Fix `Route` serialization round-trip

When the `max_total_routing_fee_msat` parameter was added to
`RouteParameters`, the serialization used `map` to get the max fee,
accidentally writing an `Option<Option<u64>>`, but then read it as
an `Option<u64>`. Thus, any `Route`s with a `route_params` written
will fail to be read back.

Luckily, this is an incredibly rarely-used bit of code, so only one
user managed to hit it.

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 42e7f76dab9f977651abc15c8c899905eaf102ac..8e59c9bd46f5ff5edeed994adb96d2667a0acfc3 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -526,7 +526,7 @@ impl Writeable for Route {
                        (1, self.route_params.as_ref().map(|p| &p.payment_params), option),
                        (2, blinded_tails, optional_vec),
                        (3, self.route_params.as_ref().map(|p| p.final_value_msat), option),
-                       (5, self.route_params.as_ref().map(|p| p.max_total_routing_fee_msat), option),
+                       (5, self.route_params.as_ref().and_then(|p| p.max_total_routing_fee_msat), option),
                });
                Ok(())
        }