From da5a839a22cdec7265e6c57c079dc998ea581a37 Mon Sep 17 00:00:00 2001
From: Elias Rohrer <dev@tnull.de>
Date: Fri, 21 Mar 2025 17:03:10 +0100
Subject: [PATCH] Allow forwarding to unannounced channels if LSP service is
 enabled

Previously, we'd always disallow forwarding to unannounced channels.
However, if we're acting as an LSP, we *should* allow forwarding to
unannounced channels.
---
 src/builder.rs                  |  8 ++++++++
 src/liquidity.rs                | 13 ++++++++-----
 tests/integration_tests_rust.rs | 16 ++++++++++++++++
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/builder.rs b/src/builder.rs
index 7ab2ff889..c8fb848fc 100644
--- a/src/builder.rs
+++ b/src/builder.rs
@@ -1090,6 +1090,14 @@ fn build_with_store_internal(
 		// If we act as an LSPS2 service, we need to to be able to intercept HTLCs and forward the
 		// information to the service handler.
 		user_config.accept_intercept_htlcs = true;
+
+		// If we act as an LSPS2 service, we allow forwarding to unnannounced 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;
 	}
 
 	let message_router =
diff --git a/src/liquidity.rs b/src/liquidity.rs
index a7751026b..a47c23c81 100644
--- a/src/liquidity.rs
+++ b/src/liquidity.rs
@@ -675,11 +675,14 @@ where
 
 				let mut config = *self.channel_manager.get_current_default_configuration();
 
-				// Set the HTLC-value-in-flight to 100% of the channel value to ensure we can
-				// forward the payment.
-				config
-					.channel_handshake_config
-					.max_inbound_htlc_value_in_flight_percent_of_channel = 100;
+				// We set these LSP-specific values during Node building, here we're making sure it's actually set.
+				debug_assert_eq!(
+					config
+						.channel_handshake_config
+						.max_inbound_htlc_value_in_flight_percent_of_channel,
+					100
+				);
+				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.
 				//
diff --git a/tests/integration_tests_rust.rs b/tests/integration_tests_rust.rs
index 8dc0ca50a..3c406a3a9 100644
--- a/tests/integration_tests_rust.rs
+++ b/tests/integration_tests_rust.rs
@@ -1145,6 +1145,22 @@ fn lsps2_client_service_integration() {
 		(expected_received_amount_msat + expected_channel_overprovisioning_msat) / 1000;
 	let channel_value_sats = client_node.list_channels().first().unwrap().channel_value_sats;
 	assert_eq!(channel_value_sats, expected_channel_size_sat);
+
+	println!("Generating regular invoice!");
+	let invoice_description =
+		Bolt11InvoiceDescription::Direct(Description::new(String::from("asdf")).unwrap());
+	let amount_msat = 5_000_000;
+	let invoice = client_node
+		.bolt11_payment()
+		.receive(amount_msat, &invoice_description.into(), 1024)
+		.unwrap();
+
+	// Have the payer_node pay the invoice, to check regular forwards service_node -> client_node
+	// are working as expected.
+	println!("Paying regular invoice!");
+	let payment_id = payer_node.bolt11_payment().send(&invoice, None).unwrap();
+	expect_payment_successful_event!(payer_node, Some(payment_id), None);
+	expect_payment_received_event!(client_node, amount_msat);
 }
 
 #[test]