[B.A.T.M.A.N.] Basic Multicast Optimizations

["Linus Lüssing" <linus.luessing@web.de>]

This is the fifth revision of the basic multicast optimization patches.

It fixes two bugs:

For one thing packets to the IPv6 all-hosts-link-scope multicast address
(ff02::1) were optimized, too. However this is the one link local address
which we should not never optimize (see RFC4541, section 3 [1]).

For another since commit 87d4a282 ("batman-adv: remove useless find_router look up"
the unicast-forwarding of multicast packets was broken and I had
only runtime tested the patches based on an older commit
(before 87d4a282 such unicast-forwarding was "only" broken if
a gateway-server was present).


Also note that rebasing on top of the TT-VLAN patches wasn't trivial:
Simply resolving the rebase complaints resulted in subtle runtime
bugs. A few lines in the counting methods added to translation-table.c
needed changes.

Cheers, Linus


[1]: Considerations for Internet Group Management Protocol (IGMP)
     and Multicast Listener Discovery (MLD) Snooping Switches
     -> "Packets with the all hosts link-scope address should be forwarded
         on all ports."
     https://tools.ietf.org/html/rfc4541