Batch funding for v1 channel establishments

Author: wvanlint

lightning/src/events/mod.rs

@@ -168,6 +168,9 @@ pub enum ClosureReason {
 	/// The counterparty requested a cooperative close of a channel that had not been funded yet.
 	/// The channel has been immediately closed.
 	CounterpartyCoopClosedUnfundedChannel,
+	/// Another channel in the same funding batch closed before the funding transaction
+	/// was ready to be broadcast.
+	FundingBatchClosure,
 }
 
 impl core::fmt::Display for ClosureReason {
@@ -188,6 +191,7 @@ impl core::fmt::Display for ClosureReason {
 			ClosureReason::DisconnectedPeer => f.write_str("the peer disconnected prior to the channel being funded"),
 			ClosureReason::OutdatedChannelManager => f.write_str("the ChannelManager read from disk was stale compared to ChannelMonitor(s)"),
 			ClosureReason::CounterpartyCoopClosedUnfundedChannel => f.write_str("the peer requested the unfunded channel be closed"),
+			ClosureReason::FundingBatchClosure => f.write_str("another channel in the same funding batch closed"),
 		}
 	}
 }
@@ -202,6 +206,7 @@ impl_writeable_tlv_based_enum_upgradable!(ClosureReason,
 	(10, DisconnectedPeer) => {},
 	(12, OutdatedChannelManager) => {},
 	(13, CounterpartyCoopClosedUnfundedChannel) => {},
+	(15, FundingBatchClosure) => {}
 );
 
 /// Intended destination of a failed HTLC as indicated in [`Event::HTLCHandlingFailed`].

lightning/src/ln/channel.rs

@@ -301,6 +301,10 @@ enum ChannelState {
 	/// We've successfully negotiated a closing_signed dance. At this point ChannelManager is about
 	/// to drop us, but we store this anyway.
 	ShutdownComplete = 4096,
+	/// Flag which is set on `FundingSent` to indicate this channel is funded in a batch and the
+	/// broadcasting of the funding transaction is being held until all channels in the batch
+	/// have received funding_signed and have their monitors persisted.
+	WaitingForBatch = 1 << 13,
 }
 const BOTH_SIDES_SHUTDOWN_MASK: u32 = ChannelState::LocalShutdownSent as u32 | ChannelState::RemoteShutdownSent as u32;
 const MULTI_STATE_FLAGS: u32 = BOTH_SIDES_SHUTDOWN_MASK | ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateInProgress as u32;
@@ -1198,9 +1202,11 @@ impl<Signer: ChannelSigner> ChannelContext<Signer> {
 		did_channel_update
 	}
 
-	/// Returns true if funding_created was sent/received.
+	/// Returns true if funding_signed was sent/received and the
+	/// funding transaction has been broadcast if necessary.
 	pub fn is_funding_initiated(&self) -> bool {
-		self.channel_state >= ChannelState::FundingSent as u32
+		self.channel_state >= ChannelState::FundingSent as u32 &&
+		self.channel_state & ChannelState::WaitingForBatch as u32 == 0
 	}
 
 	/// Transaction nomenclature is somewhat confusing here as there are many different cases - a
@@ -1940,7 +1946,8 @@ impl<Signer: ChannelSigner> ChannelContext<Signer> {
 
 	/// 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 {
+		if self.channel_state & ChannelState::FundingCreated as u32 != 0 ||
+				self.channel_state & ChannelState::WaitingForBatch as u32 != 0 {
 			self.funding_transaction.clone()
 		} else {
 			None
@@ -2487,7 +2494,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 	/// Handles a funding_signed message from the remote end.
 	/// If this call is successful, broadcast the funding transaction (and not before!)
 	pub fn funding_signed<SP: Deref, L: Deref>(
-		&mut self, msg: &msgs::FundingSigned, best_block: BestBlock, signer_provider: &SP, logger: &L
+		&mut self, msg: &msgs::FundingSigned, best_block: BestBlock, signer_provider: &SP, is_batch_funding: bool, logger: &L
 	) -> Result<ChannelMonitor<Signer>, ChannelError>
 	where
 		SP::Target: SignerProvider<Signer = Signer>,
@@ -2557,7 +2564,11 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 		channel_monitor.provide_latest_counterparty_commitment_tx(counterparty_initial_bitcoin_tx.txid, Vec::new(), self.context.cur_counterparty_commitment_transaction_number, self.context.counterparty_cur_commitment_point.unwrap(), logger);
 
 		assert_eq!(self.context.channel_state & (ChannelState::MonitorUpdateInProgress as u32), 0); // We have no had any monitor(s) yet to fail update!
-		self.context.channel_state = ChannelState::FundingSent as u32;
+		if is_batch_funding {
+			self.context.channel_state = ChannelState::FundingSent as u32 | ChannelState::WaitingForBatch as u32;
+		} else {
+			self.context.channel_state = ChannelState::FundingSent as u32;
+		}
 		self.context.cur_holder_commitment_transaction_number -= 1;
 		self.context.cur_counterparty_commitment_transaction_number -= 1;
 
@@ -2568,6 +2579,13 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 		Ok(channel_monitor)
 	}
 
+	/// Updates the state of the channel to indicate that all channels in the batch
+	/// have received funding_signed and persisted their monitors.
+	/// The funding transaction is consequently allowed to be broadcast.
+	pub fn set_batch_ready(&mut self) {
+		self.context.channel_state &= !(ChannelState::WaitingForBatch as u32);
+	}
+
 	/// Handles a channel_ready message from our peer. If we've already sent our channel_ready
 	/// and the channel is now usable (and public), this may generate an announcement_signatures to
 	/// reply with.
@@ -3656,7 +3674,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 		// (re-)broadcast the funding transaction as we may have declined to broadcast it when we
 		// first received the funding_signed.
 		let mut funding_broadcastable =
-			if self.context.is_outbound() && self.context.channel_state & !MULTI_STATE_FLAGS >= ChannelState::FundingSent as u32 {
+			if self.context.is_outbound() && self.context.channel_state & !MULTI_STATE_FLAGS >= ChannelState::FundingSent as u32 && self.context.channel_state & ChannelState::WaitingForBatch as u32 == 0 {
 				self.context.funding_transaction.take()
 			} else { None };
 		// That said, if the funding transaction is already confirmed (ie we're active with a
@@ -7642,7 +7660,7 @@ mod tests {
 		let (_, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, 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();
+		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, false, &&logger).unwrap();
 
 		// Put some inbound and outbound HTLCs in A's channel.
 		let htlc_amount_msat = 11_092_000; // put an amount below A's effective dust limit but above B's.
@@ -7769,7 +7787,7 @@ mod tests {
 		let (mut node_b_chan, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, 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();
+		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, false, &&logger).unwrap();
 
 		// Now disconnect the two nodes and check that the commitment point in
 		// Node B's channel_reestablish message is sane.
@@ -7957,7 +7975,7 @@ mod tests {
 		let (_, funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, 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();
+		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, false, &&logger).unwrap();
 
 		// Make sure that receiving a channel update will update the Channel as expected.
 		let update = ChannelUpdate {