Merge pull request #878 from jkczyz/2026-04-lsp-max-in-flight

Drop `max_inbound_htlc_value_in_flight_percent_of_channel `

Author: tnull

Cargo.toml

@@ -40,18 +40,18 @@ default = []
 #lightning-macros = { version = "0.2.0" }
 #lightning-dns-resolver = { version = "0.3.0" }
 
-lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std"] }
-lightning-types = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
-lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std"] }
-lightning-net-tokio = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
-lightning-persister = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["tokio"] }
-lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
-lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
-lightning-block-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["rest-client", "rpc-client", "tokio"] }
-lightning-transaction-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["esplora-async-https", "time", "electrum-rustls-ring"] }
-lightning-liquidity = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std"] }
-lightning-macros = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
-lightning-dns-resolver = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
+lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std"] }
+lightning-types = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
+lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std"] }
+lightning-net-tokio = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
+lightning-persister = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["tokio"] }
+lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
+lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
+lightning-block-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["rest-client", "rpc-client", "tokio"] }
+lightning-transaction-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["esplora-async-https", "time", "electrum-rustls-ring"] }
+lightning-liquidity = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std"] }
+lightning-macros = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
+lightning-dns-resolver = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
 
 bdk_chain = { version = "0.23.0", default-features = false, features = ["std"] }
 bdk_esplora = { version = "0.22.0", default-features = false, features = ["async-https-rustls", "tokio"]}
@@ -81,13 +81,13 @@ async-trait = { version = "0.1", default-features = false }
 vss-client = { package = "vss-client-ng", version = "0.5" }
 prost = { version = "0.11.6", default-features = false}
 #bitcoin-payment-instructions = { version = "0.6" }
-bitcoin-payment-instructions = { git = "https://github.com/jkczyz/bitcoin-payment-instructions", rev = "340c535a600f7c43bef4c9f910edac4085f2e70c" }
+bitcoin-payment-instructions = { git = "https://github.com/jkczyz/bitcoin-payment-instructions", rev = "679dac50cc0d81ec4d31da94b93d467e5308f16a" }
 
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3", features = ["winbase"] }
 
 [dev-dependencies]
-lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std", "_test_utils"] }
+lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std", "_test_utils"] }
 rand = { version = "0.9.2", default-features = false, features = ["std", "thread_rng", "os_rng"] }
 proptest = "1.0.0"
 regex = "1.5.6"

src/builder.rs

@@ -1666,11 +1666,6 @@ fn build_with_store_internal(
 
 		// If we act as an LSPS2 service, we allow forwarding to unannounced channels.
 		user_config.accept_forwards_to_priv_channels = true;
-
-		// If we act as an LSPS2 service, set the HTLC-value-in-flight to 100% of the channel value
-		// to ensure we can forward the initial payment.
-		user_config.channel_handshake_config.max_inbound_htlc_value_in_flight_percent_of_channel =
-			100;
 	}
 
 	if let Some(role) = async_payments_role {

src/event.rs

@@ -26,9 +26,7 @@ use lightning::ln::channelmanager::{PaymentId, TrustedChannelFeatures};
 use lightning::ln::types::ChannelId;
 use lightning::routing::gossip::NodeId;
 use lightning::sign::EntropySource;
-use lightning::util::config::{
-	ChannelConfigOverrides, ChannelConfigUpdate, ChannelHandshakeConfigUpdate,
-};
+use lightning::util::config::{ChannelConfigOverrides, ChannelConfigUpdate};
 use lightning::util::errors::APIError;
 use lightning::util::persist::KVStore;
 use lightning::util::ser::{Readable, ReadableArgs, Writeable, Writer};
@@ -1273,20 +1271,24 @@ where
 					if lsp_node_id == counterparty_node_id {
 						// When we're an LSPS2 client, allow claiming underpaying HTLCs as the LSP will skim off some fee. We'll
 						// check that they don't take too much before claiming.
-						//
-						// We also set maximum allowed inbound HTLC value in flight
-						// to 100%. We should eventually be able to set this on a per-channel basis, but for
-						// now we just bump the default for all channels.
 						channel_override_config = Some(ChannelConfigOverrides {
-							handshake_overrides: Some(ChannelHandshakeConfigUpdate {
-								max_inbound_htlc_value_in_flight_percent_of_channel: Some(100),
-								..Default::default()
-							}),
 							update_overrides: Some(ChannelConfigUpdate {
 								accept_underpaying_htlcs: Some(true),
 								..Default::default()
 							}),
+							..Default::default()
 						});
+
+						// LSPS2 channels are unannounced; rely on LDK's default of 100%
+						// inbound HTLC value-in-flight so the LSP can forward the initial
+						// payment in full.
+						debug_assert_eq!(
+							self.channel_manager
+								.get_current_config()
+								.channel_handshake_config
+								.unannounced_channel_max_inbound_htlc_value_in_flight_percentage,
+							100
+						);
 					}
 				}
 				let res = if allow_0conf {

src/lib.rs

@@ -1197,13 +1197,16 @@ impl Node {
 		let mut user_config = default_user_config(&self.config);
 		user_config.channel_handshake_config.announce_for_forwarding = announce_for_forwarding;
 		user_config.channel_config = (channel_config.unwrap_or_default()).clone().into();
-		// We set the max inflight to 100% for private channels.
-		// FIXME: LDK will default to this behavior soon, too, at which point we should drop this
-		// manual override.
+
+		// Unannounced channels rely on LDK's default of 100% inbound HTLC value-in-flight
+		// to support large initial payments via LSPS2.
 		if !announce_for_forwarding {
-			user_config
-				.channel_handshake_config
-				.max_inbound_htlc_value_in_flight_percent_of_channel = 100;
+			debug_assert_eq!(
+				user_config
+					.channel_handshake_config
+					.unannounced_channel_max_inbound_htlc_value_in_flight_percentage,
+				100
+			);
 		}
 
 		let push_msat = push_to_counterparty_msat.unwrap_or(0);

src/liquidity.rs

@@ -781,13 +781,16 @@ where
 
 				let mut config = self.channel_manager.get_current_config().clone();
 
-				// We set these LSP-specific values during Node building, here we're making sure it's actually set.
+				// If we act as an LSPS2 service, the HTLC-value-in-flight must be 100% of the
+				// channel value to ensure we can forward the initial payment. That cap only
+				// applies to unannounced channels, so the channel must also be unannounced.
 				debug_assert_eq!(
 					config
 						.channel_handshake_config
-						.max_inbound_htlc_value_in_flight_percent_of_channel,
+						.unannounced_channel_max_inbound_htlc_value_in_flight_percentage,
 					100
 				);
+				debug_assert!(!config.channel_handshake_config.announce_for_forwarding);
 				debug_assert!(config.accept_forwards_to_priv_channels);
 
 				// We set the forwarding fee to 0 for now as we're getting paid by the channel fee.