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From:   Rick Macklem <rmacklem@uoguelph.ca>
To:     "nfsv4@ietf.org" <nfsv4@ietf.org>
CC:     "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: what defines a TCP connection as new, requiring
 BindConnectionToSession?
Thread-Topic: what defines a TCP connection as new, requiring
 BindConnectionToSession?
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Date:   Sun, 4 Apr 2021 03:21:34 +0000
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Hi,=0A=
=0A=
I have been doing testing of network partitioning between a=0A=
Linux client (5.2.10) and a FreeBSD server and have observed=0A=
the following:=0A=
- If I unplug a net cable for a few minutes and the plug it=0A=
   back in, the Linux client does a TCP "SYN", expects "SYN, ACK"=0A=
   and then continues on, using the same port# as before the=0A=
   network partitioning.=0A=
--> I had assumed the above created a "new connection" that=0A=
       will only be bound to the backchannel if a=0A=
       BindConnectionToSession is done on it.=0A=
Now I am not sure if this is considered a "new connection" or=0A=
the same connection (same port#) still bound to the back channel?=0A=
=0A=
I am also wondering about this para. in RFC5661 pg. 493:=0A=
   Invoking BIND_CONN_TO_SESSION on a connection already associated with=0A=
   the specified session has no effect, and the server MUST respond with=0A=
   NFS4_OK, unless the client is demanding changes to the set of=0A=
   channels the connection is associated with.  If so, the server MUST=0A=
   return NFS4ERR_INVAL.=0A=
Since a "new connection" is bound to a session's fore channel by=0A=
sending an RPC with Sequence in it, does this imply that a=0A=
BindConnectionToSession done on a connection to bind a back channel=0A=
after an RPC with Sequence in it has been done on the connection,=0A=
must fail with NFS4ERR_INVAL?=0A=
=0A=
As you can see, knowing what constitutes a new TCP connection matters.=0A=
=0A=
Thanks in advance for any help with this, rick=0A=