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    Subject[PATCH 4.19 06/89] ipv6/addrconf: call ipv6_mc_up() for non-Ethernet interface
    Date
    From: Hangbin Liu <liuhangbin@gmail.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@gmail.com>
    Tested-by: Rafał Miłecki <zajec5@gmail.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@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv6/addrconf.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/net/ipv6/addrconf.c
    +++ b/net/ipv6/addrconf.c
    @@ -3291,6 +3291,10 @@ 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;
    }


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