Rename the syn cache counter into tcp_syn_cache_count to have the

same prefix for all variables.  Convert the counter type to int,
the limit is also int.  Before searching the cache, check that it
is not empty.  Do not access the counter outside of the syn cache
from tcp_ctlinput(), let the syn_cache_lookup() function handle it.
OK dlg@

1 files changed, 9 insertions, 7 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 3cd2b0ae0a1..1c9bdbee67f 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcp_input.c,v 1.299 2015/08/13 23:42:16 bluhm Exp $	*/
+/*	$OpenBSD: tcp_input.c,v 1.300 2015/08/24 15:37:03 bluhm Exp $	*/
 /*	$NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $	*/
 
 /*
@@ -3276,7 +3276,7 @@ tcp_mss_adv(struct ifnet *ifp, int af)
  * state for SYN_RECEIVED.
  */
 
-u_long	syn_cache_count;
+int	tcp_syn_cache_count;
 u_int32_t syn_hash1, syn_hash2;
 
 #define SYN_HASH(sa, sp, dp) \
@@ -3324,7 +3324,7 @@ syn_cache_rm(struct syn_cache *sc)
 	LIST_REMOVE(sc, sc_tpq);
 	tcp_syn_cache[sc->sc_bucketidx].sch_length--;
 	timeout_del(&sc->sc_timer);
-	syn_cache_count--;
+	tcp_syn_cache_count--;
 }
 
 void
@@ -3383,7 +3383,7 @@ syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp)
 	 * If there are no entries in the hash table, reinitialize
 	 * the hash secrets.
 	 */
-	if (syn_cache_count == 0) {
+	if (tcp_syn_cache_count == 0) {
 		syn_hash1 = arc4random();
 		syn_hash2 = arc4random();
 	}
@@ -3414,7 +3414,7 @@ syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp)
 #endif
 		syn_cache_rm(sc2);
 		syn_cache_put(sc2);
-	} else if (syn_cache_count >= tcp_syn_cache_limit) {
+	} else if (tcp_syn_cache_count >= tcp_syn_cache_limit) {
 		struct syn_cache_head *scp2, *sce;
 
 		tcpstat.tcps_sc_overflowed++;
@@ -3463,7 +3463,7 @@ syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp)
 	/* Put it into the bucket. */
 	TAILQ_INSERT_TAIL(&scp->sch_bucket, sc, sc_bucketq);
 	scp->sch_length++;
-	syn_cache_count++;
+	tcp_syn_cache_count++;
 
 	tcpstat.tcps_sc_added++;
 	splx(s);
@@ -3568,8 +3568,10 @@ syn_cache_lookup(struct sockaddr *src, struct sockaddr *dst,
 	u_int32_t hash;
 	int s;
 
-	SYN_HASHALL(hash, src, dst);
+	if (tcp_syn_cache_count == 0)
+		return (NULL);
 
+	SYN_HASHALL(hash, src, dst);
 	scp = &tcp_syn_cache[hash % tcp_syn_cache_size];
 	*headp = scp;
 	s = splsoftnet();