kernel: mtk_eth_soc: fix tx vlan tag for llc packets

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: https://github.com/openwrt/openwrt/issues/19916
Reported-by: Thibaut VARENE <hacks@slashdirt.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

4 files changed, 82 insertions, 4 deletions

diff --git a/target/linux/generic/hack-6.12/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch b/target/linux/generic/hack-6.12/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch
index c4bf08b594..ffc21ee2ff 100644
--- a/target/linux/generic/hack-6.12/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch
+++ b/target/linux/generic/hack-6.12/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch
@@ -37,7 +37,7 @@ Signed-off-by: Bo-Cun Chen <bc-bocun.chen@mediatek.com>
  		.glo_cfg	= 0x4604,
  		.rst_idx	= 0x4608,
  		.delay_irq	= 0x460c,
-@@ -3901,6 +3904,56 @@ static void mtk_set_mcr_max_rx(struct mt
+@@ -3909,6 +3912,56 @@ static void mtk_set_mcr_max_rx(struct mt
  		mtk_w32(mac->hw, mcr_new, MTK_MAC_MCR(mac->id));
  }
  
@@ -94,7 +94,7 @@ Signed-off-by: Bo-Cun Chen <bc-bocun.chen@mediatek.com>
  static void mtk_hw_reset(struct mtk_eth *eth)
  {
  	u32 val;
-@@ -4380,6 +4433,8 @@ static void mtk_pending_work(struct work
+@@ -4388,6 +4441,8 @@ static void mtk_pending_work(struct work
  	rtnl_lock();
  	set_bit(MTK_RESETTING, &eth->state);
  
diff --git a/target/linux/generic/hack-6.6/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch b/target/linux/generic/hack-6.6/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch
index 95a6aa8cb8..25d824bce6 100644
--- a/target/linux/generic/hack-6.6/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch
+++ b/target/linux/generic/hack-6.6/730-net-ethernet-mtk_eth_soc-add-hw-dump-for-forced-rese.patch
@@ -37,7 +37,7 @@ Signed-off-by: Bo-Cun Chen <bc-bocun.chen@mediatek.com>
  		.glo_cfg	= 0x4604,
  		.rst_idx	= 0x4608,
  		.delay_irq	= 0x460c,
-@@ -3899,6 +3902,56 @@ static void mtk_set_mcr_max_rx(struct mt
+@@ -3907,6 +3910,56 @@ static void mtk_set_mcr_max_rx(struct mt
  		mtk_w32(mac->hw, mcr_new, MTK_MAC_MCR(mac->id));
  }
  
@@ -94,7 +94,7 @@ Signed-off-by: Bo-Cun Chen <bc-bocun.chen@mediatek.com>
  static void mtk_hw_reset(struct mtk_eth *eth)
  {
  	u32 val;
-@@ -4374,6 +4427,8 @@ static void mtk_pending_work(struct work
+@@ -4382,6 +4435,8 @@ static void mtk_pending_work(struct work
  	rtnl_lock();
  	set_bit(MTK_RESETTING, &eth->state);
  
diff --git a/target/linux/generic/pending-6.12/742-net-ethernet-mtk_eth_soc-fix-tx-vlan-tag-for-llc-pac.patch b/target/linux/generic/pending-6.12/742-net-ethernet-mtk_eth_soc-fix-tx-vlan-tag-for-llc-pac.patch
new file mode 100644
index 0000000000..20a6a29449
--- /dev/null
+++ b/target/linux/generic/pending-6.12/742-net-ethernet-mtk_eth_soc-fix-tx-vlan-tag-for-llc-pac.patch
@@ -0,0 +1,39 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 31 Aug 2025 20:05:13 +0200
+Subject: [PATCH] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets
+
+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>
+---
+
+--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
++++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+@@ -1778,6 +1778,13 @@ static netdev_tx_t mtk_start_xmit(struct
+ 	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
+@@ -1841,8 +1848,9 @@ static netdev_tx_t mtk_start_xmit(struct
+ 
+ drop:
+ 	spin_unlock(&eth->page_lock);
+-	stats->tx_dropped++;
+ 	dev_kfree_skb_any(skb);
++dropped:
++	stats->tx_dropped++;
+ 	return NETDEV_TX_OK;
+ }
+ 
diff --git a/target/linux/generic/pending-6.6/742-net-ethernet-mtk_eth_soc-fix-tx-vlan-tag-for-llc-pac.patch b/target/linux/generic/pending-6.6/742-net-ethernet-mtk_eth_soc-fix-tx-vlan-tag-for-llc-pac.patch
new file mode 100644
index 0000000000..7e90a79e5b
--- /dev/null
+++ b/target/linux/generic/pending-6.6/742-net-ethernet-mtk_eth_soc-fix-tx-vlan-tag-for-llc-pac.patch
@@ -0,0 +1,39 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Sun, 31 Aug 2025 20:05:13 +0200
+Subject: [PATCH] net: ethernet: mtk_eth_soc: fix tx vlan tag for llc packets
+
+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>
+---
+
+--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
++++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+@@ -1773,6 +1773,13 @@ static netdev_tx_t mtk_start_xmit(struct
+ 	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
+@@ -1836,8 +1843,9 @@ static netdev_tx_t mtk_start_xmit(struct
+ 
+ drop:
+ 	spin_unlock(&eth->page_lock);
+-	stats->tx_dropped++;
+ 	dev_kfree_skb_any(skb);
++dropped:
++	stats->tx_dropped++;
+ 	return NETDEV_TX_OK;
+ }
+