Track message timeout ticks based on internal states

With the introduction of `has_pending_channel_update`, we can now
determine whether any messages are owed to irrevocably commit HTLC
updates based on the current channel state. We prefer using the channel
state, over manually tracking as previously done, to have a single
source of truth. We also gain the ability to expect to receive multiple
messages at once, which will become relevant with the quiescence
protocol, where we may be waiting on a counterparty `revoke_and_ack` and
`stfu`.

Author: wpaulino

lightning/src/ln/channel.rs

@@ -1142,9 +1142,8 @@ pub(crate) const MIN_AFFORDABLE_HTLC_COUNT: usize = 4;
 ///   * `EXPIRE_PREV_CONFIG_TICKS` = convergence_delay / tick_interval
 pub(crate) const EXPIRE_PREV_CONFIG_TICKS: usize = 5;
 
-/// The number of ticks that may elapse while we're waiting for a response to a
-/// [`msgs::RevokeAndACK`] or [`msgs::ChannelReestablish`] message before we attempt to disconnect
-/// them.
+/// The number of ticks that may elapse while we're waiting for a response before we attempt to
+/// disconnect them.
 ///
 /// See [`ChannelContext::sent_message_awaiting_response`] for more information.
 pub(crate) const DISCONNECT_PEER_AWAITING_RESPONSE_TICKS: usize = 2;
@@ -1826,16 +1825,14 @@ pub(super) struct ChannelContext<SP: Deref> where SP::Target: SignerProvider {
 	pub workaround_lnd_bug_4006: Option<msgs::ChannelReady>,
 
 	/// An option set when we wish to track how many ticks have elapsed while waiting for a response
-	/// from our counterparty after sending a message. If the peer has yet to respond after reaching
-	/// `DISCONNECT_PEER_AWAITING_RESPONSE_TICKS`, a reconnection should be attempted to try to
-	/// unblock the state machine.
+	/// from our counterparty after entering specific states. If the peer has yet to respond after
+	/// reaching `DISCONNECT_PEER_AWAITING_RESPONSE_TICKS`, a reconnection should be attempted to
+	/// try to unblock the state machine.
 	///
-	/// This behavior is mostly motivated by a lnd bug in which we don't receive a message we expect
-	/// to in a timely manner, which may lead to channels becoming unusable and/or force-closed. An
-	/// example of such can be found at <https://github.com/lightningnetwork/lnd/issues/7682>.
-	///
-	/// This is currently only used when waiting for a [`msgs::ChannelReestablish`] or
-	/// [`msgs::RevokeAndACK`] message from the counterparty.
+	/// This behavior was initially motivated by a lnd bug in which we don't receive a message we
+	/// expect to in a timely manner, which may lead to channels becoming unusable and/or
+	/// force-closed. An example of such can be found at
+	/// <https://github.com/lightningnetwork/lnd/issues/7682>.
 	sent_message_awaiting_response: Option<usize>,
 
 	/// This channel's type, as negotiated during channel open
@@ -5928,7 +5925,7 @@ impl<SP: Deref> FundedChannel<SP> where
 		// OK, we step the channel here and *then* if the new generation fails we can fail the
 		// channel based on that, but stepping stuff here should be safe either way.
 		self.context.channel_state.clear_awaiting_remote_revoke();
-		self.context.sent_message_awaiting_response = None;
+		self.mark_response_received();
 		self.context.counterparty_prev_commitment_point = self.context.counterparty_cur_commitment_point;
 		self.context.counterparty_cur_commitment_point = Some(msg.next_per_commitment_point);
 		self.context.cur_counterparty_commitment_transaction_number -= 1;
@@ -6306,6 +6303,10 @@ impl<SP: Deref> FundedChannel<SP> where
 			return Err(())
 		}
 
+		// We only clear `peer_disconnected` if we were able to reestablish the channel. We always
+ 		// reset our awaiting response in case we failed reestablishment and are disconnecting.
+		self.context.sent_message_awaiting_response = None;
+
 		if self.context.channel_state.is_peer_disconnected() {
 			// While the below code should be idempotent, it's simpler to just return early, as
 			// redundant disconnect events can fire, though they should be rare.
@@ -6366,8 +6367,6 @@ impl<SP: Deref> FundedChannel<SP> where
 			}
 		}
 
-		self.context.sent_message_awaiting_response = None;
-
 		// Reset any quiescence-related state as it is implicitly terminated once disconnected.
 		match self.context.channel_state {
 			ChannelState::ChannelReady(_) => {
@@ -6500,10 +6499,6 @@ impl<SP: Deref> FundedChannel<SP> where
 			commitment_update = None;
 		}
 
-		if commitment_update.is_some() {
-			self.mark_awaiting_response();
-		}
-
 		self.context.monitor_pending_revoke_and_ack = false;
 		self.context.monitor_pending_commitment_signed = false;
 		let order = self.context.resend_order.clone();
@@ -6862,7 +6857,7 @@ impl<SP: Deref> FundedChannel<SP> where
 		// Go ahead and unmark PeerDisconnected as various calls we may make check for it (and all
 		// remaining cases either succeed or ErrorMessage-fail).
 		self.context.channel_state.clear_peer_disconnected();
-		self.context.sent_message_awaiting_response = None;
+		self.mark_response_received();
 
 		let shutdown_msg = self.get_outbound_shutdown();
 
@@ -6918,9 +6913,6 @@ impl<SP: Deref> FundedChannel<SP> where
 		// AwaitingRemoteRevoke set, which indicates we sent a commitment_signed but haven't gotten
 		// the corresponding revoke_and_ack back yet.
 		let is_awaiting_remote_revoke = self.context.channel_state.is_awaiting_remote_revoke();
-		if is_awaiting_remote_revoke && !self.is_awaiting_monitor_update() {
-			self.mark_awaiting_response();
-		}
 		let next_counterparty_commitment_number = INITIAL_COMMITMENT_NUMBER - self.context.cur_counterparty_commitment_transaction_number + if is_awaiting_remote_revoke { 1 } else { 0 };
 
 		let channel_ready = if msg.next_local_commitment_number == 1 && INITIAL_COMMITMENT_NUMBER - self.holder_commitment_point.transaction_number() == 1 {
@@ -7105,26 +7097,34 @@ impl<SP: Deref> FundedChannel<SP> where
 		Ok((closing_signed, None, None))
 	}
 
-	// Marks a channel as waiting for a response from the counterparty. If it's not received
-	// [`DISCONNECT_PEER_AWAITING_RESPONSE_TICKS`] after sending our own to them, then we'll attempt
-	// a reconnection.
-	fn mark_awaiting_response(&mut self) {
-		self.context.sent_message_awaiting_response = Some(0);
+	fn mark_response_received(&mut self) {
+		self.context.sent_message_awaiting_response = None;
 	}
 
 	/// Determines whether we should disconnect the counterparty due to not receiving a response
 	/// within our expected timeframe.
 	///
-	/// This should be called on every [`super::channelmanager::ChannelManager::timer_tick_occurred`].
+	/// This should be called for peers with an active socket on every
+	/// [`super::channelmanager::ChannelManager::timer_tick_occurred`].
 	pub fn should_disconnect_peer_awaiting_response(&mut self) -> bool {
-		let ticks_elapsed = if let Some(ticks_elapsed) = self.context.sent_message_awaiting_response.as_mut() {
-			ticks_elapsed
+		if let Some(ticks_elapsed) = self.context.sent_message_awaiting_response.as_mut() {
+			*ticks_elapsed += 1;
+			*ticks_elapsed >= DISCONNECT_PEER_AWAITING_RESPONSE_TICKS
+		} else if
+			// Cleared upon receiving `channel_reestablish`.
+			self.context.channel_state.is_peer_disconnected()
+			// Cleared upon receiving `revoke_and_ack`.
+			|| self.context.has_pending_channel_update(false)
+			|| self.context.has_pending_channel_update(true)
+		{
+			// This is the first tick we've seen after expecting to make forward progress.
+			self.context.sent_message_awaiting_response = Some(1);
+			debug_assert!(DISCONNECT_PEER_AWAITING_RESPONSE_TICKS > 1);
+			false
 		} else {
 			// Don't disconnect when we're not waiting on a response.
-			return false;
-		};
-		*ticks_elapsed += 1;
-		*ticks_elapsed >= DISCONNECT_PEER_AWAITING_RESPONSE_TICKS
+			false
+		}
 	}
 
 	pub fn shutdown(
@@ -8290,7 +8290,6 @@ impl<SP: Deref> FundedChannel<SP> where
 			log_info!(logger, "Sending a data_loss_protect with no previous remote per_commitment_secret for channel {}", &self.context.channel_id());
 			[0;32]
 		};
-		self.mark_awaiting_response();
 		msgs::ChannelReestablish {
 			channel_id: self.context.channel_id(),
 			// The protocol has two different commitment number concepts - the "commitment

lightning/src/ln/channelmanager.rs

@@ -6520,19 +6520,21 @@ where
 
 								funded_chan.context.maybe_expire_prev_config();
 
-								if funded_chan.should_disconnect_peer_awaiting_response() {
-									let logger = WithChannelContext::from(&self.logger, &funded_chan.context, None);
-									log_debug!(logger, "Disconnecting peer {} due to not making any progress on channel {}",
-											counterparty_node_id, chan_id);
-									pending_msg_events.push(MessageSendEvent::HandleError {
-										node_id: counterparty_node_id,
-										action: msgs::ErrorAction::DisconnectPeerWithWarning {
-											msg: msgs::WarningMessage {
-												channel_id: *chan_id,
-												data: "Disconnecting due to timeout awaiting response".to_owned(),
+								if peer_state.is_connected {
+									if funded_chan.should_disconnect_peer_awaiting_response() {
+										let logger = WithChannelContext::from(&self.logger, &funded_chan.context, None);
+										log_debug!(logger, "Disconnecting peer {} due to not making any progress on channel {}",
+												counterparty_node_id, chan_id);
+										pending_msg_events.push(MessageSendEvent::HandleError {
+											node_id: counterparty_node_id,
+											action: msgs::ErrorAction::DisconnectPeerWithWarning {
+												msg: msgs::WarningMessage {
+													channel_id: *chan_id,
+													data: "Disconnecting due to timeout awaiting response".to_owned(),
+												},
 											},
-										},
-									});
+										});
+									}
 								}
 
 								true