[RFC] Multicast and IPv6 Link Local Addresses

[Jason A. Donenfeld]

Hey George,

On Fri, Apr 7, 2017 at 4:13 PM, George Walker <georgewalkeriv at gmail.com> wrote:
> I'm far from an IP muticast expert, but it would seem more consistent with
> the existing cryptokey routing paradigm if the packets addressed to the
> multicast range went to every peer on that interface which had the multicast
> address addressed among its "allowedIPs."  Then, the only difference between
> configuring multicast and unicast is how many peers may have the same
> allowedIP.

Thanks for this feedback. Indeed this is the initial design I had
thought about and discussed quite a bit. In the name of "simplicity" I
had been nudged back toward the easier special case semantics. I
suppose it's still up in the air.

== Peers Sharing Multiple AllowedIPs Entries ==
Pros:
- Highly configurable.
- More clear what's happening.
Cons:
- Right now there is a strict one-entry-one-peer enforcement, to
maintain the one to one. This has the nice property that if you try to
add the same allowed-ips to the same peer, by accident, the allowed-ip
simply _moves_. I rather like this behavior. Thus, there'd have to be
some explicit way of telling it, "yes I really do want this to be
duplicated, not moved". Perhaps a "multi:" prefix? I don't know, but
it's uglier UI stuff to grok.

== Special Cased Broadcast/Multicast Addresses ==
Pros:
- Simple on and off switch.
Cons:
- A bit too magical.
- Seems to break paradigm.

Hm.

Jason