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Date:      Sat, 15 Dec 2001 01:04:57 -0800
From:      David Greenman <dg@root.com>
To:        rsharpe@ns.aus.com
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: Does anyone know if the Broadcom BCM5700 has problems with HW csum?
Message-ID:  <20011215010457.B84861@nexus.root.com>
In-Reply-To: <3C1AEA9E.6010502@ns.aus.com>; from sharpe@ns.aus.com on Sat, Dec 15, 2001 at 04:45:58PM %2B1030
References:  <3C1AEA9E.6010502@ns.aus.com>

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>I am playing with a driver for the Broadcom 5700/5701.
>
>It recognizes the 5700 in my 3Com cards OK, but seems to screw up the 
>TCP checksum.
>
>Switching off hardware checksum capability fixes it.
>
>Does anyone know the details of which stepping this stuff worked on?

   I haven't nailed down the problem that I've seen with them to a specific
chipset, but I can confirm that they incorrectly calculate the checksum on
input packets in some cases. It seems to be related to both packet size and
certain TCP options (or lack of them). I've only seen the problem occur with
very small (0-4 byte payload) packets.
   In any case, after discussing this problem with Bill Paul, I disabled
input checksum in the -current driver and intend to merge that to -stable in
a few days.

-DG

David Greenman
Co-founder, The FreeBSD Project - http://www.freebsd.org
President, TeraSolutions, Inc. - http://www.terasolutions.com
Pave the road of life with opportunities.

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