Re: [PATCH v5 net-next 12/14] bridge: No DEV_PATH_BR_VLAN_UNTAG_HW for dsa foreign

Vladimir Oltean
2025-02-07T15:06:08Z

On Tue, Feb 04, 2025 at 08:49:19PM +0100, Eric Woudstra wrote:
> In network setup as below:
>
> fastpath bypass
> .----------------------------------------.
> / \
> | IP - forwarding |
> | / \ v
> | / wan ...
> | /
> | |
> | |
> | brlan.1
> | |
> | +-------------------------------+
> | | vlan 1 |
> | | |
> | | brlan (vlan-filtering) |
> | | +---------------+
> | | | DSA-SWITCH |
> | | vlan 1 | |
> | | to | |
> | | untagged 1 vlan 1 |
> | +---------------+---------------+
> . / \
> ----->wlan1 lan0
> . .
> . ^
> ^ vlan 1 tagged packets
> untagged packets
>
> br_vlan_fill_forward_path_mode() sets DEV_PATH_BR_VLAN_UNTAG_HW when
> filling in from brlan.1 towards wlan1. But it should be set to
> DEV_PATH_BR_VLAN_UNTAG in this case. Using BR_VLFLAG_ADDED_BY_SWITCHDEV
> is not correct. The dsa switchdev adds it as a foreign port.
>
> The same problem for all foreignly added dsa vlans on the bridge.
>
> First add the vlan, trying only native devices.
> If this fails, we know this may be a vlan from a foreign device.
>
> Use BR_VLFLAG_TAGGING_BY_SWITCHDEV to make sure DEV_PATH_BR_VLAN_UNTAG_HW
> is set only when there if no foreign device involved.
>
> Signed-off-by: Eric Woudstra <ericwouds@gmail.com>
> ---

Shouldn't mlxsw_sp_switchdev_vxlan_vlans_add() also respect the
SWITCHDEV_F_NO_FOREIGN flag? My (maybe incorrect) understanding of
bridging topologies with vxlan and mlxsw is that they are neighbor
bridge ports, and mlxsw doesn't (seem to) call
switchdev_bridge_port_offload() for the vxlan bridge port. This
technically makes vxlan a foreign bridge port to mlxsw, so it should
skip reacting on VLAN switchdev objects when that flag is set, just
for uniform behavior across the board.

(your patch repeats the notifier without the SWITCHDEV_F_NO_FOREIGN
flag anyway, so it only matters for flowtable offload).