Index: head/sys/netinet/tcp_hostcache.c
===================================================================
--- head/sys/netinet/tcp_hostcache.c
+++ head/sys/netinet/tcp_hostcache.c
@@ -124,6 +124,12 @@
 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, hostcache, CTLFLAG_RW, 0,
     "TCP Host cache");
 
+VNET_DEFINE(int, tcp_use_hostcache) = 1;
+#define V_tcp_use_hostcache  VNET(tcp_use_hostcache)
+SYSCTL_INT(_net_inet_tcp_hostcache, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
+    &VNET_NAME(tcp_use_hostcache), 0,
+    "Enable the TCP hostcache");
+
 SYSCTL_UINT(_net_inet_tcp_hostcache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
     &VNET_NAME(tcp_hostcache.cache_limit), 0,
     "Overall entry limit for hostcache");
@@ -276,6 +282,9 @@
 	struct hc_head *hc_head;
 	struct hc_metrics *hc_entry;
 
+	if (!V_tcp_use_hostcache)
+		return NULL;
+
 	KASSERT(inc != NULL, ("tcp_hc_lookup with NULL in_conninfo pointer"));
 
 	/*
@@ -332,6 +341,9 @@
 	struct hc_head *hc_head;
 	struct hc_metrics *hc_entry;
 
+	if (!V_tcp_use_hostcache)
+		return NULL;
+
 	KASSERT(inc != NULL, ("tcp_hc_insert with NULL in_conninfo pointer"));
 
 	/*
@@ -421,6 +433,9 @@
 {
 	struct hc_metrics *hc_entry;
 
+	if (!V_tcp_use_hostcache)
+		return;
+
 	/*
 	 * Find the right bucket.
 	 */
@@ -452,7 +467,7 @@
 
 /*
  * External function: look up an entry in the hostcache and return the
- * discovered path MTU.  Returns NULL if no entry is found or value is not
+ * discovered path MTU.  Returns 0 if no entry is found or value is not
  * set.
  */
 u_long
@@ -461,6 +476,9 @@
 	struct hc_metrics *hc_entry;
 	u_long mtu;
 
+	if (!V_tcp_use_hostcache)
+		return 0;
+
 	hc_entry = tcp_hc_lookup(inc);
 	if (hc_entry == NULL) {
 		return 0;
@@ -482,6 +500,9 @@
 {
 	struct hc_metrics *hc_entry;
 
+	if (!V_tcp_use_hostcache)
+		return;
+
 	/*
 	 * Find the right bucket.
 	 */
@@ -521,6 +542,9 @@
 {
 	struct hc_metrics *hc_entry;
 
+	if (!V_tcp_use_hostcache)
+		return;
+
 	hc_entry = tcp_hc_lookup(inc);
 	if (hc_entry == NULL) {
 		hc_entry = tcp_hc_insert(inc);