netdev - Re: [PATCH net 3/3] net: bcmgenet: use hardware padding of runt frames

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Message-ID: <5fdf1da6-8c69-1434-e5ee-0c90568f6aba@gmail.com>
Date:   Wed, 24 Jun 2020 18:48:36 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Doug Berger <opendmb@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 3/3] net: bcmgenet: use hardware padding of runt
 frames



On 6/24/2020 6:14 PM, Doug Berger wrote:
> When commit 474ea9cafc45 ("net: bcmgenet: correctly pad short
> packets") added the call to skb_padto() it should have been
> located before the nr_frags parameter was read since that value
> could be changed when padding packets with lengths between 55
> and 59 bytes (inclusive).
> 
> The use of a stale nr_frags value can cause corruption of the
> pad data when tx-scatter-gather is enabled. This corruption of
> the pad can cause invalid checksum computation when hardware
> offload of tx-checksum is also enabled.
> 
> Since the original reason for the padding was corrected by
> commit 7dd399130efb ("net: bcmgenet: fix skb_len in
> bcmgenet_xmit_single()") we can remove the software padding all
> together and make use of hardware padding of short frames as
> long as the hardware also always appends the FCS value to the
> frame.
> 
> Fixes: 474ea9cafc45 ("net: bcmgenet: correctly pad short packets")
> Signed-off-by: Doug Berger <opendmb@...il.com>

Acked-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian