net: tap: check vlan with eth_type_vlan() method

Replace some checks for ETH_P_8021Q and ETH_P_8021AD in
drivers/net/tap.c with eth_type_vlan.
Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Link: https://lore.kernel.org/r/20210115023238.4681-1-dong.menglong@zte.com.cnSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/tap.c

@@ -713,8 +713,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 	skb_probe_transport_header(skb);
 
 	/* Move network header to the right position for VLAN tagged packets */
-	if ((skb->protocol == htons(ETH_P_8021Q) ||
-	     skb->protocol == htons(ETH_P_8021AD)) &&
+	if (eth_type_vlan(skb->protocol) &&
 	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
 		skb_set_network_header(skb, depth);
 
@@ -1164,8 +1163,7 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
 	}
 
 	/* Move network header to the right position for VLAN tagged packets */
-	if ((skb->protocol == htons(ETH_P_8021Q) ||
-	     skb->protocol == htons(ETH_P_8021AD)) &&
+	if (eth_type_vlan(skb->protocol) &&
 	    __vlan_get_protocol(skb, skb->protocol, &depth) != 0)
 		skb_set_network_header(skb, depth);