[PATCH net 2/5] net: dsa: mt7530: preserve VLAN tags on trapped link-local frames

[Chester A. Unal]

Hey Daniel.

On 05/05/2026 15:16, Daniel Golle wrote:
> The BPC, RGAC1 and RGAC2 registers control the handling of link-local
> frames with reserved MAC DAs (01:80:C2:00:00:0x). These frames are
> correctly trapped to the CPU port, but the egress VLAN tag attribute was
> set to MT7530_VLAN_EG_UNTAGGED which causes the switch to strip any
> VLAN tags from trapped frames before they reach the CPU.
> 
> This causes VLAN-tagged link-local frames (STP BPDUs, LLDP, PTP Peer
> Delay Requests) to arrive at the CPU without their VLAN tag, so they
> are delivered to the base network interface instead of the VLAN
> sub-interface. The DSA local_termination selftest confirms this: all
> link-local protocol tests on VLAN upper interfaces fail.
> 
> Set the EG_TAG attribute to MT7530_VLAN_EG_DISABLED (system default)
> so that the switch does not modify VLAN tags in trapped frames. This
> way VLAN-tagged frames retain their original tag and are delivered to
> the correct VLAN sub-interface, matching the behavior of non-trapped
> frames which pass through without VLAN tag modification.
> 
> Fixes: 69ddba9d170b ("net: dsa: mt7530: fix handling of all link-local frames")
> Signed-off-by: Daniel Golle <daniel at makrotopia.org>

Thank you for this patch. Could you please confirm that it conforms to the
findings documented on this patch log?

https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=e8bf353577f382c7066c661fed41b2adc0fc7c40

Cheers.
Chester A.