use lightning::util::anchor_channel_reserves for improved anchor reserve estimation

Replaced flat fee-based reserve logic with estimation using
`get_reserve_per_channel`, following changes introduced in
lightningdevkit/rust-lightning#3487.

Author: Camillarhi

bindings/ldk_node.udl

@@ -17,7 +17,6 @@ dictionary Config {
 
 dictionary AnchorChannelsConfig {
 	sequence<PublicKey> trusted_peers_no_reserve;
-	u64 per_channel_reserve_sats;
 };
 
 dictionary BackgroundSyncConfig {

src/config.rs

@@ -27,7 +27,6 @@ const DEFAULT_BDK_WALLET_SYNC_INTERVAL_SECS: u64 = 80;
 const DEFAULT_LDK_WALLET_SYNC_INTERVAL_SECS: u64 = 30;
 const DEFAULT_FEE_RATE_CACHE_UPDATE_INTERVAL_SECS: u64 = 60 * 10;
 const DEFAULT_PROBING_LIQUIDITY_LIMIT_MULTIPLIER: u64 = 3;
-const DEFAULT_ANCHOR_PER_CHANNEL_RESERVE_SATS: u64 = 25_000;
 
 /// The default log level.
 pub const DEFAULT_LOG_LEVEL: LogLevel = LogLevel::Debug;
@@ -219,7 +218,6 @@ impl Default for Config {
 /// | Parameter                  | Value  |
 /// |----------------------------|--------|
 /// | `trusted_peers_no_reserve` | []     |
-/// | `per_channel_reserve_sats` | 25000  |
 ///
 ///
 /// [BOLT 3]: https://github.com/lightning/bolts/blob/master/03-transactions.md#htlc-timeout-and-htlc-success-transactions
@@ -235,33 +233,11 @@ pub struct AnchorChannelsConfig {
 	/// required Anchor spending transactions confirmed on-chain is potentially insecure
 	/// as the channel may not be closed if they refuse to do so.
 	pub trusted_peers_no_reserve: Vec<PublicKey>,
-	/// The amount of satoshis per anchors-negotiated channel with an untrusted peer that we keep
-	/// as an emergency reserve in our on-chain wallet.
-	///
-	/// This allows for having the required Anchor output spending and HTLC transactions confirmed
-	/// when the channel is closed.
-	///
-	/// If the channel peer is not marked as trusted via
-	/// [`AnchorChannelsConfig::trusted_peers_no_reserve`], we will always try to spend the Anchor
-	/// outputs with *any* on-chain funds available, i.e., the total reserve value as well as any
-	/// spendable funds available in the on-chain wallet. Therefore, this per-channel multiplier is
-	/// really a emergency reserve that we maintain at all time to reduce reduce the risk of
-	/// insufficient funds at time of a channel closure. To this end, we will refuse to open
-	/// outbound or accept inbound channels if we don't have sufficient on-chain funds available to
-	/// cover the additional reserve requirement.
-	///
-	/// **Note:** Depending on the fee market at the time of closure, this reserve amount might or
-	/// might not suffice to successfully spend the Anchor output and have the HTLC transactions
-	/// confirmed on-chain, i.e., you may want to adjust this value accordingly.
-	pub per_channel_reserve_sats: u64,
 }
 
 impl Default for AnchorChannelsConfig {
 	fn default() -> Self {
-		Self {
-			trusted_peers_no_reserve: Vec::new(),
-			per_channel_reserve_sats: DEFAULT_ANCHOR_PER_CHANNEL_RESERVE_SATS,
-		}
+		Self { trusted_peers_no_reserve: Vec::new() }
 	}
 }
 

src/event.rs

@@ -22,6 +22,9 @@ use lightning::impl_writeable_tlv_based_enum;
 use lightning::ln::channelmanager::PaymentId;
 use lightning::ln::types::ChannelId;
 use lightning::routing::gossip::NodeId;
+use lightning::util::anchor_channel_reserves::{
+	get_reserve_per_channel, AnchorChannelReserveContext,
+};
 use lightning::util::config::{
 	ChannelConfigOverrides, ChannelConfigUpdate, ChannelHandshakeConfigUpdate,
 };
@@ -1108,7 +1111,8 @@ where
 						{
 							0
 						} else {
-							anchor_channels_config.per_channel_reserve_sats
+							get_reserve_per_channel(&AnchorChannelReserveContext::default())
+								.to_sat()
 						};
 
 						if spendable_amount_sats < required_amount_sats {

src/lib.rs

@@ -136,6 +136,9 @@ use lightning::ln::channel_state::ChannelShutdownState;
 use lightning::ln::channelmanager::PaymentId;
 use lightning::ln::msgs::SocketAddress;
 use lightning::routing::gossip::NodeAlias;
+use lightning::util::anchor_channel_reserves::{
+	get_reserve_per_channel, AnchorChannelReserveContext,
+};
 use lightning::util::persist::KVStoreSync;
 use lightning_background_processor::process_events_async;
 use liquidity::{LSPS1Liquidity, LiquiditySource};
@@ -1069,7 +1072,7 @@ impl Node {
 				if init_features.requires_anchors_zero_fee_htlc_tx()
 					&& !c.trusted_peers_no_reserve.contains(&node_id)
 				{
-					c.per_channel_reserve_sats
+					get_reserve_per_channel(&AnchorChannelReserveContext::default()).to_sat()
 				} else {
 					0
 				}
@@ -1132,13 +1135,11 @@ impl Node {
 	/// channel counterparty on channel open. This can be useful to start out with the balance not
 	/// entirely shifted to one side, therefore allowing to receive payments from the getgo.
 	///
-	/// If Anchor channels are enabled, this will ensure the configured
-	/// [`AnchorChannelsConfig::per_channel_reserve_sats`] is available and will be retained before
-	/// opening the channel.
+	/// If Anchor channels are enabled, this will ensure the reserved amount per
+	/// channel is available and will be retained before opening the channel.
 	///
 	/// Returns a [`UserChannelId`] allowing to locally keep track of the channel.
 	///
-	/// [`AnchorChannelsConfig::per_channel_reserve_sats`]: crate::config::AnchorChannelsConfig::per_channel_reserve_sats
 	pub fn open_channel(
 		&self, node_id: PublicKey, address: SocketAddress, channel_amount_sats: u64,
 		push_to_counterparty_msat: Option<u64>, channel_config: Option<ChannelConfig>,
@@ -1167,13 +1168,11 @@ impl Node {
 	/// channel counterparty on channel open. This can be useful to start out with the balance not
 	/// entirely shifted to one side, therefore allowing to receive payments from the getgo.
 	///
-	/// If Anchor channels are enabled, this will ensure the configured
-	/// [`AnchorChannelsConfig::per_channel_reserve_sats`] is available and will be retained before
-	/// opening the channel.
+	/// If Anchor channels are enabled, this will ensure the reserved amount per
+	/// channel is available and will be retained before opening the channel.
 	///
 	/// Returns a [`UserChannelId`] allowing to locally keep track of the channel.
 	///
-	/// [`AnchorChannelsConfig::per_channel_reserve_sats`]: crate::config::AnchorChannelsConfig::per_channel_reserve_sats
 	pub fn open_announced_channel(
 		&self, node_id: PublicKey, address: SocketAddress, channel_amount_sats: u64,
 		push_to_counterparty_msat: Option<u64>, channel_config: Option<ChannelConfig>,
@@ -1580,6 +1579,8 @@ impl_writeable_tlv_based!(NodeMetrics, {
 pub(crate) fn total_anchor_channels_reserve_sats(
 	channel_manager: &ChannelManager, config: &Config,
 ) -> u64 {
+	let reserve_sat_per_channel = get_anchor_reserve_per_channel();
+
 	config.anchor_channels_config.as_ref().map_or(0, |anchor_channels_config| {
 		channel_manager
 			.list_channels()
@@ -1593,6 +1594,12 @@ pub(crate) fn total_anchor_channels_reserve_sats(
 						.map_or(false, |t| t.requires_anchors_zero_fee_htlc_tx())
 			})
 			.count() as u64
-			* anchor_channels_config.per_channel_reserve_sats
+			* reserve_sat_per_channel
 	})
 }
+
+/// Returns the configured anchor channel reserve per channel in satoshis.
+pub fn get_anchor_reserve_per_channel() -> u64 {
+	let context = AnchorChannelReserveContext::default();
+	get_reserve_per_channel(&context).to_sat()
+}

src/liquidity.rs

@@ -20,6 +20,9 @@ use lightning::ln::channelmanager::{InterceptId, MIN_FINAL_CLTV_EXPIRY_DELTA};
 use lightning::ln::msgs::SocketAddress;
 use lightning::ln::types::ChannelId;
 use lightning::routing::router::{RouteHint, RouteHintHop};
+use lightning::util::anchor_channel_reserves::{
+	get_reserve_per_channel, AnchorChannelReserveContext,
+};
 use lightning_invoice::{Bolt11Invoice, Bolt11InvoiceDescription, InvoiceBuilder, RoutingFees};
 use lightning_liquidity::events::LiquidityEvent;
 use lightning_liquidity::lsps0::ser::{LSPSDateTime, LSPSRequestId};
@@ -672,7 +675,8 @@ where
 						if init_features.requires_anchors_zero_fee_htlc_tx()
 							&& !c.trusted_peers_no_reserve.contains(&their_network_key)
 						{
-							c.per_channel_reserve_sats
+							get_reserve_per_channel(&AnchorChannelReserveContext::default())
+								.to_sat()
 						} else {
 							0
 						}

tests/common/mod.rs

@@ -29,6 +29,7 @@ use electrsd::corepc_node::{Client as BitcoindClient, Node as BitcoinD};
 use electrsd::{corepc_node, ElectrsD};
 use electrum_client::ElectrumApi;
 use ldk_node::config::{AsyncPaymentsRole, Config, ElectrumSyncConfig, EsploraSyncConfig};
+use ldk_node::get_anchor_reserve_per_channel;
 use ldk_node::io::sqlite_store::SqliteStore;
 use ldk_node::payment::{PaymentDirection, PaymentKind, PaymentStatus};
 use ldk_node::{
@@ -640,8 +641,9 @@ pub(crate) fn do_channel_full_cycle<E: ElectrumApi>(
 	let addr_a = node_a.onchain_payment().new_address().unwrap();
 	let addr_b = node_b.onchain_payment().new_address().unwrap();
 
-	let premine_amount_sat = if expect_anchor_channel { 2_125_000 } else { 2_100_000 };
+	let anchor_reserve = if expect_anchor_channel { get_anchor_reserve_per_channel() } else { 0 };
 
+	let premine_amount_sat = 2_100_000 + anchor_reserve;
 	premine_and_distribute_funds(
 		&bitcoind,
 		electrsd,
@@ -725,7 +727,8 @@ pub(crate) fn do_channel_full_cycle<E: ElectrumApi>(
 	);
 
 	let onchain_fee_buffer_sat = 5000;
-	let node_a_anchor_reserve_sat = if expect_anchor_channel { 25_000 } else { 0 };
+	let node_a_anchor_reserve_sat =
+		if expect_anchor_channel { get_anchor_reserve_per_channel() } else { 0 };
 	let node_a_upper_bound_sat =
 		premine_amount_sat - node_a_anchor_reserve_sat - funding_amount_sat;
 	let node_a_lower_bound_sat = premine_amount_sat
@@ -746,7 +749,7 @@ pub(crate) fn do_channel_full_cycle<E: ElectrumApi>(
 	{
 		0
 	} else {
-		25_000
+		get_anchor_reserve_per_channel()
 	};
 	assert_eq!(
 		node_b.list_balances().spendable_onchain_balance_sats,

tests/integration_tests_rust.rs

@@ -26,6 +26,7 @@ use common::{
 	setup_two_nodes, wait_for_tx, TestChainSource, TestSyncStore,
 };
 use ldk_node::config::{AsyncPaymentsRole, EsploraSyncConfig};
+use ldk_node::get_anchor_reserve_per_channel;
 use ldk_node::liquidity::LSPS2ServiceConfig;
 use ldk_node::payment::{
 	ConfirmationStatus, PaymentDetails, PaymentDirection, PaymentKind, PaymentStatus,
@@ -317,7 +318,7 @@ fn onchain_send_receive() {
 	let unchecked_address = Address::<NetworkUnchecked>::from_str(static_address).unwrap();
 	let addr_c = unchecked_address.assume_checked();
 
-	let premine_amount_sat = 1_100_000;
+	let premine_amount_sat = 2_100_000;
 	premine_and_distribute_funds(
 		&bitcoind.client,
 		&electrsd.client,
@@ -349,7 +350,7 @@ fn onchain_send_receive() {
 	}
 
 	let channel_amount_sat = 1_000_000;
-	let reserve_amount_sat = 25_000;
+	let reserve_amount_sat = get_anchor_reserve_per_channel();
 	open_channel(&node_b, &node_a, channel_amount_sat, true, &electrsd);
 	generate_blocks_and_wait(&bitcoind.client, &electrsd.client, 6);
 
@@ -514,8 +515,8 @@ fn onchain_send_all_retains_reserve() {
 	let addr_a = node_a.onchain_payment().new_address().unwrap();
 	let addr_b = node_b.onchain_payment().new_address().unwrap();
 
-	let premine_amount_sat = 1_000_000;
-	let reserve_amount_sat = 25_000;
+	let premine_amount_sat = 2_000_000;
+	let reserve_amount_sat = get_anchor_reserve_per_channel();
 	let onchain_fee_buffer_sat = 1000;
 	premine_and_distribute_funds(
 		&bitcoind.client,