net: dsa: lan9303: handle hwaccel VLAN tags

Check for a hwaccel VLAN tag on rx and use it if present.  Otherwise,
use __skb_vlan_pop() like the other tag parsers do.  This fixes the case
where the VLAN tag has already been consumed by the master.

Fixes: a129259 ("net: dsa: add new DSA switch driver for the SMSC-LAN9303")
Signed-off-by: Mans Rullgard <mans@mansr.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20220216124634.23123-1-mans@mansr.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: mansr

net/dsa/tag_lan9303.c

@@ -77,7 +77,6 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
 
 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
 {
-	__be16 *lan9303_tag;
 	u16 lan9303_tag1;
 	unsigned int source_port;
 
@@ -87,14 +86,15 @@ static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
 		return NULL;
 	}
 
-	lan9303_tag = dsa_etype_header_pos_rx(skb);
-
-	if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
-		dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
-		return NULL;
+	if (skb_vlan_tag_present(skb)) {
+		lan9303_tag1 = skb_vlan_tag_get(skb);
+		__vlan_hwaccel_clear_tag(skb);
+	} else {
+		skb_push_rcsum(skb, ETH_HLEN);
+		__skb_vlan_pop(skb, &lan9303_tag1);
+		skb_pull_rcsum(skb, ETH_HLEN);
 	}
 
-	lan9303_tag1 = ntohs(lan9303_tag[1]);
 	source_port = lan9303_tag1 & 0x3;
 
 	skb->dev = dsa_master_find_slave(dev, 0, source_port);
@@ -103,13 +103,6 @@ static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
 		return NULL;
 	}
 
-	/* remove the special VLAN tag between the MAC addresses
-	 * and the current ethertype field.
-	 */
-	skb_pull_rcsum(skb, 2 + 2);
-
-	dsa_strip_etype_header(skb, LAN9303_TAG_LEN);
-
 	if (!(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU))
 		dsa_default_offload_fwd_mark(skb);