[PATCH 0/4][SRU][focal:linux] NFSv4.1: Don't rebind to the same source port when reconnecting to the server

[Khaled Elmously]

On 2022-11-23 06:20:28 , Tim Gardner wrote:
> On 11/22/22 2:11 PM, Khaled Elmously wrote:
> > On 2022-11-22 13:39:10 , Tim Gardner wrote:
> > > BugLink: https://bugs.launchpad.net/bugs/1997488
> > > 
> > > SRU Justification
> > > 
> > > Microsoft asked for this backport complaining that,
> > > "NFS 4.1 mounts on AKS are reusing the same source port when a reconnect needs to happen".
> > > 
> > > Patches 1-3 are scaffolding in order to provide a clean cherrypick for patch 4.
> > > This issue looks applicable to the generic kernel.
> > > 
> > > [Impact]
> > > 
> > > NFSv2, v3 and NFSv4 servers often have duplicate replay caches that look
> > > at the source port when deciding whether or not an RPC call is a replay
> > > of a previous call. This requires clients to perform strange TCP gymnastics
> > > in order to ensure that when they reconnect to the server, they bind
> > > to the same source port.
> > > 
> > > NFSv4.1 and NFSv4.2 have sessions that provide proper replay semantics,
> > > that do not look at the source port of the connection. This patch therefore
> > > ensures they can ignore the rebind requirement.
> > > 
> > > [Where things could go wrong]
> > > 
> > > NFS reconnects may erroneously fail.
> > > 
> > > [Other Info]
> > > 
> > > SF: #00345839
> > > 
> > 
> > Would this not cause issues for users that run NFSv < 4.1 who don't have proper replay semantics and still rely on source-port reuse?
> > 
> 
> Aren't NFS version updates backwards compatible ?

Yes, you're right.

--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -880,8 +880,11 @@ static int nfs4_set_client(struct nfs_server *server,
        };
        struct nfs_client *clp;

-       if (minorversion > 0 && proto == XPRT_TRANSPORT_TCP)
+       if (minorversion == 0)
+               __set_bit(NFS_CS_REUSEPORT, &cl_init.init_flags);
+       else if (proto == XPRT_TRANSPORT_TCP)
                cl_init.nconnect = nconnect;



Sorry ignore the noise.


> 
> -- 
> -----------
> Tim Gardner
> Canonical, Inc
>