Commit 4eba7bb1 authored Dec 01, 2015 by Andrew Lunn Committed by David S. Miller Dec 03, 2015

ipv4: igmp: Allow removing groups from a removed interface



When a multicast group is joined on a socket, a struct ip_mc_socklist
is appended to the sockets mc_list containing information about the
joined group.

If the interface is hot unplugged, this entry becomes stale. Prior to
commit 52ad353a ("igmp: fix the problem when mc leave group") it
was possible to remove the stale entry by performing a
IP_DROP_MEMBERSHIP, passing either the old ifindex or ip address on
the interface. However, this fix enforces that the interface must
still exist. Thus with time, the number of stale entries grows, until
sysctl_igmp_max_memberships is reached and then it is not possible to
join and more groups.

The previous patch fixes an issue where a IP_DROP_MEMBERSHIP is
performed without specifying the interface, either by ifindex or ip
address. However here we do supply one of these. So loosen the
restriction on device existence to only apply when the interface has
not been specified. This then restores the ability to clean up the
stale entries.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Fixes: 52ad353a "(igmp: fix the problem when mc leave group")
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 602dd62d

net/ipv4/igmp.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -2126,7 +2126,7 @@ int ip_mc_leave_group(struct sock sk, struct ip_mreqn imr)
		ASSERT_RTNL();

		in_dev = ip_mc_find_dev(net, imr);
		if (!in_dev) {
		if (!imr->imr_ifindex && !imr->imr_address.s_addr && !in_dev) {
		ret = -ENODEV;
		goto out;
		}
		@@ -2147,6 +2147,7 @@ int ip_mc_leave_group(struct sock sk, struct ip_mreqn imr)

		*imlp = iml->next_rcu;

		if (in_dev)
		ip_mc_dec_group(in_dev, group);

		/* decrease mem now to avoid the memleak warning */

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