openvswitch: Fix GSO with multiple MPLS label.

MPLS GSO needs to know inner most protocol to process GSO packets.

Fixes: 25cd9ba0abc ("openvswitch: Add basic MPLS support to
kernel").

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/actions.c

@@ -147,7 +147,8 @@ static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 	hdr = eth_hdr(skb);
 	hdr->h_proto = mpls->mpls_ethertype;
 
-	skb_set_inner_protocol(skb, skb->protocol);
+	if (!skb->inner_protocol)
+		skb_set_inner_protocol(skb, skb->protocol);
 	skb->protocol = mpls->mpls_ethertype;
 
 	invalidate_flow_key(key);