Maintain and expose anchor reserve

Author: tnull

bindings/kotlin/ldk-node-jvm/lib/src/test/kotlin/org/lightningdevkit/ldknode/LibraryTest.kt

@@ -203,9 +203,9 @@ class LibraryTest {
         val spendableBalance2AfterOpen = node2.listBalances().spendableOnchainBalanceSats
         println("Spendable balance 1 after open: $spendableBalance1AfterOpen")
         println("Spendable balance 2 after open: $spendableBalance2AfterOpen")
-        assert(spendableBalance1AfterOpen > 49000u)
-        assert(spendableBalance1AfterOpen < 50000u)
-        assertEquals(100000uL, spendableBalance2AfterOpen)
+        assert(spendableBalance1AfterOpen > 24000u)
+        assert(spendableBalance1AfterOpen < 25000u)
+        assertEquals(75000uL, spendableBalance2AfterOpen)
 
         val channelReadyEvent1 = node1.waitNextEvent()
         println("Got event: $channelReadyEvent1")

bindings/ldk_node.udl

@@ -354,6 +354,7 @@ interface PendingSweepBalance {
 dictionary BalanceDetails {
 	u64 total_onchain_balance_sats;
 	u64 spendable_onchain_balance_sats;
+	u64 total_anchor_channels_reserve_sats;
 	u64 total_lightning_balance_sats;
 	sequence<LightningBalance> lightning_balances;
 	sequence<PendingSweepBalance> pending_balances_from_channel_closures;

src/balance.rs

@@ -15,7 +15,15 @@ pub struct BalanceDetails {
 	/// The total balance of our on-chain wallet.
 	pub total_onchain_balance_sats: u64,
 	/// The currently spendable balance of our on-chain wallet.
+	///
+	/// This includes any sufficiently confirmed funds, minus
+	/// [`total_anchor_channels_reserve_sats`].
+	///
+	/// [`total_anchor_channels_reserve_sats`]: Self::total_anchor_channels_reserve_sats
 	pub spendable_onchain_balance_sats: u64,
+	/// The share of our total balance that we retain as an emergency reserve to (hopefully) be
+	/// able to spend the Anchor outputs when one of our channels is closed.
+	pub total_anchor_channels_reserve_sats: u64,
 	/// The total balance that we would be able to claim across all our Lightning channels.
 	///
 	/// Note this excludes balances that we are unsure if we are able to claim (e.g., as we are

src/event.rs

@@ -820,9 +820,67 @@ where
 				temporary_channel_id,
 				counterparty_node_id,
 				funding_satoshis,
-				channel_type: _,
+				channel_type,
 				push_msat: _,
 			} => {
+				let anchor_channel = channel_type.requires_anchors_zero_fee_htlc_tx();
+
+				if anchor_channel {
+					if let Some(anchor_channels_config) =
+						self.config.anchor_channels_config.as_ref()
+					{
+						let cur_anchor_reserve_sats = crate::total_anchor_channels_reserve_sats(
+							&self.channel_manager,
+							&self.config,
+						);
+						let spendable_amount_sats = self
+							.wallet
+							.get_spendable_amount_sats(cur_anchor_reserve_sats)
+							.unwrap_or(0);
+
+						let required_amount_sats = if anchor_channels_config
+							.trusted_peers_no_reserve
+							.contains(&counterparty_node_id)
+						{
+							0
+						} else {
+							anchor_channels_config.per_channel_reserve_sats
+						};
+
+						if spendable_amount_sats < required_amount_sats {
+							log_error!(
+								self.logger,
+								"Rejecting inbound Anchor channel from peer {} due to insufficient available on-chain reserves.",
+								counterparty_node_id,
+							);
+							self.channel_manager
+								.force_close_without_broadcasting_txn(
+									&temporary_channel_id,
+									&counterparty_node_id,
+								)
+								.unwrap_or_else(|e| {
+									log_error!(self.logger, "Failed to reject channel: {:?}", e)
+								});
+							return;
+						}
+					} else {
+						log_error!(
+							self.logger,
+							"Rejecting inbound channel from peer {} due to Anchor channels being disabled.",
+							counterparty_node_id,
+						);
+						self.channel_manager
+							.force_close_without_broadcasting_txn(
+								&temporary_channel_id,
+								&counterparty_node_id,
+							)
+							.unwrap_or_else(|e| {
+								log_error!(self.logger, "Failed to reject channel: {:?}", e)
+							});
+						return;
+					}
+				}
+
 				let user_channel_id: u128 = rand::thread_rng().gen::<u128>();
 				let allow_0conf = self.config.trusted_peers_0conf.contains(&counterparty_node_id);
 				let res = if allow_0conf {
@@ -843,8 +901,9 @@ where
 					Ok(()) => {
 						log_info!(
 							self.logger,
-							"Accepting inbound{} channel of {}sats from{} peer {}",
+							"Accepting inbound{}{} channel of {}sats from{} peer {}",
 							if allow_0conf { " 0conf" } else { "" },
+							if anchor_channel { " Anchor" } else { "" },
 							funding_satoshis,
 							if allow_0conf { " trusted" } else { "" },
 							counterparty_node_id,
@@ -853,8 +912,9 @@ where
 					Err(e) => {
 						log_error!(
 							self.logger,
-							"Error while accepting inbound{} channel from{} peer {}: {:?}",
+							"Error while accepting inbound{}{} channel from{} peer {}: {:?}",
 							if allow_0conf { " 0conf" } else { "" },
+							if anchor_channel { " Anchor" } else { "" },
 							counterparty_node_id,
 							if allow_0conf { " trusted" } else { "" },
 							e,

src/lib.rs

@@ -142,7 +142,7 @@ use logger::{log_error, log_info, log_trace, FilesystemLogger, Logger};
 
 use lightning::chain::{BestBlock, Confirm};
 use lightning::events::bump_transaction::Wallet as LdkWallet;
-use lightning::ln::channelmanager::PaymentId;
+use lightning::ln::channelmanager::{ChannelShutdownState, PaymentId};
 use lightning::ln::msgs::SocketAddress;
 
 use lightning::util::config::{ChannelHandshakeConfig, UserConfig};
@@ -916,6 +916,8 @@ impl Node {
 		OnchainPayment::new(
 			Arc::clone(&self.runtime),
 			Arc::clone(&self.wallet),
+			Arc::clone(&self.channel_manager),
+			Arc::clone(&self.config),
 			Arc::clone(&self.logger),
 		)
 	}
@@ -926,6 +928,8 @@ impl Node {
 		Arc::new(OnchainPayment::new(
 			Arc::clone(&self.runtime),
 			Arc::clone(&self.wallet),
+			Arc::clone(&self.channel_manager),
+			Arc::clone(&self.config),
 			Arc::clone(&self.logger),
 		))
 	}
@@ -1001,6 +1005,10 @@ 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.
+	///
 	/// Returns a [`UserChannelId`] allowing to locally keep track of the channel.
 	pub fn connect_open_channel(
 		&self, node_id: PublicKey, address: SocketAddress, channel_amount_sats: u64,
@@ -1013,18 +1021,26 @@ impl Node {
 		}
 		let runtime = rt_lock.as_ref().unwrap();
 
-		let cur_balance = self.wallet.get_balance()?;
-		if cur_balance.get_spendable() < channel_amount_sats {
-			log_error!(self.logger, "Unable to create channel due to insufficient funds.");
-			return Err(Error::InsufficientFunds);
-		}
-
 		let peer_info = PeerInfo { node_id, address };
 
 		let con_node_id = peer_info.node_id;
 		let con_addr = peer_info.address.clone();
 		let con_cm = Arc::clone(&self.connection_manager);
 
+		let cur_anchor_reserve_sats =
+			total_anchor_channels_reserve_sats(&self.channel_manager, &self.config);
+		let spendable_amount_sats =
+			self.wallet.get_spendable_amount_sats(cur_anchor_reserve_sats).unwrap_or(0);
+
+		// Fail early if we have less than the channel value available.
+		if spendable_amount_sats < channel_amount_sats {
+			log_error!(self.logger,
+				"Unable to create channel due to insufficient funds. Available: {}sats, Required: {}sats",
+				spendable_amount_sats, channel_amount_sats
+			);
+			return Err(Error::InsufficientFunds);
+		}
+
 		// We need to use our main runtime here as a local runtime might not be around to poll
 		// connection futures going forward.
 		tokio::task::block_in_place(move || {
@@ -1033,11 +1049,37 @@ impl Node {
 			})
 		})?;
 
+		// Fail if we have less than the channel value + anchor reserve available (if applicable).
+		let init_features = self
+			.peer_manager
+			.peer_by_node_id(&node_id)
+			.ok_or(Error::ConnectionFailed)?
+			.init_features;
+		let required_funds_sats = channel_amount_sats
+			+ self.config.anchor_channels_config.as_ref().map_or(0, |c| {
+				if init_features.requires_anchors_zero_fee_htlc_tx()
+					&& !c.trusted_peers_no_reserve.contains(&node_id)
+				{
+					c.per_channel_reserve_sats
+				} else {
+					0
+				}
+			});
+
+		if spendable_amount_sats < required_funds_sats {
+			log_error!(self.logger,
+				"Unable to create channel due to insufficient funds. Available: {}sats, Required: {}sats",
+				spendable_amount_sats, required_funds_sats
+			);
+			return Err(Error::InsufficientFunds);
+		}
+
 		let channel_config = (*(channel_config.unwrap_or_default())).clone().into();
 		let user_config = UserConfig {
 			channel_handshake_limits: Default::default(),
 			channel_handshake_config: ChannelHandshakeConfig {
 				announced_channel: announce_channel,
+				negotiate_anchors_zero_fee_htlc_tx: self.config.anchor_channels_config.is_some(),
 				..Default::default()
 			},
 			channel_config,
@@ -1196,11 +1238,13 @@ impl Node {
 
 	/// Retrieves an overview of all known balances.
 	pub fn list_balances(&self) -> BalanceDetails {
-		let (total_onchain_balance_sats, spendable_onchain_balance_sats) = self
-			.wallet
-			.get_balance()
-			.map(|bal| (bal.get_total(), bal.get_spendable()))
-			.unwrap_or((0, 0));
+		let cur_anchor_reserve_sats =
+			total_anchor_channels_reserve_sats(&self.channel_manager, &self.config);
+		let (total_onchain_balance_sats, spendable_onchain_balance_sats) =
+			self.wallet.get_balances(cur_anchor_reserve_sats).unwrap_or((0, 0));
+
+		let total_anchor_channels_reserve_sats =
+			std::cmp::min(cur_anchor_reserve_sats, total_onchain_balance_sats);
 
 		let mut total_lightning_balance_sats = 0;
 		let mut lightning_balances = Vec::new();
@@ -1235,6 +1279,7 @@ impl Node {
 		BalanceDetails {
 			total_onchain_balance_sats,
 			spendable_onchain_balance_sats,
+			total_anchor_channels_reserve_sats,
 			total_lightning_balance_sats,
 			lightning_balances,
 			pending_balances_from_channel_closures,
@@ -1367,3 +1412,23 @@ pub struct NodeStatus {
 	/// Will be `None` if we have no public channels or we haven't broadcasted since the [`Node`] was initialized.
 	pub latest_node_announcement_broadcast_timestamp: Option<u64>,
 }
+
+pub(crate) fn total_anchor_channels_reserve_sats(
+	channel_manager: &ChannelManager, config: &Config,
+) -> u64 {
+	config.anchor_channels_config.as_ref().map_or(0, |anchor_channels_config| {
+		channel_manager
+			.list_channels()
+			.into_iter()
+			.filter(|c| {
+				!anchor_channels_config.trusted_peers_no_reserve.contains(&c.counterparty.node_id)
+					&& c.channel_shutdown_state
+						.map_or(true, |s| s != ChannelShutdownState::ShutdownComplete)
+					&& c.channel_type
+						.as_ref()
+						.map_or(false, |t| t.requires_anchors_zero_fee_htlc_tx())
+			})
+			.count() as u64
+			* anchor_channels_config.per_channel_reserve_sats
+	})
+}

src/payment/onchain.rs

@@ -1,8 +1,9 @@
 //! Holds a payment handler allowing to send and receive on-chain payments.
 
+use crate::config::Config;
 use crate::error::Error;
 use crate::logger::{log_error, log_info, FilesystemLogger, Logger};
-use crate::types::Wallet;
+use crate::types::{ChannelManager, Wallet};
 
 use bitcoin::{Address, Txid};
 
@@ -16,15 +17,17 @@ use std::sync::{Arc, RwLock};
 pub struct OnchainPayment {
 	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
 	wallet: Arc<Wallet>,
+	channel_manager: Arc<ChannelManager>,
+	config: Arc<Config>,
 	logger: Arc<FilesystemLogger>,
 }
 
 impl OnchainPayment {
 	pub(crate) fn new(
 		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>, wallet: Arc<Wallet>,
-		logger: Arc<FilesystemLogger>,
+		channel_manager: Arc<ChannelManager>, config: Arc<Config>, logger: Arc<FilesystemLogger>,
 	) -> Self {
-		Self { runtime, wallet, logger }
+		Self { runtime, wallet, channel_manager, config, logger }
 	}
 
 	/// Retrieve a new on-chain/funding address.
@@ -35,6 +38,11 @@ impl OnchainPayment {
 	}
 
 	/// Send an on-chain payment to the given address.
+	///
+	/// This will respect any on-chain reserve we need to keep, i.e., won't allow to cut into
+	/// [`BalanceDetails::total_anchor_channels_reserve_sats`].
+	///
+	/// [`BalanceDetails::total_anchor_channels_reserve_sats`]: crate::BalanceDetails::total_anchor_channels_reserve_sats
 	pub fn send_to_address(
 		&self, address: &bitcoin::Address, amount_sats: u64,
 	) -> Result<Txid, Error> {
@@ -43,15 +51,29 @@ impl OnchainPayment {
 			return Err(Error::NotRunning);
 		}
 
-		let cur_balance = self.wallet.get_balance()?;
-		if cur_balance.get_spendable() < amount_sats {
-			log_error!(self.logger, "Unable to send payment due to insufficient funds.");
+		let cur_anchor_reserve_sats =
+			crate::total_anchor_channels_reserve_sats(&self.channel_manager, &self.config);
+		let spendable_amount_sats =
+			self.wallet.get_spendable_amount_sats(cur_anchor_reserve_sats).unwrap_or(0);
+
+		if spendable_amount_sats < amount_sats {
+			log_error!(self.logger,
+				"Unable to send payment due to insufficient funds. Available: {}sats, Required: {}sats",
+				spendable_amount_sats, amount_sats
+			);
 			return Err(Error::InsufficientFunds);
 		}
 		self.wallet.send_to_address(address, Some(amount_sats))
 	}
 
 	/// Send an on-chain payment to the given address, draining all the available funds.
+	///
+	/// This is useful if you have closed all channels and want to migrate funds to another
+	/// on-chain wallet.
+	///
+	/// Please note that this will **not** retain any on-chain reserves, which might be potentially
+	/// dangerous if you have open Anchor channels for which you can't trust the counterparty to
+	/// spend the Anchor output after channel closure.
 	pub fn send_all_to_address(&self, address: &bitcoin::Address) -> Result<Txid, Error> {
 		let rt_lock = self.runtime.read().unwrap();
 		if rt_lock.is_none() {

src/wallet.rs

@@ -166,8 +166,23 @@ where
 		Ok(address_info.address)
 	}
 
-	pub(crate) fn get_balance(&self) -> Result<bdk::Balance, Error> {
-		Ok(self.inner.lock().unwrap().get_balance()?)
+	pub(crate) fn get_balances(
+		&self, total_anchor_channels_reserve_sats: u64,
+	) -> Result<(u64, u64), Error> {
+		let wallet_lock = self.inner.lock().unwrap();
+		let (total, spendable) = wallet_lock.get_balance().map(|bal| {
+			(
+				bal.get_total(),
+				bal.get_spendable().saturating_sub(total_anchor_channels_reserve_sats),
+			)
+		})?;
+		Ok((total, spendable))
+	}
+
+	pub(crate) fn get_spendable_amount_sats(
+		&self, total_anchor_channels_reserve_sats: u64,
+	) -> Result<u64, Error> {
+		self.get_balances(total_anchor_channels_reserve_sats).map(|(_, s)| s)
 	}
 
 	/// Send funds to the given address.