Re: [PATCH net 0/5] net: stmmac: Fix double VLAN 802.1ad tag handling

[Andrew Lunn]

On Wed, Jul 29, 2026 at 09:51:04AM +0000, Ovidiu Panait wrote:
> Currently, hardware VLAN stripping is broken for 802.1ad tags. vlan_rx_hw()
> hardcodes ETH_P_8021Q when putting the hardware tag into the skb, rather
> than using the actual protocol from the packet. Because of this, packets
> that contain an 802.1ad outer tag are incorrectly passed up the stack as
> having an 802.1Q tag.
> 
> This issue was observed on the Renesas RZ/V2H platform (which has a dwmac4
> IP), when testing QinQ ping:
> 
>   # DUT
>   ip link add link end0 name end0.100 type vlan proto 802.1ad id 100
>   ip link add link end0.100 name end0.100.200 type vlan proto 802.1q id 200
>   ip addr add 172.16.3.2/24 dev end0.100.200
>   ip link set end0 up
>   ip link set end0.100 up
>   ip link set end0.100.200 up
> 
>   # Peer
>   ip link add link eth0 name eth0.100 type vlan proto 802.1ad id 100
>   ip link add link eth0.100 name eth0.100.200 type vlan proto 802.1q id 200
>   ip addr add 172.16.3.1/24 dev eth0.100.200
>   ip link set eth0 up
>   ip link set eth0.100 up
>   ip link set eth0.100.200 up
>   ping 172.16.3.2
>     -- FAIL --

I stretch goal, if you are interested and have time. Can you turn this
into a test somewhere in tools/testing/selftests/net ? If one MAC
driver has it wrong, there are probably other MAC drivers which are
also wrong.

	Andrew