Introduce Retry Invoice Flow

Description:

- Add functionality to handle retrying the sending of invoice_request
  messages on new reply_paths that are still awaiting invoices.

Changes:

1. Introduced invoice_request as an optional field in the `PendingOutboundPayments::AwaitingInvoice`
   variant to accommodate instances without invoice requests.
2. Refactored logic from `pay_for_offer` to create invoice request messages into a separate function
   for reuse with retry message flow.
3. Implemented `retry_tick_occurred` function in ChannelManager to handle generating invoice request
   messages for AwaitingInvoice payments and enqueueing them.
4. Added `retry_tick_occurred` to ln_background_processor with a timer duration of 5 seconds for
   timely retries without overwhelming the system with too many onion_messages.

lightning-background-processor/src/lib.rs

@@ -64,8 +64,9 @@ use alloc::vec::Vec;
 /// * Monitoring whether the [`ChannelManager`] needs to be re-persisted to disk, and if so,
 ///   writing it to disk/backups by invoking the callback given to it at startup.
 ///   [`ChannelManager`] persistence should be done in the background.
-/// * Calling [`ChannelManager::timer_tick_occurred`], [`ChainMonitor::rebroadcast_pending_claims`]
-///   and [`PeerManager::timer_tick_occurred`] at the appropriate intervals.
+/// * Calling [`ChannelManager::timer_tick_occurred`], [`ChannelManager::retry_tick_occurred`]
+///   [`ChainMonitor::rebroadcast_pending_claims`] and [`PeerManager::timer_tick_occurred`]
+///   at the appropriate intervals.
 /// * Calling [`NetworkGraph::remove_stale_channels_and_tracking`] (if a [`GossipSync`] with a
 ///   [`NetworkGraph`] is provided to [`BackgroundProcessor::start`]).
 ///
@@ -81,6 +82,7 @@ use alloc::vec::Vec;
 ///
 /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
 /// [`ChannelManager::timer_tick_occurred`]: lightning::ln::channelmanager::ChannelManager::timer_tick_occurred
+/// [`ChannelManager::retry_tick_occurred`]: lightning::ln::channelmanager::ChannelManager::retry_tick_occurred
 /// [`ChannelMonitor`]: lightning::chain::channelmonitor::ChannelMonitor
 /// [`Event`]: lightning::events::Event
 /// [`PeerManager::timer_tick_occurred`]: lightning::ln::peer_handler::PeerManager::timer_tick_occurred
@@ -97,6 +99,11 @@ const FRESHNESS_TIMER: u64 = 60;
 #[cfg(test)]
 const FRESHNESS_TIMER: u64 = 1;
 
+#[cfg(not(test))]
+const RETRY_TIMER: u64 = 5;
+#[cfg(test)]
+const RETRY_TIMER: u64 = 1;
+
 #[cfg(all(not(test), not(debug_assertions)))]
 const PING_TIMER: u64 = 10;
 /// Signature operations take a lot longer without compiler optimisations.
@@ -134,7 +141,7 @@ const REBROADCAST_TIMER: u64 = 1;
 /// core::cmp::min is not currently const, so we define a trivial (and equivalent) replacement
 const fn min_u64(a: u64, b: u64) -> u64 { if a < b { a } else { b } }
 #[cfg(feature = "futures")]
-const FASTEST_TIMER: u64 = min_u64(min_u64(FRESHNESS_TIMER, PING_TIMER),
+const FASTEST_TIMER: u64 = min_u64(min_u64(RETRY_TIMER, min_u64(FRESHNESS_TIMER, PING_TIMER)),
 	min_u64(SCORER_PERSIST_TIMER, min_u64(FIRST_NETWORK_PRUNE_TIMER, REBROADCAST_TIMER)));
 
 /// Either [`P2PGossipSync`] or [`RapidGossipSync`].
@@ -291,6 +298,7 @@ macro_rules! define_run_body {
 		$chain_monitor.rebroadcast_pending_claims();
 
 		let mut last_freshness_call = $get_timer(FRESHNESS_TIMER);
+		let mut last_retry_call = $get_timer(RETRY_TIMER);
 		let mut last_onion_message_handler_call = $get_timer(ONION_MESSAGE_HANDLER_TIMER);
 		let mut last_ping_call = $get_timer(PING_TIMER);
 		let mut last_prune_call = $get_timer(FIRST_NETWORK_PRUNE_TIMER);
@@ -346,6 +354,11 @@ macro_rules! define_run_body {
 				$channel_manager.get_cm().timer_tick_occurred();
 				last_freshness_call = $get_timer(FRESHNESS_TIMER);
 			}
+			if $timer_elapsed(&mut last_retry_call, RETRY_TIMER) {
+				log_trace!($logger, "Calling ChannelManager's retry_tick_occurred");
+				$channel_manager.get_cm().retry_tick_occurred();
+				last_retry_call = $get_timer(RETRY_TIMER);
+			}
 			if $timer_elapsed(&mut last_onion_message_handler_call, ONION_MESSAGE_HANDLER_TIMER) {
 				log_trace!($logger, "Calling OnionMessageHandler's timer_tick_occurred");
 				$peer_manager.onion_message_handler().timer_tick_occurred();
@@ -1444,6 +1457,7 @@ mod tests {
 		// - `ChainMonitor::rebroadcast_pending_claims` is called every `REBROADCAST_TIMER`,
 		// - `PeerManager::timer_tick_occurred` is called every `PING_TIMER`, and
 		// - `OnionMessageHandler::timer_tick_occurred` is called every `ONION_MESSAGE_HANDLER_TIMER`.
+		// - `ChannelManager::retry_tick_occurred` is called every `RETRY_TIMER`.
 		let (_, nodes) = create_nodes(1, "test_timer_tick_called");
 		let data_dir = nodes[0].kv_store.get_data_dir();
 		let persister = Arc::new(Persister::new(data_dir));
@@ -1455,10 +1469,12 @@ mod tests {
 			let desired_log_2 = "Calling PeerManager's timer_tick_occurred".to_string();
 			let desired_log_3 = "Rebroadcasting monitor's pending claims".to_string();
 			let desired_log_4 = "Calling OnionMessageHandler's timer_tick_occurred".to_string();
+			let desired_log_5 = "Calling ChannelManager's retry_tick_occurred".to_string();
 			if log_entries.get(&("lightning_background_processor", desired_log_1)).is_some() &&
 				log_entries.get(&("lightning_background_processor", desired_log_2)).is_some() &&
 				log_entries.get(&("lightning_background_processor", desired_log_3)).is_some() &&
-				log_entries.get(&("lightning_background_processor", desired_log_4)).is_some() {
+				log_entries.get(&("lightning_background_processor", desired_log_4)).is_some() &&
+				log_entries.get(&("lightning_background_processor", desired_log_5)).is_some() {
 				break
 			}
 		}

lightning/src/ln/channelmanager.rs

@@ -76,6 +76,8 @@ use crate::util::string::UntrustedString;
 use crate::util::ser::{BigSize, FixedLengthReader, Readable, ReadableArgs, MaybeReadable, Writeable, Writer, VecWriter};
 use crate::util::logger::{Level, Logger, WithContext};
 use crate::util::errors::APIError;
+use super::onion_utils::construct_invoice_request_message;
+
 #[cfg(not(c_bindings))]
 use {
 	crate::offers::offer::DerivedMetadata,
@@ -6010,6 +6012,20 @@ where
 		});
 	}
 
+	pub fn retry_tick_occurred(&self) {
+		let invoice_requests = self.pending_outbound_payments.get_invoice_request_awaiting_invoice();
+
+		if invoice_requests.is_empty() { return; }
+
+		if let Ok(reply_path) = self.create_blinded_path() {
+			let mut pending_offers_messages = self.pending_offers_messages.lock().unwrap();
+
+			for invoice_request in invoice_requests {
+				pending_offers_messages.extend(construct_invoice_request_message(invoice_request, reply_path.clone()));
+			}
+		}
+	}
+
 	/// Indicates that the preimage for payment_hash is unknown or the received amount is incorrect
 	/// after a PaymentClaimable event, failing the HTLC back to its origin and freeing resources
 	/// along the path (including in our own channel on which we received it).
@@ -8623,7 +8639,7 @@ macro_rules! create_refund_builder { ($self: ident, $builder: ty) => {
 		let expiration = StaleExpiration::AbsoluteTimeout(absolute_expiry);
 		$self.pending_outbound_payments
 			.add_new_awaiting_invoice(
-				payment_id, expiration, retry_strategy, max_total_routing_fee_msat,
+				payment_id, expiration, retry_strategy, max_total_routing_fee_msat, None
 			)
 			.map_err(|_| Bolt12SemanticError::DuplicatePaymentId)?;
 
@@ -8740,32 +8756,12 @@ where
 		let expiration = StaleExpiration::TimerTicks(1);
 		self.pending_outbound_payments
 			.add_new_awaiting_invoice(
-				payment_id, expiration, retry_strategy, max_total_routing_fee_msat
+				payment_id, expiration, retry_strategy, max_total_routing_fee_msat, Some(invoice_request)
 			)
 			.map_err(|_| Bolt12SemanticError::DuplicatePaymentId)?;
 
 		let mut pending_offers_messages = self.pending_offers_messages.lock().unwrap();
-		if offer.paths().is_empty() {
-			let message = new_pending_onion_message(
-				OffersMessage::InvoiceRequest(invoice_request),
-				Destination::Node(offer.signing_pubkey()),
-				Some(reply_path),
-			);
-			pending_offers_messages.push(message);
-		} else {
-			// Send as many invoice requests as there are paths in the offer (with an upper bound).
-			// Using only one path could result in a failure if the path no longer exists. But only
-			// one invoice for a given payment id will be paid, even if more than one is received.
-			const REQUEST_LIMIT: usize = 10;
-			for path in offer.paths().into_iter().take(REQUEST_LIMIT) {
-				let message = new_pending_onion_message(
-					OffersMessage::InvoiceRequest(invoice_request.clone()),
-					Destination::BlindedPath(path.clone()),
-					Some(reply_path.clone()),
-				);
-				pending_offers_messages.push(message);
-			}
-		}
+		pending_offers_messages.extend(construct_invoice_request_message(invoice_request, reply_path));
 
 		Ok(())
 	}

lightning/src/ln/onion_utils.rs

@@ -7,12 +7,16 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
+use crate::blinded_path::BlindedPath;
 use crate::crypto::chacha20::ChaCha20;
 use crate::crypto::streams::ChaChaReader;
 use crate::ln::channelmanager::{HTLCSource, RecipientOnionFields};
 use crate::ln::msgs;
 use crate::ln::wire::Encode;
 use crate::ln::{PaymentHash, PaymentPreimage};
+use crate::offers::invoice_request::InvoiceRequest;
+use crate::onion_message::messenger::{new_pending_onion_message, Destination, PendingOnionMessage};
+use crate::onion_message::offers::OffersMessage;
 use crate::routing::gossip::NetworkUpdate;
 use crate::routing::router::{BlindedTail, Path, RouteHop};
 use crate::sign::NodeSigner;
@@ -1235,6 +1239,32 @@ fn decode_next_hop<T, R: ReadableArgs<T>, N: NextPacketBytes>(
 	}
 }
 
+pub fn construct_invoice_request_message(invoice_request: InvoiceRequest, reply_path: BlindedPath) -> Vec<PendingOnionMessage<OffersMessage>> {
+	let mut messages = vec![];
+	if invoice_request.paths().is_empty() {
+		let message = new_pending_onion_message(
+			OffersMessage::InvoiceRequest(invoice_request),
+			Destination::Node(invoice_request.signing_pubkey()),
+			Some(reply_path),
+		);
+		messages.push(message);
+	} else {
+		// Send as many invoice requests as there are paths in the offer (with an upper bound).
+		// Using only one path could result in a failure if the path no longer exists. But only
+		// one invoice for a given payment id will be paid, even if more than one is received.
+		const REQUEST_LIMIT: usize = 10;
+		for path in invoice_request.paths().into_iter().take(REQUEST_LIMIT) {
+			let message = new_pending_onion_message(
+				OffersMessage::InvoiceRequest(invoice_request.clone()),
+				Destination::BlindedPath(path.clone()),
+				Some(reply_path.clone()),
+			);
+			messages.push(message);
+		}
+	}
+	messages
+}
+
 #[cfg(test)]
 mod tests {
 	use crate::io;

lightning/src/ln/outbound_payment.rs

@@ -13,6 +13,7 @@ use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::secp256k1::{self, Secp256k1, SecretKey};
 
+use crate::offers::invoice_request::InvoiceRequest;
 use crate::sign::{EntropySource, NodeSigner, Recipient};
 use crate::events::{self, PaymentFailureReason};
 use crate::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
@@ -50,6 +51,7 @@ pub(crate) enum PendingOutboundPayment {
 		expiration: StaleExpiration,
 		retry_strategy: Retry,
 		max_total_routing_fee_msat: Option<u64>,
+		invoice_request: Option<InvoiceRequest>,
 	},
 	InvoiceReceived {
 		payment_hash: PaymentHash,
@@ -1291,7 +1293,7 @@ impl OutboundPayments {
 
 	pub(super) fn add_new_awaiting_invoice(
 		&self, payment_id: PaymentId, expiration: StaleExpiration, retry_strategy: Retry,
-		max_total_routing_fee_msat: Option<u64>
+		max_total_routing_fee_msat: Option<u64>, invoice_request: Option<InvoiceRequest>
 	) -> Result<(), ()> {
 		let mut pending_outbounds = self.pending_outbound_payments.lock().unwrap();
 		match pending_outbounds.entry(payment_id) {
@@ -1301,6 +1303,7 @@ impl OutboundPayments {
 					expiration,
 					retry_strategy,
 					max_total_routing_fee_msat,
+					invoice_request,
 				});
 
 				Ok(())
@@ -1766,6 +1769,20 @@ impl OutboundPayments {
 	pub fn clear_pending_payments(&self) {
 		self.pending_outbound_payments.lock().unwrap().clear()
 	}
+
+	pub fn get_invoice_request_awaiting_invoice(&self) -> Vec<InvoiceRequest> {
+		let pending_outbound_payments = self.pending_outbound_payments.lock().unwrap();
+
+		pending_outbound_payments.iter().filter_map(
+			|(_, payment)| {
+				if let PendingOutboundPayment::AwaitingInvoice { invoice_request, .. } = payment {
+					invoice_request.clone()
+				} else {
+					None
+				}
+			}
+		).collect()
+	}
 }
 
 /// Returns whether a payment with the given [`PaymentHash`] and [`PaymentId`] is, in fact, a
@@ -1821,6 +1838,7 @@ impl_writeable_tlv_based_enum_upgradable!(PendingOutboundPayment,
 		(0, expiration, required),
 		(2, retry_strategy, required),
 		(4, max_total_routing_fee_msat, option),
+		(6, invoice_request, option),
 	},
 	(7, InvoiceReceived) => {
 		(0, payment_hash, required),
@@ -2058,7 +2076,7 @@ mod tests {
 		assert!(!outbound_payments.has_pending_payments());
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
@@ -2084,14 +2102,14 @@ mod tests {
 
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
 
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_err()
 		);
 	}
@@ -2107,7 +2125,7 @@ mod tests {
 		assert!(!outbound_payments.has_pending_payments());
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
@@ -2133,14 +2151,14 @@ mod tests {
 
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
 
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_err()
 		);
 	}
@@ -2155,7 +2173,7 @@ mod tests {
 		assert!(!outbound_payments.has_pending_payments());
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
@@ -2188,7 +2206,7 @@ mod tests {
 
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), None
+				payment_id, expiration, Retry::Attempts(0), None, None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
@@ -2250,7 +2268,7 @@ mod tests {
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
 				payment_id, expiration, Retry::Attempts(0),
-				Some(invoice.amount_msats() / 100 + 50_000)
+				Some(invoice.amount_msats() / 100 + 50_000), None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());
@@ -2347,7 +2365,7 @@ mod tests {
 
 		assert!(
 			outbound_payments.add_new_awaiting_invoice(
-				payment_id, expiration, Retry::Attempts(0), Some(1234)
+				payment_id, expiration, Retry::Attempts(0), Some(1234), None
 			).is_ok()
 		);
 		assert!(outbound_payments.has_pending_payments());