netdev - Re: skb_warn_bad_offload related to IPv6 in 3.9.9+

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Message-ID: <1373578657.2085.20.camel@bwh-desktop.uk.level5networks.com>
Date:	Thu, 11 Jul 2013 22:37:37 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Ben Greear <greearb@...delatech.com>
CC:	netdev <netdev@...r.kernel.org>
Subject: Re: skb_warn_bad_offload related to IPv6 in 3.9.9+

On Thu, 2013-07-11 at 11:52 -0700, Ben Greear wrote:
> This kernel has local patches applied...but I don't think it has anything
> that would cause this....
> 
> The wanlink module is something we added.  It is now GPL, but code is
> not upstream.  I don't think it's in directly related to the splat though...
>
> Only saw one splat, and system remains stable as far as we can tell.
>
> ------------[ cut here ]------------
> WARNING: at /home/greearb/git/linux-3.9.dev.y/net/core/dev.c:2179 skb_warn_bad_offload+0xc2/0xcb()
> Hardware name: X7DBU
> e1000e: caps=(0x00000000700003a9, 0x0000000000000000) len=2942 data_len=1428 gso_size=1428 gso_type=16 ip_summed=1
[...]

The skb requires TSO, which requires that ip_summed = CHECKSUM_PARTIAL.
But ip_summed = CHECKSUM_UNNECESSARY.

To me, this suggests that the receiving device i.e. wanlink has some
kind of broken LRO that can't be turned off...

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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