Enable Tor v3 address support for Neutrino client mode

[bitcoinlizard]

Background

Tor v3 address are not supported in Neutrino client mode. This is discussed in the first comment here:

#4806

This is more relevant as bitcoind recently released version 0.21.0 which adds support for serving compact filters to peers. Bitcoind also switched to Tor v3 addresses as a default in version 0.21.0 (older versions only supported v2). Enabling Tor v3 address support could increase the number of Neutrino mode LND nodes deployed as there would be many more backends available.

[Roasbeef]

Note that in order to implement this, we'll need to implement the new addrv2 scheme within the btcsuite set of libraries. After we do that, neutrino will get this feature "for free".

[openoms]

Would like note that there is a time limit here:

https://blog.torproject.org/v2-deprecation-timeline

3. October 15th, 2021
We will release new Tor client stable versions for all supported series that will disable v2.

As mentioned here also: #5771 (comment)

[bitcoinlizard]

A lot of Tor only Neutrino LND nodes are going to go offline in short order. I run a Tor v2 BTCD node and have at times seen 50+ Neutrino nodes connected to it. As I understand it the btcsuite upgrade will resolve the issue for both LND and BTCD.

[Roasbeef]

We're aware of the time limit, but unfortunately this won't make it into 0.14 as slated. See the newly created milestone that tracks this inclusion.

As usual: contributions are accepted here. BIP 155 isn't too involved, but this fell through the cracks somewhat w/ all the other PR/issues and priorities.

[Roasbeef]

Note that I have started a BIP 155 implementation, pretty confident I can finish it before the end of October (see the milestone this issue is attached to).

[nochiel]

Note that I have started a BIP 155 implementation, pretty confident I can finish it before the end of October (see the milestone this issue is attached to).

@Roasbeef Which branch in your repo should I look at for what you've implemented so far? I'd love to contribute and help get it done.

[Roasbeef]

Update on this: we're in active testing, a PR should be up in the next few days!

[Roasbeef]

The btcd PR (where most of this code lives), is here: btcsuite/btcd#1812

[Roasbeef]

PR has been merged, so this is only blocked on the updates to the neutrino package.