Implement RBF fee bumping for unconfirmed transactions

Add `Replace-by-Fee` functionality to allow users to increase fees on
pending outbound transactions, improving confirmation likelihood during
network congestion.

- Uses BDK's `build_fee_bump` for transaction replacement
- Validates transaction eligibility: must be outbound and unconfirmed
- Implements fee rate estimation with safety limits
- Maintains payment history consistency across wallet updates
- Includes integration tests for various RBF scenarios

Author: Camillarhi

bindings/ldk_node.udl

@@ -269,6 +269,8 @@ interface OnchainPayment {
 	Txid send_all_to_address([ByRef]Address address, boolean retain_reserve, FeeRate? fee_rate);
 	[Throws=NodeError]
 	void rebroadcast_transaction(PaymentId payment_id);
+	[Throws=NodeError]
+	Txid bump_fee_rbf(PaymentId payment_id);
 };
 
 interface FeeRate {
@@ -454,7 +456,7 @@ interface ClosureReason {
 
 [Enum]
 interface PaymentKind {
-	Onchain(Txid txid, ConfirmationStatus status, Transaction? raw_tx, u64? last_broadcast_time, u32? broadcast_attempts);
+	Onchain(Txid txid, ConfirmationStatus status);
 	Bolt11(PaymentHash hash, PaymentPreimage? preimage, PaymentSecret? secret);
 	Bolt11Jit(PaymentHash hash, PaymentPreimage? preimage, PaymentSecret? secret, u64? counterparty_skimmed_fee_msat, LSPFeeLimits lsp_fee_limits);
 	Bolt12Offer(PaymentHash? hash, PaymentPreimage? preimage, PaymentSecret? secret, OfferId offer_id, UntrustedString? payer_note, u64? quantity);
@@ -920,6 +922,3 @@ typedef string LSPSDateTime;
 
 [Custom]
 typedef string ScriptBuf;
-
-[Custom]
-typedef string Transaction;

src/ffi/types.rs

@@ -1248,21 +1248,6 @@ impl UniffiCustomTypeConverter for LSPSDateTime {
 	}
 }
 
-impl UniffiCustomTypeConverter for Transaction {
-	type Builtin = String;
-	fn into_custom(val: Self::Builtin) -> uniffi::Result<Self> {
-		if let Some(bytes) = hex_utils::to_vec(&val) {
-			if let Ok(tx) = bitcoin::consensus::deserialize::<Transaction>(&bytes) {
-				return Ok(tx);
-			}
-		}
-		Err(Error::InvalidTransaction.into())
-	}
-	fn from_custom(obj: Self) -> Self::Builtin {
-		hex_utils::to_string(&bitcoin::consensus::serialize(&obj))
-	}
-}
-
 #[cfg(test)]
 mod tests {
 	use std::num::NonZeroU64;

src/lib.rs

@@ -124,7 +124,8 @@ pub use builder::NodeBuilder as Builder;
 use chain::ChainSource;
 use config::{
 	default_user_config, may_announce_channel, AsyncPaymentsRole, ChannelConfig, Config,
-	NODE_ANN_BCAST_INTERVAL, PEER_RECONNECTION_INTERVAL, RGS_SYNC_INTERVAL, UNCONFIRMED_TX_BROADCAST_INTERVAL,
+	NODE_ANN_BCAST_INTERVAL, PEER_RECONNECTION_INTERVAL, RGS_SYNC_INTERVAL,
+	UNCONFIRMED_TX_BROADCAST_INTERVAL,
 };
 use connection::ConnectionManager;
 pub use error::Error as NodeError;

src/payment/onchain.rs

@@ -17,11 +17,8 @@ use crate::logger::{log_info, LdkLogger, Logger};
 use crate::types::{ChannelManager, Wallet};
 use crate::wallet::OnchainSendAmount;
 
-use bitcoin::{Address, Txid};
 use lightning::ln::channelmanager::PaymentId;
 
-use std::sync::{Arc, RwLock};
-
 #[cfg(not(feature = "uniffi"))]
 type FeeRate = bitcoin::FeeRate;
 #[cfg(feature = "uniffi")]
@@ -136,4 +133,18 @@ impl OnchainPayment {
 	pub fn rebroadcast_transaction(&self, payment_id: PaymentId) -> Result<(), Error> {
 		self.wallet.rebroadcast_transaction(payment_id)
 	}
+
+	/// Attempt to bump the fee of an unconfirmed transaction using Replace-by-Fee (RBF).
+	///
+	/// This creates a new transaction that replaces the original one, increasing the fee by the
+	/// specified increment to improve its chances of confirmation. The original transaction must
+	/// be signaling RBF replaceability for this to succeed.
+	///
+	/// The new transaction will have the same outputs as the original but with a
+	/// higher fee, resulting in faster confirmation potential.
+	///
+	/// Returns the Txid of the new replacement transaction if successful.
+	pub fn bump_fee_rbf(&self, payment_id: PaymentId) -> Result<Txid, Error> {
+		self.wallet.bump_fee_rbf(payment_id)
+	}
 }

src/payment/pending_payment_store.rs

@@ -5,7 +5,7 @@
 // http://opensource.org/licenses/MIT>, at your option. You may not use this file except in
 // accordance with one or both of these licenses.
 
-use bitcoin::Txid;
+use bitcoin::{Transaction, Txid};
 use lightning::{impl_writeable_tlv_based, ln::channelmanager::PaymentId};
 
 use crate::{
@@ -20,11 +20,20 @@ pub struct PendingPaymentDetails {
 	pub details: PaymentDetails,
 	/// Transaction IDs that have replaced or conflict with this payment.
 	pub conflicting_txids: Vec<Txid>,
+	/// The raw transaction for rebroadcasting
+	pub raw_tx: Option<Transaction>,
+	/// Last broadcast attempt timestamp (UNIX seconds)
+	pub last_broadcast_time: Option<u64>,
+	/// Number of broadcast attempts
+	pub broadcast_attempts: Option<u32>,
 }
 
 impl PendingPaymentDetails {
-	pub(crate) fn new(details: PaymentDetails, conflicting_txids: Vec<Txid>) -> Self {
-		Self { details, conflicting_txids }
+	pub(crate) fn new(
+		details: PaymentDetails, conflicting_txids: Vec<Txid>, raw_tx: Option<Transaction>,
+		last_broadcast_time: Option<u64>, broadcast_attempts: Option<u32>,
+	) -> Self {
+		Self { details, conflicting_txids, raw_tx, last_broadcast_time, broadcast_attempts }
 	}
 
 	/// Convert to finalized payment for the main payment store
@@ -36,13 +45,19 @@ impl PendingPaymentDetails {
 impl_writeable_tlv_based!(PendingPaymentDetails, {
 	(0, details, required),
 	(2, conflicting_txids, optional_vec),
+	(3, raw_tx, option),
+	(5, last_broadcast_time, option),
+	(7, broadcast_attempts, option),
 });
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub(crate) struct PendingPaymentDetailsUpdate {
 	pub id: PaymentId,
 	pub payment_update: Option<PaymentDetailsUpdate>,
 	pub conflicting_txids: Option<Vec<Txid>>,
+	pub raw_tx: Option<Option<Transaction>>,
+	pub last_broadcast_time: Option<Option<u64>>,
+	pub broadcast_attempts: Option<Option<u32>>,
 }
 
 impl StorableObject for PendingPaymentDetails {
@@ -56,18 +71,39 @@ impl StorableObject for PendingPaymentDetails {
 	fn update(&mut self, update: &Self::Update) -> bool {
 		let mut updated = false;
 
+		macro_rules! update_if_necessary {
+			($val:expr, $update:expr) => {
+				if $val != $update {
+					$val = $update;
+					updated = true;
+				}
+			};
+		}
+
 		// Update the underlying payment details if present
 		if let Some(payment_update) = &update.payment_update {
 			updated |= self.details.update(payment_update);
 		}
 
 		if let Some(new_conflicting_txids) = &update.conflicting_txids {
-			if &self.conflicting_txids != new_conflicting_txids {
-				self.conflicting_txids = new_conflicting_txids.clone();
-				updated = true;
+			// Don't overwrite existing conflicts with an empty list
+			if !new_conflicting_txids.is_empty() {
+				update_if_necessary!(self.conflicting_txids, new_conflicting_txids.clone());
 			}
 		}
 
+		if let Some(new_raw_tx) = &update.raw_tx {
+			update_if_necessary!(self.raw_tx, new_raw_tx.clone());
+		}
+
+		if let Some(new_last_broadcast_time) = update.last_broadcast_time {
+			update_if_necessary!(self.last_broadcast_time, new_last_broadcast_time);
+		}
+
+		if let Some(new_broadcast_attempts) = update.broadcast_attempts {
+			update_if_necessary!(self.broadcast_attempts, new_broadcast_attempts);
+		}
+
 		updated
 	}
 
@@ -88,6 +124,9 @@ impl From<&PendingPaymentDetails> for PendingPaymentDetailsUpdate {
 			id: value.id(),
 			payment_update: Some(value.details.to_update()),
 			conflicting_txids: Some(value.conflicting_txids.clone()),
+			raw_tx: Some(value.raw_tx.clone()),
+			last_broadcast_time: Some(value.last_broadcast_time),
+			broadcast_attempts: Some(value.broadcast_attempts),
 		}
 	}
 }

src/payment/store.rs

@@ -19,10 +19,6 @@ use lightning::{
 use lightning_types::payment::{PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning_types::string::UntrustedString;
 
-use bitcoin::{BlockHash, Transaction, Txid};
-
-use std::time::{Duration, SystemTime, UNIX_EPOCH};
-
 use crate::data_store::{StorableObject, StorableObjectId, StorableObjectUpdate};
 use crate::hex_utils;
 
@@ -295,28 +291,10 @@ impl StorableObject for PaymentDetails {
 			}
 		}
 
-		if let Some(tx) = &update.raw_tx {
-			match self.kind {
-				PaymentKind::Onchain { ref mut raw_tx, .. } => {
-					update_if_necessary!(*raw_tx, tx.clone());
-				},
-				_ => {},
-			}
-		}
-
-		if let Some(attempts) = update.broadcast_attempts {
+		if let Some(tx_id) = update.txid {
 			match self.kind {
-				PaymentKind::Onchain { ref mut broadcast_attempts, .. } => {
-					update_if_necessary!(*broadcast_attempts, attempts);
-				},
-				_ => {},
-			}
-		}
-
-		if let Some(broadcast_time) = update.last_broadcast_time {
-			match self.kind {
-				PaymentKind::Onchain { ref mut last_broadcast_time, .. } => {
-					update_if_necessary!(*last_broadcast_time, broadcast_time);
+				PaymentKind::Onchain { ref mut txid, .. } => {
+					update_if_necessary!(*txid, tx_id);
 				},
 				_ => {},
 			}
@@ -382,12 +360,6 @@ pub enum PaymentKind {
 		txid: Txid,
 		/// The confirmation status of this payment.
 		status: ConfirmationStatus,
-		/// The raw transaction for rebroadcasting
-		raw_tx: Option<Transaction>,
-		/// Last broadcast attempt timestamp (UNIX seconds)
-		last_broadcast_time: Option<u64>,
-		/// Number of broadcast attempts
-		broadcast_attempts: Option<u32>,
 	},
 	/// A [BOLT 11] payment.
 	///
@@ -485,10 +457,7 @@ pub enum PaymentKind {
 impl_writeable_tlv_based_enum!(PaymentKind,
 	(0, Onchain) => {
 		(0, txid, required),
-		(1, raw_tx, option),
 		(2, status, required),
-		(3, last_broadcast_time, option),
-		(5, broadcast_attempts, option),
 	},
 	(2, Bolt11) => {
 		(0, hash, required),
@@ -580,9 +549,7 @@ pub(crate) struct PaymentDetailsUpdate {
 	pub direction: Option<PaymentDirection>,
 	pub status: Option<PaymentStatus>,
 	pub confirmation_status: Option<ConfirmationStatus>,
-	pub raw_tx: Option<Option<Transaction>>,
-	pub last_broadcast_time: Option<Option<u64>>,
-	pub broadcast_attempts: Option<Option<u32>>,
+	pub txid: Option<Txid>,
 }
 
 impl PaymentDetailsUpdate {
@@ -598,9 +565,7 @@ impl PaymentDetailsUpdate {
 			direction: None,
 			status: None,
 			confirmation_status: None,
-			raw_tx: None,
-			last_broadcast_time: None,
-			broadcast_attempts: None,
+			txid: None,
 		}
 	}
 }
@@ -616,17 +581,10 @@ impl From<&PaymentDetails> for PaymentDetailsUpdate {
 			_ => (None, None, None),
 		};
 
-		let (confirmation_status, raw_tx, last_broadcast_time, broadcast_attempts) =
-			match &value.kind {
-				PaymentKind::Onchain {
-					status,
-					raw_tx,
-					last_broadcast_time,
-					broadcast_attempts,
-					..
-				} => (Some(*status), raw_tx.clone(), *last_broadcast_time, *broadcast_attempts),
-				_ => (None, None, None, None),
-			};
+		let (confirmation_status, txid) = match &value.kind {
+			PaymentKind::Onchain { status, txid, .. } => (Some(*status), Some(*txid)),
+			_ => (None, None),
+		};
 
 		let counterparty_skimmed_fee_msat = match value.kind {
 			PaymentKind::Bolt11Jit { counterparty_skimmed_fee_msat, .. } => {
@@ -646,9 +604,7 @@ impl From<&PaymentDetails> for PaymentDetailsUpdate {
 			direction: Some(value.direction),
 			status: Some(value.status),
 			confirmation_status,
-			raw_tx: Some(raw_tx),
-			last_broadcast_time: Some(last_broadcast_time),
-			broadcast_attempts: Some(broadcast_attempts),
+			txid,
 		}
 	}
 }