Adds DiscardFunding event

During the event of a channel close, if the funding transaction
is yet to be broadcasted then a DiscardFunding event is issued
along with the ChannelClose event.

lightning/src/ln/channel.rs

@@ -1901,6 +1901,15 @@ impl<Signer: Sign> Channel<Signer> {
 		Ok(())
 	}
 
+	/// Returns transaction if there is pending funding transaction that is yet to broadcast
+	pub fn unbroadcasted_funding(&self) -> Option<Transaction> {
+		 if self.channel_state & (ChannelState::FundingCreated as u32) != 0 {
+			 self.funding_transaction.clone()
+		 } else {
+			 None
+		 }
+	}
+
 	/// Returns a HTLCStats about inbound pending htlcs
 	fn get_inbound_pending_htlc_stats(&self) -> HTLCStats {
 		let mut stats = HTLCStats {

lightning/src/ln/channelmanager.rs

@@ -1326,6 +1326,18 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 		self.list_channels_with_filter(|&(_, ref channel)| channel.is_live())
 	}
 
+	/// Helper function that issues the channel close events
+	fn issue_channel_close_events(&self, channel: &Channel<Signer>, closure_reason: ClosureReason) {
+		let mut pending_events_lock = self.pending_events.lock().unwrap();
+		match channel.unbroadcasted_funding() {
+			Some(transaction) => {
+				pending_events_lock.push(events::Event::DiscardFunding { channel_id: channel.channel_id(), transaction })
+			},
+			None => {},
+		}
+		pending_events_lock.push(events::Event::ChannelClosed { channel_id: channel.channel_id(), reason: closure_reason });
+	}
+
 	fn close_channel_internal(&self, channel_id: &[u8; 32], target_feerate_sats_per_1000_weight: Option<u32>) -> Result<(), APIError> {
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(&self.total_consistency_lock, &self.persistence_notifier);
 
@@ -1372,12 +1384,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 								msg: channel_update
 							});
 						}
-						if let Ok(mut pending_events_lock) = self.pending_events.lock() {
-							pending_events_lock.push(events::Event::ChannelClosed {
-								channel_id: *channel_id,
-								reason: ClosureReason::HolderForceClosed
-							});
-						}
+						self.issue_channel_close_events(&channel, ClosureReason::HolderForceClosed);
 					}
 					break Ok(());
 				},
@@ -1468,13 +1475,12 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 				if let Some(short_id) = chan.get().get_short_channel_id() {
 					channel_state.short_to_id.remove(&short_id);
 				}
-				let mut pending_events_lock = self.pending_events.lock().unwrap();
 				if peer_node_id.is_some() {
 					if let Some(peer_msg) = peer_msg {
-						pending_events_lock.push(events::Event::ChannelClosed { channel_id: *channel_id, reason: ClosureReason::CounterpartyForceClosed { peer_msg: peer_msg.to_string() } });
+						self.issue_channel_close_events(chan.get(),ClosureReason::CounterpartyForceClosed { peer_msg: peer_msg.to_string() });
 					}
 				} else {
-					pending_events_lock.push(events::Event::ChannelClosed { channel_id: *channel_id, reason: ClosureReason::HolderForceClosed });
+					self.issue_channel_close_events(chan.get(),ClosureReason::HolderForceClosed);
 				}
 				chan.remove_entry().1
 			} else {
@@ -3574,7 +3580,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 					msg: update
 				});
 			}
-			self.pending_events.lock().unwrap().push(events::Event::ChannelClosed { channel_id: msg.channel_id,  reason: ClosureReason::CooperativeClosure });
+			self.issue_channel_close_events(&chan, ClosureReason::CooperativeClosure);
 		}
 		Ok(())
 	}
@@ -3986,7 +3992,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 								msg: update
 							});
 						}
-						self.pending_events.lock().unwrap().push(events::Event::ChannelClosed { channel_id: chan.channel_id(),  reason: ClosureReason::CommitmentTxConfirmed });
+						self.issue_channel_close_events(&chan, ClosureReason::CommitmentTxConfirmed);
 						pending_msg_events.push(events::MessageSendEvent::HandleError {
 							node_id: chan.get_counterparty_node_id(),
 							action: msgs::ErrorAction::SendErrorMessage {
@@ -4102,12 +4108,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 								});
 							}
 
-							if let Ok(mut pending_events_lock) = self.pending_events.lock() {
-								pending_events_lock.push(events::Event::ChannelClosed {
-									channel_id: *channel_id,
-									reason: ClosureReason::CooperativeClosure
-								});
-							}
+							self.issue_channel_close_events(chan, ClosureReason::CooperativeClosure);
 
 							log_info!(self.logger, "Broadcasting {}", log_tx!(tx));
 							self.tx_broadcaster.broadcast_transaction(&tx);
@@ -4529,7 +4530,7 @@ where
 							msg: update
 						});
 					}
-					self.pending_events.lock().unwrap().push(events::Event::ChannelClosed { channel_id: channel.channel_id(),  reason: ClosureReason::CommitmentTxConfirmed });
+					self.issue_channel_close_events(channel, ClosureReason::CommitmentTxConfirmed);
 					pending_msg_events.push(events::MessageSendEvent::HandleError {
 						node_id: channel.get_counterparty_node_id(),
 						action: msgs::ErrorAction::SendErrorMessage { msg: e },
@@ -4720,7 +4721,7 @@ impl<Signer: Sign, M: Deref , T: Deref , K: Deref , F: Deref , L: Deref >
 								msg: update
 							});
 						}
-						self.pending_events.lock().unwrap().push(events::Event::ChannelClosed { channel_id: chan.channel_id(),  reason: ClosureReason::DisconnectedPeer });
+						self.issue_channel_close_events(chan, ClosureReason::DisconnectedPeer);
 						false
 					} else {
 						true
@@ -4735,7 +4736,7 @@ impl<Signer: Sign, M: Deref , T: Deref , K: Deref , F: Deref , L: Deref >
 							if let Some(short_id) = chan.get_short_channel_id() {
 								short_to_id.remove(&short_id);
 							}
-							self.pending_events.lock().unwrap().push(events::Event::ChannelClosed { channel_id: chan.channel_id(),  reason: ClosureReason::DisconnectedPeer });
+							self.issue_channel_close_events(chan, ClosureReason::DisconnectedPeer);
 							return false;
 						} else {
 							no_channels_remain = false;

lightning/src/ln/functional_test_utils.rs

@@ -763,21 +763,29 @@ macro_rules! check_closed_broadcast {
 	}}
 }
 
-/// Check that a channel's closing channel event has been issued
+/// Check that a channel's closing channel events has been issued
 #[macro_export]
 macro_rules! check_closed_event {
-	($node: expr, $events: expr, $reason: expr) => {{
+	($node: expr, $events: expr, $reason: expr) => {
+		check_closed_event!($node, $events, $reason, false);
+	};
+	($node: expr, $events: expr, $reason: expr, $is_check_discard_funding: expr) => {{
 		let events = $node.node.get_and_clear_pending_events();
 		assert_eq!(events.len(), $events);
 		let expected_reason = $reason;
+		let mut issues_discard_funding = false;
 		for event in events {
 			match event {
 				Event::ChannelClosed { ref reason, .. } => {
 					assert_eq!(*reason, expected_reason);
 				},
+				Event::DiscardFunding { .. } => {
+					issues_discard_funding = true;
+				}
 				_ => panic!("Unexpected event"),
 			}
 		}
+		assert_eq!($is_check_discard_funding, issues_discard_funding);
 	}}
 }
 

lightning/src/ln/functional_tests.rs

@@ -8632,7 +8632,7 @@ fn test_pre_lockin_no_chan_closed_update() {
 	let channel_id = ::chain::transaction::OutPoint { txid: funding_created_msg.funding_txid, index: funding_created_msg.funding_output_index }.to_channel_id();
 	nodes[0].node.handle_error(&nodes[1].node.get_our_node_id(), &msgs::ErrorMessage { channel_id, data: "Hi".to_owned() });
 	assert!(nodes[0].chain_monitor.added_monitors.lock().unwrap().is_empty());
-	check_closed_event!(nodes[0], 1, ClosureReason::CounterpartyForceClosed { peer_msg: "Hi".to_string() });
+	check_closed_event!(nodes[0], 2, ClosureReason::CounterpartyForceClosed { peer_msg: "Hi".to_string() }, true);
 }
 
 #[test]

lightning/src/util/events.rs

@@ -30,6 +30,7 @@ use io;
 use prelude::*;
 use core::time::Duration;
 use core::ops::Deref;
+use bitcoin::Transaction;
 
 /// Some information provided on receipt of payment depends on whether the payment received is a
 /// spontaneous payment or a "conventional" lightning payment that's paying an invoice.
@@ -254,6 +255,14 @@ pub enum Event {
 		channel_id: [u8; 32],
 		/// The reason the channel was closed.
 		reason: ClosureReason
+	},
+	/// Used to indicate to the user that they can abandon the funding transaction and recycle the
+	/// inputs for another purpose.
+	DiscardFunding {
+		/// The channel_id of the channel which has been closed.
+		channel_id: [u8; 32],
+		/// The full transaction received from the user
+		transaction: Transaction
 	}
 }
 
@@ -340,6 +349,13 @@ impl Writeable for Event {
 					(2, reason, required)
 				});
 			},
+			&Event::DiscardFunding { ref channel_id, ref transaction } => {
+				11u8.write(writer)?;
+				write_tlv_fields!(writer, {
+					(0, channel_id, required),
+					(2, transaction, required)
+				})
+			},
 			// Note that, going forward, all new events must only write data inside of
 			// `write_tlv_fields`. Versions 0.0.101+ will ignore odd-numbered events that write
 			// data via `write_tlv_fields`.
@@ -471,6 +487,15 @@ impl MaybeReadable for Event {
 				if reason.is_none() { return Ok(None); }
 				Ok(Some(Event::ChannelClosed { channel_id, reason: reason.unwrap() }))
 			},
+			11u8 => {
+				let mut channel_id = [0; 32];
+				let mut transaction = Transaction{ version: 2, lock_time: 0, input: Vec::new(), output: Vec::new() };
+				read_tlv_fields!(reader, {
+					(0, channel_id, required),
+					(2, transaction, required),
+				});
+				Ok(Some(Event::DiscardFunding { channel_id, transaction } ))
+			},
 			// Versions prior to 0.0.100 did not ignore odd types, instead returning InvalidValue.
 			// Version 0.0.100 failed to properly ignore odd types, possibly resulting in corrupt
 			// reads.