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Date:      Fri, 3 Apr 2009 08:25:08 -0300
From:      "Luiz Otavio O Souza" <lists.br@gmail.com>
To:        <freebsd-hackers@freebsd.org>
Subject:   Re: Setting the mss for socket
Message-ID:  <64D5D9E633734200A603D067ED5A81E9@adnote989>
References:  <3FD46C21A487490FB15B89E890790121@adnote989> <49d5c0de.E5bkeKr%2Bp%2Bfg4K00%perryh@pluto.rain.com>

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>> Is there a way to set the mss for a socket ? Like you can do
>> in linux with setsockopt(TCP_MAXSEG) ?
>>
>> So i can set the maximum size of packets (or sort of) from a
>> simple userland program.
>
> Depending on exactly what you need to accomplish, you may
> find something useful in this thread from last August in
> freebsd-questions@
>
>  setting the other end's TCP segment size

Very informative thread, thanks.

This thread show me that TCP_MAXSEG is implemented in freebsd but don't
work. You can set the setsockopt(IPPROTO_TCP, TCP_MAXSEG), wich will set the
tp->t_maxseg, but this value is recalculated at tcp_input, so in short, you
cannot set the max segment size for a socket.

I've posted a completly wrong patch (from style point-of-view - and using
SOL_SOCKET instead of IPPROTO_TCP), but with that patch i'm able to set the
mss in iperf.

Many thanks,
Luiz




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