Add RBF-bumping of preimage/timeout txn on remote HTLC outputs

Given they are only signed by us we can RBF at wish

Author: Antoine Riard

src/ln/channelmonitor.rs

@@ -2533,7 +2533,10 @@ impl ChannelMonitor {
 					inputs_witnesses_weight += Self::get_witnesses_weight(if !is_htlc { &[InputDescriptors::RevokedOutput] } else if script.len() == OFFERED_HTLC_SCRIPT_WEIGHT { &[InputDescriptors::RevokedOfferedHTLC] } else if script.len() == ACCEPTED_HTLC_SCRIPT_WEIGHT { &[InputDescriptors::RevokedReceivedHTLC] } else { &[] });
 					amt = *amount;
 				},
-				&TxMaterial::RemoteHTLC { .. } => {},
+				&TxMaterial::RemoteHTLC { ref preimage, ref amount, .. } => {
+					inputs_witnesses_weight += Self::get_witnesses_weight(if preimage.is_some() { &[InputDescriptors::OfferedHTLC] } else { &[InputDescriptors::ReceivedHTLC] });
+					amt = *amount;
+				},
 				&TxMaterial::LocalHTLC { .. } => {},
 			}
 		}
@@ -2564,7 +2567,20 @@ impl ChannelMonitor {
 					bumped_tx.input[i].witness.push(script.clone().into_bytes());
 					log_trace!(self, "Going to broadcast bumped Penalty Transaction {} claiming revoked {} output {} from {} with new feerate {}", bumped_tx.txid(), if !is_htlc { "to_local" } else if script.len() == OFFERED_HTLC_SCRIPT_WEIGHT { "offered" } else if script.len() == ACCEPTED_HTLC_SCRIPT_WEIGHT { "received" } else { "" }, vout, txid, new_feerate);
 				},
-				&TxMaterial::RemoteHTLC { .. } => {},
+				&TxMaterial::RemoteHTLC { ref script, ref key, ref preimage, ref amount } => {
+					let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
+					let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[0], &script, *amount)[..]);
+					let sig = self.secp_ctx.sign(&sighash, &key);
+					bumped_tx.input[0].witness.push(sig.serialize_der().to_vec());
+					bumped_tx.input[0].witness[0].push(SigHashType::All as u8);
+					if let &Some(preimage) = preimage {
+						bumped_tx.input[0].witness.push(preimage.clone().0.to_vec());
+					} else {
+						bumped_tx.input[0].witness.push(vec![0]);
+					}
+					bumped_tx.input[0].witness.push(script.clone().into_bytes());
+					log_trace!(self, "Going to broadcast bumped Claim Transaction {} claiming remote htlc output {} from {} with new feerate {}", bumped_tx.txid(), vout, txid, new_feerate);
+				},
 				&TxMaterial::LocalHTLC { .. } => {
 					//TODO : Given that Local Commitment Transaction and HTLC-Timeout/HTLC-Success are counter-signed by peer, we can't
 					// RBF them. Need a Lightning specs change and package relay modification :