considering the request an error. It is expected that

servers will support all attributes they comfortably can and only

fail to support attributes which are difficult to support in their

operating environments. A server should provide attributes whenever

they don't have to "tell lies" to the client. For example, a file

modification time should be either an accurate time or should not be

supported by the server. This will not always be comfortable to

clients but it seems that the client has a better ability to

fabricate or construct an attribute or do without the attribute.

5.3. Named Attributes

These attributes are not supported by direct encoding in the NFS

Version 4 protocol but are accessed by string names rather than

numbers and correspond to an uninterpreted stream of bytes which are

stored with the file system object. The name space for these

attributes may be accessed by using the OPENATTR operation. The

OPENATTR operation returns a filehandle for a virtual "attribute

directory" and further perusal of the name space may be done using

READDIR and LOOKUP operations on this filehandle. Named attributes

may then be examined or changed by normal READ and WRITE and CREATE

operations on the filehandles returned from READDIR and LOOKUP.

Named attributes may have attributes.

It is recommended that servers support arbitrary named attributes. A

client should not depend on the ability to store any named attributes

in the server's file system. If a server does support named

attributes, a client which is also able to handle them should be able

to copy a file's data and meta-data with complete transparency from

one location to another; this would imply that names allowed for

regular directory entries are valid for named attribute names as

well.

Names of attributes will not be controlled by this document or other

IETF standards track documents. See the section "IANA

Considerations" for further discussion.

5.4. Mandatory Attributes - Definitions

Name # DataType Access Description

___________________________________________________________________

supp_attr 0 bitmap READ The bit vector which

would retrieve all

mandatory and

recommended attributes

that are supported for

this object.

type 1 nfs4_ftype READ The type of the object

(file, directory,

symlink)

fh_expire_type 2 uint32 READ Server uses this to

specify filehandle

expiration behavior to

the client. See the

section "Filehandles"

for additional

description.

change 3 uint64 READ A value created by the

server that the client

can use to determine

if file data,

directory contents or

attributes of the

object have been

modified. The server

may return the

object's time_modify

attribute for this

attribute's value but

only if the file

system object can not

be updated more

frequently than the

resolution of

time_modify.

size 4 uint64 R/W The size of the object

in bytes.

link_support 5 boolean READ Does the object's file

system supports hard

links?

symlink_support 6 boolean READ Does the object's file

system supports

symbolic links?

named_attr 7 boolean READ Does this object have

named attributes?

fsid 8 fsid4 READ Unique file system

identifier for the

file system holding

this object. fsid

contains major and

minor components each

of which are uint64.

unique_handles 9 boolean READ Are two distinct

filehandles guaranteed

to refer to two

different file system

objects?

lease_time 10 nfs_lease4 READ Duration of leases at

server in seconds.

rdattr_error 11 enum READ Error returned from

getattr during

readdir.

5.5. Recommended Attributes - Definitions

Name # Data Type Access Description

_____________________________________________________________________

ACL 12 nfsace4<> R/W The access control

list for the object.

aclsupport 13 uint32 READ Indicates what types

of ACLs are supported

on the current file

system.

archive 14 boolean R/W Whether or not this

file has been

archived since the

time of last

modification

(deprecated in favor

of time_backup).

cansettime 15 boolean READ Is the server able to

change the times for

a file system object

as specified in a

SETATTR operation?

case_insensitive 16 boolean READ Are filename

comparisons on this

file system case

insensitive?

case_preserving 17 boolean READ Is filename case on

this file system

preserved?

chown_restricted 18 boolean READ If TRUE, the server

will reject any

request to change

either the owner or

the group associated

with a file if the

caller is not a

privileged user (for

example, "root" in

Unix operating

environments or in NT

the "Take Ownership"

privilege)

filehandle 19 nfs4_fh READ The filehandle of

this object

(primarily for

readdir requests).

fileid 20 uint64 READ A number uniquely

identifying the file

within the file

system.

files_avail 21 uint64 READ File slots available

to this user on the

file system

containing this

object - this should

be the smallest

relevant limit.

files_free 22 uint64 READ Free file slots on

the file system

containing this

object - this should

be the smallest

relevant limit.

files_total 23 uint64 READ Total file slots on

the file system

containing this

object.

fs_locations 24 fs_locations READ Locations where this

file system may be

found. If the server

returns NFS4ERR_MOVED

as an error, this

attribute must be

supported.

hidden 25 boolean R/W Is file considered

hidden with respect

to the WIN32 API?

homogeneous 26 boolean READ Whether or not this

object's file system

is homogeneous, i.e.

are per file system

attributes the same

for all file system's

objects.

maxfilesize 27 uint64 READ Maximum supported

file size for the

file system of this

object.

maxlink 28 uint32 READ Maximum number of

links for this

object.

maxname 29 uint32 READ Maximum filename size

supported for this

object.

maxread 30 uint64 READ Maximum read size

supported for this

object.

maxwrite 31 uint64 READ Maximum write size

supported for this

object. This

attribute SHOULD be

supported if the file

is writable. Lack of

this attribute can

lead to the client

either wasting

bandwidth or not

receiving the best

performance.

mimetype 32 utf8<> R/W MIME body

type/subtype of this

object.

mode 33 mode4 R/W Unix-style permission

bits for this object

(deprecated in favor

of ACLs)

no_trunc 34 boolean READ If a name longer than

name_max is used,

will an error be

returned or will the

name be truncated?

numlinks 35 uint32 READ Number of hard links

to this object.

owner 36 utf8<> R/W The string name of

the owner of this

object.

owner_group 37 utf8<> R/W The string name of

the group ownership

of this object.

quota_avail_hard 38 uint64 READ For definition see

"Quota Attributes"

section below.

quota_avail_soft 39 uint64 READ For definition see

"Quota Attributes"

section below.

quota_used 40 uint64 READ For definition see

"Quota Attributes"

section below.

rawdev 41 specdata4 READ Raw device

identifier. Unix

device major/minor

node information.

space_avail 42 uint64 READ Disk space in bytes

available to this

user on the file

system containing

this object - this

should be the

smallest relevant

limit.

space_free 43 uint64 READ Free disk space in

bytes on the file

system containing

this object - this

should be the

smallest relevant

limit.

space_total 44 uint64 READ Total disk space in

bytes on the file

system containing

this object.

space_used 45 uint64 READ Number of file system

bytes allocated to

this object.

system 46 boolean R/W Is this file a system

file with respect to

the WIN32 API?

time_access 47 nfstime4 READ The time of last

access to the object.

time_access_set 48 settime4 WRITE Set the time of last

access to the object.

SETATTR use only.

time_backup 49 nfstime4 R/W The time of last

backup of the object.

time_create 50 nfstime4 R/W The time of creation

of the object. This

attribute does not

have any relation to

the traditional Unix

file attribute

"ctime" or "change

time".

time_delta 51 nfstime4 READ Smallest useful

server time

granularity.

time_metadata 52 nfstime4 R/W The time of last

meta-data

modification of the

object.

time_modify 53 nfstime4 READ The time of last

modification to the

object.

time_modify_set 54 settime4 WRITE Set the time of last

modification to the

object. SETATTR use

only.

5.6. Interpreting owner and owner_group

The recommended attributes "owner" and "owner_group" are represented

in terms of a UTF-8 string. To avoid a representation that is tied

to a particular underlying implementation at the client or server,

the use of the UTF-8 string has been chosen. Note that section 6.1

of [RFC2624] provides additional rationale. It is expected that the

client and server will have their own local representation of owner

and owner_group that is used for local storage or presentation to the

end user. Therefore, it is expected that when these attributes are

transferred between the client and server that the local

representation is translated to a syntax of the form

"user@dns_domain". This will allow for a client and server that do

not use the same local representation the ability to translate to a

common syntax that can be interpreted by both.

The translation is not specified as part of the protocol. This

allows various solutions to be employed. For example, a local

translation table may be consulted that maps between a numeric id to

the user@dns_domain syntax. A name service may also be used to

accomplish the translation. The "dns_domain" portion of the owner

string is meant to be a DNS domain name. For example, user@ietf.org.

In the case where there is no translation available to the client or

server, the attribute value must be constructed without the "@".

Therefore, the absence of the @ from the owner or owner_group

attribute signifies that no translation was available and the

receiver of the attribute should not place any special meaning with

the attribute value. Even though the attribute value can not be

translated, it may still be useful. In the case of a client, the

attribute string may be used for local display of ownership.

5.7. Character Case Attributes

With respect to the case_insensitive and case_preserving attributes,

each UCS-4 character (which UTF-8 encodes) has a "long descriptive

name" [RFC1345] which may or may not included the word "CAPITAL" or

"SMALL". The presence of SMALL or CAPITAL allows an NFS server to

implement unambiguous and efficient table driven mappings for case

insensitive comparisons, and non-case-preserving storage. For

general character handling and internationalization issues, see the

section "Internationalization".

5.8. Quota Attributes

For the attributes related to file system quotas, the following

definitions apply:

quota_avail_soft

The value in bytes which represents the amount of additional

disk space that can be allocated to this file or directory

before the user may reasonably be warned. It is understood

that this space may be consumed by allocations to other files

or directories though there is a rule as to which other files

or directories.

quota_avail_hard

The value in bytes which represent the amount of additional

disk space beyond the current allocation that can be allocated

to this file or directory before further allocations will be

refused. It is understood that this space may be consumed by

allocations to other files or directories.

quota_used

The value in bytes which represent the amount of disc space

used by this file or directory and possibly a number of other

similar files or directories, where the set of "similar" meets

at least the criterion that allocating space to any file or

directory in the set will reduce the "quota_avail_hard" of

every other file or directory in the set.

Note that there may be a number of distinct but overlapping

sets of files or directories for which a quota_used value is

maintained. E.g. "all files with a given owner", "all files

with a given group owner". etc.

The server is at liberty to choose any of those sets but should

do so in a repeatable way. The rule may be configured per-

filesystem or may be "choose the set with the smallest quota".

5.9. Access Control Lists

The NFS ACL attribute is an array of access control entries (ACE).

There are various access control entry types. The server is able to

communicate which ACE types are supported by returning the

appropriate value within the aclsupport attribute. The types of ACEs

are defined as follows:

Type Description

_____________________________________________________

ALLOW Explicitly grants the access defined in

acemask4 to the file or directory.

DENY Explicitly denies the access defined in

acemask4 to the file or directory.

AUDIT LOG (system dependent) any access

attempt to a file or directory which

uses any of the access methods specified

in acemask4.

ALARM Generate a system ALARM (system

dependent) when any access attempt is

made to a file or directory for the

access methods specified in acemask4.

The NFS ACE attribute is defined as follows:

typedef uint32_t acetype4;

typedef uint32_t aceflag4;

typedef uint32_t acemask4;

struct nfsace4 {

acetype4 type;

aceflag4 flag;

acemask4 access_mask;

utf8string who;

};

To determine if an ACCESS or OPEN request succeeds each nfsace4 entry

is processed in order by the server. Only ACEs which have a "who"

that matches the requester are considered. Each ACE is processed

until all of the bits of the requester's access have been ALLOWED.

Once a bit (see below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it

is no longer considered in the processing of later ACEs. If an

ACCESS_DENIED_ACE is encountered where the requester's mode still has

unALLOWED bits in common with the "access_mask" of the ACE, the

request is denied.

The bitmask constants used to represent the above definitions within

the aclsupport attribute are as follows:

const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;

const ACL4_SUPPORT_DENY_ACL = 0x00000002;

const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;

const ACL4_SUPPORT_ALARM_ACL = 0x00000008;

5.9.1. ACE type

The semantics of the "type" field follow the descriptions provided

above.

The bitmask constants used for the type field are as follows:

const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;

const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;

const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;

const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;

5.9.2. ACE flag

The "flag" field contains values based on the following descriptions.

ACE4_FILE_INHERIT_ACE

Can be placed on a directory and indicates that this ACE should be

added to each new non-directory file created.

ACE4_DIRECTORY_INHERIT_ACE

Can be placed on a directory and indicates that this ACE should be

added to each new directory created.

ACE4_INHERIT_ONLY_ACE

Can be placed on a directory but does not apply to the directory,

only to newly created files/directories as specified by the above two

flags.

ACE4_NO_PROPAGATE_INHERIT_ACE

Can be placed on a directory. Normally when a new directory is

created and an ACE exists on the parent directory which is marked

ACL4_DIRECTORY_INHERIT_ACE, two ACEs are placed on the new directory.

One for the directory itself and one which is an inheritable ACE for

newly created directories. This flag tells the server to not place

an ACE on the newly created directory which is inheritable by

subdirectories of the created directory.

ACE4_SUCCESSFUL_ACCESS_ACE_FLAG

ACL4_FAILED_ACCESS_ACE_FLAG

Both indicate for AUDIT and ALARM which state to log the event. On

every ACCESS or OPEN call which occurs on a file or directory which

has an ACL that is of type ACE4_SYSTEM_AUDIT_ACE_TYPE or

ACE4_SYSTEM_ALARM_ACE_TYPE, the attempted access is compared to the

ace4mask of these ACLs. If the access is a subset of ace4mask and the

identifier match, an AUDIT trail or an ALARM is generated. By

default this happens regardless of the success or failure of the

ACCESS or OPEN call.

The flag ACE4_SUCCESSFUL_ACCESS_ACE_FLAG only produces the AUDIT or

ALARM if the ACCESS or OPEN call is successful. The

ACE4_FAILED_ACCESS_ACE_FLAG causes the ALARM or AUDIT if the ACCESS

or OPEN call fails.

ACE4_IDENTIFIER_GROUP

Indicates that the "who" refers to a GROUP as defined under Unix.

The bitmask constants used for the flag field are as follows:

const ACE4_FILE_INHERIT_ACE = 0x00000001;

const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002;

const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004;

const ACE4_INHERIT_ONLY_ACE = 0x00000008;

const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010;

const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020;

const ACE4_IDENTIFIER_GROUP = 0x00000040;

5.9.3. ACE Access Mask

The access_mask field contains values based on the following:

Access Description

_______________________________________________________________

READ_DATA Permission to read the data of the file

LIST_DIRECTORY Permission to list the contents of a

directory

WRITE_DATA Permission to modify the file's data

ADD_FILE Permission to add a new file to a

directory

APPEND_DATA Permission to append data to a file

ADD_SUBDIRECTORY Permission to create a subdirectory to a

directory

READ_NAMED_ATTRS Permission to read the named attributes

of a file

WRITE_NAMED_ATTRS Permission to write the named attributes

of a file

EXECUTE Permission to execute a file

DELETE_CHILD Permission to delete a file or directory

within a directory

READ_ATTRIBUTES The ability to read basic attributes

(non-acls) of a file

WRITE_ATTRIBUTES Permission to change basic attributes

(non-acls) of a file

DELETE Permission to Delete the file

READ_ACL Permission to Read the ACL

WRITE_ACL Permission to Write the ACL

WRITE_OWNER Permission to change the owner

SYNCHRONIZE Permission to access file locally at the

server with synchronous reads and writes

The bitmask constants used for the access mask field are as follows:

const ACE4_READ_DATA = 0x00000001;

const ACE4_LIST_DIRECTORY = 0x00000001;

const ACE4_WRITE_DATA = 0x00000002;

const ACE4_ADD_FILE = 0x00000002;

const ACE4_APPEND_DATA = 0x00000004;

const ACE4_ADD_SUBDIRECTORY = 0x00000004;

const ACE4_READ_NAMED_ATTRS = 0x00000008;

const ACE4_WRITE_NAMED_ATTRS = 0x00000010;

const ACE4_EXECUTE = 0x00000020;

const ACE4_DELETE_CHILD = 0x00000040;

const ACE4_READ_ATTRIBUTES = 0x00000080;

const ACE4_WRITE_ATTRIBUTES = 0x00000100;

const ACE4_DELETE = 0x00010000;

const ACE4_READ_ACL = 0x00020000;

const ACE4_WRITE_ACL = 0x00040000;

const ACE4_WRITE_OWNER = 0x00080000;

const ACE4_SYNCHRONIZE = 0x00100000;

5.9.4. ACE who

There are several special identifiers ("who") which need to be

understood universally. Some of these identifiers cannot be

understood when an NFS client accesses the server, but have meaning

when a local process accesses the file. The ability to display and

modify these permissions is permitted over NFS.

Who Description

_______________________________________________________________

"OWNER" The owner of the file.

"GROUP" The group associated with the file.

"EVERYONE" The world.

"INTERACTIVE" Accessed from an interactive terminal.

"NETWORK" Accessed via the network.

"DIALUP" Accessed as a dialup user to the server.

"BATCH" Accessed from a batch job.

"ANONYMOUS" Accessed without any authentication.

"AUTHENTICATED" Any authenticated user (opposite of

ANONYMOUS)

"SERVICE" Access from a system service.

To avoid conflict, these special identifiers are distinguish by an

appended "@" and should appear in the form "xxxx@" (note: no domain

name after the "@"). For example: ANONYMOUS@.

6. File System Migration and Replication

With the use of the recommended attribute "fs_locations", the NFS

version 4 server has a method of providing file system migration or

replication services. For the purposes of migration and replication,

a file system will be defined as all files that share a given fsid

(both major and minor values are the same).

The fs_locations attribute provides a list of file system locations.

These locations are specified by providing the server name (either

DNS domain or IP address) and the path name representing the root of

the file system. Depending on the type of service being provided,

the list will provide a new location or a set of alternate locations

for the file system. The client will use this information to

redirect its requests to the new server.

6.1. Replication

It is expected that file system replication will be used in the case

of read-only data. Typically, the file system will be replicated on

two or more servers. The fs_locations attribute will provide the

list of these locations to the client. On first access of the file

system, the client should obtain the value of the fs_locations

attribute. If, in the future, the client finds the server

unresponsive, the client may attempt to use another server specified

by fs_locations.

If applicable, the client must take the appropriate steps to recover

valid filehandles from the new server. This is described in more

detail in the following sections.

6.2. Migration

File system migration is used to move a file system from one server

to another. Migration is typically used for a file system that is

writable and has a single copy. The expected use of migration is for

load balancing or general resource reallocation. The protocol does

not specify how the file system will be moved between servers. This

server-to-server transfer mechanism is left to the server

implementor. However, the method used to communicate the migration

event between client and server is specified here.

Once the servers participating in the migration have completed the

move of the file system, the error NFS4ERR_MOVED will be returned for

subsequent requests received by the original server. The

NFS4ERR_MOVED error is returned for all operations except GETATTR.

Upon receiving the NFS4ERR_MOVED error, the client will obtain the

value of the fs_locations attribute. The client will then use the

contents of the attribute to redirect its requests to the specified

server. To facilitate the use of GETATTR, operations such as PUTFH

must also be accepted by the server for the migrated file system's

filehandles. Note that if the server returns NFS4ERR_MOVED, the

server MUST support the fs_locations attribute.

If the client requests more attributes than just fs_locations, the

server may return fs_locations only. This is to be expected since

the server has migrated the file system and may not have a method of

obtaining additional attribute data.

The server implementor needs to be careful in developing a migration

solution. The server must consider all of the state information

clients may have outstanding at the server. This includes but is not

limited to locking/share state, delegation state, and asynchronous

file writes which are represented by WRITE and COMMIT verifiers. The

server should strive to minimize the impact on its clients during and

after the migration process.

6.3. Interpretation of the fs_locations Attribute

The fs_location attribute is structured in the following way:

struct fs_location {

utf8string server<>;

pathname4 rootpath;

};

struct fs_locations {

pathname4 fs_root;

fs_location locations<>;

};

The fs_location struct is used to represent the location of a file

system by providing a server name and the path to the root of the

file system. For a multi-homed server or a set of servers that use

the same rootpath, an array of server names may be provided. An

entry in the server array is an UTF8 string and represents one of a

traditional DNS host name, IPv4 address, or IPv6 address. It is not

a requirement that all servers that share the same rootpath be listed

in one fs_location struct. The array of server names is provided for

convenience. Servers that share the same rootpath may also be listed

in separate fs_location entries in the fs_locations attribute.

The fs_locations struct and attribute then contains an array of

locations. Since the name space of each server may be constructed

differently, the "fs_root" field is provided. The path represented

by fs_root represents the location of the file system in the server's

name space. Therefore, the fs_root path is only associated with the

server from which the fs_locations attribute was obtained. The

fs_root path is meant to aid the client in locating the file system

at the various servers listed.

As an example, there is a replicated file system located at two

servers (servA and servB). At servA the file system is located at

path "/a/b/c". At servB the file system is located at path "/x/y/z".

In this example the client accesses the file system first at servA

with a multi-component lookup path of "/a/b/c/d". Since the client

used a multi-component lookup to obtain the filehandle at "/a/b/c/d",

it is unaware that the file system's root is located in servA's name

space at "/a/b/c". When the client switches to servB, it will need

to determine that the directory it first referenced at servA is now

represented by the path "/x/y/z/d" on servB. To facilitate this, the

fs_locations attribute provided by servA would have a fs_root value

of "/a/b/c" and two entries in fs_location. One entry in fs_location

will be for itself (servA) and the other will be for servB with a

path of "/x/y/z". With this information, the client is able to

substitute "/x/y/z" for the "/a/b/c" at the beginning of its access

path and construct "/x/y/z/d" to use for the new server.

6.4. Filehandle Recovery for Migration or Replication

Filehandles for file systems that are replicated or migrated

generally have the same semantics as for file systems that are not

replicated or migrated. For example, if a file system has persistent

filehandles and it is migrated to another server, the filehandle

values for the file system will be valid at the new server.

For volatile filehandles, the servers involved likely do not have a

mechanism to transfer filehandle format and content between

themselves. Therefore, a server may have difficulty in determining

if a volatile filehandle from an old server should return an error of

NFS4ERR_FHEXPIRED. Therefore, the client is informed, with the use

of the fh_expire_type attribute, whether volatile filehandles will

expire at the migration or replication event. If the bit

FH4_VOL_MIGRATION is set in the fh_expire_type attribute, the client

must treat the volatile filehandle as if the server had returned the

NFS4ERR_FHEXPIRED error. At the migration or replication event in

the presence of the FH4_VOL_MIGRATION bit, the client will not

present the original or old volatile file handle to the new server.

The client will start its communication with the new server by

recovering its filehandles using the saved file names.

7. NFS Server Name Space

7.1. Server Exports

On a UNIX server the name space describes all the files reachable by

pathnames under the root directory or "/". On a Windows NT server

the name space constitutes all the files on disks named by mapped

disk letters. NFS server administrators rarely make the entire

server's file system name space available to NFS clients. More often

portions of the name space are made available via an "export"

feature. In previous versions of the NFS protocol, the root

filehandle for each export is obtained through the MOUNT protocol;

the client sends a string that identifies the export of name space

and the server returns the root filehandle for it. The MOUNT

protocol supports an EXPORTS procedure that will enumerate the

server's exports.

7.2. Browsing Exports

The NFS version 4 protocol provides a root filehandle that clients

can use to obtain filehandles for these exports via a multi-component

LOOKUP. A common user experience is to use a graphical user

interface (perhaps a file "Open" dialog window) to find a file via

progressive browsing through a directory tree. The client must be

able to move from one export to another export via single-component,

progressive LOOKUP operations.

This style of browsing is not well supported by the NFS version 2 and

3 protocols. The client expects all LOOKUP operations to remain

within a single server file system. For example, the device

attribute will not change. This prevents a client from taking name

space paths that span exports.

An automounter on the client can obtain a snapshot of the server's

name space using the EXPORTS procedure of the MOUNT protocol. If it

understands the server's pathname syntax, it can create an image of

the server's name space on the client. The parts of the name space

that are not exported by the server are filled in with a "pseudo file

system" that allows the user to browse from one mounted file system

to another. There is a drawback to this representation of the

server's name space on the client: it is static. If the server

administrator adds a new export the client will be unaware of it.

7.3. Server Pseudo File System

NFS version 4 servers avoid this name space inconsistency by

presenting all the exports within the framework of a single server

name space. An NFS version 4 client uses LOOKUP and READDIR

operations to browse seamlessly from one export to another. Portions

of the server name space that are not exported are bridged via a

"pseudo file system" that provides a view of exported directories

only. A pseudo file system has a unique fsid and behaves like a

normal, read only file system.

Based on the construction of the server's name space, it is possible

that multiple pseudo file systems may exist. For example,

/a pseudo file system

/a/b real file system

/a/b/c pseudo file system

/a/b/c/d real file system

Each of the pseudo file systems are consider separate entities and

therefore will have a unique fsid.

7.4. Multiple Roots

The DOS and Windows operating environments are sometimes described as

having "multiple roots". File systems are commonly represented as

disk letters. MacOS represents file systems as top level names. NFS

version 4 servers for these platforms can construct a pseudo file

system above these root names so that disk letters or volume names

are simply directory names in the pseudo root.

7.5. Filehandle Volatility

The nature of the server's pseudo file system is that it is a logical

representation of file system(s) available from the server.

Therefore, the pseudo file system is most likely constructed

dynamically when the server is first instantiated. It is expected

that the pseudo file system may not have an on disk counterpart from

which persistent filehandles could be constructed. Even though it is

preferable that the server provide persistent filehandles for the

pseudo file system, the NFS client should expect that pseudo file

system filehandles are volatile. This can be confirmed by checking

the associated "fh_expire_type" attribute for those filehandles in

question. If the filehandles are volatile, the NFS client must be

prepared to recover a filehandle value (e.g. with a multi-component

LOOKUP) when receiving an error of NFS4ERR_FHEXPIRED.

7.6. Exported Root

If the server's root file system is exported, one might conclude that

a pseudo-file system is not needed. This would be wrong. Assume the

following file systems on a server:

/ disk1 (exported)

/a disk2 (not exported)

/a/b disk3 (exported)

Because disk2 is not exported, disk3 cannot be reached with simple

LOOKUPs. The server must bridge the gap with a pseudo-file system.

7.7. Mount Point Crossing

The server file system environment may be constructed in such a way

that one file system contains a directory which is 'covered' or

mounted upon by a second file system. For example:

/a/b (file system 1)

/a/b/c/d (file system 2)

The pseudo file system for this server may be constructed to look

like:

/ (place holder/not exported)

/a/b (file system 1)

/a/b/c/d (file system 2)

It is the server's responsibility to present the pseudo file system

that is complete to the client. If the client sends a lookup request

for the path "/a/b/c/d", the server's response is the filehandle of

the file system "/a/b/c/d". In previous versions of the NFS

protocol, the server would respond with the directory "/a/b/c/d"

within the file system "/a/b".

The NFS client will be able to determine if it crosses a server mount

point by a change in the value of the "fsid" attribute.

7.8. Security Policy and Name Space Presentation

The application of the server's security policy needs to be carefully

considered by the implementor. One may choose to limit the

viewability of portions of the pseudo file system based on the

server's perception of the client's ability to authenticate itself

properly. However, with the support of multiple security mechanisms

and the ability to negotiate the appropriate use of these mechanisms,

the server is unable to properly determine if a client will be able

to authenticate itself. If, based on its policies, the server

chooses to limit the contents of the pseudo file system, the server

may effectively hide file systems from a client that may otherwise

have legitimate access.

8. File Locking and Share Reservations

Integrating locking into the NFS protocol necessarily causes it to be

state-full. With the inclusion of "share" file locks the protocol

becomes substantially more dependent on state than the traditional

combination of NFS and NLM [XNFS]. There are three components to

making this state manageable:

o Clear division between client and server

o Ability to reliably detect inconsistency in state between client

and server

o Simple and robust recovery mechanisms

In this model, the server owns the state information. The client

communicates its view of this state to the server as needed. The

client is also able to detect inconsistent state before modifying a

file.

To support Win32 "share" locks it is necessary to atomically OPEN or

CREATE files. Having a separate share/unshare operation would not

allow correct implementation of the Win32 OpenFile API. In order to

correctly implement share semantics, the previous NFS protocol

mechanisms used when a file is opened or created (LOOKUP, CREATE,

ACCESS) need to be replaced. The NFS version 4 protocol has an OPEN

operation that subsumes the functionality of LOOKUP, CREATE, and

ACCESS. However, because many operations require a filehandle, the

traditional LOOKUP is preserved to map a file name to filehandle

without establishing state on the server. The policy of granting

access or modifying files is managed by the server based on the

client's state. These mechanisms can implement policy ranging from

advisory only locking to full mandatory locking.

8.1. Locking

It is assumed that manipulating a lock is rare when compared to READ

and WRITE operations. It is also assumed that crashes and network

partitions are relatively rare. Therefore it is important that the

READ and WRITE operations have a lightweight mechanism to indicate if

they possess a held lock. A lock request contains the heavyweight

information required to establish a lock and uniquely define the lock

owner.

The following sections describe the transition from the heavy weight

information to the eventual stateid used for most client and server

locking and lease interactions.

8.1.1. Client ID

For each LOCK request, the client must identify itself to the server.

This is done in such a way as to allow for correct lock

identification and crash recovery. Client identification is

accomplished with two values.

o A verifier that is used to detect client reboots.

o A variable length opaque array to uniquely define a client.

For an operating system this may be a fully qualified host name

or IP address. For a user level NFS client it may additionally

contain a process id or other unique sequence.

The data structure for the Client ID would then appear as:

struct nfs_client_id {

opaque verifier[4];

opaque id<>;

}

It is possible through the mis-configuration of a client or the

existence of a rogue client that two clients end up using the same

nfs_client_id. This situation is avoided by "negotiating" the

nfs_client_id between client and server with the use of the

SETCLIENTID and SETCLIENTID_CONFIRM operations. The following

describes the two scenarios of negotiation.

1 Client has never connected to the server

In this case the client generates an nfs_client_id and unless

another client has the same nfs_client_id.id field, the server

accepts the request. The server also records the principal (or

principal to uid mapping) from the credential in the RPC request

that contains the nfs_client_id negotiation request (SETCLIENTID

operation).

Two clients might still use the same nfs_client_id.id due to

perhaps configuration error. For example, a High Availability

configuration where the nfs_client_id.id is derived from the

ethernet controller address and both systems have the same

address. In this case, the result is a switched union that

returns, in addition to NFS4ERR_CLID_INUSE, the network address

(the rpcbind netid and universal address) of the client that is

using the id.

2 Client is re-connecting to the server after a client reboot

In this case, the client still generates an nfs_client_id but the

nfs_client_id.id field will be the same as the nfs_client_id.id

generated prior to reboot. If the server finds that the

principal/uid is equal to the previously "registered"

nfs_client_id.id, then locks associated with the old nfs_client_id

are immediately released. If the principal/uid is not equal, then

this is a rogue client and the request is returned in error. For

more discussion of crash recovery semantics, see the section on

"Crash Recovery".

It is possible for a retransmission of request to be received by

the server after the server has acted upon and responded to the

original client request. Therefore to mitigate effects of the

retransmission of the SETCLIENTID operation, the client and server

use a confirmation step. The server returns a confirmation

verifier that the client then sends to the server in the

SETCLIENTID_CONFIRM operation. Once the server receives the

confirmation from the client, the locking state for the client is

released.

In both cases, upon success, NFS4_OK is returned. To help reduce the

amount of data transferred on OPEN and LOCK, the server will also

return a unique 64-bit clientid value that is a shorthand reference

to the nfs_client_id values presented by the client. From this point

forward, the client will use the clientid to refer to itself.

The clientid assigned by the server should be chosen so that it will

not conflict with a clientid previously assigned by the server. This

applies across server restarts or reboots. When a clientid is

presented to a server and that clientid is not recognized, as would

happen after a server reboot, the server will reject the request with

the error NFS4ERR_STALE_CLIENTID. When this happens, the client must

obtain a new clientid by use of the SETCLIENTID operation and then

proceed to any other necessary recovery for the server reboot case

(See the section "Server Failure and Recovery").

The client must also employ the SETCLIENTID operation when it

receives a NFS4ERR_STALE_STATEID error using a stateid derived from

its current clientid, since this also indicates a server reboot which

has invalidated the existing clientid (see the next section

"nfs_lockowner and stateid Definition" for details).

8.1.2. Server Release of Clientid

If the server determines that the client holds no associated state

for its clientid, the server may choose to release the clientid. The

server may make this choice for an inactive client so that resources

are not consumed by those intermittently active clients. If the

client contacts the server after this release, the server must ensure

the client receives the appropriate error so that it will use the

SETCLIENTID/SETCLIENTID_CONFIRM sequence to establish a new identity.

It should be clear that the server must be very hesitant to release a

clientid since the resulting work on the client to recover from such

an event will be the same burden as if the server had failed and

restarted. Typically a server would not release a clientid unless

there had been no activity from that client for many minutes.

8.1.3. nfs_lockowner and stateid Definition

When requesting a lock, the client must present to the server the

clientid and an identifier for the owner of the requested lock.

These two fields are referred to as the nfs_lockowner and the

definition of those fields are:

o A clientid returned by the server as part of the client's use of

the SETCLIENTID operation.

o A variable length opaque array used to uniquely define the owner

of a lock managed by the client.

This may be a thread id, process id, or other unique value.

When the server grants the lock, it responds with a unique 64-bit

stateid. The stateid is used as a shorthand reference to the

nfs_lockowner, since the server will be maintaining the

correspondence between them.

The server is free to form the stateid in any manner that it chooses

as long as it is able to recognize invalid and out-of-date stateids.

This requirement includes those stateids generated by earlier

instances of the server. From this, the client can be properly

notified of a server restart. This notification will occur when the

client presents a stateid to the server from a previous

instantiation.

The server must be able to distinguish the following situations and

return the error as specified:

o The stateid was generated by an earlier server instance (i.e.

before a server reboot). The error NFS4ERR_STALE_STATEID should

be returned.

o The stateid was generated by the current server instance but the

stateid no longer designates the current locking state for the

lockowner-file pair in question (i.e. one or more locking

operations has occurred). The error NFS4ERR_OLD_STATEID should be

returned.

This error condition will only occur when the client issues a

locking request which changes a stateid while an I/O request that

uses that stateid is outstanding.

o The stateid was generated by the current server instance but the

stateid does not designate a locking state for any active

lockowner-file pair. The error NFS4ERR_BAD_STATEID should be

returned.

This error condition will occur when there has been a logic error

on the part of the client or server. This should not happen.

One mechanism that may be used to satisfy these requirements is for

the server to divide stateids into three fields:

o A server verifier which uniquely designates a particular server

instantiation.

o An index into a table of locking-state structures.

o A sequence value which is incremented for each stateid that is

associated with the same index into the locking-state table.

By matching the incoming stateid and its field values with the state

held at the server, the server is able to easily determine if a

stateid is valid for its current instantiation and state. If the

stateid is not valid, the appropriate error can be supplied to the

client.

8.1.4. Use of the stateid

All READ and WRITE operations contain a stateid. If the

nfs_lockowner performs a READ or WRITE on a range of bytes within a

locked range, the stateid (previously returned by the server) must be

used to indicate that the appropriate lock (record or share) is held.

If no state is established by the client, either record lock or share

lock, a stateid of all bits 0 is used. If no conflicting locks are

held on the file, the server may service the READ or WRITE operation.

If a conflict with an explicit lock occurs, an error is returned for

the operation (NFS4ERR_LOCKED). This allows "mandatory locking" to be

implemented.

A stateid of all bits 1 (one) allows READ operations to bypass record

locking checks at the server. However, WRITE operations with stateid

with bits all 1 (one) do not bypass record locking checks. File

locking checks are handled by the OPEN operation (see the section

"OPEN/CLOSE Operations").

An explicit lock may not be granted while a READ or WRITE operation

with conflicting implicit locking is being performed.

8.1.5. Sequencing of Lock Requests

Locking is different than most NFS operations as it requires "at-

most-one" semantics that are not provided by ONCRPC. ONCRPC over a

reliable transport is not sufficient because a sequence of locking

requests may span multiple TCP connections. In the face of

retransmission or reordering, lock or unlock requests must have a

well defined and consistent behavior. To accomplish this, each lock

request contains a sequence number that is a consecutively increasing

integer. Different nfs_lockowners have different sequences. The

server maintains the last sequence number (L) received and the

response that was returned.

Note that for requests that contain a sequence number, for each

nfs_lockowner, there should be no more than one outstanding request.

If a request with a previous sequence number (r < L) is received, it

is rejected with the return of error NFS4ERR_BAD_SEQID. Given a

properly-functioning client, the response to (r) must have been

received before the last request (L) was sent. If a duplicate of

last request (r == L) is received, the stored response is returned.

If a request beyond the next sequence (r == L + 2) is received, it is

rejected with the return of error NFS4ERR_BAD_SEQID. Sequence

history is reinitialized whenever the client verifier changes.

Since the sequence number is represented with an unsigned 32-bit

integer, the arithmetic involved with the sequence number is mod

2^32.

It is critical the server maintain the last response sent to the

client to provide a more reliable cache of duplicate non-idempotent

requests than that of the traditional cache described in [Juszczak].

The traditional duplicate request cache uses a least recently used

algorithm for removing unneeded requests. However, the last lock

request and response on a given nfs_lockowner must be cached as long

as the lock state exists on the server.

8.1.6. Recovery from Replayed Requests

As described above, the sequence number is per nfs_lockowner. As

long as the server maintains the last sequence number received and

follows the methods described above, there are no risks of a

Byzantine router re-sending old requests. The server need only

maintain the nfs_lockowner, sequence number state as long as there

are open files or closed files with locks outstanding.

LOCK, LOCKU, OPEN, OPEN_DOWNGRADE, and CLOSE each contain a sequence

number and therefore the risk of the replay of these operations

resulting in undesired effects is non-existent while the server

maintains the nfs_lockowner state.

8.1.7. Releasing nfs_lockowner State

When a particular nfs_lockowner no longer holds open or file locking

state at the server, the server may choose to release the sequence

number state associated with the nfs_lockowner. The server may make

this choice based on lease expiration, for the reclamation of server

memory, or other implementation specific details. In any event, the

server is able to do this safely only when the nfs_lockowner no

longer is being utilized by the client. The server may choose to

hold the nfs_lockowner state in the event that retransmitted requests

are received. However, the period to hold this state is

implementation specific.

In the case that a LOCK, LOCKU, OPEN_DOWNGRADE, or CLOSE is

retransmitted after the server has previously released the

nfs_lockowner state, the server will find that the nfs_lockowner has

no files open and an error will be returned to the client. If the

nfs_lockowner does have a file open, the stateid will not match and

again an error is returned to the client.

In the case that an OPEN is retransmitted and the nfs_lockowner is

being used for the first time or the nfs_lockowner state has been

previously released by the server, the use of the OPEN_CONFIRM

operation will prevent incorrect behavior. When the server observes

the use of the nfs_lockowner for the first time, it will direct the

client to perform the OPEN_CONFIRM for the corresponding OPEN. This

sequence establishes the use of an nfs_lockowner and associated

sequence number. See the section "OPEN_CONFIRM - Confirm Open" for

further details.

8.2. Lock Ranges

The protocol allows a lock owner to request a lock with one byte

range and then either upgrade or unlock a sub-range of the initial

lock. It is expected that this will be an uncommon type of request.

In any case, servers or server file systems may not be able to

support sub-range lock semantics. In the event that a server

receives a locking request that represents a sub-range of current

locking state for the lock owner, the server is allowed to return the

error NFS4ERR_LOCK_RANGE to signify that it does not support sub-

range lock operations. Therefore, the client should be prepared to

receive this error and, if appropriate, report the error to the

requesting application.

The client is discouraged from combining multiple independent locking

ranges that happen to be adjacent into a single request since the

server may not support sub-range requests and for reasons related to

the recovery of file locking state in the event of server failure.

As discussed in the section "Server Failure and Recovery" below, the

server may employ certain optimizations during recovery that work

effectively only when the client's behavior during lock recovery is

similar to the client's locking behavior prior to server failure.

8.3. Blocking Locks

Some clients require the support of blocking locks. The NFS version

4 protocol must not rely on a callback mechanism and therefore is

unable to notify a client when a previously denied lock has been

granted. Clients have no choice but to continually poll for the

lock. This presents a fairness problem. Two new lock types are

added, READW and WRITEW, and are used to indicate to the server that

the client is requesting a blocking lock. The server should maintain

an ordered list of pending blocking locks. When the conflicting lock

is released, the server may wait the lease period for the first

waiting client to re-request the lock. After the lease period

expires the next waiting client request is allowed the lock. Clients

are required to poll at an interval sufficiently small that it is

likely to acquire the lock in a timely manner. The server is not

required to maintain a list of pending blocked locks as it is used to

increase fairness and not correct operation. Because of the

unordered nature of crash recovery, storing of lock state to stable

storage would be required to guarantee ordered granting of blocking

locks.

Servers may also note the lock types and delay returning denial of

the request to allow extra time for a conflicting lock to be

released, allowing a successful return. In this way, clients can

avoid the burden of needlessly frequent polling for blocking locks.

The server should take care in the length of delay in the event the

client retransmits the request.

8.4. Lease Renewal

The purpose of a lease is to allow a server to remove stale locks

that are held by a client that has crashed or is otherwise

unreachable. It is not a mechanism for cache consistency and lease

renewals may not be denied if the lease interval has not expired.

The following events cause implicit renewal of all of the leases for

a given client (i.e. all those sharing a given clientid). Each of

these is a positive indication that the client is still active and

that the associated state held at the server, for the client, is

still valid.

o An OPEN with a valid clientid.

o Any operation made with a valid stateid (CLOSE, DELEGRETURN, LOCK,

LOCKU, OPEN, OPEN_CONFIRM, READ, RENEW, SETATTR, WRITE). This

does not include the special stateids of all bits 0 or all bits 1.

Note that if the client had restarted or rebooted, the client

would not be making these requests without issuing the

SETCLIENTID operation. The use of the SETCLIENTID operation

(possibly with the addition of the optional SETCLIENTID_CONFIRM

operation) notifies the server to drop the locking state

associated with the client.

If the server has rebooted, the stateids (NFS4ERR_STALE_STATEID

error) or the clientid (NFS4ERR_STALE_CLIENTID error) will not

be valid hence preventing spurious renewals.

This approach allows for low overhead lease renewal which scales

well. In the typical case no extra RPC calls are required for lease

renewal and in the worst case one RPC is required every lease period

(i.e. a RENEW operation). The number of locks held by the client is

not a factor since all state for the client is involved with the

lease renewal action.

Since all operations that create a new lease also renew existing

leases, the server must maintain a common lease expiration time for

all valid leases for a given client. This lease time can then be

easily updated upon implicit lease renewal actions.

8.5. Crash Recovery

The important requirement in crash recovery is that both the client

and the server know when the other has failed. Additionally, it is

required that a client sees a consistent view of data across server

restarts or reboots. All READ and WRITE operations that may have

been queued within the client or network buffers must wait until the

client has successfully recovered the locks protecting the READ and

WRITE operations.

8.5.1. Client Failure and Recovery

In the event that a client fails, the server may recover the client's

locks when the associated leases have expired. Conflicting locks

from another client may only be granted after this lease expiration.

If the client is able to restart or reinitialize within the lease

period the client may be forced to wait the remainder of the lease

period before obtaining new locks.

To minimize client delay upon restart, lock requests are associated

with an instance of the client by a client supplied verifier. This

verifier is part of the initial SETCLIENTID call made by the client.

The server returns a clientid as a result of the SETCLIENTID

operation. The client then confirms the use of the verifier with

SETCLIENTID_CONFIRM. The clientid in combination with an opaque

owner field is then used by the client to identify the lock owner for

OPEN. This chain of associations is then used to identify all locks

for a particular client.

Since the verifier will be changed by the client upon each

initialization, the server can compare a new verifier to the verifier

associated with currently held locks and determine that they do not

match. This signifies the client's new instantiation and subsequent

loss of locking state. As a result, the server is free to release

all locks held which are associated with the old clientid which was

derived from the old verifier.

For secure environments, a change in the verifier must only cause the

release of locks associated with the authenticated requester. This

is required to prevent a rogue entity from freeing otherwise valid

locks.

Note that the verifier must have the same uniqueness properties of

the verifier for the COMMIT operation.

8.5.2. Server Failure and Recovery

If the server loses locking state (usually as a result of a restart

or reboot), it must allow clients time to discover this fact and re-

establish the lost locking state. The client must be able to re-

establish the locking state without having the server deny valid

requests because the server has granted conflicting access to another

client. Likewise, if there is the possibility that clients have not

yet re-established their locking state for a file, the server must

disallow READ and WRITE operations for that file. The duration of

this recovery period is equal to the duration of the lease period.

A client can determine that server failure (and thus loss of locking

state) has occurred, when it receives one of two errors. The

NFS4ERR_STALE_STATEID error indicates a stateid invalidated by a

reboot or restart. The NFS4ERR_STALE_CLIENTID error indicates a

clientid invalidated by reboot or restart. When either of these are

received, the client must establish a new clientid (See the section

"Client ID") and re-establish the locking state as discussed below.

The period of special handling of locking and READs and WRITEs, equal

in duration to the lease period, is referred to as the "grace

period". During the grace period, clients recover locks and the

associated state by reclaim-type locking requests (i.e. LOCK requests

with reclaim set to true and OPEN operations with a claim type of

CLAIM_PREVIOUS). During the grace period, the server must reject

READ and WRITE operations and non-reclaim locking requests (i.e.

other LOCK and OPEN operations) with an error of NFS4ERR_GRACE.

If the server can reliably determine that granting a non-reclaim

request will not conflict with reclamation of locks by other clients,

the NFS4ERR_GRACE error does not have to be returned and the non-

reclaim client request can be serviced. For the server to be able to

service READ and WRITE operations during the grace period, it must

again be able to guarantee that no possible conflict could arise

between an impending reclaim locking request and the READ or WRITE

operation. If the server is unable to offer that guarantee, the

NFS4ERR_GRACE error must be returned to the client.

For a server to provide simple, valid handling during the grace

period, the easiest method is to simply reject all non-reclaim

locking requests and READ and WRITE operations by returning the

NFS4ERR_GRACE error. However, a server may keep information about

granted locks in stable storage. With this information, the server

could determine if a regular lock or READ or WRITE operation can be

safely processed.

For example, if a count of locks on a given file is available in

stable storage, the server can track reclaimed locks for the file and

when all reclaims have been processed, non-reclaim locking requests

may be processed. This way the server can ensure that non-reclaim

locking requests will not conflict with potential reclaim requests.

With respect to I/O requests, if the server is able to determine that

there are no outstanding reclaim requests for a file by information

from stable storage or another similar mechanism, the processing of

I/O requests could proceed normally for the file.

To reiterate, for a server that allows non-reclaim lock and I/O

requests to be processed during the grace period, it MUST determine

that no lock subsequently reclaimed will be rejected and that no lock

subsequently reclaimed would have prevented any I/O operation

processed during the grace period.

Clients should be prepared for the return of NFS4ERR_GRACE errors for

non-reclaim lock and I/O requests. In this case the client should

employ a retry mechanism for the request. A delay (on the order of

several seconds) between retries should be used to avoid overwhelming

the server. Further discussion of the general is included in

[Floyd]. The client must account for the server that is able to

perform I/O and non-reclaim locking requests within the grace period

as well as those that can not do so.

A reclaim-type locking request outside the server's grace period can

only succeed if the server can guarantee that no conflicting lock or

I/O request has been granted since reboot or restart.

8.5.3. Network Partitions and Recovery

If the duration of a network partition is greater than the lease

period provided by the server, the server will have not received a

lease renewal from the client. If this occurs, the server may free

all locks held for the client. As a result, all stateids held by the

client will become invalid or stale. Once the client is able to

reach the server after such a network partition, all I/O submitted by

the client with the now invalid stateids will fail with the server

returning the error NFS4ERR_EXPIRED. Once this error is received,

the client will suitably notify the application that held the lock.

As a courtesy to the client or as an optimization, the server may

continue to hold locks on behalf of a client for which recent

communication has extended beyond the lease period. If the server

receives a lock or I/O request that conflicts with one of these

courtesy locks, the server must free the courtesy lock and grant the

new request.

If the server continues to hold locks beyond the expiration of a

client's lease, the server MUST employ a method of recording this

fact in its stable storage. Conflicting locks requests from another

client may be serviced after the lease expiration. There are various

scenarios involving server failure after such an event that require

the storage of these lease expirations or network partitions. One

scenario is as follows:

A client holds a lock at the server and encounters a network

partition and is unable to renew the associated lease. A

second client obtains a conflicting lock and then frees the

lock. After the unlock request by the second client, the

server reboots or reinitializes. Once the server recovers, the

network partition heals and the original client attempts to

reclaim the original lock.

In this scenario and without any state information, the server will

allow the reclaim and the client will be in an inconsistent state

because the server or the client has no knowledge of the conflicting

lock.

The server may choose to store this lease expiration or network

partitioning state in a way that will only identify the client as a

whole. Note that this may potentially lead to lock reclaims being

denied unnecessarily because of a mix of conflicting and non-

conflicting locks. The server may also choose to store information

about each lock that has an expired lease with an associated

conflicting lock. The choice of the amount and type of state

information that is stored is left to the implementor. In any case,

the server must have enough state information to enable correct

recovery from multiple partitions and multiple server failures.

8.6. Recovery from a Lock Request Timeout or Abort

In the event a lock request times out, a client may decide to not

retry the request. The client may also abort the request when the

process for which it was issued is terminated (e.g. in UNIX due to a

signal. It is possible though that the server received the request

and acted upon it. This would change the state on the server without

the client being aware of the change. It is paramount that the

client re-synchronize state with server before it attempts any other

operation that takes a seqid and/or a stateid with the same

nfs_lockowner. This is straightforward to do without a special re-

synchronize operation.

Since the server maintains the last lock request and response

received on the nfs_lockowner, for each nfs_lockowner, the client

should cache the last lock request it sent such that the lock request

did not receive a response. From this, the next time the client does

a lock operation for the nfs_lockowner, it can send the cached

request, if there is one, and if the request was one that established

state (e.g. a LOCK or OPEN operation) the client can follow up with a

request to remove the state (e.g. a LOCKU or CLOSE operation). With

this approach, the sequencing and stateid information on the client

and server for the given nfs_lockowner will re-synchronize and in

turn the lock state will re-synchronize.

8.7. Server Revocation of Locks

At any point, the server can revoke locks held by a client and the

client must be prepared for this event. When the client detects that

its locks have been or may have been revoked, the client is

responsible for validating the state information between itself and

the server. Validating locking state for the client means that it

must verify or reclaim state for each lock currently held.

The first instance of lock revocation is upon server reboot or re-

initialization. In this instance the client will receive an error

(NFS4ERR_STALE_STATEID or NFS4ERR_STALE_CLIENTID) and the client will

proceed with normal crash recovery as described in the previous

section.

The second lock revocation event is the inability to renew the lease

period. While this is considered a rare or unusual event, the client

must be prepared to recover. Both the server and client will be able

to detect the failure to renew the lease and are capable of

recovering without data corruption. For the server, it tracks the

last renewal event serviced for the client and knows when the lease

will expire. Similarly, the client must track operations which will

renew the lease period. Using the time that each such request was

sent and the time that the corresponding reply was received, the

client should bound the time that the corresponding renewal could

have occurred on the server and thus determine if it is possible that

a lease period expiration could have occurred.

The third lock revocation event can occur as a result of

administrative intervention within the lease period. While this is

considered a rare event, it is possible that the server's

administrator has decided to release or revoke a particular lock held

by the client. As a result of revocation, the client will receive an

error of NFS4ERR_EXPIRED and the error is received within the lease

period for the lock. In this instance the client may assume that

only the nfs_lockowner's locks have been lost. The client notifies

the lock holder appropriately. The client may not assume the lease

period has been renewed as a result of failed operation.

When the client determines the lease period may have expired, the

client must mark all locks held for the associated lease as

"unvalidated". This means the client has been unable to re-establish

or confirm the appropriate lock state with the server. As described

in the previous section on crash recovery, there are scenarios in

which the server may grant conflicting locks after the lease period

has expired for a client. When it is possible that the lease period

has expired, the client must validate each lock currently held to

ensure that a conflicting lock has not been granted. The client may

accomplish this task by issuing an I/O request, either a pending I/O

or a zero-length read, specifying the stateid associated with the

lock in question. If the response to the request is success, the

client has validated all of the locks governed by that stateid and

re-established the appropriate state between itself and the server.

If the I/O request is not successful, then one or more of the locks

associated with the stateid was revoked by the server and the client

must notify the owner.

8.8. Share Reservations

A share reservation is a mechanism to control access to a file. It

is a separate and independent mechanism from record locking. When a

client opens a file, it issues an OPEN operation to the server

specifying the type of access required (READ, WRITE, or BOTH) and the

type of access to deny others (deny NONE, READ, WRITE, or BOTH). If

the OPEN fails the client will fail the application's open request.

Pseudo-code definition of the semantics:

if ((request.access & file_state.deny))

(request.deny & file_state.access))

return (NFS4ERR_DENIED)

The constants used for the OPEN and OPEN_DOWNGRADE operations for the

access and deny fields are as follows:

const OPEN4_SHARE_ACCESS_READ = 0x00000001;

const OPEN4_SHARE_ACCESS_WRITE = 0x00000002;

const OPEN4_SHARE_ACCESS_BOTH = 0x00000003;

const OPEN4_SHARE_DENY_NONE = 0x00000000;

const OPEN4_SHARE_DENY_READ = 0x00000001;

const OPEN4_SHARE_DENY_WRITE = 0x00000002;

const OPEN4_SHARE_DENY_BOTH = 0x00000003;

8.9. OPEN/CLOSE Operations

To provide correct share semantics, a client MUST use the OPEN

operation to obtain the initial filehandle and indicate the desired

access and what if any access to deny. Even if the client intends to

use a stateid of all 0's or all 1's, it must still obtain the

filehandle for the regular file with the OPEN operation so the

appropriate share semantics can be applied. For clients that do not

have a deny mode built into their open programming interfaces, deny

equal to NONE should be used.

The OPEN operation with the CREATE flag, also subsumes the CREATE

operation for regular files as used in previous versions of the NFS

protocol. This allows a create with a share to be done atomically.

The CLOSE operation removes all share locks held by the nfs_lockowner

on that file. If record locks are held, the client SHOULD release

all locks before issuing a CLOSE. The server MAY free all

outstanding locks on CLOSE but some servers may not support the CLOSE

of a file that still has record locks held. The server MUST return

failure if any locks would exist after the CLOSE.

The LOOKUP operation will return a filehandle without establishing

any lock state on the server. Without a valid stateid, the server

will assume the client has the least access. For example, a file

opened with deny READ/WRITE cannot be accessed using a filehandle

obtained through LOOKUP because it would not have a valid stateid

(i.e. using a stateid of all bits 0 or all bits 1).

8.10. Open Upgrade and Downgrade

When an OPEN is done for a file and the lockowner for which the open

is being done already has the file open, the result is to upgrade the

open file status maintained on the server to include the access and

deny bits specified by the new OPEN as well as those for the existing

OPEN. The result is that there is one open file, as far as the

protocol is concerned, and it includes the union of the access and

deny bits for all of the OPEN requests completed. Only a single

CLOSE will be done to reset the effects of both OPEN's. Note that

the client, when issuing the OPEN, may not know that the same file is

in fact being opened. The above only applies if both OPEN's result

in the OPEN'ed object being designated by the same filehandle.

When the server chooses to export multiple filehandles corresponding

to the same file object and returns different filehandles on two

different OPEN's of the same file object, the server MUST NOT "OR"

together the access and deny bits and coalesce the two open files.

Instead the server must maintain separate OPEN's with separate

stateid's and will require separate CLOSE's to free them.

When multiple open files on the client are merged into a single open

file object on the server, the close of one of the open files (on the

client) may necessitate change of the access and deny status of the

open file on the server. This is because the union of the access and

deny bits for the remaining open's may be smaller (i.e. a proper

subset) than previously. The OPEN_DOWNGRADE operation is used to

make the necessary change and the client should use it to update the

server so that share reservation requests by other clients are

handled properly.

8.11. Short and Long Leases

When determining the time period for the server lease, the usual

lease tradeoffs apply. Short leases are good for fast server

recovery at a cost of increased RENEW or READ (with zero length)

requests. Longer leases are certainly kinder and gentler to large

internet servers trying to handle very large numbers of clients. The

number of RENEW requests drop in proportion to the lease time. The

disadvantages of long leases are slower recovery after server failure

(server must wait for leases to expire and grace period before

granting new lock requests) and increased file contention (if client

fails to transmit an unlock request then server must wait for lease

expiration before granting new locks).

Long leases are usable if the server is able to store lease state in

non-volatile memory. Upon recovery, the server can reconstruct the

lease state from its non-volatile memory and continue operation with

its clients and therefore long leases are not an issue.

8.12. Clocks and Calculating Lease Expiration

To avoid the need for synchronized clocks, lease times are granted by

the server as a time delta. However, there is a requirement that the

client and server clocks do not drift excessively over the duration

of the lock. There is also the issue of propagation delay across the

network which could easily be several hundred milliseconds as well as

the possibility that requests will be lost and need to be

retransmitted.

To take propagation delay into account, the client should subtract it

from lease times (e.g. if the client estimates the one-way

propagation delay as 200 msec, then it can assume that the lease is

already 200 msec old when it gets it). In addition, it will take

another 200 msec to get a response back to the server. So the client

must send a lock renewal or write data back to the server 400 msec

before the lease would expire.

8.13. Migration, Replication and State

When responsibility for handling a given file system is transferred

to a new server (migration) or the client chooses to use an alternate

server (e.g. in response to server unresponsiveness) in the context

of file system replication, the appropriate handling of state shared

between the client and server (i.e. locks, leases, stateid's, and

clientid's) is as described below. The handling differs between

migration and replication. For related discussion of file server

state and recover of such see the sections under "File Locking and

Share Reservations"

8.13.1. Migration and State

In the case of migration, the servers involved in the migration of a

file system SHOULD transfer all server state from the original to the

new server. This must be done in a way that is transparent to the

client. This state transfer will ease the client's transition when a

file system migration occurs. If the servers are successful in

transferring all state, the client will continue to use stateid's

assigned by the original server. Therefore the new server must

recognize these stateid's as valid. This holds true for the clientid

as well. Since responsibility for an entire file system is

transferred with a migration event, there is no possibility that

conflicts will arise on the new server as a result of the transfer of

locks.

As part of the transfer of information between servers, leases would

be transferred as well. The leases being transferred to the new

server will typically have a different expiration time from those for

the same client, previously on the new server. To maintain the

property that all leases on a given server for a given client expire

at the same time, the server should advance the expiration time to

the later of the leases being transferred or the leases already

present. This allows the client to maintain lease renewal of both

classes without special effort.

The servers may choose not to transfer the state information upon

migration. However, this choice is discouraged. In this case, when

the client presents state information from the original server, the

client must be prepared to receive either NFS4ERR_STALE_CLIENTID or

NFS4ERR_STALE_STATEID from the new server. The client should then

recover its state information as it normally would in response to a

server failure. The new server must take care to allow for the

recovery of state information as it would in the event of server

restart.

8.13.2. Replication and State

Since client switch-over in the case of replication is not under

server control, the handling of state is different. In this case,

leases, stateid's and clientid's do not have validity across a

transition from one server to another. The client must re-establish

its locks on the new server. This can be compared to the re-

establishment of locks by means of reclaim-type requests after a

server reboot. The difference is that the server has no provision to

distinguish requests reclaiming locks from those obtaining new locks

or to defer the latter. Thus, a client re-establishing a lock on the

new server (by means of a LOCK or OPEN request), may have the

requests denied due to a conflicting lock. Since replication is

intended for read-only use of filesystems, such denial of locks

should not pose large difficulties in practice. When an attempt to

re-establish a lock on a new server is denied, the client should

treat the situation as if his original lock had been revoked.

8.13.3. Notification of Migrated Lease

In the case of lease renewal, the client may not be submitting

requests for a file system that has been migrated to another server.

This can occur because of the implicit lease renewal mechanism. The

client renews leases for all file systems when submitting a request

to any one file system at the server.

In order for the client to schedule renewal of leases that may have

been relocated to the new server, the client must find out about

lease relocation before those leases expire. To accomplish this, all

operations which implicitly renew leases for a client (i.e. OPEN,

CLOSE, READ, WRITE, RENEW, LOCK, LOCKT, LOCKU), will return the error

NFS4ERR_LEASE_MOVED if responsibility for any of the leases to be

renewed has been transferred to a new server. This condition will

continue until the client receives an NFS4ERR_MOVED error and the

server receives the subsequent GETATTR(fs_locations) for an access to

each file system for which a lease has been moved to a new server.

When a client receives an NFS4ERR_LEASE_MOVED error, it should

perform some operation, such as a RENEW, on each file system

associated with the server in question. When the client receives an

NFS4ERR_MOVED error, the client can follow the normal process to

obtain the new server information (through the fs_locations

attribute) and perform renewal of those leases on the new server. If

the server has not had state transferred to it transparently, it will

receive either NFS4ERR_STALE_CLIENTID or NFS4ERR_STALE_STATEID from

the new server, as described above, and can then recover state

information as it does in the event of server failure.

9. Client-Side Caching

Client-side caching of data, of file attributes, and of file names is

essential to providing good performance with the NFS protocol.

Providing distributed cache coherence is a difficult problem and

previous versions of the NFS protocol have not attempted it.

Instead, several NFS client implementation techniques have been used

to reduce the problems that a lack of coherence poses for users.

These techniques have not been clearly defined by earlier protocol

specifications and it is often unclear what is valid or invalid

client behavior.

The NFS version 4 protocol uses many techniques similar to those that

have been used in previous protocol versions. The NFS version 4

protocol does not provide distributed cache coherence. However, it

defines a more limited set of caching guarantees to allow locks and

share reservations to be used without destructive interference from

client side caching.

In addition, the NFS version 4 protocol introduces a delegation

mechanism which allows many decisions normally made by the server to

be made locally by clients. This mechanism provides efficient

support of the common cases where sharing is infrequent or where

sharing is read-only.

9.1. Performance Challenges for Client-Side Caching

Caching techniques used in previous versions of the NFS protocol have

been successful in providing good performance. However, several

scalability challenges can arise when those techniques are used with

very large numbers of clients. This is particularly true when

clients are geographically distributed which classically increases

the latency for cache revalidation requests.

The previous versions of the NFS protocol repeat their file data

cache validation requests at the time the file is opened. This

behavior can have serious performance drawbacks. A common case is

one in which a file is only accessed by a single client. Therefore,

sharing is infrequent.

In this case, repeated reference to the server to find that no

conflicts exist is expensive. A better option with regards to

performance is to allow a client that repeatedly opens a file to do

so without reference to the server. This is done until potentially

conflicting operations from another client actually occur.

A similar situation arises in connection with file locking. Sending

file lock and unlock requests to the server as well as the read and

write requests necessary to make data caching consistent with the

locking semantics (see the section "Data Caching and File Locking")

can severely limit performance. When locking is used to provide

protection against infrequent conflicts, a large penalty is incurred.

This penalty may discourage the use of file locking by applications.

The NFS version 4 protocol provides more aggressive caching

strategies with the following design goals:

o Compatibility with a large range of server semantics.

o Provide the same caching benefits as previous versions of the NFS

protocol when unable to provide the more aggressive model.

o Requirements for aggressive caching are organized so that a large

portion of the benefit can be obtained even when not all of the

requirements can be met.

The appropriate requirements for the server are discussed in later

sections in which specific forms of caching are covered. (see the

section "Open Delegation").

9.2. Delegation and Callbacks

Recallable delegation of server responsibilities for a file to a

client improves performance by avoiding repeated requests to the

server in the absence of inter-client conflict. With the use of a

"callback" RPC from server to client, a server recalls delegated

responsibilities when another client engages in sharing of a

delegated file.

A delegation is passed from the server to the client, specifying the

object of the delegation and the type of delegation. There are

different types of delegations but each type contains a stateid to be

used to represent the delegation when performing operations that

depend on the delegation. This stateid is similar to those

associated with locks and share reservations but differs in that the

stateid for a delegation is associated with a clientid and may be

used on behalf of all the nfs_lockowners for the given client. A

delegation is made to the client as a whole and not to any specific

process or thread of control within it.

Because callback RPCs may not work in all environments (due to

firewalls, for example), correct protocol operation does not depend

on them. Preliminary testing of callback functionality by means of a

CB_NULL procedure determines whether callbacks can be supported. The

CB_NULL procedure checks the continuity of the callback path. A

server makes a preliminary assessment of callback availability to a

given client and avoids delegating responsibilities until it has

determined that callbacks are supported. Because the granting of a

delegation is always conditional upon the absence of conflicting

access, clients must not assume that a delegation will be granted and

they must always be prepared for OPENs to be processed without any

delegations being granted.

Once granted, a delegation behaves in most ways like a lock. There

is an associated lease that is subject to renewal together with all

of the other leases held by that client.

Unlike locks, an operation by a second client to a delegated file

will cause the server to recall a delegation through a callback.

On recall, the client holding the delegation must flush modified

state (such as modified data) to the server and return the

delegation. The conflicting request will not receive a response

until the recall is complete. The recall is considered complete when

the client returns the delegation or the server times out on the

recall and revokes the delegation as a result of the timeout.

Following the resolution of the recall, the server has the

information necessary to grant or deny the second client's request.

At the time the client receives a delegation recall, it may have

substantial state that needs to be flushed to the server. Therefore,

the server should allow sufficient time for the delegation to be

returned since it may involve numerous RPCs to the server. If the

server is able to determine that the client is diligently flushing

state to the server as a result of the recall, the server may extend

the usual time allowed for a recall. However, the time allowed for

recall completion should not be unbounded.

An example of this is when responsibility to mediate opens on a given

file is delegated to a client (see the section "Open Delegation").

The server will not know what opens are in effect on the client.

Without this knowledge the server will be unable to determine if the

access and deny state for the file allows any particular open until

the delegation for the file has been returned.

A client failure or a network partition can result in failure to

respond to a recall callback. In this case, the server will revoke

the delegation which in turn will render useless any modified state

still on the client.

9.2.1. Delegation Recovery

There are three situations that delegation recovery must deal with:

o Client reboot or restart

o Server reboot or restart

o Network partition (full or callback-only)

In the event the client reboots or restarts, the failure to renew

leases will result in the revocation of record locks and share

reservations. Delegations, however, may be treated a bit

differently.

There will be situations in which delegations will need to be

reestablished after a client reboots or restarts. The reason for

this is the client may have file data stored locally and this data

was associated with the previously held delegations. The client will

need to reestablish the appropriate file state on the server.

To allow for this type of client recovery, the server may extend the

period for delegation recovery beyond the typical lease expiration

period. This implies that requests from other clients that conflict

with these delegations will need to wait. Because the normal recall

process may require significant time for the client to flush changed

state to the server, other clients need be prepared for delays that

occur because of a conflicting delegation. This longer interval

would increase the window for clients to reboot and consult stable

storage so that the delegations can be reclaimed. For open

delegations, such delegations are reclaimed using OPEN with a claim

type of CLAIM_DELEGATE_PREV. (see the sections on "Data Caching and

Revocation" and "Operation 18: OPEN" for discussion of open

delegation and the details of OPEN respectively).

When the server reboots or restarts, delegations are reclaimed (using

the OPEN operation with CLAIM_DELEGATE_PREV) in a similar fashion to

record locks and share reservations. However, there is a slight

semantic difference. In the normal case if the server decides that a

delegation should not be granted, it performs the requested action

(e.g. OPEN) without granting any delegation. For reclaim, the server

grants the delegation but a special designation is applied so that

the client treats the delegation as having been granted but recalled

by the server. Because of this, the client has the duty to write all

modified state to the server and then return the delegation. This

process of handling delegation reclaim reconciles three principles of

the NFS Version 4 protocol:

o Upon reclaim, a client reporting resources assigned to it by an

earlier server instance must be granted those resources.

o The server has unquestionable authority to determine whether

delegations are to be granted and, once granted, whether they are

to be continued.

o The use of callbacks is not to be depended upon until the client

has proven its ability to receive them.

When a network partition occurs, delegations are subject to freeing

by the server when the lease renewal period expires. This is similar

to the behavior for locks and share reservations. For delegations,

however, the server may extend the period in which conflicting

requests are held off. Eventually the occurrence of a conflicting

request from another client will cause revocation of the delegation.

A loss of the callback path (e.g. by later network configuration

change) will have the same effect. A recall request will fail and

revocation of the delegation will result.

A client normally finds out about revocation of a delegation when it

uses a stateid associated with a delegation and receives the error

NFS4ERR_EXPIRED. It also may find out about delegation revocation

after a client reboot when it attempts to reclaim a delegation and

receives that same error. Note that in the case of a revoked write

open delegation, there are issues because data may have been modified

by the client whose delegation is revoked and separately by other

clients. See the section "Revocation Recovery for Write Open

Delegation" for a discussion of such issues. Note also that when

delegations are revoked, information about the revoked delegation

will be written by the server to stable storage (as described in the

section "Crash Recovery"). This is done to deal with the case in

which a server reboots after revoking a delegation but before the

client holding the revoked delegation is notified about the

revocation.

9.3. Data Caching

When applications share access to a set of files, they need to be

implemented so as to take account of the possibility of conflicting

access by another application. This is true whether the applications

in question execute on different clients or reside on the same

client.

Share reservations and record locks are the facilities the NFS

version 4 protocol provides to allow applications to coordinate

access by providing mutual exclusion facilities. The NFS version 4

protocol's data caching must be implemented such that it does not

invalidate the assumptions that those using these facilities depend

upon.

9.3.1. Data Caching and OPENs

In order to avoid invalidating the sharing assumptions that

applications rely on, NFS version 4 clients should not provide cached

data to applications or modify it on behalf of an application when it

would not be valid to obtain or modify that same data via a READ or

WRITE operation.

Furthermore, in the absence of open delegation (see the section "Open

Delegation") two additional rules apply. Note that these rules are

obeyed in practice by many NFS version 2 and version 3 clients.

o First, cached data present on a client must be revalidated after

doing an OPEN. This is to ensure that the data for the OPENed

file is still correctly reflected in the client's cache. This

validation must be done at least when the client's OPEN operation

includes DENY=WRITE or BOTH thus terminating a period in which

other clients may have had the opportunity to open the file with

WRITE access. Clients may choose to do the revalidation more

often (i.e. at OPENs specifying DENY=NONE) to parallel the NFS

version 3 protocol's practice for the benefit of users assuming

this degree of cache revalidation.

o Second, modified data must be flushed to the server before closing

a file OPENed for write. This is complementary to the first rule.

If the data is not flushed at CLOSE, the revalidation done after

client OPENs as file is unable to achieve its purpose. The other

ASPect to flushing the data before close is that the data must be

committed to stable storage, at the server, before the CLOSE

operation is requested by the client. In the case of a server

reboot or restart and a CLOSEd file, it may not be possible to

retransmit the data to be written to the file. Hence, this

requirement.

9.3.2. Data Caching and File Locking

For those applications that choose to use file locking instead of

share reservations to exclude inconsistent file access, there is an

analogous set of constraints that apply to client side data caching.

These rules are effective only if the file locking is used in a way

that matches in an equivalent way the actual READ and WRITE

operations executed. This is as opposed to file locking that is

based on pure convention. For example, it is possible to manipulate

a two-megabyte file by dividing the file into two one-megabyte

regions and protecting access to the two regions by file locks on

bytes zero and one. A lock for write on byte zero of the file would

represent the right to do READ and WRITE operations on the first

region. A lock for write on byte one of the file would represent the

right to do READ and WRITE operations on the second region. As long

as all applications manipulating the file obey this convention, they

will work on a local file system. However, they may not work with

the NFS version 4 protocol unless clients refrain from data caching.

The rules for data caching in the file locking environment are:

o First, when a client obtains a file lock for a particular region,

the data cache corresponding to that region (if any cache data

exists) must be revalidated. If the change attribute indicates

that the file may have been updated since the cached data was

obtained, the client must flush or invalidate the cached data for

the newly locked region. A client might choose to invalidate all

of non-modified cached data that it has for the file but the only

requirement for correct operation is to invalidate all of the data

in the newly locked region.

o Second, before releasing a write lock for a region, all modified

data for that region must be flushed to the server. The modified

data must also be written to stable storage.

Note that flushing data to the server and the invalidation of cached

data must reflect the actual byte ranges locked or unlocked.

Rounding these up or down to reflect client cache block boundaries

will cause problems if not carefully done. For example, writing a

modified block when only half of that block is within an area being

unlocked may cause invalid modification to the region outside the

unlocked area. This, in turn, may be part of a region locked by

another client. Clients can avoid this situation by synchronously

performing portions of write operations that overlap that portion

(initial or final) that is not a full block. Similarly, invalidating

a locked area which is not an integral number of full buffer blocks

would require the client to read one or two partial blocks from the

server if the revalidation procedure shows that the data which the

client possesses may not be valid.

The data that is written to the server as a pre-requisite to the

unlocking of a region must be written, at the server, to stable

storage. The client may accomplish this either with synchronous

writes or by following asynchronous writes with a COMMIT operation.

This is required because retransmission of the modified data after a

server reboot might conflict with a lock held by another client.

A client implementation may choose to accommodate applications which

use record locking in non-standard ways (e.g. using a record lock as

a global semaphore) by flushing to the server more data upon an LOCKU

than is covered by the locked range. This may include modified data

within files other than the one for which the unlocks are being done.

In such cases, the client must not interfere with applications whose

READs and WRITEs are being done only within the bounds of record

locks which the application holds. For example, an application locks

a single byte of a file and proceeds to write that single byte. A

client that chose to handle a LOCKU by flushing all modified data to

the server could validly write that single byte in response to an

unrelated unlock. However, it would not be valid to write the entire

block in which that single written byte was located since it includes

an area that is not locked and might be locked by another client.

Client implementations can avoid this problem by dividing files with

modified data into those for which all modifications are done to

areas covered by an appropriate record lock and those for which there

are modifications not covered by a record lock. Any writes done for

the former class of files must not include areas not locked and thus

not modified on the client.

9.3.3. Data Caching and Mandatory File Locking

Client side data caching needs to respect mandatory file locking when

it is in effect. The presence of mandatory file locking for a given

file is indicated in the result flags for an OPEN. When mandatory

locking is in effect for a file, the client must check for an

appropriate file lock for data being read or written. If a lock

exists for the range being read or written, the client may satisfy

the request using the client's validated cache. If an appropriate

file lock is not held for the range of the read or write, the read or

write request must not be satisfied by the client's cache and the

request must be sent to the server for processing. When a read or

write request partially overlaps a locked region, the request should

be subdivided into multiple pieces with each region (locked or not)

treated appropriately.

9.3.4. Data Caching and File Identity

When clients cache data, the file data needs to organized according

to the file system object to which the data belongs. For NFS version

3 clients, the typical practice has been to assume for the purpose of

caching that distinct filehandles represent distinct file system

objects. The client then has the choice to organize and maintain the

data cache on this basis.

In the NFS version 4 protocol, there is now the possibility to have

significant deviations from a "one filehandle per object" model

because a filehandle may be constructed on the basis of the object's

pathname. Therefore, clients need a reliable method to determine if

two filehandles designate the same file system object. If clients

were simply to assume that all distinct filehandles denote distinct

objects and proceed to do data caching on this basis, caching

inconsistencies would arise between the distinct client side objects

which mapped to the same server side object.

By providing a method to differentiate filehandles, the NFS version 4

protocol alleviates a potential functional regression in comparison

with the NFS version 3 protocol. Without this method, caching

inconsistencies within the same client could occur and this has not

been present in previous versions of the NFS protocol. Note that it

is possible to have such inconsistencies with applications executing

on multiple clients but that is not the issue being addressed here.

For the purposes of data caching, the following steps allow an NFS

version 4 client to determine whether two distinct filehandles denote

the same server side object:

o If GETATTR directed to two filehandles have different values of

the fsid attribute, then the filehandles represent distinct

objects.

o If GETATTR for any file with an fsid that matches the fsid of the

two filehandles in question returns a unique_handles attribute

with a value of TRUE, then the two objects are distinct.

o If GETATTR directed to the two filehandles does not return the

fileid attribute for one or both of the handles, then the it

cannot be determined whether the two objects are the same.

Therefore, operations which depend on that knowledge (e.g. client

side data caching) cannot be done reliably.

o If GETATTR directed to the two filehandles returns different

values for the fileid attribute, then they are distinct objects.

o Otherwise they are the same object.

9.4. Open Delegation

When a file is being OPENed, the server may delegate further handling

of opens and closes for that file to the opening client. Any such

delegation is recallable, since the circumstances that allowed for

the delegation are subject to change. In particular, the server may

receive a conflicting OPEN from another client, the server must

recall the delegation before deciding whether the OPEN from the other

client may be granted. Making a delegation is up to the server and

clients should not assume that any particular OPEN either will or

will not result in an open delegation. The following is a typical

set of conditions that servers might use in deciding whether OPEN

should be delegated:

o The client must be able to respond to the server's callback

requests. The server will use the CB_NULL procedure for a test of

callback ability.

o The client must have responded properly to previous recalls.

o There must be no current open conflicting with the requested

delegation.

o There should be no current delegation that conflicts with the

delegation being requested.

o The probability of future conflicting open requests should be low

based on the recent history of the file.

o The existence of any server-specific semantics of OPEN/CLOSE that

would make the required handling incompatible with the prescribed

handling that the delegated client would apply (see below).

There are two types of open delegations, read and write. A read open

delegation allows a client to handle, on its own, requests to open a

file for reading that do not deny read access to others. Multiple

read open delegations may be outstanding simultaneously and do not

conflict. A write open delegation allows the client to handle, on

its own, all opens. Only one write open delegation may exist for a

given file at a given time and it is inconsistent with any read open

delegations.

When a client has a read open delegation, it may not make any changes

to the contents or attributes of the file but it is assured that no

other client may do so. When a client has a write open delegation,

it may modify the file data since no other client will be accessing

the file's data. The client holding a write delegation may only

affect file attributes which are intimately connected with the file

data: object_size, time_modify, change.

When a client has an open delegation, it does not send OPENs or

CLOSEs to the server but updates the appropriate status internally.

For a read open delegation, opens that cannot be handled locally

(opens for write or that deny read access) must be sent to the

server.

When an open delegation is made, the response to the OPEN contains an

open delegation structure which specifies the following:

o the type of delegation (read or write)

o space limitation information to control flushing of data on close

(write open delegation only, see the section "Open Delegation and

Data Caching")

o an nfsace4 specifying read and write permissions

o a stateid to represent the delegation for READ and WRITE

The stateid is separate and distinct from the stateid for the OPEN

proper. The standard stateid, unlike the delegation stateid, is

associated with a particular nfs_lockowner and will continue to be

valid after the delegation is recalled and the file remains open.

When a request internal to the client is made to open a file and open

delegation is in effect, it will be accepted or rejected solely on

the basis of the following conditions. Any requirement for other

checks to be made by the delegate should result in open delegation

being denied so that the checks can be made by the server itself.

o The access and deny bits for the request and the file as described

in the section "Share Reservations".

o The read and write permissions as determined below.

The nfsace4 passed with delegation can be used to avoid frequent

ACCESS calls. The permission check should be as follows:

o If the nfsace4 indicates that the open may be done, then it should

be granted without reference to the server.

o If the nfsace4 indicates that the open may not be done, then an

ACCESS request must be sent to the server to obtain the definitive

answer.

The server may return an nfsace4 that is more restrictive than the

actual ACL of the file. This includes an nfsace4 that specifies

denial of all access. Note that some common practices such as

mapping the traditional user "root" to the user "nobody" may make it

incorrect to return the actual ACL of the file in the delegation

response.

The use of delegation together with various other forms of caching

creates the possibility that no server authentication will ever be

performed for a given user since all of the user's requests might be

satisfied locally. Where the client is depending on the server for

authentication, the client should be sure authentication occurs for

each user by use of the ACCESS operation. This should be the case

even if an ACCESS operation would not be required otherwise. As

mentioned before, the server may enforce frequent authentication by

returning an nfsace4 denying all access with every open delegation.

9.4.1. Open Delegation and Data Caching

OPEN delegation allows much of the message overhead associated with

the opening and closing files to be eliminated. An open when an open

delegation is in effect does not require that a validation message be

sent to the server. The continued endurance of the "read open

delegation" provides a guarantee that no OPEN for write and thus no

write has occurred. Similarly, when closing a file opened for write

and if write open delegation is in effect, the data written does not

have to be flushed to the server until the open delegation is

recalled. The continued endurance of the open delegation provides a

guarantee that no open and thus no read or write has been done by

another client.

For the purposes of open delegation, READs and WRITEs done without an

OPEN are treated as the functional equivalents of a corresponding

type of OPEN. This refers to the READs and WRITEs that use the

special stateids consisting of all zero bits or all one bits.

Therefore, READs or WRITEs with a special stateid done by another

client will force the server to recall a write open delegation. A

WRITE with a special stateid done by another client will force a

recall of read open delegations.

With delegations, a client is able to avoid writing data to the

server when the CLOSE of a file is serviced. The CLOSE operation is

the usual point at which the client is notified of a lack of stable

storage for the modified file data generated by the application. At

the CLOSE, file data is written to the server and through normal

accounting the server is able to determine if the available file

system space for the data has been exceeded (i.e. server returns

NFS4ERR_NOSPC or NFS4ERR_DQUOT). This accounting includes quotas.

The introduction of delegations requires that a alternative method be

in place for the same type of communication to occur between client

and server.

In the delegation response, the server provides either the limit of

the size of the file or the number of modified blocks and associated

block size. The server must ensure that the client will be able to

flush data to the server of a size equal to that provided in the

original delegation. The server must make this assurance for all

outstanding delegations. Therefore, the server must be careful in

its management of available space for new or modified data taking

into account available file system space and any applicable quotas.

The server can recall delegations as a result of managing the

available file system space. The client should abide by the server's

state space limits for delegations. If the client exceeds the stated

limits for the delegation, the server's behavior is undefined.

Based on server conditions, quotas or available file system space,

the server may grant write open delegations with very restrictive

space limitations. The limitations may be defined in a way that will

always force modified data to be flushed to the server on close.

With respect to authentication, flushing modified data to the server

after a CLOSE has occurred may be problematic. For example, the user

of the application may have logged off of the client and unexpired

authentication credentials may not be present. In this case, the

client may need to take special care to ensure that local unexpired

credentials will in fact be available. This may be accomplished by

tracking the expiration time of credentials and flushing data well in

advance of their expiration or by making private copies of

credentials to assure their availability when needed.

9.4.2. Open Delegation and File Locks

When a client holds a write open delegation, lock operations are

performed locally. This includes those required for mandatory file

locking. This can be done since the delegation implies that there

can be no conflicting locks. Similarly, all of the revalidations

that would normally be associated with obtaining locks and the

flushing of data associated with the releasing of locks need not be

done.

9.4.3. Recall of Open Delegation

The following events necessitate recall of an open delegation:

o Potentially conflicting OPEN request (or READ/WRITE done with

"special" stateid)

o SETATTR issued by another client

o REMOVE request for the file

o RENAME request for the file as either source or target of the

RENAME

Whether a RENAME of a directory in the path leading to the file

results in recall of an open delegation depends on the semantics of

the server file system. If that file system denies such RENAMEs when

a file is open, the recall must be performed to determine whether the

file in question is, in fact, open.

In addition to the situations above, the server may choose to recall

open delegations at any time if resource constraints make it

advisable to do so. Clients should always be prepared for the

possibility of recall.

The server needs to employ special handling for a GETATTR where the

target is a file that has a write open delegation in effect. In this

case, the client holding the delegation needs to be interrogated.

The server will use a CB_GETATTR callback, if the GETATTR attribute

bits include any of the attributes that a write open delegate may

modify (object_size, time_modify, change).

When a client receives a recall for an open delegation, it needs to

update state on the server before returning the delegation. These

same updates must be done whenever a client chooses to return a

delegation voluntarily. The following items of state need to be

dealt with:

o If the file associated with the delegation is no longer open and

no previous CLOSE operation has been sent to the server, a CLOSE

operation must be sent to the server.

o If a file has other open references at the client, then OPEN

operations must be sent to the server. The appropriate stateids

will be provided by the server for subsequent use by the client

since the delegation stateid will not longer be valid. These OPEN

requests are done with the claim type of CLAIM_DELEGATE_CUR. This

will allow the presentation of the delegation stateid so that the

client can establish the appropriate rights to perform the OPEN.

(see the section "Operation 18: OPEN" for details.)

o If there are granted file locks, the corresponding LOCK operations

need to be performed. This applies to the write open delegation

case only.

o For a write open delegation, if at the time of recall the file is

not open for write, all modified data for the file must be flushed

to the server. If the delegation had not existed, the client

would have done this data flush before the CLOSE operation.

o For a write open delegation when a file is still open at the time

of recall, any modified data for the file needs to be flushed to

the server.

o With the write open delegation in place, it is possible that the

file was truncated during the duration of the delegation. For

example, the truncation could have occurred as a result of an OPEN

UNCHECKED with a object_size attribute value of zero. Therefore,

if a truncation of the file has occurred and this operation has

not been propagated to the server, the truncation must occur

before any modified data is written to the server.

In the case of write open delegation, file locking imposes some

additional requirements. The flushing of any modified data in any

region for which a write lock was released while the write open

delegation was in effect is what is required to precisely maintain

the associated invariant. However, because the write open delegation

implies no other locking by other clients, a simpler implementation

is to flush all modified data for the file (as described just above)

if any write lock has been released while the write open delegation

was in effect.

9.4.4. Delegation Revocation

At the point a delegation is revoked, if there are associated opens

on the client, the applications holding these opens need to be

notified. This notification usually occurs by returning errors for

READ/WRITE operations or when a close is attempted for the open file.

If no opens exist for the file at the point the delegation is

revoked, then notification of the revocation is unnecessary.

However, if there is modified data present at the client for the

file, the user of the application should be notified. Unfortunately,

it may not be possible to notify the user since active applications

may not be present at the client. See the section "Revocation

Recovery for Write Open Delegation" for additional details.

9.5. Data Caching and Revocation

When locks and delegations are revoked, the assumptions upon which

successful caching depend are no longer guaranteed. The owner of the

locks or share reservations which have been revoked needs to be

notified. This notification includes applications with a file open

that has a corresponding delegation which has been revoked. Cached

data associated with the revocation must be removed from the client.

In the case of modified data existing in the client's cache, that

data must be removed from the client without it being written to the

server. As mentioned, the assumptions made by the client are no

longer valid at the point when a lock or delegation has been revoked.

For example, another client may have been granted a conflicting lock

after the revocation of the lock at the first client. Therefore, the

data within the lock range may have been modified by the other

client. Obviously, the first client is unable to guarantee to the

application what has occurred to the file in the case of revocation.

Notification to a lock owner will in many cases consist of simply

returning an error on the next and all subsequent READs/WRITEs to the

open file or on the close. Where the methods available to a client

make such notification impossible because errors for certain

operations may not be returned, more drastic action such as signals

or process termination may be appropriate. The justification for

this is that an invariant for which an application depends on may be

violated. Depending on how errors are typically treated for the

client operating environment, further levels of notification

including logging, console messages, and GUI pop-ups may be

appropriate.

9.5.1. Revocation Recovery for Write Open Delegation

Revocation recovery for a write open delegation poses the special

issue of modified data in the client cache while the file is not

open. In this situation, any client which does not flush modified

data to the server on each close must ensure that the user receives

appropriate notification of the failure as a result of the

revocation. Since such situations may require human action to

correct problems, notification schemes in which the appropriate user

or administrator is notified may be necessary. Logging and console

messages are typical examples.

If there is modified data on the client, it must not be flushed

normally to the server. A client may attempt to provide a copy of

the file data as modified during the delegation under a different

name in the file system name space to ease recovery. Unless the

client can determine that the file has not modified by any other

client, this technique must be limited to situations in which a

client has a complete cached copy of the file in question. Use of

such a technique may be limited to files under a certain size or may

only be used when sufficient disk space is guaranteed to be available

within the target file system and when the client has sufficient

buffering resources to keep the cached copy available until it is

properly stored to the target file system.

9.6. Attribute Caching

The attributes discussed in this section do not include named

attributes. Individual named attributes are analogous to files and

caching of the data for these needs to be handled just as data

caching is for ordinary files. Similarly, LOOKUP results from an

OPENATTR directory are to be cached on the same basis as any other

pathnames and similarly for directory contents.

Clients may cache file attributes obtained from the server and use

them to avoid subsequent GETATTR requests. Such caching is write

through in that modification to file attributes is always done by

means of requests to the server and should not be done locally and

cached. The exception to this are modifications to attributes that

are intimately connected with data caching. Therefore, extending a

file by writing data to the local data cache is reflected immediately

in the object_size as seen on the client without this change being

immediately reflected on the server. Normally such changes are not

propagated directly to the server but when the modified data is

flushed to the server, analogous attribute changes are made on the

server. When open delegation is in effect, the modified attributes

may be returned to the server in the response to a CB_RECALL call.

The result of local caching of attributes is that the attribute

caches maintained on individual clients will not be coherent. Changes

made in one order on the server may be seen in a different order on

one client and in a third order on a different client.

The typical file system application programming interfaces do not

provide means to atomically modify or interrogate attributes for

multiple files at the same time. The following rules provide an

environment where the potential incoherences mentioned above can be

reasonably managed. These rules are derived from the practice of

previous NFS protocols.

o All attributes for a given file (per-fsid attributes excepted) are

cached as a unit at the client so that no non-serializability can

arise within the context of a single file.

o An upper time boundary is maintained on how long a client cache

entry can be kept without being refreshed from the server.

o When operations are performed that change attributes at the

server, the updated attribute set is requested as part of the

containing RPC. This includes directory operations that update

attributes indirectly. This is accomplished by following the

modifying operation with a GETATTR operation and then using the

results of the GETATTR to update the client's cached attributes.

Note that if the full set of attributes to be cached is requested by

READDIR, the results can be cached by the client on the same basis as

attributes obtained via GETATTR.

A client may validate its cached version of attributes for a file by

fetching only the change attribute and assuming that if the change

attribute has the same value as it did when the attributes were

cached, then no attributes have changed. The possible exception is

the attribute time_access.

9.7. Name Caching

The results of LOOKUP and READDIR operations may be cached to avoid

the cost of subsequent LOOKUP operations. Just as in the case of

attribute caching, inconsistencies may arise among the various client

caches. To mitigate the effects of these inconsistencies and given

the context of typical file system APIs, the following rules should

be followed:

o The results of unsuccessful LOOKUPs should not be cached, unless

they are specifically reverified at the point of use.

o An upper time boundary is maintained on how long a client name

cache entry can be kept without verifying that the entry has not

been made invalid by a directory change operation performed by

another client.

When a client is not making changes to a directory for which there

exist name cache entries, the client needs to periodically fetch

attributes for that directory to ensure that it is not being

modified. After determining that no modification has occurred, the

expiration time for the associated name cache entries may be updated

to be the current time plus the name cache staleness bound.

When a client is making changes to a given directory, it needs to

determine whether there have been changes made to the directory by

other clients. It does this by using the change attribute as

reported before and after the directory operation in the associated

change_info4 value returned for the operation. The server is able to

communicate to the client whether the change_info4 data is provided

atomically with respect to the directory operation. If the change

values are provided atomically, the client is then able to compare

the pre-operation change value with the change value in the client's

name cache. If the comparison indicates that the directory was

updated by another client, the name cache associated with the

modified directory is purged from the client. If the comparison

indicates no modification, the name cache can be updated on the

client to reflect the directory operation and the associated timeout

extended. The post-operation change value needs to be saved as the

basis for future change_info4 comparisons.

As demonstrated by the scenario above, name caching requires that the

client revalidate name cache data by inspecting the change attribute

of a directory at the point when the name cache item was cached.

This requires that the server update the change attribute for

directories when the contents of the corresponding directory is

modified. For a client to use the change_info4 information

appropriately and correctly, the server must report the pre and post

operation change attribute values atomically. When the server is

unable to report the before and after values atomically with respect

to the directory operation, the server must indicate that fact in the

change_info4 return value. When the information is not atomically

reported, the client should not assume that other clients have not

changed the directory.

9.8. Directory Caching

The results of READDIR operations may be used to avoid subsequent

READDIR operations. Just as in the cases of attribute and name

caching, inconsistencies may arise among the various client caches.

To mitigate the effects of these inconsistencies, and given the

context of typical file system APIs, the following rules should be

followed:

o Cached READDIR information for a directory which is not obtained

in a single READDIR operation must always be a consistent snapshot

of directory contents. This is determined by using a GETATTR

before the first READDIR and after the last of READDIR that

contributes to the cache.

o An upper time boundary is maintained to indicate the length of

time a directory cache entry is considered valid before the client

must revalidate the cached information.

The revalidation technique parallels that discussed in the case of

name caching. When the client is not changing the directory in

question, checking the change attribute of the directory with GETATTR

is adequate. The lifetime of the cache entry can be extended at

these checkpoints. When a client is modifying the directory, the

client needs to use the change_info4 data to determine whether there

are other clients modifying the directory. If it is determined that

no other client modifications are occurring, the client may update

its directory cache to reflect its own changes.

As demonstrated previously, directory caching requires that the

client revalidate directory cache data by inspecting the change

attribute of a directory at the point when the directory was cached.

This requires that the server update the change attribute for

directories when the contents of the corresponding directory is

modified. For a client to use the change_info4 information

appropriately and correctly, the server must report the pre and post

operation change attribute values atomically. When the server is

unable to report the before and after values atomically with respect

to the directory operation, the server must indicate that fact in the

change_info4 return value. When the information is not atomically

reported, the client should not assume that other clients have not

changed the directory.

10. Minor Versioning

To address the requirement of an NFS protocol that can evolve as the

need arises, the NFS version 4 protocol contains the rules and

framework to allow for future minor changes or versioning.

The base assumption with respect to minor versioning is that any

future accepted minor version must follow the IETF process and be

documented in a standards track RFC. Therefore, each minor version

number will correspond to an RFC. Minor version zero of the NFS

version 4 protocol is represented by this RFC. The COMPOUND

procedure will support the encoding of the minor version being

requested by the client.

The following items represent the basic rules for the development of

minor versions. Note that a future minor version may decide to

modify or add to the following rules as part of the minor version

definition.

1 Procedures are not added or deleted

To maintain the general RPC model, NFS version 4 minor versions

will not add or delete procedures from the NFS program.

2 Minor versions may add operations to the COMPOUND and

CB_COMPOUND procedures.

The addition of operations to the COMPOUND and CB_COMPOUND

procedures does not affect the RPC model.

2.1 Minor versions may append attributes to GETATTR4args, bitmap4,

and GETATTR4res.

This allows for the expansion of the attribute model to allow

for future growth or adaptation.

2.2 Minor version X must append any new attributes after the last

documented attribute.

Since attribute results are specified as an opaque array of

per-attribute XDR encoded results, the complexity of adding new

attributes in the midst of the current definitions will be too

burdensome.

3 Minor versions must not modify the structure of an existing

operation's arguments or results.

Again the complexity of handling multiple structure definitions

for a single operation is too burdensome. New operations should

be added instead of modifying existing structures for a minor

version.

This rule does not preclude the following adaptations in a minor

version.

o adding bits to flag fields such as new attributes to

GETATTR's bitmap4 data type

o adding bits to existing attributes like ACLs that have flag

words

o extending enumerated types (including NFS4ERR_*) with new

values

4 Minor versions may not modify the structure of existing

attributes.

5 Minor versions may not delete operations.

This prevents the potential reuse of a particular operation

"slot" in a future minor version.

6 Minor versions may not delete attributes.

7 Minor versions may not delete flag bits or enumeration values.

8 Minor versions may declare an operation as mandatory to NOT

implement.

Specifying an operation as "mandatory to not implement" is

equivalent to obsoleting an operation. For the client, it means

that the operation should not be sent to the server. For the

server, an NFS error can be returned as opposed to "dropping"

the request as an XDR decode error. This approach allows for

the obsolescence of an operation while maintaining its structure

so that a future minor version can reintroduce the operation.

8.1 Minor versions may declare attributes mandatory to NOT

implement.

8.2 Minor versions may declare flag bits or enumeration values as

mandatory to NOT implement.

9 Minor versions may downgrade features from mandatory to

recommended, or recommended to optional.

10 Minor versions may upgrade features from optional to recommended

or recommended to mandatory.

11 A client and server that support minor version X must support

minor versions 0 (zero) through X-1 as well.

12 No new features may be introduced as mandatory in a minor

version.

This rule allows for the introduction of new functionality and

forces the use of implementation experience before designating a

feature as mandatory.

13 A client MUST NOT attempt to use a stateid, file handle, or

similar returned object from the COMPOUND procedure with minor

version X for another COMPOUND procedure with minor version Y,

where X != Y.

11. Internationalization

The primary issue in which NFS needs to deal with

internationalization, or I18n, is with respect to file names and

other strings as used within the protocol. The choice of string

representation must allow reasonable name/string access to clients

which use various languages. The UTF-8 encoding of the UCS as

defined by [ISO10646] allows for this type of access and follows the

policy described in "IETF Policy on Character Sets and Languages",

[RFC2277]. This choice is explained further in the following.

11.1. Universal Versus Local Character Sets

[RFC1345] describes a table of 16 bit characters for many different

languages (the bit encodings match Unicode, though of course RFC1345

is somewhat out of date with respect to current Unicode assignments).

Each character from each language has a unique 16 bit value in the 16

bit character set. Thus this table can be thought of as a universal

character set. [RFC1345] then talks about groupings of subsets of

the entire 16 bit character set into "Charset Tables". For example

one might take all the Greek characters from the 16 bit table (which

are consecutively allocated), and normalize their offsets to a table

that fits in 7 bits. Thus it is determined that "lower case alpha"

is in the same position as "upper case a" in the US-ASCII table, and

"upper case alpha" is in the same position as "lower case a" in the

US-ASCII table.

These normalized subset character sets can be thought of as "local

character sets", suitable for an operating system locale.

Local character sets are not suitable for the NFS protocol. Consider

someone who creates a file with a name in a Swedish character set.

If someone else later goes to access the file with their locale set

to the Swedish language, then there are no problems. But if someone

in say the US-ASCII locale goes to access the file, the file name

will look very different, because the Swedish characters in the 7 bit

table will now be represented in US-ASCII characters on the display.

It would be preferable to give the US-ASCII user a way to display the

file name using Swedish glyphs. In order to do that, the NFS protocol

would have to include the locale with the file name on each operation

to create a file.

But then what of the situation when there is a path name on the

server like:

/component-1/component-2/component-3

Each component could have been created with a different locale. If

one issues CREATE with multi-component path name, and if some of the

leading components already exist, what is to be done with the

existing components? Is the current locale attribute replaced with

the user's current one? These types of situations quickly become too

complex when there is an alternate solution.

If the NFS version 4 protocol used a universal 16 bit or 32 bit

character set (or an encoding of a 16 bit or 32 bit character set

into octets), then the server and client need not care if the locale

of the user accessing the file is different than the locale of the

user who created the file. The unique 16 bit or 32 bit encoding of

the character allows for determination of what language the character

is from and also how to display that character on the client. The

server need not know what locales are used.

11.2. Overview of Universal Character Set Standards

The previous section makes a case for using a universal character

set. This section makes the case for using UTF-8 as the specific

universal character set for the NFS version 4 protocol.

[RFC2279] discusses UTF-* (UTF-8 and other UTF-XXX encodings),

Unicode, and UCS-*. There are two standards bodies managing

universal code sets:

o ISO/IEC which has the standard 10646-1

o Unicode which has the Unicode standard

Both standards bodies have pledged to track each other's assignments

of character codes.

The following is a brief analysis of the various standards.

UCS Universal Character Set. This is ISO/IEC 10646-1: "a

multi-octet character set called the Universal Character

Set (UCS), which encompasses most of the world's writing

systems."

UCS-2 a two octet per character encoding that addresses the first

2^16 characters of UCS. Currently there are no UCS

characters beyond that range.

UCS-4 a four octet per character encoding that permits the

encoding of up to 2^31 characters.

UTF UTF is an abbreviation of the term "UCS transformation

format" and is used in the naming of various standards for

encoding of UCS characters as described below.

UTF-1 Only historical interest; it has been removed from 10646-1

UTF-7 Encodes the entire "repertoire" of UCS "characters using

only octets with the higher order bit clear". [RFC2152]

describes UTF-7. UTF-7 accomplishes this by reserving one

of the 7bit US-ASCII characters as a "shift" character to

indicate non-US-ASCII characters.

UTF-8 Unlike UTF-7, uses all 8 bits of the octets. US-ASCII

characters are encoded as before unchanged. Any octet with

the high bit cleared can only mean a US-ASCII character.

The high bit set means that a UCS character is being

encoded.

UTF-16 Encodes UCS-4 characters into UCS-2 characters using a

reserved range in UCS-2.

Unicode Unicode and UCS-2 are the same; [RFC2279] states:

Up to the present time, changes in Unicode and amendments

to ISO/IEC 10646 have tracked each other, so that the

character repertoires and code point assignments have

remained in sync. The relevant standardization committees

have committed to maintain this very useful synchronism.

11.3. Difficulties with UCS-4, UCS-2, Unicode

Adapting existing applications, and file systems to multi-octet

schemes like UCS and Unicode can be difficult. A significant amount

of code has been written to process streams of bytes. Also there are

many existing stored objects described with 7 bit or 8 bit

characters. Doubling or quadrupling the bandwidth and storage

requirements seems like an expensive way to accomplish I18N.

UCS-2 and Unicode are "only" 16 bits long. That might seem to be

enough but, according to [Unicode1], 49,194 Unicode characters are

already assigned. According to [Unicode2] there are still more

languages that need to be added.

11.4. UTF-8 and its solutions

UTF-8 solves problems for NFS that exist with the use of UCS and

Unicode. UTF-8 will encode 16 bit and 32 bit characters in a way

that will be compact for most users. The encoding table from UCS-4 to

UTF-8, as copied from [RFC2279]:

UCS-4 range (hex.) UTF-8 octet sequence (binary)

0000 0000-0000 007F 0xxxxxxx

0000 0080-0000 07FF 110xxxxx 10xxxxxx

0000 0800-0000 FFFF 1110xxxx 10xxxxxx 10xxxxxx

0001 0000-001F FFFF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

0020 0000-03FF FFFF 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx

0400 0000-7FFF FFFF 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx

10xxxxxx

See [RFC2279] for precise encoding and decoding rules. Note because

of UTF-16, the algorithm from Unicode/UCS-2 to UTF-8 needs to account

for the reserved range between D800 and DFFF.

Note that the 16 bit UCS or Unicode characters require no more than 3

octets to encode into UTF-8

Interestingly, UTF-8 has room to handle characters larger than 31

bits, because the leading octet of form:

1111111x

is not defined. If needed, ISO could either use that octet to

indicate a sequence of an encoded 8 octet character, or perhaps use

11111110 to permit the next octet to indicate an even more expandable

character set.

So using UTF-8 to represent character encodings means never having to

run out of room.

11.5. Normalization

The client and server operating environments may differ in their

policies and operational methods with respect to character

normalization (See [Unicode1] for a discussion of normalization

forms). This difference may also exist between applications on the

same client. This adds to the difficulty of providing a single

normalization policy for the protocol that allows for maximal

interoperability. This issue is similar to the character case issues

where the server may or may not support case insensitive file name

matching and may or may not preserve the character case when storing

file names. The protocol does not mandate a particular behavior but

allows for the various permutations.

The NFS version 4 protocol does not mandate the use of a particular

normalization form at this time. A later revision of this

specification may specify a particular normalization form.

Therefore, the server and client can expect that they may receive

unnormalized characters within protocol requests and responses. If

the operating environment requires normalization, then the

implementation must normalize the various UTF-8 encoded strings

within the protocol before presenting the information to an

application (at the client) or local file system (at the server).

12. Error Definitions

NFS error numbers are assigned to failed operations within a compound

request. A compound request contains a number of NFS operations that

have their results encoded in sequence in a compound reply. The

results of successful operations will consist of an NFS4_OK status

followed by the encoded results of the operation. If an NFS

operation fails, an error status will be entered in the reply and the

compound request will be terminated.

A description of each defined error follows:

NFS4_OK Indicates the operation completed successfully.

NFS4ERR_ACCES Permission denied. The caller does not have the

correct permission to perform the requested

operation. Contrast this with NFS4ERR_PERM,

which restricts itself to owner or privileged

user permission failures.

NFS4ERR_BADHANDLE Illegal NFS file handle. The file handle failed

internal consistency checks.

NFS4ERR_BADTYPE An attempt was made to create an object of a

type not supported by the server.

NFS4ERR_BAD_COOKIE READDIR cookie is stale.

NFS4ERR_BAD_SEQID The sequence number in a locking request is

neither the next expected number or the last

number processed.

NFS4ERR_BAD_STATEID A stateid generated by the current server

instance, but which does not designate any

locking state (either current or superseded)

for a current lockowner-file pair, was used.

NFS4ERR_CLID_INUSE The SETCLIENTID procedure has found that a

client id is already in use by another client.

NFS4ERR_DELAY The server initiated the request, but was not

able to complete it in a timely fashion. The

client should wait and then try the request

with a new RPC transaction ID. For example,

this error should be returned from a server

that supports hierarchical storage and receives

a request to process a file that has been

migrated. In this case, the server should start

the immigration process and respond to client

with this error. This error may also occur

when a necessary delegation recall makes

processing a request in a timely fashion

impossible.

NFS4ERR_DENIED An attempt to lock a file is denied. Since

this may be a temporary condition, the client

is encouraged to retry the lock request until

the lock is accepted.

NFS4ERR_DQUOT Resource (quota) hard limit exceeded. The

user's resource limit on the server has been

exceeded.

NFS4ERR_EXIST File exists. The file specified already exists.

NFS4ERR_EXPIRED A lease has expired that is being used in the

current procedure.

NFS4ERR_FBIG File too large. The operation would have caused

a file to grow beyond the server's limit.

NFS4ERR_FHEXPIRED The file handle provided is volatile and has

expired at the server.

NFS4ERR_GRACE The server is in its recovery or grace period

which should match the lease period of the

server.

NFS4ERR_INVAL Invalid argument or unsupported argument for an

operation. Two examples are attempting a

READLINK on an object other than a symbolic

link or attempting to SETATTR a time field on a

server that does not support this operation.

NFS4ERR_IO I/O error. A hard error (for example, a disk

error) occurred while processing the requested

operation.

NFS4ERR_ISDIR Is a directory. The caller specified a

directory in a non-directory operation.

NFS4ERR_LEASE_MOVED A lease being renewed is associated with a file

system that has been migrated to a new server.

NFS4ERR_LOCKED A read or write operation was attempted on a

locked file.

NFS4ERR_LOCK_RANGE A lock request is operating on a sub-range of a

current lock for the lock owner and the server

does not support this type of request.

NFS4ERR_MINOR_VERS_MISMATCH

The server has received a request that

specifies an unsupported minor version. The

server must return a COMPOUND4res with a zero

length operations result array.

NFS4ERR_MLINK Too many hard links.

NFS4ERR_MOVED The filesystem which contains the current

filehandle object has been relocated or

migrated to another server. The client may

obtain the new filesystem location by obtaining

the "fs_locations" attribute for the current

filehandle. For further discussion, refer to

the section "Filesystem Migration or

Relocation".

NFS4ERR_NAMETOOLONG The filename in an operation was too long.

NFS4ERR_NODEV No such device.

NFS4ERR_NOENT No such file or directory. The file or

directory name specified does not exist.

NFS4ERR_NOFILEHANDLE The logical current file handle value has not

been set properly. This may be a result of a

malformed COMPOUND operation (i.e. no PUTFH or

PUTROOTFH before an operation that requires the

current file handle be set).

NFS4ERR_NOSPC No space left on device. The operation would

have caused the server's file system to exceed

its limit.

NFS4ERR_NOTDIR Not a directory. The caller specified a non-

directory in a directory operation.

NFS4ERR_NOTEMPTY An attempt was made to remove a directory that

was not empty.

NFS4ERR_NOTSUPP Operation is not supported.

NFS4ERR_NOT_SAME This error is returned by the VERIFY operation

to signify that the attributes compared were

not the same as provided in the client's

request.

NFS4ERR_NXIO I/O error. No such device or address.

NFS4ERR_OLD_STATEID A stateid which designates the locking state

for a lockowner-file at an earlier time was

used.

NFS4ERR_PERM Not owner. The operation was not allowed

because the caller is either not a privileged

user (root) or not the owner of the target of

the operation.

NFS4ERR_READDIR_NOSPC The encoded response to a READDIR request

exceeds the size limit set by the initial

request.

NFS4ERR_RESOURCE For the processing of the COMPOUND procedure,

the server may exhaust available resources and

can not continue processing procedures within

the COMPOUND operation. This error will be

returned from the server in those instances of

resource exhaustion related to the processing

of the COMPOUND procedure.

NFS4ERR_ROFS Read-only file system. A modifying operation

was attempted on a read-only file system.

NFS4ERR_SAME This error is returned by the NVERIFY operation

to signify that the attributes compared were

the same as provided in the client's request.

NFS4ERR_SERVERFAULT An error occurred on the server which does not

map to any of the legal NFS version 4 protocol

error values. The client should translate this

into an appropriate error. UNIX clients may

choose to translate this to EIO.

NFS4ERR_SHARE_DENIED An attempt to OPEN a file with a share

reservation has failed because of a share

conflict.

NFS4ERR_STALE Invalid file handle. The file handle given in

the arguments was invalid. The file referred to

by that file handle no longer exists or access

to it has been revoked.

NFS4ERR_STALE_CLIENTID A clientid not recognized by the server was

used in a locking or SETCLIENTID_CONFIRM

request.

NFS4ERR_STALE_STATEID A stateid generated by an earlier server

instance was used.

NFS4ERR_SYMLINK The current file handle provided for a LOOKUP

is not a directory but a symbolic link. Also

used if the final component of the OPEN path is

a symbolic link.

NFS4ERR_TOOSMALL Buffer or request is too

small.

NFS4ERR_WRONGSEC The security mechanism being used by the client

for the procedure does not match the server's

security policy. The client should change the

security mechanism being used and retry the

operation.

NFS4ERR_XDEV Attempt to do a cross-device hard link.

13. NFS Version 4 Requests

For the NFS version 4 RPC program, there are two traditional RPC

procedures: NULL and COMPOUND. All other functionality is defined as

a set of operations and these operations are defined in normal

XDR/RPC syntax and semantics. However, these operations are

encapsulated within the COMPOUND procedure. This requires that the

client combine one or more of the NFS version 4 operations into a

single request.

The NFS4_CALLBACK program is used to provide server to client

signaling and is constructed in a similar fashion as the NFS version

4 program. The procedures CB_NULL and CB_COMPOUND are defined in the

same way as NULL and COMPOUND are within the NFS program. The

CB_COMPOUND request also encapsulates the remaining operations of the

NFS4_CALLBACK program. There is no predefined RPC program number for

the NFS4_CALLBACK program. It is up to the client to specify a

program number in the "transient" program range. The program and

port number of the NFS4_CALLBACK program are provided by the client

as part of the SETCLIENTID operation and therefore is fixed for the

life of the client instantiation.

13.1. Compound Procedure

The COMPOUND procedure provides the opportunity for better

performance within high latency networks. The client can avoid

cumulative latency of multiple RPCs by combining multiple dependent

operations into a single COMPOUND procedure. A compound operation

may provide for protocol simplification by allowing the client to

combine basic procedures into a single request that is customized for

the client's environment.

The CB_COMPOUND procedure precisely parallels the features of

COMPOUND as described above.

The basics of the COMPOUND procedures construction is:

+-----------+-----------+-----------+--

op + args op + args op + args

+-----------+-----------+-----------+--

and the reply looks like this:

+------------+-----------------------+-----------------------+--

last status status + op + results status + op + results

+------------+-----------------------+-----------------------+--

13.2. Evaluation of a Compound Request

The server will process the COMPOUND procedure by evaluating each of

the operations within the COMPOUND procedure in order. Each

component operation consists of a 32 bit operation code, followed by

the argument of length determined by the type of operation. The

results of each operation are encoded in sequence into a reply

buffer. The results of each operation are preceded by the opcode and

a status code (normally zero). If an operation results in a non-zero

status code, the status will be encoded and evaluation of the

compound sequence will halt and the reply will be returned. Note

that evaluation stops even in the event of "non error" conditions

such as NFS4ERR_SAME.

There are no atomicity requirements for the operations contained

within the COMPOUND procedure. The operations being evaluated as

part of a COMPOUND request may be evaluated simultaneously with other

COMPOUND requests that the server receives.

It is the client's responsibility for recovering from any partially

completed COMPOUND procedure. Partially completed COMPOUND

procedures may occur at any point due to errors such as

NFS4ERR_RESOURCE and NFS4ERR_LONG_DELAY. This may occur even given

an otherwise valid operation string. Further, a server reboot which

occurs in the middle of processing a COMPOUND procedure may leave the

client with the difficult task of determining how far COMPOUND

processing has proceeded. Therefore, the client should avoid overly

complex COMPOUND procedures in the event of the failure of an

operation within the procedure.

Each operation assumes a "current" and "saved" filehandle that is

available as part of the execution context of the compound request.

Operations may set, change, or return the current filehandle. The

"saved" filehandle is used for temporary storage of a filehandle

value and as operands for the RENAME and LINK operations.

13.3. Synchronous Modifying Operations

NFS version 4 operations that modify the file system are synchronous.

When an operation is successfully completed at the server, the client

can depend that any data associated with the request is now on stable

storage (the one exception is in the case of the file data in a WRITE

operation with the UNSTABLE option specified).

This implies that any previous operations within the same compound

request are also reflected in stable storage. This behavior enables

the client's ability to recover from a partially executed compound

request which may resulted from the failure of the server. For

example, if a compound request contains operations A and B and the

server is unable to send a response to the client, depending on the

progress the server made in servicing the request the result of both

operations may be reflected in stable storage or just operation A may

be reflected. The server must not have just the results of operation

B in stable storage.

13.4. Operation Values

The operations encoded in the COMPOUND procedure are identified by

operation values. To avoid overlap with the RPC procedure numbers,

operations 0 (zero) and 1 are not defined. Operation 2 is not

defined but reserved for future use with minor versioning.

14. NFS Version 4 Procedures

14.1. Procedure 0: NULL - No Operation

SYNOPSIS

<null>

ARGUMENT

void;

RESULT

void;

DESCRIPTION

Standard NULL procedure. Void argument, void response. This

procedure has no functionality associated with it. Because of

this it is sometimes used to measure the overhead of processing a

service request. Therefore, the server should ensure that no

unnecessary work is done in servicing this procedure.

ERRORS

None.

14.2. Procedure 1: COMPOUND - Compound Operations

SYNOPSIS

compoundargs -> compoundres

ARGUMENT

union nfs_argop4 switch (nfs_opnum4 argop) {

case <OPCODE>: <argument>;

...

};

struct COMPOUND4args {

utf8string tag;

uint32_t minorversion;

nfs_argop4 argarray<>;

};

RESULT

union nfs_resop4 switch (nfs_opnum4 resop){

case <OPCODE>: <result>;

...

};

struct COMPOUND4res {

nfsstat4 status;

utf8string tag;

nfs_resop4 resarray<>;

};

DESCRIPTION

The COMPOUND procedure is used to combine one or more of the NFS

operations into a single RPC request. The main NFS RPC program

has two main procedures: NULL and COMPOUND. All other operations

use the COMPOUND procedure as a wrapper.

The COMPOUND procedure is used to combine individual operations

into a single RPC request. The server interprets each of the

operations in turn. If an operation is executed by the server and

the status of that operation is NFS4_OK, then the next operation

in the COMPOUND procedure is executed. The server continues this

process until there are no more operations to be executed or one

of the operations has a status value other than NFS4_OK.

In the processing of the COMPOUND procedure, the server may find

that it does not have the available resources to execute any or

all of the operations within the COMPOUND sequence. In this case,

the error NFS4ERR_RESOURCE will be returned for the particular

operation within the COMPOUND procedure where the resource

exhaustion occurred. This assumes that all previous operations

within the COMPOUND sequence have been evaluated successfully.

The results for all of the evaluated operations must be returned

to the client.

The COMPOUND arguments contain a "minorversion" field. The

initial and default value for this field is 0 (zero). This field

will be used by future minor versions such that the client can

communicate to the server what minor version is being requested.

If the server receives a COMPOUND procedure with a minorversion

field value that it does not support, the server MUST return an

error of NFS4ERR_MINOR_VERS_MISMATCH and a zero length resultdata

array.

Contained within the COMPOUND results is a "status" field. If the

results array length is non-zero, this status must be equivalent

to the status of the last operation that was executed within the

COMPOUND procedure. Therefore, if an operation incurred an error

then the "status" value will be the same error value as is being

returned for the operation that failed.

Note that operations, 0 (zero) and 1 (one) are not defined for the

COMPOUND procedure. If the server receives an operation array

with either of these included, an error of NFS4ERR_NOTSUPP must be

returned. Operation 2 is not defined but reserved for future

definition and use with minor versioning. If the server receives

a operation array that contains operation 2 and the minorversion

field has a value of 0 (zero), an error of NFS4ERR_NOTSUPP is

returned. If an operation array contains an operation 2 and the

minorversion field is non-zero and the server does not support the

minor version, the server returns an error of

NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the

NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other

errors.

IMPLEMENTATION

Note that the definition of the "tag" in both the request and

response are left to the implementor. It may be used to summarize

the content of the compound request for the benefit of packet

sniffers and engineers debugging implementations.

Since an error of any type may occur after only a portion of the

operations have been evaluated, the client must be prepared to

recover from any failure. If the source of an NFS4ERR_RESOURCE

error was a complex or lengthy set of operations, it is likely

that if the number of operations were reduced the server would be

able to evaluate them successfully. Therefore, the client is

responsible for dealing with this type of complexity in recovery.

ERRORS

All errors defined in the protocol

14.2.1. Operation 3: ACCESS - Check Access Rights

SYNOPSIS

(cfh), accessreq -> supported, accessrights

ARGUMENT

const ACCESS4_READ = 0x00000001;

const ACCESS4_LOOKUP = 0x00000002;

const ACCESS4_MODIFY = 0x00000004;

const ACCESS4_EXTEND = 0x00000008;

const ACCESS4_DELETE = 0x00000010;

const ACCESS4_EXECUTE = 0x00000020;

struct ACCESS4args {

/* CURRENT_FH: object */

uint32_t access;

};

RESULT

struct ACCESS4resok {

uint32_t supported;

uint32_t access;

};

union ACCESS4res switch (nfsstat4 status) {

case NFS4_OK:

ACCESS4resok resok4;

default:

void;

};

DESCRIPTION

ACCESS determines the access rights that a user, as identified by

the credentials in the RPC request, has with respect to the file

system object specified by the current filehandle. The client

encodes the set of access rights that are to be checked in the bit

mask "access". The server checks the permissions encoded in the

bit mask. If a status of NFS4_OK is returned, two bit masks are

included in the response. The first, "supported", represents the

access rights for which the server can verify reliably. The

second, "access", represents the access rights available to the

user for the filehandle provided. On success, the current

filehandle retains its value.

Note that the supported field will contain only as many values as

was originally sent in the arguments. For example, if the client

sends an ACCESS operation with only the ACCESS4_READ value set and

the server supports this value, the server will return only

ACCESS4_READ even if it could have reliably checked other values.

The results of this operation are necessarily advisory in nature.

A return status of NFS4_OK and the appropriate bit set in the bit

mask does not imply that such access will be allowed to the file

system object in the future. This is because access rights can be

revoked by the server at any time.

The following access permissions may be requested:

ACCESS4_READ Read data from file or read a directory.

ACCESS4_LOOKUP Look up a name in a directory (no meaning for non-

directory objects).

ACCESS4_MODIFY Rewrite existing file data or modify existing

directory entries.

ACCESS4_EXTEND Write new data or add directory entries.

ACCESS4_DELETE Delete an existing directory entry (no meaning for

non-directory objects).

ACCESS4_EXECUTE Execute file (no meaning for a directory).

On success, the current filehandle retains its value.

IMPLEMENTATION

For the NFS version 4 protocol, the use of the ACCESS procedure

when opening a regular file is deprecated in favor of using OPEN.

In general, it is not sufficient for the client to attempt to

deduce access permissions by inspecting the uid, gid, and mode

fields in the file attributes or by attempting to interpret the

contents of the ACL attribute. This is because the server may

perform uid or gid mapping or enforce additional access control

restrictions. It is also possible that the server may not be in

the same ID space as the client. In these cases (and perhaps

others), the client can not reliably perform an access check with

only current file attributes.

In the NFS version 2 protocol, the only reliable way to determine

whether an operation was allowed was to try it and see if it

succeeded or failed. Using the ACCESS procedure in the NFS

version 4 protocol, the client can ask the server to indicate

whether or not one or more classes of operations are permitted.

The ACCESS operation is provided to allow clients to check before

doing a series of operations which will result in an access

failure. The OPEN operation provides a point where the server can

verify access to the file object and method to return that

information to the client. The ACCESS operation is still useful

for directory operations or for use in the case the UNIX API

"access" is used on the client.

The information returned by the server in response to an ACCESS

call is not permanent. It was correct at the exact time that the

server performed the checks, but not necessarily afterwards. The

server can revoke access permission at any time.

The client should use the effective credentials of the user to

build the authentication information in the ACCESS request used to

determine access rights. It is the effective user and group

credentials that are used in subsequent read and write operations.

Many implementations do not directly support the ACCESS4_DELETE

permission. Operating systems like UNIX will ignore the

ACCESS4_DELETE bit if set on an access request on a non-directory

object. In these systems, delete permission on a file is

determined by the access permissions on the directory in which the

file resides, instead of being determined by the permissions of

the file itself. Therefore, the mask returned enumerating which

access rights can be determined will have the ACCESS4_DELETE value

set to 0. This indicates to the client that the server was unable

to check that particular access right. The ACCESS4_DELETE bit in

the access mask returned will then be ignored by the client.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.2. Operation 4: CLOSE - Close File

SYNOPSIS

(cfh), seqid, stateid -> stateid

ARGUMENT

struct CLOSE4args {

/* CURRENT_FH: object */

seqid4 seqid

stateid4 stateid;

};

RESULT

union CLOSE4res switch (nfsstat4 status) {

case NFS4_OK:

stateid4 stateid;

default:

void;

};

DESCRIPTION

The CLOSE operation releases share reservations for the file as

specified by the current filehandle. The share reservations and

other state information released at the server as a result of this

CLOSE is only associated with the supplied stateid. The sequence

id provides for the correct ordering. State associated with other

OPENs is not affected.

If record locks are held, the client SHOULD release all locks

before issuing a CLOSE. The server MAY free all outstanding locks

on CLOSE but some servers may not support the CLOSE of a file that

still has record locks held. The server MUST return failure if

any locks would exist after the CLOSE.

On success, the current filehandle retains its value.

IMPLEMENTATION

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_BAD_SEQID

NFS4ERR_BAD_STATEID

NFS4ERR_DELAY

NFS4ERR_EXPIRED

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_ISDIR

NFS4ERR_LEASE_MOVED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_OLD_STATEID

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_STALE_STATEID

14.2.3. Operation 5: COMMIT - Commit Cached Data

SYNOPSIS

(cfh), offset, count -> verifier

ARGUMENT

struct COMMIT4args {

/* CURRENT_FH: file */

offset4 offset;

count4 count;

};

RESULT

struct COMMIT4resok {

verifier4 writeverf;

};

union COMMIT4res switch (nfsstat4 status) {

case NFS4_OK:

COMMIT4resok resok4;

default:

void;

};

DESCRIPTION

The COMMIT operation forces or flushes data to stable storage for

the file specified by the current file handle. The flushed data

is that which was previously written with a WRITE operation which

had the stable field set to UNSTABLE4.

The offset specifies the position within the file where the flush

is to begin. An offset value of 0 (zero) means to flush data

starting at the beginning of the file. The count specifies the

number of bytes of data to flush. If count is 0 (zero), a flush

from offset to the end of the file is done.

The server returns a write verifier upon successful completion of

the COMMIT. The write verifier is used by the client to determine

if the server has restarted or rebooted between the initial

WRITE(s) and the COMMIT. The client does this by comparing the

write verifier returned from the initial writes and the verifier

returned by the COMMIT procedure. The server must vary the value

of the write verifier at each server event or instantiation that

may lead to a loss of uncommitted data. Most commonly this occurs

when the server is rebooted; however, other events at the server

may result in uncommitted data loss as well.

On success, the current filehandle retains its value.

IMPLEMENTATION

The COMMIT procedure is similar in operation and semantics to the

POSIX fsync(2) system call that synchronizes a file's state with

the disk (file data and metadata is flushed to disk or stable

storage). COMMIT performs the same operation for a client,

flushing any unsynchronized data and metadata on the server to the

server's disk or stable storage for the specified file. Like

fsync(2), it may be that there is some modified data or no

modified data to synchronize. The data may have been synchronized

by the server's normal periodic buffer synchronization activity.

COMMIT should return NFS4_OK, unless there has been an unexpected

error.

COMMIT differs from fsync(2) in that it is possible for the client

to flush a range of the file (most likely triggered by a buffer-

reclamation scheme on the client before file has been completely

written).

The server implementation of COMMIT is reasonably simple. If the

server receives a full file COMMIT request, that is starting at

offset 0 and count 0, it should do the equivalent of fsync()'ing

the file. Otherwise, it should arrange to have the cached data in

the range specified by offset and count to be flushed to stable

storage. In both cases, any metadata associated with the file

must be flushed to stable storage before returning. It is not an

error for there to be nothing to flush on the server. This means

that the data and metadata that needed to be flushed have already

been flushed or lost during the last server failure.

The client implementation of COMMIT is a little more complex.

There are two reasons for wanting to commit a client buffer to

stable storage. The first is that the client wants to reuse a

buffer. In this case, the offset and count of the buffer are sent

to the server in the COMMIT request. The server then flushes any

cached data based on the offset and count, and flushes any

metadata associated with the file. It then returns the status of

the flush and the write verifier. The other reason for the client

to generate a COMMIT is for a full file flush, such as may be done

at close. In this case, the client would gather all of the

buffers for this file that contain uncommitted data, do the COMMIT

operation with an offset of 0 and count of 0, and then free all of

those buffers. Any other dirty buffers would be sent to the

server in the normal fashion.

After a buffer is written by the client with the stable parameter

set to UNSTABLE4, the buffer must be considered as modified by the

client until the buffer has either been flushed via a COMMIT

operation or written via a WRITE operation with stable parameter

set to FILE_SYNC4 or DATA_SYNC4. This is done to prevent the

buffer from being freed and reused before the data can be flushed

to stable storage on the server.

When a response is returned from either a WRITE or a COMMIT

operation and it contains a write verifier that is different than

previously returned by the server, the client will need to

retransmit all of the buffers containing uncommitted cached data

to the server. How this is to be done is up to the implementor.

If there is only one buffer of interest, then it should probably

be sent back over in a WRITE request with the appropriate stable

parameter. If there is more than one buffer, it might be

worthwhile retransmitting all of the buffers in WRITE requests

with the stable parameter set to UNSTABLE4 and then retransmitting

the COMMIT operation to flush all of the data on the server to

stable storage. The timing of these retransmissions is left to

the implementor.

The above description applies to page-cache-based systems as well

as buffer-cache-based systems. In those systems, the virtual

memory system will need to be modified instead of the buffer

cache.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_IO

NFS4ERR_ISDIR

NFS4ERR_LOCKED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.4. Operation 6: CREATE - Create a Non-Regular File Object

SYNOPSIS

(cfh), name, type -> (cfh), change_info

ARGUMENT

union createtype4 switch (nfs_ftype4 type) {

case NF4LNK:

linktext4 linkdata;

case NF4BLK:

case NF4CHR:

specdata4 devdata;

case NF4SOCK:

case NF4FIFO:

case NF4DIR:

void;

};

struct CREATE4args {

/* CURRENT_FH: directory for creation */

component4 objname;

createtype4 objtype;

};

RESULT

struct CREATE4resok {

change_info4 cinfo;

};

union CREATE4res switch (nfsstat4 status) {

case NFS4_OK:

CREATE4resok resok4;

default:

void;

};

DESCRIPTION

The CREATE operation creates a non-regular file object in a

directory with a given name. The OPEN procedure MUST be used to

create a regular file.

The objname specifies the name for the new object. If the objname

has a length of 0 (zero), the error NFS4ERR_INVAL will be

returned. The objtype determines the type of object to be

created: directory, symlink, etc.

If an object of the same name already exists in the directory, the

server will return the error NFS4ERR_EXIST.

For the directory where the new file object was created, the

server returns change_info4 information in cinfo. With the atomic

field of the change_info4 struct, the server will indicate if the

before and after change attributes were obtained atomically with

respect to the file object creation.

If the objname has a length of 0 (zero), or if objname does not

obey the UTF-8 definition, the error NFS4ERR_INVAL will be

returned.

The current filehandle is replaced by that of the new object.

IMPLEMENTATION

If the client desires to set attribute values after the create, a

SETATTR operation can be added to the COMPOUND request so that the

appropriate attributes will be set.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_BADTYPE

NFS4ERR_DQUOT

NFS4ERR_EXIST

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NAMETOOLONG

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOSPC

NFS4ERR_NOTDIR

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting Recovery

SYNOPSIS

clientid ->

ARGUMENT

struct DELEGPURGE4args {

clientid4 clientid;

};

RESULT

struct DELEGPURGE4res {

nfsstat4 status;

};

DESCRIPTION

Purges all of the delegations awaiting recovery for a given

client. This is useful for clients which do not commit delegation

information to stable storage to indicate that conflicting

requests need not be delayed by the server awaiting recovery of

delegation information.

This operation should be used by clients that record delegation

information on stable storage on the client. In this case,

DELEGPURGE should be issued immediately after doing delegation

recovery on all delegations know to the client. Doing so will

notify the server that no additional delegations for the client

will be recovered allowing it to free resources, and avoid

delaying other clients who make requests that conflict with the

unrecovered delegations. The set of delegations known to the

server and the client may be different. The reason for this is

that a client may fail after making a request which resulted in

delegation but before it received the results and committed them

to the client's stable storage.

ERRORS

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE_CLIENTID

14.2.6. Operation 8: DELEGRETURN - Return Delegation

SYNOPSIS

stateid ->

ARGUMENT

struct DELEGRETURN4args {

stateid4 stateid;

};

RESULT

struct DELEGRETURN4res {

nfsstat4 status;

};

DESCRIPTION

Returns the delegation represented by the given stateid.

ERRORS

NFS4ERR_BAD_STATEID

NFS4ERR_OLD_STATEID

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE_STATEID

14.2.7. Operation 9: GETATTR - Get Attributes

SYNOPSIS

(cfh), attrbits -> attrbits, attrvals

ARGUMENT

struct GETATTR4args {

/* CURRENT_FH: directory or file */

bitmap4 attr_request;

};

RESULT

struct GETATTR4resok {

fattr4 obj_attributes;

};

union GETATTR4res switch (nfsstat4 status) {

case NFS4_OK:

GETATTR4resok resok4;

default:

void;

};

DESCRIPTION

The GETATTR operation will obtain attributes for the file system

object specified by the current filehandle. The client sets a bit

in the bitmap argument for each attribute value that it would like

the server to return. The server returns an attribute bitmap that

indicates the attribute values for which it was able to return,

followed by the attribute values ordered lowest attribute number

first.

The server must return a value for each attribute that the client

requests if the attribute is supported by the server. If the

server does not support an attribute or cannot approximate a

useful value then it must not return the attribute value and must

not set the attribute bit in the result bitmap. The server must

return an error if it supports an attribute but cannot obtain its

value. In that case no attribute values will be returned.

All servers must support the mandatory attributes as specified in

the section "File Attributes".

On success, the current filehandle retains its value.

IMPLEMENTATION

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.8. Operation 10: GETFH - Get Current Filehandle

SYNOPSIS

(cfh) -> filehandle

ARGUMENT

/* CURRENT_FH: */

void;

RESULT

struct GETFH4resok {

nfs_fh4 object;

};

union GETFH4res switch (nfsstat4 status) {

case NFS4_OK:

GETFH4resok resok4;

default:

void;

};

DESCRIPTION

This operation returns the current filehandle value.

On success, the current filehandle retains its value.

IMPLEMENTATION

Operations that change the current filehandle like LOOKUP or

CREATE do not automatically return the new filehandle as a result.

For instance, if a client needs to lookup a directory entry and

obtain its filehandle then the following request is needed.

PUTFH (directory filehandle)

LOOKUP (entry name)

GETFH

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.9. Operation 11: LINK - Create Link to a File

SYNOPSIS

(sfh), (cfh), newname -> (cfh), change_info

ARGUMENT

struct LINK4args {

/* SAVED_FH: source object */

/* CURRENT_FH: target directory */

component4 newname;

};

RESULT

struct LINK4resok {

change_info4 cinfo;

};

union LINK4res switch (nfsstat4 status) {

case NFS4_OK:

LINK4resok resok4;

default:

void;

};

DESCRIPTION

The LINK operation creates an additional newname for the file

represented by the saved filehandle, as set by the SAVEFH

operation, in the directory represented by the current filehandle.

The existing file and the target directory must reside within the

same file system on the server. On success, the current

filehandle will continue to be the target directory.

For the target directory, the server returns change_info4

information in cinfo. With the atomic field of the change_info4

struct, the server will indicate if the before and after change

attributes were obtained atomically with respect to the link

creation.

If the newname has a length of 0 (zero), or if newname does not

obey the UTF-8 definition, the error NFS4ERR_INVAL will be

returned.

IMPLEMENTATION

Changes to any property of the "hard" linked files are reflected

in all of the linked files. When a link is made to a file, the

attributes for the file should have a value for numlinks that is

one greater than the value before the LINK operation.

The comments under RENAME regarding object and target residing on

the same file system apply here as well. The comments regarding

the target name applies as well.

Note that symbolic links are created with the CREATE operation.

ERRORS

NFS4ERR_ACCES NFS4ERR_BADHANDLE NFS4ERR_DELAY NFS4ERR_DQUOT

NFS4ERR_EXIST NFS4ERR_FHEXPIRED NFS4ERR_INVAL NFS4ERR_IO

NFS4ERR_ISDIR NFS4ERR_MLINK NFS4ERR_MOVED NFS4ERR_NAMETOOLONG

NFS4ERR_NOFILEHANDLE NFS4ERR_NOSPC NFS4ERR_NOTDIR NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE NFS4ERR_ROFS NFS4ERR_SERVERFAULT NFS4ERR_STALE

NFS4ERR_WRONGSEC NFS4ERR_XDEV

14.2.10. Operation 12: LOCK - Create Lock

SYNOPSIS

(cfh) type, seqid, reclaim, stateid, offset, length -> stateid,

access

ARGUMENT

enum nfs4_lock_type {

READ_LT = 1,

WRITE_LT = 2,

READW_LT = 3, /* blocking read */

WRITEW_LT = 4 /* blocking write */ };

struct LOCK4args {

/* CURRENT_FH: file */

nfs_lock_type4 locktype;

seqid4 seqid;

bool reclaim;

stateid4 stateid;

offset4 offset;

length4 length; };

RESULT

struct LOCK4denied {

nfs_lockowner4 owner;

offset4 offset;

length4 length; };

union LOCK4res switch (nfsstat4 status) {

case NFS4_OK:

stateid4 stateid;

case NFS4ERR_DENIED:

LOCK4denied denied;

default:

void; };

DESCRIPTION

The LOCK operation requests a record lock for the byte range

specified by the offset and length parameters. The lock type is

also specified to be one of the nfs4_lock_types. If this is a

reclaim request, the reclaim parameter will be TRUE;

Bytes in a file may be locked even if those bytes are not

currently allocated to the file. To lock the file from a specific

offset through the end-of-file (no matter how long the file

actually is) use a length field with all bits set to 1 (one). To

lock the entire file, use an offset of 0 (zero) and a length with

all bits set to 1. A length of 0 is reserved and should not be

used.

In the case that the lock is denied, the owner, offset, and length

of a conflicting lock are returned.

On success, the current filehandle retains its value.

IMPLEMENTATION

If the server is unable to determine the exact offset and length

of the conflicting lock, the same offset and length that were

provided in the arguments should be returned in the denied

results. The File Locking section contains a full description of

this and the other file locking operations.

ERRORS

NFS4ERR_ACCES NFS4ERR_BADHANDLE NFS4ERR_BAD_SEQID

NFS4ERR_BAD_STATEID NFS4ERR_DELAY NFS4ERR_DENIED NFS4ERR_EXPIRED

NFS4ERR_FHEXPIRED NFS4ERR_GRACE NFS4ERR_INVAL NFS4ERR_ISDIR

NFS4ERR_LEASE_MOVED NFS4ERR_LOCK_RANGE NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE NFS4ERR_OLD_STATEID NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT NFS4ERR_STALE NFS4ERR_STALE_CLIENTID

NFS4ERR_STALE_STATEID NFS4ERR_WRONGSEC

14.2.11. Operation 13: LOCKT - Test For Lock

SYNOPSIS

(cfh) type, owner, offset, length -> {void, NFS4ERR_DENIED ->

owner}

ARGUMENT

struct LOCKT4args {

/* CURRENT_FH: file */

nfs_lock_type4 locktype;

nfs_lockowner4 owner;

offset4 offset;

length4 length; };

RESULT

union LOCKT4res switch (nfsstat4 status) {

case NFS4ERR_DENIED:

LOCK4denied denied;

case NFS4_OK:

void;

default:

void; };

DESCRIPTION

The LOCKT operation tests the lock as specified in the arguments.

If a conflicting lock exists, the owner, offset, and length of the

conflicting lock are returned; if no lock is held, nothing other

than NFS4_OK is returned.

On success, the current filehandle retains its value.

IMPLEMENTATION

If the server is unable to determine the exact offset and length

of the conflicting lock, the same offset and length that were

provided in the arguments should be returned in the denied

results. The File Locking section contains further discussion of

the file locking mechanisms.

LOCKT uses nfs_lockowner4 instead of a stateid4, as LOCK does, to

identify the owner so that the client does not have to open the

file to test for the existence of a lock.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_DENIED

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_ISDIR

NFS4ERR_LEASE_MOVED

NFS4ERR_LOCK_RANGE

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_STALE_CLIENTID

NFS4ERR_WRONGSEC

14.2.12. Operation 14: LOCKU - Unlock File

SYNOPSIS

(cfh) type, seqid, stateid, offset, length -> stateid

ARGUMENT

struct LOCKU4args {

/* CURRENT_FH: file */

nfs_lock_type4 locktype;

seqid4 seqid;

stateid4 stateid;

offset4 offset;

length4 length;

};

RESULT

union LOCKU4res switch (nfsstat4 status) {

case NFS4_OK:

stateid4 stateid;

default:

void;

};

DESCRIPTION

The LOCKU operation unlocks the record lock specified by the

parameters.

On success, the current filehandle retains its value.

IMPLEMENTATION

The File Locking section contains a full description of this and

the other file locking procedures.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_BAD_SEQID

NFS4ERR_BAD_STATEID

NFS4ERR_EXPIRED

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_LOCK_RANGE

NFS4ERR_LEASE_MOVED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_OLD_STATEID

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_STALE_CLIENTID

NFS4ERR_STALE_STATEID

14.2.13. Operation 15: LOOKUP - Lookup Filename

SYNOPSIS

(cfh), filenames -> (cfh)

ARGUMENT

struct LOOKUP4args {

/* CURRENT_FH: directory */

pathname4 path;

};

RESULT

struct LOOKUP4res {

/* CURRENT_FH: object */

nfsstat4 status;

};

DESCRIPTION

This operation LOOKUPs or finds a file system object starting from

the directory specified by the current filehandle. LOOKUP

evaluates the pathname contained in the array of names and obtains

a new current filehandle from the final name. All but the final

name in the list must be the names of directories.

If the pathname cannot be evaluated either because a component

does not exist or because the client does not have permission to

evaluate a component of the path, then an error will be returned

and the current filehandle will be unchanged.

If the path is a zero length array, if any component does not obey

the UTF-8 definition, or if any component in the path is of zero

length, the error NFS4ERR_INVAL will be returned.

IMPLEMENTATION

If the client prefers a partial evaluation of the path then a

sequence of LOOKUP operations can be substituted e.g.

PUTFH (directory filehandle)

LOOKUP "pub" "foo" "bar"

GETFH

or, if the client wishes to obtain the intermediate filehandles

PUTFH (directory filehandle)

LOOKUP "pub"

GETFH

LOOKUP "foo"

GETFH

LOOKUP "bar"

GETFH

NFS version 4 servers depart from the semantics of previous NFS

versions in allowing LOOKUP requests to cross mountpoints on the

server. The client can detect a mountpoint crossing by comparing

the fsid attribute of the directory with the fsid attribute of the

directory looked up. If the fsids are different then the new

directory is a server mountpoint. Unix clients that detect a

mountpoint crossing will need to mount the server's filesystem.

This needs to be done to maintain the file object identity

checking mechanisms common to Unix clients.

Servers that limit NFS access to "shares" or "exported"

filesystems should provide a pseudo-filesystem into which the

exported filesystems can be integrated, so that clients can browse

the server's name space. The clients view of a pseudo filesystem

will be limited to paths that lead to exported filesystems.

Note: previous versions of the protocol assigned special semantics

to the names "." and "..". NFS version 4 assigns no special

semantics to these names. The LOOKUPP operator must be used to

lookup a parent directory.

Note that this procedure does not follow symbolic links. The

client is responsible for all parsing of filenames including

filenames that are modified by symbolic links encountered during

the lookup process.

If the current file handle supplied is not a directory but a

symbolic link, the error NFS4ERR_SYMLINK is returned as the error.

For all other non-directory file types, the error NFS4ERR_NOTDIR

is returned.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NAMETOOLONG

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTDIR

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_SYMLINK

NFS4ERR_WRONGSEC

14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory

SYNOPSIS

(cfh) -> (cfh)

ARGUMENT

/* CURRENT_FH: object */

void;

RESULT

struct LOOKUPP4res {

/* CURRENT_FH: directory */

nfsstat4 status;

};

DESCRIPTION

The current filehandle is assumed to refer to a regular directory

or a named attribute directory. LOOKUPP assigns the filehandle

for its parent directory to be the current filehandle. If there

is no parent directory an NFS4ERR_ENOENT error must be returned.

Therefore, NFS4ERR_ENOENT will be returned by the server when the

current filehandle is at the root or top of the server's file

tree.

IMPLEMENTATION

As for LOOKUP, LOOKUPP will also cross mountpoints.

If the current filehandle is not a directory or named attribute

directory, the error NFS4ERR_NOTDIR is returned.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTDIR

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.15. Operation 17: NVERIFY - Verify Difference in Attributes

SYNOPSIS

(cfh), fattr -> -

ARGUMENT

struct NVERIFY4args {

/* CURRENT_FH: object */

fattr4 obj_attributes;

};

RESULT

struct NVERIFY4res {

nfsstat4 status;

};

DESCRIPTION

This operation is used to prefix a sequence of operations to be

performed if one or more attributes have changed on some

filesystem object. If all the attributes match then the error

NFS4ERR_SAME must be returned.

On success, the current filehandle retains its value.

IMPLEMENTATION

This operation is useful as a cache validation operator. If the

object to which the attributes belong has changed then the

following operations may obtain new data associated with that

object. For instance, to check if a file has been changed and

obtain new data if it has:

PUTFH (public)

LOOKUP "pub" "foo" "bar"

NVERIFY attrbits attrs

READ 0 32767

In the case that a recommended attribute is specified in the

NVERIFY operation and the server does not support that attribute

for the file system object, the error NFS4ERR_NOTSUPP is returned

to the client.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_SAME

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.16. Operation 18: OPEN - Open a Regular File

SYNOPSIS

(cfh), claim, openhow, owner, seqid, access, deny -> (cfh),

stateid, cinfo, rflags, open_confirm, delegation

ARGUMENT

struct OPEN4args {

open_claim4 claim;

openflag4 openhow;

nfs_lockowner4 owner;

seqid4 seqid;

uint32_t share_access;

uint32_t share_deny;

};

enum createmode4 {

UNCHECKED4 = 0,

GUARDED4 = 1,

EXCLUSIVE4 = 2

};

union createhow4 switch (createmode4 mode) {

case UNCHECKED4:

case GUARDED4:

fattr4 createattrs;

case EXCLUSIVE4:

verifier4 createverf;

};

enum opentype4 {

OPEN4_NOCREATE = 0,

OPEN4_CREATE = 1

};

union openflag4 switch (opentype4 opentype) {

case OPEN4_CREATE:

createhow4 how;

default:

void;

};

/* Next definitions used for OPEN delegation */

enum limit_by4 {

NFS_LIMIT_SIZE = 1,

NFS_LIMIT_BLOCKS = 2

/* others as needed */

};

struct nfs_modified_limit4 {

uint32_t num_blocks;

uint32_t bytes_per_block;

};

union nfs_space_limit4 switch (limit_by4 limitby) {

/* limit specified as file size */

case NFS_LIMIT_SIZE:

uint64_t filesize;

/* limit specified by number of blocks */

case NFS_LIMIT_BLOCKS:

nfs_modified_limit4 mod_blocks;

} ;

enum open_delegation_type4 {

OPEN_DELEGATE_NONE = 0,

OPEN_DELEGATE_READ = 1,

OPEN_DELEGATE_WRITE = 2

};

enum open_claim_type4 {

CLAIM_NULL = 0,

CLAIM_PREVIOUS = 1,

CLAIM_DELEGATE_CUR = 2,

CLAIM_DELEGATE_PREV = 3

};

struct open_claim_delegate_cur4 {

pathname4 file;

stateid4 delegate_stateid;

};

union open_claim4 switch (open_claim_type4 claim) {

/*

* No special rights to file. Ordinary OPEN of the specified file.

*/

case CLAIM_NULL:

/* CURRENT_FH: directory */

pathname4 file;

/*

* Right to the file established by an open previous to server

* reboot. File identified by filehandle obtained at that time

* rather than by name.

*/

case CLAIM_PREVIOUS:

/* CURRENT_FH: file being reclaimed */

uint32_t delegate_type;

/*

* Right to file based on a delegation granted by the server.

* File is specified by name.

*/

case CLAIM_DELEGATE_CUR:

/* CURRENT_FH: directory */

open_claim_delegate_cur4 delegate_cur_info;

/* Right to file based on a delegation granted to a previous boot

* instance of the client. File is specified by name.

*/

case CLAIM_DELEGATE_PREV:

/* CURRENT_FH: directory */

pathname4 file_delegate_prev;

};

RESULT

struct open_read_delegation4 {

stateid4 stateid; /* Stateid for delegation*/

bool recall; /* Pre-recalled flag for

delegations obtained

by reclaim

(CLAIM_PREVIOUS) */

nfsace4 permissions; /* Defines users who don't

need an ACCESS call to

open for read */

};

struct open_write_delegation4 {

stateid4 stateid; /* Stateid for delegation*/

bool recall; /* Pre-recalled flag for

delegations obtained

by reclaim

(CLAIM_PREVIOUS) */

nfs_space_limit4 space_limit; /* Defines condition that

the client must check to

determine whether the

file needs to be flushed

to the server on close.

*/

nfsace4 permissions; /* Defines users who don't

need an ACCESS call as

part of a delegated

open. */

};

union open_delegation4

switch (open_delegation_type4 delegation_type) {

case OPEN_DELEGATE_NONE:

void;

case OPEN_DELEGATE_READ:

open_read_delegation4 read;

case OPEN_DELEGATE_WRITE:

open_write_delegation4 write;

};

const OPEN4_RESULT_MLOCK = 0x00000001;

const OPEN4_RESULT_CONFIRM= 0x00000002;

struct OPEN4resok {

stateid4 stateid; /* Stateid for open */

change_info4 cinfo; /* Directory Change Info */

uint32_t rflags; /* Result flags */

verifier4 open_confirm; /* OPEN_CONFIRM verifier */

open_delegation4 delegation; /* Info on any open

delegation */

};

union OPEN4res switch (nfsstat4 status) {

case NFS4_OK:

/* CURRENT_FH: opened file */

OPEN4resok resok4;

default:

void;

};

WARNING TO CLIENT IMPLEMENTORS

OPEN resembles LOOKUP in that it generates a filehandle for the

client to use. Unlike LOOKUP though, OPEN creates server state on

the filehandle. In normal circumstances, the client can only

release this state with a CLOSE operation. CLOSE uses the current

filehandle to determine which file to close. Therefore the client

MUST follow every OPEN operation with a GETFH operation in the

same COMPOUND procedure. This will supply the client with the

filehandle such that CLOSE can be used appropriately.

Simply waiting for the lease on the file to expire is insufficient

because the server may maintain the state indefinitely as long as

another client does not attempt to make a conflicting access to

the same file.

DESCRIPTION

The OPEN operation creates and/or opens a regular file in a

directory with the provided name. If the file does not exist at

the server and creation is desired, specification of the method of

creation is provided by the openhow parameter. The client has the

choice of three creation methods: UNCHECKED, GUARDED, or

EXCLUSIVE.

UNCHECKED means that the file should be created if a file of that

name does not exist and encountering an existing regular file of

that name is not an error. For this type of create, createattrs

specifies the initial set of attributes for the file. The set of

attributes may includes any writable attribute valid for regular

files. When an UNCHECKED create encounters an existing file, the

attributes specified by createattrs is not used, except that when

an object_size of zero is specified, the existing file is

truncated. If GUARDED is specified, the server checks for the

presence of a duplicate object by name before performing the

create. If a duplicate exists, an error of NFS4ERR_EXIST is

returned as the status. If the object does not exist, the request

is performed as described for UNCHECKED.

EXCLUSIVE specifies that the server is to follow exclusive

creation semantics, using the verifier to ensure exclusive

creation of the target. The server should check for the presence

of a duplicate object by name. If the object does not exist, the

server creates the object and stores the verifier with the object.

If the object does exist and the stored verifier matches the

client provided verifier, the server uses the existing object as

the newly created object. If the stored verifier does not match,

then an error of NFS4ERR_EXIST is returned. No attributes may be

provided in this case, since the server may use an attribute of

the target object to store the verifier.

For the target directory, the server returns change_info4

information in cinfo. With the atomic field of the change_info4

struct, the server will indicate if the before and after change

attributes were obtained atomically with respect to the link

creation.

Upon successful creation, the current filehandle is replaced by

that of the new object.

The OPEN procedure provides for DOS SHARE capability with the use

of the access and deny fields of the OPEN arguments. The client

specifies at OPEN the required access and deny modes. For clients

that do not directly support SHAREs (i.e. Unix), the expected deny

value is DENY_NONE. In the case that there is a existing SHARE

reservation that conflicts with the OPEN request, the server

returns the error NFS4ERR_DENIED. For a complete SHARE request,

the client must provide values for the owner and seqid fields for

the OPEN argument. For additional discussion of SHARE semantics

see the section on 'Share Reservations'.

In the case that the client is recovering state from a server

failure, the reclaim field of the OPEN argument is used to signify

that the request is meant to reclaim state previously held.

The "claim" field of the OPEN argument is used to specify the file

to be opened and the state information which the client claims to

possess. There are four basic claim types which cover the various

situations for an OPEN. They are as follows:

CLAIM_NULL

For the client, this is a new OPEN

request and there is no previous state

associate with the file for the client.

CLAIM_PREVIOUS

The client is claiming basic OPEN state

for a file that was held previous to a

server reboot. Generally used when a

server is returning persistent file

handles; the client may not have the

file name to reclaim the OPEN.

CLAIM_DELEGATE_CUR

The client is claiming a delegation for

OPEN as granted by the server.

Generally this is done as part of

recalling a delegation.

CLAIM_DELEGATE_PREV

The client is claiming a delegation

granted to a previous client instance;

used after the client reboots.

For OPEN requests whose claim type is other than CLAIM_PREVIOUS

(i.e. requests other than those devoted to reclaiming opens after

a server reboot) that reach the server during its grace or lease

expiration period, the server returns an error of NFS4ERR_GRACE.

For any OPEN request, the server may return an open delegation,

which allows further opens and closes to be handled locally on the

client as described in the section Open Delegation. Note that

delegation is up to the server to decide. The client should never

assume that delegation will or will not be granted in a particular

instance. It should always be prepared for either case. A

partial exception is the reclaim (CLAIM_PREVIOUS) case, in which a

delegation type is claimed. In this case, delegation will always

be granted, although the server may specify an immediate recall in

the delegation structure.

The rflags returned by a successful OPEN allow the server to

return information governing how the open file is to be handled.

OPEN4_RESULT_MLOCK indicates to the caller that mandatory locking

is in effect for this file and the client should act appropriately

with regard to data cached on the client. OPEN4_RESULT_CONFIRM

indicates that the client MUST execute an OPEN_CONFIRM operation

before using the open file.

If the file is a zero length array, if any component does not obey

the UTF-8 definition, or if any component in the path is of zero

length, the error NFS4ERR_INVAL will be returned.

When an OPEN is done and the specified lockowner already has the

resulting filehandle open, the result is to "OR" together the new

share and deny status together with the existing status. In this

case, only a single CLOSE need be done, even though multiple

OPEN's were completed.

IMPLEMENTATION

The OPEN procedure contains support for EXCLUSIVE create. The

mechanism is similar to the support in NFS version 3 [RFC1813].

As in NFS version 3, this mechanism provides reliable exclusive

creation. Exclusive create is invoked when the how parameter is

EXCLUSIVE. In this case, the client provides a verifier that can

reasonably be expected to be unique. A combination of a client

identifier, perhaps the client network address, and a unique

number generated by the client, perhaps the RPC transaction

identifier, may be appropriate.

If the object does not exist, the server creates the object and

stores the verifier in stable storage. For file systems that do

not provide a mechanism for the storage of arbitrary file

attributes, the server may use one or more elements of the object

meta-data to store the verifier. The verifier must be stored in

stable storage to prevent erroneous failure on retransmission of

the request. It is assumed that an exclusive create is being

performed because exclusive semantics are critical to the

application. Because of the expected usage, exclusive CREATE does

not rely solely on the normally volatile duplicate request cache

for storage of the verifier. The duplicate request cache in

volatile storage does not survive a crash and may actually flush

on a long network partition, opening failure windows. In the UNIX

local file system environment, the expected storage location for

the verifier on creation is the meta-data (time stamps) of the

object. For this reason, an exclusive object create may not

include initial attributes because the server would have nowhere

to store the verifier.

If the server can not support these exclusive create semantics,

possibly because of the requirement to commit the verifier to

stable storage, it should fail the OPEN request with the error,

NFS4ERR_NOTSUPP.

During an exclusive CREATE request, if the object already exists,

the server reconstructs the object's verifier and compares it with

the verifier in the request. If they match, the server treats the

request as a success. The request is presumed to be a duplicate of

an earlier, successful request for which the reply was lost and

that the server duplicate request cache mechanism did not detect.

If the verifiers do not match, the request is rejected with the

status, NFS4ERR_EXIST.

Once the client has performed a successful exclusive create, it

must issue a SETATTR to set the correct object attributes. Until

it does so, it should not rely upon any of the object attributes,

since the server implementation may need to overload object meta-

data to store the verifier. The subsequent SETATTR must not occur

in the same COMPOUND request as the OPEN. This separation will

guarantee that the exclusive create mechanism will continue to

function properly in the face of retransmission of the request.

Use of the GUARDED attribute does not provide exactly-once

semantics. In particular, if a reply is lost and the server does

not detect the retransmission of the request, the procedure can

fail with NFS4ERR_EXIST, even though the create was performed

successfully.

For SHARE reservations, the client must specify a value for access

that is one of READ, WRITE, or BOTH. For deny, the client must

specify one of NONE, READ, WRITE, or BOTH. If the client fails to

do this, the server must return NFS4ERR_INVAL.

If the final component provided to OPEN is a symbolic link, the

error NFS4ERR_SYMLINK will be returned to the client. If an

intermediate component of the pathname provided to OPEN is a

symbolic link, the error NFS4ERR_NOTDIR will be returned to the

client.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BAD_SEQID

NFS4ERR_DELAY

NFS4ERR_DQUOT

NFS4ERR_EXIST

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_IO

NFS4ERR_ISDIR

NFS4ERR_LEASE_MOVED

NFS4ERR_MOVED

NFS4ERR_NAMETOOLONG

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOSPC

NFS4ERR_NOTDIR

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_SHARE_DENIED

NFS4ERR_STALE_CLIENTID

NFS4ERR_SYMLINK

14.2.17. Operation 19: OPENATTR - Open Named Attribute Directory

SYNOPSIS

(cfh) -> (cfh)

ARGUMENT

/* CURRENT_FH: file or directory */

void;

RESULT

struct OPENATTR4res {

/* CURRENT_FH: name attr directory*/

nfsstat4 status;

};

DESCRIPTION

The OPENATTR operation is used to obtain the filehandle of the

named attribute directory associated with the current filehandle.

The result of the OPENATTR will be a filehandle to an object of

type NF4ATTRDIR. From this filehandle, READDIR and LOOKUP

procedures can be used to obtain filehandles for the various named

attributes associated with the original file system object.

Filehandles returned within the named attribute directory will

have a type of NF4NAMEDATTR.

IMPLEMENTATION

If the server does not support named attributes for the current

filehandle, an error of NFS4ERR_NOTSUPP will be returned to the

client.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open

SYNOPSIS

(cfh), seqid, open_confirm-> stateid

ARGUMENT

struct OPEN_CONFIRM4args {

/* CURRENT_FH: opened file */

seqid4 seqid;

verifier4 open_confirm; /* OPEN_CONFIRM verifier */

};

RESULT

struct OPEN_CONFIRM4resok {

stateid4 stateid;

};

union OPEN_CONFIRM4res switch (nfsstat4 status) {

case NFS4_OK:

OPEN_CONFIRM4resok resok4;

default:

void;

};

DESCRIPTION

This operation is used to confirm the sequence id usage for the

first time that a nfs_lockowner is used by a client. The OPEN

operation returns a opaque confirmation verifier that is then

passed to this operation along with the next sequence id for the

nfs_lockowner. The sequence id passed to the OPEN_CONFIRM must be

1 (one) greater than the seqid passed to the OPEN operation from

which the open_confirm value was obtained. If the server receives

an unexpected sequence id with respect to the original open, then

the server assumes that the client will not confirm the original

OPEN and all state associated with the original OPEN is released

by the server.

On success, the current filehandle retains its value.

IMPLEMENTATION

A given client might generate many nfs_lockowner data structures

for a given clientid. The client will periodically either dispose

of its nfs_lockowners or stop using them for indefinite periods of

time. The latter situation is why the NFS version 4 protocol does

not have a an explicit operation to exit an nfs_lockowner: such an

operation is of no use in that situation. Instead, to avoid

unbounded memory use, the server needs to implement a strategy for

disposing of nfs_lockowners that have no current lock, open, or

delegation state for any files and have not been used recently.

The time period used to determine when to dispose of

nfs_lockowners is an implementation choice. The time period

should certainly be no less than the lease time plus any grace

period the server wishes to implement beyond a lease time. The

OPEN_CONFIRM operation allows the server to safely dispose of

unused nfs_lockowner data structures.

In the case that a client issues an OPEN operation and the server

no longer has a record of the nfs_lockowner, the server needs

ensure that this is a new OPEN and not a replay or retransmission.

A lazy server implementation might require confirmation for every

nfs_lockowner for which it has no record. However, this is not

necessary until the server records the fact that it has disposed

of one nfs_lockowner for the given clientid.

The server must hold unconfirmed OPEN state until one of three

events occur. First, the client sends an OPEN_CONFIRM request

with the appropriate sequence id and confirmation verifier within

the lease period. In this case, the OPEN state on the server goes

to confirmed, and the nfs_lockowner on the server is fully

established.

Second, the client sends another OPEN request with a sequence id

that is incorrect for the nfs_lockowner (out of sequence). In

this case, the server assumes the second OPEN request is valid and

the first one is a replay. The server cancels the OPEN state of

the first OPEN request, establishes an unconfirmed OPEN state for

the second OPEN request, and responds to the second OPEN request

with an indication that an OPEN_CONFIRM is needed. The process

then repeats itself. While there is a potential for a denial of

service attack on the client, it is mitigated if the client and

server require the use of a security flavor based on Kerberos V5,

LIPKEY, or some other flavor that uses cryptography.

What if the server is in the unconfirmed OPEN state for a given

nfs_lockowner, and it receives an operation on the nfs_lockowner

that has a stateid but the operation is not OPEN, or it is

OPEN_CONFIRM but with the wrong confirmation verifier? Then, even

if the seqid is correct, the server returns NFS4ERR_BAD_STATEID,

because the server assumes the operation is a replay: if the

server has no established OPEN state, then there is no way, for

example, a LOCK operation could be valid.

Third, neither of the two aforementioned events occur for the

nfs_lockowner within the lease period. In this case, the OPEN

state is cancelled and disposal of the nfs_lockowner can occur.

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_BAD_SEQID

NFS4ERR_EXPIRED

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_MOVED

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.19. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access

SYNOPSIS

(cfh), stateid, seqid, access, deny -> stateid

ARGUMENT

struct OPEN_DOWNGRADE4args {

/* CURRENT_FH: opened file */

stateid4 stateid;

seqid4 seqid;

uint32_t share_access;

uint32_t share_deny;

};

RESULT

struct OPEN_DOWNGRADE4resok {

stateid4 stateid;

};

union OPEN_DOWNGRADE4res switch(nfsstat4 status) {

case NFS4_OK:

OPEN_DOWNGRADE4resok resok4;

default:

void;

};

This operation is used to adjust the access and deny bits for a given

open. This is necessary when a given lockowner opens the same file

multiple times with different access and deny flags. In this

situation, a close of one of the open's may change the appropriate

access and deny flags to remove bits associated with open's no longer

in effect.

The access and deny bits specified in this operation replace the

current ones for the specified open file. If either the access or

the deny mode specified includes bits not in effect for the open, the

error NFS4ERR_INVAL should be returned. Since access and deny bits

are subsets of those already granted, it is not possible for this

request to be denied because of conflicting share reservations.

On success, the current filehandle retains its value.

ERRORS

NFS4ERR_BADHANDLE NFS4ERR_BAD_SEQID NFS4ERR_BAD_STATEID

NFS4ERR_EXPIRED NFS4ERR_FHEXPIRED NFS4ERR_INVAL NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE NFS4ERR_OLD_STATEID NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT NFS4ERR_STALE NFS4ERR_STALE_STATEID

14.2.20. Operation 22: PUTFH - Set Current Filehandle

SYNOPSIS

filehandle -> (cfh)

ARGUMENT

struct PUTFH4args {

nfs4_fh object; };

RESULT

struct PUTFH4res {

/* CURRENT_FH: */

nfsstat4 status; };

DESCRIPTION

Replaces the current filehandle with the filehandle provided as an

argument.

IMPLEMENTATION

Commonly used as the first operator in an NFS request to set the

context for following operations.

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_MOVED

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.21. Operation 23: PUTPUBFH - Set Public Filehandle

SYNOPSIS

- -> (cfh)

ARGUMENT

void;

RESULT

struct PUTPUBFH4res {

/* CURRENT_FH: public fh */

nfsstat4 status;

};

DESCRIPTION

Replaces the current filehandle with the filehandle that

represents the public filehandle of the server's name space. This

filehandle may be different from the "root" filehandle which may

be associated with some other directory on the server.

IMPLEMENTATION

Used as the first operator in an NFS request to set the context

for following operations.

ERRORS

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_WRONGSEC

14.2.22. Operation 24: PUTROOTFH - Set Root Filehandle

SYNOPSIS

- -> (cfh)

ARGUMENT

void;

RESULT

struct PUTROOTFH4res {

/* CURRENT_FH: root fh */

nfsstat4 status;

};

DESCRIPTION

Replaces the current filehandle with the filehandle that

represents the root of the server's name space. From this

filehandle a LOOKUP operation can locate any other filehandle on

the server. This filehandle may be different from the "public"

filehandle which may be associated with some other directory on

the server.

IMPLEMENTATION

Commonly used as the first operator in an NFS request to set the

context for following operations.

ERRORS

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_WRONGSEC

14.2.23. Operation 25: READ - Read from File

SYNOPSIS

(cfh), offset, count, stateid -> eof, data

ARGUMENT

struct READ4args {

/* CURRENT_FH: file */

stateid4 stateid;

offset4 offset;

count4 count;

};

RESULT

struct READ4resok {

bool eof;

opaque data<>;

};

union READ4res switch (nfsstat4 status) {

case NFS4_OK:

READ4resok resok4;

default:

void;

};

DESCRIPTION

The READ operation reads data from the regular file identified by

the current filehandle.

The client provides an offset of where the READ is to start and a

count of how many bytes are to be read. An offset of 0 (zero)

means to read data starting at the beginning of the file. If

offset is greater than or equal to the size of the file, the

status, NFS4_OK, is returned with a data length set to 0 (zero)

and eof is set to TRUE. The READ is subject to access permissions

checking.

If the client specifies a count value of 0 (zero), the READ

succeeds and returns 0 (zero) bytes of data again subject to

access permissions checking. The server may choose to return

fewer bytes than specified by the client. The client needs to

check for this condition and handle the condition appropriately.

The stateid value for a READ request represents a value returned

from a previous record lock or share reservation request. Used by

the server to verify that the associated lock is still valid and

to update lease timeouts for the client.

If the read ended at the end-of-file (formally, in a correctly

formed READ request, if offset + count is equal to the size of the

file), or the read request extends beyond the size of the file (if

offset + count is greater than the size of the file), eof is

returned as TRUE; otherwise it is FALSE. A successful READ of an

empty file will always return eof as TRUE.

On success, the current filehandle retains its value.

IMPLEMENTATION

It is possible for the server to return fewer than count bytes of

data. If the server returns less than the count requested and eof

set to FALSE, the client should issue another READ to get the

remaining data. A server may return less data than requested

under several circumstances. The file may have been truncated by

another client or perhaps on the server itself, changing the file

size from what the requesting client believes to be the case.

This would reduce the actual amount of data available to the

client. It is possible that the server may back off the transfer

size and reduce the read request return. Server resource

exhaustion may also occur necessitating a smaller read return.

If the file is locked the server will return an NFS4ERR_LOCKED

error. Since the lock may be of short duration, the client may

choose to retransmit the READ request (with exponential bacKOFf)

until the operation succeeds.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_BAD_STATEID

NFS4ERR_DELAY

NFS4ERR_DENIED

NFS4ERR_EXPIRED

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_LOCKED

NFS4ERR_LEASE_MOVED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NXIO

NFS4ERR_OLD_STATEID

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_STALE_STATEID

NFS4ERR_WRONGSEC

14.2.24. Operation 26: READDIR - Read Directory

SYNOPSIS

(cfh), cookie, cookieverf, dircount, maxcount, attrbits ->

cookieverf { cookie, filename, attrbits, attributes }

ARGUMENT

struct READDIR4args {

/* CURRENT_FH: directory */

nfs_cookie4 cookie;

verifier4 cookieverf;

count4 dircount;

count4 maxcount;

bitmap4 attr_request;

};

RESULT

struct entry4 {

nfs_cookie4 cookie;

component4 name;

fattr4 attrs;

entry4 *nextentry;

};

struct dirlist4 {

entry4 *entries;

bool eof;

};

struct READDIR4resok {

verifier4 cookieverf;

dirlist4 reply;

};

union READDIR4res switch (nfsstat4 status) {

case NFS4_OK:

READDIR4resok resok4;

default:

void;

};

DESCRIPTION

The READDIR operation retrieves a variable number of entries from

a file system directory and returns client requested attributes

for each entry along with information to allow the client to

request additional directory entries in a subsequent READDIR.

The arguments contain a cookie value that represents where the

READDIR should start within the directory. A value of 0 (zero)

for the cookie is used to start reading at the beginning of the

directory. For subsequent READDIR requests, the client specifies

a cookie value that is provided by the server on a previous

READDIR request.

The cookieverf value should be set to 0 (zero) when the cookie

value is 0 (zero) (first directory read). On subsequent requests,

it should be a cookieverf as returned by the server. The

cookieverf must match that returned by the READDIR in which the

cookie was acquired.

The dircount portion of the argument is a hint of the maximum

number of bytes of directory information that should be returned.

This value represents the length of the names of the directory

entries and the cookie value for these entries. This length

represents the XDR encoding of the data (names and cookies) and

not the length in the native format of the server. The server may

return less data.

The maxcount value of the argument is the maximum number of bytes

for the result. This maximum size represents all of the data

being returned and includes the XDR overhead. The server may

return less data. If the server is unable to return a single

directory entry within the maxcount limit, the error

NFS4ERR_READDIR_NOSPC will be returned to the client.

Finally, attrbits represents the list of attributes to be returned

for each directory entry supplied by the server.

On successful return, the server's response will provide a list of

directory entries. Each of these entries contains the name of the

directory entry, a cookie value for that entry, and the associated

attributes as requested.

The cookie value is only meaningful to the server and is used as a

"bookmark" for the directory entry. As mentioned, this cookie is

used by the client for subsequent READDIR operations so that it

may continue reading a directory. The cookie is similar in

concept to a READ offset but should not be interpreted as such by

the client. Ideally, the cookie value should not change if the

directory is modified since the client may be caching these

values.

In some cases, the server may encounter an error while obtaining

the attributes for a directory entry. Instead of returning an

error for the entire READDIR operation, the server can instead

return the attribute 'fattr4_rdattr_error'. With this, the server

is able to communicate the failure to the client and not fail the

entire operation in the instance of what might be a transient

failure. Obviously, the client must request the

fattr4_rdattr_error attribute for this method to work properly.

If the client does not request the attribute, the server has no

choice but to return failure for the entire READDIR operation.

For some file system environments, the directory entries "." and

".." have special meaning and in other environments, they may

not. If the server supports these special entries within a

directory, they should not be returned to the client as part of

the READDIR response. To enable some client environments, the

cookie values of 0, 1, and 2 are to be considered reserved. Note

that the Unix client will use these values when combining the

server's response and local representations to enable a fully

formed Unix directory presentation to the application.

For READDIR arguments, cookie values of 1 and 2 should not be used

and for READDIR results cookie values of 0, 1, and 2 should not

returned.

On success, the current filehandle retains its value.

IMPLEMENTATION

The server's file system directory representations can differ

greatly. A client's programming interfaces may also be bound to

the local operating environment in a way that does not translate

well into the NFS protocol. Therefore the use of the dircount and

maxcount fields are provided to allow the client the ability to

provide guidelines to the server. If the client is aggressive

about attribute collection during a READDIR, the server has an

idea of how to limit the encoded response. The dircount field

provides a hint on the number of entries based solely on the names

of the directory entries. Since it is a hint, it may be possible

that a dircount value is zero. In this case, the server is free

to ignore the dircount value and return directory information

based on the specified maxcount value.

The cookieverf may be used by the server to help manage cookie

values that may become stale. It should be a rare occurrence that

a server is unable to continue properly reading a directory with

the provided cookie/cookieverf pair. The server should make every

effort to avoid this condition since the application at the client

may not be able to properly handle this type of failure.

The use of the cookieverf will also protect the client from using

READDIR cookie values that may be stale. For example, if the file

system has been migrated, the server may or may not be able to use

the same cookie values to service READDIR as the previous server

used. With the client providing the cookieverf, the server is

able to provide the appropriate response to the client. This

prevents the case where the server may accept a cookie value but

the underlying directory has changed and the response is invalid

from the client's context of its previous READDIR.

Since some servers will not be returning "." and ".." entries as

has been done with previous versions of the NFS protocol, the

client that requires these entries be present in READDIR responses

must fabricate them.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_BAD_COOKIE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTDIR

NFS4ERR_NOTSUPP

NFS4ERR_READDIR_NOSPC

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_TOOSMALL

NFS4ERR_WRONGSEC

14.2.25. Operation 27: READLINK - Read Symbolic Link

SYNOPSIS

(cfh) -> linktext

ARGUMENT

/* CURRENT_FH: symlink */

void;

RESULT

struct READLINK4resok {

linktext4 link;

};

union READLINK4res switch (nfsstat4 status) {

case NFS4_OK:

READLINK4resok resok4;

default:

void;

};

DESCRIPTION

READLINK reads the data associated with a symbolic link. The data

is a UTF-8 string that is opaque to the server. That is, whether

created by an NFS client or created locally on the server, the

data in a symbolic link is not interpreted when created, but is

simply stored.

On success, the current filehandle retains its value.

IMPLEMENTATION

A symbolic link is nominally a pointer to another file. The data

is not necessarily interpreted by the server, just stored in the

file. It is possible for a client implementation to store a path

name that is not meaningful to the server operating system in a

symbolic link. A READLINK operation returns the data to the

client for interpretation. If different implementations want to

share access to symbolic links, then they must agree on the

interpretation of the data in the symbolic link.

The READLINK operation is only allowed on objects of type NF4LNK.

The server should return the error, NFS4ERR_INVAL, if the object

is not of type, NF4LNK.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.26. Operation 28: REMOVE - Remove Filesystem Object

SYNOPSIS

(cfh), filename -> change_info

ARGUMENT

struct REMOVE4args {

/* CURRENT_FH: directory */

component4 target;

};

RESULT

struct REMOVE4resok {

change_info4 cinfo;

}

union REMOVE4res switch (nfsstat4 status) {

case NFS4_OK:

REMOVE4resok resok4;

default:

void;

}

DESCRIPTION

The REMOVE operation removes (deletes) a directory entry named by

filename from the directory corresponding to the current

filehandle. If the entry in the directory was the last reference

to the corresponding file system object, the object may be

destroyed.

For the directory where the filename was removed, the server

returns change_info4 information in cinfo. With the atomic field

of the change_info4 struct, the server will indicate if the before

and after change attributes were obtained atomically with respect

to the removal.

If the target has a length of 0 (zero), or if target does not obey

the UTF-8 definition, the error NFS4ERR_INVAL will be returned.

On success, the current filehandle retains its value.

IMPLEMENTATION

NFS versions 2 and 3 required a different operator RMDIR for

directory removal. NFS version 4 REMOVE can be used to delete any

directory entry independent of its file type.

The concept of last reference is server specific. However, if the

numlinks field in the previous attributes of the object had the

value 1, the client should not rely on referring to the object via

a file handle. Likewise, the client should not rely on the

resources (disk space, directory entry, and so on) formerly

associated with the object becoming immediately available. Thus,

if a client needs to be able to continue to access a file after

using REMOVE to remove it, the client should take steps to make

sure that the file will still be accessible. The usual mechanism

used is to RENAME the file from its old name to a new hidden name.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NAMETOOLONG

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTDIR

NFS4ERR_NOTEMPTY

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.27. Operation 29: RENAME - Rename Directory Entry

SYNOPSIS

(sfh), oldname (cfh), newname -> source_change_info,

target_change_info

ARGUMENT

struct RENAME4args {

/* SAVED_FH: source directory */

component4 oldname;

/* CURRENT_FH: target directory */

component4 newname;

};

RESULT

struct RENAME4resok {

change_info4 source_cinfo;

change_info4 target_cinfo;

};

union RENAME4res switch (nfsstat4 status) {

case NFS4_OK:

RENAME4resok resok4;

default:

void;

};

DESCRIPTION

The RENAME operation renames the object identified by oldname in

the source directory corresponding to the saved filehandle, as set

by the SAVEFH operation, to newname in the target directory

corresponding to the current filehandle. The operation is

required to be atomic to the client. Source and target

directories must reside on the same file system on the server. On

success, the current filehandle will continue to be the target

directory.

If the target directory already contains an entry with the name,

newname, the source object must be compatible with the target:

either both are non-directories or both are directories and the

target must be empty. If compatible, the existing target is

removed before the rename occurs. If they are not compatible or

if the target is a directory but not empty, the server will return

the error, NFS4ERR_EXIST.

If oldname and newname both refer to the same file (they might be

hard links of each other), then RENAME should perform no action

and return success.

For both directories involved in the RENAME, the server returns

change_info4 information. With the atomic field of the

change_info4 struct, the server will indicate if the before and

after change attributes were obtained atomically with respect to

the rename.

If the oldname or newname has a length of 0 (zero), or if oldname

or newname does not obey the UTF-8 definition, the error

NFS4ERR_INVAL will be returned.

IMPLEMENTATION

The RENAME operation must be atomic to the client. The statement

"source and target directories must reside on the same file system

on the server" means that the fsid fields in the attributes for

the directories are the same. If they reside on different file

systems, the error, NFS4ERR_XDEV, is returned.

A filehandle may or may not become stale or expire on a rename.

However, server implementors are strongly encouraged to attempt to

keep file handles from becoming stale or expiring in this fashion.

On some servers, the filenames, "." and "..", are illegal as

either oldname or newname. In addition, neither oldname nor

newname can be an alias for the source directory. These servers

will return the error, NFS4ERR_INVAL, in these cases.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_DQUOT

NFS4ERR_EXIST

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_ISDIR

NFS4ERR_MOVED

NFS4ERR_NAMETOOLONG

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOSPC

NFS4ERR_NOTDIR

NFS4ERR_NOTEMPTY

NFS4ERR_NOTSUPP

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

NFS4ERR_XDEV

14.2.28. Operation 30: RENEW - Renew a Lease

SYNOPSIS

stateid -> ()

ARGUMENT

struct RENEW4args {

stateid4 stateid;

};

RESULT

struct RENEW4res {

nfsstat4 status;

};

DESCRIPTION

The RENEW operation is used by the client to renew leases which it

currently holds at a server. In processing the RENEW request, the

server renews all leases associated with the client. The

associated leases are determined by the client id provided via the

SETCLIENTID procedure.

The stateid for RENEW may not be one of the special stateids

consisting of all bits 0 (zero) or all bits 1.

IMPLEMENTATION

ERRORS

NFS4ERR_BAD_STATEID

NFS4ERR_EXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_LEASE_MOVED

NFS4ERR_MOVED

NFS4ERR_OLD_STATEID

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE_STATEID

NFS4ERR_WRONGSEC

14.2.29. Operation 31: RESTOREFH - Restore Saved Filehandle

SYNOPSIS

(sfh) -> (cfh)

ARGUMENT

/* SAVED_FH: */

void;

RESULT

struct RESTOREFH4res {

/* CURRENT_FH: value of saved fh */

nfsstat4 status;

};

DESCRIPTION

Set the current filehandle to the value in the saved filehandle.

If there is no saved filehandle then return an error

NFS4ERR_NOFILEHANDLE.

IMPLEMENTATION

Operations like OPEN and LOOKUP use the current filehandle to

represent a directory and replace it with a new filehandle.

Assuming the previous filehandle was saved with a SAVEFH operator,

the previous filehandle can be restored as the current filehandle.

This is commonly used to obtain post-operation attributes for the

directory, e.g.

PUTFH (directory filehandle)

SAVEFH

GETATTR attrbits (pre-op dir attrs)

CREATE optbits "foo" attrs

GETATTR attrbits (file attributes)

RESTOREFH

GETATTR attrbits (post-op dir attrs)

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.30. Operation 32: SAVEFH - Save Current Filehandle

SYNOPSIS

(cfh) -> (sfh)

ARGUMENT

/* CURRENT_FH: */

void;

RESULT

struct SAVEFH4res {

/* SAVED_FH: value of current fh */

nfsstat4 status;

};

DESCRIPTION

Save the current filehandle. If a previous filehandle was saved

then it is no longer accessible. The saved filehandle can be

restored as the current filehandle with the RESTOREFH operator.

On success, the current filehandle retains its value.

IMPLEMENTATION

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.31. Operation 33: SECINFO - Obtain Available Security

SYNOPSIS

(cfh), name -> { secinfo }

ARGUMENT

struct SECINFO4args {

/* CURRENT_FH: */

component4 name;

};

RESULT

enum rpc_gss_svc_t {

RPC_GSS_SVC_NONE = 1,

RPC_GSS_SVC_INTEGRITY = 2,

RPC_GSS_SVC_PRIVACY = 3

};

struct rpcsec_gss_info {

sec_oid4 oid;

qop4 qop;

rpc_gss_svc_t service;

};

struct secinfo4 {

uint32_t flavor;

opaque flavor_info<>; /* null for AUTH_SYS, AUTH_NONE;

contains rpcsec_gss_info for

RPCSEC_GSS. */

};

typedef secinfo4 SECINFO4resok<>;

union SECINFO4res switch (nfsstat4 status) {

case NFS4_OK:

SECINFO4resok resok4;

default:

void;

};

DESCRIPTION

The SECINFO operation is used by the client to obtain a list of

valid RPC authentication flavors for a specific file handle, file

name pair. The result will contain an array which represents the

security mechanisms available. The array entries are represented

by the secinfo4 structure. The field 'flavor' will contain a

value of AUTH_NONE, AUTH_SYS (as defined in [RFC1831]), or

RPCSEC_GSS (as defined in [RFC2203]).

For the flavors, AUTH_NONE, and AUTH_SYS no additional security

information is returned. For a return value of RPCSEC_GSS, a

security triple is returned that contains the mechanism object id

(as defined in [RFC2078]), the quality of protection (as defined

in [RFC2078]) and the service type (as defined in [RFC2203]). It

is possible for SECINFO to return multiple entries with flavor

equal to RPCSEC_GSS with different security triple values.

On success, the current filehandle retains its value.

IMPLEMENTATION

The SECINFO operation is expected to be used by the NFS client

when the error value of NFS4ERR_WRONGSEC is returned from another

NFS operation. This signifies to the client that the server's

security policy is different from what the client is currently

using. At this point, the client is expected to obtain a list of

possible security flavors and choose what best suits its policies.

It is recommended that the client issue the SECINFO call protected

by a security triple that uses either rpc_gss_svc_integrity or

rpc_gss_svc_privacy service. The use of rpc_gss_svc_none would

allow an attacker in the middle to modify the SECINFO results such

that the client might select a weaker algorithm in the set allowed

by server, making the client and/or server vulnerable to further

attacks.

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_FHEXPIRED

NFS4ERR_MOVED

NFS4ERR_NAMETOOLONG

NFS4ERR_NOENT

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTDIR

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.32. Operation 34: SETATTR - Set Attributes

SYNOPSIS

(cfh), attrbits, attrvals -> -

ARGUMENT

struct SETATTR4args {

/* CURRENT_FH: target object */

stateid4 stateid;

fattr4 obj_attributes;

};

RESULT

struct SETATTR4res {

nfsstat4 status;

bitmap4 attrsset;

};

DESCRIPTION

The SETATTR operation changes one or more of the attributes of a

file system object. The new attributes are specified with a

bitmap and the attributes that follow the bitmap in bit order.

The stateid is necessary for SETATTRs that change the size of a

file (modify the attribute object_size). This stateid represents

a record lock, share reservation, or delegation which must be

valid for the SETATTR to modify the file data. A valid stateid

would always be specified. When the file size is not changed, the

special stateid consisting of all bits 0 (zero) should be used.

On either success or failure of the operation, the server will

return the attrsset bitmask to represent what (if any) attributes

were successfully set.

On success, the current filehandle retains its value.

IMPLEMENTATION

The file size attribute is used to request changes to the size of

a file. A value of 0 (zero) causes the file to be truncated, a

value less than the current size of the file causes data from new

size to the end of the file to be discarded, and a size greater

than the current size of the file causes logically zeroed data

bytes to be added to the end of the file. Servers are free to

implement this using holes or actual zero data bytes. Clients

should not make any assumptions regarding a server's

implementation of this feature, beyond that the bytes returned

will be zeroed. Servers must support extending the file size via

SETATTR.

SETATTR is not guaranteed atomic. A failed SETATTR may partially

change a file's attributes.

Changing the size of a file with SETATTR indirectly changes the

time_modify. A client must account for this as size changes can

result in data deletion.

If server and client times differ, programs that compare client

time to file times can break. A time maintenance protocol should

be used to limit client/server time skew.

If the server cannot successfully set all the attributes it must

return an NFS4ERR_INVAL error. If the server can only support 32

bit offsets and sizes, a SETATTR request to set the size of a file

to larger than can be represented in 32 bits will be rejected with

this same error.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_BAD_STATEID

NFS4ERR_DELAY

NFS4ERR_DENIED

NFS4ERR_DQUOT

NFS4ERR_EXPIRED

NFS4ERR_FBIG

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOSPC

NFS4ERR_NOTSUPP

NFS4ERR_OLD_STATEID

NFS4ERR_PERM

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_STALE_STATEID

NFS4ERR_WRONGSEC

14.2.33. Operation 35: SETCLIENTID - Negotiate Clientid

SYNOPSIS

client, callback -> clientid, setclientid_confirm

ARGUMENT

struct SETCLIENTID4args {

nfs_client_id4 client;

cb_client4 callback;

};

RESULT

struct SETCLIENTID4resok {

clientid4 clientid;

verifier4 setclientid_confirm;

};

union SETCLIENTID4res switch (nfsstat4 status) {

case NFS4_OK:

SETCLIENTID4resok resok4;

case NFS4ERR_CLID_INUSE:

clientaddr4 client_using;

default:

void;

};

DESCRIPTION

The SETCLIENTID operation introduces the ability of the client to

notify the server of its intention to use a particular client

identifier and verifier pair. Upon successful completion the

server will return a clientid which is used in subsequent file

locking requests and a confirmation verifier. The client will use

the SETCLIENTID_CONFIRM operation to return the verifier to the

server. At that point, the client may use the clientid in

subsequent operations that require an nfs_lockowner.

The callback information provided in this operation will be used

if the client is provided an open delegation at a future point.

Therefore, the client must correctly reflect the program and port

numbers for the callback program at the time SETCLIENTID is used.

IMPLEMENTATION

The server takes the verifier and client identification supplied

in the nfs_client_id4 and searches for a match of the client

identification. If no match is found the server saves the

principal/uid information along with the verifier and client

identification and returns a unique clientid that is used as a

shorthand reference to the supplied information.

If the server finds matching client identification and a

corresponding match in principal/uid, the server releases all

locking state for the client and returns a new clientid.

The principal, or principal to user-identifier mapping is taken

from the credential presented in the RPC. As mentioned, the

server will use the credential and associated principal for the

matching with existing clientids. If the client is a traditional

host-based client like a Unix NFS client, then the credential

presented may be the host credential. If the client is a user

level client or lightweight client, the credential used may be the

end user's credential. The client should take care in choosing an

appropriate credential since denial of service attacks could be

attempted by a rogue client that has access to the credential.

ERRORS

NFS4ERR_CLID_INUSE

NFS4ERR_INVAL

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

14.2.34. Operation 36: SETCLIENTID_CONFIRM - Confirm Clientid

SYNOPSIS

setclientid_confirm -> -

ARGUMENT

struct SETCLIENTID_CONFIRM4args {

verifier4 setclientid_confirm;

};

RESULT

struct SETCLIENTID_CONFIRM4res {

nfsstat4 status;

};

DESCRIPTION

This operation is used by the client to confirm the results from a

previous call to SETCLIENTID. The client provides the server

supplied (from a SETCLIENTID response) opaque confirmation

verifier. The server responds with a simple status of success or

failure.

IMPLEMENTATION

The client must use the SETCLIENTID_CONFIRM operation to confirm

its use of client identifier. If the server is holding state for

a client which has presented a new verifier via SETCLIENTID, then

the state will not be released, as described in the section

"Client Failure and Recovery", until a valid SETCLIENTID_CONFIRM

is received. Upon successful confirmation the server will release

the previous state held on behalf of the client. The server

should choose a confirmation cookie value that is reasonably

unique for the client.

ERRORS

NFS4ERR_CLID_INUSE

NFS4ERR_INVAL

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE_CLIENTID

14.2.35. Operation 37: VERIFY - Verify Same Attributes

SYNOPSIS

(cfh), fattr -> -

ARGUMENT

struct VERIFY4args {

/* CURRENT_FH: object */

fattr4 obj_attributes;

};

RESULT

struct VERIFY4res {

nfsstat4 status;

};

DESCRIPTION

The VERIFY operation is used to verify that attributes have a

value assumed by the client before proceeding with following

operations in the compound request. If any of the attributes do

not match then the error NFS4ERR_NOT_SAME must be returned. The

current filehandle retains its value after successful completion

of the operation.

IMPLEMENTATION

One possible use of the VERIFY operation is the following compound

sequence. With this the client is attempting to verify that the

file being removed will match what the client expects to be

removed. This sequence can help prevent the unintended deletion

of a file.

PUTFH (directory filehandle)

LOOKUP (file name)

VERIFY (filehandle == fh)

PUTFH (directory filehandle)

REMOVE (file name)

This sequence does not prevent a second client from removing and

creating a new file in the middle of this sequence but it does

help avoid the unintended result.

In the case that a recommended attribute is specified in the

VERIFY operation and the server does not support that attribute

for the file system object, the error NFS4ERR_NOTSUPP is returned

to the client.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_DELAY

NFS4ERR_FHEXPIRED

NFS4ERR_INVAL

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOTSUPP

NFS4ERR_NOT_SAME

NFS4ERR_RESOURCE

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_WRONGSEC

14.2.36. Operation 38: WRITE - Write to File

SYNOPSIS

(cfh), offset, count, stability, stateid, data -> count, committed,

verifier

ARGUMENT

enum stable_how4 {

UNSTABLE4 = 0,

DATA_SYNC4 = 1,

FILE_SYNC4 = 2

};

struct WRITE4args {

/* CURRENT_FH: file */

stateid4 stateid;

offset4 offset;

stable_how4 stable;

opaque data<>;

};

RESULT

struct WRITE4resok {

count4 count;

stable_how4 committed;

verifier4 writeverf;

};

union WRITE4res switch (nfsstat4 status) {

case NFS4_OK:

WRITE4resok resok4;

default:

void;

};

DESCRIPTION

The WRITE operation is used to write data to a regular file. The

target file is specified by the current filehandle. The offset

specifies the offset where the data should be written. An offset

of 0 (zero) specifies that the write should start at the beginning

of the file. The count represents the number of bytes of data

that are to be written. If the count is 0 (zero), the WRITE will

succeed and return a count of 0 (zero) subject to permissions

checking. The server may choose to write fewer bytes than

requested by the client.

Part of the write request is a specification of how the write is

to be performed. The client specifies with the stable parameter

the method of how the data is to be processed by the server. If

stable is FILE_SYNC4, the server must commit the data written plus

all file system metadata to stable storage before returning

results. This corresponds to the NFS version 2 protocol

semantics. Any other behavior constitutes a protocol violation.

If stable is DATA_SYNC4, then the server must commit all of the

data to stable storage and enough of the metadata to retrieve the

data before returning. The server implementor is free to

implement DATA_SYNC4 in the same fashion as FILE_SYNC4, but with a

possible performance drop. If stable is UNSTABLE4, the server is

free to commit any part of the data and the metadata to stable

storage, including all or none, before returning a reply to the

client. There is no guarantee whether or when any uncommitted data

will subsequently be committed to stable storage. The only

guarantees made by the server are that it will not destroy any

data without changing the value of verf and that it will not

commit the data and metadata at a level less than that requested

by the client.

The stateid returned from a previous record lock or share

reservation request is provided as part of the argument. The

stateid is used by the server to verify that the associated lock

is still valid and to update lease timeouts for the client.

Upon successful completion, the following results are returned.

The count result is the number of bytes of data written to the

file. The server may write fewer bytes than requested. If so, the

actual number of bytes written starting at location, offset, is

returned.

The server also returns an indication of the level of commitment

of the data and metadata via committed. If the server committed

all data and metadata to stable storage, committed should be set

to FILE_SYNC4. If the level of commitment was at least as strong

as DATA_SYNC4, then committed should be set to DATA_SYNC4.

Otherwise, committed must be returned as UNSTABLE4. If stable was

FILE4_SYNC, then committed must also be FILE_SYNC4: anything else

constitutes a protocol violation. If stable was DATA_SYNC4, then

committed may be FILE_SYNC4 or DATA_SYNC4: anything else

constitutes a protocol violation. If stable was UNSTABLE4, then

committed may be either FILE_SYNC4, DATA_SYNC4, or UNSTABLE4.

The final portion of the result is the write verifier, verf. The

write verifier is a cookie that the client can use to determine

whether the server has changed state between a call to WRITE and a

subsequent call to either WRITE or COMMIT. This cookie must be

consistent during a single instance of the NFS version 4 protocol

service and must be unique between instances of the NFS version 4

protocol server, where uncommitted data may be lost.

If a client writes data to the server with the stable argument set

to UNSTABLE4 and the reply yields a committed response of

DATA_SYNC4 or UNSTABLE4, the client will follow up some time in

the future with a COMMIT operation to synchronize outstanding

asynchronous data and metadata with the server's stable storage,

barring client error. It is possible that due to client crash or

other error that a subsequent COMMIT will not be received by the

server.

On success, the current filehandle retains its value.

IMPLEMENTATION

It is possible for the server to write fewer than count bytes of

data. In this case, the server should not return an error unless

no data was written at all. If the server writes less than count

bytes, the client should issue another WRITE to write the

remaining data.

It is assumed that the act of writing data to a file will cause

the time_modified of the file to be updated. However, the

time_modified of the file should not be changed unless the

contents of the file are changed. Thus, a WRITE request with

count set to 0 should not cause the time_modified of the file to

be updated.

The definition of stable storage has been historically a point of

contention. The following expected properties of stable storage

may help in resolving design issues in the implementation. Stable

storage is persistent storage that survives:

1. Repeated power failures.

2. Hardware failures (of any board, power supply, etc.).

3. Repeated software crashes, including reboot cycle.

This definition does not address failure of the stable storage

module itself.

The verifier is defined to allow a client to detect different

instances of an NFS version 4 protocol server over which cached,

uncommitted data may be lost. In the most likely case, the

verifier allows the client to detect server reboots. This

information is required so that the client can safely determine

whether the server could have lost cached data. If the server

fails unexpectedly and the client has uncommitted data from

previous WRITE requests (done with the stable argument set to

UNSTABLE4 and in which the result committed was returned as

UNSTABLE4 as well) it may not have flushed cached data to stable

storage. The burden of recovery is on the client and the client

will need to retransmit the data to the server.

A suggested verifier would be to use the time that the server was

booted or the time the server was last started (if restarting the

server without a reboot results in lost buffers).

The committed field in the results allows the client to do more

effective caching. If the server is committing all WRITE requests

to stable storage, then it should return with committed set to

FILE_SYNC4, regardless of the value of the stable field in the

arguments. A server that uses an NVRAM accelerator may choose to

implement this policy. The client can use this to increase the

effectiveness of the cache by discarding cached data that has

already been committed on the server.

Some implementations may return NFS4ERR_NOSPC instead of

NFS4ERR_DQUOT when a user's quota is exceeded.

ERRORS

NFS4ERR_ACCES

NFS4ERR_BADHANDLE

NFS4ERR_BAD_STATEID

NFS4ERR_DELAY

NFS4ERR_DENIED

NFS4ERR_DQUOT

NFS4ERR_EXPIRED

NFS4ERR_FBIG

NFS4ERR_FHEXPIRED

NFS4ERR_GRACE

NFS4ERR_INVAL

NFS4ERR_IO

NFS4ERR_LEASE_MOVED

NFS4ERR_LOCKED

NFS4ERR_MOVED

NFS4ERR_NOFILEHANDLE

NFS4ERR_NOSPC

NFS4ERR_OLD_STATEID

NFS4ERR_RESOURCE

NFS4ERR_ROFS

NFS4ERR_SERVERFAULT

NFS4ERR_STALE

NFS4ERR_STALE_STATEID

NFS4ERR_WRONGSEC

15. NFS Version 4 Callback Procedures

The procedures used for callbacks are defined in the following

sections. In the interest of clarity, the terms "client" and

"server" refer to NFS clients and servers, despite the fact that for

an individual callback RPC, the sense of these terms would be

precisely the opposite.

15.1. Procedure 0: CB_NULL - No Operation

SYNOPSIS

<null>

ARGUMENT

void;

RESULT

void;

DESCRIPTION

Standard NULL procedure. Void argument, void response. Even

though there is no direct functionality associated with this

procedure, the server will use CB_NULL to confirm the existence of

a path for RPCs from server to client.

ERRORS

None.

15.2. Procedure 1: CB_COMPOUND - Compound Operations

SYNOPSIS

compoundargs -> compoundres

ARGUMENT

enum nfs_cb_opnum4 {

OP_CB_GETATTR = 3,

OP_CB_RECALL = 4 };

union nfs_cb_argop4 switch (unsigned argop) {

case OP_CB_GETATTR: CB_GETATTR4args opcbgetattr;

case OP_CB_RECALL: CB_RECALL4args opcbrecall; };

struct CB_COMPOUND4args {

utf8string tag;

uint32_t minorversion;

nfs_cb_argop4 argarray<>; };

RESULT

union nfs_cb_resop4 switch (unsigned resop){

case OP_CB_GETATTR: CB_GETATTR4res opcbgetattr;

case OP_CB_RECALL: CB_RECALL4res opcbrecall; };

struct CB_COMPOUND4res {

nfsstat4 status;

utf8string tag;

nfs_cb_resop4 resarray<>; };

DESCRIPTION

The CB_COMPOUND procedure is used to combine one or more of the

callback procedures into a single RPC request. The main callback

RPC program has two main procedures: CB_NULL and CB_COMPOUND. All

other operations use the CB_COMPOUND procedure as a wrapper.

In the processing of the CB_COMPOUND procedure, the client may

find that it does not have the available resources to execute any

or all of the operations within the CB_COMPOUND sequence. In this

case, the error NFS4ERR_RESOURCE will be returned for the

particular operation within the CB_COMPOUND procedure where the

resource exhaustion occurred. This assumes that all previous

operations within the CB_COMPOUND sequence have been evaluated

successfully.

Contained within the CB_COMPOUND results is a 'status' field.

This status must be equivalent to the status of the last operation

that was executed within the CB_COMPOUND procedure. Therefore, if

an operation incurred an error then the 'status' value will be the

same error value as is being returned for the operation that

failed.

IMPLEMENTATION

The CB_COMPOUND procedure is used to combine individual operations

into a single RPC request. The client interprets each of the

operations in turn. If an operation is executed by the client and

the status of that operation is NFS4_OK, then the next operation

in the CB_COMPOUND procedure is executed. The client continues

this process until there are no more operations to be executed or

one of the operations has a status value other than NFS4_OK.

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_BAD_STATEID

NFS4ERR_RESOURCE

15.2.1. Operation 3: CB_GETATTR - Get Attributes

SYNOPSIS

fh, attrbits -> attrbits, attrvals

ARGUMENT

struct CB_GETATTR4args {

nfs_fh4 fh;

bitmap4 attr_request;

};

RESULT

struct CB_GETATTR4resok {

fattr4 obj_attributes;

};

union CB_GETATTR4res switch (nfsstat4 status) {

case NFS4_OK:

CB_GETATTR4resok resok4;

default:

void;

};

DESCRIPTION

The CB_GETATTR operation is used to obtain the attributes modified

by an open delegate to allow the server to respond to GETATTR

requests for a file which is the subject of an open delegation.

If the handle specified is not one for which the client holds a

write open delegation, an NFS4ERR_BADHANDLE error is returned.

IMPLEMENTATION

The client returns attrbits and the associated attribute values

only for attributes that it may change (change, time_modify,

object_size).

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_RESOURCE

15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation

SYNOPSIS

stateid, truncate, fh -> status

ARGUMENT

struct CB_RECALL4args {

stateid4 stateid;

bool truncate;

nfs_fh4 fh;

};

RESULT

struct CB_RECALL4res {

nfsstat4 status;

};

DESCRIPTION

The CB_RECALL operation is used to begin the process of recalling

an open delegation and returning it to the server.

The truncate flag is used to optimize recall for a file which is

about to be truncated to zero. When it is set, the client is

freed of obligation to propagate modified data for the file to the

server, since this data is irrelevant.

If the handle specified is not one for which the client holds an

open delegation, an NFS4ERR_BADHANDLE error is returned.

If the stateid specified is not one corresponding to an open

delegation for the file specified by the filehandle, an

NFS4ERR_BAD_STATEID is returned.

IMPLEMENTATION

The client should reply to the callback immediately. Replying

does not complete the recall. The recall is not complete until

the delegation is returned using a DELEGRETURN.

ERRORS

NFS4ERR_BADHANDLE

NFS4ERR_BAD_STATEID

NFS4ERR_RESOURCE

16. Security Considerations

The major security feature to consider is the authentication of the

user making the request of NFS service. Consideration should also be

given to the integrity and privacy of this NFS request. These

specific issues are discussed as part of the section on "RPC and

Security Flavor".

17. IANA Considerations

17.1. Named Attribute Definition

The NFS version 4 protocol provides for the association of named

attributes to files. The name space identifiers for these attributes

are defined as string names. The protocol does not define the

specific assignment of the name space for these file attributes; the

application developer or system vendor is allowed to define the

attribute, its semantics, and the associated name. Even though this

name space will not be specifically controlled to prevent collisions,

the application developer or system vendor is strongly encouraged to

provide the name assignment and associated semantics for attributes

via an Informational RFC. This will provide for interoperability

where common interests exist.

18. RPC definition file

/*

* Copyright (C) The Internet Society (1998,1999,2000).

* All Rights Reserved.

*/

/*

* nfs4_prot.x

*

*/

%#pragma ident "@(#)nfs4_prot.x 1.97 00/06/12"

/*

* Basic typedefs for RFC1832 data type definitions

*/

typedef int int32_t;

typedef unsigned int uint32_t;

typedef hyper int64_t;

typedef unsigned hyper uint64_t;

/*

* Sizes

*/

const NFS4_FHSIZE = 128;

const NFS4_VERIFIER_SIZE = 8;

/*

* File types

*/

enum nfs_ftype4 {

NF4REG = 1, /* Regular File */

NF4DIR = 2, /* Directory */

NF4BLK = 3, /* Special File - block device */

NF4CHR = 4, /* Special File - character device */

NF4LNK = 5, /* Symbolic Link */

NF4SOCK = 6, /* Special File - socket */

NF4FIFO = 7, /* Special File - fifo */

NF4ATTRDIR = 8, /* Attribute Directory */

NF4NAMEDATTR = 9 /* Named Attribute */

};

/*

* Error status

*/

enum nfsstat4 {

NFS4_OK = 0,

NFS4ERR_PERM = 1,

NFS4ERR_NOENT = 2,

NFS4ERR_IO = 5,

NFS4ERR_NXIO = 6,

NFS4ERR_ACCES = 13,

NFS4ERR_EXIST = 17,

NFS4ERR_XDEV = 18,

NFS4ERR_NODEV = 19,

NFS4ERR_NOTDIR = 20,

NFS4ERR_ISDIR = 21,

NFS4ERR_INVAL = 22,

NFS4ERR_FBIG = 27,

NFS4ERR_NOSPC = 28,

NFS4ERR_ROFS = 30,

NFS4ERR_MLINK = 31,

NFS4ERR_NAMETOOLONG = 63,

NFS4ERR_NOTEMPTY = 66,

NFS4ERR_DQUOT = 69,

NFS4ERR_STALE = 70,

NFS4ERR_BADHANDLE = 10001,

NFS4ERR_BAD_COOKIE = 10003,

NFS4ERR_NOTSUPP = 10004,

NFS4ERR_TOOSMALL = 10005,

NFS4ERR_SERVERFAULT = 10006,

NFS4ERR_BADTYPE = 10007,

NFS4ERR_DELAY = 10008,

NFS4ERR_SAME = 10009,/* nverify says attrs same */

NFS4ERR_DENIED = 10010,/* lock unavailable */

NFS4ERR_EXPIRED = 10011,/* lock lease expired */

NFS4ERR_LOCKED = 10012,/* I/O failed due to lock */

NFS4ERR_GRACE = 10013,/* in grace period */

NFS4ERR_FHEXPIRED = 10014,/* file handle expired */

NFS4ERR_SHARE_DENIED = 10015,/* share reserve denied */

NFS4ERR_WRONGSEC = 10016,/* wrong security flavor */

NFS4ERR_CLID_INUSE = 10017,/* clientid in use */

NFS4ERR_RESOURCE = 10018,/* resource exhaustion */

NFS4ERR_MOVED = 10019,/* filesystem relocated */

NFS4ERR_NOFILEHANDLE = 10020,/* current FH is not set */

NFS4ERR_MINOR_VERS_MISMATCH = 10021,/* minor vers not supp */

NFS4ERR_STALE_CLIENTID = 10022,

NFS4ERR_STALE_STATEID = 10023,

NFS4ERR_OLD_STATEID = 10024,

NFS4ERR_BAD_STATEID = 10025,

NFS4ERR_BAD_SEQID = 10026,

NFS4ERR_NOT_SAME = 10027,/* verify - attrs not same */

NFS4ERR_LOCK_RANGE = 10028,

NFS4ERR_SYMLINK = 10029,

NFS4ERR_READDIR_NOSPC = 10030,

NFS4ERR_LEASE_MOVED = 10031

};

/*

* Basic data types

*/

typedef uint32_t bitmap4<>;

typedef uint64_t offset4;

typedef uint32_t count4;

typedef uint64_t length4;

typedef uint64_t clientid4;

typedef uint64_t stateid4;

typedef uint32_t seqid4;

typedef opaque utf8string<>;

typedef utf8string component4;

typedef component4 pathname4<>;

typedef uint64_t nfs_lockid4;

typedef uint64_t nfs_cookie4;

typedef utf8string linktext4;

typedef opaque sec_oid4<>;

typedef uint32_t qop4;

typedef uint32_t mode4;

typedef uint64_t changeid4;

typedef opaque verifier4[NFS4_VERIFIER_SIZE];

/*

* Timeval

*/

struct nfstime4 {

int64_t seconds;

uint32_t nseconds;

};

enum time_how4 {

SET_TO_SERVER_TIME4 = 0,

SET_TO_CLIENT_TIME4 = 1

};

union settime4 switch (time_how4 set_it) {

case SET_TO_CLIENT_TIME4:

nfstime4 time;

default:

void;

};

/*

* File access handle

*/

typedef opaque nfs_fh4<NFS4_FHSIZE>;

/*

* File attribute definitions

*/

/*

* FSID structure for major/minor

*/

struct fsid4 {

uint64_t major;

uint64_t minor;

};

/*

* Filesystem locations attribute for relocation/migration

*/

struct fs_location4 {

utf8string server<>;

pathname4 rootpath;

};

struct fs_locations4 {

pathname4 fs_root;

fs_location4 locations<>;

};

/*

* Various Access Control Entry definitions

*/

/*

* Mask that indicates which Access Control Entries are supported.

* Values for the fattr4_aclsupport attribute.

*/

const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;

const ACL4_SUPPORT_DENY_ACL = 0x00000002;

const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;

const ACL4_SUPPORT_ALARM_ACL = 0x00000008;

typedef uint32_t acetype4;

/*

* acetype4 values, others can be added as needed.

*/

const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;

const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;

const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;

const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;

/*

* ACE flag

*/

typedef uint32_t aceflag4;

/*

* ACE flag values

*/

const ACE4_FILE_INHERIT_ACE = 0x00000001;

const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002;

const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004;

const ACE4_INHERIT_ONLY_ACE = 0x00000008;

const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010;

const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020;

const ACE4_IDENTIFIER_GROUP = 0x00000040;

/*

* ACE mask

*/

typedef uint32_t acemask4;

/*

* ACE mask values

*/

const ACE4_READ_DATA = 0x00000001;

const ACE4_LIST_DIRECTORY = 0x00000001;

const ACE4_WRITE_DATA = 0x00000002;

const ACE4_ADD_FILE = 0x00000002;

const ACE4_APPEND_DATA = 0x00000004;

const ACE4_ADD_SUBDIRECTORY = 0x00000004;

const ACE4_READ_NAMED_ATTRS = 0x00000008;

const ACE4_WRITE_NAMED_ATTRS = 0x00000010;

const ACE4_EXECUTE = 0x00000020;

const ACE4_DELETE_CHILD = 0x00000040;

const ACE4_READ_ATTRIBUTES = 0x00000080;

const ACE4_WRITE_ATTRIBUTES = 0x00000100;

const ACE4_DELETE = 0x00010000;

const ACE4_READ_ACL = 0x00020000;

const ACE4_WRITE_ACL = 0x00040000;

const ACE4_WRITE_OWNER = 0x00080000;

const ACE4_SYNCHRONIZE = 0x00100000;

/*

* ACE4_GENERIC_READ -- defined as combination of

* ACE4_READ_ACL

* ACE4_READ_DATA

* ACE4_READ_ATTRIBUTES

* ACE4_SYNCHRONIZE

*/

const ACE4_GENERIC_READ = 0x00120081;

/*

* ACE4_GENERIC_WRITE -- defined as combination of

* ACE4_READ_ACL

* ACE4_WRITE_DATA

* ACE4_WRITE_ATTRIBUTES

* ACE4_WRITE_ACL

* ACE4_APPEND_DATA

* ACE4_SYNCHRONIZE

*/

const ACE4_GENERIC_WRITE = 0x00160106;

/*

* ACE4_GENERIC_EXECUTE -- defined as combination of

* ACE4_READ_ACL

* ACE4_READ_ATTRIBUTES

* ACE4_EXECUTE

* ACE4_SYNCHRONIZE

*/

const ACE4_GENERIC_EXECUTE = 0x001200A0;

/*

* Access Control Entry definition

*/

struct nfsace4 {

acetype4 type;

aceflag4 flag;

acemask4 access_mask;

utf8string who;

};

/*

* Special data/attribute associated with

* file types NF4BLK and NF4CHR.

*/

struct specdata4 {

uint32_t specdata1;

uint32_t specdata2;

};

/*

* Values for fattr4_fh_expire_type

*/

const FH4_PERSISTENT = 0x00000000;

const FH4_NOEXPIRE_WITH_OPEN = 0x00000001;

const FH4_VOLATILE_ANY = 0x00000002;

const FH4_VOL_MIGRATION = 0x00000004;

const FH4_VOL_RENAME = 0x00000008;

typedef bitmap4 fattr4_supported_attrs;

typedef nfs_ftype4 fattr4_type;

typedef uint32_t fattr4_fh_expire_type;

typedef changeid4 fattr4_change;

typedef uint64_t fattr4_size;

typedef bool fattr4_link_support;

typedef bool fattr4_symlink_support;

typedef bool fattr4_named_attr;

typedef fsid4 fattr4_fsid;

typedef bool fattr4_unique_handles;

typedef uint32_t fattr4_lease_time;

typedef nfsstat4 fattr4_rdattr_error;

typedef nfsace4 fattr4_acl<>;

typedef uint32_t fattr4_aclsupport;

typedef bool fattr4_archive;

typedef bool fattr4_cansettime;

typedef bool fattr4_case_insensitive;

typedef bool fattr4_case_preserving;

typedef bool fattr4_chown_restricted;

typedef uint64_t fattr4_fileid;

typedef uint64_t fattr4_files_avail;

typedef nfs_fh4 fattr4_filehandle;

typedef uint64_t fattr4_files_free;

typedef uint64_t fattr4_files_total;

typedef fs_locations4 fattr4_fs_locations;

typedef bool fattr4_hidden;

typedef bool fattr4_homogeneous;

typedef uint64_t fattr4_maxfilesize;

typedef uint32_t fattr4_maxlink;

typedef uint32_t fattr4_maxname;

typedef uint64_t fattr4_maxread;

typedef uint64_t fattr4_maxwrite;

typedef utf8string fattr4_mimetype;

typedef mode4 fattr4_mode;

typedef bool fattr4_no_trunc;

typedef uint32_t fattr4_numlinks;

typedef utf8string fattr4_owner;

typedef utf8string fattr4_owner_group;

typedef uint64_t fattr4_quota_avail_hard;

typedef uint64_t fattr4_quota_avail_soft;

typedef uint64_t fattr4_quota_used;

typedef specdata4 fattr4_rawdev;

typedef uint64_t fattr4_space_avail;

typedef uint64_t fattr4_space_free;

typedef uint64_t fattr4_space_total;

typedef uint64_t fattr4_space_used;

typedef bool fattr4_system;

typedef nfstime4 fattr4_time_access;

typedef settime4 fattr4_time_access_set;

typedef nfstime4 fattr4_time_backup;

typedef nfstime4 fattr4_time_create;

typedef nfstime4 fattr4_time_delta;

typedef nfstime4 fattr4_time_metadata;

typedef nfstime4 fattr4_time_modify;

typedef settime4 fattr4_time_modify_set;

/*

* Mandatory Attributes

*/

const FATTR4_SUPPORTED_ATTRS = 0;

const FATTR4_TYPE = 1;

const FATTR4_FH_EXPIRE_TYPE = 2;

const FATTR4_CHANGE = 3;

const FATTR4_SIZE = 4;

const FATTR4_LINK_SUPPORT = 5;

const FATTR4_SYMLINK_SUPPORT = 6;

const FATTR4_NAMED_ATTR = 7;

const FATTR4_FSID = 8;

const FATTR4_UNIQUE_HANDLES = 9;

const FATTR4_LEASE_TIME = 10;

const FATTR4_RDATTR_ERROR = 11;

/*

* Recommended Attributes

*/

const FATTR4_ACL = 12;

const FATTR4_ACLSUPPORT = 13;

const FATTR4_ARCHIVE = 14;

const FATTR4_CANSETTIME = 15;

const FATTR4_CASE_INSENSITIVE = 16;

const FATTR4_CASE_PRESERVING = 17;

const FATTR4_CHOWN_RESTRICTED = 18;

const FATTR4_FILEHANDLE = 19;

const FATTR4_FILEID = 20;

const FATTR4_FILES_AVAIL = 21;

const FATTR4_FILES_FREE = 22;

const FATTR4_FILES_TOTAL = 23;

const FATTR4_FS_LOCATIONS = 24;

const FATTR4_HIDDEN = 25;

const FATTR4_HOMOGENEOUS = 26;

const FATTR4_MAXFILESIZE = 27;

const FATTR4_MAXLINK = 28;

const FATTR4_MAXNAME = 29;

const FATTR4_MAXREAD = 30;

const FATTR4_MAXWRITE = 31;

const FATTR4_MIMETYPE = 32;

const FATTR4_MODE = 33;

const FATTR4_NO_TRUNC = 34;

const FATTR4_NUMLINKS = 35;

const FATTR4_OWNER = 36;

const FATTR4_OWNER_GROUP = 37;

const FATTR4_QUOTA_AVAIL_HARD = 38;

const FATTR4_QUOTA_AVAIL_SOFT = 39;

const FATTR4_QUOTA_USED = 40;

const FATTR4_RAWDEV = 41;

const FATTR4_SPACE_AVAIL = 42;

const FATTR4_SPACE_FREE = 43;

const FATTR4_SPACE_TOTAL = 44;

const FATTR4_SPACE_USED = 45;

const FATTR4_SYSTEM = 46;

const FATTR4_TIME_ACCESS = 47;

const FATTR4_TIME_ACCESS_SET = 48;

const FATTR4_TIME_BACKUP = 49;

const FATTR4_TIME_CREATE = 50;

const FATTR4_TIME_DELTA = 51;

const FATTR4_TIME_METADATA = 52;

const FATTR4_TIME_MODIFY = 53;

const FATTR4_TIME_MODIFY_SET = 54;

typedef opaque attrlist4<>;

/*

* File attribute container

*/

struct fattr4 {

bitmap4 attrmask;

attrlist4 attr_vals;

};

/*

* Change info for the client

*/

struct change_info4 {

bool atomic;

changeid4 before;

changeid4 after;

};

struct clientaddr4 {

/* see struct rpcb in RFC1833 */

string r_netid<>; /* network id */

string r_addr<>; /* universal address */

};

/*

* Callback program info as provided by the client

*/

struct cb_client4 {

unsigned int cb_program;

clientaddr4 cb_location;

};

/*

* Client ID

*/

struct nfs_client_id4 {

verifier4 verifier;

opaque id<>;

};

struct nfs_lockowner4 {

clientid4 clientid;

opaque owner<>;

};

enum nfs_lock_type4 {

READ_LT = 1,

WRITE_LT = 2,

READW_LT = 3, /* blocking read */

WRITEW_LT = 4 /* blocking write */

};

/*

* ACCESS: Check access permission

*/

const ACCESS4_READ = 0x00000001;

const ACCESS4_LOOKUP = 0x00000002;

const ACCESS4_MODIFY = 0x00000004;

const ACCESS4_EXTEND = 0x00000008;

const ACCESS4_DELETE = 0x00000010;

const ACCESS4_EXECUTE = 0x00000020;

struct ACCESS4args {

/* CURRENT_FH: object */

uint32_t access;

};

struct ACCESS4resok {

uint32_t supported;

uint32_t access;

};

union ACCESS4res switch (nfsstat4 status) {

case NFS4_OK:

ACCESS4resok resok4;

default:

void;

};

/*

* CLOSE: Close a file and release share locks

*/

struct CLOSE4args {

/* CURRENT_FH: object */

seqid4 seqid;

stateid4 stateid;

};

union CLOSE4res switch (nfsstat4 status) {

case NFS4_OK:

stateid4 stateid;

default:

void;

};

/*

* COMMIT: Commit cached data on server to stable storage

*/

struct COMMIT4args {

/* CURRENT_FH: file */

offset4 offset;

count4 count;

};

struct COMMIT4resok {

verifier4 writeverf;

};

union COMMIT4res switch (nfsstat4 status) {

case NFS4_OK:

COMMIT4resok resok4;

default:

void;

};

/*

* CREATE: Create a file

*/

union createtype4 switch (nfs_ftype4 type) {

case NF4LNK:

linktext4 linkdata;

case NF4BLK:

case NF4CHR:

specdata4 devdata;

case NF4SOCK:

case NF4FIFO:

case NF4DIR:

void;

};

struct CREATE4args {

/* CURRENT_FH: directory for creation */

component4 objname;

createtype4 objtype;

};

struct CREATE4resok {

change_info4 cinfo;

};

union CREATE4res switch (nfsstat4 status) {

case NFS4_OK:

CREATE4resok resok4;

default:

void;

};

/*

* DELEGPURGE: Purge Delegations Awaiting Recovery

*/

struct DELEGPURGE4args {

clientid4 clientid;

};

struct DELEGPURGE4res {

nfsstat4 status;

};

/*

* DELEGRETURN: Return a delegation

*/

struct DELEGRETURN4args {

stateid4 stateid;

};

struct DELEGRETURN4res {

nfsstat4 status;

};

/*

* GETATTR: Get file attributes

*/

struct GETATTR4args {

/* CURRENT_FH: directory or file */

bitmap4 attr_request;

};

struct GETATTR4resok {

fattr4 obj_attributes;

};

union GETATTR4res switch (nfsstat4 status) {

case NFS4_OK:

GETATTR4resok resok4;

default:

void;

};

/*

* GETFH: Get current filehandle

*/

struct GETFH4resok {

nfs_fh4 object;

};

union GETFH4res switch (nfsstat4 status) {

case NFS4_OK:

GETFH4resok resok4;

default:

void;

};

/*

* LINK: Create link to an object

*/

struct LINK4args {

/* SAVED_FH: source object */

/* CURRENT_FH: target directory */

component4 newname;

};

struct LINK4resok {

change_info4 cinfo;

};

union LINK4res switch (nfsstat4 status) {

case NFS4_OK:

LINK4resok resok4;

default:

void;

};

/*

* LOCK/LOCKT/LOCKU: Record lock management

*/

struct LOCK4args {

/* CURRENT_FH: file */

nfs_lock_type4 locktype;

seqid4 seqid;

bool reclaim;

stateid4 stateid;

offset4 offset;

length4 length;

};

struct LOCK4denied {

nfs_lockowner4 owner;

offset4 offset;

length4 length;

};

union LOCK4res switch (nfsstat4 status) {

case NFS4_OK:

stateid4 stateid;

case NFS4ERR_DENIED:

LOCK4denied denied;

default:

void;

};

struct LOCKT4args {

/* CURRENT_FH: file */

nfs_lock_type4 locktype;

nfs_lockowner4 owner;

offset4 offset;

length4 length;

};

union LOCKT4res switch (nfsstat4 status) {

case NFS4ERR_DENIED:

LOCK4denied denied;

case NFS4_OK:

void;

default:

void;

};

struct LOCKU4args {

/* CURRENT_FH: file */

nfs_lock_type4 locktype;

seqid4 seqid;

stateid4 stateid;

offset4 offset;

length4 length;

};

union LOCKU4res switch (nfsstat4 status) {

case NFS4_OK:

stateid4 stateid;

default:

void;

};

/*

* LOOKUP: Lookup filename

*/

struct LOOKUP4args {

/* CURRENT_FH: directory */

pathname4 path;

};

struct LOOKUP4res {

/* CURRENT_FH: object */

nfsstat4 status;

};

/*

* LOOKUPP: Lookup parent directory

*/

struct LOOKUPP4res {

/* CURRENT_FH: directory */

nfsstat4 status;

};

/*

* NVERIFY: Verify attributes different

*/

struct NVERIFY4args {

/* CURRENT_FH: object */

fattr4 obj_attributes;

};

struct NVERIFY4res {

nfsstat4 status;

};

/*

* Various definitions for OPEN

*/

enum createmode4 {

UNCHECKED4 = 0,

GUARDED4 = 1,

EXCLUSIVE4 = 2

};

union createhow4 switch (createmode4 mode) {

case UNCHECKED4:

case GUARDED4:

fattr4 createattrs;

case EXCLUSIVE4:

verifier4 createverf;

};

enum opentype4 {

OPEN4_NOCREATE = 0,

OPEN4_CREATE = 1

};

union openflag4 switch (opentype4 opentype) {

case OPEN4_CREATE:

createhow4 how;

default:

void;

};

/* Next definitions used for OPEN delegation */

enum limit_by4 {

NFS_LIMIT_SIZE = 1,

NFS_LIMIT_BLOCKS = 2

/* others as needed */

};

struct nfs_modified_limit4 {

uint32_t num_blocks;

uint32_t bytes_per_block;

};

union nfs_space_limit4 switch (limit_by4 limitby) {

/* limit specified as file size */

case NFS_LIMIT_SIZE:

uint64_t filesize;

/* limit specified by number of blocks */

case NFS_LIMIT_BLOCKS:

nfs_modified_limit4 mod_blocks;

} ;

/*

* Share Access and Deny constants for open argument

*/

const OPEN4_SHARE_ACCESS_READ = 0x00000001;

const OPEN4_SHARE_ACCESS_WRITE = 0x00000002;

const OPEN4_SHARE_ACCESS_BOTH = 0x00000003;

const OPEN4_SHARE_DENY_NONE = 0x00000000;

const OPEN4_SHARE_DENY_READ = 0x00000001;

const OPEN4_SHARE_DENY_WRITE = 0x00000002;

const OPEN4_SHARE_DENY_BOTH = 0x00000003;

enum open_delegation_type4 {

OPEN_DELEGATE_NONE = 0,

OPEN_DELEGATE_READ = 1,

OPEN_DELEGATE_WRITE = 2

};

enum open_claim_type4 {

CLAIM_NULL = 0,

CLAIM_PREVIOUS = 1,

CLAIM_DELEGATE_CUR = 2,

CLAIM_DELEGATE_PREV = 3

};

struct open_claim_delegate_cur4 {

pathname4 file;

stateid4 delegate_stateid;

};

union open_claim4 switch (open_claim_type4 claim) {

/*

* No special rights to file. Ordinary OPEN of the specified file.

*/

case CLAIM_NULL:

/* CURRENT_FH: directory */

pathname4 file;

/*

* Right to the file established by an open previous to server

* reboot. File identified by filehandle obtained at that time

* rather than by name.

*/

case CLAIM_PREVIOUS:

/* CURRENT_FH: file being reclaimed */

uint32_t delegate_type;

/*

* Right to file based on a delegation granted by the server.

* File is specified by name.

*/

case CLAIM_DELEGATE_CUR:

/* CURRENT_FH: directory */

open_claim_delegate_cur4 delegate_cur_info;

/* Right to file based on a delegation granted to a previous boot

* instance of the client. File is specified by name.

*/

case CLAIM_DELEGATE_PREV:

/* CURRENT_FH: directory */

pathname4 file_delegate_prev;

};

/*

* OPEN: Open a file, potentially receiving an open delegation

*/

struct OPEN4args {

open_claim4 claim;

openflag4 openhow;

nfs_lockowner4 owner;

seqid4 seqid;

uint32_t share_access;

uint32_t share_deny;

};

struct open_read_delegation4 {

stateid4 stateid; /* Stateid for delegation*/

bool recall; /* Pre-recalled flag for

delegations obtained

by reclaim

(CLAIM_PREVIOUS) */

nfsace4 permissions; /* Defines users who don't

need an ACCESS call to

open for read */

};

struct open_write_delegation4 {

stateid4 stateid; /* Stateid for delegation */

bool recall; /* Pre-recalled flag for

delegations obtained

by reclaim

(CLAIM_PREVIOUS) */

nfs_space_limit4 space_limit; /* Defines condition that

the client must check to

determine whether the

file needs to be flushed

to the server on close.

*/

nfsace4 permissions; /* Defines users who don't

need an ACCESS call as

part of a delegated

open. */

};

union open_delegation4

switch (open_delegation_type4 delegation_type) {

case OPEN_DELEGATE_NONE:

void;

case OPEN_DELEGATE_READ:

open_read_delegation4 read;

case OPEN_DELEGATE_WRITE:

open_write_delegation4 write;

};

/*

* Result flags

*/

/* Mandatory locking is in effect for this file. */

const OPEN4_RESULT_MLOCK = 0x00000001;

/* Client must confirm open */

const OPEN4_RESULT_CONFIRM = 0x00000002;

struct OPEN4resok {

stateid4 stateid; /* Stateid for open */

change_info4 cinfo; /* Directory Change Info */

uint32_t rflags; /* Result flags */

verifier4 open_confirm; /* OPEN_CONFIRM verifier */

open_delegation4 delegation; /* Info on any open

delegation */

};

union OPEN4res switch (nfsstat4 status) {

case NFS4_OK:

/* CURRENT_FH: opened file */

OPEN4resok resok4;

default:

void;

};

/*

* OPENATTR: open named attributes directory

*/

struct OPENATTR4res {

/* CURRENT_FH: name attr directory*/

nfsstat4 status;

};

/*

* OPEN_CONFIRM: confirm the open

*/

struct OPEN_CONFIRM4args {

/* CURRENT_FH: opened file */

seqid4 seqid;

verifier4 open_confirm; /* OPEN_CONFIRM verifier */

};

struct OPEN_CONFIRM4resok {

stateid4 stateid;

};

union OPEN_CONFIRM4res switch (nfsstat4 status) {

case NFS4_OK:

OPEN_CONFIRM4resok resok4;

default:

void;

};

/*

* OPEN_DOWNGRADE: downgrade the access/deny for a file

*/

struct OPEN_DOWNGRADE4args {

/* CURRENT_FH: opened file */

stateid4 stateid;

seqid4 seqid;

uint32_t share_access;

uint32_t share_deny;

};

struct OPEN_DOWNGRADE4resok {

stateid4 stateid;

};

union OPEN_DOWNGRADE4res switch(nfsstat4 status) {

case NFS4_OK:

OPEN_DOWNGRADE4resok resok4;

default:

void;

};

/*

* PUTFH: Set current filehandle

*/

struct PUTFH4args {

nfs_fh4 object;

};

struct PUTFH4res {

/* CURRENT_FH: */

nfsstat4 status;

};

/*

* PUTPUBFH: Set public filehandle

*/

struct PUTPUBFH4res {

/* CURRENT_FH: public fh */

nfsstat4 status;

};

/*

* PUTROOTFH: Set root filehandle

*/

struct PUTROOTFH4res {

/* CURRENT_FH: root fh */

nfsstat4 status;

};

/*

* READ: Read from file

*/

struct READ4args {

/* CURRENT_FH: file */

stateid4 stateid;

offset4 offset;

count4 count;

};

struct READ4resok {

bool eof;

opaque data<>;

};

union READ4res switch (nfsstat4 status) {

case NFS4_OK:

READ4resok resok4;

default:

void;

};

/*

* READDIR: Read directory

*/

struct READDIR4args {

/* CURRENT_FH: directory */

nfs_cookie4 cookie;

verifier4 cookieverf;

count4 dircount;

count4 maxcount;

bitmap4 attr_request;

};

struct entry4 {

nfs_cookie4 cookie;

component4 name;

fattr4 attrs;

entry4 *nextentry;

};

struct dirlist4 {

entry4 *entries;

bool eof;

};

struct READDIR4resok {

verifier4 cookieverf;

dirlist4 reply;

};

union READDIR4res switch (nfsstat4 status) {

case NFS4_OK:

READDIR4resok resok4;

default:

void;

};

/*

* READLINK: Read symbolic link

*/

struct READLINK4resok {

linktext4 link;

};

union READLINK4res switch (nfsstat4 status) {

case NFS4_OK:

READLINK4resok resok4;

default:

void;

};

/*

* REMOVE: Remove filesystem object

*/

struct REMOVE4args {

/* CURRENT_FH: directory */

component4 target;

};

struct REMOVE4resok {

change_info4 cinfo;

};

union REMOVE4res switch (nfsstat4 status) {

case NFS4_OK:

REMOVE4resok resok4;

default:

void;

};

/*

* RENAME: Rename directory entry

*/

struct RENAME4args {

/* SAVED_FH: source directory */

component4 oldname;

/* CURRENT_FH: target directory */

component4 newname;

};

struct RENAME4resok {

change_info4 source_cinfo;

change_info4 target_cinfo;

};

union RENAME4res switch (nfsstat4 status) {

case NFS4_OK:

RENAME4resok resok4;

default:

void;

};

/*

* RENEW: Renew a Lease

*/

struct RENEW4args {

stateid4 stateid;

};

struct RENEW4res {

nfsstat4 status;

};

/*

* RESTOREFH: Restore saved filehandle

*/

struct RESTOREFH4res {

/* CURRENT_FH: value of saved fh */

nfsstat4 status;

};

/*

* SAVEFH: Save current filehandle

*/

struct SAVEFH4res {

/* SAVED_FH: value of current fh */

nfsstat4 status;

};

/*

* SECINFO: Obtain Available Security Mechanisms

*/

struct SECINFO4args {

/* CURRENT_FH: */

component4 name;

};

/*

* From RFC2203

*/

enum rpc_gss_svc_t {

RPC_GSS_SVC_NONE = 1,

RPC_GSS_SVC_INTEGRITY = 2,

RPC_GSS_SVC_PRIVACY = 3

};

struct rpcsec_gss_info {

sec_oid4 oid;

qop4 qop;

rpc_gss_svc_t service;

};

struct secinfo4 {

uint32_t flavor;

/* null for AUTH_SYS, AUTH_NONE;

contains rpcsec_gss_info for

RPCSEC_GSS. */

opaque flavor_info<>;

};

typedef secinfo4 SECINFO4resok<>;

union SECINFO4res switch (nfsstat4 status) {

case NFS4_OK:

SECINFO4resok resok4;

default:

void;

};

/*

* SETATTR: Set attributes

*/

struct SETATTR4args {

/* CURRENT_FH: target object */

stateid4 stateid;

fattr4 obj_attributes;

};

struct SETATTR4res {

nfsstat4 status;

bitmap4 attrsset;

};

/*

* SETCLIENTID

*/

struct SETCLIENTID4args {

nfs_client_id4 client;

cb_client4 callback;

};

struct SETCLIENTID4resok {

clientid4 clientid;

verifier4 setclientid_confirm;

};

union SETCLIENTID4res switch (nfsstat4 status) {

case NFS4_OK:

SETCLIENTID4resok resok4;

case NFS4ERR_CLID_INUSE:

clientaddr4 client_using;

default:

void;

};

struct SETCLIENTID_CONFIRM4args {

verifier4 setclientid_confirm;

};

struct SETCLIENTID_CONFIRM4res {

nfsstat4 status;

};

/*

* VERIFY: Verify attributes same

*/

struct VERIFY4args {

/* CURRENT_FH: object */

fattr4 obj_attributes;

};

struct VERIFY4res {

nfsstat4 status;

};

/*

* WRITE: Write to file

*/

enum stable_how4 {

UNSTABLE4 = 0,

DATA_SYNC4 = 1,

FILE_SYNC4 = 2

};

struct WRITE4args {

/* CURRENT_FH: file */

stateid4 stateid;

offset4 offset;

stable_how4 stable;

opaque data<>;

};

struct WRITE4resok {

count4 count;

stable_how4 committed;

verifier4 writeverf;

};

union WRITE4res switch (nfsstat4 status) {

case NFS4_OK:

WRITE4resok resok4;

default:

void;

};

/*

* Operation arrays

*/

enum nfs_opnum4 {

OP_ACCESS = 3,

OP_CLOSE = 4,

OP_COMMIT = 5,

OP_CREATE = 6,

OP_DELEGPURGE = 7,

OP_DELEGRETURN = 8,

OP_GETATTR = 9,

OP_GETFH = 10,

OP_LINK = 11,

OP_LOCK = 12,

OP_LOCKT = 13,

OP_LOCKU = 14,

OP_LOOKUP = 15,

OP_LOOKUPP = 16,

OP_NVERIFY = 17,

OP_OPEN = 18,

OP_OPENATTR = 19,

OP_OPEN_CONFIRM = 20,

OP_OPEN_DOWNGRADE = 21,

OP_PUTFH = 22,

OP_PUTPUBFH = 23,

OP_PUTROOTFH = 24,

OP_READ = 25,

OP_READDIR = 26,

OP_READLINK = 27,

OP_REMOVE = 28,

OP_RENAME = 29,

OP_RENEW = 30,

OP_RESTOREFH = 31,

OP_SAVEFH = 32,

OP_SECINFO = 33,

OP_SETATTR = 34,

OP_SETCLIENTID = 35,

OP_SETCLIENTID_CONFIRM = 36,

OP_VERIFY = 37,

OP_WRITE = 38

};

union nfs_argop4 switch (nfs_opnum4 argop) {

case OP_ACCESS: ACCESS4args opaccess;

case OP_CLOSE: CLOSE4args opclose;

case OP_COMMIT: COMMIT4args opcommit;

case OP_CREATE: CREATE4args opcreate;

case OP_DELEGPURGE: DELEGPURGE4args opdelegpurge;

case OP_DELEGRETURN: DELEGRETURN4args opdelegreturn;

case OP_GETATTR: GETATTR4args opgetattr;

case OP_GETFH: void;

case OP_LINK: LINK4args oplink;

case OP_LOCK: LOCK4args oplock;

case OP_LOCKT: LOCKT4args oplockt;

case OP_LOCKU: LOCKU4args oplocku;

case OP_LOOKUP: LOOKUP4args oplookup;

case OP_LOOKUPP: void;

case OP_NVERIFY: NVERIFY4args opnverify;

case OP_OPEN: OPEN4args opopen;

case OP_OPENATTR: void;

case OP_OPEN_CONFIRM: OPEN_CONFIRM4args opopen_confirm;

case OP_OPEN_DOWNGRADE: OPEN_DOWNGRADE4args opopen_downgrade;

case OP_PUTFH: PUTFH4args opputfh;

case OP_PUTPUBFH: void;

case OP_PUTROOTFH: void;

case OP_READ: READ4args opread;

case OP_READDIR: READDIR4args opreaddir;

case OP_READLINK: void;

case OP_REMOVE: REMOVE4args opremove;

case OP_RENAME: RENAME4args oprename;

case OP_RENEW: RENEW4args oprenew;

case OP_RESTOREFH: void;

case OP_SAVEFH: void;

case OP_SECINFO: SECINFO4args opsecinfo;

case OP_SETATTR: SETATTR4args opsetattr;

case OP_SETCLIENTID: SETCLIENTID4args opsetclientid;

case OP_SETCLIENTID_CONFIRM: SETCLIENTID_CONFIRM4args

opsetclientid_confirm;

case OP_VERIFY: VERIFY4args opverify;

case OP_WRITE: WRITE4args opwrite;

};

union nfs_resop4 switch (nfs_opnum4 resop){

case OP_ACCESS: ACCESS4res opaccess;

case OP_CLOSE: CLOSE4res opclose;

case OP_COMMIT: COMMIT4res opcommit;

case OP_CREATE: CREATE4res opcreate;

case OP_DELEGPURGE: DELEGPURGE4res opdelegpurge;

case OP_DELEGRETURN: DELEGRETURN4res opdelegreturn;

case OP_GETATTR: GETATTR4res opgetattr;

case OP_GETFH: GETFH4res opgetfh;

case OP_LINK: LINK4res oplink;

case OP_LOCK: LOCK4res oplock;

case OP_LOCKT: LOCKT4res oplockt;

case OP_LOCKU: LOCKU4res oplocku;

case OP_LOOKUP: LOOKUP4res oplookup;

case OP_LOOKUPP: LOOKUPP4res oplookupp;

case OP_NVERIFY: NVERIFY4res opnverify;

case OP_OPEN: OPEN4res opopen;

case OP_OPENATTR: OPENATTR4res opopenattr;

case OP_OPEN_CONFIRM: OPEN_CONFIRM4res opopen_confirm;

case OP_OPEN_DOWNGRADE: OPEN_DOWNGRADE4res opopen_downgrade;

case OP_PUTFH: PUTFH4res opputfh;

case OP_PUTPUBFH: PUTPUBFH4res opputpubfh;

case OP_PUTROOTFH: PUTROOTFH4res opputrootfh;

case OP_READ: READ4res opread;

case OP_READDIR: READDIR4res opreaddir;

case OP_READLINK: READLINK4res opreadlink;

case OP_REMOVE: REMOVE4res opremove;

case OP_RENAME: RENAME4res oprename;

case OP_RENEW: RENEW4res oprenew;

case OP_RESTOREFH: RESTOREFH4res oprestorefh;

case OP_SAVEFH: SAVEFH4res opsavefh;

case OP_SECINFO: SECINFO4res opsecinfo;

case OP_SETATTR: SETATTR4res opsetattr;

case OP_SETCLIENTID: SETCLIENTID4res opsetclientid;

case OP_SETCLIENTID_CONFIRM: SETCLIENTID_CONFIRM4res

opsetclientid_confirm;

case OP_VERIFY: VERIFY4res opverify;

case OP_WRITE: WRITE4res opwrite;

};

struct COMPOUND4args {

utf8string tag;

uint32_t minorversion;

nfs_argop4 argarray<>;

};

struct COMPOUND4res {

nfsstat4 status;

utf8string tag;

nfs_resop4 resarray<>;

};

/*

* Remote file service routines

*/

program NFS4_PROGRAM {

version NFS_V4 {

void

NFSPROC4_NULL(void) = 0;

COMPOUND4res

NFSPROC4_COMPOUND(COMPOUND4args) = 1;

} = 4;

} = 100003;

/*

* NFS4 Callback Procedure Definitions and Program

*/

/*

* CB_GETATTR: Get Current Attributes

*/

struct CB_GETATTR4args {

nfs_fh4 fh;

bitmap4 attr_request;

};

struct CB_GETATTR4resok {

fattr4 obj_attributes;

};

union CB_GETATTR4res switch (nfsstat4 status) {

case NFS4_OK:

CB_GETATTR4resok resok4;

default:

void;

};

/*

* CB_RECALL: Recall an Open Delegation

*/

struct CB_RECALL4args {

stateid4 stateid;

bool truncate;

nfs_fh4 fh;

};

struct CB_RECALL4res {

nfsstat4 status;

};

/*

* Various definitions for CB_COMPOUND

*/

enum nfs_cb_opnum4 {

OP_CB_GETATTR = 3,

OP_CB_RECALL = 4

};

union nfs_cb_argop4 switch (unsigned argop) {

case OP_CB_GETATTR: CB_GETATTR4args opcbgetattr;

case OP_CB_RECALL: CB_RECALL4args opcbrecall;

};

union nfs_cb_resop4 switch (unsigned resop){

case OP_CB_GETATTR: CB_GETATTR4res opcbgetattr;

case OP_CB_RECALL: CB_RECALL4res opcbrecall;

};

struct CB_COMPOUND4args {

utf8string tag;

uint32_t minorversion;

nfs_cb_argop4 argarray<>;

};

struct CB_COMPOUND4res {

nfsstat4 status;

utf8string tag;

nfs_cb_resop4 resarray<>;

};

/*

* Program number is in the transient range since the client

* will assign the exact transient program number and provide

* that to the server via the SETCLIENTID operation.

*/

program NFS4_CALLBACK {

version NFS_CB {

void

CB_NULL(void) = 0;

CB_COMPOUND4res

CB_COMPOUND(CB_COMPOUND4args) = 1;

} = 1;

} = 40000000;

19. Bibliography

[Floyd] S. Floyd, V. Jacobson, "The Synchronization of Periodic

Routing Messages," IEEE/ACM Transactions on Networking,

2(2), pp. 122-136, April 1994.

[Gray] C. Gray, D. Cheriton, "Leases: An Efficient Fault-

Tolerant Mechanism for Distributed File Cache

Consistency," Proceedings of the Twelfth Symposium on

Operating Systems Principles, p. 202-210, December 1989.

[ISO10646] "ISO/IEC 10646-1:1993. International Standard --

Information technology -- Universal Multiple-Octet Coded

Character Set (UCS) -- Part 1: Architecture and Basic

Multilingual Plane."

[Juszczak] Juszczak, Chet, "Improving the Performance and

Correctness of an NFS Server," USENIX Conference

Proceedings, USENIX Association, Berkeley, CA, June

1990, pages 53-63. Describes reply cache implementation

that avoids work in the server by handling duplicate

requests. More important, though listed as a side-

effect, the reply cache aids in the avoidance of

destructive non-idempotent operation re-application --

improving correctness.

[Kazar] Kazar, Michael Leon, "Synchronization and Caching Issues

in the Andrew File System," USENIX Conference

Proceedings, USENIX Association, Berkeley, CA, Dallas

Winter 1988, pages 27-36. A description of the cache

consistency scheme in AFS. Contrasted with other

distributed file systems.

[Macklem] Macklem, Rick, "Lessons Learned Tuning the 4.3BSD Reno

Implementation of the NFS Protocol," Winter USENIX

Conference Proceedings, USENIX Association, Berkeley,

CA, January 1991. Describes performance work in tuning

the 4.3BSD Reno NFS implementation. Describes

performance improvement (reduced CPU loading) through

elimination of data copies.

[Mogul] Mogul, Jeffrey C., "A Recovery Protocol for Spritely

NFS," USENIX File System Workshop Proceedings, Ann

Arbor, MI, USENIX Association, Berkeley, CA, May 1992.

Second paper on Spritely NFS proposes a lease-based

scheme for recovering state of consistency protocol.

[Nowicki] Nowicki, Bill, "Transport Issues in the Network File

System," ACM SIGCOMM newsletter Computer Communication

Review, April 1989. A brief description of the basis

for the dynamic retransmission work.

[Pawlowski] Pawlowski, Brian, Ron Hixon, Mark Stein, Joseph

Tumminaro, "Network Computing in the UNIX and IBM

Mainframe Environment," Uniforum `89 Conf. Proc.,

(1989) Description of an NFS server implementation for

IBM's MVS operating system.

[RFC1094] Sun Microsystems, Inc., "NFS: Network File System

Protocol Specification", RFC1094, March 1989.

[RFC1345] Simonsen, K., "Character Mnemonics & Character Sets",

RFC1345, June 1992.

[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2,

RFC1700, October 1994.

[RFC1813] Callaghan, B., Pawlowski, B. and P. Staubach, "NFS

Version 3 Protocol Specification", RFC1813, June 1995.

[RFC1831] Srinivasan, R., "RPC: Remote Procedure Call Protocol

Specification Version 2", RFC1831, August 1995.

[RFC1832] Srinivasan, R., "XDR: External Data Representation

Standard", RFC1832, August 1995.

[RFC1833] Srinivasan, R., "Binding Protocols for ONC RPC Version

2", RFC1833, August 1995.

[RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism

(SPKM)", RFC2025, October 1996.

[RFC2054] Callaghan, B., "WebNFS Client Specification", RFC2054,

October 1996.

[RFC2055] Callaghan, B., "WebNFS Server Specification", RFC2055,

October 1996.

[RFC2078] Linn, J., "Generic Security Service Application Program

Interface, Version 2", RFC2078, January 1997.

[RFC2152] Goldsmith, D., "UTF-7 A Mail-Safe Transformation Format

of Unicode", RFC2152, May 1997.

[RFC2203] Eisler, M., Chiu, A. and L. Ling, "RPCSEC_GSS Protocol

Specification", RFC2203, August 1995.

[RFC2277] Alvestrand, H., "IETF Policy on Character Sets and

Languages", BCP 18, RFC2277, January 1998.

[RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO

10646", RFC2279, January 1998.

[RFC2623] Eisler, M., "NFS Version 2 and Version 3 Security Issues

and the NFS Protocol's Use of RPCSEC_GSS and Kerberos

V5", RFC2623, June 1999.

[RFC2624] Shepler, S., "NFS Version 4 Design Considerations", RFC

2624, June 1999.

[RFC2847] Eisler, M., "LIPKEY - A Low Infrastructure Public Key

Mechanism Using SPKM", RFC2847, June 2000.

[Sandberg] Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh, B.

Lyon, "Design and Implementation of the Sun Network

Filesystem," USENIX Conference Proceedings, USENIX

Association, Berkeley, CA, Summer 1985. The basic paper

describing the SunOS implementation of the NFS version 2

protocol, and discusses the goals, protocol

specification and trade-offs.

[Srinivasan] Srinivasan, V., Jeffrey C. Mogul, "Spritely NFS:

Implementation and Performance of Cache Consistency

Protocols", WRL Research Report 89/5, Digital Equipment

Corporation Western Research Laboratory, 100 Hamilton

Ave., Palo Alto, CA, 94301, May 1989. This paper

analyzes the effect of applying a Sprite-like

consistency protocol applied to standard NFS. The issues

of recovery in a stateful environment are covered in

[Mogul].

[Unicode1] The Unicode Consortium, "The Unicode Standard, Version

3.0", Addison-Wesley Developers Press, Reading, MA,

2000. ISBN 0-201-61633-5.

More information available at: http://www.unicode.org/

[Unicode2] "Unsupported Scripts" Unicode, Inc., The Unicode

Consortium, P.O. Box 700519, San Jose, CA 95710-0519

USA, September 1999

http://www.unicode.org/unicode/standard/unsupported.Html

[XNFS] The Open Group, Protocols for Interworking: XNFS,

Version 3W, The Open Group, 1010 El Camino Real Suite

380, Menlo Park, CA 94025, ISBN 1-85912-184-5, February

1998.

HTML version available: http://www.opengroup.org

20. Authors

20.1. Editor's Address

Spencer Shepler

Sun Microsystems, Inc.

7808 Moonflower Drive

Austin, Texas 78750

Phone: +1 512-349-9376

EMail: spencer.shepler@sun.com

20.2. Authors' Addresses

Carl Beame

Hummingbird Ltd.

EMail: beame@bws.com

Brent Callaghan

Sun Microsystems, Inc.

901 San Antonio Road

Palo Alto, CA 94303

Phone: +1 650-786-5067

EMail:

brent.callaghan@sun.com

Mike Eisler

5565 Wilson Road

Colorado Springs, CO 80919

Phone: +1 719-599-9026

EMail: mike@eisler.com

David Noveck

Network Appliance

375 Totten Pond Road

Waltham, MA 02451

Phone: +1 781-895-4949

E-mail: dnoveck@netapp.com

David Robinson

Sun Microsystems, Inc.

901 San Antonio Road

Palo Alto, CA 94303

Phone: +1 650-786-5088

EMail: david.robinson@sun.com

Robert Thurlow

Sun Microsystems, Inc.

901 San Antonio Road

Palo Alto, CA 94303

Phone: +1 650-786-5096

EMail: robert.thurlow@sun.com

20.3. Acknowledgements

The author thanks and acknowledges:

Neil Brown for his extensive review and comments of various drafts.

21. Full Copyright Statement

Copyright (C) The Internet Society (2000). All Rights Reserved.

This document and translations of it may be copied and furnished to

others, and derivative works that comment on or otherwise explain it

or assist in its implementation may be prepared, copied, published

and distributed, in whole or in part, without restriction of any

kind, provided that the above copyright notice and this paragraph are

included on all such copies and derivative works. However, this

document itself may not be modified in any way, such as by removing

the copyright notice or references to the Internet Society or other

Internet organizations, except as needed for the purpose of

developing Internet standards in which case the procedures for

copyrights defined in the Internet Standards process must be

followed, or as required to translate it into languages other than

English.

The limited permissions granted above are perpetual and will not be

revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an

"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING

TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION

HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the RFCEditor function is currently provided by the

Internet Society.

 
 
 
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