[avahi] multiple ethernet ports

[Zachary Loafman]

> Yes. Avahi is perfectly capable of dealing with multihomed hosts.

Q: How is this supposed to work if the host is multihomed across
different fabrics? For example, I have:

zc-1# ifconfig
em0: flags=408843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=30b<RXCSUM,TXCSUM,VLAN_MTU,TSO4,TSO6>
        inet 169.254.4.36 netmask 0xffff0000 broadcast 169.254.255.255
        ether 00:0c:29:60:3f:55
        media: Ethernet autoselect (1000baseTX <full-duplex>)
        status: active
        flexnet: internal
em1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=30b<RXCSUM,TXCSUM,VLAN_MTU,TSO4,TSO6>
        inet 169.254.84.168 netmask 0xffff0000 broadcast 169.254.255.255
        ether 00:0c:29:60:3f:5f
        media: Ethernet autoselect (1000baseTX <full-duplex>)
        status: active
        flexnet: unused

em0 and em1 are connected to separate physical networks.

Amusingly, after fixing multicast issues on BSD, avahi-browse works
fine (I can talk mDNS over both em0 and em1 with no 169.254/16
routes). However, I can't figure out how one would get the routing
correct for this situation for normal traffic. If I just add a
169.254/16 routes, one interface can talk on one network. To do this
in any reasonable way, it seems like I'd need to actively update
routing tables with known hosts (and some expiration). Any thoughts?

...Zach