Channel splicing support #677
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When a channel is spliced, the existing funding transaction's output is spent and a new funding transaction output is formed. Once the splice is considered locked by both parties, LDK will emit a ChannelReady event which will include the new funding_txo. Additionally, the initial ChannelReady event now includes the original funding_txo. Include this data in LDK Node's ChannelReady event.
LDK introduced similar events with splicing. SplicePending is largely informational like ChannelPending. SpliceFailed indicates the used UTXOs can be reclaimed. This requires UTXO locking, which is not yet implemented.
When the interactive-tx construction protocol completes in LDK during splicing (and in the future dual-funding), LDK Node must provide signatures for any non-shared inputs belonging to its on-chain wallet. This commit implements this when handling the corresponding FundingTransactionReadyForSigning event.
Extract the funds availability checking logic from open_channel_inner into a separate method so that it can be reused for channel splicing.
Instead of closing and re-opening a channel when outbound liquidity is exhausted, splicing allows to adding more funds (splice-in) while keeping the channel operational. This commit implements splice-in using funds from the BDK on-chain wallet.
Instead of closing and re-opening a channel when on-chain funds are needed, splicing allows removing funds (splice-out) while keeping the channel operational. This commit implements splice-out sending funds to a user-provided on-chain address.
By default LDK sets UserConfig::reject_inbound_splices to true, thus disallowing splices not specifically requested by the user. This ensures that a counterparty cannot break backwards compatibility. Expose this setting in LDK Node in order to enable splicing for interoperability testing.
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👋 Thanks for assigning @wpaulino as a reviewer! |
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🔔 1st Reminder Hey @tnull @TheBlueMatt @wpaulino! This PR has been waiting for your review. |
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🔔 1st Reminder Hey @tnull @TheBlueMatt @wpaulino! This PR has been waiting for your review. |
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🔔 1st Reminder Hey @tnull @TheBlueMatt @wpaulino! This PR has been waiting for your review. |
2 participants
LDK 0.2 added beta support for splicing. This PR exposes it in LDK Node as two new
Nodemethods:splice_inandsplice_out. Funds used for splicing in are taken from the on-chain BDK wallet. When splicing out, any on-chain address can be provided as the destination.Two new events are provided:
SplicePendingandSpliceFailed. The former is emitted once the new funding transaction has been broadcast. The latter indicates that any contributed inputs may be re-used, though this is not currently exposed. It should be used internally to unlock UTXOs that were intended to be spent.