netdev - Re: [PATCH net] net/mlx4_en: Force CHECKSUM

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Date:   Fri, 1 Feb 2019 00:05:10 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "edumazet@...gle.com" <edumazet@...gle.com>
CC:     Eran Ben Elisha <eranbe@...lanox.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [PATCH net] net/mlx4_en: Force CHECKSUM_NONE for short ethernet
 frames

On Thu, 2019-01-31 at 11:42 -0800, Eric Dumazet wrote:
> On Thu, Jan 31, 2019 at 11:27 AM Saeed Mahameed <saeedm@...lanox.com>
> wrote:
> > Are you sure ? you are claiming that the hardware will skip csum
> > complete i.e cqe->checksum will be 0xffff for padded short IP
> > frames.
> > i don't think this is the case, the whole bug is that the hw does
> > provide a partial cqe->checksum (i.e doesn't included the padding
> > bytes) even for short eth frames.
> 
> If the padding is not included, then cqe->checksum is 0xFFFF for
> correctly received frames.
> 
> Otherwise, what would be cqe->checksum in this case ? A random value
> ?

the actual checksum of IP headers+IP payload, while ignoring the
padding bytes, which is the bug, let me double check..