From: Felix Fietkau <nbd@nbd.name>
Date: Tue, 27 Dec 2022 15:02:51 +0100
Subject: [PATCH] net: ethernet: mtk_eth_soc: ppe: fix L2 offloading with DSA
 untagging offload enabled

Check for skb metadata in order to detect the case where the DSA header is not
present.

Fixes: 2d7605a72906 ("net: ethernet: mtk_eth_soc: enable hardware DSA untagging")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---

--- a/drivers/net/ethernet/mediatek/mtk_ppe.c
+++ b/drivers/net/ethernet/mediatek/mtk_ppe.c
@@ -8,6 +8,7 @@
 #include <linux/platform_device.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
+#include <net/dst_metadata.h>
 #include <net/dsa.h>
 #include "mtk_eth_soc.h"
 #include "mtk_ppe.h"
@@ -781,7 +782,9 @@ void __mtk_ppe_check_skb(struct mtk_ppe
 		    skb->dev->dsa_ptr->tag_ops->proto != DSA_TAG_PROTO_MTK)
 			goto out;
 
-		tag += 4;
+		if (!skb_metadata_dst(skb))
+			tag += 4;
+
 		if (get_unaligned_be16(tag) != ETH_P_8021Q)
 			break;
 
