Store HTLC pending retry data upon path failure

And generate a PendingHTLCsForwardable event, since we'll be retrying these
payments in process_pending_htlcs_forwardable in the next commit(s).

No retries will be stored or events generated yet since we currently always
pass RetryAttempts::(0).

Author: valentinewallace

lightning/src/ln/channelmanager.rs

@@ -386,7 +386,7 @@ impl MsgHandleErrInternal {
 /// Event::PendingHTLCsForwardable for the API guidelines indicating how long should be waited).
 /// This provides some limited amount of privacy. Ideally this would range from somewhere like one
 /// second to 30 seconds, but people expect lightning to be, you know, kinda fast, sadly.
-const MIN_HTLC_RELAY_HOLDING_CELL_MILLIS: u64 = 100;
+pub(super) const MIN_HTLC_RELAY_HOLDING_CELL_MILLIS: u64 = 100;
 
 /// For events which result in both a RevokeAndACK and a CommitmentUpdate, by default they should
 /// be sent in the order they appear in the return value, however sometimes the order needs to be

lightning/src/ln/outbound_payment.rs

@@ -15,7 +15,7 @@ use bitcoin::secp256k1::{self, Secp256k1, SecretKey};
 
 use crate::chain::keysinterface::{KeysInterface, Recipient};
 use crate::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
-use crate::ln::channelmanager::{HTLCSource, IDEMPOTENCY_TIMEOUT_TICKS, PaymentId};
+use crate::ln::channelmanager::{HTLCSource, IDEMPOTENCY_TIMEOUT_TICKS, MIN_HTLC_RELAY_HOLDING_CELL_MILLIS, PaymentId};
 use crate::ln::msgs::DecodeError;
 use crate::ln::onion_utils::HTLCFailReason;
 use crate::routing::router::{PaymentParameters, Route, RouteHop, RouteParameters, RoutePath};
@@ -30,6 +30,7 @@ use core::cmp;
 use core::fmt::{self, Display, Formatter};
 use core::ops::Deref;
 use core::sync::atomic::{AtomicUsize, Ordering};
+use core::time::Duration;
 
 use crate::prelude::*;
 use crate::sync::Mutex;
@@ -783,7 +784,8 @@ impl OutboundPayments {
 		let mut outbounds = self.pending_outbound_payments.lock().unwrap();
 		let mut all_paths_failed = false;
 		let mut full_failure_ev = None;
-		if let hash_map::Entry::Occupied(mut payment) = outbounds.entry(*payment_id) {
+		let mut pending_retry_ev = None;
+		let attempts_remaining = if let hash_map::Entry::Occupied(mut payment) = outbounds.entry(*payment_id) {
 			if !payment.get_mut().remove(&session_priv_bytes, Some(&path)) {
 				log_trace!(logger, "Received duplicative fail for HTLC with payment_hash {}", log_bytes!(payment_hash.0));
 				return (None, None);
@@ -792,6 +794,7 @@ impl OutboundPayments {
 				log_trace!(logger, "Received failure of HTLC with payment_hash {} after payment completion", log_bytes!(payment_hash.0));
 				return (None, None);
 			}
+			let is_retryable = payment.get().is_retryable();
 			if payment.get().remaining_parts() == 0 {
 				all_paths_failed = true;
 				if payment.get().abandoned() {
@@ -802,10 +805,11 @@ impl OutboundPayments {
 					payment.remove();
 				}
 			}
+			is_retryable
 		} else {
 			log_trace!(logger, "Received duplicative fail for HTLC with payment_hash {}", log_bytes!(payment_hash.0));
 			return (None, None);
-		}
+		};
 		let mut retry = if let Some(payment_params_data) = payment_params {
 			let path_last_hop = path.last().expect("Outbound payments must have had a valid path");
 			Some(RouteParameters {
@@ -844,6 +848,15 @@ impl OutboundPayments {
 				if let Some(scid) = short_channel_id {
 					retry.as_mut().map(|r| r.payment_params.previously_failed_channels.push(scid));
 				}
+				if payment_retryable && attempts_remaining {
+					if let Some(retry_params) = &retry {
+						debug_assert!(full_failure_ev.is_none());
+						pending_retry_ev = Some(events::Event::PendingHTLCsForwardable {
+							time_forwardable: Duration::from_millis(MIN_HTLC_RELAY_HOLDING_CELL_MILLIS),
+						});
+						self.retryable_htlcs.lock().unwrap().push((*payment_id, retry_params.clone()));
+					}
+				}
 				events::Event::PaymentPathFailed {
 					payment_id: Some(*payment_id),
 					payment_hash: payment_hash.clone(),
@@ -860,7 +873,7 @@ impl OutboundPayments {
 				}
 			}
 		};
-		(Some(path_failure), full_failure_ev)
+		(Some(path_failure), full_failure_ev.or(pending_retry_ev))
 	}
 
 	pub(super) fn abandon_payment(&self, payment_id: PaymentId) -> Option<events::Event> {