Explicit commit_sig retransmission for interactive-tx
#1289
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When disconnecting in the middle of the signing steps of an `interactive-tx` transaction, we must retransmit signatures on reconnection to complete the `interactive-tx` protocol. Nodes first exchange `commitment_signed`, followed by `tx_signatures` once they have both sent and received `commitment_signed`. We previously always retransmitted `commitment_signed`, even when our peer had already received it. We now include an explicit bitfield that lets nodes request `commitment_signed` if they haven't received it. Note that this is a breaking change, and we are thus changing the TLV type to make it easier to detect. In practice it should be fine, since only `eclair` and `cln` have shipped support for dual funding, and those two implementations are already incompatible on reconnection because `eclair` implements lightning#1214 but `cln` doesn't. This edge case only creates an issue when nodes disconnect after exchanging `tx_complete` but before receiving signatures, which should happen very infrequently. Replaces lightning#1214.
This was referenced Sep 9, 2025
This was referenced Sep 17, 2025
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When disconnecting in the middle of the signing steps of an
interactive-txtransaction, we must retransmit signatures on reconnection to complete theinteractive-txprotocol.Nodes first exchange
commitment_signed, followed bytx_signaturesonce they have both sent and receivedcommitment_signed.We previously always retransmitted
commitment_signed, even when our peer had already received it. We now include an explicit bitfield that lets nodes requestcommitment_signedif they haven't received it.Note that this is a breaking change, and we are thus changing the TLV type to make it easier to detect. In practice it should be fine, since only
eclairandclnhave shipped support for dual funding, and those two implementations are already incompatible on reconnection becauseeclairimplements #1214 butclndoesn't. This edge case only creates an issue when nodes disconnect after exchangingtx_completebut before receiving signatures, which should happen very infrequently.Replaces #1214.