Remove AvailableBalances::balance_msat

The ChannelMonitor::get_claimable_balances method provides a more
straightforward approach to the balance of a channel, which satisfies
most use cases. The computation of AvailableBalances::balance_msat is
complex and originally had a different purpose that is not applicable
anymore.

Co-authored-by: Willem Van Lint <[email protected]>

Author: dunxen

fuzz/src/router.rs

@@ -242,7 +242,6 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
 							is_channel_ready: true,
 							is_usable: true,
 							is_public: true,
-							balance_msat: 0,
 							outbound_capacity_msat: capacity.saturating_mul(1000),
 							next_outbound_htlc_limit_msat: capacity.saturating_mul(1000),
 							next_outbound_htlc_minimum_msat: 0,

lightning/src/chain/chainmonitor.rs

@@ -394,8 +394,7 @@ where C::Target: chain::Filter,
 	/// claims which are awaiting confirmation.
 	///
 	/// Includes the balances from each [`ChannelMonitor`] *except* those included in
-	/// `ignored_channels`, allowing you to filter out balances from channels which are still open
-	/// (and whose balance should likely be pulled from the [`ChannelDetails`]).
+	/// `ignored_channels`.
 	///
 	/// See [`ChannelMonitor::get_claimable_balances`] for more details on the exact criteria for
 	/// inclusion in the return value.

lightning/src/ln/channel.rs

@@ -79,8 +79,6 @@ pub struct ChannelValueStat {
 }
 
 pub struct AvailableBalances {
-	/// The amount that would go to us if we close the channel, ignoring any on-chain fees.
-	pub balance_msat: u64,
 	/// Total amount available for our counterparty to send to us.
 	pub inbound_capacity_msat: u64,
 	/// Total amount available for us to send to our counterparty.
@@ -3076,14 +3074,6 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 		let dust_exposure_limiting_feerate = self.get_dust_exposure_limiting_feerate(&fee_estimator);
 		let htlc_stats = context.get_pending_htlc_stats(None, dust_exposure_limiting_feerate);
 
-		let mut balance_msat = context.value_to_self_msat;
-		for ref htlc in context.pending_inbound_htlcs.iter() {
-			if let InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::Fulfill(_)) = htlc.state {
-				balance_msat += htlc.amount_msat;
-			}
-		}
-		balance_msat -= htlc_stats.pending_outbound_htlcs_value_msat;
-
 		let outbound_capacity_msat = context.value_to_self_msat
 				.saturating_sub(htlc_stats.pending_outbound_htlcs_value_msat)
 				.saturating_sub(
@@ -3224,7 +3214,6 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 			outbound_capacity_msat,
 			next_outbound_htlc_limit_msat: available_capacity_msat,
 			next_outbound_htlc_minimum_msat,
-			balance_msat,
 		}
 	}
 

lightning/src/ln/channel_state.rs

@@ -273,8 +273,14 @@ impl_writeable_tlv_based!(ChannelCounterparty, {
 
 /// Details of a channel, as returned by [`ChannelManager::list_channels`] and [`ChannelManager::list_usable_channels`]
 ///
+/// Balances of a channel are available through [`ChainMonitor::get_claimable_balances`] and
+/// [`ChannelMonitor::get_claimable_balances`], calculated with respect to the corresponding on-chain
+/// transactions.
+///
 /// [`ChannelManager::list_channels`]: crate::ln::channelmanager::ChannelManager::list_channels
 /// [`ChannelManager::list_usable_channels`]: crate::ln::channelmanager::ChannelManager::list_usable_channels
+/// [`ChainMonitor::get_claimable_balances`]: crate::chain::chainmonitor::ChainMonitor::get_claimable_balances
+/// [`ChannelMonitor::get_claimable_balances`]: crate::chain::channelmonitor::ChannelMonitor::get_claimable_balances
 #[derive(Clone, Debug, PartialEq)]
 pub struct ChannelDetails {
 	/// The channel's ID (prior to funding transaction generation, this is a random 32 bytes,
@@ -353,24 +359,11 @@ pub struct ChannelDetails {
 	///
 	/// This value will be `None` for objects serialized with LDK versions prior to 0.0.115.
 	pub feerate_sat_per_1000_weight: Option<u32>,
-	/// Our total balance.  This is the amount we would get if we close the channel.
-	/// This value is not exact. Due to various in-flight changes and feerate changes, exactly this
-	/// amount is not likely to be recoverable on close.
-	///
-	/// This does not include any pending HTLCs which are not yet fully resolved (and, thus, whose
-	/// 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.
-	/// This does not consider any on-chain fees.
-	///
-	/// See also [`ChannelDetails::outbound_capacity_msat`]
-	pub balance_msat: 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, whose 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.
 	///
-	/// See also [`ChannelDetails::balance_msat`]
-	///
 	/// This value is not exact. Due to various in-flight changes, feerate changes, and our
 	/// conflict-avoidance policy, exactly this amount is not likely to be spendable. However, we
 	/// should be able to spend nearly this amount.
@@ -380,8 +373,8 @@ pub struct ChannelDetails {
 	/// the current state and per-HTLC limit(s). This is intended for use when routing, allowing us
 	/// to use a limit as close as possible to the HTLC limit we can currently send.
 	///
-	/// See also [`ChannelDetails::next_outbound_htlc_minimum_msat`],
-	/// [`ChannelDetails::balance_msat`], and [`ChannelDetails::outbound_capacity_msat`].
+	/// See also [`ChannelDetails::next_outbound_htlc_minimum_msat`] and
+	/// [`ChannelDetails::outbound_capacity_msat`].
 	pub next_outbound_htlc_limit_msat: u64,
 	/// The minimum value for sending a single HTLC to the remote peer. This is the equivalent of
 	/// [`ChannelDetails::next_outbound_htlc_limit_msat`] but represents a lower-bound, rather than
@@ -532,7 +525,6 @@ impl ChannelDetails {
 			channel_value_satoshis: context.get_value_satoshis(),
 			feerate_sat_per_1000_weight: Some(context.get_feerate_sat_per_1000_weight()),
 			unspendable_punishment_reserve: to_self_reserve_satoshis,
-			balance_msat: balance.balance_msat,
 			inbound_capacity_msat: balance.inbound_capacity_msat,
 			outbound_capacity_msat: balance.outbound_capacity_msat,
 			next_outbound_htlc_limit_msat: balance.next_outbound_htlc_limit_msat,
@@ -574,7 +566,7 @@ impl Writeable for ChannelDetails {
 			(10, self.channel_value_satoshis, required),
 			(12, self.unspendable_punishment_reserve, option),
 			(14, user_channel_id_low, required),
-			(16, self.balance_msat, required),
+			(16, self.next_outbound_htlc_limit_msat, required), // Forwards compatibility for removed balance_msat field.
 			(18, self.outbound_capacity_msat, required),
 			(19, self.next_outbound_htlc_limit_msat, required),
 			(20, self.inbound_capacity_msat, required),
@@ -612,7 +604,7 @@ impl Readable for ChannelDetails {
 			(10, channel_value_satoshis, required),
 			(12, unspendable_punishment_reserve, option),
 			(14, user_channel_id_low, required),
-			(16, balance_msat, required),
+			(16, _balance_msat, option), // Backwards compatibility for removed balance_msat field.
 			(18, outbound_capacity_msat, required),
 			// Note that by the time we get past the required read above, outbound_capacity_msat will be
 			// filled in, so we can safely unwrap it here.
@@ -640,6 +632,8 @@ impl Readable for ChannelDetails {
 		let user_channel_id = user_channel_id_low as u128
 			+ ((user_channel_id_high_opt.unwrap_or(0 as u64) as u128) << 64);
 
+		let _balance_msat: Option<u64> = _balance_msat;
+
 		Ok(Self {
 			inbound_scid_alias,
 			channel_id: channel_id.0.unwrap(),
@@ -652,7 +646,6 @@ impl Readable for ChannelDetails {
 			channel_value_satoshis: channel_value_satoshis.0.unwrap(),
 			unspendable_punishment_reserve,
 			user_channel_id,
-			balance_msat: balance_msat.0.unwrap(),
 			outbound_capacity_msat: outbound_capacity_msat.0.unwrap(),
 			next_outbound_htlc_limit_msat: next_outbound_htlc_limit_msat.0.unwrap(),
 			next_outbound_htlc_minimum_msat: next_outbound_htlc_minimum_msat.0.unwrap(),

lightning/src/routing/router.rs

@@ -3602,7 +3602,6 @@ mod tests {
 			inbound_scid_alias: None,
 			channel_value_satoshis: 0,
 			user_channel_id: 0,
-			balance_msat: 0,
 			outbound_capacity_msat,
 			next_outbound_htlc_limit_msat: outbound_capacity_msat,
 			next_outbound_htlc_minimum_msat: 0,
@@ -8877,7 +8876,6 @@ pub(crate) mod bench_utils {
 			outbound_scid_alias: None,
 			channel_value_satoshis: 10_000_000_000,
 			user_channel_id: 0,
-			balance_msat: 10_000_000_000,
 			outbound_capacity_msat: 10_000_000_000,
 			next_outbound_htlc_minimum_msat: 0,
 			next_outbound_htlc_limit_msat: 10_000_000_000,

pending_changelog/remove_balance_msat.txt

@@ -0,0 +1 @@
+* The `AvailableBalances::balance_msat` field has been removed in favor of `ChannelMonitor::get_claimable_balances`. `ChannelDetails` serialized with versions of LDK >= 0.0.124 will have their `balance_msat` field set to `next_outbound_htlc_limit_msat` when read by versions of LDK prior to 0.0.124 (#TODO).