linux-kernel - [PATCH 5.5 009/151] ipv6/addrconf: call ipv6_mc

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Date:   Tue, 17 Mar 2020 11:53:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rafał Miłecki <zajec5@...il.com>,
        Hangbin Liu <liuhangbin@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.5 009/151] ipv6/addrconf: call ipv6_mc_up() for non-Ethernet interface

From: Hangbin Liu <liuhangbin@...il.com>

[ Upstream commit 60380488e4e0b95e9e82aa68aa9705baa86de84c ]

Rafał found an issue that for non-Ethernet interface, if we down and up
frequently, the memory will be consumed slowly.

The reason is we add allnodes/allrouters addressed in multicast list in
ipv6_add_dev(). When link down, we call ipv6_mc_down(), store all multicast
addresses via mld_add_delrec(). But when link up, we don't call ipv6_mc_up()
for non-Ethernet interface to remove the addresses. This makes idev->mc_tomb
getting bigger and bigger. The call stack looks like:

addrconf_notify(NETDEV_REGISTER)
	ipv6_add_dev
		ipv6_dev_mc_inc(ff01::1)
		ipv6_dev_mc_inc(ff02::1)
		ipv6_dev_mc_inc(ff02::2)

addrconf_notify(NETDEV_UP)
	addrconf_dev_config
		/* Alas, we support only Ethernet autoconfiguration. */
		return;

addrconf_notify(NETDEV_DOWN)
	addrconf_ifdown
		ipv6_mc_down
			igmp6_group_dropped(ff02::2)
				mld_add_delrec(ff02::2)
			igmp6_group_dropped(ff02::1)
			igmp6_group_dropped(ff01::1)

After investigating, I can't found a rule to disable multicast on
non-Ethernet interface. In RFC2460, the link could be Ethernet, PPP, ATM,
tunnels, etc. In IPv4, it doesn't check the dev type when calls ip_mc_up()
in inetdev_event(). Even for IPv6, we don't check the dev type and call
ipv6_add_dev(), ipv6_dev_mc_inc() after register device.

So I think it's OK to fix this memory consumer by calling ipv6_mc_up() for
non-Ethernet interface.

v2: Also check IFF_MULTICAST flag to make sure the interface supports
    multicast

Reported-by: Rafał Miłecki <zajec5@...il.com>
Tested-by: Rafał Miłecki <zajec5@...il.com>
Fixes: 74235a25c673 ("[IPV6] addrconf: Fix IPv6 on tuntap tunnels")
Fixes: 1666d49e1d41 ("mld: do not remove mld souce list info when set link down")
Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/addrconf.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3345,6 +3345,10 @@ static void addrconf_dev_config(struct n
 	    (dev->type != ARPHRD_NONE) &&
 	    (dev->type != ARPHRD_RAWIP)) {
 		/* Alas, we support only Ethernet autoconfiguration. */
+		idev = __in6_dev_get(dev);
+		if (!IS_ERR_OR_NULL(idev) && dev->flags & IFF_UP &&
+		    dev->flags & IFF_MULTICAST)
+			ipv6_mc_up(idev);
 		return;
 	}