Introduce RenegotiatedFunding monitor update variant #3822
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We shouldn't track our `HTLCSource`s within our `HolderCommitmentTransaction`s duplicatively for each `FundingScope`. With splicing, we may have alternative holder commitment transactions, but they must all have the same set of non-dust and dust HTLCs as the pre-spliced commitment transaction. Different sets of HTLCs are only possible with a change to the dust limit on commitment transactions, which the splicing protocol does not currently support. This commit moves the `nondust_htlc_sources` and `dust_htlcs` fields out from each `FundingScope` into the `ChannelMonitor`, such that they can be reused for each `FundingScope`. This remains as a backwards compatible change, the underlying stored data is not changed, but where it lives in memory is.
This is a new `ChannelMonitorUpdateStep` variant intended to be used whenever a new funding transaction for the channel has been negotiated via the `InteractiveTxConstructor`. This commit primarily focuses on its use for splices, but future work will expand where needed to support RBFs (both for the initial dual funding transaction, and splice transactions). To draw a parallel to channel open, we generally want to have the commitment transactions negotiated for the funding transaction and committed to the respective `ChannelMonitor` before attempting to sign the funding transaction itself. This monitor update fulfills this need for a newly negotiated splice; it includes both the new holder and counterparty commitment transactions, and the new set of applicable `ChannelTransactionParameters`. Once the monitor update has been applied to the monitor and persisted, we allow the release of our `tx_signatures` for the splice transaction to wait for its confirmation.
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## main #3822 +/- ##
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| fn funding_txid(&self) -> Txid { | ||
| self.channel_parameters.funding_outpoint.as_ref().unwrap().txid |
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Should we use expect here, too?
| if msg.batch.is_some() { | ||
| return Err(ChannelError::close("Peer sent splice initial commitment_signed with a batch".to_owned())); | ||
| } |
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May as well drop this given #3793.
| .map(|session| session.has_received_commitment_signed()) | ||
| .unwrap_or(false); |
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Could you help me understand the difference between the case where session.has_received_commitment_signed() is false and where we don't have an interactive_tx_signing_session?
| let tx_signatures = self.interactive_tx_signing_session.as_mut() | ||
| .and_then(|session| session.received_commitment_signed()); |
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When would we not have an interactive_tx_signing_session here?
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This is a new
ChannelMonitorUpdateStepvariant intended to be used whenever a new funding transaction for the channel has been negotiated via theInteractiveTxConstructor. This commit primarily focuses on its use for splices, but future work will expand where needed to support RBFs (both for the initial dual funding transaction, and splice transactions).To draw a parallel to channel open, we generally want to have the commitment transactions negotiated for the funding transaction and committed to the respective
ChannelMonitorbefore attempting to sign the funding transaction itself. This monitor update fulfills this need for a newly negotiated splice; it includes both the new holder and counterparty commitment transactions, and the new set of applicableChannelTransactionParameters. Once the monitor update has been applied to the monitor and persisted, we allow the release of ourtx_signaturesfor the splice transaction to wait for its confirmation.Note: This currently doesn't build without some of the work done in #3736.
Depends on #3774.