};
use crate::events::Event;
use crate::prelude::HashMap;
+use crate::sync::Mutex;
use crate::util::logger::Logger;
use bitcoin::{OutPoint, PackedLockTime, PubkeyHash, Sequence, Script, Transaction, Txid, TxIn, TxOut, Witness, WPubkeyHash};
/// An abstraction over a bitcoin wallet that can perform coin selection over a set of UTXOs and can
/// sign for them. The coin selection method aims to mimic Bitcoin Core's `fundrawtransaction` RPC,
-/// which most wallets should be able to satisfy.
+/// which most wallets should be able to satisfy. Otherwise, consider implementing [`WalletSource`],
+/// which can provide a default implementation of this trait when used with [`Wallet`].
pub trait CoinSelectionSource {
/// Performs coin selection of a set of UTXOs, with at least 1 confirmation each, that are
/// available to spend. Implementations are free to pick their coin selection algorithm of
fn sign_tx(&self, tx: &mut Transaction) -> Result<(), ()>;
}
+/// An alternative to [`CoinSelectionSource`] that can be implemented and used along [`Wallet`] to
+/// provide a default implementation to [`CoinSelectionSource`].
+pub trait WalletSource {
+ /// Returns all UTXOs, with at least 1 confirmation each, that are available to spend.
+ fn list_confirmed_utxos(&self) -> Result<Vec<Utxo>, ()>;
+ /// Returns a script to use for change above dust resulting from a successful coin selection
+ /// attempt.
+ fn get_change_script(&self) -> Result<Script, ()>;
+ /// Signs and provides the full [`TxIn::script_sig`] and [`TxIn::witness`] for all inputs within
+ /// the transaction known to the wallet (i.e., any provided via
+ /// [`WalletSource::list_confirmed_utxos`]).
+ fn sign_tx(&self, tx: &mut Transaction) -> Result<(), ()>;
+}
+
+/// A wrapper over [`WalletSource`] that implements [`CoinSelection`] by preferring UTXOs that would
+/// avoid conflicting double spends. If not enough UTXOs are available to do so, conflicting double
+/// spends may happen.
+pub struct Wallet<W: Deref> where W::Target: WalletSource {
+ source: W,
+ // TODO: Do we care about cleaning this up once the UTXOs have a confirmed spend? We can do so
+ // by checking whether any UTXOs that exist in the map are no longer returned in
+ // `list_confirmed_utxos`.
+ locked_utxos: Mutex<HashMap<OutPoint, ClaimId>>,
+}
+
+impl<W: Deref> Wallet<W> where W::Target: WalletSource {
+ /// Returns a new instance backed by the given [`WalletSource`] that serves as an implementation
+ /// of [`CoinSelectionSource`].
+ pub fn new(source: W) -> Self {
+ Self { source, locked_utxos: Mutex::new(HashMap::new()) }
+ }
+
+ /// Performs coin selection on the set of UTXOs obtained from
+ /// [`WalletSource::list_confirmed_utxos`]. Its algorithm can be described as "smallest
+ /// above-dust-after-spend first", with a slight twist: we may skip UTXOs that are above dust at
+ /// the target feerate after having spent them in a separate claim transaction if
+ /// `force_conflicting_utxo_spend` is unset to avoid producing conflicting transactions. If
+ /// `tolerate_high_network_feerates` is set, we'll attempt to spend UTXOs that contribute at
+ /// least 1 satoshi at the current feerate, otherwise, we'll only attempt to spend those which
+ /// contribute at least twice their fee.
+ fn select_confirmed_utxos_internal(
+ &self, utxos: &[Utxo], claim_id: ClaimId, force_conflicting_utxo_spend: bool,
+ tolerate_high_network_feerates: bool, target_feerate_sat_per_1000_weight: u32,
+ preexisting_tx_weight: u64, target_amount_sat: u64,
+ ) -> Result<CoinSelection, ()> {
+ let mut locked_utxos = self.locked_utxos.lock().unwrap();
+ let mut eligible_utxos = utxos.iter().filter_map(|utxo| {
+ if let Some(utxo_claim_id) = locked_utxos.get(&utxo.outpoint) {
+ if *utxo_claim_id != claim_id && !force_conflicting_utxo_spend {
+ return None;
+ }
+ }
+ let fee_to_spend_utxo = fee_for_weight(
+ target_feerate_sat_per_1000_weight, BASE_INPUT_WEIGHT as u64 + utxo.satisfaction_weight,
+ );
+ let should_spend = if tolerate_high_network_feerates {
+ utxo.output.value > fee_to_spend_utxo
+ } else {
+ utxo.output.value >= fee_to_spend_utxo * 2
+ };
+ if should_spend {
+ Some((utxo, fee_to_spend_utxo))
+ } else {
+ None
+ }
+ }).collect::<Vec<_>>();
+ eligible_utxos.sort_unstable_by_key(|(utxo, _)| utxo.output.value);
+
+ let mut selected_amount = 0;
+ let mut total_fees = fee_for_weight(target_feerate_sat_per_1000_weight, preexisting_tx_weight);
+ let mut selected_utxos = Vec::new();
+ for (utxo, fee_to_spend_utxo) in eligible_utxos {
+ if selected_amount >= target_amount_sat + total_fees {
+ break;
+ }
+ selected_amount += utxo.output.value;
+ total_fees += fee_to_spend_utxo;
+ selected_utxos.push(utxo.clone());
+ }
+ if selected_amount < target_amount_sat + total_fees {
+ return Err(());
+ }
+ for utxo in &selected_utxos {
+ locked_utxos.insert(utxo.outpoint, claim_id);
+ }
+ core::mem::drop(locked_utxos);
+
+ let remaining_amount = selected_amount - target_amount_sat - total_fees;
+ let change_script = self.source.get_change_script()?;
+ let change_output_fee = fee_for_weight(
+ target_feerate_sat_per_1000_weight,
+ (8 /* value */ + change_script.consensus_encode(&mut sink()).unwrap() as u64) *
+ WITNESS_SCALE_FACTOR as u64,
+ );
+ let change_output_amount = remaining_amount.saturating_sub(change_output_fee);
+ let change_output = if change_output_amount < change_script.dust_value().to_sat() {
+ None
+ } else {
+ Some(TxOut { script_pubkey: change_script, value: change_output_amount })
+ };
+
+ Ok(CoinSelection {
+ confirmed_utxos: selected_utxos,
+ change_output,
+ })
+ }
+}
+
+impl<W: Deref> CoinSelectionSource for Wallet<W> where W::Target: WalletSource {
+ fn select_confirmed_utxos(
+ &self, claim_id: ClaimId, must_spend: &[Input], must_pay_to: &[TxOut],
+ target_feerate_sat_per_1000_weight: u32,
+ ) -> Result<CoinSelection, ()> {
+ let utxos = self.source.list_confirmed_utxos()?;
+ // TODO: Use fee estimation utils when we upgrade to bitcoin v0.30.0.
+ const BASE_TX_SIZE: u64 = 4 /* version */ + 1 /* input count */ + 1 /* output count */ + 4 /* locktime */;
+ let total_output_size: u64 = must_pay_to.iter().map(|output|
+ 8 /* value */ + 1 /* script len */ + output.script_pubkey.len() as u64
+ ).sum();
+ let total_satisfaction_weight: u64 = must_spend.iter().map(|input| input.satisfaction_weight).sum();
+ let total_input_weight = (BASE_INPUT_WEIGHT * must_spend.len() as u64) + total_satisfaction_weight;
+
+ let preexisting_tx_weight = 2 /* segwit marker & flag */ + total_input_weight +
+ ((BASE_TX_SIZE + total_output_size) * WITNESS_SCALE_FACTOR as u64);
+ let target_amount_sat = must_pay_to.iter().map(|output| output.value).sum();
+ let do_coin_selection = |force_conflicting_utxo_spend: bool, tolerate_high_network_feerates: bool| {
+ self.select_confirmed_utxos_internal(
+ &utxos, claim_id, force_conflicting_utxo_spend, tolerate_high_network_feerates,
+ target_feerate_sat_per_1000_weight, preexisting_tx_weight, target_amount_sat,
+ )
+ };
+ do_coin_selection(false, false)
+ .or_else(|_| do_coin_selection(false, true))
+ .or_else(|_| do_coin_selection(true, false))
+ .or_else(|_| do_coin_selection(true, true))
+ }
+
+ fn sign_tx(&self, tx: &mut Transaction) -> Result<(), ()> {
+ self.source.sign_tx(tx)
+ }
+}
+
/// A handler for [`Event::BumpTransaction`] events that sources confirmed UTXOs from a
/// [`CoinSelectionSource`] to fee bump transactions via Child-Pays-For-Parent (CPFP) or
/// Replace-By-Fee (RBF).
projects / rust-lightning / commitdiff