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

@@ -13,6 +13,7 @@ dictionary Config {
 	u64 probing_liquidity_limit_multiplier;
 	AnchorChannelsConfig? anchor_channels_config;
 	SendingParameters? sending_parameters;
+	boolean? auto_rebroadcast_unconfirmed_tx
 };
 
 dictionary AnchorChannelsConfig {
@@ -104,6 +105,8 @@ interface Builder {
 	Node build_with_vss_store_and_fixed_headers(string vss_url, string store_id, record<string, string> fixed_headers);
 	[Throws=BuildError]
 	Node build_with_vss_store_and_header_provider(string vss_url, string store_id, VssHeaderProvider header_provider);
+	[Throws=BuildError]
+	void set_auto_rebroadcast_unconfirmed(boolean enable);
 };
 
 interface Node {
@@ -231,6 +234,10 @@ interface OnchainPayment {
 	Txid send_to_address([ByRef]Address address, u64 amount_sats, FeeRate? fee_rate);
 	[Throws=NodeError]
 	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 {
@@ -409,7 +416,7 @@ interface ClosureReason {
 
 [Enum]
 interface PaymentKind {
-	Onchain(Txid txid, ConfirmationStatus status);
+	Onchain(Txid txid, ConfirmationStatus status, sequence<u8>? raw_tx, u64? last_broadcast_time, u32? broadcast_attempts);
 	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);

src/payment/onchain.rs

@@ -14,6 +14,7 @@ use crate::types::{ChannelManager, Wallet};
 use crate::wallet::OnchainSendAmount;
 
 use bitcoin::{Address, Txid};
+use lightning::ln::channelmanager::PaymentId;
 
 use std::sync::{Arc, RwLock};
 
@@ -120,4 +121,30 @@ impl OnchainPayment {
 		let fee_rate_opt = maybe_map_fee_rate_opt!(fee_rate);
 		self.wallet.send_to_address(address, send_amount, fee_rate_opt)
 	}
+
+	/// Manually trigger a rebroadcast of a specific transaction according to the default policy.
+	///
+	/// This is useful if you suspect a transaction may not have propagated properly through the
+	/// network and you want to attempt to rebroadcast it immediately rather than waiting for the
+	/// automatic background job to handle it.
+	///
+	/// updating the attempt count and last broadcast time for the transaction in the payment store.
+	pub fn rebroadcast_transaction(&self, payment_id: PaymentId) -> Result<(), Error> {
+		self.wallet.rebroadcast_transaction(payment_id)?;
+		Ok(())
+	}
+
+	/// 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/store.rs

@@ -293,6 +293,24 @@ impl StorableObject for PaymentDetails {
 			}
 		}
 
+		if let Some(attempts) = update.broadcast_attempts {
+			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);
+				},
+				_ => {},
+			}
+		}
+
 		if updated {
 			self.latest_update_timestamp = SystemTime::now()
 				.duration_since(UNIX_EPOCH)
@@ -353,6 +371,12 @@ pub enum PaymentKind {
 		txid: Txid,
 		/// The confirmation status of this payment.
 		status: ConfirmationStatus,
+		/// The raw transaction for rebroadcasting
+		raw_tx: Option<Vec<u8>>,
+		/// Last broadcast attempt timestamp (UNIX seconds)
+		last_broadcast_time: Option<u64>,
+		/// Number of broadcast attempts
+		broadcast_attempts: Option<u32>,
 	},
 	/// A [BOLT 11] payment.
 	///
@@ -451,6 +475,9 @@ impl_writeable_tlv_based_enum!(PaymentKind,
 	(0, Onchain) => {
 		(0, txid, required),
 		(2, status, required),
+		(4, raw_tx, option),
+		(10, last_broadcast_time, option),
+		(12, broadcast_attempts, option),
 	},
 	(2, Bolt11) => {
 		(0, hash, required),
@@ -542,6 +569,8 @@ pub(crate) struct PaymentDetailsUpdate {
 	pub direction: Option<PaymentDirection>,
 	pub status: Option<PaymentStatus>,
 	pub confirmation_status: Option<ConfirmationStatus>,
+	pub last_broadcast_time: Option<Option<u64>>,
+	pub broadcast_attempts: Option<Option<u32>>,
 }
 
 impl PaymentDetailsUpdate {
@@ -557,6 +586,8 @@ impl PaymentDetailsUpdate {
 			direction: None,
 			status: None,
 			confirmation_status: None,
+			last_broadcast_time: None,
+			broadcast_attempts: None,
 		}
 	}
 }
@@ -572,9 +603,11 @@ impl From<&PaymentDetails> for PaymentDetailsUpdate {
 			_ => (None, None, None),
 		};
 
-		let confirmation_status = match value.kind {
-			PaymentKind::Onchain { status, .. } => Some(status),
-			_ => None,
+		let (confirmation_status, last_broadcast_time, broadcast_attempts) = match value.kind {
+			PaymentKind::Onchain { status, last_broadcast_time, broadcast_attempts, .. } => {
+				(Some(status), last_broadcast_time, broadcast_attempts)
+			},
+			_ => (None, None, None),
 		};
 
 		let counterparty_skimmed_fee_msat = match value.kind {
@@ -595,6 +628,8 @@ impl From<&PaymentDetails> for PaymentDetailsUpdate {
 			direction: Some(value.direction),
 			status: Some(value.status),
 			confirmation_status,
+			last_broadcast_time: Some(last_broadcast_time),
+			broadcast_attempts: Some(broadcast_attempts),
 		}
 	}
 }