Make create_blinded_payment_paths methods amount optional.

Useful for creating payment paths for static invoices which are typically
amount-less.

Author: valentinewallace

fuzz/src/chanmon_consistency.rs

@@ -127,7 +127,7 @@ impl Router for FuzzRouter {
 
 	fn create_blinded_payment_paths<T: secp256k1::Signing + secp256k1::Verification>(
 		&self, _recipient: PublicKey, _first_hops: Vec<ChannelDetails>, _tlvs: ReceiveTlvs,
-		_amount_msats: u64, _secp_ctx: &Secp256k1<T>,
+		_amount_msats: Option<u64>, _secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPaymentPath>, ()> {
 		unreachable!()
 	}

fuzz/src/full_stack.rs

@@ -162,7 +162,7 @@ impl Router for FuzzRouter {
 
 	fn create_blinded_payment_paths<T: secp256k1::Signing + secp256k1::Verification>(
 		&self, _recipient: PublicKey, _first_hops: Vec<ChannelDetails>, _tlvs: ReceiveTlvs,
-		_amount_msats: u64, _secp_ctx: &Secp256k1<T>,
+		_amount_msats: Option<u64>, _secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPaymentPath>, ()> {
 		unreachable!()
 	}

lightning/src/ln/channelmanager.rs

@@ -9748,7 +9748,7 @@ where
 			Ok((payment_hash, payment_secret)) => {
 				let payment_context = PaymentContext::Bolt12Refund(Bolt12RefundContext {});
 				let payment_paths = self.create_blinded_payment_paths(
-					amount_msats, payment_secret, payment_context
+					Some(amount_msats), payment_secret, payment_context
 				)
 					.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 
@@ -10055,7 +10055,7 @@ where
 	/// Creates multi-hop blinded payment paths for the given `amount_msats` by delegating to
 	/// [`Router::create_blinded_payment_paths`].
 	fn create_blinded_payment_paths(
-		&self, amount_msats: u64, payment_secret: PaymentSecret, payment_context: PaymentContext
+		&self, amount_msats: Option<u64>, payment_secret: PaymentSecret, payment_context: PaymentContext
 	) -> Result<Vec<BlindedPaymentPath>, ()> {
 		let secp_ctx = &self.secp_ctx;
 
@@ -11585,7 +11585,7 @@ where
 					invoice_request: invoice_request.fields(),
 				});
 				let payment_paths = match self.create_blinded_payment_paths(
-					amount_msats, payment_secret, payment_context
+					Some(amount_msats), payment_secret, payment_context
 				) {
 					Ok(payment_paths) => payment_paths,
 					Err(()) => {

lightning/src/routing/router.rs

@@ -95,7 +95,7 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref, ES: Deref, S: Deref, SP: Size
 		T: secp256k1::Signing + secp256k1::Verification
 	> (
 		&self, recipient: PublicKey, first_hops: Vec<ChannelDetails>, tlvs: ReceiveTlvs,
-		amount_msats: u64, secp_ctx: &Secp256k1<T>
+		amount_msats: Option<u64>, secp_ctx: &Secp256k1<T>
 	) -> Result<Vec<BlindedPaymentPath>, ()> {
 		// Limit the number of blinded paths that are computed.
 		const MAX_PAYMENT_PATHS: usize = 3;
@@ -104,6 +104,9 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref, ES: Deref, S: Deref, SP: Size
 		// recipient's node_id.
 		const MIN_PEER_CHANNELS: usize = 3;
 
+		const DEFAULT_AMT_MSAT: u64 = 100_000_000;
+		let amount_msats = amount_msats.unwrap_or(DEFAULT_AMT_MSAT);
+
 		let has_one_peer = first_hops
 			.first()
 			.map(|details| details.counterparty.node_id)
@@ -218,7 +221,7 @@ pub trait Router {
 		T: secp256k1::Signing + secp256k1::Verification
 	> (
 		&self, recipient: PublicKey, first_hops: Vec<ChannelDetails>, tlvs: ReceiveTlvs,
-		amount_msats: u64, secp_ctx: &Secp256k1<T>
+		amount_msats: Option<u64>, secp_ctx: &Secp256k1<T>
 	) -> Result<Vec<BlindedPaymentPath>, ()>;
 }
 

lightning/src/util/test_utils.rs

@@ -251,7 +251,7 @@ impl<'a> Router for TestRouter<'a> {
 		T: secp256k1::Signing + secp256k1::Verification
 	>(
 		&self, recipient: PublicKey, first_hops: Vec<ChannelDetails>, tlvs: ReceiveTlvs,
-		amount_msats: u64, secp_ctx: &Secp256k1<T>,
+		amount_msats: Option<u64>, secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPaymentPath>, ()> {
 		let mut expected_paths = self.next_blinded_payment_paths.lock().unwrap();
 		if expected_paths.is_empty() {