netdev - Re: [Patch net v3] mlx5: force CHECKSUM

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Date:   Tue, 4 Dec 2018 13:20:57 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     saeedm@....mellanox.co.il, Eric Dumazet <edumazet@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [Patch net v3] mlx5: force CHECKSUM_NONE for short ethernet frames

On Tue, Dec 4, 2018 at 1:16 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> Erm I never suggested to get rid of CHECKSUM_COMPLETE...
> My suggestion was to reorder the mlx5 logic to match mlx4 one.
>
> CHECKSUM_COMPLETE is very nice _when_/_if_ the NIC is unable to
> fully dissect a packet and validate L4, as a fallback.

Quote from Eric:

"For native IP+TCP or IP+UDP, the NIC has the ability to fully
understand the packet and fully validate the checksum."

Therefore CHECKSUM_COMPLETE is not nice here.

>
> I am pretty sure for example that IP reassembly can benefit from CHECKSUM_COMPLETE.
> (Although for some reason mlx4 code does not handle IPv6 fragments in its CHECKSUM_COMPLETE path)
>

I am pretty sure mlx5 driver code doesn't check for IP fragments.


My patch is dropped, let's keep the current code as it is and pretend
everything just works fine.

Thanks a lot!