How can I accept Lightning channels with fewer confirmations in LDK?

Question

For testing purposes, I want to reduce the number of confirmations required until a LDK-based Lightning node deems a channel ready for operation.

How can I accomplish this?

Answer 1

According to the BOLT #2 specs, the non-funding counterparty indicates which confirmation depth it is willing to accept via the minimum_depth field in the accept_channel message.

In LDK you can configure this for inbound channels via ChannelHandshakeConfig::minimum_depth and the opening counterparty can limit what maximum value it is willing to accept via ChannelHandshakeLimits::max_minimum_depth.

Note that you may also want to enable zero confirmation channels. For outbound channels you can simply enable this via setting ChannelHandshakeLimits::trust_own_fundings_0conf. As inbound zero confirmation channels are a risk for the accepting party, LDK requires you to manually check and accept each such channel. You can enable this by setting UserConfig::manually_accept_inbound_channels, upon which you'll start receiving an OpenChannelRequest event for each inbound channel. For each request you want to accept you then need to call ChannelManager::accept_inbound_channel_from_trusted_peer_0conf, or can force-close the channel otherwise.