Implement Holder HTLC claim chunking for 0FC channels

Otherwise, we could hit the max 10_000vB size limit on V3 transactions
(BIP 431 rule 4).

Also introduce a `max_tx_weight` parameter to `select_confirmed_utxos`.
This constraint makes sure anchor and HTLC transactions in 0FC channels
satisfy the `TRUC_MAX_WEIGHT` and the `TRUC_CHILD_MAX_WEIGHT`
maximums.

Expand the coin-selection algorithm provided for any `T: WalletSource`
to satisfy this new constraint.

Author: tankyleo

lightning/src/chain/mod.rs

@@ -12,6 +12,8 @@
 use bitcoin::block::{Block, Header};
 use bitcoin::constants::genesis_block;
 use bitcoin::hash_types::{BlockHash, Txid};
+use bitcoin::hashes::sha256::Hash as Sha256;
+use bitcoin::hashes::{Hash, HashEngine};
 use bitcoin::network::Network;
 use bitcoin::script::{Script, ScriptBuf};
 use bitcoin::secp256k1::PublicKey;
@@ -21,6 +23,7 @@ use crate::chain::transaction::{OutPoint, TransactionData};
 use crate::impl_writeable_tlv_based;
 use crate::ln::types::ChannelId;
 use crate::sign::ecdsa::EcdsaChannelSigner;
+use crate::sign::HTLCDescriptor;
 
 #[allow(unused_imports)]
 use crate::prelude::*;
@@ -442,3 +445,20 @@ where
 /// This is not exported to bindings users as we just use [u8; 32] directly.
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub struct ClaimId(pub [u8; 32]);
+
+impl ClaimId {
+	pub(crate) fn from_htlcs(htlcs: &[HTLCDescriptor]) -> ClaimId {
+		let mut engine = Sha256::engine();
+		for htlc in htlcs {
+			engine.input(&htlc.commitment_txid.to_byte_array());
+			engine.input(&htlc.htlc.transaction_output_index.unwrap().to_be_bytes());
+		}
+		ClaimId(Sha256::from_engine(engine).to_byte_array())
+	}
+	pub(crate) fn step_with_bytes(&self, bytes: &[u8]) -> ClaimId {
+		let mut engine = Sha256::engine();
+		engine.input(&self.0);
+		engine.input(bytes);
+		ClaimId(Sha256::from_engine(engine).to_byte_array())
+	}
+}

lightning/src/chain/onchaintx.rs

@@ -14,8 +14,7 @@
 
 use bitcoin::amount::Amount;
 use bitcoin::hash_types::{BlockHash, Txid};
-use bitcoin::hashes::sha256::Hash as Sha256;
-use bitcoin::hashes::{Hash, HashEngine};
+use bitcoin::hashes::Hash;
 use bitcoin::locktime::absolute::LockTime;
 use bitcoin::script::{Script, ScriptBuf};
 use bitcoin::secp256k1;
@@ -882,12 +881,7 @@ impl<ChannelSigner: EcdsaChannelSigner> OnchainTxHandler<ChannelSigner> {
 								// claim, which will always be unique per request. Once a claim ID
 								// is generated, it is assigned and remains unchanged, even if the
 								// underlying set of HTLCs changes.
-								let mut engine = Sha256::engine();
-								for htlc in htlcs {
-									engine.input(&htlc.commitment_txid.to_byte_array());
-									engine.input(&htlc.htlc.transaction_output_index.unwrap().to_be_bytes());
-								}
-								ClaimId(Sha256::from_engine(engine).to_byte_array())
+								ClaimId::from_htlcs(htlcs)
 							},
 						};
 						debug_assert!(self.pending_claim_requests.get(&claim_id).is_none());

lightning/src/events/bump_transaction/mod.rs

@@ -102,13 +102,14 @@ where
 {
 	fn select_confirmed_utxos(
 		&self, claim_id: ClaimId, must_spend: Vec<Input>, must_pay_to: &[TxOut],
-		target_feerate_sat_per_1000_weight: u32,
+		target_feerate_sat_per_1000_weight: u32, max_tx_weight: u64,
 	) -> Result<CoinSelection, ()> {
 		let mut fut = self.wallet.select_confirmed_utxos(
 			claim_id,
 			must_spend,
 			must_pay_to,
 			target_feerate_sat_per_1000_weight,
+			max_tx_weight,
 		);
 		let mut waker = dummy_waker();
 		let mut ctx = task::Context::from_waker(&mut waker);
@@ -140,7 +141,7 @@ pub trait CoinSelectionSourceSync {
 	/// A synchronous version of [`CoinSelectionSource::select_confirmed_utxos`].
 	fn select_confirmed_utxos(
 		&self, claim_id: ClaimId, must_spend: Vec<Input>, must_pay_to: &[TxOut],
-		target_feerate_sat_per_1000_weight: u32,
+		target_feerate_sat_per_1000_weight: u32, max_tx_weight: u64,
 	) -> Result<CoinSelection, ()>;
 
 	/// A synchronous version of [`CoinSelectionSource::sign_psbt`].
@@ -169,13 +170,14 @@ where
 {
 	fn select_confirmed_utxos<'a>(
 		&'a self, claim_id: ClaimId, must_spend: Vec<Input>, must_pay_to: &'a [TxOut],
-		target_feerate_sat_per_1000_weight: u32,
+		target_feerate_sat_per_1000_weight: u32, max_tx_weight: u64,
 	) -> AsyncResult<'a, CoinSelection> {
 		let coins = self.0.select_confirmed_utxos(
 			claim_id,
 			must_spend,
 			must_pay_to,
 			target_feerate_sat_per_1000_weight,
+			max_tx_weight,
 		);
 		Box::pin(async move { coins })
 	}

lightning/src/events/bump_transaction/sync.rs

@@ -1604,15 +1604,18 @@ pub enum Event {
 	/// Indicates that a transaction originating from LDK needs to have its fee bumped. This event
 	/// requires confirmed external funds to be readily available to spend.
 	///
-	/// LDK does not currently generate this event unless the
-	/// [`ChannelHandshakeConfig::negotiate_anchors_zero_fee_htlc_tx`] config flag is set to true.
+	/// LDK does not currently generate this event unless either the
+	/// [`ChannelHandshakeConfig::negotiate_anchors_zero_fee_htlc_tx`] or the
+	/// [`ChannelHandshakeConfig::negotiate_anchor_zero_fee_commitments`] config flags are set to
+	/// true.
 	/// It is limited to the scope of channels with anchor outputs.
 	///
 	/// # Failure Behavior and Persistence
 	/// This event will eventually be replayed after failures-to-handle (i.e., the event handler
 	/// returning `Err(ReplayEvent ())`), but will only be regenerated as needed after restarts.
 	///
 	/// [`ChannelHandshakeConfig::negotiate_anchors_zero_fee_htlc_tx`]: crate::util::config::ChannelHandshakeConfig::negotiate_anchors_zero_fee_htlc_tx
+	/// [`ChannelHandshakeConfig::negotiate_anchor_zero_fee_commitments`]: crate::util::config::ChannelHandshakeConfig::negotiate_anchor_zero_fee_commitments
 	BumpTransaction(BumpTransactionEvent),
 	/// We received an onion message that is intended to be forwarded to a peer
 	/// that is currently offline. This event will only be generated if the

lightning/src/events/mod.rs

@@ -11,6 +11,7 @@
 //! largely of interest for those implementing the traits on [`crate::sign`] by hand.
 
 use bitcoin::amount::Amount;
+use bitcoin::constants::WITNESS_SCALE_FACTOR;
 use bitcoin::opcodes;
 use bitcoin::script::{Builder, Script, ScriptBuf};
 use bitcoin::sighash;
@@ -89,12 +90,18 @@ pub const ANCHOR_INPUT_WITNESS_WEIGHT: u64 = 114;
 #[cfg(not(feature = "grind_signatures"))]
 pub const ANCHOR_INPUT_WITNESS_WEIGHT: u64 = 115;
 
-/// The weight of a P2A anchor witness.
-pub const P2A_ANCHOR_INPUT_WITNESS_WEIGHT: u64 = 1;
+/// The weight of an empty witness; used to spend a P2A output.
+pub const EMPTY_WITNESS_WEIGHT: u64 = 1;
 
 /// The maximum value of a P2A anchor.
 pub const P2A_MAX_VALUE: u64 = 240;
 
+/// The maximum weight of a TRUC transaction, see BIP431.
+pub const TRUC_MAX_WEIGHT: u64 = 10_000 * WITNESS_SCALE_FACTOR as u64;
+
+/// The maximum weight of a TRUC transaction with an unconfirmed TRUC ancestor, see BIP431.
+pub const TRUC_CHILD_MAX_WEIGHT: u64 = 1000 * WITNESS_SCALE_FACTOR as u64;
+
 /// The upper bound weight of an HTLC timeout input from a commitment transaction with keyed anchor outputs.
 pub const HTLC_TIMEOUT_INPUT_KEYED_ANCHOR_WITNESS_WEIGHT: u64 = 288;
 /// The upper bound weight of an HTLC timeout input from a commitment transaction with a p2a anchor output.
@@ -125,6 +132,15 @@ pub const FUNDING_TRANSACTION_WITNESS_WEIGHT: u64 = 1 + // number_of_witness_ele
 	1 + // witness_script_length
 	MULTISIG_SCRIPT_SIZE;
 
+pub(crate) const BASE_TX_SIZE: u64 = 4 /* version */ + 1 /* input count */ + 1 /* output count */ + 4 /* locktime */;
+pub(crate) const SEGWIT_MARKER_FLAG_WEIGHT: u64 = 2;
+pub(crate) const EMPTY_SCRIPT_SIG_WEIGHT: u64 =
+	1 /* empty script_sig */ * WITNESS_SCALE_FACTOR as u64;
+pub(crate) const BASE_INPUT_SIZE: u64 = 32 /* txid */ + 4 /* vout */ + 4 /* sequence */;
+pub(crate) const BASE_INPUT_WEIGHT: u64 = BASE_INPUT_SIZE * WITNESS_SCALE_FACTOR as u64;
+pub(crate) const P2WSH_TXOUT_WEIGHT: u64 =
+	(8 /* value */ + 1 /* var_int */ + 34/* p2wsh spk */) * WITNESS_SCALE_FACTOR as u64;
+
 /// Gets the weight for an HTLC-Success transaction.
 #[inline]
 #[rustfmt::skip]
@@ -134,6 +150,18 @@ pub fn htlc_success_tx_weight(channel_type_features: &ChannelTypeFeatures) -> u6
 	if channel_type_features.supports_anchors_zero_fee_htlc_tx() { HTLC_SUCCESS_ANCHOR_TX_WEIGHT } else { HTLC_SUCCESS_TX_WEIGHT }
 }
 
+/// Gets the weight of a single input-output pair in externally funded HTLC-success transactions
+pub fn aggregated_htlc_success_input_output_pair_weight(
+	channel_type_features: &ChannelTypeFeatures,
+) -> u64 {
+	let satisfaction_weight = if channel_type_features.supports_anchors_zero_fee_htlc_tx() {
+		EMPTY_SCRIPT_SIG_WEIGHT + HTLC_SUCCESS_INPUT_KEYED_ANCHOR_WITNESS_WEIGHT
+	} else {
+		EMPTY_SCRIPT_SIG_WEIGHT + HTLC_SUCCESS_INPUT_P2A_ANCHOR_WITNESS_WEIGHT
+	};
+	BASE_INPUT_WEIGHT + P2WSH_TXOUT_WEIGHT + satisfaction_weight
+}
+
 /// Gets the weight for an HTLC-Timeout transaction.
 #[inline]
 #[rustfmt::skip]
@@ -143,6 +171,18 @@ pub fn htlc_timeout_tx_weight(channel_type_features: &ChannelTypeFeatures) -> u6
 	if channel_type_features.supports_anchors_zero_fee_htlc_tx() { HTLC_TIMEOUT_ANCHOR_TX_WEIGHT } else { HTLC_TIMEOUT_TX_WEIGHT }
 }
 
+/// Gets the weight of a single input-output pair in externally funded HTLC-timeout transactions
+pub fn aggregated_htlc_timeout_input_output_pair_weight(
+	channel_type_features: &ChannelTypeFeatures,
+) -> u64 {
+	let satisfaction_weight = if channel_type_features.supports_anchors_zero_fee_htlc_tx() {
+		EMPTY_SCRIPT_SIG_WEIGHT + HTLC_TIMEOUT_INPUT_KEYED_ANCHOR_WITNESS_WEIGHT
+	} else {
+		EMPTY_SCRIPT_SIG_WEIGHT + HTLC_TIMEOUT_INPUT_P2A_ANCHOR_WITNESS_WEIGHT
+	};
+	BASE_INPUT_WEIGHT + P2WSH_TXOUT_WEIGHT + satisfaction_weight
+}
+
 /// Describes the type of HTLC claim as determined by analyzing the witness.
 #[derive(PartialEq, Eq)]
 pub enum HTLCClaim {

lightning/src/ln/chan_utils.rs

@@ -36,15 +36,14 @@ use crate::chain::channelmonitor::{
 };
 use crate::chain::transaction::{OutPoint, TransactionData};
 use crate::chain::BestBlock;
-use crate::events::bump_transaction::{BASE_INPUT_WEIGHT, EMPTY_SCRIPT_SIG_WEIGHT};
 use crate::events::{ClosureReason, FundingInfo};
 use crate::ln::chan_utils;
 use crate::ln::chan_utils::{
 	get_commitment_transaction_number_obscure_factor, max_htlcs, second_stage_tx_fees_sat,
 	selected_commitment_sat_per_1000_weight, ChannelPublicKeys, ChannelTransactionParameters,
 	ClosingTransaction, CommitmentTransaction, CounterpartyChannelTransactionParameters,
 	CounterpartyCommitmentSecrets, HTLCOutputInCommitment, HolderCommitmentTransaction,
-	FUNDING_TRANSACTION_WITNESS_WEIGHT,
+	BASE_INPUT_WEIGHT, EMPTY_SCRIPT_SIG_WEIGHT, FUNDING_TRANSACTION_WITNESS_WEIGHT,
 };
 use crate::ln::channel_state::{
 	ChannelShutdownState, CounterpartyForwardingInfo, InboundHTLCDetails, InboundHTLCStateDetails,

lightning/src/ln/channel.rs

@@ -21,7 +21,9 @@ use crate::events::{
 	ClaimedHTLC, ClosureReason, Event, HTLCHandlingFailureType, PaidBolt12Invoice, PathFailure,
 	PaymentFailureReason, PaymentPurpose,
 };
-use crate::ln::chan_utils::{commitment_tx_base_weight, COMMITMENT_TX_WEIGHT_PER_HTLC};
+use crate::ln::chan_utils::{
+	commitment_tx_base_weight, COMMITMENT_TX_WEIGHT_PER_HTLC, TRUC_MAX_WEIGHT,
+};
 use crate::ln::channelmanager::{
 	AChannelManager, ChainParameters, ChannelManager, ChannelManagerReadArgs, PaymentId,
 	RAACommitmentOrder, RecipientOnionFields, MIN_CLTV_EXPIRY_DELTA,
@@ -58,6 +60,7 @@ use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hashes::Hash as _;
 use bitcoin::locktime::absolute::{LockTime, LOCK_TIME_THRESHOLD};
 use bitcoin::network::Network;
+use bitcoin::policy::MAX_STANDARD_TX_WEIGHT;
 use bitcoin::pow::CompactTarget;
 use bitcoin::script::ScriptBuf;
 use bitcoin::secp256k1::{PublicKey, SecretKey};
@@ -400,12 +403,18 @@ fn do_connect_block_without_consistency_checks<'a, 'b, 'c, 'd>(
 }
 
 pub fn provide_anchor_reserves<'a, 'b, 'c>(nodes: &[Node<'a, 'b, 'c>]) -> Transaction {
+	provide_anchor_utxo_reserves(nodes, 1, Amount::ONE_BTC)
+}
+
+pub fn provide_anchor_utxo_reserves<'a, 'b, 'c>(
+	nodes: &[Node<'a, 'b, 'c>], utxos: usize, amount: Amount,
+) -> Transaction {
 	let mut output = Vec::with_capacity(nodes.len());
 	for node in nodes {
-		output.push(TxOut {
-			value: Amount::ONE_BTC,
-			script_pubkey: node.wallet_source.get_change_script().unwrap(),
-		});
+		let script_pubkey = node.wallet_source.get_change_script().unwrap();
+		for _ in 0..utxos {
+			output.push(TxOut { value: amount, script_pubkey: script_pubkey.clone() });
+		}
 	}
 	let tx = Transaction {
 		version: TxVersion::TWO,
@@ -1941,6 +1950,11 @@ pub fn update_nodes_with_chan_announce<'a, 'b, 'c, 'd>(
 pub fn do_check_spends<F: Fn(&bitcoin::transaction::OutPoint) -> Option<TxOut>>(
 	tx: &Transaction, get_output: F,
 ) {
+	if tx.version == TxVersion::non_standard(3) {
+		assert!(tx.weight().to_wu() <= TRUC_MAX_WEIGHT);
+	} else {
+		assert!(tx.weight().to_wu() <= MAX_STANDARD_TX_WEIGHT as u64);
+	}
 	let mut p2a_output_below_dust = false;
 	let mut has_p2a_output = false;
 	for outp in tx.output.iter() {

lightning/src/ln/functional_test_utils.rs

@@ -12,7 +12,8 @@
 use bitcoin::{Amount, ScriptBuf, SignedAmount, TxOut};
 use bitcoin::{Script, Sequence, Transaction, Weight};
 
-use crate::events::bump_transaction::{Utxo, EMPTY_SCRIPT_SIG_WEIGHT};
+use crate::events::bump_transaction::Utxo;
+use crate::ln::chan_utils::EMPTY_SCRIPT_SIG_WEIGHT;
 use crate::prelude::Vec;
 use crate::sign::{P2TR_KEY_PATH_WITNESS_WEIGHT, P2WPKH_WITNESS_WEIGHT};
 

lightning/src/ln/funding.rs

@@ -26,8 +26,9 @@ use bitcoin::{
 };
 
 use crate::chain::chaininterface::fee_for_weight;
-use crate::events::bump_transaction::{BASE_INPUT_WEIGHT, EMPTY_SCRIPT_SIG_WEIGHT};
-use crate::ln::chan_utils::FUNDING_TRANSACTION_WITNESS_WEIGHT;
+use crate::ln::chan_utils::{
+	BASE_INPUT_WEIGHT, EMPTY_SCRIPT_SIG_WEIGHT, FUNDING_TRANSACTION_WITNESS_WEIGHT,
+};
 use crate::ln::channel::{FundingNegotiationContext, TOTAL_BITCOIN_SUPPLY_SATOSHIS};
 use crate::ln::funding::FundingTxInput;
 use crate::ln::msgs;