Move JIT parameters to BOLT11 payment_metadata

`LSPS2Parameters` should travel with generated JIT invoices and the
returned recipient onion metadata instead of living in a dedicated
`PaymentKind::Bolt11Jit` payment-store variant.

Store new JIT payments as `PaymentKind::Bolt11`, decode legacy
`PaymentKind::Bolt11Jit` records as `PaymentKind::Bolt11`, and reject
nonzero `counterparty_skimmed_fee_msat` unless valid BOLT11
`payment_metadata` proves the `LSPS2` fee is allowed.

Co-Authored-By: HAL 9000

Author: tnull

CHANGELOG.md

@@ -1,3 +1,9 @@
+# Pending
+
+## Compatibility Notes
+- Pending JIT-channel payments created before upgrading may fail after upgrade because the
+  prior LSPS2 fee-limit state stored in `PaymentKind::Bolt11Jit` is not migrated.
+
 # 0.7.0 - Dec. 3, 2025
 This seventh minor release introduces numerous new features, bug fixes, and API improvements. In particular, it adds support for channel Splicing, Async Payments, as well as sourcing chain data from a Bitcoin Core REST backend.
 
@@ -419,4 +425,3 @@ integrated LDK and BDK-based wallets.
 
 **Note:** This release is still considered experimental, should not be run in
 production, and no compatibility guarantees are given until the release of 0.1.
-

src/event.rs

@@ -50,6 +50,7 @@ use crate::payment::asynchronous::static_invoice_store::StaticInvoiceStore;
 use crate::payment::store::{
 	PaymentDetails, PaymentDetailsUpdate, PaymentDirection, PaymentKind, PaymentStatus,
 };
+use crate::payment::Bolt11PaymentMetadata;
 use crate::runtime::Runtime;
 use crate::types::{
 	CustomTlvRecord, DynStore, KeysManager, OnionMessenger, PaymentStore, Sweeper, Wallet,
@@ -581,6 +582,35 @@ where
 		}
 	}
 
+	fn fail_claimable_payment(
+		&self, payment_id: PaymentId, payment_hash: &PaymentHash,
+	) -> Result<(), ReplayEvent> {
+		self.channel_manager.fail_htlc_backwards(payment_hash);
+
+		let update = PaymentDetailsUpdate {
+			status: Some(PaymentStatus::Failed),
+			..PaymentDetailsUpdate::new(payment_id)
+		};
+		match self.payment_store.update(update) {
+			Ok(_) => Ok(()),
+			Err(e) => {
+				log_error!(self.logger, "Failed to access payment store: {}", e);
+				Err(ReplayEvent())
+			},
+		}
+	}
+
+	fn lsps2_max_total_opening_fee_msat(payment_metadata: &[u8], amount_msat: u64) -> Option<u64> {
+		let metadata = Bolt11PaymentMetadata::read(&mut &payment_metadata[..]).ok()?;
+		let lsps2_parameters = metadata.lsps2_parameters?;
+		lsps2_parameters.max_total_opening_fee_msat.or_else(|| {
+			lsps2_parameters.max_proportional_opening_fee_ppm_msat.and_then(|max_prop_fee| {
+				// If it's a variable amount payment, compute the actual fee.
+				compute_opening_fee(amount_msat, 0, max_prop_fee)
+			})
+		})
+	}
+
 	pub async fn handle_event(&self, event: LdkEvent) -> Result<(), ReplayEvent> {
 		match event {
 			LdkEvent::FundingGenerationReady {
@@ -694,7 +724,8 @@ where
 				..
 			} => {
 				let payment_id = PaymentId(payment_hash.0);
-				if let Some(info) = self.payment_store.get(&payment_id) {
+				let payment_info = self.payment_store.get(&payment_id);
+				if let Some(info) = payment_info.as_ref() {
 					if info.direction == PaymentDirection::Outbound {
 						log_info!(
 							self.logger,
@@ -717,14 +748,13 @@ where
 					}
 
 					if info.status == PaymentStatus::Succeeded
-						|| matches!(info.kind, PaymentKind::Spontaneous { .. })
+						|| matches!(&info.kind, PaymentKind::Spontaneous { .. })
 					{
-						let stored_preimage = match info.kind {
+						let stored_preimage = match &info.kind {
 							PaymentKind::Bolt11 { preimage, .. }
-							| PaymentKind::Bolt11Jit { preimage, .. }
 							| PaymentKind::Bolt12Offer { preimage, .. }
 							| PaymentKind::Bolt12Refund { preimage, .. }
-							| PaymentKind::Spontaneous { preimage, .. } => preimage,
+							| PaymentKind::Spontaneous { preimage, .. } => *preimage,
 							_ => None,
 						};
 
@@ -759,22 +789,28 @@ where
 							},
 						};
 					}
+				}
 
-					let max_total_opening_fee_msat = match info.kind {
-						PaymentKind::Bolt11Jit { lsp_fee_limits, .. } => {
-							lsp_fee_limits
-								.max_total_opening_fee_msat
-								.or_else(|| {
-									lsp_fee_limits.max_proportional_opening_fee_ppm_msat.and_then(
-										|max_prop_fee| {
-											// If it's a variable amount payment, compute the actual fee.
-											compute_opening_fee(amount_msat, 0, max_prop_fee)
-										},
-									)
-								})
-								.unwrap_or(0)
-						},
-						_ => 0,
+				if counterparty_skimmed_fee_msat > 0 {
+					let max_total_opening_fee_msat = match &purpose {
+						PaymentPurpose::Bolt11InvoicePayment { .. } => onion_fields
+							.as_ref()
+							.and_then(|fields| fields.payment_metadata.as_ref())
+							.and_then(|metadata| {
+								Self::lsps2_max_total_opening_fee_msat(metadata, amount_msat)
+							}),
+						_ => None,
+					};
+
+					let Some(max_total_opening_fee_msat) = max_total_opening_fee_msat else {
+						log_info!(
+							self.logger,
+							"Refusing inbound payment with hash {} as the counterparty withheld {}msat without valid BOLT11 LSPS2 payment metadata",
+							hex_utils::to_string(&payment_hash.0),
+							counterparty_skimmed_fee_msat,
+						);
+						self.fail_claimable_payment(payment_id, &payment_hash)?;
+						return Ok(());
 					};
 
 					if counterparty_skimmed_fee_msat > max_total_opening_fee_msat {
@@ -785,26 +821,13 @@ where
 							counterparty_skimmed_fee_msat,
 							max_total_opening_fee_msat,
 						);
-						self.channel_manager.fail_htlc_backwards(&payment_hash);
-
-						let update = PaymentDetailsUpdate {
-							hash: Some(Some(payment_hash)),
-							status: Some(PaymentStatus::Failed),
-							..PaymentDetailsUpdate::new(payment_id)
-						};
-						match self.payment_store.update(update) {
-							Ok(_) => return Ok(()),
-							Err(e) => {
-								log_error!(self.logger, "Failed to access payment store: {}", e);
-								return Err(ReplayEvent());
-							},
-						};
+						self.fail_claimable_payment(payment_id, &payment_hash)?;
+						return Ok(());
 					}
 
-					// If the LSP skimmed anything, update our stored payment.
-					if counterparty_skimmed_fee_msat > 0 {
-						match info.kind {
-							PaymentKind::Bolt11Jit { .. } => {
+					if let Some(info) = payment_info.as_ref() {
+						match &info.kind {
+							PaymentKind::Bolt11 { .. } => {
 								let update = PaymentDetailsUpdate {
 									counterparty_skimmed_fee_msat: Some(Some(counterparty_skimmed_fee_msat)),
 									..PaymentDetailsUpdate::new(payment_id)
@@ -817,16 +840,17 @@ where
 									},
 								};
 							}
-							_ => debug_assert!(false, "We only expect the counterparty to get away with withholding fees for JIT payments."),
+							_ => debug_assert!(false, "We only expect the counterparty to get away with withholding fees for BOLT11 payments."),
 						}
 					}
+				}
 
+				if let Some(info) = payment_info {
 					// If this is known by the store but ChannelManager doesn't know the preimage,
 					// the payment has been registered via `_for_hash` variants and needs to be manually claimed via
 					// user interaction.
 					match info.kind {
-						PaymentKind::Bolt11 { preimage, .. }
-						| PaymentKind::Bolt11Jit { preimage, .. } => {
+						PaymentKind::Bolt11 { preimage, .. } => {
 							if purpose.preimage().is_none() {
 								debug_assert!(
 									preimage.is_none(),
@@ -1897,8 +1921,44 @@ mod tests {
 
 	use super::*;
 	use crate::io::test_utils::InMemoryStore;
+	use crate::payment::store::LSPS2Parameters;
 	use crate::types::DynStoreWrapper;
 
+	#[test]
+	fn lsps2_payment_metadata_decodes_total_fee_limit() {
+		let metadata = Bolt11PaymentMetadata {
+			lsps2_parameters: Some(LSPS2Parameters {
+				max_total_opening_fee_msat: Some(42_000),
+				max_proportional_opening_fee_ppm_msat: None,
+			}),
+		};
+
+		assert_eq!(
+			EventHandler::<Arc<TestLogger>>::lsps2_max_total_opening_fee_msat(
+				&metadata.encode(),
+				100_000
+			),
+			Some(42_000)
+		);
+	}
+
+	#[test]
+	fn lsps2_payment_metadata_missing_or_malformed_limit_is_rejected() {
+		let empty_metadata = Bolt11PaymentMetadata { lsps2_parameters: None }.encode();
+
+		assert_eq!(
+			EventHandler::<Arc<TestLogger>>::lsps2_max_total_opening_fee_msat(
+				&empty_metadata,
+				100_000
+			),
+			None
+		);
+		assert_eq!(
+			EventHandler::<Arc<TestLogger>>::lsps2_max_total_opening_fee_msat(&[0xff], 100_000),
+			None
+		);
+	}
+
 	#[tokio::test]
 	async fn event_queue_persistence() {
 		let store: Arc<DynStore> = Arc::new(DynStoreWrapper(InMemoryStore::new()));

src/liquidity.rs

@@ -21,6 +21,7 @@ use lightning::ln::msgs::SocketAddress;
 use lightning::ln::types::ChannelId;
 use lightning::routing::router::{RouteHint, RouteHintHop};
 use lightning::sign::EntropySource;
+use lightning::util::ser::Writeable;
 use lightning_invoice::{Bolt11Invoice, Bolt11InvoiceDescription, InvoiceBuilder, RoutingFees};
 use lightning_liquidity::events::LiquidityEvent;
 use lightning_liquidity::lsps0::ser::{LSPSDateTime, LSPSRequestId};
@@ -41,6 +42,8 @@ use tokio::sync::oneshot;
 use crate::builder::BuildError;
 use crate::connection::ConnectionManager;
 use crate::logger::{log_debug, log_error, log_info, LdkLogger, Logger};
+use crate::payment::store::LSPS2Parameters;
+use crate::payment::Bolt11PaymentMetadata;
 use crate::runtime::Runtime;
 use crate::types::{
 	Broadcaster, ChannelManager, DynStore, KeysManager, LiquidityManager, PeerManager, Wallet,
@@ -1113,7 +1116,7 @@ where
 	pub(crate) async fn lsps2_receive_to_jit_channel(
 		&self, amount_msat: u64, description: &Bolt11InvoiceDescription, expiry_secs: u32,
 		max_total_lsp_fee_limit_msat: Option<u64>, payment_hash: Option<PaymentHash>,
-	) -> Result<(Bolt11Invoice, u64), Error> {
+	) -> Result<Bolt11Invoice, Error> {
 		let fee_response = self.lsps2_request_opening_fee_params().await?;
 
 		let (min_total_fee_msat, min_opening_params) = fee_response
@@ -1159,22 +1162,27 @@ where
 
 		let buy_response =
 			self.lsps2_send_buy_request(Some(amount_msat), min_opening_params).await?;
+		let lsps2_parameters = LSPS2Parameters {
+			max_total_opening_fee_msat: Some(min_total_fee_msat),
+			max_proportional_opening_fee_ppm_msat: None,
+		};
 		let invoice = self.lsps2_create_jit_invoice(
 			buy_response,
 			Some(amount_msat),
 			description,
 			expiry_secs,
 			payment_hash,
+			lsps2_parameters,
 		)?;
 
 		log_info!(self.logger, "JIT-channel invoice created: {}", invoice);
-		Ok((invoice, min_total_fee_msat))
+		Ok(invoice)
 	}
 
 	pub(crate) async fn lsps2_receive_variable_amount_to_jit_channel(
 		&self, description: &Bolt11InvoiceDescription, expiry_secs: u32,
 		max_proportional_lsp_fee_limit_ppm_msat: Option<u64>, payment_hash: Option<PaymentHash>,
-	) -> Result<(Bolt11Invoice, u64), Error> {
+	) -> Result<Bolt11Invoice, Error> {
 		let fee_response = self.lsps2_request_opening_fee_params().await?;
 
 		let (min_prop_fee_ppm_msat, min_opening_params) = fee_response
@@ -1207,16 +1215,21 @@ where
 		);
 
 		let buy_response = self.lsps2_send_buy_request(None, min_opening_params).await?;
+		let lsps2_parameters = LSPS2Parameters {
+			max_total_opening_fee_msat: None,
+			max_proportional_opening_fee_ppm_msat: Some(min_prop_fee_ppm_msat),
+		};
 		let invoice = self.lsps2_create_jit_invoice(
 			buy_response,
 			None,
 			description,
 			expiry_secs,
 			payment_hash,
+			lsps2_parameters,
 		)?;
 
 		log_info!(self.logger, "JIT-channel invoice created: {}", invoice);
-		Ok((invoice, min_prop_fee_ppm_msat))
+		Ok(invoice)
 	}
 
 	async fn lsps2_request_opening_fee_params(&self) -> Result<LSPS2FeeResponse, Error> {
@@ -1298,7 +1311,7 @@ where
 	fn lsps2_create_jit_invoice(
 		&self, buy_response: LSPS2BuyResponse, amount_msat: Option<u64>,
 		description: &Bolt11InvoiceDescription, expiry_secs: u32,
-		payment_hash: Option<PaymentHash>,
+		payment_hash: Option<PaymentHash>, lsps2_parameters: LSPS2Parameters,
 	) -> Result<Bolt11Invoice, Error> {
 		let lsps2_client = self.lsps2_client.as_ref().ok_or(Error::LiquiditySourceUnavailable)?;
 
@@ -1346,7 +1359,11 @@ where
 			.current_timestamp()
 			.min_final_cltv_expiry_delta(min_final_cltv_expiry_delta.into())
 			.expiry_time(Duration::from_secs(expiry_secs.into()))
-			.private_route(route_hint);
+			.private_route(route_hint)
+			.payment_metadata(
+				Bolt11PaymentMetadata { lsps2_parameters: Some(lsps2_parameters) }.encode(),
+			)
+			.require_payment_metadata();
 
 		if let Some(amount_msat) = amount_msat {
 			invoice_builder = invoice_builder.amount_milli_satoshis(amount_msat).basic_mpp();