Use routable source IP addresses inside Opulent Voice frames

[MustBeArt]

Currently we use a fallback address of 127.0.0.1 for the source address. That's not right, the loopback address should never be the source address of anything.

What address to use is an interesting problem. I think it depends on the architecture.

For an architecture like Haifuraiya, with a central node, we could use 10.0.0.0/8 or 192.168.0.0/16 addresses and dispense them from the satellite using DHCP or something similar. This could be tied in with the AAAAA mechanism, or not. These addresses would need to be restricted to our private network, though. Destination addresses on the private network don't always correspond to individual user stations. Some of them, maybe the only important ones, correspond to rooms or other ways to categorize data. These could be vended by the satellite on demand whenever somebody wants to open a new room.

If we ever want to interconnect the Opulent Voice network, whatever type it may be, with the real Internet, then we need to be able to use real routable IP addresses at least some of the time. These would probably have to be addresses assigned by local ISPs, since the whole idea would be to be reachable over the Internet. Or, there could be something like a Tailscale tailnet on the non-amateur side, and everybody would just use private-network addresses there as well as on the air.

I'm thinking mainly about IPv4 addresses, since that's what we've designed in. We probably need to figure out how to interconnect with the IPv6 Internet while still using IPv4 addresses internally. But since nobody has really figured out how to interconnect an amateur radio network to the Wild West Internet and stay legal, maybe that's not so critical.

For the purposes of this issue, it's probably good enough to make the Opulent Voice internal IPv4 address a configuration item.