Add and use ChannelInfo::as_coming_from.

Author: tnull

lightning/src/routing/network_graph.rs

@@ -674,6 +674,21 @@ impl ChannelInfo {
 		};
 		Some((DirectedChannelInfo { channel: self, direction }, source))
 	}
+
+	/// Returns a [`DirectedChannelInfo`] for the channel coming from the given `source` to a
+	/// returned `target`, or `None` if `source` is not one of the channel's counterparties.
+	pub fn as_coming_from(&self, source: &NodeId) -> Option<(DirectedChannelInfo, &NodeId)> {
+		let (direction, target) = {
+			if source == &self.node_one {
+				(self.one_to_two.as_ref(), &self.node_two)
+			} else if source == &self.node_two {
+				(self.two_to_one.as_ref(), &self.node_one)
+			} else {
+				return None;
+			}
+		};
+		Some((DirectedChannelInfo { channel: self, direction }, target))
+	}
 }
 
 impl fmt::Display for ChannelInfo {

lightning/src/routing/router.rs

@@ -1578,7 +1578,7 @@ fn add_random_cltv_offset(route: &mut Route, payment_params: &PaymentParameters,
 					if let Some(random_channel) = usize::from_be_bytes(random_path_bytes).checked_rem(cur_node.channels.len())
 						.and_then(|index| cur_node.channels.get(index))
 						.and_then(|id| network_channels.get(id)) {
-							random_channel.as_directed_to(&cur_node_id).map(|(dir_info, next_id)| {
+							random_channel.as_coming_from(&cur_node_id).map(|(dir_info, next_id)| {
 								dir_info.direction().map(|channel_update_info|
 									shadow_ctlv_expiry_delta_offset = shadow_ctlv_expiry_delta_offset
 										.checked_add(channel_update_info.cltv_expiry_delta.into())