igmp: call ip_mc_clear_src() only when we have no users of ip_mc_list

BugLink: http://bugs.launchpad.net/bugs/793702

[ Upstream commit 24cf3af3fed5edcf90bc2a0ed181e6ce1513d2dc ]

In igmp_group_dropped() we call ip_mc_clear_src(), which resets the number
of source filters per mulitcast. However, igmp_group_dropped() is also
called on NETDEV_DOWN, NETDEV_PRE_TYPE_CHANGE and NETDEV_UNREGISTER, which
means that the group might get added back on NETDEV_UP, NETDEV_REGISTER and
NETDEV_POST_TYPE_CHANGE respectively, leaving us with broken source
filters.

To fix that, we must clear the source filters only when there are no users
in the ip_mc_list, i.e. in ip_mc_dec_group() and on device destroy.

Acked-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index e0e77e2..d9d5130 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1172,20 +1172,18 @@ static void igmp_group_dropped(struct ip_mc_list *im)
 
        if (!in_dev->dead) {
                if (IGMP_V1_SEEN(in_dev))
-                       goto done;
+                       return;
                if (IGMP_V2_SEEN(in_dev)) {
                        if (reporter)
                                igmp_send_report(in_dev, im, IGMP_HOST_LEAVE_MESSAGE);
-                       goto done;
+                       return;
                }
                /* IGMPv3 */
                igmpv3_add_delrec(in_dev, im);
 
                igmp_ifc_event(in_dev);
        }
-done:
 #endif
-       ip_mc_clear_src(im);
 }
 
 static void igmp_group_added(struct ip_mc_list *im)
@@ -1322,6 +1320,7 @@ void ip_mc_dec_group(struct in_device *in_dev, __be32 addr)
                                *ip = i->next_rcu;
                                in_dev->mc_count--;
                                igmp_group_dropped(i);
+                               ip_mc_clear_src(i);
 
                                if (!in_dev->dead)
                                        ip_rt_multicast_event(in_dev);
@@ -1431,7 +1430,8 @@ void ip_mc_destroy_dev(struct in_device *in_dev)
                in_dev->mc_list = i->next_rcu;
                in_dev->mc_count--;
 
-               igmp_group_dropped(i);
+               /* We've dropped the groups in ip_mc_down already */
+               ip_mc_clear_src(i);
                ip_ma_put(i);
        }
 }