Implement utilities for keysending to private nodes

lightning/src/ln/features.rs

@@ -420,6 +420,18 @@ impl InvoiceFeatures {
 	pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 		self.to_context_internal()
 	}
+
+	/// Getting a route for a keysend payment to a private node requires providing the payee's
+	/// features (since they were not announced in a node announcement). However, keysend payments
+	/// don't have an invoice to pull the payee's features from, so this method is provided for use in
+	/// [`get_keysend_route`], thus omitting the need for payers to manually construct an
+	/// `InvoiceFeatures` for [`get_route`].
+	///
+	/// [`get_keysend_route`]: crate::routing::router::get_keysend_route
+	/// [`get_route`]: crate::routing::router::get_route
+	pub(crate) fn for_keysend() -> InvoiceFeatures {
+		InvoiceFeatures::empty().set_variable_length_onion_optional()
+	}
 }
 
 impl ToBase32 for InvoiceFeatures {

lightning/src/ln/functional_tests.rs

@@ -22,7 +22,7 @@ use ln::channel::{COMMITMENT_TX_BASE_WEIGHT, COMMITMENT_TX_WEIGHT_PER_HTLC};
 use ln::channelmanager::{ChannelManager, ChannelManagerReadArgs, RAACommitmentOrder, PaymentSendFailure, BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA};
 use ln::channel::{Channel, ChannelError};
 use ln::{chan_utils, onion_utils};
-use routing::router::{Route, RouteHop, get_route};
+use routing::router::{Route, RouteHop, get_route, get_keysend_route};
 use ln::features::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
 use ln::msgs;
 use ln::msgs::{ChannelMessageHandler,RoutingMessageHandler,HTLCFailChannelUpdate, ErrorAction};
@@ -9419,3 +9419,33 @@ fn test_keysend_payments_to_public_node() {
 	pass_along_path(&nodes[0], &path, 10000, payment_hash, PaymentSecret([0; 32]), event, true, Some(test_preimage));
 	claim_payment(&nodes[0], &path, test_preimage);
 }
+
+#[test]
+fn test_keysend_payments_to_private_node() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	let payer_pubkey = nodes[0].node.get_our_node_id();
+	let payee_pubkey = nodes[1].node.get_our_node_id();
+	nodes[0].node.peer_connected(&payee_pubkey, &msgs::Init { features: InitFeatures::known() });
+	nodes[1].node.peer_connected(&payer_pubkey, &msgs::Init { features: InitFeatures::known() });
+
+	let _chan = create_chan_between_nodes(&nodes[0], &nodes[1], InitFeatures::known(), InitFeatures::known());
+	let network_graph = nodes[0].net_graph_msg_handler.network_graph.read().unwrap();
+	let first_hops = nodes[0].node.list_usable_channels();
+	let route = get_keysend_route(&payer_pubkey, &network_graph, &payee_pubkey,
+                                Some(&first_hops.iter().collect::<Vec<_>>()), &vec![], 10000, 40,
+                                nodes[0].logger).unwrap();
+
+	let test_preimage = PaymentPreimage([42; 32]);
+	let payment_hash = nodes[0].node.send_spontaneous_payment(&route, Some(test_preimage)).unwrap();
+	check_added_monitors!(nodes[0], 1);
+	let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+	assert_eq!(events.len(), 1);
+	let event = events.pop().unwrap();
+	let path = vec![&nodes[1]];
+	pass_along_path(&nodes[0], &path, 10000, payment_hash, PaymentSecret([0; 32]), event, true, Some(test_preimage));
+	claim_payment(&nodes[0], &path, test_preimage);
+}

lightning/src/routing/router.rs

@@ -327,6 +327,18 @@ fn compute_fees(amount_msat: u64, channel_fees: RoutingFees) -> Option<u64> {
 	}
 }
 
+/// Gets a keysend route from us (payer) to the given target node (payee). This is needed because
+/// keysend payments do not have an invoice from which to pull the payee's supported features, which
+/// makes it tricky to otherwise supply the `payee_features` parameter of `get_route`.
+pub fn get_keysend_route<L: Deref>(our_node_id: &PublicKey, network: &NetworkGraph, payee:
+                       &PublicKey, first_hops: Option<&[&ChannelDetails]>, last_hops: &[&RouteHint],
+                       final_value_msat: u64, final_cltv: u32, logger: L) -> Result<Route,
+                       LightningError> where L::Target: Logger {
+	let invoice_features = InvoiceFeatures::for_keysend();
+	get_route(our_node_id, network, payee, Some(invoice_features), first_hops, last_hops,
+            final_value_msat, final_cltv, logger)
+}
+
 /// Gets a route from us (payer) to the given target node (payee).
 ///
 /// If the payee provided features in their invoice, they should be provided via payee_features.