[PATCH net] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets

[PATCH net] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets

[Felix Fietkau]

When sending llc packets with vlan tx offload, the hardware fails to
actually add the tag. Deal with this by fixing it up in software.

Fixes: 656e705243fd ("net-next: mediatek: add support for MT7623 ethernet")
Reported-by: Thibaut VARENE <hacks@slashdirt.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 5a5fcde76dc0..e68997a29191 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -1761,6 +1761,13 @@ static netdev_tx_t mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	bool gso = false;
 	int tx_num;
 
+	if (skb_vlan_tag_present(skb) &&
+	    !eth_proto_is_802_3(eth_hdr(skb)->h_proto)) {
+		skb = __vlan_hwaccel_push_inside(skb);
+		if (!skb)
+			goto dropped;
+	}
+
 	/* normally we can rely on the stack not calling this more than once,
 	 * however we have 2 queues running on the same ring so we need to lock
 	 * the ring access
@@ -1806,8 +1813,9 @@ static netdev_tx_t mtk_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 drop:
 	spin_unlock(&eth->page_lock);
-	stats->tx_dropped++;
 	dev_kfree_skb_any(skb);
+dropped:
+	stats->tx_dropped++;
 	return NETDEV_TX_OK;
 }
 
-- 
2.51.0

Re: [PATCH net] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets

[Simon Horman]

On Sun, Aug 31, 2025 at 08:20:07PM +0200, Felix Fietkau wrote:
> When sending llc packets with vlan tx offload, the hardware fails to
> actually add the tag. Deal with this by fixing it up in software.
> 
> Fixes: 656e705243fd ("net-next: mediatek: add support for MT7623 ethernet")
> Reported-by: Thibaut VARENE <hacks@slashdirt.org>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Sun, 31 Aug 2025 20:20:07 +0200 you wrote:
> When sending llc packets with vlan tx offload, the hardware fails to
> actually add the tag. Deal with this by fixing it up in software.
> 
> Fixes: 656e705243fd ("net-next: mediatek: add support for MT7623 ethernet")
> Reported-by: Thibaut VARENE <hacks@slashdirt.org>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>
> 
> [...]

Here is the summary with links:
  - [net] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets
    https://git.kernel.org/netdev/net/c/d4736737110f

You are awesome, thank you!
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