// You may not use this file except in accordance with one or both of these
// licenses.
-//! Utitilies for bumping transactions originating from [`super::Event`]s.
+//! Utilities for bumping transactions originating from [`Event`]s.
+//!
+//! [`Event`]: crate::events::Event
-use crate::ln::PaymentPreimage;
+use alloc::collections::BTreeMap;
+use core::ops::Deref;
+
+use crate::chain::chaininterface::{BroadcasterInterface, fee_for_weight};
+use crate::chain::ClaimId;
+use crate::io_extras::sink;
+use crate::ln::channel::ANCHOR_OUTPUT_VALUE_SATOSHI;
use crate::ln::chan_utils;
-use crate::ln::chan_utils::{ChannelTransactionParameters, HTLCOutputInCommitment};
+use crate::ln::chan_utils::{
+ ANCHOR_INPUT_WITNESS_WEIGHT, HTLC_SUCCESS_INPUT_ANCHOR_WITNESS_WEIGHT,
+ HTLC_TIMEOUT_INPUT_ANCHOR_WITNESS_WEIGHT, HTLCOutputInCommitment
+};
+use crate::prelude::*;
+use crate::sign::{
+ ChannelDerivationParameters, HTLCDescriptor, SignerProvider, P2WPKH_WITNESS_WEIGHT
+};
+use crate::sign::ecdsa::{EcdsaChannelSigner, WriteableEcdsaChannelSigner};
+use crate::sync::Mutex;
+use crate::util::logger::Logger;
-use bitcoin::{OutPoint, PackedLockTime, Script, Transaction, Txid, TxIn, TxOut, Witness};
+use bitcoin::{OutPoint, PubkeyHash, Sequence, ScriptBuf, Transaction, TxIn, TxOut, Witness, WPubkeyHash};
+use bitcoin::blockdata::constants::WITNESS_SCALE_FACTOR;
+use bitcoin::blockdata::locktime::absolute::LockTime;
+use bitcoin::consensus::Encodable;
+use bitcoin::psbt::PartiallySignedTransaction;
use bitcoin::secp256k1;
-use bitcoin::secp256k1::{PublicKey, Secp256k1};
+use bitcoin::secp256k1::Secp256k1;
use bitcoin::secp256k1::ecdsa::Signature;
+const EMPTY_SCRIPT_SIG_WEIGHT: u64 = 1 /* empty script_sig */ * WITNESS_SCALE_FACTOR as u64;
+
+const BASE_INPUT_SIZE: u64 = 32 /* txid */ + 4 /* vout */ + 4 /* sequence */;
+
+const BASE_INPUT_WEIGHT: u64 = BASE_INPUT_SIZE * WITNESS_SCALE_FACTOR as u64;
+
/// A descriptor used to sign for a commitment transaction's anchor output.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct AnchorDescriptor {
- /// A unique identifier used along with `channel_value_satoshis` to re-derive the
- /// [`InMemorySigner`] required to sign `input`.
- ///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- pub channel_keys_id: [u8; 32],
- /// The value in satoshis of the channel we're attempting to spend the anchor output of. This is
- /// used along with `channel_keys_id` to re-derive the [`InMemorySigner`] required to sign
- /// `input`.
- ///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- pub channel_value_satoshis: u64,
+ /// The parameters required to derive the signer for the anchor input.
+ pub channel_derivation_parameters: ChannelDerivationParameters,
/// The transaction input's outpoint corresponding to the commitment transaction's anchor
/// output.
pub outpoint: OutPoint,
}
-/// A descriptor used to sign for a commitment transaction's HTLC output.
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct HTLCDescriptor {
- /// A unique identifier used along with `channel_value_satoshis` to re-derive the
- /// [`InMemorySigner`] required to sign `input`.
- ///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- pub channel_keys_id: [u8; 32],
- /// The value in satoshis of the channel we're attempting to spend the anchor output of. This is
- /// used along with `channel_keys_id` to re-derive the [`InMemorySigner`] required to sign
- /// `input`.
- ///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- pub channel_value_satoshis: u64,
- /// The necessary channel parameters that need to be provided to the re-derived
- /// [`InMemorySigner`] through [`ChannelSigner::provide_channel_parameters`].
- ///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- /// [`ChannelSigner::provide_channel_parameters`]: crate::sign::ChannelSigner::provide_channel_parameters
- pub channel_parameters: ChannelTransactionParameters,
- /// The txid of the commitment transaction in which the HTLC output lives.
- pub commitment_txid: Txid,
- /// The number of the commitment transaction in which the HTLC output lives.
- pub per_commitment_number: u64,
- /// The details of the HTLC as it appears in the commitment transaction.
- pub htlc: HTLCOutputInCommitment,
- /// The preimage, if `Some`, to claim the HTLC output with. If `None`, the timeout path must be
- /// taken.
- pub preimage: Option<PaymentPreimage>,
- /// The counterparty's signature required to spend the HTLC output.
- pub counterparty_sig: Signature
-}
+impl AnchorDescriptor {
+ /// Returns the UTXO to be spent by the anchor input, which can be obtained via
+ /// [`Self::unsigned_tx_input`].
+ pub fn previous_utxo(&self) -> TxOut {
+ TxOut {
+ script_pubkey: self.witness_script().to_v0_p2wsh(),
+ value: ANCHOR_OUTPUT_VALUE_SATOSHI,
+ }
+ }
-impl HTLCDescriptor {
- /// Returns the unsigned transaction input spending the HTLC output in the commitment
+ /// Returns the unsigned transaction input spending the anchor output in the commitment
/// transaction.
pub fn unsigned_tx_input(&self) -> TxIn {
- chan_utils::build_htlc_input(&self.commitment_txid, &self.htlc, true /* opt_anchors */)
+ TxIn {
+ previous_output: self.outpoint.clone(),
+ script_sig: ScriptBuf::new(),
+ sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
+ witness: Witness::new(),
+ }
}
- /// Returns the delayed output created as a result of spending the HTLC output in the commitment
- /// transaction.
- pub fn tx_output<C: secp256k1::Signing + secp256k1::Verification>(
- &self, per_commitment_point: &PublicKey, secp: &Secp256k1<C>
- ) -> TxOut {
- let channel_params = self.channel_parameters.as_holder_broadcastable();
- let broadcaster_keys = channel_params.broadcaster_pubkeys();
- let counterparty_keys = channel_params.countersignatory_pubkeys();
- let broadcaster_delayed_key = chan_utils::derive_public_key(
- secp, per_commitment_point, &broadcaster_keys.delayed_payment_basepoint
- );
- let counterparty_revocation_key = chan_utils::derive_public_revocation_key(
- secp, per_commitment_point, &counterparty_keys.revocation_basepoint
- );
- chan_utils::build_htlc_output(
- 0 /* feerate_per_kw */, channel_params.contest_delay(), &self.htlc, true /* opt_anchors */,
- false /* use_non_zero_fee_anchors */, &broadcaster_delayed_key, &counterparty_revocation_key
- )
- }
-
- /// Returns the witness script of the HTLC output in the commitment transaction.
- pub fn witness_script<C: secp256k1::Signing + secp256k1::Verification>(
- &self, per_commitment_point: &PublicKey, secp: &Secp256k1<C>
- ) -> Script {
- let channel_params = self.channel_parameters.as_holder_broadcastable();
- let broadcaster_keys = channel_params.broadcaster_pubkeys();
- let counterparty_keys = channel_params.countersignatory_pubkeys();
- let broadcaster_htlc_key = chan_utils::derive_public_key(
- secp, per_commitment_point, &broadcaster_keys.htlc_basepoint
- );
- let counterparty_htlc_key = chan_utils::derive_public_key(
- secp, per_commitment_point, &counterparty_keys.htlc_basepoint
- );
- let counterparty_revocation_key = chan_utils::derive_public_revocation_key(
- secp, per_commitment_point, &counterparty_keys.revocation_basepoint
- );
- chan_utils::get_htlc_redeemscript_with_explicit_keys(
- &self.htlc, true /* opt_anchors */, &broadcaster_htlc_key, &counterparty_htlc_key,
- &counterparty_revocation_key,
- )
+ /// Returns the witness script of the anchor output in the commitment transaction.
+ pub fn witness_script(&self) -> ScriptBuf {
+ let channel_params = self.channel_derivation_parameters.transaction_parameters.as_holder_broadcastable();
+ chan_utils::get_anchor_redeemscript(&channel_params.broadcaster_pubkeys().funding_pubkey)
}
- /// Returns the fully signed witness required to spend the HTLC output in the commitment
+ /// Returns the fully signed witness required to spend the anchor output in the commitment
/// transaction.
- pub fn tx_input_witness(&self, signature: &Signature, witness_script: &Script) -> Witness {
- chan_utils::build_htlc_input_witness(
- signature, &self.counterparty_sig, &self.preimage, witness_script, true /* opt_anchors */
- )
+ pub fn tx_input_witness(&self, signature: &Signature) -> Witness {
+ let channel_params = self.channel_derivation_parameters.transaction_parameters.as_holder_broadcastable();
+ chan_utils::build_anchor_input_witness(&channel_params.broadcaster_pubkeys().funding_pubkey, signature)
+ }
+
+ /// Derives the channel signer required to sign the anchor input.
+ pub fn derive_channel_signer<S: WriteableEcdsaChannelSigner, SP: Deref>(&self, signer_provider: &SP) -> S
+ where
+ SP::Target: SignerProvider<EcdsaSigner= S>
+ {
+ let mut signer = signer_provider.derive_channel_signer(
+ self.channel_derivation_parameters.value_satoshis,
+ self.channel_derivation_parameters.keys_id,
+ );
+ signer.provide_channel_parameters(&self.channel_derivation_parameters.transaction_parameters);
+ signer
}
}
/// broadcast first, as the child anchor transaction depends on it.
///
/// The consumer should be able to sign for any of the additional inputs included within the
- /// child anchor transaction. To sign its anchor input, an [`InMemorySigner`] should be
- /// re-derived through [`KeysManager::derive_channel_keys`] with the help of
- /// [`AnchorDescriptor::channel_keys_id`] and [`AnchorDescriptor::channel_value_satoshis`]. The
- /// anchor input signature can be computed with [`EcdsaChannelSigner::sign_holder_anchor_input`],
- /// which can then be provided to [`build_anchor_input_witness`] along with the `funding_pubkey`
- /// to obtain the full witness required to spend.
+ /// child anchor transaction. To sign its anchor input, an [`EcdsaChannelSigner`] should be
+ /// re-derived through [`AnchorDescriptor::derive_channel_signer`]. The anchor input signature
+ /// can be computed with [`EcdsaChannelSigner::sign_holder_anchor_input`], which can then be
+ /// provided to [`build_anchor_input_witness`] along with the `funding_pubkey` to obtain the
+ /// full witness required to spend.
///
/// It is possible to receive more than one instance of this event if a valid child anchor
/// transaction is never broadcast or is but not with a sufficient fee to be mined. Care should
/// an empty `pending_htlcs`), confirmation of the commitment transaction can be considered to
/// be not urgent.
///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- /// [`KeysManager::derive_channel_keys`]: crate::sign::KeysManager::derive_channel_keys
- /// [`EcdsaChannelSigner::sign_holder_anchor_input`]: crate::sign::EcdsaChannelSigner::sign_holder_anchor_input
+ /// [`EcdsaChannelSigner`]: crate::sign::ecdsa::EcdsaChannelSigner
+ /// [`EcdsaChannelSigner::sign_holder_anchor_input`]: crate::sign::ecdsa::EcdsaChannelSigner::sign_holder_anchor_input
/// [`build_anchor_input_witness`]: crate::ln::chan_utils::build_anchor_input_witness
ChannelClose {
+ /// The unique identifier for the claim of the anchor output in the commitment transaction.
+ ///
+ /// The identifier must map to the set of external UTXOs assigned to the claim, such that
+ /// they can be reused when a new claim with the same identifier needs to be made, resulting
+ /// in a fee-bumping attempt.
+ claim_id: ClaimId,
/// The target feerate that the transaction package, which consists of the commitment
/// transaction and the to-be-crafted child anchor transaction, must meet.
package_target_feerate_sat_per_1000_weight: u32,
/// broadcast by the consumer of the event.
///
/// The consumer should be able to sign for any of the non-HTLC inputs added to the resulting
- /// HTLC transaction. To sign HTLC inputs, an [`InMemorySigner`] should be re-derived through
- /// [`KeysManager::derive_channel_keys`] with the help of `channel_keys_id` and
- /// `channel_value_satoshis`. Each HTLC input's signature can be computed with
- /// [`EcdsaChannelSigner::sign_holder_htlc_transaction`], which can then be provided to
- /// [`HTLCDescriptor::tx_input_witness`] to obtain the fully signed witness required to spend.
+ /// HTLC transaction. To sign HTLC inputs, an [`EcdsaChannelSigner`] should be re-derived
+ /// through [`HTLCDescriptor::derive_channel_signer`]. Each HTLC input's signature can be
+ /// computed with [`EcdsaChannelSigner::sign_holder_htlc_transaction`], which can then be
+ /// provided to [`HTLCDescriptor::tx_input_witness`] to obtain the fully signed witness required
+ /// to spend.
///
/// It is possible to receive more than one instance of this event if a valid HTLC transaction
/// is never broadcast or is but not with a sufficient fee to be mined. Care should be taken by
/// longer able to commit external confirmed funds to the HTLC transaction or the fee committed
/// to the HTLC transaction is greater in value than the HTLCs being claimed.
///
- /// [`InMemorySigner`]: crate::sign::InMemorySigner
- /// [`KeysManager::derive_channel_keys`]: crate::sign::KeysManager::derive_channel_keys
- /// [`EcdsaChannelSigner::sign_holder_htlc_transaction`]: crate::sign::EcdsaChannelSigner::sign_holder_htlc_transaction
- /// [`HTLCDescriptor::tx_input_witness`]: HTLCDescriptor::tx_input_witness
+ /// [`EcdsaChannelSigner`]: crate::sign::ecdsa::EcdsaChannelSigner
+ /// [`EcdsaChannelSigner::sign_holder_htlc_transaction`]: crate::sign::ecdsa::EcdsaChannelSigner::sign_holder_htlc_transaction
HTLCResolution {
+ /// The unique identifier for the claim of the HTLCs in the confirmed commitment
+ /// transaction.
+ ///
+ /// The identifier must map to the set of external UTXOs assigned to the claim, such that
+ /// they can be reused when a new claim with the same identifier needs to be made, resulting
+ /// in a fee-bumping attempt.
+ claim_id: ClaimId,
/// The target feerate that the resulting HTLC transaction must meet.
target_feerate_sat_per_1000_weight: u32,
/// The set of pending HTLCs on the confirmed commitment that need to be claimed, preferably
/// by the same transaction.
htlc_descriptors: Vec<HTLCDescriptor>,
/// The locktime required for the resulting HTLC transaction.
- tx_lock_time: PackedLockTime,
+ tx_lock_time: LockTime,
},
}
+
+/// An input that must be included in a transaction when performing coin selection through
+/// [`CoinSelectionSource::select_confirmed_utxos`]. It is guaranteed to be a SegWit input, so it
+/// must have an empty [`TxIn::script_sig`] when spent.
+#[derive(Clone, Debug, Hash, PartialOrd, Ord, PartialEq, Eq)]
+pub struct Input {
+ /// The unique identifier of the input.
+ pub outpoint: OutPoint,
+ /// The UTXO being spent by the input.
+ pub previous_utxo: TxOut,
+ /// The upper-bound weight consumed by the input's full [`TxIn::script_sig`] and
+ /// [`TxIn::witness`], each with their lengths included, required to satisfy the output's
+ /// script.
+ pub satisfaction_weight: u64,
+}
+
+/// An unspent transaction output that is available to spend resulting from a successful
+/// [`CoinSelection`] attempt.
+#[derive(Clone, Debug, Hash, PartialOrd, Ord, PartialEq, Eq)]
+pub struct Utxo {
+ /// The unique identifier of the output.
+ pub outpoint: OutPoint,
+ /// The output to spend.
+ pub output: TxOut,
+ /// The upper-bound weight consumed by the input's full [`TxIn::script_sig`] and [`TxIn::witness`], each
+ /// 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,
+}
+
+impl Utxo {
+ /// Returns a `Utxo` with the `satisfaction_weight` estimate for a legacy P2PKH output.
+ pub fn new_p2pkh(outpoint: OutPoint, value: u64, pubkey_hash: &PubkeyHash) -> Self {
+ let script_sig_size = 1 /* script_sig length */ +
+ 1 /* OP_PUSH73 */ +
+ 73 /* sig including sighash flag */ +
+ 1 /* OP_PUSH33 */ +
+ 33 /* pubkey */;
+ Self {
+ outpoint,
+ output: TxOut {
+ value,
+ script_pubkey: ScriptBuf::new_p2pkh(pubkey_hash),
+ },
+ satisfaction_weight: script_sig_size * WITNESS_SCALE_FACTOR as u64 + 1 /* empty witness */,
+ }
+ }
+
+ /// Returns a `Utxo` with the `satisfaction_weight` estimate for a P2WPKH nested in P2SH output.
+ pub fn new_nested_p2wpkh(outpoint: OutPoint, value: u64, pubkey_hash: &WPubkeyHash) -> Self {
+ let script_sig_size = 1 /* script_sig length */ +
+ 1 /* OP_0 */ +
+ 1 /* OP_PUSH20 */ +
+ 20 /* pubkey_hash */;
+ Self {
+ outpoint,
+ output: TxOut {
+ value,
+ script_pubkey: ScriptBuf::new_p2sh(&ScriptBuf::new_v0_p2wpkh(pubkey_hash).script_hash()),
+ },
+ satisfaction_weight: script_sig_size * WITNESS_SCALE_FACTOR as u64 + P2WPKH_WITNESS_WEIGHT,
+ }
+ }
+
+ /// Returns a `Utxo` with the `satisfaction_weight` estimate for a SegWit v0 P2WPKH output.
+ pub fn new_v0_p2wpkh(outpoint: OutPoint, value: u64, pubkey_hash: &WPubkeyHash) -> Self {
+ Self {
+ outpoint,
+ output: TxOut {
+ value,
+ script_pubkey: ScriptBuf::new_v0_p2wpkh(pubkey_hash),
+ },
+ satisfaction_weight: EMPTY_SCRIPT_SIG_WEIGHT + P2WPKH_WITNESS_WEIGHT,
+ }
+ }
+}
+
+/// The result of a successful coin selection attempt for a transaction requiring additional UTXOs
+/// to cover its fees.
+#[derive(Clone, Debug)]
+pub struct CoinSelection {
+ /// The set of UTXOs (with at least 1 confirmation) to spend and use within a transaction
+ /// requiring additional fees.
+ pub confirmed_utxos: Vec<Utxo>,
+ /// An additional output tracking whether any change remained after coin selection. This output
+ /// should always have a value above dust for its given `script_pubkey`. It should not be
+ /// spent until the transaction it belongs to confirms to ensure mempool descendant limits are
+ /// not met. This implies no other party should be able to spend it except us.
+ pub change_output: Option<TxOut>,
+}
+
+/// 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. 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
+ /// choice, as long as the following requirements are met:
+ ///
+ /// 1. `must_spend` contains a set of [`Input`]s that must be included in the transaction
+ /// throughout coin selection, but must not be returned as part of the result.
+ /// 2. `must_pay_to` contains a set of [`TxOut`]s that must be included in the transaction
+ /// throughout coin selection. In some cases, like when funding an anchor transaction, this
+ /// set is empty. Implementations should ensure they handle this correctly on their end,
+ /// e.g., Bitcoin Core's `fundrawtransaction` RPC requires at least one output to be
+ /// provided, in which case a zero-value empty OP_RETURN output can be used instead.
+ /// 3. Enough inputs must be selected/contributed for the resulting transaction (including the
+ /// inputs and outputs noted above) to meet `target_feerate_sat_per_1000_weight`.
+ ///
+ /// Implementations must take note that [`Input::satisfaction_weight`] only tracks the weight of
+ /// the input's `script_sig` and `witness`. Some wallets, like Bitcoin Core's, may require
+ /// providing the full input weight. Failing to do so may lead to underestimating fee bumps and
+ /// delaying block inclusion.
+ ///
+ /// The `claim_id` must map to the set of external UTXOs assigned to the claim, such that they
+ /// can be re-used within new fee-bumped iterations of the original claiming transaction,
+ /// ensuring that claims don't double spend each other. If a specific `claim_id` has never had a
+ /// transaction associated with it, and all of the available UTXOs have already been assigned to
+ /// other claims, implementations must be willing to double spend their UTXOs. The choice of
+ /// which UTXOs to double spend is left to the implementation, but it must strive to keep the
+ /// set of other claims being double spent to a minimum.
+ fn select_confirmed_utxos(
+ &self, claim_id: ClaimId, must_spend: Vec<Input>, must_pay_to: &[TxOut],
+ target_feerate_sat_per_1000_weight: u32,
+ ) -> Result<CoinSelection, ()>;
+ /// Signs and provides the full witness for all inputs within the transaction known to the
+ /// trait (i.e., any provided via [`CoinSelectionSource::select_confirmed_utxos`]).
+ ///
+ /// If your wallet does not support signing PSBTs you can call `psbt.extract_tx()` to get the
+ /// unsigned transaction and then sign it with your wallet.
+ fn sign_psbt(&self, psbt: PartiallySignedTransaction) -> Result<Transaction, ()>;
+}
+
+/// 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<ScriptBuf, ()>;
+ /// 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`]).
+ ///
+ /// If your wallet does not support signing PSBTs you can call `psbt.extract_tx()` to get the
+ /// unsigned transaction and then sign it with your wallet.
+ fn sign_psbt(&self, psbt: PartiallySignedTransaction) -> Result<Transaction, ()>;
+}
+
+/// 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, L: Deref>
+where
+ W::Target: WalletSource,
+ L::Target: Logger
+{
+ source: W,
+ logger: L,
+ // 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, L: Deref> Wallet<W, L>
+where
+ W::Target: WalletSource,
+ L::Target: Logger
+{
+ /// Returns a new instance backed by the given [`WalletSource`] that serves as an implementation
+ /// of [`CoinSelectionSource`].
+ pub fn new(source: W, logger: L) -> Self {
+ Self { source, logger, 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, input_amount_sat: 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 {
+ log_trace!(self.logger, "Skipping UTXO {} to prevent conflicting spend", utxo.outpoint);
+ return None;
+ }
+ }
+ let fee_to_spend_utxo = fee_for_weight(
+ target_feerate_sat_per_1000_weight, BASE_INPUT_WEIGHT + 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 {
+ log_trace!(self.logger, "Skipping UTXO {} due to dust proximity after spend", utxo.outpoint);
+ None
+ }
+ }).collect::<Vec<_>>();
+ eligible_utxos.sort_unstable_by_key(|(utxo, _)| utxo.output.value);
+
+ let mut selected_amount = input_amount_sat;
+ 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 {
+ log_debug!(self.logger, "Insufficient funds to meet target feerate {} sat/kW",
+ target_feerate_sat_per_1000_weight);
+ 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() {
+ log_debug!(self.logger, "Coin selection attempt did not yield change output");
+ None
+ } else {
+ Some(TxOut { script_pubkey: change_script, value: change_output_amount })
+ };
+
+ Ok(CoinSelection {
+ confirmed_utxos: selected_utxos,
+ change_output,
+ })
+ }
+}
+
+impl<W: Deref, L: Deref> CoinSelectionSource for Wallet<W, L>
+where
+ W::Target: WalletSource,
+ L::Target: Logger
+{
+ fn select_confirmed_utxos(
+ &self, claim_id: ClaimId, must_spend: Vec<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 input_amount_sat: u64 = must_spend.iter().map(|input| input.previous_utxo.value).sum();
+ 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| {
+ log_debug!(self.logger, "Attempting coin selection targeting {} sat/kW (force_conflicting_utxo_spend = {}, tolerate_high_network_feerates = {})",
+ target_feerate_sat_per_1000_weight, force_conflicting_utxo_spend, tolerate_high_network_feerates);
+ 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, input_amount_sat, 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_psbt(&self, psbt: PartiallySignedTransaction) -> Result<Transaction, ()> {
+ self.source.sign_psbt(psbt)
+ }
+}
+
+/// 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).
+///
+/// [`Event::BumpTransaction`]: crate::events::Event::BumpTransaction
+pub struct BumpTransactionEventHandler<B: Deref, C: Deref, SP: Deref, L: Deref>
+where
+ B::Target: BroadcasterInterface,
+ C::Target: CoinSelectionSource,
+ SP::Target: SignerProvider,
+ L::Target: Logger,
+{
+ broadcaster: B,
+ utxo_source: C,
+ signer_provider: SP,
+ logger: L,
+ secp: Secp256k1<secp256k1::All>,
+}
+
+impl<B: Deref, C: Deref, SP: Deref, L: Deref> BumpTransactionEventHandler<B, C, SP, L>
+where
+ B::Target: BroadcasterInterface,
+ C::Target: CoinSelectionSource,
+ SP::Target: SignerProvider,
+ L::Target: Logger,
+{
+ /// Returns a new instance capable of handling [`Event::BumpTransaction`] events.
+ ///
+ /// [`Event::BumpTransaction`]: crate::events::Event::BumpTransaction
+ pub fn new(broadcaster: B, utxo_source: C, signer_provider: SP, logger: L) -> Self {
+ Self {
+ broadcaster,
+ utxo_source,
+ signer_provider,
+ logger,
+ secp: Secp256k1::new(),
+ }
+ }
+
+ /// Updates a transaction with the result of a successful coin selection attempt.
+ fn process_coin_selection(&self, tx: &mut Transaction, coin_selection: &CoinSelection) {
+ for utxo in coin_selection.confirmed_utxos.iter() {
+ tx.input.push(TxIn {
+ previous_output: utxo.outpoint,
+ script_sig: ScriptBuf::new(),
+ sequence: Sequence::ZERO,
+ witness: Witness::new(),
+ });
+ }
+ if let Some(change_output) = coin_selection.change_output.clone() {
+ tx.output.push(change_output);
+ } else if tx.output.is_empty() {
+ // We weren't provided a change output, likely because the input set was a perfect
+ // match, but we still need to have at least one output in the transaction for it to be
+ // considered standard. We choose to go with an empty OP_RETURN as it is the cheapest
+ // way to include a dummy output.
+ log_debug!(self.logger, "Including dummy OP_RETURN output since an output is needed and a change output was not provided");
+ tx.output.push(TxOut {
+ value: 0,
+ script_pubkey: ScriptBuf::new_op_return(&[]),
+ });
+ }
+ }
+
+ /// Handles a [`BumpTransactionEvent::ChannelClose`] event variant by producing a fully-signed
+ /// transaction spending an anchor output of the commitment transaction to bump its fee and
+ /// broadcasts them to the network as a package.
+ fn handle_channel_close(
+ &self, claim_id: ClaimId, package_target_feerate_sat_per_1000_weight: u32,
+ commitment_tx: &Transaction, commitment_tx_fee_sat: u64, anchor_descriptor: &AnchorDescriptor,
+ ) -> Result<(), ()> {
+ // Our commitment transaction already has fees allocated to it, so we should take them into
+ // account. We do so by pretending the commitment tranasction's fee and weight are part of
+ // the anchor input.
+ let mut anchor_utxo = anchor_descriptor.previous_utxo();
+ anchor_utxo.value += commitment_tx_fee_sat;
+ let must_spend = vec![Input {
+ outpoint: anchor_descriptor.outpoint,
+ previous_utxo: anchor_utxo,
+ satisfaction_weight: commitment_tx.weight().to_wu() + ANCHOR_INPUT_WITNESS_WEIGHT + EMPTY_SCRIPT_SIG_WEIGHT,
+ }];
+ #[cfg(debug_assertions)]
+ let must_spend_amount = must_spend.iter().map(|input| input.previous_utxo.value).sum::<u64>();
+
+ log_debug!(self.logger, "Peforming coin selection for commitment package (commitment and anchor transaction) targeting {} sat/kW",
+ package_target_feerate_sat_per_1000_weight);
+ let coin_selection: CoinSelection = self.utxo_source.select_confirmed_utxos(
+ claim_id, must_spend, &[], package_target_feerate_sat_per_1000_weight,
+ )?;
+
+ let mut anchor_tx = Transaction {
+ version: 2,
+ lock_time: LockTime::ZERO, // TODO: Use next best height.
+ input: vec![anchor_descriptor.unsigned_tx_input()],
+ output: vec![],
+ };
+
+ #[cfg(debug_assertions)]
+ let total_satisfaction_weight = ANCHOR_INPUT_WITNESS_WEIGHT + EMPTY_SCRIPT_SIG_WEIGHT +
+ coin_selection.confirmed_utxos.iter().map(|utxo| utxo.satisfaction_weight).sum::<u64>();
+ #[cfg(debug_assertions)]
+ let total_input_amount = must_spend_amount +
+ coin_selection.confirmed_utxos.iter().map(|utxo| utxo.output.value).sum::<u64>();
+
+ self.process_coin_selection(&mut anchor_tx, &coin_selection);
+ let anchor_txid = anchor_tx.txid();
+
+ // construct psbt
+ let mut anchor_psbt = PartiallySignedTransaction::from_unsigned_tx(anchor_tx).unwrap();
+ // add witness_utxo to anchor input
+ anchor_psbt.inputs[0].witness_utxo = Some(anchor_descriptor.previous_utxo());
+ // add witness_utxo to remaining inputs
+ for (idx, utxo) in coin_selection.confirmed_utxos.into_iter().enumerate() {
+ // add 1 to skip the anchor input
+ let index = idx + 1;
+ debug_assert_eq!(anchor_psbt.unsigned_tx.input[index].previous_output, utxo.outpoint);
+ if utxo.output.script_pubkey.is_witness_program() {
+ anchor_psbt.inputs[index].witness_utxo = Some(utxo.output);
+ }
+ }
+
+ debug_assert_eq!(anchor_psbt.unsigned_tx.output.len(), 1);
+ #[cfg(debug_assertions)]
+ let unsigned_tx_weight = anchor_psbt.unsigned_tx.weight().to_wu() - (anchor_psbt.unsigned_tx.input.len() as u64 * EMPTY_SCRIPT_SIG_WEIGHT);
+
+ log_debug!(self.logger, "Signing anchor transaction {}", anchor_txid);
+ anchor_tx = self.utxo_source.sign_psbt(anchor_psbt)?;
+
+ let signer = anchor_descriptor.derive_channel_signer(&self.signer_provider);
+ let anchor_sig = signer.sign_holder_anchor_input(&anchor_tx, 0, &self.secp)?;
+ anchor_tx.input[0].witness = anchor_descriptor.tx_input_witness(&anchor_sig);
+
+ #[cfg(debug_assertions)] {
+ let signed_tx_weight = anchor_tx.weight().to_wu();
+ let expected_signed_tx_weight = unsigned_tx_weight + total_satisfaction_weight;
+ // Our estimate should be within a 1% error margin of the actual weight and we should
+ // never underestimate.
+ assert!(expected_signed_tx_weight >= signed_tx_weight &&
+ expected_signed_tx_weight - (expected_signed_tx_weight / 100) <= signed_tx_weight);
+
+ let expected_package_fee = fee_for_weight(package_target_feerate_sat_per_1000_weight,
+ signed_tx_weight + commitment_tx.weight().to_wu());
+ let package_fee = total_input_amount -
+ anchor_tx.output.iter().map(|output| output.value).sum::<u64>();
+ // Our fee should be within a 5% error margin of the expected fee based on the
+ // feerate and transaction weight and we should never pay less than required.
+ let fee_error_margin = expected_package_fee * 5 / 100;
+ assert!(package_fee >= expected_package_fee &&
+ package_fee - fee_error_margin <= expected_package_fee);
+ }
+
+ log_info!(self.logger, "Broadcasting anchor transaction {} to bump channel close with txid {}",
+ anchor_txid, commitment_tx.txid());
+ self.broadcaster.broadcast_transactions(&[&commitment_tx, &anchor_tx]);
+ Ok(())
+ }
+
+ /// Handles a [`BumpTransactionEvent::HTLCResolution`] event variant by producing a
+ /// fully-signed, fee-bumped HTLC transaction that is broadcast to the network.
+ fn handle_htlc_resolution(
+ &self, claim_id: ClaimId, target_feerate_sat_per_1000_weight: u32,
+ htlc_descriptors: &[HTLCDescriptor], tx_lock_time: LockTime,
+ ) -> Result<(), ()> {
+ let mut htlc_tx = Transaction {
+ version: 2,
+ lock_time: tx_lock_time,
+ input: vec![],
+ output: vec![],
+ };
+ let mut must_spend = Vec::with_capacity(htlc_descriptors.len());
+ for htlc_descriptor in htlc_descriptors {
+ let htlc_input = htlc_descriptor.unsigned_tx_input();
+ must_spend.push(Input {
+ outpoint: htlc_input.previous_output.clone(),
+ previous_utxo: htlc_descriptor.previous_utxo(&self.secp),
+ satisfaction_weight: EMPTY_SCRIPT_SIG_WEIGHT + if htlc_descriptor.preimage.is_some() {
+ HTLC_SUCCESS_INPUT_ANCHOR_WITNESS_WEIGHT
+ } else {
+ HTLC_TIMEOUT_INPUT_ANCHOR_WITNESS_WEIGHT
+ },
+ });
+ htlc_tx.input.push(htlc_input);
+ let htlc_output = htlc_descriptor.tx_output(&self.secp);
+ htlc_tx.output.push(htlc_output);
+ }
+
+ log_debug!(self.logger, "Peforming coin selection for HTLC transaction targeting {} sat/kW",
+ target_feerate_sat_per_1000_weight);
+
+ #[cfg(debug_assertions)]
+ let must_spend_satisfaction_weight =
+ must_spend.iter().map(|input| input.satisfaction_weight).sum::<u64>();
+ #[cfg(debug_assertions)]
+ let must_spend_amount = must_spend.iter().map(|input| input.previous_utxo.value).sum::<u64>();
+
+ let coin_selection: CoinSelection = self.utxo_source.select_confirmed_utxos(
+ claim_id, must_spend, &htlc_tx.output, target_feerate_sat_per_1000_weight,
+ )?;
+
+ #[cfg(debug_assertions)]
+ let total_satisfaction_weight = must_spend_satisfaction_weight +
+ coin_selection.confirmed_utxos.iter().map(|utxo| utxo.satisfaction_weight).sum::<u64>();
+ #[cfg(debug_assertions)]
+ let total_input_amount = must_spend_amount +
+ coin_selection.confirmed_utxos.iter().map(|utxo| utxo.output.value).sum::<u64>();
+
+ self.process_coin_selection(&mut htlc_tx, &coin_selection);
+
+ // construct psbt
+ let mut htlc_psbt = PartiallySignedTransaction::from_unsigned_tx(htlc_tx).unwrap();
+ // add witness_utxo to htlc inputs
+ for (i, htlc_descriptor) in htlc_descriptors.iter().enumerate() {
+ debug_assert_eq!(htlc_psbt.unsigned_tx.input[i].previous_output, htlc_descriptor.outpoint());
+ htlc_psbt.inputs[i].witness_utxo = Some(htlc_descriptor.previous_utxo(&self.secp));
+ }
+ // add witness_utxo to remaining inputs
+ for (idx, utxo) in coin_selection.confirmed_utxos.into_iter().enumerate() {
+ // offset to skip the htlc inputs
+ let index = idx + htlc_descriptors.len();
+ debug_assert_eq!(htlc_psbt.unsigned_tx.input[index].previous_output, utxo.outpoint);
+ if utxo.output.script_pubkey.is_witness_program() {
+ htlc_psbt.inputs[index].witness_utxo = Some(utxo.output);
+ }
+ }
+
+ #[cfg(debug_assertions)]
+ let unsigned_tx_weight = htlc_psbt.unsigned_tx.weight().to_wu() - (htlc_psbt.unsigned_tx.input.len() as u64 * EMPTY_SCRIPT_SIG_WEIGHT);
+
+ log_debug!(self.logger, "Signing HTLC transaction {}", htlc_psbt.unsigned_tx.txid());
+ htlc_tx = self.utxo_source.sign_psbt(htlc_psbt)?;
+
+ let mut signers = BTreeMap::new();
+ for (idx, htlc_descriptor) in htlc_descriptors.iter().enumerate() {
+ let signer = signers.entry(htlc_descriptor.channel_derivation_parameters.keys_id)
+ .or_insert_with(|| htlc_descriptor.derive_channel_signer(&self.signer_provider));
+ let htlc_sig = signer.sign_holder_htlc_transaction(&htlc_tx, idx, htlc_descriptor, &self.secp)?;
+ let witness_script = htlc_descriptor.witness_script(&self.secp);
+ htlc_tx.input[idx].witness = htlc_descriptor.tx_input_witness(&htlc_sig, &witness_script);
+ }
+
+ #[cfg(debug_assertions)] {
+ let signed_tx_weight = htlc_tx.weight().to_wu();
+ let expected_signed_tx_weight = unsigned_tx_weight + total_satisfaction_weight;
+ // Our estimate should be within a 1% error margin of the actual weight and we should
+ // never underestimate.
+ assert!(expected_signed_tx_weight >= signed_tx_weight &&
+ expected_signed_tx_weight - (expected_signed_tx_weight / 100) <= signed_tx_weight);
+
+ let expected_signed_tx_fee = fee_for_weight(target_feerate_sat_per_1000_weight, signed_tx_weight);
+ let signed_tx_fee = total_input_amount -
+ htlc_tx.output.iter().map(|output| output.value).sum::<u64>();
+ // Our fee should be within a 5% error margin of the expected fee based on the
+ // feerate and transaction weight and we should never pay less than required.
+ let fee_error_margin = expected_signed_tx_fee * 5 / 100;
+ assert!(signed_tx_fee >= expected_signed_tx_fee &&
+ signed_tx_fee - fee_error_margin <= expected_signed_tx_fee);
+ }
+
+ log_info!(self.logger, "Broadcasting {}", log_tx!(htlc_tx));
+ self.broadcaster.broadcast_transactions(&[&htlc_tx]);
+ Ok(())
+ }
+
+ /// Handles all variants of [`BumpTransactionEvent`].
+ pub fn handle_event(&self, event: &BumpTransactionEvent) {
+ match event {
+ BumpTransactionEvent::ChannelClose {
+ claim_id, package_target_feerate_sat_per_1000_weight, commitment_tx,
+ commitment_tx_fee_satoshis, anchor_descriptor, ..
+ } => {
+ log_info!(self.logger, "Handling channel close bump (claim_id = {}, commitment_txid = {})",
+ log_bytes!(claim_id.0), commitment_tx.txid());
+ if let Err(_) = self.handle_channel_close(
+ *claim_id, *package_target_feerate_sat_per_1000_weight, commitment_tx,
+ *commitment_tx_fee_satoshis, anchor_descriptor,
+ ) {
+ log_error!(self.logger, "Failed bumping commitment transaction fee for {}",
+ commitment_tx.txid());
+ }
+ }
+ BumpTransactionEvent::HTLCResolution {
+ claim_id, target_feerate_sat_per_1000_weight, htlc_descriptors, tx_lock_time,
+ } => {
+ log_info!(self.logger, "Handling HTLC bump (claim_id = {}, htlcs_to_claim = {})",
+ log_bytes!(claim_id.0), log_iter!(htlc_descriptors.iter().map(|d| d.outpoint())));
+ if let Err(_) = self.handle_htlc_resolution(
+ *claim_id, *target_feerate_sat_per_1000_weight, htlc_descriptors, *tx_lock_time,
+ ) {
+ log_error!(self.logger, "Failed bumping HTLC transaction fee for commitment {}",
+ htlc_descriptors[0].commitment_txid);
+ }
+ }
+ }
+ }
+}
projects / rust-lightning / blobdiff