Patch needs a rebase. Remove in the meantime.

Signed-off-by: David Bauer <mail@david-bauer.net>

to prevent word splitting and globbing

Allow the transmission of IPv6 multicast packets as long as they are not
flooded through the whole mesh.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

With batman-adv 2020.4 and the according backports to batman-adv v2019.2
several more bugs were found and fixed regarding the batman-adv
multicast optimizations feature.

Also a "wakeup-call" feature was added to the Linux bridge IGMP/MLD
snooping code in Gluon to work around issues with Android devices.

With batman-adv now at v2019.2, multicast-to-multi-unicasts conversion
is supported, too. Which means that even if there are a few outdated nodes
these and all other recipients will be served multicast packets via unicast,
too, as long as the sum of receiving nodes does not exceed the multicast
fanout setting (default: 16). If is exceeded, then batman-adv will revert
back to broadcast flooding automatically.

Long story short, with all these extra measures in place, let's reenable
the batman-adv multicast optimizations to reduce the layer 2 overhead
and in preparation for multicast applications in the future.

The default is enabled for this feature anyway, so removing the
"batctl multicast_mode 0" overwrite is sufficient.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

Add a UCI setting gluon.mesh_batman_adv.hop_penalty

Example UCI commands:

    uci set gluon.mesh_batman_adv=mesh_batman_adv
    uci set gluon.mesh_batman_adv.hop_penalty=20
    uci commit

`/etc/config/gluon` config section:

    config mesh_batman_adv 'mesh_batman_adv'
    	option hop_penalty '20'

Fixes: #1942

While we're at it, also slightly optimize proto_gluon_bat0_renew.

The new routing_algo site.conf value BATMAN_IV_LEGACY is introduced. With
these changes, the routing_algo setting becomes mandatory.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

[Matthias Schiffer: move to proto_gluon_bat0_setup() and default to BATMAN_IV]

We now create bat0 and primary0 independently of the lower mesh interfaces,
making the whole setup a lot more robust. In particular:

- we can't accidentially destroy primary0 because of concurrent setup and
  teardown runs of different interfaces
- bat0 will always exist, even when no mesh interfaces are up (e.g. no link
  on wired mesh)
- interfaces going down and up again will never tear down the whole of
  batman-adv
- we can enable and disable bat0 independently of the lower interface
  states