[router] Use the invoice value for last-hop hint channel capacity

If an invoice contains route hints, we should assume the channel
capacity is sufficient to route the invoice's value.

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index ac9b2109ad5d6252b169a8e40ccd556fa7596d0d..087e7ede215d302dea95560f0484b44f6f6ae0e2 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -882,7 +882,11 @@ pub fn get_route<L: Deref>(our_node_id: &PublicKey, network: &NetworkGraph, paye
                                        htlc_maximum_msat: hop.htlc_maximum_msat,
                                        fees: hop.fees,
                                };
-                               if add_entry!(hop.short_channel_id, hop.src_node_id, payee, directional_info, None::<u64>, &empty_channel_features, 0, path_value_msat, 0) {
+                               // We assume that the recipient only included route hints for routes which had
+                               // sufficient value to route `final_value_msat`. Note that in the case of "0-value"
+                               // invoices where the invoice does not specify value this may not be the case, but
+                               // better to include the hints than not.
+                               if add_entry!(hop.short_channel_id, hop.src_node_id, payee, directional_info, Some((final_value_msat + 999) / 1000), &empty_channel_features, 0, path_value_msat, 0) {
                                        // If this hop connects to a node with which we have a direct channel,
                                        // ignore the network graph and, if the last hop was added, add our
                                        // direct channel to the candidate set.