xfrm: Move the test on replay window size into the replay check functions

As it is, the replay check is just performed if the replay window of the
legacy implementation is nonzero. So we move the test on a nonzero replay
window inside the replay check functions to be sure we are testing for the
right implementation.

Signed-off-by: Steffen Klassert <[e-mail]>
Acked-by: Herbert Xu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/xfrm/xfrm_input.c

···
 			goto drop_unlock;
 		}
 
-		if (x->props.replay_window && x->repl->check(x, skb, seq)) {
+		if (x->repl->check(x, skb, seq)) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATESEQERROR);
 			goto drop_unlock;
 		}

net/xfrm/xfrm_replay.c

···
 	u32 diff;
 	u32 seq = ntohl(net_seq);
 
+	if (!x->props.replay_window)
+		return 0;
+
 	if (unlikely(seq == 0))
 		goto err;
 
···
 {
 	unsigned int bitnr, nr;
 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
+	u32 pos;
 	u32 seq = ntohl(net_seq);
 	u32 diff =  replay_esn->seq - seq;
-	u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
+
+	if (!replay_esn->replay_window)
+		return 0;
+
+	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
 
 	if (unlikely(seq == 0))
 		goto err;
···
 	unsigned int bitnr, nr;
 	u32 diff;
 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
+	u32 pos;
 	u32 seq = ntohl(net_seq);
-	u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
 	u32 wsize = replay_esn->replay_window;
 	u32 top = replay_esn->seq;
 	u32 bottom = top - wsize + 1;
+
+	if (!wsize)
+		return 0;
+
+	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
 
 	if (unlikely(seq == 0 && replay_esn->seq_hi == 0 &&
 		     (replay_esn->seq < replay_esn->replay_window - 1)))