Re: Regression: net/ipv6/mld running system out of memory (not a leak)

On Tue, Mar 03, 2020 at 05:00:35PM +0800, Hangbin Liu wrote:

On Tue, Mar 03, 2020 at 07:16:44AM +0100, Rafał Miłecki wrote:

quoted

It appears that every interface up & down sequence results in adding a
new ff02::2 entry to the idev->mc_tomb. Doing that over and over will
obviously result in running out of memory at some point. That list isn't
cleared until removing an interface.

Thanks Rafał, this info is very useful. When we set interface up, we will
call ipv6_add_dev() and add in6addr_linklocal_allrouters to the mcast list.
But we only remove it in ipv6_mc_destroy_dev(). This make the link down save
the list and link up add a new one.

Maybe we should remove the list in ipv6_mc_down(). like:

Or maybe we just remove the list in addrconf_ifdown(), as opposite of
ipv6_add_dev(), which looks more clear.

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 164c71c54b5c..4369087b8b74 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c

@@ -3841,6 +3841,12 @@ static int addrconf_ifdown(struct net_device *dev, int how)
                ipv6_ac_destroy_dev(idev);
                ipv6_mc_destroy_dev(idev);
        } else {
+               ipv6_dev_mc_dec(dev, &in6addr_interfacelocal_allnodes);
+               ipv6_dev_mc_dec(dev, &in6addr_linklocal_allnodes);
+
+               if (idev->cnf.forwarding && (dev->flags & IFF_MULTICAST))
+                       ipv6_dev_mc_dec(dev, &in6addr_linklocal_allrouters);
+
                ipv6_mc_down(idev);
        }

Thanks
Hangbin