NFSv4 J. Lentini
Internet-Draft M. Eisler
Intended status: Standards Track D. Kenchammana
Expires: April 24, 2011 NetApp
A. Madan
Carnegie Mellon University
R. Iyer
October 21, 2010
NFS Server-side Copy
draft-lentini-nfsv4-server-side-copy-06.txt
Abstract
This document describes a set of NFS operations for offloading a file
copy to a file server or between two file servers.
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-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 24, 2011.
Copyright Notice
Copyright (c) 2010 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
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
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described in the Simplified BSD License.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Intra-Server Copy . . . . . . . . . . . . . . . . . . . . 5
3.2. Inter-Server Copy . . . . . . . . . . . . . . . . . . . . 6
3.3. Server-to-Server Copy Protocol . . . . . . . . . . . . . . 9
3.3.1. Using NFSv4.x as a Server-to-Server Copy Protocol . . 9
3.3.2. Using an alternative Server-to-Server Copy Protocol . 10
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. netloc4 - Network Locations . . . . . . . . . . . . . . . 11
4.2. Operation U: COPY_NOTIFY - Notify a source server of a
future copy . . . . . . . . . . . . . . . . . . . . . . . 12
4.3. Operation V: COPY_REVOKE - Revoke a destination
server's copy privileges . . . . . . . . . . . . . . . . . 14
4.4. Operation W: COPY - Initiate a server-side copy . . . . . 15
4.5. Operation X: COPY_ABORT - Cancel a server-side copy . . . 23
4.6. Operation Y: COPY_STATUS - Poll for status of a
server-side copy . . . . . . . . . . . . . . . . . . . . . 24
4.7. Operation Z: CB_COPY - Report results of a server-side
copy . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.8. Copy Offload Stateids . . . . . . . . . . . . . . . . . . 26
5. Security Considerations . . . . . . . . . . . . . . . . . . . 27
5.1. Inter-Server Copy Security . . . . . . . . . . . . . . . . 27
5.1.1. Requirements for Secure Inter-Server Copy . . . . . . 27
5.1.2. Inter-Server Copy with RPCSEC_GSSv3 . . . . . . . . . 28
5.1.3. Inter-Server Copy via ONC RPC but without
RPCSEC_GSSv3 . . . . . . . . . . . . . . . . . . . . . 34
5.1.4. Inter-Server Copy without ONC RPC and RPCSEC_GSSv3 . . 35
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.1. Normative References . . . . . . . . . . . . . . . . . . . 35
7.2. Informational References . . . . . . . . . . . . . . . . . 35
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36
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1. Requirements notation
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. Introduction
This document describes a server-side copy feature for the NFS
protocol.
The server-side copy feature provides a mechanism for the NFS client
to perform a file copy on the server without the data being
transmitted back and forth over the network.
Without this feature, an NFS client copies data from one location to
another by reading the data from the server over the network, and
then writing the data back over the network to the server. Using
this server-side copy operation, the client is able to instruct the
server to copy the data locally without the data being sent back and
forth over the network unnecessarily.
In general, this feature is useful whenever data is copied from one
location to another on the server. It is particularly useful when
copying the contents of a file from a backup. Backup-versions of a
file are copied for a number of reasons, including restoring and
cloning data.
If the source object and destination object are on different file
servers, the file servers will communicate with one another to
perform the copy operation. The server-to-server protocol by which
this is accomplished is not defined in this document.
3. Protocol Overview
The server-side copy offload operations support both intra-server and
inter-server file copies. An intra-server copy is a copy in which
the source file and destination file reside on the same server. In
an inter-server copy, the source file and destination file are on
different servers. In both cases, the copy may be performed
synchronously or asynchronously.
Throughout the rest of this document, we refer to the NFS server
containing the source file as the "source server" and the NFS server
to which the file is transferred as the "destination server". In the
case of an intra-server copy, the source server and destination
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server are the same server. Therefore in the context of an intra-
server copy, the terms source server and destination server refer to
the single server performing the copy.
The operations described below are designed to copy files. Other
file system objects can be copied by building on these operations or
using other techniques. For example if the user wishes to copy a
directory, the client can synthesize a directory copy by first
creating the destination directory and then copying the source
directory's files to the new destination directory. If the user
wishes to copy a namespace junction [FEDFS-NSDB] [FEDFS-ADMIN], the
client can use the ONC RPC Federated Filesystem protocol
[FEDFS-ADMIN] to perform the copy. Specifically the client can
determine the source junction's attributes using the FEDFS_LOOKUP_FSN
procedure and create a duplicate junction using the
FEDFS_CREATE_JUNCTION procedure.
For the inter-server copy protocol, the operations are defined to be
compatible with a server-to-server copy protocol in which the
destination server reads the file data from the source server. This
model in which the file data is pulled from the source by the
destination has a number of advantages over a model in which the
source pushes the file data to the destination. The advantages of
the pull model include:
o The pull model only requires a remote server (i.e. the destination
server) to be granted read access. A push model requires a remote
server (i.e. the source server) to be granted write access, which
is more privileged.
o The pull model allows the destination server to stop reading if it
has run out of space. In a push model, the destination server
must flow control the source server in this situation.
o The pull model allows the destination server to easily flow
control the data stream by adjusting the size of its read
operations. In a push model, the destination server does not have
this ability. The source server in a push model is capable of
writing chunks larger than the destination server has requested in
attributes and session parameters. In theory, the destination
server could perform a "short" write in this situation, but this
approach is known to behave poorly in practice.
The following operations are provided to support server-side copy:
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COPY_NOTIFY: For inter-server copies, the client sends this
operation to the source server to notify it of a future file copy
from a given destination server for the given user.
COPY_REVOKE: Also for inter-server copies, the client sends this
operation to the source server to revoke permission to copy a file
for the given user.
COPY: Used by the client to request a file copy.
COPY_ABORT: Used by the client to abort an asynchronous file copy.
COPY_STATUS: Used by the client to poll the status of an
asynchronous file copy.
CB_COPY: Used by the destination server to report the results of an
asynchronous file copy to the client.
These operations are described in detail in Section 4. This section
provides an overview of how these operations are used to perform
server-side copies.
3.1. Intra-Server Copy
To copy a file on a single server, the client uses a COPY operation.
The server may respond to the copy operation with the final results
of the copy or it may perform the copy asynchronously and deliver the
results using a CB_COPY operation callback. If the copy is performed
asynchronously, the client may poll the status of the copy using
COPY_STATUS or cancel the copy using COPY_ABORT.
A synchronous intra-server copy is shown in Figure 1. In this
example, the NFS server chooses to perform the copy synchronously.
The copy operation is completed, either successfully or
unsuccessfully, before the server replies to the client's request.
The server's reply contains the final result of the operation.
Client Server
+ +
| |
|--- COPY ---------------------------->| Client requests
|<------------------------------------/| a file copy
| |
| |
Figure 1: A synchronous intra-server copy.
An asynchronous intra-server copy is shown in Figure 2. In this
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example, the NFS server performs the copy asynchronously. The
server's reply to the copy request indicates that the copy operation
was initiated and the final result will be delivered at a later time.
The server's reply also contains a copy stateid. The client may use
this copy stateid to poll for status information (as shown) or to
cancel the copy using a COPY_ABORT. When the server completes the
copy, the server performs a callback to the client and reports the
results.
Client Server
+ +
| |
|--- COPY ---------------------------->| Client requests
|<------------------------------------/| a file copy
| |
| |
|--- COPY_STATUS --------------------->| Client may poll
|<------------------------------------/| for status
| |
| . | Multiple COPY_STATUS
| . | operations may be sent.
| . |
| |
|<-- CB_COPY --------------------------| Server reports results
|\------------------------------------>|
| |
Figure 2: An asynchronous intra-server copy.
3.2. Inter-Server Copy
A copy may also be performed between two servers. The copy protocol
is designed to accommodate a variety of network topologies. As shown
in Figure 3, the client and servers may be connected by multiple
networks. In particular, the servers may be connected by a
specialized, high speed network (network 192.168.33.0/24 in the
diagram) that does not include the client. The protocol allows the
client to setup the copy between the servers (over network
10.11.78.0/24 in the diagram) and for the servers to communicate on
the high speed network if they choose to do so.
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192.168.33.0/24
+-------------------------------------+
| |
| |
| 192.168.33.18 | 192.168.33.56
+-------+------+ +------+------+
| Source | | Destination |
+-------+------+ +------+------+
| 10.11.78.18 | 10.11.78.56
| |
| |
| 10.11.78.0/24 |
+------------------+------------------+
|
|
| 10.11.78.243
+-----+-----+
| Client |
+-----------+
Figure 3: An example inter-server network topology.
For an inter-server copy, the client notifies the source server that
a file will be copied by the destination server using a COPY_NOTIFY
operation. The client then initiates the copy by sending the COPY
operation to the destination server. The destination server may
perform the copy synchronously or asynchronously.
A synchronous inter-server copy is shown in Figure 4. In this case,
the destination server chooses to perform the copy before responding
to the client's COPY request.
An asynchronous copy is shown in Figure 5. In this case, the
destination server chooses to respond to the client's COPY request
immediately and then perform the copy asynchronously.
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Client Source Destination
+ + +
| | |
|--- COPY_NOTIFY --->| |
|<------------------/| |
| | |
| | |
|--- COPY ---------------------------->|
| | |
| | |
| |<----- read -----|
| |\--------------->|
| | |
| | . | Multiple reads may
| | . | be necessary
| | . |
| | |
| | |
|<------------------------------------/| Destination replies
| | | to COPY
Figure 4: A synchronous inter-server copy.
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Client Source Destination
+ + +
| | |
|--- COPY_NOTIFY --->| |
|<------------------/| |
| | |
| | |
|--- COPY ---------------------------->|
|<------------------------------------/|
| | |
| | |
| |<----- read -----|
| |\--------------->|
| | |
| | . | Multiple reads may
| | . | be necessary
| | . |
| | |
| | |
|--- COPY_STATUS --------------------->| Client may poll
|<------------------------------------/| for status
| | |
| | . | Multiple COPY_STATUS
| | . | operations may be sent
| | . |
| | |
| | |
| | |
|<-- CB_COPY --------------------------| Destination reports
|\------------------------------------>| results
| | |
Figure 5: An asynchronous inter-server copy.
3.3. Server-to-Server Copy Protocol
During an inter-server copy, the destination server reads the file
data from the source server. The source server and destination
server are not required to use a specific protocol to transfer the
file data. The choice of what protocol to use is ultimately the
destination server's decision.
3.3.1. Using NFSv4.x as a Server-to-Server Copy Protocol
The destination server MAY use standard NFSv4.x (where x >= 1) to
read the data from the source server. If NFSv4.x is used for the
server-to-server copy protocol, the destination server can use the
filehandle contained in the COPY request with standard NFSv4.x
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operations to read data from the source server. Specifically, the
destination server may use the NFSv4.x OPEN operation's CLAIM_FH
facility to open the file being copied and obtain an open stateid.
Using the stateid, the destination server may then use NFSv4.x READ
operations to read the file.
3.3.2. Using an alternative Server-to-Server Copy Protocol
In a homogeneous environment, the source and destination servers
might be able to perform the file copy extremely efficiently using
specialized protocols. For example the source and destination
servers might be two nodes sharing a common file system format for
the source and destination file systems. Thus the source and
destination are in an ideal position to efficiently render the image
of the source file to the destination file by replicating the file
system formats at the block level. Another possibility is that the
source and destination might be two nodes sharing a common storage
area network, and thus there is no need to copy any data at all, and
instead ownership of the file and its contents might simply be re-
assigned to the destination. To allow for these possibilities, the
destination server is allowed to use a server-to-server copy protocol
of its choice.
In a heterogeneous environment, using a protocol other than NFSv4.x
(e.g. HTTP [RFC2616] or FTP [RFC0959]) presents some challenges. In
particular, the destination server is presented with the challenge of
accessing the source file given only an NFSv4.x filehandle.
One option for protocols that identify source files with path names
is to use an ASCII hexadecimal representation of the source
filehandle as the file name.
Another option for the source server is to use URLs to direct the
destination server to a specialized service. For example, the
response to COPY_NOTIFY could include the URL
ftp://s1.example.com:9999/_FH/0x12345, where 0x12345 is the ASCII
hexadecimal representation of the source filehandle. When the
destination server receives the source server's URL, it would use
"_FH/0x12345" as the file name to pass to the FTP server listening on
port 9999 of s1.example.com. On port 9999 there would be a special
instance of the FTP service that understands how to convert NFS
filehandles to an open file descriptor (in many operating systems,
this would require a new system call, one which is the inverse of the
makefh() function that the pre-NFSv4 MOUNT service needs).
Authenticating and identifying the destination server to the source
server is also a challenge. Recommendations for how to accomplish
this are given in Section 5.1.2.4 and Section 5.1.4.
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4. Operations
In the sections that follow, several operations are defined that
together provide the server-side copy feature. These operations are
intended to be OPTIONAL operations as defined in section 17 of
[RFC5661]. The COPY_NOTIFY, COPY_REVOKE, COPY, COPY_ABORT, and
COPY_STATUS operations are designed to be sent within an NFSv4
COMPOUND procedure. The CB_COPY operation is designed to be sent
within an NFSv4 CB_COMPOUND procedure.
Each operation is performed in the context of the user identified by
the ONC RPC credential of its containing COMPOUND or CB_COMPOUND
request. For example, a COPY_ABORT operation issued by a given user
indicates that a specified COPY operation initiated by the same user
be canceled. Therefore a COPY_ABORT MUST NOT interfere with a copy
of the same file initiated by another user.
An NFS server MAY allow an administrative user to monitor or cancel
copy operations using an implementation specific interface.
4.1. netloc4 - Network Locations
The server-side copy operations specify network locations using the
netloc4 data type shown below:
enum netloc_type4 {
NL4_NAME = 0,
NL4_URL = 1,
NL4_NETADDR = 2
};
union netloc4 switch (netloc_type4 nl_type) {
case NL4_NAME: utf8str_cis nl_name;
case NL4_URL: utf8str_cis nl_url;
case NL4_NETADDR: netaddr4 nl_addr;
};
If the netloc4 is of type NL4_NAME, the nl_name field MUST be
specified as a UTF-8 string. The nl_name is expected to be resolved
to a network address via DNS, LDAP, NIS, /etc/hosts, or some other
means. If the netloc4 is of type NL4_URL, a server URL [RFC3986]
appropriate for the server-to-server copy operation is specified as a
UTF-8 string. If the netloc4 is of type NL4_NETADDR, the nl_addr
field MUST contain a valid netaddr4 as defined in Section 3.3.9 of
[RFC5661].
When netloc4 values are used for an inter-server copy as shown in
Figure 3, their values may be evaluated on the source server,
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destination server, and client. The network environment in which
these systems operate should be configured so that the netloc4 values
are interpreted as intended on each system.
4.2. Operation U: COPY_NOTIFY - Notify a source server of a future copy
ARGUMENTS
struct COPY_NOTIFY4args {
/* CURRENT_FH: source file */
netloc4 cna_destination_server;
};
RESULTS
union COPY_NOTIFY4res switch (nfsstat4 cnr_status) {
case NFS4_OK:
nfstime4 cnr_lease_time;
netloc4 cnr_source_server<>;
default:
void;
};
DESCRIPTION
This operation is used for an inter-server copy. A client sends this
operation in a COMPOUND request to the source server to authorize a
destination server identified by cna_destination_server to read the
file specified by CURRENT_FH on behalf of the given user.
The cna_destination_server MUST be specified using the netloc4
network location format. The server is not required to resolve the
cna_destination_server address before completing this operation.
If this operation succeeds, the source server will allow the
cna_destination_server to copy the specified file on behalf of the
given user. If COPY_NOTIFY succeeds, the destination server is
granted permission to read the file as long as both of the following
conditions are met:
o The destination server begins reading the source file before the
cnr_lease_time expires. If the cnr_lease_time expires while the
destination server is still reading the source file, the
destination server is allowed to finish reading the file.
o The client has not issued a COPY_REVOKE for the same combination
of user, filehandle, and destination server.
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The cnr_lease_time is chosen by the source server. A cnr_lease_time
of 0 (zero) indicates an infinite lease. To renew the copy lease
time the client should resend the same copy notification request to
the source server.
To avoid the need for synchronized clocks, copy 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 lease. 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 copy lease times (e.g. if the client estimates the one-way
propagation delay as 200 milliseconds, then it can assume that the
lease is already 200 milliseconds old when it gets it). In addition,
it will take another 200 milliseconds to get a response back to the
server. So the client must send a lease renewal or send the copy
offload request to the cna_destination_server at least 400
milliseconds before the copy lease would expire. If the propagation
delay varies over the life of the lease (e.g. the client is on a
mobile host), the client will need to continuously subtract the
increase in propagation delay from the copy lease times.
The server's copy lease period configuration should take into account
the network distance of the clients that will be accessing the
server's resources. It is expected that the lease period will take
into account the network propagation delays and other network delay
factors for the client population. Since the protocol does not allow
for an automatic method to determine an appropriate copy lease
period, the server's administrator may have to tune the copy lease
period.
A successful response will also contain a list of names, addresses,
and URLs called cnr_source_server, on which the source is willing to
accept connections from the destination. These might not be
reachable from the client and might be located on networks to which
the client has no connection.
If the client wishes to perform an inter-server copy, the client MUST
send a COPY_NOTIFY to the source server. Therefore, the source
server MUST support COPY_NOTIFY.
For a copy only involving one server (the source and destination are
on the same server), this operation is unnecessary.
The COPY_NOTIFY operation may fail for the following reasons (this is
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a partial list):
NFS4ERR_MOVED: The file system which contains the source file is not
present on the source server. The client can determine the
correct location and reissue the operation with the correct
location.
NFS4ERR_NOTSUPP: The copy offload operation is not supported by the
NFS server receiving this request.
NFS4ERR_WRONGSEC: The security mechanism being used by the client
does not match the server's security policy.
4.3. Operation V: COPY_REVOKE - Revoke a destination server's copy
privileges
ARGUMENTS
struct COPY_REVOKE4args {
/* CURRENT_FH: source file */
netloc4 cra_destination_server;
};
RESULTS
struct COPY_REVOKE4res {
nfsstat4 crr_status;
};
DESCRIPTION
This operation is used for an inter-server copy. A client sends this
operation in a COMPOUND request to the source server to revoke the
authorization of a destination server identified by
cra_destination_server from reading the file specified by CURRENT_FH
on behalf of given user. If the cra_destination_server has already
begun copying the file, a successful return from this operation
indicates that further access will be prevented.
The cra_destination_server MUST be specified using the netloc4
network location format. The server is not required to resolve the
cra_destination_server address before completing this operation.
The COPY_REVOKE operation is useful in situations in which the source
server granted a very long or infinite lease on the destination
server's ability to read the source file and all copy operations on
the source file have been completed.
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For a copy only involving one server (the source and destination are
on the same server), this operation is unnecessary.
If the server supports COPY_NOTIFY, the server is REQUIRED to support
the COPY_REVOKE operation.
The COPY_REVOKE operation may fail for the following reasons (this is
a partial list):
NFS4ERR_MOVED: The file system which contains the source file is not
present on the source server. The client can determine the
correct location and reissue the operation with the correct
location.
NFS4ERR_NOTSUPP: The copy offload operation is not supported by the
NFS server receiving this request.
4.4. Operation W: COPY - Initiate a server-side copy
ARGUMENTS
#define COPY4_GUARDED = 0x00000001;
#define COPY4_METADATA = 0x00000002;
struct COPY4args {
/* SAVED_FH: source file */
/* CURRENT_FH: destination file or */
/* directory */
offset4 ca_src_offset;
offset4 ca_dst_offset;
length4 ca_count;
uint32_t ca_flags;
component4 ca_destination;
netloc4 ca_source_server<>;
};
RESULTS
union COPY4res switch (nfsstat4 cr_status) {
/* CURRENT_FH: destination file */
case NFS4_OK:
stateid4 cr_callback_id<1>;
default:
length4 cr_bytes_copied;
};
DESCRIPTION
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The COPY operation is used for both intra- and inter-server copies.
In both cases, the COPY is always sent from the client to the
destination server of the file copy. The COPY operation requests
that a file be copied from the location specified by the SAVED_FH
value to the location specified by the combination of CURRENT_FH and
ca_destination.
The SAVED_FH must be a regular file. If SAVED_FH is not a regular
file, the operation MUST fail and return NFS4ERR_WRONG_TYPE.
In order to set SAVED_FH to the source file handle, the compound
procedure requesting the COPY will include a sub-sequence of
operations such as
PUTFH source-fh
SAVEFH
If the request is for a server-to-server copy, the source-fh is a
filehandle from the source server and the compound procedure is being
executed on the destination server. In this case, the source-fh is a
foreign filehandle on the server receiving the COPY request. If
either PUTFH or SAVEFH checked the validity of the filehandle, the
operation would likely fail and return NFS4ERR_STALE.
In order to avoid this problem, the minor version incorporating the
COPY operations will need to make a few small changes in the handling
of existing operations. If a server supports the server-to-server
COPY feature, a PUTFH followed by a SAVEFH MUST NOT return
NFS4ERR_STALE for either operation. These restrictions do not pose
substantial difficulties for servers. The CURRENT_FH and SAVED_FH
may be validated in the context of the operation referencing them and
an NFS4ERR_STALE error returned for an invalid file handle at that
point.
The CURRENT_FH and ca_destination together specify the destination of
the copy operation. If ca_destination is of 0 (zero) length, then
CURRENT_FH specifies the target file. In this case, CURRENT_FH MUST
be a regular file and not a directory. If ca_destination is not of 0
(zero) length, the ca_destination argument specifies the file name to
which the data will be copied within the directory identified by
CURRENT_FH. In this case, CURRENT_FH MUST be a directory and not a
regular file.
If the file named by ca_destination does not exist and the operation
completes successfully, the file will be visible in the file system
namespace. If the file does not exist and the operation fails, the
file MAY be visible in the file system namespace depending on when
the failure occurs and on the implementation of the NFS server
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receiving the COPY operation. If the ca_destination name cannot be
created in the destination file system (due to file name
restrictions, such as case or length), the operation MUST fail.
The ca_src_offset is the offset within the source file from which the
data will be read, the ca_dst_offset is the offset within the
destination file to which the data will be written, and the ca_count
is the number of bytes that will be copied. An offset of 0 (zero)
specifies the start of the file. A count of 0 (zero) requests that
all bytes from ca_src_offset through EOF be copied to the
destination. If concurrent modifications to the source file overlap
with the source file region being copied, the data copied may include
all, some, or none of the modifications. The client can use standard
NFS operations (e.g. OPEN with OPEN4_SHARE_DENY_WRITE or mandatory
byte range locks) to protect against concurrent modifications if the
client is concerned about this. If the source file's end of file is
being modified in parallel with a copy that specifies a count of 0
(zero) bytes, the amount of data copied is implementation dependent
(clients may guard against this case by specifying a non-zero count
value or preventing modification of the source file as mentioned
above).
If the source offset or the source offset plus count is greater than
or equal to the size of the source file, the operation will fail with
NFS4ERR_INVAL. The destination offset or destination offset plus
count may be greater than the size of the destination file. This
allows for the client to issue parallel copies to implement
operations such as "cat file1 file2 file3 file4 > dest".
If the destination file is created as a result of this command, the
destination file's size will be equal to the number of bytes
successfully copied. If the destination file already existed, the
destination file's size may increase as a result of this operation
(e.g. if ca_dst_offset plus ca_count is greater than the
destination's initial size).
If the ca_source_server list is specified, then this is an inter-
server copy operation and the source file is on a remote server. The
client is expected to have previously issued a successful COPY_NOTIFY
request to the remote source server. The ca_source_server list
SHOULD be the same as the COPY_NOTIFY response's cnr_source_server
list. If the client includes the entries from the COPY_NOTIFY
response's cnr_source_server list in the ca_source_server list, the
source server can indicate a specific copy protocol for the
destination server to use by returning a URL, which specifies both a
protocol service and server name. Server-to-server copy protocol
considerations are described in Section 3.3 and Section 5.1.
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The ca_flags argument allows the copy operation to be customized in
the following ways using the guarded flag (COPY4_GUARDED) and the
metadata flag (COPY4_METADATA).
[NOTE: Earlier versions of this document defined a
COPY4_SPACE_RESERVED flag for controlling space reservations on the
destination file. This flag has been removed with the expectation
that the space_reserve attribute defined in [SPACE-RESERVE] will be
adopted.]
If the guarded flag is set and the destination exists on the server,
this operation will fail with NFS4ERR_EXIST.
If the guarded flag is not set and the destination exists on the
server, the behavior is implementation dependent.
If the metadata flag is set and the client is requesting a whole file
copy (i.e. ca_count is 0 (zero)), a subset of the destination file's
attributes MUST be the same as the source file's corresponding
attributes and a subset of the destination file's attributes SHOULD
be the same as the source file's corresponding attributes. The
attributes in the MUST and SHOULD copy subsets will be defined for
each NFS version.
For NFSv4.1, Table 1 and Table 2 list the REQUIRED and RECOMMENDED
attributes respectively. A "MUST" in the "Copy to destination file?"
column indicates that the attribute is part of the MUST copy set. A
"SHOULD" in the "Copy to destination file?" column indicates that the
attribute is part of the SHOULD copy set.
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+--------------------+----+---------------------------+
| Name | Id | Copy to destination file? |
+--------------------+----+---------------------------+
| supported_attrs | 0 | no |
| type | 1 | MUST |
| fh_expire_type | 2 | no |
| change | 3 | SHOULD |
| size | 4 | MUST |
| link_support | 5 | no |
| symlink_support | 6 | no |
| named_attr | 7 | no |
| fsid | 8 | no |
| unique_handles | 9 | no |
| lease_time | 10 | no |
| rdattr_error | 11 | no |
| filehandle | 19 | no |
| suppattr_exclcreat | 75 | no |
+--------------------+----+---------------------------+
Table 1
+--------------------+----+---------------------------+
| Name | Id | Copy to destination file? |
+--------------------+----+---------------------------+
| acl | 12 | MUST |
| aclsupport | 13 | no |
| archive | 14 | no |
| cansettime | 15 | no |
| case_insensitive | 16 | no |
| case_preserving | 17 | no |
| change_policy | 60 | no |
| chown_restricted | 18 | MUST |
| dacl | 58 | MUST |
| dir_notif_delay | 56 | no |
| dirent_notif_delay | 57 | no |
| fileid | 20 | no |
| files_avail | 21 | no |
| files_free | 22 | no |
| files_total | 23 | no |
| fs_charset_cap | 76 | no |
| fs_layout_type | 62 | no |
| fs_locations | 24 | no |
| fs_locations_info | 67 | no |
| fs_status | 61 | no |
| hidden | 25 | MUST |
| homogeneous | 26 | no |
| layout_alignment | 66 | no |
| layout_blksize | 65 | no |
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| layout_hint | 63 | no |
| layout_type | 64 | no |
| maxfilesize | 27 | no |
| maxlink | 28 | no |
| maxname | 29 | no |
| maxread | 30 | no |
| maxwrite | 31 | no |
| mdsthreshold | 68 | no |
| mimetype | 32 | MUST |
| mode | 33 | MUST |
| mode_set_masked | 74 | no |
| mounted_on_fileid | 55 | no |
| no_trunc | 34 | no |
| numlinks | 35 | no |
| owner | 36 | MUST |
| owner_group | 37 | MUST |
| quota_avail_hard | 38 | no |
| quota_avail_soft | 39 | no |
| quota_used | 40 | no |
| rawdev | 41 | no |
| retentevt_get | 71 | MUST |
| retentevt_set | 72 | no |
| retention_get | 69 | MUST |
| retention_hold | 73 | MUST |
| retention_set | 70 | no |
| sacl | 59 | MUST |
| space_avail | 42 | no |
| space_free | 43 | no |
| space_total | 44 | no |
| space_used | 45 | no |
| system | 46 | MUST |
| time_access | 47 | MUST |
| time_access_set | 48 | no |
| time_backup | 49 | no |
| time_create | 50 | MUST |
| time_delta | 51 | no |
| time_metadata | 52 | SHOULD |
| time_modify | 53 | MUST |
| time_modify_set | 54 | no |
+--------------------+----+---------------------------+
Table 2
[NOTE: The space_reserve attribute [SPACE-RESERVE] will be in the
MUST set.]
[NOTE: The source file's attribute values will take precedence over
any attribute values inherited by the destination file.]
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In the case of an inter-server copy or an intra-server copy between
file systems, the attributes supported for the source file and
destination file could be different. By definition,the REQUIRED
attributes will be supported in all cases. If the metadata flag is
set and the source file has a RECOMMENDED attribute that is not
supported for the destination file, the copy MUST fail with
NFS4ERR_ATTRNOTSUPP.
Any attribute supported by the destination server that is not set on
the source file SHOULD be left unset.
Metadata attributes not exposed via the NFS protocol SHOULD be copied
to the destination file where appropriate.
The destination file's named attributes are not duplicated from the
source file. After the copy process completes, the client MAY
attempt to duplicate named attributes using standard NFSv4
operations. However, the destination file's named attribute
capabilities MAY be different from the source file's named attribute
capabilities.
If the metadata flag is not set and the client is requesting a whole
file copy (i.e. ca_count is 0 (zero)), the destination file's
metadata is implementation dependent.
If the client is requesting a partial file copy (i.e. ca_count is not
0 (zero)), the client SHOULD NOT set the metadata flag and the server
MUST ignore the metadata flag.
If the operation does not result in an immediate failure, the server
will return NFS4_OK, and the CURRENT_FH will remain the destination's
filehandle.
If an immediate failure does occur, cr_bytes_copied will be set to
the number of bytes copied to the destination file before the error
occurred. The cr_bytes_copied value indicates the number of bytes
copied but not which specific bytes have been copied.
A return of NFS4_OK indicates that either the operation is complete
or the operation was initiated and a callback will be used to deliver
the final status of the operation.
If the cr_callback_id is returned, this indicates that the operation
was initiated and a CB_COPY callback will deliver the final results
of the operation. The cr_callback_id stateid is termed a copy
stateid in this context. The server is given the option of returning
the results in a callback because the data may require a relatively
long period of time to copy.
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If no cr_callback_id is returned, the operation completed
synchronously and no callback will be issued by the server. The
completion status of the operation is indicated by cr_status.
If the copy completes successfully, either synchronously or
asynchronously, the data copied from the source file to the
destination file MUST appear identical to the NFS client. However,
the NFS server's on disk representation of the data in the source
file and destination file MAY differ. For example, the NFS server
might encrypt, compress, deduplicate, or otherwise represent the on
disk data in the source and destination file differently.
In the event of a failure the state of the destination file is
implementation dependent. The COPY operation may fail for the
following reasons (this is a partial list).
NFS4ERR_MOVED: The file system which contains the source file, or
the destination file or directory is not present. The client can
determine the correct location and reissue the operation with the
correct location.
NFS4ERR_NOTSUPP: The copy offload operation is not supported by the
NFS server receiving this request.
NFS4ERR_PARTNER_NOTSUPP: The remote server does not support the
server-to-server copy offload protocol.
NFS4ERR_PARTNER_NO_AUTH: The remote server does not authorize a
server-to-server copy offload operation. This may be due to the
client's failure to send the COPY_NOTIFY operation to the remote
server, the remote server receiving a server-to-server copy
offload request after the copy lease time expired, or for some
other permission problem.
NFS4ERR_FBIG: The copy operation would have caused the file to grow
beyond the server's limit.
NFS4ERR_NOTDIR: The CURRENT_FH is a file and ca_destination has non-
zero length.
NFS4ERR_WRONG_TYPE: The SAVED_FH is not a regular file.
NFS4ERR_ISDIR: The CURRENT_FH is a directory and ca_destination has
zero length.
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NFS4ERR_INVAL: The source offset or offset plus count are greater
than or equal to the size of the source file.
NFS4ERR_DELAY: The server does not have the resources to perform the
copy operation at the current time. The client should retry the
operation sometime in the future.
NFS4ERR_METADATA_NOTSUPP: The destination file cannot support the
same metadata as the source file.
NFS4ERR_WRONGSEC: The security mechanism being used by the client
does not match the server's security policy.
4.5. Operation X: COPY_ABORT - Cancel a server-side copy
ARGUMENTS
struct COPY_ABORT4args {
/* CURRENT_FH: destination file */
stateid4 caa_stateid;
};
RESULTS
struct COPY_ABORT4res {
nfsstat4 car_status;
};
DESCRIPTION
COPY_ABORT is used for both intra- and inter-server asynchronous
copies. The COPY_ABORT operation allows the client to cancel a
server-side copy operation that it initiated. This operation is sent
in a COMPOUND request from the client to the destination server.
This operation may be used to cancel a copy when the application that
requested the copy exits before the operation is completed or for
some other reason.
The request contains the filehandle and copy stateid cookies that act
as the context for the previously initiated copy operation.
The result's car_status field indicates whether the cancel was
successful or not. A value of NFS4_OK indicates that the copy
operation was canceled and no callback will be issued by the server.
A copy operation that is successfully canceled may result in none,
some, or all of the data copied.
If the server supports asynchronous copies, the server is REQUIRED to
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support the COPY_ABORT operation.
The COPY_ABORT operation may fail for the following reasons (this is
a partial list):
NFS4ERR_NOTSUPP: The abort operation is not supported by the NFS
server receiving this request.
NFS4ERR_RETRY: The abort failed, but a retry at some time in the
future MAY succeed.
NFS4ERR_COMPLETE_ALREADY: The abort failed, and a callback will
deliver the results of the copy operation.
NFS4ERR_SERVERFAULT: An error occurred on the server that does not
map to a specific error code.
4.6. Operation Y: COPY_STATUS - Poll for status of a server-side copy
ARGUMENTS
struct COPY_STATUS4args {
/* CURRENT_FH: destination file */
stateid4 csa_stateid;
};
RESULTS
union COPY_STATUS4res switch (nfsstat4 csr_status) {
case NFS4_OK:
length4 csr_bytes_copied;
nfsstat4 csr_complete<1>;
default:
void;
};
DESCRIPTION
COPY_STATUS is used for both intra- and inter-server asynchronous
copies. The COPY_STATUS operation allows the client to poll the
server to determine the status of an asynchronous copy operation.
This operation is sent by the client to the destination server.
If this operation is successful, the number of bytes copied are
returned to the client in the csr_bytes_copied field. The
csr_bytes_copied value indicates the number of bytes copied but not
which specific bytes have been copied.
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If the optional csr_complete field is present, the copy has
completed. In this case the status value indicates the result of the
asynchronous copy operation. In all cases, the server will also
deliver the final results of the asynchronous copy in a CB_COPY
operation.
The failure of this operation does not indicate the result of the
asynchronous copy in any way.
If the server supports asynchronous copies, the server is REQUIRED to
support the COPY_STATUS operation.
The COPY_STATUS operation may fail for the following reasons (this is
a partial list):
NFS4ERR_NOTSUPP: The copy status operation is not supported by the
NFS server receiving this request.
NFS4ERR_BAD_STATEID: The stateid is not valid (see Section 4.8
below).
NFS4ERR_EXPIRED: The stateid has expired (see Copy Offload Stateid
section below).
4.7. Operation Z: CB_COPY - Report results of a server-side copy
ARGUMENTS
union copy_info4 switch (nfsstat4 cca_status) {
case NFS4_OK:
void;
default:
length4 cca_bytes_copied;
};
struct CB_COPY4args {
nfs_fh4 cca_fh;
stateid4 cca_stateid;
copy_info4 cca_copy_info;
};
RESULTS
struct CB_COPY4res {
nfsstat4 ccr_status;
};
DESCRIPTION
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CB_COPY is used for both intra- and inter-server asynchronous copies.
The CB_COPY callback informs the client of the result of an
asynchronous server-side copy. This operation is sent by the
destination server to the client in a CB_COMPOUND request. The copy
is identified by the filehandle and stateid arguments. The result is
indicated by the status field. If the copy failed, cca_bytes_copied
contains the number of bytes copied before the failure occurred. The
cca_bytes_copied value indicates the number of bytes copied but not
which specific bytes have been copied.
In the absence of an established backchannel, the server cannot
signal the completion of the COPY via a CB_COPY callback. The loss
of a callback channel would be indicated by the server setting the
SEQ4_STATUS_CB_PATH_DOWN flag in the sr_status_flags field of the
SEQUENCE operation. The client must re-establish the callback
channel to receive the status of the COPY operation. Prolonged loss
of the callback channel could result in the server dropping the COPY
operation state and invalidating the copy stateid.
If the client supports the COPY operation, the client is REQUIRED to
support the CB_COPY operation.
The CB_COPY operation may fail for the following reasons (this is a
partial list):
NFS4ERR_NOTSUPP: The copy offload operation is not supported by the
NFS client receiving this request.
4.8. Copy Offload Stateids
A server may perform a copy offload operation asynchronously. An
asynchronous copy is tracked using a copy offload stateid. Copy
offload stateids are included in the COPY, COPY_ABORT, COPY_STATUS,
and CB_COPY operations.
Section 8.2.4 of [RFC5661] specifies that stateids are valid until
either (A) the client or server restart or (B) the client returns the
resource.
A copy offload stateid will be valid until either (A) the client or
server restart or (B) the client returns the resource by issuing a
COPY_ABORT operation or the client replies to a CB_COPY operation.
A copy offload stateid's seqid MUST NOT be 0 (zero). In the context
of a copy offload operation, it is ambiguous to indicate the most
recent copy offload operation using a stateid with seqid of 0 (zero).
Therefore a copy offload stateid with seqid of 0 (zero) MUST be
considered invalid.
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5. Security Considerations
The security considerations pertaining to NFSv4 [RFC3530] apply to
this document.
The standard security mechanisms provide by NFSv4 [RFC3530] may be
used to secure the protocol described in this document.
NFSv4 clients and servers supporting the the inter-server copy
operations described in this document are REQUIRED to implement
[RPCSEC_GSSv3], including the RPCSEC_GSSv3 privileges copy_from_auth
and copy_to_auth. If the server-to-server copy protocol is ONC RPC
based, the servers are also REQUIRED to implement the RPCSEC_GSSv3
privilege copy_confirm_auth. These requirements to implement are not
requirements to use. NFSv4 clients and servers are RECOMMENDED to
use [RPCSEC_GSSv3] to secure server-side copy operations.
5.1. Inter-Server Copy Security
5.1.1. Requirements for Secure Inter-Server Copy
Inter-server copy is driven by several requirements:
o The specification MUST NOT mandate an inter-server copy protocol.
There are many ways to copy data. Some will be more optimal than
others depending on the identities of the source server and
destination server. For example the source and destination
servers might be two nodes sharing a common file system format for
the source and destination file systems. Thus the source and
destination are in an ideal position to efficiently render the
image of the source file to the destination file by replicating
the file system formats at the block level. In other cases, the
source and destination might be two nodes sharing a common storage
area network, and thus there is no need to copy any data at all,
and instead ownership of the file and its contents simply gets re-
assigned to the destination.
o The specification MUST provide guidance for using NFSv4.x as a
copy protocol. For those source and destination servers willing
to use NFSv4.x there are specific security considerations that
this specification can and does address.
o The specification MUST NOT mandate pre-configuration between the
source and destination server. Requiring that the source and
destination first have a "copying relationship" increases the
administrative burden. However the specification MUST NOT
preclude implementations that require pre-configuration.
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o The specification MUST NOT mandate a trust relationship between
the source and destination server. The NFSv4 security model
requires mutual authentication between a principal on an NFS
client and a principal on an NFS server. This model MUST continue
with the introduction of COPY.
5.1.2. Inter-Server Copy with RPCSEC_GSSv3
When the client sends a COPY_NOTIFY to the source server to expect
the destination to attempt to copy data from the source server, it is
expected that this copy is being done on behalf of the principal
(called the "user principal") that sent the RPC request that encloses
the COMPOUND procedure that contains the COPY_NOTIFY operation. The
user principal is identified by the RPC credentials. A mechanism
that allows the user principal to authorize the destination server to
perform the copy in a manner that lets the source server properly
authenticate the destination's copy, and without allowing the
destination to exceed its authorization is necessary.
An approach that sends delegated credentials of the client's user
principal to the destination server is not used for the following
reasons. If the client's user delegated its credentials, the
destination would authenticate as the user principal. If the
destination were using the NFSv4 protocol to perform the copy, then
the source server would authenticate the destination server as the
user principal, and the file copy would securely proceed. However,
this approach would allow the destination server to copy other files.
The user principal would have to trust the destination server to not
do so. This is counter to the requirements, and therefore is not
considered. Instead an approach using RPCSEC_GSSv3 [RPCSEC_GSSv3]
privileges is proposed.
One of the stated applications of the proposed RPCSEC_GSSv3 protocol
is compound client host and user authentication [+ privilege
assertion]. For inter-server file copy, we require compound NFS
server host and user authentication [+ privilege assertion]. The
distinction between the two is one without meaning.
RPCSEC_GSSv3 introduces the notion of privileges. We define three
privileges:
copy_from_auth: A user principal is authorizing a source principal
("nfs@<source>") to allow a destination principal ("nfs@
<destination>") to copy a file from the source to the destination.
This privilege is established on the source server before the user
principal sends a COPY_NOTIFY operation to the source server.
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typedef string secret4<>;
struct copy_from_auth_priv {
secret4 cfap_shared_secret;
netloc4 cfap_destination;
/* the NFSv4 user name that the user principal maps to */
utf8str_mixed cfap_username;
/* equal to seq_num of rpc_gss_cred_vers_3_t */
unsigned int cfap_seq_num;
};
cap_shared_secret is a secret value the user principal generates.
copy_to_auth: A user principal is authorizing a destination
principal ("nfs@<destination>") to allow it to copy a file from
the source to the destination. This privilege is established on
the destination server before the user principal sends a COPY
operation to the destination server.
struct copy_to_auth_priv {
/* equal to cfap_shared_secret */
secret4 ctap_shared_secret;
netloc4 ctap_source;
/* the NFSv4 user name that the user principal maps to */
utf8str_mixed ctap_username;
/* equal to seq_num of rpc_gss_cred_vers_3_t */
unsigned int ctap_seq_num;
};
ctap_shared_secret is a secret value the user principal generated
and was used to establish the copy_from_auth privilege with the
source principal.
copy_confirm_auth: A destination principal is confirming with the
source principal that it is authorized to copy data from the
source on behalf of the user principal. When the inter-server
copy protocol is NFSv4, or for that matter, any protocol capable
of being secured via RPCSEC_GSSv3 (i.e. any ONC RPC protocol),
this privilege is established before the file is copied from the
source to the destination.
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struct copy_confirm_auth_priv {
/* equal to GSS_GetMIC() of cfap_shared_secret */
opaque ccap_shared_secret_mic<>;
/* the NFSv4 user name that the user principal maps to */
utf8str_mixed ccap_username;
/* equal to seq_num of rpc_gss_cred_vers_3_t */
unsigned int ccap_seq_num;
};
5.1.2.1. Establishing a Security Context
When the user principal wants to COPY a file between two servers, if
it has not established copy_from_auth and copy_to_auth privileges on
the servers, it establishes them:
o The user principal generates a secret it will share with the two
servers. This shared secret will be placed in the
cfap_shared_secret and ctap_shared_secret fields of the
appropriate privilege data types, copy_from_auth_priv and
copy_to_auth_priv.
o An instance of copy_from_auth_priv is filled in with the shared
secret, the destination server, and the NFSv4 user id of the user
principal. It will be sent with an RPCSEC_GSS3_CREATE procedure,
and so cfap_seq_num is set to the seq_num of the credential of the
RPCSEC_GSS3_CREATE procedure. Because cfap_shared_secret is a
secret, after XDR encoding copy_from_auth_priv, GSS_Wrap() (with
privacy) is invoked on copy_from_auth_priv. The
RPCSEC_GSS3_CREATE procedure's arguments are:
struct {
rpc_gss3_gss_binding *compound_binding;
rpc_gss3_chan_binding *chan_binding_mic;
rpc_gss3_assertion assertions<>;
rpc_gss3_extension extensions<>;
} rpc_gss3_create_args;
The string "copy_from_auth" is placed in assertions[0].privs. The
output of GSS_Wrap() is placed in extensions[0].data. The field
extensions[0].critical is set to TRUE. The source server calls
GSS_Unwrap() on the privilege, and verifies that the seq_num
matches the credential. It then verifies that the NFSv4 user id
being asserted matches the source server's mapping of the user
principal. If it does, the privilege is established on the source
server as: <"copy_from_auth", user id, destination>. The
successful reply to RPCSEC_GSS3_CREATE has:
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struct {
opaque handle<>;
rpc_gss3_chan_binding *chan_binding_mic;
rpc_gss3_assertion granted_assertions<>;
rpc_gss3_assertion server_assertions<>;
rpc_gss3_extension extensions<>;
} rpc_gss3_create_res;
The field "handle" is the RPCSEC_GSSv3 handle that the client will
use on COPY_NOTIFY requests involving the source and destination
server. granted_assertions[0].privs will be equal to
"copy_from_auth". The server will return a GSS_Wrap() of
copy_to_auth_priv.
o An instance of copy_to_auth_priv is filled in with the shared
secret, the source server, and the NFSv4 user id. It will be sent
with an RPCSEC_GSS3_CREATE procedure, and so ctap_seq_num is set
to the seq_num of the credential of the RPCSEC_GSS3_CREATE
procedure. Because ctap_shared_secret is a secret, after XDR
encoding copy_to_auth_priv, GSS_Wrap() is invoked on
copy_to_auth_priv. The RPCSEC_GSS3_CREATE procedure's arguments
are:
struct {
rpc_gss3_gss_binding *compound_binding;
rpc_gss3_chan_binding *chan_binding_mic;
rpc_gss3_assertion assertions<>;
rpc_gss3_extension extensions<>;
} rpc_gss3_create_args;
The string "copy_to_auth" is placed in assertions[0].privs. The
output of GSS_Wrap() is placed in extensions[0].data. The field
extensions[0].critical is set to TRUE. After unwrapping,
verifying the seq_num, and the user principal to NFSv4 user ID
mapping, the destination establishes a privilege of
<"copy_to_auth", user id, source>. The successful reply to
RPCSEC_GSS3_CREATE has:
struct {
opaque handle<>;
rpc_gss3_chan_binding *chan_binding_mic;
rpc_gss3_assertion granted_assertions<>;
rpc_gss3_assertion server_assertions<>;
rpc_gss3_extension extensions<>;
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} rpc_gss3_create_res;
The field "handle" is the RPCSEC_GSSv3 handle that the client will
use on COPY requests involving the source and destination server.
The field granted_assertions[0].privs will be equal to
"copy_to_auth". The server will return a GSS_Wrap() of
copy_to_auth_priv.
5.1.2.2. Starting a Secure Inter-Server Copy
When the client sends a COPY_NOTIFY request to the source server, it
uses the privileged "copy_from_auth" RPCSEC_GSSv3 handle.
cna_destination_server in COPY_NOTIFY MUST be the same as the name of
the destination server specified in copy_from_auth_priv. Otherwise,
COPY_NOTIFY will fail with NFS4ERR_ACCESS. The source server
verifies that the privilege <"copy_from_auth", user id, destination>
exists, and annotates it with the source filehandle, if the user
principal has read access to the source file, and if administrative
policies give the user principal and the NFS client read access to
the source file (i.e. if the ACCESS operation would grant read
access). Otherwise, COPY_NOTIFY will fail with NFS4ERR_ACCESS.
When the client sends a COPY request to the destination server, it
uses the privileged "copy_to_auth" RPCSEC_GSSv3 handle.
ca_source_server in COPY MUST be the same as the name of the source
server specified in copy_to_auth_priv. Otherwise, COPY will fail
with NFS4ERR_ACCESS. The destination server verifies that the
privilege <"copy_to_auth", user id, source> exists, and annotates it
with the source and destination filehandles. If the client has
failed to establish the "copy_to_auth" policy it will reject the
request with NFS4ERR_PARTNER_NO_AUTH.
If the client sends a COPY_REVOKE to the source server to rescind the
destination server's copy privilege, it uses the privileged
"copy_from_auth" RPCSEC_GSSv3 handle and the cra_destination_server
in COPY_REVOKE MUST be the same as the name of the destination server
specified in copy_from_auth_priv. The source server will then delete
the <"copy_from_auth", user id, destination> privilege and fail any
subsequent copy requests sent under the auspices of this privilege
from the destination server.
5.1.2.3. Securing ONC RPC Server-to-Server Copy Protocols
After a destination server has a "copy_to_auth" privilege established
on it, and it receives a COPY request, if it knows it will use an ONC
RPC protocol to copy data, it will establish a "copy_confirm_auth"
privilege on the source server, using nfs@<destination> as the
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initiator principal, and nfs@<source> as the target principal.
The value of the field ccap_shared_secret_mic is a GSS_VerifyMIC() of
the shared secret passed in the copy_to_auth privilege. The field
ccap_username is the mapping of the user principal to an NFSv4 user
name ("user"@"domain" form), and MUST be the same as ctap_username
and cfap_username. The field ccap_seq_num is the seq_num of the
RPCSEC_GSSv3 credential used for the RPCSEC_GSS3_CREATE procedure the
destination will send to the source server to establish the
privilege.
The source server verifies the privilege, and establishes a
<"copy_confirm_auth", user id, destination> privilege. If the source
server fails to verify the privilege, the COPY operation will be
rejected with NFS4ERR_PARTNER_NO_AUTH. All subsequent ONC RPC
requests sent from the destination to copy data from the source to
the destination will use the RPCSEC_GSSv3 handle returned by the
source's RPCSEC_GSS3_CREATE response.
Note that the use of the "copy_confirm_auth" privilege accomplishes
the following:
o if a protocol like NFS is being used, with export policies, export
policies can be overridden in case the destination server as-an-
NFS-client is not authorized
o manual configuration to allow a copy relationship between the
source and destination is not needed.
If the attempt to establish a "copy_confirm_auth" privilege fails,
then when the user principal sends a COPY request to destination, the
destination server will reject it with NFS4ERR_PARTNER_NO_AUTH.
5.1.2.4. Securing Non ONC RPC Server-to-Server Copy Protocols
If the destination won't be using ONC RPC to copy the data, then the
source and destination are using an unspecified copy protocol. The
destination could use the shared secret and the NFSv4 user id to
prove to the source server that the user principal has authorized the
copy.
For protocols that authenticate user names with passwords (e.g. HTTP
[RFC2616] and FTP [RFC0959]), the nfsv4 user id could be used as the
user name, and an ASCII hexadecimal representation of the
RPCSEC_GSSv3 shared secret could be used as the user password or as
input into non-password authentication methods like CHAP [RFC1994].
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5.1.3. Inter-Server Copy via ONC RPC but without RPCSEC_GSSv3
ONC RPC security flavors other than RPCSEC_GSSv3 MAY be used with the
server-side copy offload operations described in this document. In
particular, host-based ONC RPC security flavors such as AUTH_NONE and
AUTH_SYS MAY be used. If a host-based security flavor is used, a
minimal level of protection for the server-to-server copy protocol is
possible.
In the absence of strong security mechanisms such as RPCSEC_GSSv3,
the challenge is how the source server and destination server
identify themselves to each other, especially in the presence of
multi-homed source and destination servers. In a multi-homed
environment, the destination server might not contact the source
server from the same network address specified by the client in the
COPY_NOTIFY. This can be overcome using the procedure described
below.
When the client sends the source server the COPY_NOTIFY operation,
the source server may reply to the client with a list of target
addresses, names, and/or URLs and assign them to the unique triple:
<source fh, user ID, destination address Y>. If the destination uses
one of these target netlocs to contact the source server, the source
server will be able to uniquely identify the destination server, even
if the destination server does not connect from the address specified
by the client in COPY_NOTIFY.
For example, suppose the network topology is as shown in Figure 3.
If the source filehandle is 0x12345, the source server may respond to
a COPY_NOTIFY for destination 10.11.78.56 with the URLs:
nfs://10.11.78.18//_COPY/10.11.78.56/_FH/0x12345
nfs://192.168.33.18//_COPY/10.11.78.56/_FH/0x12345
The client will then send these URLs to the destination server in the
COPY operation. Suppose that the 192.168.33.0/24 network is a high
speed network and the destination server decides to transfer the file
over this network. If the destination contacts the source server
from 192.168.33.56 over this network using NFSv4.1, it does the
following:
COMPOUND { PUTROOTFH, LOOKUP "_COPY" ; LOOKUP "10.11.78.56"; LOOKUP
"_FH" ; OPEN "0x12345" ; GETFH }
The source server will therefore know that these NFSv4.1 operations
are being issued by the destination server identified in the
COPY_NOTIFY.
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5.1.4. Inter-Server Copy without ONC RPC and RPCSEC_GSSv3
The same techniques as Section 5.1.3, using unique URLs for each
destination server, can be used for other protocols (e.g. HTTP
[RFC2616] and FTP [RFC0959]) as well.
6. IANA Considerations
This document has no actions for IANA.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
Beame, C., Eisler, M., and D. Noveck, "Network File System
(NFS) version 4 Protocol", RFC 3530, April 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5661] Shepler, S., Eisler, M., and D. Noveck, "Network File
System (NFS) Version 4 Minor Version 1 Protocol",
RFC 5661, January 2010.
[RPCSEC_GSSv3]
Williams, N., "Remote Procedure Call (RPC) Security
Version 3", draft-williams-rpcsecgssv3 (work in progress),
2008.
7.2. Informational References
[FEDFS-ADMIN]
Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
Naik, "Administration Protocol for Federated Filesystems",
draft-ietf-nfsv4-federated-fs-admin (Work In Progress),
2010.
[FEDFS-NSDB]
Lentini, J., Everhart, C., Ellard, D., Tewari, R., and M.
Naik, "NSDB Protocol for Federated Filesystems",
draft-ietf-nfsv4-federated-fs-protocol (Work In Progress),
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2010.
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[RFC1994] Simpson, W., "PPP Challenge Handshake Authentication
Protocol (CHAP)", RFC 1994, August 1996.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[SPACE-RESERVE]
Eisler, M., Kenchammana, D., Lentini, J., Shankararao, M.,
and R. Iyer, "NFS space reservation operations",
draft-iyer-nfsv4-space-reservation-ops (work in progress),
2010.
Appendix A. Acknowledgments
Tom Talpey co-authored an unpublished version of this document. We
thank Tom for his contributions, especially with regards to the
asynchronous completion callback mechanism.
This document was reviewed by a number of individuals. We would like
to thank Pranoop Erasani, Tom Haynes, Arthur Lent, Trond Myklebust,
Dave Noveck, Theresa Lingutla-Raj, Manjunath Shankararao, Satyam
Vaghani, and Nico Williams for their input and advice.
Authors' Addresses
James Lentini
NetApp
1601 Trapelo Rd, Suite 16
Waltham, MA 02451
USA
Phone: +1 781-768-5359
Email: jlentini@netapp.com
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Mike Eisler
NetApp
5765 Chase Point Circle
Colorado Springs, CO 80919
USA
Phone: +1 719-599-9026
Email: mike@eisler.com
URI: http://www.eisler.com
Deepak Kenchammana
NetApp
475 East Java Drive
Sunnyvale, CA 94089
USA
Phone: +1 408-822-4765
Email: kencham@netapp.com
Anshul Madan
Carnegie Mellon University
School of Computer Science
5000 Forbes Avenue
Pittsburgh, PA 15213
USA
Email: anshulmadan@cmu.edu
Rahul Iyer
655 S Fair Oaks Ave
Apt #I-314
Sunnyvale, CA 94086
USA
Email: rahulair@yahoo.com
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