Add balance and is_live fields to ChannelDetails

fuzz/fuzz_targets/router_target.rs

@@ -205,6 +205,9 @@ pub fn do_test(data: &[u8]) {
 								remote_network_id: get_pubkey!(),
 								channel_value_satoshis: slice_to_be64(get_slice!(8)),
 								user_id: 0,
+								inbound_capacity_msat: 0,
+								is_live: true,
+								outbound_capacity_msat: 0,
 							});
 						}
 						Some(&first_hops_vec[..])

src/ln/channel.rs

@@ -1583,6 +1583,16 @@ impl Channel {
 		(htlc_outbound_count as u32, htlc_outbound_value_msat)
 	}
 
+	/// Get the available (ie not including pending HTLCs) inbound and outbound balance in msat.
+	/// Doesn't bother handling the
+	/// if-we-removed-it-already-but-haven't-fully-resolved-they-can-still-send-an-inbound-HTLC
+	/// corner case properly.
+	pub fn get_inbound_outbound_available_balance_msat(&self) -> (u64, u64) {
+		// Note that we have to handle overflow due to the above case.
+		(cmp::min(self.channel_value_satoshis as i64 * 1000 - self.value_to_self_msat as i64 - self.get_inbound_pending_htlc_stats().1 as i64, 0) as u64,
+		cmp::min(self.value_to_self_msat as i64 - self.get_outbound_pending_htlc_stats().1 as i64, 0) as u64)
+	}
+
 	pub fn update_add_htlc(&mut self, msg: &msgs::UpdateAddHTLC, pending_forward_state: PendingHTLCStatus) -> Result<(), ChannelError> {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32 | ChannelState::RemoteShutdownSent as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(ChannelError::Close("Got add HTLC message when channel was not in an operational state"));

src/ln/channelmanager.rs

@@ -391,6 +391,20 @@ pub struct ChannelDetails {
 	pub channel_value_satoshis: u64,
 	/// The user_id passed in to create_channel, or 0 if the channel was inbound.
 	pub user_id: u64,
+	/// The available outbound capacity for sending HTLCs to the remote peer. This does not include
+	/// any pending HTLCs which are not yet fully resolved (and, thus, who's balance is not
+	/// available for inclusion in new outbound HTLCs). This further does not include any pending
+	/// outgoing HTLCs which are awaiting some other resolution to be sent.
+	pub outbound_capacity_msat: u64,
+	/// The available inbound capacity for the remote peer to send HTLCs to us. This does not
+	/// include any pending HTLCs which are not yet fully resolved (and, thus, who's balance is not
+	/// available for inclusion in new inbound HTLCs).
+	/// Note that there are some corner cases not fully handled here, so the actual available
+	/// inbound capacity may be slightly higher than this.
+	pub inbound_capacity_msat: u64,
+	/// True if the channel is (a) confirmed and funding_locked messages have been exchanged, (b)
+	/// the peer is connected, and (c) no monitor update failure is pending resolution.
+	pub is_live: bool,
 }
 
 macro_rules! handle_error {
@@ -613,19 +627,26 @@ impl ChannelManager {
 		let channel_state = self.channel_state.lock().unwrap();
 		let mut res = Vec::with_capacity(channel_state.by_id.len());
 		for (channel_id, channel) in channel_state.by_id.iter() {
+			let (inbound_capacity_msat, outbound_capacity_msat) = channel.get_inbound_outbound_available_balance_msat();
 			res.push(ChannelDetails {
 				channel_id: (*channel_id).clone(),
 				short_channel_id: channel.get_short_channel_id(),
 				remote_network_id: channel.get_their_node_id(),
 				channel_value_satoshis: channel.get_value_satoshis(),
+				inbound_capacity_msat,
+				outbound_capacity_msat,
 				user_id: channel.get_user_id(),
+				is_live: channel.is_live(),
 			});
 		}
 		res
 	}
 
 	/// Gets the list of usable channels, in random order. Useful as an argument to
 	/// Router::get_route to ensure non-announced channels are used.
+	///
+	/// These are guaranteed to have their is_live value set to true, see the documentation for
+	/// ChannelDetails::is_live for more info on exactly what the criteria are.
 	pub fn list_usable_channels(&self) -> Vec<ChannelDetails> {
 		let channel_state = self.channel_state.lock().unwrap();
 		let mut res = Vec::with_capacity(channel_state.by_id.len());
@@ -634,12 +655,16 @@ impl ChannelManager {
 			// internal/external nomenclature, but that's ok cause that's probably what the user
 			// really wanted anyway.
 			if channel.is_live() {
+				let (inbound_capacity_msat, outbound_capacity_msat) = channel.get_inbound_outbound_available_balance_msat();
 				res.push(ChannelDetails {
 					channel_id: (*channel_id).clone(),
 					short_channel_id: channel.get_short_channel_id(),
 					remote_network_id: channel.get_their_node_id(),
 					channel_value_satoshis: channel.get_value_satoshis(),
+					inbound_capacity_msat,
+					outbound_capacity_msat,
 					user_id: channel.get_user_id(),
+					is_live: true,
 				});
 			}
 		}

src/ln/router.rs

@@ -1468,6 +1468,9 @@ mod tests {
 				remote_network_id: node8.clone(),
 				channel_value_satoshis: 0,
 				user_id: 0,
+				outbound_capacity_msat: 0,
+				inbound_capacity_msat: 0,
+				is_live: true,
 			}];
 			let route = router.get_route(&node3, Some(&our_chans), &Vec::new(), 100, 42).unwrap();
 			assert_eq!(route.hops.len(), 2);
@@ -1543,6 +1546,9 @@ mod tests {
 				remote_network_id: node4.clone(),
 				channel_value_satoshis: 0,
 				user_id: 0,
+				outbound_capacity_msat: 0,
+				inbound_capacity_msat: 0,
+				is_live: true,
 			}];
 			let route = router.get_route(&node7, Some(&our_chans), &last_hops, 100, 42).unwrap();
 			assert_eq!(route.hops.len(), 2);