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

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Message-Id: <20181203.151724.648093455366632499.davem@davemloft.net>
Date:   Mon, 03 Dec 2018 15:17:24 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org, saeedm@...lanox.com, edumazet@...gle.com
Subject: Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame
 padding

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?