This patch adds a new gluon-ebtables package to filter IGMP/MLD messages
via ebtables.
For one thing this reduces multicast overhead: About one third of all
ICMPv6 multicast traffic in Lübeck or Hamburg is MLD.
Furthermore it removes a potential Distributed Denial-of-Service vector
(see Gluon ticket #553).
Finally, it is a prerequisite for enabling bridge multicast snooping in
a decentral and robust fashion.
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. Also adding these rules to be prepared to anyone intentionally
or unintentionally disabling these filters on his/her node.
Node operators not running Gluon (for instance gateway nodes) should
make sure to either enable multicast_router towards bat0 or disable
multicast snooping entirely if they have a bridge on top of bat0.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
ebtables actually skips any IPv6 extension headers like the hop-by-hop
one. So this rule is actually void.
The intend back then was to allow passing MLD messages into the mesh.
Since extension headers are skipped, the general icmpv6 rule will
actually match MLD messages. So the hop-by-hop rule is unnecessary,
too.
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
in a layer 2 mesh network, multicast pings cause a lot of traffic in the
network, significantly increasing the 'backgroudn noise' (= Grundrauschen)
and stressing nodes in the network.
this commit blacklists all icmpv4 multicast traffic as well as multicast
icmpv6 echo-requests and node iformation queries. as no application
depending on these types of multicast traffic is known, blacklisting is safe.
the ports were interchanged, see the following packet flow:
client:546 --> [ff02::1:2]:547
server:547 --> client:546
therefore we need to allow outgoing multicast packets with dst-port 547
and unicast packets from bat0 to clients with dst-port 546 and 547 in the other direction
