Allow specifying a fee rate for channel-open funding transactions

CHANGELOG.md

@@ -30,6 +30,10 @@
   `Event::PaymentClaimable`.
 
 ## Feature and API updates
+- All `Node::open_channel` variants now take an optional `FeeRate` (after
+  `push_to_counterparty_msat`) that, when set, is used for the channel's funding transaction instead of the internal fee estimation. For the
+  `_with_all` variants it also determines the rate at which the maximum funding amount is
+  computed. When unset, behavior is unchanged.
 - Language-binding `Mnemonic` objects can be generated or constructed from entropy and expose
   their words, word indices, word count, entropy, checksum, and passphrase-derived seed.
 - `Node::list_payments` is now paginated: it takes an optional `PageToken` and returns a

README.md

@@ -45,7 +45,7 @@ fn main() {
 
 	let node_id = PublicKey::from_str("NODE_ID").unwrap();
 	let node_addr = SocketAddress::from_str("IP_ADDR:PORT").unwrap();
-	node.open_channel(node_id, node_addr, 10000, None, None).unwrap();
+	node.open_channel(node_id, node_addr, 10000, None, None, None).unwrap();
 
 	let event = node.wait_next_event();
 	println!("EVENT: {:?}", event);

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

@@ -253,7 +253,7 @@ class LibraryTest {
         assertEquals(100000uL, totalBalance1)
         assertEquals(100000uL, totalBalance2)
 
-        node1.openChannel(nodeId2, listenAddress2, 50000u, null, null)
+        node1.openChannel(nodeId2, listenAddress2, 50000u, null, null, null)
 
         val channelPendingEvent1 = node1.waitNextEvent()
         println("Got event: $channelPendingEvent1")

bindings/ldk_node.udl

@@ -78,17 +78,17 @@ interface Node {
 	[Throws=NodeError]
 	void disconnect(PublicKey node_id);
 	[Throws=NodeError]
-	UserChannelId open_channel(PublicKey node_id, SocketAddress address, u64 channel_amount_sats, u64? push_to_counterparty_msat, ChannelConfig? channel_config);
+	UserChannelId open_channel(PublicKey node_id, SocketAddress address, u64 channel_amount_sats, u64? push_to_counterparty_msat, FeeRate? fee_rate, ChannelConfig? channel_config);
 	[Throws=NodeError]
-	UserChannelId open_announced_channel(PublicKey node_id, SocketAddress address, u64 channel_amount_sats, u64? push_to_counterparty_msat, ChannelConfig? channel_config);
+	UserChannelId open_announced_channel(PublicKey node_id, SocketAddress address, u64 channel_amount_sats, u64? push_to_counterparty_msat, FeeRate? fee_rate, ChannelConfig? channel_config);
 	[Throws=NodeError]
-	UserChannelId open_channel_with_all(PublicKey node_id, SocketAddress address, u64? push_to_counterparty_msat, ChannelConfig? channel_config);
+	UserChannelId open_channel_with_all(PublicKey node_id, SocketAddress address, u64? push_to_counterparty_msat, FeeRate? fee_rate, ChannelConfig? channel_config);
 	[Throws=NodeError]
-	UserChannelId open_announced_channel_with_all(PublicKey node_id, SocketAddress address, u64? push_to_counterparty_msat, ChannelConfig? channel_config);
+	UserChannelId open_announced_channel_with_all(PublicKey node_id, SocketAddress address, u64? push_to_counterparty_msat, FeeRate? fee_rate, ChannelConfig? channel_config);
 	[Throws=NodeError]
-	UserChannelId open_0reserve_channel(PublicKey node_id, SocketAddress address, u64 channel_amount_sats, u64? push_to_counterparty_msat, ChannelConfig? channel_config);
+	UserChannelId open_0reserve_channel(PublicKey node_id, SocketAddress address, u64 channel_amount_sats, u64? push_to_counterparty_msat, FeeRate? fee_rate, ChannelConfig? channel_config);
 	[Throws=NodeError]
-	UserChannelId open_0reserve_channel_with_all(PublicKey node_id, SocketAddress address, u64? push_to_counterparty_msat, ChannelConfig? channel_config);
+	UserChannelId open_0reserve_channel_with_all(PublicKey node_id, SocketAddress address, u64? push_to_counterparty_msat, FeeRate? fee_rate, ChannelConfig? channel_config);
 	[Throws=NodeError]
 	void splice_in([ByRef]UserChannelId user_channel_id, PublicKey counterparty_node_id, u64 splice_amount_sats);
 	[Throws=NodeError]

bindings/python/src/ldk_node/test_ldk_node.py

@@ -159,7 +159,7 @@ def fund_nodes(node_1, node_2, esplora_endpoint, amount_sats=100000):
     node_2.sync_wallets()
 
 def open_channel_and_wait_ready(node_1, node_2, node_id_2, listening_address_2, esplora_endpoint, channel_amount_sats=50000):
-    node_1.open_channel(node_id_2, listening_address_2, channel_amount_sats, None, None)
+    node_1.open_channel(node_id_2, listening_address_2, channel_amount_sats, None, None, None)
 
     channel_pending_event_1 = expect_event(node_1, Event.CHANNEL_PENDING)
     expect_event(node_2, Event.CHANNEL_PENDING)

src/builder.rs

@@ -2556,6 +2556,7 @@ fn build_with_store_internal(
 		node_metrics,
 		om_mailbox,
 		async_payments_role,
+		pending_funding_fee_rates: Arc::new(Mutex::new(std::collections::HashMap::new())),
 		#[cfg(feature = "unified-payments")]
 		hrn_resolver,
 		prober,

src/event.rs

@@ -7,13 +7,13 @@
 
 use core::future::Future;
 use core::task::{Poll, Waker};
-use std::collections::VecDeque;
+use std::collections::{HashMap, VecDeque};
 use std::ops::Deref;
 use std::sync::{Arc, Mutex};
 
 use bitcoin::blockdata::locktime::absolute::LockTime;
 use bitcoin::secp256k1::PublicKey;
-use bitcoin::{Amount, OutPoint};
+use bitcoin::{Amount, FeeRate, OutPoint};
 use lightning::blinded_path::message::NextMessageHop;
 use lightning::events::bump_transaction::BumpTransactionEvent;
 #[cfg(not(feature = "uniffi"))]
@@ -574,6 +574,7 @@ where
 	runtime: Arc<Runtime>,
 	logger: L,
 	config: Arc<Config>,
+	pending_funding_fee_rates: Arc<Mutex<HashMap<u128, FeeRate>>>,
 }
 
 impl<L: Deref + Clone + Sync + Send + 'static> EventHandler<L>
@@ -590,6 +591,7 @@ where
 		keys_manager: Arc<KeysManager>, static_invoice_store: Option<StaticInvoiceStore>,
 		onion_messenger: Arc<OnionMessenger>, om_mailbox: Option<Arc<OnionMessageMailbox>>,
 		prober: Option<Arc<Prober>>, runtime: Arc<Runtime>, logger: L, config: Arc<Config>,
+		pending_funding_fee_rates: Arc<Mutex<HashMap<u128, FeeRate>>>,
 	) -> Self {
 		Self {
 			event_queue,
@@ -611,6 +613,7 @@ where
 			runtime,
 			logger,
 			config,
+			pending_funding_fee_rates,
 		}
 	}
 
@@ -750,6 +753,10 @@ where
 				let cur_height = self.channel_manager.current_best_block().height;
 				let locktime = LockTime::from_height(cur_height).unwrap_or(LockTime::ZERO);
 
+				// Look up and remove any pending fee-rate override for this channel.
+				let fee_rate_override =
+					self.pending_funding_fee_rates.lock().expect("lock").remove(&user_channel_id);
+
 				// Sign the final funding transaction and broadcast it.
 				let channel_amount = Amount::from_sat(channel_value_satoshis);
 				let funding_transaction = self
@@ -759,6 +766,7 @@ where
 						channel_amount,
 						confirmation_target,
 						locktime,
+						fee_rate_override,
 					)
 					.await;
 				match funding_transaction {
@@ -1935,6 +1943,10 @@ where
 			} => {
 				log_info!(self.logger, "Channel {} closed due to: {}", channel_id, reason);
 
+				// Clean up any funding fee-rate override still pending if the channel went
+				// away before the funding transaction was generated.
+				self.pending_funding_fee_rates.lock().expect("lock").remove(&user_channel_id);
+
 				// `counterparty_node_id` has been set on every `ChannelClosed` since LDK 0.0.117.
 				let counterparty_node_id = counterparty_node_id
 					.expect("counterparty_node_id is always set since LDK 0.0.117");

src/ffi/mod.rs

@@ -31,6 +31,14 @@ pub fn maybe_wrap<T>(ldk_type: impl Into<T>) -> std::sync::Arc<T> {
 	std::sync::Arc::new(ldk_type.into())
 }
 
+#[cfg(feature = "uniffi")]
+pub(crate) type FfiFeeRate = std::sync::Arc<bitcoin::FeeRate>;
+
+#[cfg(feature = "uniffi")]
+pub(crate) fn maybe_map_fee_rate_opt(fee_rate: Option<FfiFeeRate>) -> Option<bitcoin::FeeRate> {
+	fee_rate.map(|f| *f)
+}
+
 #[cfg(not(feature = "uniffi"))]
 pub fn maybe_deref<T>(value: &T) -> &T {
 	value
@@ -45,3 +53,11 @@ pub fn maybe_try_convert_enum<T>(value: &T) -> Result<&T, crate::error::Error> {
 pub fn maybe_wrap<T>(value: T) -> T {
 	value
 }
+
+#[cfg(not(feature = "uniffi"))]
+pub(crate) type FfiFeeRate = bitcoin::FeeRate;
+
+#[cfg(not(feature = "uniffi"))]
+pub(crate) fn maybe_map_fee_rate_opt(fee_rate: Option<FfiFeeRate>) -> Option<bitcoin::FeeRate> {
+	fee_rate
+}