Filter IGMP/MLD messges so that we can have an IGMP/MLD querier per
node. Segmenting the IGMP/MLD domain on a per node basis allows us
to *not* rely on a central querier (on a gateway for instance) to
take advantage of multicast snooping.
Even though we receive no more reports from other nodes anymore then,
the "multicast_router" bridge port setting will ensure to always
forward multicast packets towards bat0 (unless filtered by another
ebtables rule).
Note that IGMP/MLD are filtered for multicast traffic coming from
the mesh, too (new MULTICAST_IN), as unfortunately there seem to
be other queriers somewhere in the mesh at least for Freifunk
Lübeck. Such queriers would potentially confuse / silence the
querier on a node.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
