Re: Bad UDP checksum with 82540EM

[Andreas Schwab <schwab@suse.de>]

Andi Kleen <ak@suse.de> writes:

> On Sat, 07 Feb 2004 23:42:21 +0100
> Andreas Schwab <schwab@suse.de> wrote:
>
>> Jon D Mason <jonmason@us.ibm.com> writes:
>> 
>> > This probably isn't helpful, but it sounds like a hardware error.  Is the 
>> > error occurring on multiple/all HP adapters, or only one? 
>> 
>> I've also seen it with a HP branded BCM5701 on IA64, but also with a
>> Broadcom BCM5702 on AMD64 (both using the tg3 driver).  It seems like
>> broken UDP checksumming is rather common. :-(
>
> It could be still a software bug.  When hardware checksumming is available
> the UDP packets use a slightly different path through the stack.
>
> Could you perhaps test if the problem occurs in a 32bit box with the 
> same NIC ? Maybe it is some 64bit problem somewhere in software.

Just tested with a "3Com 3C996B-T 1000Base-T" (BCM5701 based, with tg3
driver) on an Athlon.  It shows the same bug, and disabling HW
checksumming on tx fixes it.  So it doesn't look like a 64bit issue.

Andreas.

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Andreas Schwab, SuSE Labs, schwab@suse.de
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