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

["Nazle Asmade, Muhammad Nazim Amirul" <muhammad.nazim.amirul.nazle.asmade@altera.com>]

On 29/7/2026 7:35 pm, Maxime Chevallier wrote:
> + Nazim Amirul
> 
> On 7/29/26 11:51, 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 --
>>
>> This series addresses the issue for both dwmac4 and dwxgmac2:
>> - dwmac4: since dwmac4 does not expose the tag type in the RDES3
>>    descriptor, it cannot support hardware double VLAN stripping correctly.
>>    This series disables double VLAN stripping for it, so the 802.1ad tags
>>    are left in place and are handled by the software VLAN path.
>>
>> - dwxgmac2: the RDES3 descriptor does report the type, so the code was
>>    updated to read it instead of hardcoding ETH_P_8021Q.
>>
>> Note: patch 5/5 was compile tested only, as I do not have the hardware.
>> However, it uses the same codepath as dwmac4, so it has the same issue.
> Nazim Amirul, as you seem to have access to some AgileX5 with XGMAC, can you
> see if you can reproduce the issue on your side and if this series solves it ?

Hi Maxime,

Tested on my end and seeing the same failure as above without this 
series, is this patch 5 is the only patch needed to fix the problem?>
> Thanks :)
> 
> Maxime