xfrm: Check for the new replay implementation if an esn state is inserted

IPsec extended sequence numbers can be used only with the new
anti-replay window implementation. So check if the new implementation
is used if an esn state is inserted and return an error if it is not.
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>

net/xfrm/xfrm_user.c

@@ -124,6 +124,9 @@ static inline int verify_replay(struct xfrm_usersa_info *p,
 {
 	struct nlattr *rt = attrs[XFRMA_REPLAY_ESN_VAL];
 
+	if ((p->flags & XFRM_STATE_ESN) && !rt)
+		return -EINVAL;
+
 	if (!rt)
 		return 0;