DRAFT: Dual funding messages (funding)

Oct 25, 2022

https://github.com/lightningdevkit/rust-lightning/pull/1794

Host: ariard  -  PR author: dunxen

The PR branch HEAD was b1d3eee at the time of this review club meeting.

Notes

• Historically, the funding UTXOs have been provided by a single counterparty, leading to the hard issue of bootstrapping inbound liquidity for services providers and nodes.
• Few solutions have been developed in an attempt to palliate this issue: submarine swaps, liquidity ads, inbound channel request
• #1754 starts the support of dual-funding, a new funding flow enabling both sides of a channel to commit UTXOs.

Questions

1. What’s the message flow of channel opening V1 ? What the logically equivalent sequence of checks processed by both acceptor and initiator ? What are the policy checks realized ?
2. What’s the dual-funding proposal ? How the mechanism works compared to single-funded channel and the push_msat setting ?
3. What dual-funding bring as a liquidity tooling compared to a swap ? What are the trade-offs ?
4. Dual-funding builds on top of the interactive construction protocol, which introduces a collaborative fee-bumping Replace-by-Fee mechanism ? What’s the trade-offs in terms of cost/liveliness/key management/etc compared to Child-Pay-For-Parent ?
5. What are the downsides of dual-funding with “untrusted” Lightning counterparties, especially in multi-party context ?