Support filtered blocks in lightning-block-sync

Expand the BlockSource trait to allow filtered blocks now that
chain::Listen supports them (d629a7e).
This makes it possible to use BIP 157/158 compact block filters with
lightning-block-sync.

Author: jkczyz

lightning-block-sync/src/init.rs

@@ -216,6 +216,16 @@ impl<'a, L: chain::Listen + ?Sized> chain::Listen for DynamicChainListener<'a, L
 struct ChainListenerSet<'a, L: chain::Listen + ?Sized>(Vec<(u32, &'a L)>);
 
 impl<'a, L: chain::Listen + ?Sized> chain::Listen for ChainListenerSet<'a, L> {
+	// Needed to differentiate test expectations.
+	#[cfg(test)]
+	fn block_connected(&self, block: &bitcoin::Block, height: u32) {
+		for (starting_height, chain_listener) in self.0.iter() {
+			if height > *starting_height {
+				chain_listener.block_connected(block, height);
+			}
+		}
+	}
+
 	fn filtered_block_connected(&self, header: &BlockHeader, txdata: &chain::transaction::TransactionData, height: u32) {
 		for (starting_height, chain_listener) in self.0.iter() {
 			if height > *starting_height {

lightning-block-sync/src/lib.rs

@@ -68,7 +68,7 @@ pub trait BlockSource : Sync + Send {
 
 	/// Returns the block for a given hash. A headers-only block source should return a `Transient`
 	/// error.
-	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block>;
+	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, BlockData>;
 
 	/// Returns the hash of the best block and, optionally, its height.
 	///
@@ -152,6 +152,18 @@ pub struct BlockHeaderData {
 	pub chainwork: Uint256,
 }
 
+/// A block including either all its transactions or only the block header.
+///
+/// [`BlockSource`] may be implemented to either always return full blocks or, in the case of
+/// compact block filters (BIP 157/158), return header-only blocks when no pertinent transactions
+/// match. See [`chain::Filter`] for details on how to notify a source of such transactions.
+pub enum BlockData {
+	/// A block containing all its transactions.
+	FullBlock(Block),
+	/// A block header for when the block does not contain any pertinent transactions.
+	HeaderOnly(BlockHeader),
+}
+
 /// A lightweight client for keeping a listener in sync with the chain, allowing for Simplified
 /// Payment Verification (SPV).
 ///
@@ -396,13 +408,22 @@ impl<'a, C: Cache, L: Deref> ChainNotifier<'a, C, L> where L::Target: chain::Lis
 		chain_poller: &mut P,
 	) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
 		for header in connected_blocks.drain(..).rev() {
-			let block = chain_poller
+			let height = header.height;
+			let block_data = chain_poller
 				.fetch_block(&header).await
 				.or_else(|e| Err((e, Some(new_tip))))?;
-			debug_assert_eq!(block.block_hash, header.block_hash);
+			debug_assert_eq!(block_data.block_hash, header.block_hash);
+
+			match block_data.deref() {
+				BlockData::FullBlock(block) => {
+					self.chain_listener.block_connected(&block, height);
+				},
+				BlockData::HeaderOnly(header) => {
+					self.chain_listener.filtered_block_connected(&header, &[], height);
+				},
+			}
 
 			self.header_cache.block_connected(header.block_hash, header);
-			self.chain_listener.block_connected(&block, header.height);
 			new_tip = header;
 		}
 
@@ -707,4 +728,25 @@ mod chain_notifier_tests {
 			Ok(_) => panic!("Expected error"),
 		}
 	}
+
+	#[tokio::test]
+	async fn sync_from_chain_with_filtered_blocks() {
+		let mut chain = Blockchain::default().with_height(3).filtered_blocks();
+
+		let new_tip = chain.tip();
+		let old_tip = chain.at_height(1);
+		let chain_listener = &MockChainListener::new()
+			.expect_filtered_block_connected(*chain.at_height(2))
+			.expect_filtered_block_connected(*new_tip);
+		let mut notifier = ChainNotifier {
+			header_cache: &mut chain.header_cache(0..=1),
+			chain_listener,
+		};
+		let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+		match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
+			Err((e, _)) => panic!("Unexpected error: {:?}", e),
+			Ok(_) => {},
+		}
+	}
+
 }

lightning-block-sync/src/poll.rs

@@ -1,8 +1,7 @@
 //! Adapters that make one or more [`BlockSource`]s simpler to poll for new chain tip transitions.
 
-use crate::{AsyncBlockSourceResult, BlockHeaderData, BlockSource, BlockSourceError, BlockSourceResult};
+use crate::{AsyncBlockSourceResult, BlockData, BlockHeaderData, BlockSource, BlockSourceError, BlockSourceResult};
 
-use bitcoin::blockdata::block::Block;
 use bitcoin::hash_types::BlockHash;
 use bitcoin::network::constants::Network;
 
@@ -71,24 +70,31 @@ impl Validate for BlockHeaderData {
 	}
 }
 
-impl Validate for Block {
+impl Validate for BlockData {
 	type T = ValidatedBlock;
 
 	fn validate(self, block_hash: BlockHash) -> BlockSourceResult<Self::T> {
-		let pow_valid_block_hash = self.header
-			.validate_pow(&self.header.target())
+		let header = match &self {
+			BlockData::FullBlock(block) => &block.header,
+			BlockData::HeaderOnly(header) => header,
+		};
+
+		let pow_valid_block_hash = header
+			.validate_pow(&header.target())
 			.or_else(|e| Err(BlockSourceError::persistent(e)))?;
 
 		if pow_valid_block_hash != block_hash {
 			return Err(BlockSourceError::persistent("invalid block hash"));
 		}
 
-		if !self.check_merkle_root() {
-			return Err(BlockSourceError::persistent("invalid merkle root"));
-		}
+		if let BlockData::FullBlock(block) = &self {
+			if !block.check_merkle_root() {
+				return Err(BlockSourceError::persistent("invalid merkle root"));
+			}
 
-		if !self.check_witness_commitment() {
-			return Err(BlockSourceError::persistent("invalid witness commitment"));
+			if !block.check_witness_commitment() {
+				return Err(BlockSourceError::persistent("invalid witness commitment"));
+			}
 		}
 
 		Ok(ValidatedBlock { block_hash, inner: self })
@@ -145,11 +151,11 @@ impl ValidatedBlockHeader {
 /// A block with validated data against its transaction list and corresponding block hash.
 pub struct ValidatedBlock {
 	pub(crate) block_hash: BlockHash,
-	inner: Block,
+	inner: BlockData,
 }
 
 impl std::ops::Deref for ValidatedBlock {
-	type Target = Block;
+	type Target = BlockData;
 
 	fn deref(&self) -> &Self::Target {
 		&self.inner
@@ -161,7 +167,7 @@ mod sealed {
 	pub trait Validate {}
 
 	impl Validate for crate::BlockHeaderData {}
-	impl Validate for bitcoin::blockdata::block::Block {}
+	impl Validate for crate::BlockData {}
 }
 
 /// The canonical `Poll` implementation used for a single `BlockSource`.

lightning-block-sync/src/rest.rs

@@ -1,10 +1,9 @@
 //! Simple REST client implementation which implements [`BlockSource`] against a Bitcoin Core REST
 //! endpoint.
 
-use crate::{BlockHeaderData, BlockSource, AsyncBlockSourceResult};
+use crate::{BlockData, BlockHeaderData, BlockSource, AsyncBlockSourceResult};
 use crate::http::{BinaryResponse, HttpEndpoint, HttpClient, JsonResponse};
 
-use bitcoin::blockdata::block::Block;
 use bitcoin::hash_types::BlockHash;
 use bitcoin::hashes::hex::ToHex;
 
@@ -45,10 +44,10 @@ impl BlockSource for RestClient {
 		})
 	}
 
-	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block> {
+	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, BlockData> {
 		Box::pin(async move {
 			let resource_path = format!("block/{}.bin", header_hash.to_hex());
-			Ok(self.request_resource::<BinaryResponse, _>(&resource_path).await?)
+			Ok(BlockData::FullBlock(self.request_resource::<BinaryResponse, _>(&resource_path).await?))
 		})
 	}
 

lightning-block-sync/src/rpc.rs

@@ -1,10 +1,9 @@
 //! Simple RPC client implementation which implements [`BlockSource`] against a Bitcoin Core RPC
 //! endpoint.
 
-use crate::{BlockHeaderData, BlockSource, AsyncBlockSourceResult};
+use crate::{BlockData, BlockHeaderData, BlockSource, AsyncBlockSourceResult};
 use crate::http::{HttpClient, HttpEndpoint, HttpError, JsonResponse};
 
-use bitcoin::blockdata::block::Block;
 use bitcoin::hash_types::BlockHash;
 use bitcoin::hashes::hex::ToHex;
 
@@ -91,11 +90,11 @@ impl BlockSource for RpcClient {
 		})
 	}
 
-	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block> {
+	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, BlockData> {
 		Box::pin(async move {
 			let header_hash = serde_json::json!(header_hash.to_hex());
 			let verbosity = serde_json::json!(0);
-			Ok(self.call_method("getblock", &[header_hash, verbosity]).await?)
+			Ok(BlockData::FullBlock(self.call_method("getblock", &[header_hash, verbosity]).await?))
 		})
 	}
 

lightning-block-sync/src/test_utils.rs

@@ -1,4 +1,4 @@
-use crate::{AsyncBlockSourceResult, BlockHeaderData, BlockSource, BlockSourceError, UnboundedCache};
+use crate::{AsyncBlockSourceResult, BlockData, BlockHeaderData, BlockSource, BlockSourceError, UnboundedCache};
 use crate::poll::{Validate, ValidatedBlockHeader};
 
 use bitcoin::blockdata::block::{Block, BlockHeader};
@@ -20,6 +20,7 @@ pub struct Blockchain {
 	without_blocks: Option<std::ops::RangeFrom<usize>>,
 	without_headers: bool,
 	malformed_headers: bool,
+	filtered_blocks: bool,
 }
 
 impl Blockchain {
@@ -77,6 +78,10 @@ impl Blockchain {
 		Self { malformed_headers: true, ..self }
 	}
 
+	pub fn filtered_blocks(self) -> Self {
+		Self { filtered_blocks: true, ..self }
+	}
+
 	pub fn fork_at_height(&self, height: usize) -> Self {
 		assert!(height + 1 < self.blocks.len());
 		let mut blocks = self.blocks.clone();
@@ -146,7 +151,7 @@ impl BlockSource for Blockchain {
 		})
 	}
 
-	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block> {
+	fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, BlockData> {
 		Box::pin(async move {
 			for (height, block) in self.blocks.iter().enumerate() {
 				if block.header.block_hash() == *header_hash {
@@ -156,7 +161,11 @@ impl BlockSource for Blockchain {
 						}
 					}
 
-					return Ok(block.clone());
+					if self.filtered_blocks {
+						return Ok(BlockData::HeaderOnly(block.header.clone()));
+					} else {
+						return Ok(BlockData::FullBlock(block.clone()));
+					}
 				}
 			}
 			Err(BlockSourceError::transient("block not found"))
@@ -185,13 +194,15 @@ impl chain::Listen for NullChainListener {
 
 pub struct MockChainListener {
 	expected_blocks_connected: RefCell<VecDeque<BlockHeaderData>>,
+	expected_filtered_blocks_connected: RefCell<VecDeque<BlockHeaderData>>,
 	expected_blocks_disconnected: RefCell<VecDeque<BlockHeaderData>>,
 }
 
 impl MockChainListener {
 	pub fn new() -> Self {
 		Self {
 			expected_blocks_connected: RefCell::new(VecDeque::new()),
+			expected_filtered_blocks_connected: RefCell::new(VecDeque::new()),
 			expected_blocks_disconnected: RefCell::new(VecDeque::new()),
 		}
 	}
@@ -201,17 +212,34 @@ impl MockChainListener {
 		self
 	}
 
+	pub fn expect_filtered_block_connected(self, block: BlockHeaderData) -> Self {
+		self.expected_filtered_blocks_connected.borrow_mut().push_back(block);
+		self
+	}
+
 	pub fn expect_block_disconnected(self, block: BlockHeaderData) -> Self {
 		self.expected_blocks_disconnected.borrow_mut().push_back(block);
 		self
 	}
 }
 
 impl chain::Listen for MockChainListener {
-	fn filtered_block_connected(&self, header: &BlockHeader, _txdata: &chain::transaction::TransactionData, height: u32) {
+	fn block_connected(&self, block: &Block, height: u32) {
 		match self.expected_blocks_connected.borrow_mut().pop_front() {
 			None => {
-				panic!("Unexpected block connected: {:?}", header.block_hash());
+				panic!("Unexpected block connected: {:?}", block.block_hash());
+			},
+			Some(expected_block) => {
+				assert_eq!(block.block_hash(), expected_block.header.block_hash());
+				assert_eq!(height, expected_block.height);
+			},
+		}
+	}
+
+	fn filtered_block_connected(&self, header: &BlockHeader, _txdata: &chain::transaction::TransactionData, height: u32) {
+		match self.expected_filtered_blocks_connected.borrow_mut().pop_front() {
+			None => {
+				panic!("Unexpected filtered block connected: {:?}", header.block_hash());
 			},
 			Some(expected_block) => {
 				assert_eq!(header.block_hash(), expected_block.header.block_hash());
@@ -244,6 +272,11 @@ impl Drop for MockChainListener {
 			panic!("Expected blocks connected: {:?}", expected_blocks_connected);
 		}
 
+		let expected_filtered_blocks_connected = self.expected_filtered_blocks_connected.borrow();
+		if !expected_filtered_blocks_connected.is_empty() {
+			panic!("Expected filtered_blocks connected: {:?}", expected_filtered_blocks_connected);
+		}
+
 		let expected_blocks_disconnected = self.expected_blocks_disconnected.borrow();
 		if !expected_blocks_disconnected.is_empty() {
 			panic!("Expected blocks disconnected: {:?}", expected_blocks_disconnected);