linux-kernel - Re: incorrect TCP checksum on sent TCP-MD5 packets (2.6.20-rc5)

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Message-ID: <20070115101522.481e2f8f@freekitty>
Date:	Mon, 15 Jan 2007 10:15:22 -0800
From:	Stephen Hemminger <shemminger@...l.org>
To:	linux-kernel@...r.kernel.org
Subject: Re: incorrect TCP checksum on sent TCP-MD5 packets (2.6.20-rc5)

On Sun, 14 Jan 2007 20:32:34 +0100
Torsten Luettgert <t.luettgert@...ssestimmen.de> wrote:

> Hi,
> 
> I'm using the new TCP-MD5 option in 2.6.20-rc4 and rc5
> to talk BGP to cisco routers.
> My box connects to the cisco, and the handshake looks fine:
> SYN, SYN/ACK, ACK all have md5 option and correct TCP checksums.
> 
> All packets after that, i.e. the ones with payload data,
> have wrong TCP checksums, quoth wireshark.
> The same happens if the cisco connects: the first, "empty" packet
> is ok, packets with payload aren't.
> 
> Am I doing something wrong? Or is this a bug?
> 
> I'll gladly send tcpdumps if it helps.
> 
> Thanks for your help,
> Torsten

Are you running over a device that does checksum offload?


-- 
Stephen Hemminger <shemminger@...l.org>
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