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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
	Saeed Mahameed <saeedm@mellanox.com>,
	Eric Dumazet <edumazet@google.com>
Subject: Re: [Patch net] mlx5: fixup checksum for ethernet padding
Date: Tue, 27 Nov 2018 17:42:33 -0800	[thread overview]
Message-ID: <CAM_iQpWc82LG4b40XZCypP+SFYX9LCm2GCaMaG_xfU87h7SOow@mail.gmail.com> (raw)
In-Reply-To: <0e6a8a08-b181-b17a-1330-0159808e9a42@gmail.com>

On Tue, Nov 27, 2018 at 5:25 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 11/27/2018 04:07 PM, Cong Wang wrote:
> > On Tue, Nov 27, 2018 at 3:48 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> >>
> >> But the padding might be added on normal packets (say 1000 bytes + 3 bytes of padding) ?
> >
> > I never see other padding cases than ETH_ZLEN. Does ethernet standard
> > require padding for other cases? I only read the section "3.2.8 Pad field" in
> > the standard.
> >
>
> Padding can be done by senders, eg using AF_PACKET,
> added at the tail of a regular IP/IP6 frame of 1000 or 6000 bytes.


I tried the trafgen script you provided, it doesn't trigger any checksum fault.
So, it is probably a different case.

>
> Note that mlx5 will presumably set CHECKSUM_UNNECESSARY for standard protocols,
> so if you want to reproduce the issue, you might need to find an IP frame that
> mlx5 is not able to checksum validate.

This warning is 100% reproducible with a TCP RST packet (no data)
here, after I find the right switch which pads non-zero's. This is
also how I verified this patch.

Thanks.

  reply	other threads:[~2018-11-28 12:42 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-27 23:21 [Patch net] mlx5: fixup checksum for ethernet padding Cong Wang
2018-11-27 23:23 ` Cong Wang
2018-11-27 23:48 ` Eric Dumazet
2018-11-28  0:07   ` Cong Wang
2018-11-28  1:11     ` Saeed Mahameed
2018-11-28  1:38       ` Cong Wang
2018-11-28  1:25     ` Eric Dumazet
2018-11-28  1:42       ` Cong Wang [this message]
2018-11-28  1:48         ` Eric Dumazet
2018-11-28  1:52           ` Cong Wang
2018-11-29 21:51 ` kbuild test robot

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