Add chain syncing via compact block filters (BIP 157)

.github/workflows/rust.yml

@@ -84,7 +84,11 @@ jobs:
       - name: Test on Rust ${{ matrix.toolchain }}
         if: "matrix.platform != 'windows-latest'"
         run: |
-          RUSTFLAGS="--cfg no_download --cfg cycle_tests" cargo test
+          RUSTFLAGS="--cfg no_download --cfg cycle_tests" cargo test -- --skip cbf
+      - name: Test CBF on Rust ${{ matrix.toolchain }}
+        if: "matrix.platform != 'windows-latest'"
+        run: |
+          RUSTFLAGS="--cfg no_download --cfg cycle_tests" cargo test cbf -- --test-threads=1
       - name: Test with UniFFI support on Rust ${{ matrix.toolchain }}
         if: "matrix.platform != 'windows-latest' && matrix.build-uniffi"
         run: |

Cargo.toml

@@ -57,6 +57,7 @@ lightning-dns-resolver = { git = "https://github.com/lightningdevkit/rust-lightn
 bdk_chain = { version = "0.23.0", default-features = false, features = ["std"] }
 bdk_esplora = { version = "0.22.0", default-features = false, features = ["async-https-rustls", "tokio"]}
 bdk_electrum = { version = "0.24.0", default-features = false, features = ["use-rustls-ring"]}
+bip157 = { version = "0.6.0", default-features = false }
 bdk_wallet = { version = "2.3.0", default-features = false, features = ["std", "keys-bip39"]}
 
 bitreq = { version = "0.3", default-features = false, features = ["async-https", "json-using-serde"] }

README.md

@@ -61,7 +61,7 @@ fn main() {
 LDK Node currently comes with a decidedly opinionated set of design choices:
 
 - On-chain data is handled by the integrated [BDK][bdk] wallet.
-- Chain data may currently be sourced from the Bitcoin Core RPC interface, or from an [Electrum][electrum] or [Esplora][esplora] server.
+- Chain data may currently be sourced from the Bitcoin Core RPC interface, from an [Electrum][electrum] or [Esplora][esplora] server, or via [compact block filters (BIP 157)][bip157].
 - Wallet and channel state may be persisted to an [SQLite][sqlite] database, to file system, or to a custom back-end to be implemented by the user.
 - Gossip data may be sourced via Lightning's peer-to-peer network or the [Rapid Gossip Sync](https://docs.rs/lightning-rapid-gossip-sync/*/lightning_rapid_gossip_sync/) protocol.
 - Entropy for the Lightning and on-chain wallets may be sourced from raw bytes or a [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki) mnemonic. In addition, LDK Node offers the means to generate and persist the entropy bytes to disk.
@@ -80,6 +80,7 @@ The Minimum Supported Rust Version (MSRV) is currently 1.85.0.
 [bdk]: https://bitcoindevkit.org/
 [electrum]: https://github.com/spesmilo/electrum-protocol
 [esplora]: https://github.com/Blockstream/esplora
+[bip157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki
 [sqlite]: https://sqlite.org/
 [rust]: https://www.rust-lang.org/
 [swift]: https://www.swift.org/

bindings/ldk_node.udl

@@ -9,6 +9,8 @@ typedef dictionary EsploraSyncConfig;
 
 typedef dictionary ElectrumSyncConfig;
 
+typedef dictionary CbfSyncConfig;
+
 typedef dictionary TorConfig;
 
 typedef interface NodeEntropy;
@@ -38,6 +40,7 @@ interface Builder {
 	constructor(Config config);
 	void set_chain_source_esplora(string server_url, EsploraSyncConfig? config);
 	void set_chain_source_electrum(string server_url, ElectrumSyncConfig? config);
+	void set_chain_source_cbf(sequence<string> peers, CbfSyncConfig? sync_config, FeeSourceConfig? fee_source_config);
 	void set_chain_source_bitcoind_rpc(string rpc_host, u16 rpc_port, string rpc_user, string rpc_password);
 	void set_chain_source_bitcoind_rest(string rest_host, u16 rest_port, string rpc_host, u16 rpc_port, string rpc_user, string rpc_password);
 	void set_gossip_source_p2p();
@@ -354,6 +357,8 @@ enum Currency {
 
 typedef enum AsyncPaymentsRole;
 
+typedef enum FeeSourceConfig;
+
 [Custom]
 typedef string Txid;
 

src/builder.rs

@@ -45,11 +45,12 @@ use lightning::util::sweep::OutputSweeper;
 use lightning_dns_resolver::OMDomainResolver;
 use vss_client::headers::VssHeaderProvider;
 
-use crate::chain::ChainSource;
+use crate::chain::{ChainSource, FeeSourceConfig};
 use crate::config::{
 	default_user_config, may_announce_channel, AnnounceError, AsyncPaymentsRole,
-	BitcoindRestClientConfig, Config, ElectrumSyncConfig, EsploraSyncConfig, HRNResolverConfig,
-	TorConfig, DEFAULT_ESPLORA_SERVER_URL, DEFAULT_LOG_FILENAME, DEFAULT_LOG_LEVEL,
+	BitcoindRestClientConfig, CbfSyncConfig, Config, ElectrumSyncConfig, EsploraSyncConfig,
+	HRNResolverConfig, TorConfig, DEFAULT_ESPLORA_SERVER_URL, DEFAULT_LOG_FILENAME,
+	DEFAULT_LOG_LEVEL,
 };
 use crate::connection::ConnectionManager;
 use crate::entropy::NodeEntropy;
@@ -108,6 +109,11 @@ enum ChainDataSourceConfig {
 		rpc_password: String,
 		rest_client_config: Option<BitcoindRestClientConfig>,
 	},
+	Cbf {
+		peers: Vec<String>,
+		sync_config: Option<CbfSyncConfig>,
+		fee_source_config: Option<FeeSourceConfig>,
+	},
 }
 
 #[derive(Debug, Clone)]
@@ -376,6 +382,28 @@ impl NodeBuilder {
 		self
 	}
 
+	/// Configures the [`Node`] instance to source its chain data via BIP 157 compact block
+	/// filters.
+	///
+	/// `peers` is an optional list of peer addresses to connect to for sourcing compact block
+	/// filters. If empty, the node will discover peers via DNS seeds.
+	///
+	/// If no `sync_config` is given, default values are used. See [`CbfSyncConfig`] for more
+	/// information.
+	///
+	/// Note: fee rate estimation with this chain source uses block-level averages (total fees
+	/// divided by block weight) rather than per-transaction fee rates. This can underestimate
+	/// next-block inclusion rates during periods of high mempool congestion. Percentile-based
+	/// target selection partially mitigates this.
+	pub fn set_chain_source_cbf(
+		&mut self, peers: Vec<String>, sync_config: Option<CbfSyncConfig>,
+		fee_source_config: Option<FeeSourceConfig>,
+	) -> &mut Self {
+		self.chain_data_source_config =
+			Some(ChainDataSourceConfig::Cbf { peers, sync_config, fee_source_config });
+		self
+	}
+
 	/// Configures the [`Node`] instance to connect to a Bitcoin Core node via RPC.
 	///
 	/// This method establishes an RPC connection that enables all essential chain operations including
@@ -970,6 +998,30 @@ impl ArcedNodeBuilder {
 		self.inner.write().expect("lock").set_chain_source_electrum(server_url, sync_config);
 	}
 
+	/// Configures the [`Node`] instance to source its chain data via BIP 157 compact block
+	/// filters.
+	///
+	/// `peers` is an optional list of peer addresses to connect to for sourcing compact block
+	/// filters. If empty, the node will discover peers via DNS seeds.
+	///
+	/// If no `sync_config` is given, default values are used. See [`CbfSyncConfig`] for more
+	/// information.
+	///
+	/// Note: fee rate estimation with this chain source uses block-level averages (total fees
+	/// divided by block weight) rather than per-transaction fee rates. This can underestimate
+	/// next-block inclusion rates during periods of high mempool congestion. Percentile-based
+	/// target selection partially mitigates this.
+	pub fn set_chain_source_cbf(
+		&self, peers: Vec<String>, sync_config: Option<CbfSyncConfig>,
+		fee_source_config: Option<FeeSourceConfig>,
+	) {
+		self.inner.write().expect("lock").set_chain_source_cbf(
+			peers,
+			sync_config,
+			fee_source_config,
+		);
+	}
+
 	/// Configures the [`Node`] instance to connect to a Bitcoin Core node via RPC.
 	///
 	/// This method establishes an RPC connection that enables all essential chain operations including
@@ -1509,6 +1561,25 @@ fn build_with_store_internal(
 			}),
 		},
 
+		Some(ChainDataSourceConfig::Cbf { peers, sync_config, fee_source_config }) => {
+			let sync_config = sync_config.clone().unwrap_or(CbfSyncConfig::default());
+			ChainSource::new_cbf(
+				peers.clone(),
+				sync_config,
+				fee_source_config.clone(),
+				Arc::clone(&fee_estimator),
+				Arc::clone(&tx_broadcaster),
+				Arc::clone(&kv_store),
+				Arc::clone(&config),
+				Arc::clone(&logger),
+				Arc::clone(&node_metrics),
+			)
+			.map_err(|e| {
+				log_error!(logger, "Failed to initialize CBF chain source: {}", e);
+				BuildError::ChainSourceSetupFailed
+			})?
+		},
+
 		None => {
 			// Default to Esplora client.
 			let server_url = DEFAULT_ESPLORA_SERVER_URL.to_string();
@@ -2261,6 +2332,9 @@ pub(crate) fn sanitize_alias(alias_str: &str) -> Result<NodeAlias, BuildError> {
 
 #[cfg(test)]
 mod tests {
+	#[cfg(feature = "uniffi")]
+	use crate::config::CbfSyncConfig;
+
 	use super::{sanitize_alias, BuildError, NodeAlias};
 
 	#[test]
@@ -2298,4 +2372,24 @@ mod tests {
 		let node = sanitize_alias(alias);
 		assert_eq!(node.err().unwrap(), BuildError::InvalidNodeAlias);
 	}
+
+	#[cfg(feature = "uniffi")]
+	#[test]
+	fn arced_builder_can_set_cbf_chain_source() {
+		let builder = super::ArcedNodeBuilder::new();
+		let sync_config = CbfSyncConfig::default();
+
+		let peers = vec!["127.0.0.1:8333".to_string()];
+		builder.set_chain_source_cbf(peers.clone(), Some(sync_config.clone()), None);
+
+		let guard = builder.inner.read().unwrap();
+		assert!(matches!(
+			guard.chain_data_source_config.as_ref(),
+			Some(super::ChainDataSourceConfig::Cbf {
+				peers: p,
+				sync_config: Some(config),
+				..
+			}) if config == &sync_config && p == &peers
+		));
+	}
 }