Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA
draft-ietf-nfsv4-rfc5667bis-02
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Network File System Version 4 C. Lever, Ed.
Internet-Draft Oracle
Obsoletes: 5667 (if approved) August 25, 2016
Intended status: Standards Track
Expires: February 26, 2017
Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA
draft-ietf-nfsv4-rfc5667bis-02
Abstract
This document specifies Upper Layer Bindings of Network File System
(NFS) protocol versions to RPC-over-RDMA transports. These bindings
are required to enable RPC-based protocols to use direct data
placement on RPC-over-RDMA transports. This document obsoletes RFC
5667.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 26, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Changes Since RFC 5667 . . . . . . . . . . . . . . . . . 3
1.2. Extending This Upper Layer Binding . . . . . . . . . . . 4
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Conveying NFS Operations On RPC-Over-RDMA Transports . . . . 4
2.1. Use Of The Read List . . . . . . . . . . . . . . . . . . 4
2.2. Use Of The Write List . . . . . . . . . . . . . . . . . . 4
2.3. Construction Of Individual Chunks . . . . . . . . . . . . 5
2.4. Use Of Long Calls And Replies . . . . . . . . . . . . . . 5
3. NFS Versions 2 And 3 Upper Layer Binding . . . . . . . . . . 5
4. NFS Version 4 Upper Layer Binding . . . . . . . . . . . . . . 6
4.1. DDP-Eligibility . . . . . . . . . . . . . . . . . . . . . 6
4.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 7
4.3. NFS Version 4 COMPOUND Considerations . . . . . . . . . . 7
4.4. NFS Version 4 Callback . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
An RPC-over-RDMA transport, such as defined in
[I-D.ietf-nfsv4-rfc5666bis], may employ direct data placement to
transmit large data payloads associated with RPC transactions. Each
RPC-over-RDMA transport header conveys lists of memory locations
corresponding to XDR data items defined in an Upper Layer Protocol
(such as NFS).
To facilitate interoperation, RPC client and server implementations
must agree in advance on what XDR data items in which RPC procedures
are eligible for direct data placement (DDP). This document contains
material required of Upper Layer Bindings, as specified in
[I-D.ietf-nfsv4-rfc5666bis], for the following NFS protocol versions:
o NFS Version 2 [RFC1094]
o NFS Version 3 [RFC1813]
o NFS Version 4.0 [RFC7530]
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o NFS Version 4.1 [RFC5661]
o NFS Version 4.2 [I-D.ietf-nfsv4-minorversion2]
1.1. Changes Since RFC 5667
Corrections and updates made necessary by new language in
[I-D.ietf-nfsv4-rfc5666bis] have been introduced. For example,
references to deprecated features of RPC-over-RDMA Version One, such
as RDMA_MSGP, and the use of the Read list for handling RPC replies,
has been removed. The term "mapping" has been replaced with the term
"binding" or "Upper Layer Binding" throughout the document. Material
that duplicates what is in [I-D.ietf-nfsv4-rfc5666bis] has been
deleted.
Material required by [I-D.ietf-nfsv4-rfc5666bis] for Upper Layer
Bindings that was not present in [RFC5667] has been added, including
discussion of how each NFS version properly estimates the maximum
size of RPC replies.
The following changes have been made, relative to [RFC5667]:
o Ambiguous or erroneous uses of RFC2119 terms have been corrected.
o References to specific data movement mechanisms have been made
generic or removed.
o References to obsolete RFCs have been replaced.
o Technical corrections have been made. For example, the mention of
12KB and 36KB inline thresholds have been removed. The reference
to a non-existant NFS version 4 SYMLINK operation has been
replaced with NFS version 4 CREATE(NF4LNK). The discussion of NFS
version 4 COMPOUND handling has been completed.
o An IANA Considerations Section has replaced the "Port Usage
Considerations" Section.
o Code excerpts have been removed, and figures have been modernized.
o Language inconsistent with or contradictory to
[I-D.ietf-nfsv4-rfc5666bis] has been removed from Sections 2 and
3, and both Sections have been combined into Section 2 in the
present document.
o An explicit discussion of NFSv4.0 and NFSv4.1 backchannel
operation will replace the previous treatment of callback
operations. No NFSv4.x callback operation is DDP-eligible.
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o The binding for NFSv4.1 has been completed. No DDP-eligible
operations exist in NFSv4.1 that did not exist in NFSv4.0.
o A binding for NFSv4.2 has been added that includes discussion of
new data-bearing operations like READ_PLUS.
1.2. Extending This Upper Layer Binding
As stated earlier, RPC programs such as NFS are required to have an
Upper Layer Binding specification to interoperate on RPC-over-RDMA
transports [I-D.ietf-nfsv4-rfc5666bis]. The Upper Layer Binding
specified in this document can be extended to cover versions of the
NFS version 4 protocol specified after NFS version 4 minor version 2
via standards action. This includes NFSv4 extensions that are
documented separately from a new minor version.
1.3. Requirements Language
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].
2. Conveying NFS Operations On RPC-Over-RDMA Transports
Definitions of terminology and a general discussion of how RPC-over-
RDMA is used to convey RPC transactions can be found in
[I-D.ietf-nfsv4-rfc5666bis]. In this section, these general
principals are applied to the specifics of the NFS protocol.
2.1. Use Of The Read List
The Read list in each RPC-over-RDMA transport header represents a set
of memory regions containing DDP-eligible NFS argument data. Large
data items, such as the data payload of an NFS WRITE request, are
referenced by the Read list. The server places these directly into
its memory.
XDR unmarshaling code on the NFS server identifies the correspondence
between Read chunks and particular NFS arguments via the chunk
Position value encoded in each Read chunk.
2.2. Use Of The Write List
The Write list in each RPC-over-RDMA transport header represents a
set of memory regions that can receive DDP-eligible NFS result data.
Large data items such as the payload of an NFS READ request are
referenced by the Write list. The server places these directly into
client memory.
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Each Write chunk corresponds to a specific XDR data item in an NFS
reply. This document specifies how NFS client and server
implementations identify the correspondence between Write chunks and
XDR results.
2.3. Construction Of Individual Chunks
Each Read chunk is represented as a list of segments at the same XDR
Position, and each Write chunk is represented as an array of
segments. An NFS client thus has the flexibility to advertise a set
of discontiguous memory regions in which to send or receive a single
DDP-eligible data item.
2.4. Use Of Long Calls And Replies
Small RPC messages are conveyed using RDMA Send operations which are
of limited size. If an NFS request is too large to be conveyed via
an RDMA Send, and there are no DDP-eligible data items that can be
removed, an NFS client must send the request using a Long Call. The
entire NFS request is sent in a special Read chunk called a Position-
Zero Read chunk.
If a client predicts that the maximum size of an NFS reply is too
large to be conveyed via an RDMA Send, it provides a Reply chunk in
the RPC-over-RDMA transport header conveying the NFS request. The
server can place the entire NFS reply in the Reply chunk.
These special chunks are described in more detail in
[I-D.ietf-nfsv4-rfc5666bis].
3. NFS Versions 2 And 3 Upper Layer Binding
An NFS client MAY send a single Read chunk to supply opaque file data
for an NFS WRITE procedure, or the pathname for an NFS SYMLINK
procedure. For all other NFS procedures, NFS servers MUST ignore
Read chunks that have a non-zero value in their Position fields, and
Read chunks beyond the first in the Read list.
Similarly, an NFS client MAY provide a single Write chunk to receive
either opaque file data from an NFS READ procedure, or the pathname
from an NFS READLINK procedure. NFS servers MUST ignore the Write
list for any other NFS procedure, and any Write chunks beyond the
first in the Write list.
There are no NFS version 2 or 3 procedures that have DDP-eligible
data items in both their Call and Reply. However, when an NFS client
sends a Long Call or Reply, it MAY provide a combination of Read
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list, Write list, and/or a Reply chunk in the same RPC-over-RDMA
header.
If an NFS client has not provided enough bytes in a Read list to
match the size of a DDP-eligible NFS argument data item, or if an NFS
client has not provided enough Write list resources to handle an NFS
WRITE or READLINK reply, or if the client has not provided a large
enough Reply chunk to convey an NFS reply, the server MUST return one
of:
o An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid
field set to the XID of the matching NFS Call, and the rdma_error
field set to ERR_CHUNK; or
o An RPC message with the mtype field set to REPLY, the stat field
set to MSG_ACCEPTED, and the accept_stat field set to
GARBAGE_ARGS.
NFS clients already successfully estimate the maximum reply size of
each operation in order to provide an adequate set of buffers to
receive each NFS reply. An NFS client provides a Reply chunk when
the maximum possible reply size is larger than the client's responder
inline threshold.
4. NFS Version 4 Upper Layer Binding
This specification applies to NFS Version 4.0 [RFC7530], NFS Version
4.1 [RFC5661], and NFS Version 4.2 [I-D.ietf-nfsv4-minorversion2].
It also applies to the callback protocols associated with each of
these minor versions.
4.1. DDP-Eligibility
An NFS client MAY send a Read chunk to supply opaque file data for a
WRITE operation or the pathname for a CREATE(NF4LNK) operation in an
NFS version 4 COMPOUND procedure. An NFS client MUST NOT send a Read
chunk that corresponds with any other XDR data item in any other NFS
version 4 operation in an NFS version 4 COMPOUND procedure, or in an
NFS version 4 NULL procedure.
Similarly, an NFS client MAY provide a Write chunk to receive either
opaque file data from a READ operation, NFS4_CONTENT_DATA from a
READ_PLUS operation, or the pathname from a READLINK operation in an
NFS version 4 COMPOUND procedure. An NFS client MUST NOT provide a
Write chunk that corresponds with any other XDR data item in any
other NFS version 4 operation in an NFS version 4 COMPOUND procedure,
or in an NFS version 4 NULL procedure.
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There is no prohibition against an NFS version 4 COMPOUND procedure
constructed with both a READ and WRITE operation, say. Thus it is
possible for NFS version 4 COMPOUND procedures to use both the Read
list and Write list simultaneously. An NFS client MAY provide a Read
list and a Write list in the same transaction if it is sending a Long
Call or Reply.
If an NFS client has not provided enough bytes in a Read list to
match the size of a DDP-eligible NFS argument data item, or if an NFS
client has not provided enough Write list resources to handle a WRITE
or READLINK operation, or if the client has not provided a large
enough Reply chunk to convey an NFS reply, the server MUST return one
of:
o An RPC-over-RDMA message of type RDMA_ERROR, with the rdma_xid
field set to the XID of the matching NFS Call, and the rdma_error
field set to ERR_CHUNK; or
o An RPC message with the mtype field set to REPLY, the stat field
set to MSG_ACCEPTED, and the accept_stat field set to
GARBAGE_ARGS.
4.2. Reply Size Estimation
An NFS client provides a Reply chunk when the maximum possible reply
size is larger than the client's responder inline threshold. NFS
clients successfully estimate the maximum reply size of most
operations in order to provide an adequate set of buffers to receive
each NFS reply.
There are certain NFSv4 data items whose size cannot be reliably
estimated by clients, however, because there is no protocol-specified
size limit on these structures. These include but are not limited to
opaque types such as the attrlist4 field; fields containing ACLs such
as fattr4_acl, fattr4_dacl, fattr4_sacl; fields in the fs_locations4
and fs_locations_info4 data structures; and opaque fields loc_body,
loh_body, da_addr_body, lou_body, lrf_body, fattr_layout_types and
fs_layout_types, which pertain to pNFS layout metadata.
4.3. NFS Version 4 COMPOUND Considerations
An NFS version 4 COMPOUND procedure supplies arguments for a sequence
of operations, and returns results from that sequence. A client MAY
construct an NFS version 4 COMPOUND procedure that uses more than one
chunk in either the Read list or Write list. The NFS client provides
XDR Position values in each Read chunk to disambiguate which chunk is
associated with which XDR data item.
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However NFS server and client implementations must agree in advance
on how to pair Write chunks with returned result data items. The
mechanism specified in [I-D.ietf-nfsv4-rfc5666bis]) is applied here:
o The first chunk in the Write list MUST be used by the first READ
or READLINK operation in an NFS version 4 COMPOUND procedure. The
next Write chunk is used by the next READ or READLINK, and so on.
o If there are more READ or READLINK operations than Write chunks,
then any remaining operations MUST return their results inline.
o If an NFS client presents a Write chunk, then the corresponding
READ or READLINK operation MUST return its data by placing data
into that chunk.
o If the Write chunk has zero RDMA segments, or if the total size of
the segments is zero, then the corresponding READ or READLINK
operation MUST return its result inline.
The following example shows a Write list with three Write chunks, A,
B, and C. The server consumes the provided Write chunks by writing
the results of the designated operations in the compound request,
READ and READLINK, back to each chunk.
Write list:
A --> B --> C
NFS version 4 COMPOUND request:
PUTFH LOOKUP READ PUTFH LOOKUP READLINK PUTFH LOOKUP READ
| | |
v v v
A B C
If the client does not want to have the READLINK result returned
directly, it provides a zero-length array of segment triplets for
buffer B or sets the values in the segment triplet for buffer B to
zeros to indicate that the READLINK result must be returned inline.
Unlike NFS versions 2 and 3, the maximum size of an NFS version 4
COMPOUND is not bounded. However, typical NFS version 4 clients
rarely issue such problematic requests. In practice, NFS version 4
clients behave in much more predictable ways. Rsize and wsize apply
to COMPOUND operations by capping the total amount of data payload
allowed in each COMPOUND. An extension to NFS version 4 supporting a
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comprehensive exchange of upper-layer message size parameters is part
of [RFC5661].
4.4. NFS Version 4 Callback
The NFS version 4 protocols support server-initiated callbacks to
notify clients of events such as recalled delegations. There are no
DDP-eligible data items in callback protocols associated with
NFSv4.0, NFSv4.1, or NFSv4.2.
In NFS version 4.1 and 4.2, callback operations may appear on the
same connection as one used for NFS version 4 client requests. NFS
version 4 clients and servers MUST use the mechanism described in
[I-D.ietf-nfsv4-rpcrdma-bidirection] when backchannel operations are
conveyed on RPC-over-RDMA transports.
5. IANA Considerations
NFS use of direct data placement introduces a need for an additional
NFS port number assignment for networks that share traditional UDP
and TCP port spaces with RDMA services. The iWARP [RFC5041]
[RFC5040] protocol is such an example (InfiniBand is not).
NFS servers for versions 2 and 3 [RFC1094] [RFC1813] traditionally
listen for clients on UDP and TCP port 2049, and additionally, they
register these with the portmapper and/or rpcbind [RFC1833] service.
However, [RFC7530] requires NFS servers for version 4 to listen on
TCP port 2049, and they are not required to register.
An NFS version 2 or version 3 server supporting RPC-over-RDMA on such
a network and registering itself with the RPC portmapper MAY choose
an arbitrary port, or MAY use the alternative well-known port number
for its RPC-over-RDMA service. The chosen port MAY be registered
with the RPC portmapper under the netid assigned by the requirement
in [I-D.ietf-nfsv4-rfc5666bis].
An NFS version 4 server supporting RPC-over-RDMA on such a network
MUST use the alternative well-known port number for its RPC-over-RDMA
service. Clients SHOULD connect to this well-known port without
consulting the RPC portmapper (as for NFSv4/TCP).
The port number assigned to an NFS service over an RPC-over-RDMA
transport is available from the IANA port registry [RFC3232].
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6. Security Considerations
The RDMA transport for RPC [I-D.ietf-nfsv4-rfc5666bis] supports all
RPC [RFC5531] security models, including RPCSEC_GSS [RFC2203]
security and transport-level security. The choice of RDMA Read and
RDMA Write to convey RPC argument and results does not affect this,
since it only changes the method of data transfer. Specifically, the
requirements of [I-D.ietf-nfsv4-rfc5666bis] ensure that this choice
does not introduce new vulnerabilities.
Because this document defines only the binding of the NFS protocols
atop [I-D.ietf-nfsv4-rfc5666bis], all relevant security
considerations are therefore to be described at that layer.
7. Acknowledgments
The author gratefully acknowledges the work of Brent Callaghan and
Tom Talpey on the original NFS Direct Data Placement specification
[RFC5667]. The author also wishes to thank Bill Baker and Greg
Marsden for their support of this work.
Dave Noveck provided excellent review, constructive suggestions, and
consistent navigational guidance throughout the process of drafting
this document.
Special thanks go to nfsv4 Working Group Chair Spencer Shepler and
nfsv4 Working Group Secretary Thomas Haynes for their support.
8. References
8.1. Normative References
[I-D.ietf-nfsv4-minorversion2]
Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
nfsv4-minorversion2-41 (work in progress), January 2016.
[I-D.ietf-nfsv4-rfc5666bis]
Lever, C., Simpson, W., and T. Talpey, "Remote Direct
Memory Access Transport for Remote Procedure Call, Version
One", draft-ietf-nfsv4-rfc5666bis-07 (work in progress),
May 2016.
[I-D.ietf-nfsv4-rpcrdma-bidirection]
Lever, C., "Bi-directional Remote Procedure Call On RPC-
over-RDMA Transports", draft-ietf-nfsv4-rpcrdma-
bidirection-05 (work in progress), June 2016.
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[RFC1833] Srinivasan, R., "Binding Protocols for ONC RPC Version 2",
RFC 1833, DOI 10.17487/RFC1833, August 1995,
<http://www.rfc-editor.org/info/rfc1833>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
Specification", RFC 2203, DOI 10.17487/RFC2203, September
1997, <http://www.rfc-editor.org/info/rfc2203>.
[RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol
Specification Version 2", RFC 5531, DOI 10.17487/RFC5531,
May 2009, <http://www.rfc-editor.org/info/rfc5531>.
[RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed.,
"Network File System (NFS) Version 4 Minor Version 1
Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010,
<http://www.rfc-editor.org/info/rfc5661>.
[RFC7530] Haynes, T., Ed. and D. Noveck, Ed., "Network File System
(NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530,
March 2015, <http://www.rfc-editor.org/info/rfc7530>.
8.2. Informative References
[RFC1094] Nowicki, B., "NFS: Network File System Protocol
specification", RFC 1094, DOI 10.17487/RFC1094, March
1989, <http://www.rfc-editor.org/info/rfc1094>.
[RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS
Version 3 Protocol Specification", RFC 1813,
DOI 10.17487/RFC1813, June 1995,
<http://www.rfc-editor.org/info/rfc1813>.
[RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
January 2002, <http://www.rfc-editor.org/info/rfc3232>.
[RFC5040] Recio, R., Metzler, B., Culley, P., Hilland, J., and D.
Garcia, "A Remote Direct Memory Access Protocol
Specification", RFC 5040, DOI 10.17487/RFC5040, October
2007, <http://www.rfc-editor.org/info/rfc5040>.
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[RFC5041] Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct
Data Placement over Reliable Transports", RFC 5041,
DOI 10.17487/RFC5041, October 2007,
<http://www.rfc-editor.org/info/rfc5041>.
[RFC5667] Talpey, T. and B. Callaghan, "Network File System (NFS)
Direct Data Placement", RFC 5667, DOI 10.17487/RFC5667,
January 2010, <http://www.rfc-editor.org/info/rfc5667>.
Author's Address
Charles Lever (editor)
Oracle Corporation
1015 Granger Avenue
Ann Arbor, MI 48104
USA
Phone: +1 734 274 2396
Email: chuck.lever@oracle.com
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