Re: [nfsv4] Review of draft-ietf-nfsv4-rfc5667bis-09

[Tom Talpey <[e-mail]>]

On 5/4/2017 11:00 AM, Chuck Lever wrote:
> I've tried to address your concerns, and I changed the segment count
> limit to document what we know about the current Solaris implementations.
> I liked the "be conservative in what you send" idea, but I couldn't find
> a way to work it in that was not awkward.
>
> If this text is OK, I'll submit a fresh I-D revision after WGLC ends on
> Friday.

Well that wasn't enough time for me to respond since I was traveling
from SambaXP in Germany, but the text does look better. The statement
below makes no requirement on the server.

> 5.4.2.  Chunk List Complexity
>...
>    To avoid encountering server chunk list complexity limits, NFS
>    version 4 clients SHOULD follow the below prescriptions when
>    constructing transport headers:
>
>    o  The Read list can contain either a Position-Zero Read chunk, one
>       Read chunk with a non-zero Position, or both.
>
>    o  The Write list can contain no more than one Write chunk.
>
>    o  Any chunk can contain up to sixteen RDMA segments.

I would suggest the following modifications to the above.

   "In accordance with chunk list processing limits of existing
    server implementations, NFS Version 4 clients SHOULD maximally
    follow the below prescriptions when constructing requests to
    be transported by RPC-over-RDMA. Additionally, NFS Version 4
    servers SHOULD minimally be prepared to accept and process such
    requests."

>    NFS version 4 clients wishing to send more complex chunk lists can
>    provide configuration interfaces to bound the complexity of NFS
>    version 4 COMPOUNDs, limit the number of elements in scatter-gather
>    operations, and avoid other sources of RPC-over-RDMA chunk overruns
>    at the receiving peer.
>
>    An NFS Version 4 server has some flexibility in how it indicates that
>    an RPC-over-RDMA Version One message received from an NFS Version 4
>    client is valid but cannot be processed.  Examples include:


Strongly suggest deleting the words "has some flexibility" and "Examples
include". We've already had this discussion, so I will just suggest the
following.

   "An NFS Version 4 server SHOULD return one of the following responses
    to a client which has sent a request containing RPC-over-RDMA chunks
    which cannot be processed due to exceeding server implementation
    limits"


Tom.


>    o  A problem is detected by the transport layer while parsing the
>       transport header in an RPC Call message.  The server responds with
>       an RDMA_ERROR message with the err field set to ERR_CHUNK.
>
>    o  A problem is detected during XDR decoding of the RPC Call message
>       while the RPC layer reassembles the call's XDR stream.  The server
>       responds with an RPC reply with its "reply_stat" field set to
>       MSG_ACCEPTED and its "accept_stat" field set to GARBAGE_ARGS.
>
>    After receiving one of these errors, an NFS version 4 client SHOULD
>    NOT retransmit the failing request, as the result would be the same
>    error.  It SHOULD immediately terminate the RPC transaction
>    associated with the XID in the reply.