Expose the full set of outbound HTLCs from a ChannelMonitor

This expands the outbound-HTLC-listing support in `ChannelMonitor`
to include not only the set of outbound HTLCs which have not yet
been resolved but to also include the full set of HTLCs which the
`ChannelMonitor` is currently able to to or has already finalized.

This will be used in the next commit to fail-back HTLCs which were
removed from a channel in the ChannelMonitor but not in a Channel.
Using the existing `get_pending_outbound_htlcs` for this purpose is
subtly broken - if the channel is already closed, an HTLC fail may
have completed on chain and is no longer "pending" to the monitor,
but the fail event is still in the monitor waiting to be handed
back to the `ChannelMonitor` when polled.

Author: TheBlueMatt

lightning/src/chain/channelmonitor.rs

@@ -1828,12 +1828,60 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
 		res
 	}
 
+	/// Gets the set of outbound HTLCs which can be (or have been) resolved by this
+	/// `ChannelMonitor`. This is used to determine if an HTLC was removed from the channel prior
+	/// to the `ChannelManager` having been persisted.
+	///
+	/// This is similar to [`Self::get_pending_outbound_htlcs`] except it includes HTLCs which were
+	/// resolved by this `ChannelMonitor`.
+	pub(crate) fn get_all_current_outbound_htlcs(&self) -> HashMap<HTLCSource, HTLCOutputInCommitment> {
+		let mut res = HashMap::new();
+		// Just examine the available counterparty commitment transactions. See docs on
+		// `fail_unbroadcast_htlcs`, below, for justification.
+		let us = self.inner.lock().unwrap();
+		macro_rules! walk_counterparty_commitment {
+			($txid: expr) => {
+				if let Some(ref latest_outpoints) = us.counterparty_claimable_outpoints.get($txid) {
+					for &(ref htlc, ref source_option) in latest_outpoints.iter() {
+						if let &Some(ref source) = source_option {
+							res.insert((**source).clone(), htlc.clone());
+						}
+					}
+				}
+			}
+		}
+		if let Some(ref txid) = us.current_counterparty_commitment_txid {
+			walk_counterparty_commitment!(txid);
+		}
+		if let Some(ref txid) = us.prev_counterparty_commitment_txid {
+			walk_counterparty_commitment!(txid);
+		}
+		res
+	}
+
 	/// Gets the set of outbound HTLCs which are pending resolution in this channel.
 	/// This is used to reconstruct pending outbound payments on restart in the ChannelManager.
 	pub(crate) fn get_pending_outbound_htlcs(&self) -> HashMap<HTLCSource, HTLCOutputInCommitment> {
-		let mut res = HashMap::new();
 		let us = self.inner.lock().unwrap();
+		// We're only concerned with the confirmation count of HTLC transactions, and don't
+		// actually care how many confirmations a commitment transaction may or may not have. Thus,
+		// we look for either a FundingSpendConfirmation event or a funding_spend_confirmed.
+		let confirmed_txid = us.funding_spend_confirmed.or_else(|| {
+			us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
+				if let OnchainEvent::FundingSpendConfirmation { .. } = event.event {
+					Some(event.txid)
+				} else { None }
+			})
+		});
+
+		if confirmed_txid.is_none() {
+			// If we have not seen a commitment transaction on-chain (ie the channel is not yet
+			// closed), just get the full set.
+			mem::drop(us);
+			return self.get_all_current_outbound_htlcs();
+		}
 
+		let mut res = HashMap::new();
 		macro_rules! walk_htlcs {
 			($holder_commitment: expr, $htlc_iter: expr) => {
 				for (htlc, source) in $htlc_iter {
@@ -1869,54 +1917,22 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
 			}
 		}
 
-		// We're only concerned with the confirmation count of HTLC transactions, and don't
-		// actually care how many confirmations a commitment transaction may or may not have. Thus,
-		// we look for either a FundingSpendConfirmation event or a funding_spend_confirmed.
-		let confirmed_txid = us.funding_spend_confirmed.or_else(|| {
-			us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
-				if let OnchainEvent::FundingSpendConfirmation { .. } = event.event {
-					Some(event.txid)
+		let txid = confirmed_txid.unwrap();
+		if Some(txid) == us.current_counterparty_commitment_txid || Some(txid) == us.prev_counterparty_commitment_txid {
+			walk_htlcs!(false, us.counterparty_claimable_outpoints.get(&txid).unwrap().iter().filter_map(|(a, b)| {
+				if let &Some(ref source) = b {
+					Some((a, &**source))
 				} else { None }
-			})
-		});
-		if let Some(txid) = confirmed_txid {
-			if Some(txid) == us.current_counterparty_commitment_txid || Some(txid) == us.prev_counterparty_commitment_txid {
-				walk_htlcs!(false, us.counterparty_claimable_outpoints.get(&txid).unwrap().iter().filter_map(|(a, b)| {
-					if let &Some(ref source) = b {
-						Some((a, &**source))
-					} else { None }
-				}));
-			} else if txid == us.current_holder_commitment_tx.txid {
-				walk_htlcs!(true, us.current_holder_commitment_tx.htlc_outputs.iter().filter_map(|(a, _, c)| {
+			}));
+		} else if txid == us.current_holder_commitment_tx.txid {
+			walk_htlcs!(true, us.current_holder_commitment_tx.htlc_outputs.iter().filter_map(|(a, _, c)| {
+				if let Some(source) = c { Some((a, source)) } else { None }
+			}));
+		} else if let Some(prev_commitment) = &us.prev_holder_signed_commitment_tx {
+			if txid == prev_commitment.txid {
+				walk_htlcs!(true, prev_commitment.htlc_outputs.iter().filter_map(|(a, _, c)| {
 					if let Some(source) = c { Some((a, source)) } else { None }
 				}));
-			} else if let Some(prev_commitment) = &us.prev_holder_signed_commitment_tx {
-				if txid == prev_commitment.txid {
-					walk_htlcs!(true, prev_commitment.htlc_outputs.iter().filter_map(|(a, _, c)| {
-						if let Some(source) = c { Some((a, source)) } else { None }
-					}));
-				}
-			}
-		} else {
-			// If we have not seen a commitment transaction on-chain (ie the channel is not yet
-			// closed), just examine the available counterparty commitment transactions. See docs
-			// on `fail_unbroadcast_htlcs`, below, for justification.
-			macro_rules! walk_counterparty_commitment {
-				($txid: expr) => {
-					if let Some(ref latest_outpoints) = us.counterparty_claimable_outpoints.get($txid) {
-						for &(ref htlc, ref source_option) in latest_outpoints.iter() {
-							if let &Some(ref source) = source_option {
-								res.insert((**source).clone(), htlc.clone());
-							}
-						}
-					}
-				}
-			}
-			if let Some(ref txid) = us.current_counterparty_commitment_txid {
-				walk_counterparty_commitment!(txid);
-			}
-			if let Some(ref txid) = us.prev_counterparty_commitment_txid {
-				walk_counterparty_commitment!(txid);
 			}
 		}