netdev - Re: [PATCH net v5] net: stmmac: Prevent DSA tags from breaking COE

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Message-ID: <20240116103637.794811a6@kernel.org>
Date: Tue, 16 Jan 2024 10:36:37 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Romain Gantois <romain.gantois@...tlin.com>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
 <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, 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>,
 Pascal EBERHARD <pascal.eberhard@...com>, Richard Tresidder
 <rtresidd@...ctromag.com.au>, Linus Walleij <linus.walleij@...aro.org>,
 Vladimir Oltean <olteanv@...il.com>, Andrew Lunn <andrew@...n.ch>, Thomas
 Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org, Vladimir
 Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH net v5] net: stmmac: Prevent DSA tags from breaking COE

On Tue, 16 Jan 2024 17:18:30 +0100 (CET) Romain Gantois wrote:
> > which makes it sound like bit 5 will not be set for a Ethernet II frame
> > with unsupported IP payload, or not an IP frame. Does the bit mean other
> > things in different descriptor formats?  
> 
> The description of this bit in my datasheet is:
> 
> ```
> b5 FT Frame Type
> When set, this bit indicates that the Receive Frame is an Ethernet-type frame 
> (the Length/Type field is greater than or equal to 1,536). When this bit is 
> reset, it indicates that the received frame is an IEEE 802.3 frame. This bit is 
> not valid for Runt frames less than 14 bytes
> ```
> 
> There is no mention of a more subtle check to detect non-IP Ethernet II frames. 
> I ran some tests on my hardware and EDSA-tagged packets consistently come in 
> with status 0b100, so the MAC sets the frame type bit even for frames that don't 
> have an IP ethertype.

Boo, who designed this thing :(

v6 is good to go in then, thank you for investigating and testing!