netdev - TCP_MAXSEG option with TSO enabled

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Message-ID: <CAEnQRZC1sLW8BUOx2ov-S-UUSyfAi7Wem2mAzUHBHn2o9q-eRg@mail.gmail.com>
Date:	Fri, 30 Mar 2012 14:33:37 +0300
From:	Daniel Baluta <daniel.baluta@...il.com>
To:	netdev@...r.kernel.org
Subject: TCP_MAXSEG option with TSO enabled

Hello,

I am using TCP_MAXSEG option on an interface which has TSO enabled.

strace output for connection looks as follows:

socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 26
setsockopt(26, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
setsockopt(26, SOL_TCP, TCP_NODELAY, [1], 4) = 0
setsockopt(26, SOL_TCP, TCP_MAXSEG, [300], 4) = 0
connect(26, {sa_family=AF_INET, sin_port=htons(1935),
sin_addr=inet_addr("10.10.0.1")}, 16) = -1 EINPROGRESS (Operation now
in progress)

I can see that MSS (300) is advertised in SYN packet, anyhow capturing
the traffic
I notice that are some TCP segments with length greater than MSS.

Is this normal taking in consideration that TSO is enabled?

thanks,
Daniel.
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