Add splice-out support #3979
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Add splice-out support #3979
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #3979 +/- ##
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- Coverage 88.94% 88.93% -0.02%
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Files 174 174
Lines 124200 124211 +11
Branches 124200 124211 +11
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- Hits 110471 110462 -9
- Misses 11253 11261 +8
- Partials 2476 2488 +12
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Splice contributions should never exceed the total bitcoin supply. This check prevents a potential overflow when converting the contribution from sats to msats. The commit additionally begins to store the contribution using SignedAmount.
…text Once the counterparty supplies their funding contribution, there is no longer a need to store it in FundingNegotiationContext as it will have already been used to create a FundingScope.
Specify what inputs and outputs to contribute to a funding transaction using an enum. This will make the splice-in and upcoming splice-out use cases explicit.
TransactionU16LenLimited was used to limit Transaction serialization size to u16::MAX. This was because messages can not be longer than u16::MAX bytes when serialized for the transport layer. However, this limit doesn't take into account other fields in a message containing a Transaction, including the length of the transaction itself. Remove TransactionU16LenLimited and instead check any user supplied transactions in the context of the enclosing message (e.g. TxAddInput).
In preparation for having ChannelManager::splice_channel take FundingTxContributions, add a weight to the FundingTxContributions::InputsOnly, which supports the splice-in use case.
Using FundingTxContributions for ChannelManager::splice_channel allows supporting both splice-in and splice-out using the same method, with a descriptive enum for the contributions.
Update FundingTxContributions with a variant used to support splice-out (i.e., removing funds from a channel). The TxOut values must not exceed the users channel balance after accounting for fees and the reserve requirement.
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Splice-in support was added in #3736. This PR expands
ChannelManager::splice_channelto support splice-out (i.e., removing funds from a channel). This is accomplished by adding aFundingTxContributionsenum to cover both use cases.Depends on #3736.