Hi,

The following are two patches for the Linux bridge regarding multicast
routers. They are rebased on top of the following fix:
"net: bridge: mcast: fix broken length + header check for MRDv6 Adv." [0]
And should be applied afterwards.

The first one splits the so far combined multicast router state into two
ones, one for IPv4 and one for IPv6, for a more fine-grained detection of
multicast routers. This avoids sending IPv4 multicast packets to an
IPv6-only multicast router and avoids sending IPv6 multicast packets to
an IPv4-only multicast router. This is also in preparation for the
second patch:

The second patch exports this now per protocol family multicast router
state so that batman-adv can then later make full use of the
Multicast Router Discovery (MRD) support in the Linux bridge. The
batman-adv protocol format currently expects separate multicast router
states for IPv4 and IPv6, therefore it depends on the first patch.
batman-adv will then make use of this newly exported functions like
this[1].

Regards, Linus

[0]: https://patchwork.kernel.org/project/netdevbpf/patch/20210425152736.8421-1-linus.luessing@c0d3.blue/
[1]: https://git.open-mesh.org/batman-adv.git/shortlog/refs/heads/linus/multicast-routeable-mrd
     -> https://git.open-mesh.org/batman-adv.git/commit/d4bed3a92427445708baeb1f2d1841c5fb816fd4