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
