Use RouteParametersConfig to create new RouteParameters

- This finally allow overriding the {Route, Payment} parameters with the
  RouteParametersConfig value provided by the user.

Author: shaavan

lightning/src/ln/outbound_payment.rs

@@ -863,15 +863,15 @@ impl OutboundPayments {
 		SP: Fn(SendAlongPathArgs) -> Result<(), APIError>,
 	{
 		let payment_hash = invoice.payment_hash();
-		let max_total_routing_fee_msat;
+		let params_config;
 		let retry_strategy;
 		match self.pending_outbound_payments.lock().unwrap().entry(payment_id) {
 			hash_map::Entry::Occupied(entry) => match entry.get() {
 				PendingOutboundPayment::AwaitingInvoice {
 					retry_strategy: retry, route_params_config, ..
 				} => {
 					retry_strategy = *retry;
-					max_total_routing_fee_msat = route_params_config.max_total_routing_fee_msat;
+					params_config = *route_params_config;
 					*entry.into_mut() = PendingOutboundPayment::InvoiceReceived {
 						payment_hash,
 						retry_strategy: *retry,
@@ -891,9 +891,10 @@ impl OutboundPayments {
 		}
 
 		let mut route_params = RouteParameters::from_payment_params_and_value(
-			PaymentParameters::from_bolt12_invoice(&invoice), invoice.amount_msats()
+			PaymentParameters::from_bolt12_invoice(&invoice)
+				.with_user_config_ignoring_fee_limit(params_config), invoice.amount_msats()
 		);
-		if let Some(max_fee_msat) = max_total_routing_fee_msat {
+		if let Some(max_fee_msat) = params_config.max_total_routing_fee_msat {
 			route_params.max_total_routing_fee_msat = Some(max_fee_msat);
 		}
 		self.send_payment_for_bolt12_invoice_internal(
@@ -1066,7 +1067,8 @@ impl OutboundPayments {
 					};
 					let keysend_preimage = PaymentPreimage(entropy_source.get_secure_random_bytes());
 					let payment_hash = PaymentHash(Sha256::hash(&keysend_preimage.0).to_byte_array());
-					let pay_params = PaymentParameters::from_static_invoice(invoice);
+					let pay_params = PaymentParameters::from_static_invoice(invoice)
+						.with_user_config_ignoring_fee_limit(*route_params_config);
 					let mut route_params = RouteParameters::from_payment_params_and_value(pay_params, amount_msat);
 					route_params.max_total_routing_fee_msat = route_params_config.max_total_routing_fee_msat;
 

lightning/src/routing/router.rs

@@ -943,6 +943,21 @@ impl PaymentParameters {
 		}
 	}
 
+	/// Updates the parameters with the given route parameters configuration.
+	///
+	/// Note:
+	/// We *do not* apply `max_total_routing_fee_msat` here, as it is unique to each route.
+	/// Instead, we apply only the parameters that are common across multiple route-finding sessions
+	/// for a payment across retries.
+	pub(crate) fn with_user_config_ignoring_fee_limit(self, params_config: RouteParametersConfig) -> Self {
+		Self {
+			max_total_cltv_expiry_delta: params_config.max_total_cltv_expiry_delta,
+			max_path_count: params_config.max_path_count,
+			max_channel_saturation_power_of_half: params_config.max_channel_saturation_power_of_half,
+			..self
+		}
+	}
+
 	/// Includes the payee's features. Errors if the parameters were not initialized with
 	/// [`PaymentParameters::from_bolt12_invoice`].
 	///