Re: [PATCH 1/2] IGMP snooping: set mrouters_only flag for IPv4 traffic properly

From: Fernando Luis Vázquez Cao <redacted>
Date: Tue, 14 Jun 2011 10:04:43 +0900

Upon reception of a IGMP/IGMPv2 membership report the kernel sets the
mrouters_only flag in a skb that may be a clone of the original skb, which
means that sometimes the bridge loses track of membership report packets (cb
buffers are tied to a specific skb and not shared) and it ends up forwading
join requests to the bridge interface.

This can cause unexpected membership timeouts and intermitent/permanent loss
of connectivity as described in RFC 4541 [2.1.1. IGMP Forwarding Rules]:

    A snooping switch should forward IGMP Membership Reports only to
    those ports where multicast routers are attached.
    [...]
    Sending membership reports to other hosts can result, for IGMPv1
    and IGMPv2, in unintentionally preventing a host from joining a
    specific multicast group.


Signed-off-by: Fernando Luis Vazquez Cao <redacted>
Tested-by: Hayato Kakuta <redacted>

Applied.