Handle sign_counterparty_commitment failing during outb funding

If sign_counterparty_commitment fails (i.e. because the signer is
temporarily disconnected), this really indicates that we should
retry the message sending which required the signature later,
rather than force-closing the channel (which probably won't even
work if the signer is missing).

Here we add initial handling of sign_counterparty_commitment
failing during outbound channel funding, setting a new flag in
`ChannelContext` which indicates we should retry sending the
`funding_created` later. We don't yet add any ability to do that
retry.

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -736,6 +736,10 @@ pub(super) struct ChannelContext<SP: Deref> where SP::Target: SignerProvider {
 	/// This flag is set in such a case. Note that we don't need to persist this as we'll end up
 	/// setting it again as a side-effect of [`Channel::channel_reestablish`].
 	signer_pending_commitment_update: bool,
+	/// Similar to [`Self::signer_pending_commitment_update`] but we're waiting to send either a
+	/// [`msgs::FundingCreated`] or [`msgs::FundingSigned`] depending on if this channel is
+	/// outbound or inbound.
+	signer_pending_funding: bool,
 
 	// pending_update_fee is filled when sending and receiving update_fee.
 	//
@@ -5746,6 +5750,7 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 				monitor_pending_finalized_fulfills: Vec::new(),
 
 				signer_pending_commitment_update: false,
+				signer_pending_funding: false,
 
 				#[cfg(debug_assertions)]
 				holder_max_commitment_tx_output: Mutex::new((channel_value_satoshis * 1000 - push_msat, push_msat)),
@@ -5826,15 +5831,14 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 		})
 	}
 
-	/// If an Err is returned, it is a ChannelError::Close (for get_funding_created)
-	fn get_funding_created_signature<L: Deref>(&mut self, logger: &L) -> Result<Signature, ChannelError> where L::Target: Logger {
+	fn get_funding_created_signature<L: Deref>(&mut self, logger: &L) -> Result<Signature, ()> where L::Target: Logger {
 		let counterparty_keys = self.context.build_remote_transaction_keys();
 		let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
 		match &self.context.holder_signer {
 			// TODO (taproot|arik): move match into calling method for Taproot
 			ChannelSignerType::Ecdsa(ecdsa) => {
-				Ok(ecdsa.sign_counterparty_commitment(&counterparty_initial_commitment_tx, Vec::new(), &self.context.secp_ctx)
-					.map_err(|_| ChannelError::Close("Failed to get signatures for new commitment_signed".to_owned()))?.0)
+				ecdsa.sign_counterparty_commitment(&counterparty_initial_commitment_tx, Vec::new(), &self.context.secp_ctx)
+					.map(|(sig, _)| sig)
 			}
 		}
 	}
@@ -5847,7 +5851,7 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 	/// Do NOT broadcast the funding transaction until after a successful funding_signed call!
 	/// If an Err is returned, it is a ChannelError::Close.
 	pub fn get_funding_created<L: Deref>(mut self, funding_transaction: Transaction, funding_txo: OutPoint, logger: &L)
-	-> Result<(Channel<SP>, msgs::FundingCreated), (Self, ChannelError)> where L::Target: Logger {
+	-> Result<(Channel<SP>, Option<msgs::FundingCreated>), (Self, ChannelError)> where L::Target: Logger {
 		if !self.context.is_outbound() {
 			panic!("Tried to create outbound funding_created message on an inbound channel!");
 		}
@@ -5863,15 +5867,6 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 		self.context.channel_transaction_parameters.funding_outpoint = Some(funding_txo);
 		self.context.holder_signer.as_mut().provide_channel_parameters(&self.context.channel_transaction_parameters);
 
-		let signature = match self.get_funding_created_signature(logger) {
-			Ok(res) => res,
-			Err(e) => {
-				log_error!(logger, "Got bad signatures: {:?}!", e);
-				self.context.channel_transaction_parameters.funding_outpoint = None;
-				return Err((self, e));
-			}
-		};
-
 		let temporary_channel_id = self.context.channel_id;
 
 		// Now that we're past error-generating stuff, update our local state:
@@ -5889,20 +5884,27 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 
 		self.context.funding_transaction = Some(funding_transaction);
 
+		let funding_created = if let Ok(signature) = self.get_funding_created_signature(logger) {
+			Some(msgs::FundingCreated {
+				temporary_channel_id,
+				funding_txid: funding_txo.txid,
+				funding_output_index: funding_txo.index,
+				signature,
+				#[cfg(taproot)]
+				partial_signature_with_nonce: None,
+				#[cfg(taproot)]
+				next_local_nonce: None,
+			})
+		} else {
+			self.context.signer_pending_funding = true;
+			None
+		};
+
 		let channel = Channel {
 			context: self.context,
 		};
 
-		Ok((channel, msgs::FundingCreated {
-			temporary_channel_id,
-			funding_txid: funding_txo.txid,
-			funding_output_index: funding_txo.index,
-			signature,
-			#[cfg(taproot)]
-			partial_signature_with_nonce: None,
-			#[cfg(taproot)]
-			next_local_nonce: None,
-		}))
+		Ok((channel, funding_created))
 	}
 
 	fn get_initial_channel_type(config: &UserConfig, their_features: &InitFeatures) -> ChannelTypeFeatures {
@@ -6395,6 +6397,7 @@ impl<SP: Deref> InboundV1Channel<SP> where SP::Target: SignerProvider {
 				monitor_pending_finalized_fulfills: Vec::new(),
 
 				signer_pending_commitment_update: false,
+				signer_pending_funding: false,
 
 				#[cfg(debug_assertions)]
 				holder_max_commitment_tx_output: Mutex::new((msg.push_msat, msg.funding_satoshis * 1000 - msg.push_msat)),
@@ -7483,6 +7486,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 				monitor_pending_finalized_fulfills: monitor_pending_finalized_fulfills.unwrap(),
 
 				signer_pending_commitment_update: false,
+				signer_pending_funding: false,
 
 				pending_update_fee,
 				holding_cell_update_fee,
@@ -7754,7 +7758,7 @@ mod tests {
 		}]};
 		let funding_outpoint = OutPoint{ txid: tx.txid(), index: 0 };
 		let (mut node_a_chan, funding_created_msg) = node_a_chan.get_funding_created(tx.clone(), funding_outpoint, &&logger).map_err(|_| ()).unwrap();
-		let (_, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, best_block, &&keys_provider, &&logger).map_err(|_| ()).unwrap();
+		let (_, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg.unwrap(), best_block, &&keys_provider, &&logger).map_err(|_| ()).unwrap();
 
 		// Node B --> Node A: funding signed
 		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, &&logger).unwrap();
@@ -7881,7 +7885,7 @@ mod tests {
 		}]};
 		let funding_outpoint = OutPoint{ txid: tx.txid(), index: 0 };
 		let (mut node_a_chan, funding_created_msg) = node_a_chan.get_funding_created(tx.clone(), funding_outpoint, &&logger).map_err(|_| ()).unwrap();
-		let (mut node_b_chan, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, best_block, &&keys_provider, &&logger).map_err(|_| ()).unwrap();
+		let (mut node_b_chan, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg.unwrap(), best_block, &&keys_provider, &&logger).map_err(|_| ()).unwrap();
 
 		// Node B --> Node A: funding signed
 		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, &&logger).unwrap();
@@ -8069,7 +8073,7 @@ mod tests {
 		}]};
 		let funding_outpoint = OutPoint{ txid: tx.txid(), index: 0 };
 		let (mut node_a_chan, funding_created_msg) = node_a_chan.get_funding_created(tx.clone(), funding_outpoint, &&logger).map_err(|_| ()).unwrap();
-		let (_, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, best_block, &&keys_provider, &&logger).map_err(|_| ()).unwrap();
+		let (_, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg.unwrap(), best_block, &&keys_provider, &&logger).map_err(|_| ()).unwrap();
 
 		// Node B --> Node A: funding signed
 		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, &&logger).unwrap();

lightning/src/ln/channelmanager.rs

@@ -3488,7 +3488,7 @@ where
 
 		let mut peer_state_lock = peer_state_mutex.lock().unwrap();
 		let peer_state = &mut *peer_state_lock;
-		let (chan, msg) = match peer_state.channel_by_id.remove(temporary_channel_id) {
+		let (chan, msg_opt) = match peer_state.channel_by_id.remove(temporary_channel_id) {
 			Some(ChannelPhase::UnfundedOutboundV1(chan)) => {
 				let funding_txo = find_funding_output(&chan, &funding_transaction)?;
 
@@ -3527,10 +3527,12 @@ where
 				}),
 		};
 
-		peer_state.pending_msg_events.push(events::MessageSendEvent::SendFundingCreated {
-			node_id: chan.context.get_counterparty_node_id(),
-			msg,
-		});
+		if let Some(msg) = msg_opt {
+			peer_state.pending_msg_events.push(events::MessageSendEvent::SendFundingCreated {
+				node_id: chan.context.get_counterparty_node_id(),
+				msg,
+			});
+		}
 		match peer_state.channel_by_id.entry(chan.context.channel_id()) {
 			hash_map::Entry::Occupied(_) => {
 				panic!("Generated duplicate funding txid?");

lightning/src/ln/functional_tests.rs

@@ -8970,7 +8970,7 @@ fn test_duplicate_chan_id() {
 		}
 	};
 	check_added_monitors!(nodes[0], 0);
-	nodes[1].node.handle_funding_created(&nodes[0].node.get_our_node_id(), &funding_created);
+	nodes[1].node.handle_funding_created(&nodes[0].node.get_our_node_id(), &funding_created.unwrap());
 	// At this point we'll look up if the channel_id is present and immediately fail the channel
 	// without trying to persist the `ChannelMonitor`.
 	check_added_monitors!(nodes[1], 0);