No IPv6 support in uTP/DHT

I was trying out Dat and noticed that IPv6 is not used to reach peers. This pretty seriously limits its usefulness for me, so I looked around the internals a bit. On a high level, I think the following changes would be needed in discovery-swarm to fix this:

• Create separete IPv4 and IPv6 uTP sockets.
• Run separate instances of bittorrent-dht for IPv4 and IPv6 on each socket (technically these could be merged, but makes the implementation a lot more complex for relatively little benefit).
• Hide the distinction from higher layers (discovery-channel and up). It seems that this would happen pretty much automagically due to the event architecture.

On the lower levels, looks like this needs:

• Support for binding IPv6 sockets in utp-native. Seems like a minor change, libutp already has support so just needs selecting the right libuv functions based on the input address.
• Support for BEP-32 in bittorrent-dht and the k-rpc modules. A bit of work, but BEP-32 is pretty simple, and with DHT instances handling a single socket this shouldn’t cause any major restructuring.
• dns-discovery: no idea, not going to go there for now, would continue using the current (IPv4) socket as before.

I may have some time to work on this in the near future. Does the approach sound reasonable?

[RangerMauve]

@vuori I’m going to be doing some stability work on hyperswarm, I’ll see if I can put in IPv6 support in my spare time.

[vuori]

I’m not familiar with i2p. If you mean IPv6, it turned out that the rabbit hole went a bit too deep for a weekend project, so the issue has been on the shelf.