[WiP] bip324 v2 p2p protocol

[lnliz]

⚠️ This is still a work in progress ⚠️

Add support for bip324 v2 p2p protocol

I worked on bip324 code for the bitcoin-bip324-proxy project and created the v2 p2p transport code so it can be used as a library for other bitcoin projects written in Go. This is POC showing that btcd can use the bip324_transport package to establish v2 connections.
Please disregard the noise in go.mod/go.sum file - I think this needs refactor of the bip324 crypto and transport package in a new package or repo so that proxy dependencies are not pulled in.

This is not a final PR, only to start a conversation and to demo functionality. There are many open questions:

• is btcd project interested in adding bip324 v2 protocol support?
• if yes, what's a good way forward?
• how are external dependencies normally handled?
• I added the v2 code in the code where I thought it would make sense but could use help in fixing the approach.
• the bip324_transport code is not very well tested yet, some help with reviewing and improvement suggestions are welcome.
• still missing: when trying to connect to a v1 node this will fail. bitcoin core then marks the node for reconnect with v1 - this needs something similar.

tested with:

go run . --blocksonly --noonion --maxpeers=10 --nodnsseed --debuglevel=debug --connect=aa.bb.cc.dd:8333

where "aa.bb.cc.dd:8333" is a bitcoin core node that supports v2 (-> bitcoin core v27.0 and up)
or run without "connect" parameter and btcd will try the list of peers it already has

[saubyk]

Hi @lnliz thanks for the pr. This is an important area of work for sure

Just to let you know, this project is already being worked on by @Crypt-iQ (should have the draft pr up soon)
It would be good to reconcile and also get your reviews on it as well

@Crypt-iQ can also post some initial review comments on this pr, but I would urge you to hold-off on this for a bit

[lnliz]

Hey @saubyk and thank you for your comment, that is helpful to know.
I searched for bip324 in the repo but didn't find anything so I submitted the PR as I had the code ready from the work on the bip324 proxy.

I'm ok to wait with this PR until @Crypt-iQ is ready (this was more a POC anyway). And I can also help with reviews on his work and figure out the way forward on how to reconcile.

Keep me posted.

[lnliz]

Hey @Crypt-iQ - just wanted to checkin, did you make any progress on your implementation or had a chance to look here?

[saubyk]

Hi @lnliz I believe #2219 is a precursor pr for BIP324