[PATCH v4] net: stmmac: Prevent DSA tags from breaking COE

[Linus Walleij]

On Tue, Jan 9, 2024 at 3:42 PM Romain Gantois
<romain.gantois at bootlin.com> wrote:

> Some DSA tagging protocols change the EtherType field in the MAC header
> e.g.  DSA_TAG_PROTO_(DSA/EDSA/BRCM/MTK/RTL4C_A/SJA1105). On TX these tagged
> frames are ignored by the checksum offload engine and IP header checker of
> some stmmac cores.
>
> On RX, the stmmac driver wrongly assumes that checksums have been computed
> for these tagged packets, and sets CHECKSUM_UNNECESSARY.
>
> Add an additional check in the stmmac TX and RX hotpaths so that COE is
> deactivated for packets with ethertypes that will not trigger the COE and
> IP header checks.
>
> Fixes: 6b2c6e4a938f ("net: stmmac: propagate feature flags to vlan")
> Cc:  <stable at vger.kernel.org>
> Reported-by: Richard Tresidder <rtresidd at electromag.com.au>
> Link: https://lore.kernel.org/netdev/e5c6c75f-2dfa-4e50-a1fb-6bf4cdb617c2@electromag.com.au/
> Reported-by: Romain Gantois <romain.gantois at bootlin.com>
> Link: https://lore.kernel.org/netdev/c57283ed-6b9b-b0e6-ee12-5655c1c54495@bootlin.com/
> Reviewed-by: Vladimir Oltean <vladimir.oltean at nxp.com>
> Signed-off-by: Romain Gantois <romain.gantois at bootlin.com>

Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij