[PATCH net 5/5] net: dsa: mt7530: untag VLAN-aware bridge PVID

[Daniel Golle <daniel@makrotopia.org>]

From: Edward Parker <edward@topnotchit.com>

With bridge VLAN filtering enabled on a port configured as untagged
member of the bridge PVID, ingress untagged frames do not reach the
corresponding bridge VLAN upper interface (br-lan.<vid>). ARP and
similar traffic is visible on the physical port but not delivered
to the VLAN sub-interface.

The MT7530/MT7531 forwards frames to the CPU port with the user
port's PVID tag applied even when the frame ingressed untagged on
the wire, because the CPU port is set to MT7530_VLAN_EG_CONSISTENT
and is a tagged member of the VLAN entry created for the bridge
VLAN. The DSA core then sees a hwaccel-tagged frame whose VID
matches the port's PVID, which the bridge does not treat as the
untagged-on-the-wire frame that the user expects.

Set ds->untag_vlan_aware_bridge_pvid in the mt7530 and mt7531
setup paths so the DSA core strips that hwaccel tag in software
when the parsed VID matches the bridge port's PVID, restoring the
on-the-wire frame as the bridge expects to see it.

Link: https://github.com/openwrt/openwrt/issues/18576
Fixes: 83163f7dca56 ("net: dsa: mediatek: add VLAN support for MT7530")
Signed-off-by: Edward Parker <edward@topnotchit.com>
[daniel@makrotopia.org: improve commit message]
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 drivers/net/dsa/mt7530.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 2e5337186800..4b7e5398b211 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -2452,6 +2452,7 @@ mt7530_setup(struct dsa_switch *ds)
 	}
 
 	ds->assisted_learning_on_cpu_port = true;
+	ds->untag_vlan_aware_bridge_pvid = true;
 	ds->mtu_enforcement_ingress = true;
 
 	if (priv->id == ID_MT7530) {
@@ -2641,6 +2642,7 @@ mt7531_setup_common(struct dsa_switch *ds)
 	int ret, i;
 
 	ds->assisted_learning_on_cpu_port = true;
+	ds->untag_vlan_aware_bridge_pvid = true;
 	ds->mtu_enforcement_ingress = true;
 
 	mt753x_trap_frames(priv);
-- 
2.54.0