[IGMP]: Do nothing in ip_mc_down() if ip_mc_up() was not called previously.

include/linux/inetdevice.h

@@ -36,6 +36,8 @@ struct in_device
 	rwlock_t		lock;
 	int			dead;
 	struct in_ifaddr	*ifa_list;	/* IP ifaddr chain		*/
+	int			mc_initted;
+
 	struct ip_mc_list	*mc_list;	/* IP multicast filter chain    */
 	rwlock_t		mc_lock;	/* for mc_tomb */
 	struct ip_mc_list	*mc_tomb;

net/ipv4/igmp.c

@@ -1217,6 +1217,9 @@ void ip_mc_down(struct in_device *in_dev)
 
 	ASSERT_RTNL();
 
+	if (!in_dev->mc_initted)
+		return;
+
 #ifdef CONFIG_IP_MULTICAST
 	in_dev->mr_ifc_count = 0;
 	if (del_timer(&in_dev->mr_ifc_timer))
@@ -1262,6 +1265,8 @@ void ip_mc_up(struct in_device *in_dev)
 
 	for (i=in_dev->mc_list; i; i=i->next)
 		igmp_group_added(i);
+
+	in_dev->mc_initted = 1;
 }
 
 /*