netdev - Re: [PATCH net v2 1/1] net: stmmac: Prevent DSA tags from breaking COE on stmmac

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Date: Wed, 3 Jan 2024 23:25:29 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Romain Gantois <romain.gantois@...tlin.com>, 
	Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu <joabreu@...opsys.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Maxime Coquelin <mcoquelin.stm32@...il.com>, Miquel Raynal <miquel.raynal@...tlin.com>, 
	Maxime Chevallier <maxime.chevallier@...tlin.com>, Sylvain Girard <sylvain.girard@...com>, 
	Andrew Lunn <andrew@...n.ch>, Pascal EBERHARD <pascal.eberhard@...com>, 
	Richard Tresidder <rtresidd@...ctromag.com.au>, netdev@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH net v2 1/1] net: stmmac: Prevent DSA tags from breaking
 COE on stmmac

On Wed, Jan 3, 2024 at 9:10 PM Vladimir Oltean <olteanv@...il.com> wrote:
> On Tue, Jan 02, 2024 at 05:27:15PM +0100, Romain Gantois wrote:
> > +/* Check if ethertype will trigger IP
> > + * header checks/COE in hardware
> > + */
> > +static inline bool stmmac_has_ip_ethertype(struct sk_buff *skb)
> > +{
> > +     __be16 proto = eth_header_parse_protocol(skb);
> > +
> > +     return (proto == htons(ETH_P_IP)) || (proto == htons(ETH_P_IPV6)) ||
> > +             (proto == htons(ETH_P_8021Q));
>
> proto == htons(ETH_P_8021Q) means that the skb has an IP EtherType?
> What if an IP header does not follow after the VLAN header?

It's probably best to do like I do here:
https://lore.kernel.org/netdev/20240102-new-gemini-ethernet-regression-v5-2-cf61ab3aa8cd@linaro.org/

+ if (ethertype == ETH_P_8021Q)
+   ethertype = ntohs(__vlan_get_protocol(skb, htons(ethertype), NULL));

Yours,
Linus Walleij