From mboxrd@z Thu Jan  1 00:00:00 1970
From: Steve Chen <schen@mvista.com>
Subject: Re: TAHI CN-6-4-1 failed on Linux 2.6.32 kernel
Date: Fri, 20 Aug 2010 12:16:38 -0500
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To: David Miller <davem@davemloft.net>
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On Thu, Aug 19, 2010 at 7:06 PM, David Miller <davem@davemloft.net> wro=
te:
> From: Steve Chen <schen@mvista.com>
> Date: Thu, 19 Aug 2010 13:35:14 -0500
>
>> I trace through the code. =A0It appears that the network driver (e10=
00e
>> for my setup) always set ip_summed to CHECKSUM_UNNECESSARY. =A0I hav=
e
>> been unsuccessful to get the driver to take the other branch where
>> ip_summed is set to CHECKSUM_COMPLETE. =A0Even when I hard code
>> ip_summed to CHECKSUM_COMPLETE, __skb_checksum_complete_head set
>> ip_summed to CHECKSUM_UNNECESSARY after recomputing the checksum.
>>
>> So far the only way I'm able to get ICMP to recompute checksum is
>> through the attached hack. =A0Even though I can get all the tests to
>> pass, but it just seem wrong.
>
> If turning off hardware RX checksumming with ethtool has no effect,
> and the problem is seen with multiple ethernet cards, the problem
> is elsewhere.
>
> First of all, if you turn RX checksumming off, the checksum field
> of the SKB should always be skb->ip_summed =3D 0. =A0If this is not
> happening, find out why.

Ahhh, thats my problem.  I incorrectly thought the ip_summed should be
2.  The ip_summed is set to 1 in
__skb_checksum_complete_head.  Looking at the code, shouldn't

if (likely(!sum))

be

if (likely(sum))

Since sum =3D=3D 0 would indicate an error?

Thanks

Steve