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Date:   Thu, 30 May 2019 20:15:26 -0400
To:     Rick Macklem <rmacklem@uoguelph.ca>
Cc:     Olga Kornievskaia <aglo@umich.edu>, Tom Talpey <tom@talpey.com>,
        NeilBrown <neilb@suse.com>, Chuck Lever <chuck.lever@oracle.com>,
        Schumaker Anna <Anna.Schumaker@netapp.com>,
        Trond Myklebust <trondmy@hammerspace.com>,
        linux-nfs <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 0/9] Multiple network connections for a single NFS mount.
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From:   bfields@fieldses.org (J. Bruce Fields)
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On Thu, May 30, 2019 at 11:53:19PM +0000, Rick Macklem wrote:
> The FreeBSD DRC code for NFS over TCP expects the retry to be from a
> different port# (due to a new connection re: the above) for NFSv4.0.
> For NFSv3, my best recollection is that it doesn't care what the
> source port# is. (It basically uses a hash on the RPC request
> excluding TCP/IP header to recognize possible duplicates.)
> 
> I don't know what other NFS servers choose to do w.r.t. the DRC for
> NFS over TCP, however for some reason I thought that the Linux knfsd
> only used a DRC for UDP?  (Someone please clarify this.)

The knfsd DRC is used for TCP as well as UDP.  It does take into account
the source port.  I don't think we do any TCP-specific optimizations
though I agree that they sound like a good idea.

--b.