: revert MASQUERADE optimization for mostly static IPs

diff -Nru a/net/ipv4/netfilter/ipt_MASQUERADE.c b/net/ipv4/netfilter/ipt_MASQUERADE.c
@@ -125,35 +125,58 @@
 }
 
 static inline int
-device_cmp(const struct ip_conntrack *i, void *_ina)
+device_cmp(const struct ip_conntrack *i, void *ifindex)
 {
-	int ret = 0;
-	struct in_ifaddr *ina = _ina;
+	int ret;
 
 	READ_LOCK(&masq_lock);
-	/* If it's masquerading out this interface with a different address,
-	 * or we don't know the new address of this interface. */
-	if (i->nat.masq_index == ina->ifa_dev->dev->ifindex
-	    && i->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip != ina->ifa_address)
-		ret = 1;
+	ret = (i->nat.masq_index == (int)(long)ifindex);
 	READ_UNLOCK(&masq_lock);
 
 	return ret;
 }
 
+static int masq_device_event(struct notifier_block *this,
+			     unsigned long event,
+			     void *ptr)
+{
+	struct net_device *dev = ptr;
+
+	if (event == NETDEV_DOWN) {
+		/* Device was downed.  Search entire table for
+		   conntracks which were associated with that device,
+		   and forget them. */
+		IP_NF_ASSERT(dev->ifindex != 0);
+ 
+		ip_ct_selective_cleanup(device_cmp, (void *)(long)dev->ifindex);
+	}
+
+	return NOTIFY_DONE;
+}
+
+
 static int masq_inet_event(struct notifier_block *this,
 			   unsigned long event,
 			   void *ptr)
 {
-	/* For some configurations, interfaces often come back with
-	 * the same address.  If not, clean up old conntrack
-	 * entries. */
-	if (event == NETDEV_UP)
-		ip_ct_selective_cleanup(device_cmp, ptr);
+	struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
+
+	if (event == NETDEV_DOWN) {
+		/* IP address was deleted.  Search entire table for
+		   conntracks which were associated with that device,
+		   and forget them. */
+		IP_NF_ASSERT(dev->ifindex != 0);
+
+		ip_ct_selective_cleanup(device_cmp, (void *)(long)dev->ifindex);
+	}
 
 	return NOTIFY_DONE;
 }
 
+static struct notifier_block masq_dev_notifier = {
+	.notifier_call  = masq_device_event,
+};
+
 static struct notifier_block masq_inet_notifier = {
 	.notifier_call = masq_inet_event
 };

@@ -168,9 +191,12 @@
 
 	ret = ipt_register_target(&masquerade);
 
-	if (ret == 0)
+	if (ret == 0) {
+		/* Register for device down reports */
+		register_netdevice_notifier(&masq_dev_notifier);
 		/* Register IP address change reports */
 		register_inetaddr_notifier(&masq_inet_notifier);
+	}
 
 	return ret;
 }

@@ -178,6 +204,7 @@
 static void __exit fini(void)
 {
 	ipt_unregister_target(&masquerade);
+	unregister_netdevice_notifier(&masq_dev_notifier);
 	unregister_inetaddr_notifier(&masq_inet_notifier);	
 }