Include overpaid value in `Route::get_total_fees`

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 8b3a96eb42ed21c04fe915d6c9674ced3d3da46a..10bdd69b51a9b4a66e14ace4278645da4ada4be4 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -348,10 +348,15 @@ pub struct Route {
 impl Route {
        /// Returns the total amount of fees paid on this [`Route`].
        ///
-       /// This doesn't include any extra payment made to the recipient, which can happen in excess of
-       /// the amount passed to [`find_route`]'s `route_params.final_value_msat`.
+       /// For objects serialized with LDK 0.0.117 and after, this includes any extra payment made to
+       /// the recipient, which can happen in excess of the amount passed to [`find_route`] via
+       /// [`RouteParameters::final_value_msat`], if we had to reach the [`htlc_minimum_msat`] limits.
+       ///
+       /// [`htlc_minimum_msat`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#the-channel_update-message
        pub fn get_total_fees(&self) -> u64 {
-               self.paths.iter().map(|path| path.fee_msat()).sum()
+               let overpaid_value_msat = self.route_params.as_ref()
+                       .map_or(0, |p| self.get_total_amount().saturating_sub(p.final_value_msat));
+               overpaid_value_msat + self.paths.iter().map(|path| path.fee_msat()).sum::<u64>()
        }
 
        /// Returns the total amount paid on this [`Route`], excluding the fees. Might be more than