wip: replay of trampoline forwards

lightning/src/ln/channel.rs

@@ -52,7 +52,7 @@ use crate::ln::channel_state::{
 use crate::ln::channelmanager::{
 	self, BlindedFailure, ChannelReadyOrder, FundingConfirmedMessage, HTLCFailureMsg,
 	HTLCPreviousHopData, HTLCSource, OpenChannelMessage, PaymentClaimDetails, PendingHTLCInfo,
-	PendingHTLCStatus, RAACommitmentOrder, SentHTLCId, BREAKDOWN_TIMEOUT,
+	PendingHTLCStatus, RAACommitmentOrder, SentHTLCId, TrampolineDispatch, BREAKDOWN_TIMEOUT,
 	MAX_LOCAL_BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA,
 };
 use crate::ln::funding::{FundingContribution, FundingTemplate, FundingTxInput};
@@ -356,6 +356,16 @@ enum InboundUpdateAdd {
 		blinded_failure: Option<BlindedFailure>,
 		outbound_hop: OutboundHop,
 	},
+	/// This inbound HTLC is a forward that was irrevocably committed to outbound edge(s) as part
+	/// of a trampoline forward, allowing its onion to be pruned and no longer persisted.
+	///
+	/// Contains data that is useful if we need to fail or claim this HTLC backwards after a
+	/// restart and it's missing in the outbound edge.
+	TrampolineForwarded {
+		previous_hop_data: Vec<HTLCPreviousHopData>,
+		outbound_hops: Vec<(OutboundHop, TrampolineDispatch)>,
+		incoming_trampoline_shared_secret: [u8; 32],
+	},
 	/// This HTLC was received pre-LDK 0.3, before we started persisting the onion for inbound
 	/// committed HTLCs.
 	Legacy,
@@ -373,6 +383,11 @@ impl_writeable_tlv_based_enum_upgradable!(InboundUpdateAdd,
 		(6, trampoline_shared_secret, option),
 		(8, blinded_failure, option),
 	},
+	(6, TrampolineForwarded) => {
+		(0, previous_hop_data, required_vec),
+		(2, outbound_hops, required_vec),
+		(4, incoming_trampoline_shared_secret, required),
+	},
 );
 
 impl_writeable_for_vec!(&InboundUpdateAdd);
@@ -1193,7 +1208,7 @@ pub(super) struct MonitorRestoreUpdates {
 	/// The sources of outbound HTLCs that were forwarded and irrevocably committed on this channel
 	/// (the outbound edge), along with their outbound amounts. Useful to store in the inbound HTLC
 	/// to ensure it gets resolved.
-	pub committed_outbound_htlc_sources: Vec<(HTLCPreviousHopData, u64)>,
+	pub committed_outbound_htlc_sources: Vec<(HTLCSource, u64)>,
 }
 
 /// The return value of `signer_maybe_unblocked`
@@ -7451,7 +7466,7 @@ where
 	/// when reconstructing the set of pending HTLCs when deserializing the `ChannelManager`.
 	pub(super) fn inbound_forwarded_htlcs(
 		&self,
-	) -> impl Iterator<Item = (PaymentHash, HTLCPreviousHopData, OutboundHop)> + '_ {
+	) -> impl Iterator<Item = (PaymentHash, Vec<(HTLCSource, OutboundHop)>)> + '_ {
 		// We don't want to return an HTLC as needing processing if it already has a resolution that's
 		// pending in the holding cell.
 		let htlc_resolution_in_holding_cell = |id: u64| -> bool {
@@ -7500,7 +7515,38 @@ where
 					counterparty_node_id: Some(counterparty_node_id),
 					cltv_expiry: Some(htlc.cltv_expiry),
 				};
-				Some((htlc.payment_hash, prev_hop_data, *outbound_hop))
+				Some((
+					htlc.payment_hash,
+					vec![(HTLCSource::PreviousHopData(prev_hop_data), *outbound_hop)],
+				))
+			},
+			InboundHTLCState::Committed {
+				update_add_htlc:
+					InboundUpdateAdd::TrampolineForwarded {
+						previous_hop_data,
+						outbound_hops,
+						incoming_trampoline_shared_secret,
+					},
+			} => {
+				if htlc_resolution_in_holding_cell(htlc.htlc_id) {
+					return None;
+				}
+				let trampoline_sources: Vec<(HTLCSource, OutboundHop)> = outbound_hops
+					.iter()
+					.map(|(hop, dispatch)| {
+						(
+							HTLCSource::TrampolineForward {
+								previous_hop_data: previous_hop_data.clone(),
+								incoming_trampoline_shared_secret:
+									*incoming_trampoline_shared_secret,
+								outbound_payment: Some(dispatch.clone()),
+							},
+							*hop,
+						)
+					})
+					.collect();
+
+				Some((htlc.payment_hash, trampoline_sources))
 			},
 			_ => None,
 		})
@@ -7511,21 +7557,21 @@ where
 	/// present in the outbound edge, or else we'll double-forward.
 	pub(super) fn outbound_htlc_forwards(
 		&self,
-	) -> impl Iterator<Item = (PaymentHash, HTLCPreviousHopData)> + '_ {
+	) -> impl Iterator<Item = (PaymentHash, HTLCSource)> + '_ {
 		let holding_cell_outbounds =
 			self.context.holding_cell_htlc_updates.iter().filter_map(|htlc| match htlc {
 				HTLCUpdateAwaitingACK::AddHTLC { source, payment_hash, .. } => match source {
-					HTLCSource::PreviousHopData(prev_hop_data) => {
-						Some((*payment_hash, prev_hop_data.clone()))
+					HTLCSource::PreviousHopData(_) | HTLCSource::TrampolineForward { .. } => {
+						Some((*payment_hash, source.clone()))
 					},
 					_ => None,
 				},
 				_ => None,
 			});
 		let committed_outbounds =
 			self.context.pending_outbound_htlcs.iter().filter_map(|htlc| match &htlc.source {
-				HTLCSource::PreviousHopData(prev_hop_data) => {
-					Some((htlc.payment_hash, prev_hop_data.clone()))
+				HTLCSource::PreviousHopData(_) | HTLCSource::TrampolineForward { .. } => {
+					Some((htlc.payment_hash, htlc.source.clone()))
 				},
 				_ => None,
 			});
@@ -7550,20 +7596,69 @@ where
 	/// This inbound HTLC was irrevocably forwarded to the outbound edge, so we no longer need to
 	/// persist its onion.
 	pub(super) fn prune_inbound_htlc_onion(
-		&mut self, htlc_id: u64, prev_hop_data: &HTLCPreviousHopData,
-		outbound_hop_data: OutboundHop,
+		&mut self, htlc_id: u64, htlc_source: &HTLCSource, outbound_hop_data: OutboundHop,
 	) {
 		for htlc in self.context.pending_inbound_htlcs.iter_mut() {
+			// TODO: all these returns are super mif
 			if htlc.htlc_id == htlc_id {
-				if let InboundHTLCState::Committed { ref mut update_add_htlc } = htlc.state {
-					*update_add_htlc = InboundUpdateAdd::Forwarded {
-						incoming_packet_shared_secret: prev_hop_data.incoming_packet_shared_secret,
-						phantom_shared_secret: prev_hop_data.phantom_shared_secret,
-						trampoline_shared_secret: prev_hop_data.trampoline_shared_secret,
-						blinded_failure: prev_hop_data.blinded_failure,
-						outbound_hop: outbound_hop_data,
-					};
-					return;
+				match &mut htlc.state {
+					InboundHTLCState::Committed {
+						update_add_htlc: InboundUpdateAdd::TrampolineForwarded { outbound_hops, .. },
+					} => {
+						if let HTLCSource::TrampolineForward {
+							outbound_payment: Some(trampoline_dispatch),
+							..
+						} = htlc_source
+						{
+							if !outbound_hops.iter().any(|(_, dispatch)| {
+								dispatch.session_priv == trampoline_dispatch.session_priv
+							}) {
+								outbound_hops.push((outbound_hop_data, trampoline_dispatch.clone()))
+							}
+							return;
+						} else {
+							debug_assert!(false, "prune inbound onion called for trampoline with no dispatch or on non-trampoline inbound");
+							return;
+						}
+					},
+					InboundHTLCState::Committed { update_add_htlc } => {
+						*update_add_htlc = match htlc_source {
+							HTLCSource::PreviousHopData(prev_hop_data) => {
+								InboundUpdateAdd::Forwarded {
+									incoming_packet_shared_secret: prev_hop_data
+										.incoming_packet_shared_secret,
+									phantom_shared_secret: prev_hop_data.phantom_shared_secret,
+									trampoline_shared_secret: prev_hop_data
+										.trampoline_shared_secret,
+									blinded_failure: prev_hop_data.blinded_failure,
+									outbound_hop: outbound_hop_data,
+								}
+							},
+							HTLCSource::TrampolineForward {
+								previous_hop_data,
+								incoming_trampoline_shared_secret,
+								outbound_payment,
+							} => {
+								InboundUpdateAdd::TrampolineForwarded {
+									previous_hop_data: previous_hop_data.to_vec(),
+									outbound_hops: vec![(outbound_hop_data, outbound_payment
+										.clone() // TODO: no clone / expect
+										.expect("trampoline shouldn't be pruned with no payment data"))],
+									incoming_trampoline_shared_secret:
+										*incoming_trampoline_shared_secret,
+								}
+							},
+							_ => {
+								debug_assert!(
+									false,
+									"outbound route should not prune inbound htlc"
+								);
+								return;
+							},
+						};
+						return;
+					},
+					_ => {},
 				}
 			}
 		}
@@ -9184,8 +9279,8 @@ where
 		mem::swap(&mut pending_update_adds, &mut self.context.monitor_pending_update_adds);
 		let committed_outbound_htlc_sources = self.context.pending_outbound_htlcs.iter().filter_map(|htlc| {
 			if let &OutboundHTLCState::LocalAnnounced(_) = &htlc.state {
-				if let HTLCSource::PreviousHopData(prev_hop_data) = &htlc.source {
-					return Some((prev_hop_data.clone(), htlc.amount_msat))
+				if let HTLCSource::PreviousHopData(_) | HTLCSource::TrampolineForward { .. } = &htlc.source {
+					return Some((htlc.source.clone(), htlc.amount_msat))
 				}
 			}
 			None