linux-kernel - Re: [PATCH 2/2] net: dsa: tag_ksz: dont let the hardware process the layer 4 checksum

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Message-ID: <20210715131251.zhtcsjkat267yrtl@skbuf>
Date:   Thu, 15 Jul 2021 16:12:51 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     Andrew Lunn <andrew@...n.ch>, woojung.huh@...rochip.com,
        UNGLinuxDriver@...rochip.com, vivien.didelot@...il.com,
        f.fainelli@...il.com, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: dsa: tag_ksz: dont let the hardware process the
 layer 4 checksum

On Thu, Jul 15, 2021 at 03:04:31PM +0200, Lino Sanfilippo wrote:
> Please note that skb_put() asserts that the SKB is linearized. So I think we
> should rather clear both NETIF_F_FRAGLIST and NETIF_F_SG unconditionally since also
> header taggers use some form of skb_put() dont they?

The tail taggers use skb_put() as part of the routine to make room for
the tail tag.

Some of the header taggers use __skb_put_padto() when the packets are
too small (under ETH_ZLEN). When they are so small they are definitely
linear already.

We don't have a third form/use of skb_put().