openvswitch: Fix ovs_flow_key_update()

ovs_flow_key_update() is called when the flow key is invalid, and it is
used to update and revalidate the flow key. Commit 329f45bc
("openvswitch: add mac_proto field to the flow key") introduces mac_proto
field to flow key and use it to determine whether the flow key is valid.
However, the commit does not update the code path in ovs_flow_key_update()
to revalidate the flow key which may cause BUG_ON() on execute_recirc().
This patch addresses the aforementioned issue.

Fixes: 329f45bc ("openvswitch: add mac_proto field to the flow key")
Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
Acked-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/flow.c

@@ -527,7 +527,7 @@ static int key_extract(struct sk_buff *skb, struct sw_flow_key *key)
 
 	/* Link layer. */
 	clear_vlan(key);
-	if (key->mac_proto == MAC_PROTO_NONE) {
+	if (ovs_key_mac_proto(key) == MAC_PROTO_NONE) {
 		if (unlikely(eth_type_vlan(skb->protocol)))
 			return -EINVAL;
 
@@ -745,7 +745,13 @@ static int key_extract(struct sk_buff *skb, struct sw_flow_key *key)
 
 int ovs_flow_key_update(struct sk_buff *skb, struct sw_flow_key *key)
 {
-	return key_extract(skb, key);
+	int res;
+
+	res = key_extract(skb, key);
+	if (!res)
+		key->mac_proto &= ~SW_FLOW_KEY_INVALID;
+
+	return res;
 }
 
 static int key_extract_mac_proto(struct sk_buff *skb)