Broadcast holder commitment for currently confirmed funding #3939
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This is a new `ChannelMonitorUpdateStep` variant intended to be used whenever a new funding transaction that was negotiated and applied via the `RenegotiatedFunding` update reaches its intended confirmation depth and both sides of the channel exchange `channel_ready`/`splice_locked`. This commit primarily focuses on its use for splices, but future work will expand where needed to support RBFs for a dual funded channel. This monitor update ensures that the monitor can safely drop all prior commitment data since it is now considered invalid/unnecessary. Once the update is applied, only state for the new funding transaction is tracked going forward, until the monitor receives another `RenegotiatedFunding` update.
It's only intended to be set during initialization and used to check if the channel is v1 or v2. We rename it to `first_negotiated_funding_txo` to better reflect its purpose.
A `ChannelMonitor` will always consider a channel closed once a confirmed spend for the funding transaction is detected. This is no longer the case with splicing, as the channel will remain open and capable of accepting updates while its funding transaction is being replaced.
A splice's `FundingScope` can only be promoted once a `ChannelMonitorUpdateStep::RenegotiatedFundingLocked` is applied, or if the monitor is no longer accepting updates, once the splice transaction is no longer under reorg risk. Because of this, our current `FundingScope` may not reflect the latest confirmed state in the chain. Before making a holder commitment broadcast, we must check which `FundingScope` is currently confirmed to ensure that it can propogate throughout the network.
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👋 I see @joostjager was un-assigned. |
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A splice's
FundingScopecan only be promoted once aChannelMonitorUpdateStep::RenegotiatedFundingLockedis applied, or if the monitor is no longer accepting updates, once the splice transaction is no longer under reorg risk. Because of this, our currentFundingScopemay not reflect the latest confirmed state in the chain. Before making a holder commitment broadcast, we must check whichFundingScopeis currently confirmed to ensure that it can propagate throughout the network.Depends on #3894.