netdev - Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame padding

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Message-ID: <CALzJLG8Vd3+6Fz=xquBZenswkpxQeVJvY1QY=89W_ynqbr=JtQ@mail.gmail.com>
Date:   Tue, 4 Dec 2018 11:21:12 -0800
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame padding

On Mon, Dec 3, 2018 at 3:17 PM David Miller <davem@...emloft.net> wrote:
>
> From: Cong Wang <xiyou.wangcong@...il.com>
> Date: Tue, 27 Nov 2018 22:10:13 -0800
>
> > When an ethernet frame is padded to meet the minimum ethernet frame
> > size, the padding octets are not covered by the hardware checksum.
> > Fortunately the padding octets are ususally zero's, which don't affect
> > checksum. However, we have a switch which pads non-zero octets, this
> > causes kernel hardware checksum fault repeatedly.
> >
> > Prior to commit 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"),
> > skb checksum is forced to be CHECKSUM_NONE when padding is detected.
> > After it, we need to keep skb->csum updated, like what we do for FCS.
> >
> > The logic is a bit complicated when dealing with both FCS and padding,
> > so I wrap it up in a helper function mlx5e_csum_padding().
> >
> > I tested this patch with RXFCS on and off, it works fine without any
> > warning in both cases.
> >
> > Fixes: 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are friends"),
> > Cc: Saeed Mahameed <saeedm@...lanox.com>
> > Cc: Eric Dumazet <edumazet@...gle.com>
> > Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
>
> Saeed, are you going to take care of this?

Yes, I will take it to mlx5 net branch and submit it to you when it is ready.
Cong just submitted v3 with new title:
[Patch net v3] mlx5: force CHECKSUM_NONE for short ethernet frames

we are still working on it.

Thanks !