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

From: Stephen Hemminger
Date: Mon Jan 15 2007 - 13:19:47 EST


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