ip6_tunnel: allow to inherit from VLAN encapsulated IP

The current code allows to inherit the TTL (hop_limit) from the
payload when skb->protocol is ETH_P_IP or ETH_P_IPV6.
However when the payload is VLAN encapsulated (e.g because the tunnel
is of type GRETAP), then this inheriting does not work, because the
visible skb->protocol is of type ETH_P_8021Q or ETH_P_8021AD.

Instead of skb->protocol, use skb_protocol().
Signed-off-by: Matthias May <matthias.may@westermo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -1080,10 +1080,13 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 	unsigned int eth_hlen = t->dev->type == ARPHRD_ETHER ? ETH_HLEN : 0;
 	unsigned int psh_hlen = sizeof(struct ipv6hdr) + t->encap_hlen;
 	unsigned int max_headroom = psh_hlen;
+	__be16 payload_protocol;
 	bool use_cache = false;
 	u8 hop_limit;
 	int err = -1;
 
+	payload_protocol = skb_protocol(skb, true);
+
 	if (t->parms.collect_md) {
 		hop_limit = skb_tunnel_info(skb)->key.ttl;
 		goto route_lookup;
@@ -1093,7 +1096,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 
 	/* NBMA tunnel */
 	if (ipv6_addr_any(&t->parms.raddr)) {
-		if (skb->protocol == htons(ETH_P_IPV6)) {
+		if (payload_protocol == htons(ETH_P_IPV6)) {
 			struct in6_addr *addr6;
 			struct neighbour *neigh;
 			int addr_type;
@@ -1114,7 +1117,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 
 			memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
 			neigh_release(neigh);
-		} else if (skb->protocol == htons(ETH_P_IP)) {
+		} else if (payload_protocol == htons(ETH_P_IP)) {
 			const struct rtable *rt = skb_rtable(skb);
 
 			if (!rt)
@@ -1225,9 +1228,9 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 	skb_dst_set(skb, dst);
 
 	if (hop_limit == 0) {
-		if (skb->protocol == htons(ETH_P_IP))
+		if (payload_protocol == htons(ETH_P_IP))
 			hop_limit = ip_hdr(skb)->ttl;
-		else if (skb->protocol == htons(ETH_P_IPV6))
+		else if (payload_protocol == htons(ETH_P_IPV6))
 			hop_limit = ipv6_hdr(skb)->hop_limit;
 		else
 			hop_limit = ip6_dst_hoplimit(dst);