netdev - Re: Fw: [Bug 201423] New: eth0: hw csum failure

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Date:   Sun, 21 Oct 2018 15:34:19 +0200
From:   Andre Tomt <andre@...t.net>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        netdev <netdev@...r.kernel.org>, rossi.f@...ind.it,
        Dimitris Michailidis <dmichail@...gle.com>
Subject: Re: Fw: [Bug 201423] New: eth0: hw csum failure

On 20.10.2018 00:25, Eric Dumazet wrote:
> On 10/19/2018 02:58 PM, Eric Dumazet wrote:
>> On 10/16/2018 06:00 AM, Eric Dumazet wrote:
>>> On Mon, Oct 15, 2018 at 11:30 PM Andre Tomt <andre@...t.net> wrote:
>>>> I've seen similar on several systems with mlx4 cards when using 4.18.x -
>>>> that is hw csum failure followed by some backtrace.
>>>>
>>>> Only seems to happen on systems dealing with quite a bit of UDP.
>>>>
>>>
>>> Strange, because mlx4 on IPv6+UDP should not use CHECKSUM_COMPLETE,
>>> but CHECKSUM_UNNECESSARY
>>>
>>> I would be nice to track this a bit further, maybe by providing the
>>> full packet content.
>>>
<snip>
>>
>> As a matter of fact Dimitris found the issue in the patch and is working on a fix involving csum_block_sub()
>>
>> Problems comes from trimming an odd number of bytes.
> 
> More exactly, trimming bytes starting at an odd offset.

No hw csum failures here since I deployed Dimitris fix on top of 4.18.16 
32 hours ago.

Thanks