Make our in-flight limit percentage configurable

Author: ViktorTigerstrom

lightning/src/ln/channel.rs

@@ -789,8 +789,13 @@ macro_rules! secp_check {
 
 impl<Signer: Sign> Channel<Signer> {
 	// Convert constants + channel value to limits:
-	fn get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis: u64) -> u64 {
-		channel_value_satoshis * 1000 / 10 //TODO
+	fn get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis: u64, config: ChannelConfig) -> u64 {
+		channel_value_satoshis * 10 * u64::from(config.holder_max_htlc_value_in_flight_msat_channel_value_percent)
+	}
+
+	fn config_htlc_in_flight_value_is_valid(config: ChannelConfig) -> bool {
+		let htlc_in_flight_value = config.holder_max_htlc_value_in_flight_msat_channel_value_percent;
+		htlc_in_flight_value >= 1 && htlc_in_flight_value <= 100
 	}
 
 	/// Returns a minimum channel reserve value the remote needs to maintain,
@@ -865,6 +870,13 @@ impl<Signer: Sign> Channel<Signer> {
 			return Err(APIError::APIMisuseError { err: format!("Holder selected channel  reserve below implemention limit dust_limit_satoshis {}", holder_selected_channel_reserve_satoshis) });
 		}
 
+		// Check that config has valid values set
+		if !Self::config_htlc_in_flight_value_is_valid(config.channel_options){
+			return Err(APIError::APIMisuseError { err:format!(
+				"UserConfig::channel_options::holder_max_htlc_value_in_flight_msat_channel_value_percent must be set to a value between 1-100. Current value set ({})",
+				config.channel_options.holder_max_htlc_value_in_flight_msat_channel_value_percent)});
+		}
+
 		let feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Normal);
 
 		let value_to_self_msat = channel_value_satoshis * 1000 - push_msat;
@@ -946,7 +958,7 @@ impl<Signer: Sign> Channel<Signer> {
 			counterparty_dust_limit_satoshis: 0,
 			holder_dust_limit_satoshis: MIN_CHAN_DUST_LIMIT_SATOSHIS,
 			counterparty_max_htlc_value_in_flight_msat: 0,
-			holder_max_htlc_value_in_flight_msat: Self::get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis),
+			holder_max_htlc_value_in_flight_msat: Self::get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis, config.channel_options),
 			counterparty_selected_channel_reserve_satoshis: None, // Filled in in accept_channel
 			holder_selected_channel_reserve_satoshis,
 			counterparty_htlc_minimum_msat: 0,
@@ -1129,6 +1141,13 @@ impl<Signer: Sign> Channel<Signer> {
 			return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is greater than the implementation limit ({})", msg.dust_limit_satoshis, MAX_CHAN_DUST_LIMIT_SATOSHIS)));
 		}
 
+		// Check that config has valid values set
+		if !Self::config_htlc_in_flight_value_is_valid(config.channel_options){
+			return Err(ChannelError::Close(format!(
+				"UserConfig::channel_options::holder_max_htlc_value_in_flight_msat_channel_value_percent must be set to a value between 1-100. Current value set ({})",
+				config.channel_options.holder_max_htlc_value_in_flight_msat_channel_value_percent)));
+		}
+
 		// Convert things into internal flags and prep our state:
 
 		if config.peer_channel_config_limits.force_announced_channel_preference {
@@ -1259,7 +1278,7 @@ impl<Signer: Sign> Channel<Signer> {
 			counterparty_dust_limit_satoshis: msg.dust_limit_satoshis,
 			holder_dust_limit_satoshis: MIN_CHAN_DUST_LIMIT_SATOSHIS,
 			counterparty_max_htlc_value_in_flight_msat: cmp::min(msg.max_htlc_value_in_flight_msat, msg.funding_satoshis * 1000),
-			holder_max_htlc_value_in_flight_msat: Self::get_holder_max_htlc_value_in_flight_msat(msg.funding_satoshis),
+			holder_max_htlc_value_in_flight_msat: Self::get_holder_max_htlc_value_in_flight_msat(msg.funding_satoshis, config.channel_options),
 			counterparty_selected_channel_reserve_satoshis: Some(msg.channel_reserve_satoshis),
 			holder_selected_channel_reserve_satoshis,
 			counterparty_htlc_minimum_msat: msg.htlc_minimum_msat,
@@ -5855,13 +5874,14 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
 		let chan_type = if self.channel_type != ChannelTypeFeatures::only_static_remote_key() {
 			Some(&self.channel_type) } else { None };
 
-		// The same logic applies for `holder_selected_channel_reserve_satoshis` and
-		// `holder_max_htlc_value_in_flight_msat` values other than the defaults.
+		// The same logic applies for `holder_selected_channel_reserve_satoshis` values other than
+		// the default, and when `holder_max_htlc_value_in_flight_msat` has a different value then
+		// the result of `get_holder_max_htlc_value_in_flight_msat` with the set channel `config`.
 		let serialized_holder_selected_reserve =
 			if self.holder_selected_channel_reserve_satoshis != Self::get_holder_selected_channel_reserve_satoshis(self.channel_value_satoshis)
 			{ Some(self.holder_selected_channel_reserve_satoshis) } else { None };
 		let serialized_holder_htlc_max_in_flight =
-			if self.holder_max_htlc_value_in_flight_msat != Self::get_holder_max_htlc_value_in_flight_msat(self.channel_value_satoshis)
+			if self.holder_max_htlc_value_in_flight_msat != Self::get_holder_max_htlc_value_in_flight_msat(self.channel_value_satoshis, self.config)
 			{ Some(self.holder_max_htlc_value_in_flight_msat) } else { None };
 
 		write_tlv_fields!(writer, {
@@ -6131,7 +6151,6 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<(&'a K, u32)> for Channel<Signer>
 		let mut target_closing_feerate_sats_per_kw = None;
 		let mut monitor_pending_finalized_fulfills = Some(Vec::new());
 		let mut holder_selected_channel_reserve_satoshis = Some(Self::get_holder_selected_channel_reserve_satoshis(channel_value_satoshis));
-		let mut holder_max_htlc_value_in_flight_msat = Some(Self::get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis));
 		// Prior to supporting channel type negotiation, all of our channels were static_remotekey
 		// only, so we default to that if none was written.
 		let mut channel_type = Some(ChannelTypeFeatures::only_static_remote_key());
@@ -6143,6 +6162,7 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<(&'a K, u32)> for Channel<Signer>
 		let mut announcement_sigs_state = Some(AnnouncementSigsState::NotSent);
 		let mut latest_inbound_scid_alias = None;
 		let mut outbound_scid_alias = None;
+		let mut tlv_holder_max_htlc_value_in_flight_msat = None;
 
 		read_tlv_fields!(reader, {
 			(0, announcement_sigs, option),
@@ -6151,7 +6171,7 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<(&'a K, u32)> for Channel<Signer>
 			(3, counterparty_selected_channel_reserve_satoshis, option),
 			(4, holder_selected_channel_reserve_satoshis, option),
 			(5, config, option), // Note that if none is provided we will *not* overwrite the existing one.
-			(6, holder_max_htlc_value_in_flight_msat, option),
+			(6, tlv_holder_max_htlc_value_in_flight_msat, option),
 			(7, shutdown_scriptpubkey, option),
 			(9, target_closing_feerate_sats_per_kw, option),
 			(11, monitor_pending_finalized_fulfills, vec_type),
@@ -6162,6 +6182,18 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<(&'a K, u32)> for Channel<Signer>
 			(21, outbound_scid_alias, option),
 		});
 
+		// Note that we need to call `get_holder_max_htlc_value_in_flight_msat` after the tlv
+		// fields have been read, as
+		// `config.holder_max_htlc_value_in_flight_msat_channel_value_percent` always will have the
+		// default value prior to that.
+		// If `tlv_holder_max_htlc_value_in_flight_msat` was set in the tlv fields, the
+		// `holder_max_htlc_value_in_flight_msat` was written with a different value then result of
+		// `get_holder_max_htlc_value_in_flight_msat` with the channel `config`, and the written
+		// value should therefore be used.
+		let holder_max_htlc_value_in_flight_msat = tlv_holder_max_htlc_value_in_flight_msat
+			.map(|max_htlc_value_in_flight| max_htlc_value_in_flight)
+			.or(Some(Self::get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis, config.unwrap())));
+
 		if let Some(preimages) = preimages_opt {
 			let mut iter = preimages.into_iter();
 			for htlc in pending_outbound_htlcs.iter_mut() {

lightning/src/util/config.rs

@@ -269,6 +269,13 @@ pub struct ChannelConfig {
 	/// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
 	/// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
 	pub force_close_avoidance_max_fee_satoshis: u64,
+	/// Sets how many the percent of the channel value the holder_max_htlc_value_in_flight_msat
+	/// will be assigned as.
+	///
+	/// Should be set to a value between 1-100, where the value signals the percantage to be used.
+	///
+	/// Default value: 10.
+	pub holder_max_htlc_value_in_flight_msat_channel_value_percent: u8,
 }
 
 impl Default for ChannelConfig {
@@ -282,6 +289,7 @@ impl Default for ChannelConfig {
 			commit_upfront_shutdown_pubkey: true,
 			max_dust_htlc_exposure_msat: 5_000_000,
 			force_close_avoidance_max_fee_satoshis: 1000,
+			holder_max_htlc_value_in_flight_msat_channel_value_percent: 10,
 		}
 	}
 }
@@ -292,6 +300,7 @@ impl_writeable_tlv_based!(ChannelConfig, {
 	(2, cltv_expiry_delta, required),
 	(3, force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
 	(4, announced_channel, required),
+	(5, holder_max_htlc_value_in_flight_msat_channel_value_percent, (default_value, 10)),
 	(6, commit_upfront_shutdown_pubkey, required),
 	(8, forwarding_fee_base_msat, required),
 });