openvswitch: add tunnel protocol to sw_flow_key

Store tunnel protocol (AF_INET or AF_INET6) in sw_flow_key. This field now
also acts as an indicator whether the flow contains tunnel data (this was
previously indicated by tun_key.u.ipv4.dst being set but with IPv6 addresses
in an union with IPv4 ones this won't work anymore).

The new field was added to a hole in sw_flow_key.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index f2ea83b..95dbced 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -427,7 +427,7 @@
 
 static int flow_key_start(const struct sw_flow_key *key)
 {
-	if (key->tun_key.u.ipv4.dst)
+	if (key->tun_proto)
 		return 0;
 	else
 		return rounddown(offsetof(struct sw_flow_key, phy),