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!