netdev - Sending Packet Much Larger Than MSS

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Message-ID: <CAJ2iOjQGrnhG7L1jDAXybJiG7O5OpnaDzw5UBEuN2kEWXYGUnQ@mail.gmail.com>
Date:	Thu, 28 Jun 2012 10:21:01 -0700
From:	"George B." <georgeb@...il.com>
To:	netdev <netdev@...r.kernel.org>
Subject: Sending Packet Much Larger Than MSS

I am troubleshooting an issue and in the course of that noticed that a
machine running  2.6.38-11 (Ubuntu  2.6.38-11-server #48-Ubuntu SMP)
kernel is sending packets larger than the MSS advertized by the remote
host.  The local machine has a large MTU (9000) and the advertized MSS
of the remote machine is 1380 and here we have the local machine
sending a 2560 byte packet.

I have a screen capture of the flow at
http://i46.tinypic.com/10zmgyh.png but it is kind of small.  The
initial MSS shows 1380 and you see the packet highlighted in blue has
a length of 2560.  That it gets accepted and acked is a different
problem but to my mind it should not be sending a packet that large in
the first place.

Is this a known issue with that kernel?

Thanks.

George
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