xfrm: Restrict extended sequence numbers to esp

The IPsec extended sequence numbers are fully implemented just for
esp. So restrict the usage to esp until other protocols have
support too.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index ccc4c0c..3d15d3e 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -127,6 +127,9 @@
 	if (!rt)
 		return 0;
 
+	if (p->id.proto != IPPROTO_ESP)
+		return -EINVAL;
+
 	if (p->replay_window != 0)
 		return -EINVAL;