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

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Date:   Tue, 4 Dec 2018 18:52:35 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame padding

On Tue, Nov 27, 2018 at 10:10 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> 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>

Nacked-by: Cong Wang <xiyou.wangcong@...il.com>

This patch has no value for upstream. Let's discard it. Please don't
use or rework on this patch for any purpose.

Thanks!