Avoid persisting a ChannelManager after each timer tick and send update_channel re-enable messages

lightning/src/ln/channel.rs

@@ -248,18 +248,21 @@ const MULTI_STATE_FLAGS: u32 = BOTH_SIDES_SHUTDOWN_MASK | ChannelState::PeerDisc
 
 pub const INITIAL_COMMITMENT_NUMBER: u64 = (1 << 48) - 1;
 
-/// Liveness is called to fluctuate given peer disconnecton/monitor failures/closing.
-/// If channel is public, network should have a liveness view announced by us on a
-/// best-effort, which means we may filter out some status transitions to avoid spam.
-/// See further timer_tick_occurred.
-#[derive(PartialEq)]
-enum UpdateStatus {
-	/// Status has been gossiped.
-	Fresh,
-	/// Status has been changed.
-	DisabledMarked,
-	/// Status has been marked to be gossiped at next flush
+/// The "channel disabled" bit in channel_update must be set based on whether we are connected to
+/// our counterparty or not. However, we don't want to announce updates right away to avoid
+/// spamming the network with updates if the connection is flapping. Instead, we "stage" updates to
+/// our channel_update message and track the current state here.
+/// See implementation at [`super::channelmanager::ChannelManager::timer_tick_occurred`].
+#[derive(Clone, Copy, PartialEq)]
+pub(super) enum ChannelUpdateStatus {
+	/// We've announced the channel as enabled and are connected to our peer.
+	Enabled,
+	/// Our channel is no longer live, but we haven't announced the channel as disabled yet.
 	DisabledStaged,
+	/// Our channel is live again, but we haven't announced the channel as enabled yet.
+	EnabledStaged,
+	/// We've announced the channel as disabled.
+	Disabled,
 }
 
 /// An enum indicating whether the local or remote side offered a given HTLC.
@@ -416,7 +419,7 @@ pub(super) struct Channel<Signer: Sign> {
 
 	commitment_secrets: CounterpartyCommitmentSecrets,
 
-	network_sync: UpdateStatus,
+	channel_update_status: ChannelUpdateStatus,
 
 	// We save these values so we can make sure `next_local_commit_tx_fee_msat` and
 	// `next_remote_commit_tx_fee_msat` properly predict what the next commitment transaction fee will
@@ -617,7 +620,7 @@ impl<Signer: Sign> Channel<Signer> {
 
 			commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
-			network_sync: UpdateStatus::Fresh,
+			channel_update_status: ChannelUpdateStatus::Enabled,
 
 			#[cfg(any(test, feature = "fuzztarget"))]
 			next_local_commitment_tx_fee_info_cached: Mutex::new(None),
@@ -858,7 +861,7 @@ impl<Signer: Sign> Channel<Signer> {
 
 			commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
-			network_sync: UpdateStatus::Fresh,
+			channel_update_status: ChannelUpdateStatus::Enabled,
 
 			#[cfg(any(test, feature = "fuzztarget"))]
 			next_local_commitment_tx_fee_info_cached: Mutex::new(None),
@@ -3495,24 +3498,12 @@ impl<Signer: Sign> Channel<Signer> {
 		} else { false }
 	}
 
-	pub fn to_disabled_staged(&mut self) {
-		self.network_sync = UpdateStatus::DisabledStaged;
+	pub fn channel_update_status(&self) -> ChannelUpdateStatus {
+		self.channel_update_status
 	}
 
-	pub fn to_disabled_marked(&mut self) {
-		self.network_sync = UpdateStatus::DisabledMarked;
-	}
-
-	pub fn to_fresh(&mut self) {
-		self.network_sync = UpdateStatus::Fresh;
-	}
-
-	pub fn is_disabled_staged(&self) -> bool {
-		self.network_sync == UpdateStatus::DisabledStaged
-	}
-
-	pub fn is_disabled_marked(&self) -> bool {
-		self.network_sync == UpdateStatus::DisabledMarked
+	pub fn set_channel_update_status(&mut self, status: ChannelUpdateStatus) {
+		self.channel_update_status = status;
 	}
 
 	fn check_get_funding_locked(&mut self, height: u32) -> Option<msgs::FundingLocked> {
@@ -4375,6 +4366,31 @@ impl Readable for InboundHTLCRemovalReason {
 	}
 }
 
+impl Writeable for ChannelUpdateStatus {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+		// We only care about writing out the current state as it was announced, ie only either
+		// Enabled or Disabled. In the case of DisabledStaged, we most recently announced the
+		// channel as enabled, so we write 0. For EnabledStaged, we similarly write a 1.
+		match self {
+			ChannelUpdateStatus::Enabled => 0u8.write(writer)?,
+			ChannelUpdateStatus::DisabledStaged => 0u8.write(writer)?,
+			ChannelUpdateStatus::EnabledStaged => 1u8.write(writer)?,
+			ChannelUpdateStatus::Disabled => 1u8.write(writer)?,
+		}
+		Ok(())
+	}
+}
+
+impl Readable for ChannelUpdateStatus {
+	fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+		Ok(match <u8 as Readable>::read(reader)? {
+			0 => ChannelUpdateStatus::Enabled,
+			1 => ChannelUpdateStatus::Disabled,
+			_ => return Err(DecodeError::InvalidValue),
+		})
+	}
+}
+
 impl<Signer: Sign> Writeable for Channel<Signer> {
 	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
 		// Note that we write out as if remove_uncommitted_htlcs_and_mark_paused had just been
@@ -4568,6 +4584,8 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
 		self.counterparty_shutdown_scriptpubkey.write(writer)?;
 
 		self.commitment_secrets.write(writer)?;
+
+		self.channel_update_status.write(writer)?;
 		Ok(())
 	}
 }
@@ -4740,6 +4758,8 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
 		let counterparty_shutdown_scriptpubkey = Readable::read(reader)?;
 		let commitment_secrets = Readable::read(reader)?;
 
+		let channel_update_status = Readable::read(reader)?;
+
 		let mut secp_ctx = Secp256k1::new();
 		secp_ctx.seeded_randomize(&keys_source.get_secure_random_bytes());
 
@@ -4814,7 +4834,7 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
 
 			commitment_secrets,
 
-			network_sync: UpdateStatus::Fresh,
+			channel_update_status,
 
 			#[cfg(any(test, feature = "fuzztarget"))]
 			next_local_commitment_tx_fee_info_cached: Mutex::new(None),