igmp: fix incorrect unsolicit report count after link down and up

After link down and up, i.e. when call ip_mc_up(), we doesn't init
im->unsolicit_count. So after igmp_timer_expire(), we will not start
timer again and only send one unsolicit report at last.

Fix it by initializing im->unsolicit_count in igmp_group_added(), so
we can respect igmp robustness value.

Fixes: 24803f38a5c0b ("igmp: do not remove igmp souce list info when set link down")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/igmp.c

@@ -1307,6 +1307,8 @@ static void igmp_group_added(struct ip_mc_list *im)
 
 	if (in_dev->dead)
 		return;
+
+	im->unsolicit_count = net->ipv4.sysctl_igmp_qrv;
 	if (IGMP_V1_SEEN(in_dev) || IGMP_V2_SEEN(in_dev)) {
 		spin_lock_bh(&im->lock);
 		igmp_start_timer(im, IGMP_INITIAL_REPORT_DELAY);
@@ -1390,9 +1392,6 @@ static void __ip_mc_inc_group(struct in_device *in_dev, __be32 addr,
 			      unsigned int mode)
 {
 	struct ip_mc_list *im;
-#ifdef CONFIG_IP_MULTICAST
-	struct net *net = dev_net(in_dev->dev);
-#endif
 
 	ASSERT_RTNL();
 
@@ -1419,7 +1418,6 @@ static void __ip_mc_inc_group(struct in_device *in_dev, __be32 addr,
 	spin_lock_init(&im->lock);
 #ifdef CONFIG_IP_MULTICAST
 	timer_setup(&im->timer, igmp_timer_expire, 0);
-	im->unsolicit_count = net->ipv4.sysctl_igmp_qrv;
 #endif
 
 	im->next_rcu = in_dev->mc_list;