Move FundingTxInput::sequence to Utxo

A forthcoming commit will change CoinSelection to include FundingTxInput
instead of Utxo, though the former will probably be renamed. This is so
CoinSelectionSource can be used when funding a splice. Further updating
WalletSource to use FundingTxInput is not desirable, however, as it
would result in looking up each confirmed UTXOs previous transaction
even if it is not selected. See Wallet's implementation of
CoinSelectionSource, which delegates to WalletSource for listing all
confirmed UTXOs.

This commit moves FundingTxInput::sequence to Utxo, and thus the
responsibility for setting it to WalletSource implementations. Doing so
will allow Wallet's CoinSelectionSource implementation to delegate
looking up previous transactions to WalletSource without having to
explicitly set the sequence on any FundingTxInput.

Author: jkczyz

lightning/src/events/bump_transaction/mod.rs

@@ -281,12 +281,15 @@ pub struct Utxo {
 	/// with their lengths included, required to satisfy the output's script. The weight consumed by
 	/// the input's `script_sig` must account for [`WITNESS_SCALE_FACTOR`].
 	pub satisfaction_weight: u64,
+	/// The sequence number to use in the [`TxIn`] when spending the UTXO.
+	pub sequence: Sequence,
 }
 
 impl_writeable_tlv_based!(Utxo, {
 	(1, outpoint, required),
 	(3, output, required),
 	(5, satisfaction_weight, required),
+	(7, sequence, (default_value, Sequence::ENABLE_RBF_NO_LOCKTIME)),
 });
 
 impl Utxo {
@@ -301,6 +304,7 @@ impl Utxo {
 			outpoint,
 			output: TxOut { value, script_pubkey: ScriptBuf::new_p2pkh(pubkey_hash) },
 			satisfaction_weight: script_sig_size * WITNESS_SCALE_FACTOR as u64 + 1, /* empty witness */
+			sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 		}
 	}
 
@@ -320,6 +324,7 @@ impl Utxo {
 			},
 			satisfaction_weight: script_sig_size * WITNESS_SCALE_FACTOR as u64
 				+ P2WPKH_WITNESS_WEIGHT,
+			sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 		}
 	}
 
@@ -329,6 +334,7 @@ impl Utxo {
 			outpoint,
 			output: TxOut { value, script_pubkey: ScriptBuf::new_p2wpkh(pubkey_hash) },
 			satisfaction_weight: EMPTY_SCRIPT_SIG_WEIGHT + P2WPKH_WITNESS_WEIGHT,
+			sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 		}
 	}
 }
@@ -717,7 +723,7 @@ where
 			tx.input.push(TxIn {
 				previous_output: utxo.outpoint,
 				script_sig: ScriptBuf::new(),
-				sequence: Sequence::ZERO,
+				sequence: utxo.sequence,
 				witness: Witness::new(),
 			});
 		}
@@ -1343,6 +1349,7 @@ mod tests {
 								script_pubkey: ScriptBuf::new(),
 							},
 							satisfaction_weight: 5, // Just the script_sig and witness lengths
+							sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 						}],
 						change_output: None,
 					},

lightning/src/ln/funding.rs

@@ -108,11 +108,6 @@ pub struct FundingTxInput {
 	/// [`TxOut`]: bitcoin::TxOut
 	pub(super) utxo: Utxo,
 
-	/// The sequence number to use in the [`TxIn`].
-	///
-	/// [`TxIn`]: bitcoin::TxIn
-	pub(super) sequence: Sequence,
-
 	/// The transaction containing the unspent [`TxOut`] referenced by [`utxo`].
 	///
 	/// [`TxOut`]: bitcoin::TxOut
@@ -122,7 +117,7 @@ pub struct FundingTxInput {
 
 impl_writeable_tlv_based!(FundingTxInput, {
 	(1, utxo, required),
-	(3, sequence, required),
+	(3, _sequence, (legacy, Sequence, |input: &FundingTxInput| Some(input.utxo.sequence))),
 	(5, prevtx, required),
 });
 
@@ -140,8 +135,8 @@ impl FundingTxInput {
 					.ok_or(())?
 					.clone(),
 				satisfaction_weight: EMPTY_SCRIPT_SIG_WEIGHT + witness_weight.to_wu(),
+				sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 			},
-			sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 			prevtx,
 		})
 	}
@@ -234,14 +229,14 @@ impl FundingTxInput {
 	///
 	/// [`TxIn`]: bitcoin::TxIn
 	pub fn sequence(&self) -> Sequence {
-		self.sequence
+		self.utxo.sequence
 	}
 
 	/// Sets the sequence number to use in the [`TxIn`].
 	///
 	/// [`TxIn`]: bitcoin::TxIn
 	pub fn set_sequence(&mut self, sequence: Sequence) {
-		self.sequence = sequence;
+		self.utxo.sequence = sequence;
 	}
 
 	/// Converts the [`FundingTxInput`] into a [`Utxo`] for coin selection.

lightning/src/ln/interactivetxs.rs

@@ -2061,9 +2061,13 @@ impl InteractiveTxConstructor {
 
 		let mut inputs_to_contribute: Vec<(SerialId, InputOwned)> = inputs_to_contribute
 			.into_iter()
-			.map(|FundingTxInput { utxo, sequence, prevtx: prev_tx }| {
+			.map(|FundingTxInput { utxo, prevtx: prev_tx }| {
 				let serial_id = generate_holder_serial_id(entropy_source, is_initiator);
-				let txin = TxIn { previous_output: utxo.outpoint, sequence, ..Default::default() };
+				let txin = TxIn {
+					previous_output: utxo.outpoint,
+					sequence: utxo.sequence,
+					..Default::default()
+				};
 				let prev_output = utxo.output;
 				let input = InputOwned::Single(SingleOwnedInput {
 					input: txin,

lightning/src/util/anchor_channel_reserves.rs

@@ -330,7 +330,7 @@ where
 #[cfg(test)]
 mod test {
 	use super::*;
-	use bitcoin::{OutPoint, ScriptBuf, TxOut, Txid};
+	use bitcoin::{OutPoint, ScriptBuf, Sequence, TxOut, Txid};
 	use std::str::FromStr;
 
 	#[test]
@@ -358,6 +358,7 @@ mod test {
 			},
 			output: TxOut { value: amount, script_pubkey: ScriptBuf::new() },
 			satisfaction_weight: 1 * 4 + (1 + 1 + 72 + 1 + 33),
+			sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
 		}
 	}