PROBLEM: net: qede: QL41262 unable to TX packets with multiple VLAN tags

[Joseph Bywater <joseph@intrigued.uk>]

Hi,

I have been having a problem with a QLogic QL41262 NIC (using the qede driver)
that is unable to TX packets with more than one VLAN tag. RX works fine,
even with more than 2 VLAN tags applied. 

I set up a test with two servers, one with an Intel NIC (ixgbe, .101), 
and the other with the QL41262 (qede, .102). I created interfaces on each server as follows:

ip link add link eth0 eth0.10 type vlan id 10
ip link add link eth0.10 eth0.10.20 type vlan id 20
ip addr add 10.50.10.<101-102>/24 dev eth0.10
ip addr add 10.50.20.<101-102>/24 dev eth0.10.20
ip link set up eth0
ip link set up eth0.10
ip link set up eth0.10.20

I then attempted to ping from the Intel server to the QLogic:

ping 10.50.10.102 (single VLAN tag) -> works
ping 10.50.20.102 (double VLAN tag) -> does not work

In the failing case, with two VLANs, I can see the generated ARP response
using tcpdump from eth0.10.20 down to the eth0 interface.
However, I do not receive this ARP packet on the server with the Intel NIC, 
and the packet counters on the switch do not increase.

Here is a truncated output from ethtool:
rx-vlan-offload: on [fixed]
tx-vlan-offload: on [fixed]
rx-vlan-filter: on [fixed]
vlan-challenged: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]

I have tested this on 6.8.0-79-generic, Ubuntu 24.04.
Additionally, I tested a similar setup with other NICs, which worked without issue (drivers listed):
- mlx5_core
- ixgbe
- ice

Is this a known limitation of QLogic NICs? If not, are you able to
advise on further tests I may be able to perform?

Thanks,
Joe