[PATCH net 4/5] net: stmmac: Disable double VLAN stripping on dwmac4

[Ovidiu Panait]

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 a 802.1ad outer tag are incorrectly passed up the stack as
having an 802.1Q tag. This causes QinQ ping between two hosts to fail.

vlan_rx_hw() is shared by dwxgmac2 and dwmac4: on dwxgmac2 the tag type
is available in the RDES3 write-back descriptor (the ET_LT field), so the
outer tag type can be determined based on that info. However, dwmac4
doesn't seem to provide the tag type. The Length/Type field in RDES3 only
indicates whether the packet is single or double-tagged, not which tag
type was stripped.

Since dwmac4 cannot report the stripped tag type, it cannot support
hardware double VLAN stripping correctly. Disable it by dropping
update_dvlan_state from dwmac_vlan_ops. With this, 802.1ad tags are
left in place and handled by the software VLAN path.

Fixes: 750011e239a5 ("net: stmmac: Add support for HW-accelerated VLAN stripping")
Signed-off-by: Ovidiu Panait <ovidiu.panait.rb@xxxxxxxxxxx>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c
index 1e47ae62093e..9b5b3f11f699 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c
@@ -273,7 +273,6 @@ static void dwxgmac2_update_vlan_hash(struct mac_device_info *hw, u32 hash)
 
 const struct stmmac_vlan_ops dwmac_vlan_ops = {
 	.update_vlan_hash = vlan_update_hash,
-	.update_dvlan_state = vlan_update_dvlan_state,
 	.enable_vlan = vlan_enable,
 	.add_hw_vlan_rx_fltr = vlan_add_hw_rx_fltr,
 	.del_hw_vlan_rx_fltr = vlan_del_hw_rx_fltr,
-- 
2.34.1