X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Fchannelmanager.rs;h=20014f799ee5db53eec61bd1ad4c66cf3096e0ec;hb=fb6e018eb8fc6598da0b9f36ce7aa458f4df6a0c;hp=d802318975e6609adc33f7f50b873afa6108aad5;hpb=8fe7cbe9216975bfdb783af2b11203400e0a2d21;p=rust-lightning

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index d8023189..20014f79 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -2233,8 +2233,9 @@ impl<M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelManager<M, T, K, F
 						None => { // unknown_next_peer
 							// Note that this is likely a timing oracle for detecting whether an scid is a
 							// phantom or an intercept.
-							if fake_scid::is_valid_phantom(&self.fake_scid_rand_bytes, *short_channel_id, &self.genesis_hash) ||
-							   fake_scid::is_valid_intercept(&self.fake_scid_rand_bytes, *short_channel_id, &self.genesis_hash)
+							if (self.default_configuration.accept_intercept_htlcs &&
+							   fake_scid::is_valid_intercept(&self.fake_scid_rand_bytes, *short_channel_id, &self.genesis_hash)) ||
+							   fake_scid::is_valid_phantom(&self.fake_scid_rand_bytes, *short_channel_id, &self.genesis_hash)
 							{
 								None
 							} else {
@@ -3051,6 +3052,102 @@ impl<M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelManager<M, T, K, F
 		Ok(())
 	}
 
+	/// Attempts to forward an intercepted HTLC over the provided channel id and with the provided
+	/// amount to forward. Should only be called in response to an [`HTLCIntercepted`] event.
+	///
+	/// Intercepted HTLCs can be useful for Lightning Service Providers (LSPs) to open a just-in-time
+	/// channel to a receiving node if the node lacks sufficient inbound liquidity.
+	///
+	/// To make use of intercepted HTLCs, set [`UserConfig::accept_intercept_htlcs`] and use
+	/// [`ChannelManager::get_intercept_scid`] to generate short channel id(s) to put in the
+	/// receiver's invoice route hints. These route hints will signal to LDK to generate an
+	/// [`HTLCIntercepted`] event when it receives the forwarded HTLC, and this method or
+	/// [`ChannelManager::fail_intercepted_htlc`] MUST be called in response to the event.
+	///
+	/// Note that LDK does not enforce fee requirements in `amt_to_forward_msat`, and will not stop
+	/// you from forwarding more than you received.
+	///
+	/// Errors if the event was not handled in time, in which case the HTLC was automatically failed
+	/// backwards.
+	///
+	/// [`UserConfig::accept_intercept_htlcs`]: crate::util::config::UserConfig::accept_intercept_htlcs
+	/// [`HTLCIntercepted`]: events::Event::HTLCIntercepted
+	// TODO: when we move to deciding the best outbound channel at forward time, only take
+	// `next_node_id` and not `next_hop_channel_id`
+	pub fn forward_intercepted_htlc(&self, intercept_id: InterceptId, next_hop_channel_id: &[u8; 32], _next_node_id: PublicKey, amt_to_forward_msat: u64) -> Result<(), APIError> {
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(&self.total_consistency_lock, &self.persistence_notifier);
+
+		let next_hop_scid = match self.channel_state.lock().unwrap().by_id.get(next_hop_channel_id) {
+			Some(chan) => {
+				if !chan.is_usable() {
+					return Err(APIError::APIMisuseError {
+						err: format!("Channel with id {:?} not fully established", next_hop_channel_id)
+					})
+				}
+				chan.get_short_channel_id().unwrap_or(chan.outbound_scid_alias())
+			},
+			None => return Err(APIError::APIMisuseError {
+				err: format!("Channel with id {:?} not found", next_hop_channel_id)
+			})
+		};
+
+		let payment = self.pending_intercepted_htlcs.lock().unwrap().remove(&intercept_id)
+			.ok_or_else(|| APIError::APIMisuseError {
+				err: format!("Payment with intercept id {:?} not found", intercept_id.0)
+			})?;
+
+		let routing = match payment.forward_info.routing {
+			PendingHTLCRouting::Forward { onion_packet, .. } => {
+				PendingHTLCRouting::Forward { onion_packet, short_channel_id: next_hop_scid }
+			},
+			_ => unreachable!() // Only `PendingHTLCRouting::Forward`s are intercepted
+		};
+		let pending_htlc_info = PendingHTLCInfo {
+			outgoing_amt_msat: amt_to_forward_msat, routing, ..payment.forward_info
+		};
+
+		let mut per_source_pending_forward = [(
+			payment.prev_short_channel_id,
+			payment.prev_funding_outpoint,
+			payment.prev_user_channel_id,
+			vec![(pending_htlc_info, payment.prev_htlc_id)]
+		)];
+		self.forward_htlcs(&mut per_source_pending_forward);
+		Ok(())
+	}
+
+	/// Fails the intercepted HTLC indicated by intercept_id. Should only be called in response to
+	/// an [`HTLCIntercepted`] event. See [`ChannelManager::forward_intercepted_htlc`].
+	///
+	/// Errors if the event was not handled in time, in which case the HTLC was automatically failed
+	/// backwards.
+	///
+	/// [`HTLCIntercepted`]: events::Event::HTLCIntercepted
+	pub fn fail_intercepted_htlc(&self, intercept_id: InterceptId) -> Result<(), APIError> {
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(&self.total_consistency_lock, &self.persistence_notifier);
+
+		let payment = self.pending_intercepted_htlcs.lock().unwrap().remove(&intercept_id)
+			.ok_or_else(|| APIError::APIMisuseError {
+				err: format!("Payment with InterceptId {:?} not found", intercept_id)
+			})?;
+
+		if let PendingHTLCRouting::Forward { short_channel_id, .. } = payment.forward_info.routing {
+			let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
+				short_channel_id: payment.prev_short_channel_id,
+				outpoint: payment.prev_funding_outpoint,
+				htlc_id: payment.prev_htlc_id,
+				incoming_packet_shared_secret: payment.forward_info.incoming_shared_secret,
+				phantom_shared_secret: None,
+			});
+
+			let failure_reason = HTLCFailReason::Reason { failure_code: 0x4000 | 10, data: Vec::new() };
+			let destination = HTLCDestination::UnknownNextHop { requested_forward_scid: short_channel_id };
+			self.fail_htlc_backwards_internal(htlc_source, &payment.forward_info.payment_hash, failure_reason, destination);
+		} else { unreachable!() } // Only `PendingHTLCRouting::Forward`s are intercepted
+
+		Ok(())
+	}
+
 	/// Processes HTLCs which are pending waiting on random forward delay.
 	///
 	/// Should only really ever be called in response to a PendingHTLCsForwardable event.
@@ -5772,6 +5869,23 @@ impl<M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelManager<M, T, K, F
 		}
 	}
 
+	/// Gets a fake short channel id for use in receiving intercepted payments. These fake scids are
+	/// used when constructing the route hints for HTLCs intended to be intercepted. See
+	/// [`ChannelManager::forward_intercepted_htlc`].
+	///
+	/// Note that this method is not guaranteed to return unique values, you may need to call it a few
+	/// times to get a unique scid.
+	pub fn get_intercept_scid(&self) -> u64 {
+		let best_block_height = self.best_block.read().unwrap().height();
+		let short_to_chan_info = self.short_to_chan_info.read().unwrap();
+		loop {
+			let scid_candidate = fake_scid::Namespace::Intercept.get_fake_scid(best_block_height, &self.genesis_hash, &self.fake_scid_rand_bytes, &self.keys_manager);
+			// Ensure the generated scid doesn't conflict with a real channel.
+			if short_to_chan_info.contains_key(&scid_candidate) { continue }
+			return scid_candidate
+		}
+	}
+
 	/// Gets inflight HTLC information by processing pending outbound payments that are in
 	/// our channels. May be used during pathfinding to account for in-use channel liquidity.
 	pub fn compute_inflight_htlcs(&self) -> InFlightHtlcs {
@@ -6155,7 +6269,6 @@ where
 					if height >= htlc.cltv_expiry - HTLC_FAIL_BACK_BUFFER {
 						let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
 						htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(height));
-
 						timed_out_htlcs.push((HTLCSource::PreviousHopData(htlc.prev_hop.clone()), payment_hash.clone(), HTLCFailReason::Reason {
 							failure_code: 0x4000 | 15,
 							data: htlc_msat_height_data
@@ -6165,6 +6278,29 @@ where
 				});
 				!htlcs.is_empty() // Only retain this entry if htlcs has at least one entry.
 			});
+
+			let mut intercepted_htlcs = self.pending_intercepted_htlcs.lock().unwrap();
+			intercepted_htlcs.retain(|_, htlc| {
+				if height >= htlc.forward_info.outgoing_cltv_value - HTLC_FAIL_BACK_BUFFER {
+					let prev_hop_data = HTLCSource::PreviousHopData(HTLCPreviousHopData {
+						short_channel_id: htlc.prev_short_channel_id,
+						htlc_id: htlc.prev_htlc_id,
+						incoming_packet_shared_secret: htlc.forward_info.incoming_shared_secret,
+						phantom_shared_secret: None,
+						outpoint: htlc.prev_funding_outpoint,
+					});
+
+					let requested_forward_scid /* intercept scid */ = match htlc.forward_info.routing {
+						PendingHTLCRouting::Forward { short_channel_id, .. } => short_channel_id,
+						_ => unreachable!(),
+					};
+					timed_out_htlcs.push((prev_hop_data, htlc.forward_info.payment_hash,
+							HTLCFailReason::Reason { failure_code: 0x2000 | 2, data: Vec::new() },
+							HTLCDestination::InvalidForward { requested_forward_scid }));
+					log_trace!(self.logger, "Timing out intercepted HTLC with requested forward scid {}", requested_forward_scid);
+					false
+				} else { true }
+			});
 		}
 
 		self.handle_init_event_channel_failures(failed_channels);