//! A lightweight client for keeping in sync with chain activity.
//!
+//! Defines an [`SpvClient`] utility for polling one or more block sources for the best chain tip.
+//! It is used to notify listeners of blocks connected or disconnected since the last poll. Useful
+//! for keeping a Lightning node in sync with the chain.
+//!
//! Defines a [`BlockSource`] trait, which is an asynchronous interface for retrieving block headers
//! and data.
//!
//! Both features support either blocking I/O using `std::net::TcpStream` or, with feature `tokio`,
//! non-blocking I/O using `tokio::net::TcpStream` from inside a Tokio runtime.
//!
+//! [`SpvClient`]: struct.SpvClient.html
//! [`BlockSource`]: trait.BlockSource.html
+#![deny(broken_intra_doc_links)]
+#![deny(unsafe_code)]
+
#[cfg(any(feature = "rest-client", feature = "rpc-client"))]
pub mod http;
+pub mod init;
pub mod poll;
#[cfg(feature = "rest-client")]
#[cfg(any(feature = "rest-client", feature = "rpc-client"))]
mod utils;
-use crate::poll::{Poll, ValidatedBlockHeader};
+use crate::poll::{ChainTip, Poll, ValidatedBlockHeader};
use bitcoin::blockdata::block::{Block, BlockHeader};
use bitcoin::hash_types::BlockHash;
use bitcoin::util::uint::Uint256;
+use lightning::chain;
+use lightning::chain::Listen;
+
use std::future::Future;
+use std::ops::Deref;
use std::pin::Pin;
/// Abstract type for retrieving block headers and data.
/// error.
fn get_block<'a>(&'a mut self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, Block>;
- // TODO: Phrase in terms of `Poll` once added.
- /// Returns the hash of the best block and, optionally, its height. When polling a block source,
- /// the height is passed to `get_header` to allow for a more efficient lookup.
+ /// Returns the hash of the best block and, optionally, its height.
+ ///
+ /// When polling a block source, [`Poll`] implementations may pass the height to [`get_header`]
+ /// to allow for a more efficient lookup.
+ ///
+ /// [`Poll`]: poll/trait.Poll.html
+ /// [`get_header`]: #tymethod.get_header
fn get_best_block<'a>(&'a mut self) -> AsyncBlockSourceResult<(BlockHash, Option<u32>)>;
}
pub chainwork: Uint256,
}
-/// Adaptor used for notifying when blocks have been connected or disconnected from the chain.
+/// A lightweight client for keeping a listener in sync with the chain, allowing for Simplified
+/// Payment Verification (SPV).
///
-/// Used when needing to replay chain data upon startup or as new chain events occur.
-pub trait ChainListener {
- /// Notifies the listener that a block was added at the given height.
- fn block_connected(&mut self, block: &Block, height: u32);
-
- /// Notifies the listener that a block was removed at the given height.
- fn block_disconnected(&mut self, header: &BlockHeader, height: u32);
+/// The client is parameterized by a chain poller which is responsible for polling one or more block
+/// sources for the best chain tip. During this process it detects any chain forks, determines which
+/// constitutes the best chain, and updates the listener accordingly with any blocks that were
+/// connected or disconnected since the last poll.
+///
+/// Block headers for the best chain are maintained in the parameterized cache, allowing for a
+/// custom cache eviction policy. This offers flexibility to those sensitive to resource usage.
+/// Hence, there is a trade-off between a lower memory footprint and potentially increased network
+/// I/O as headers are re-fetched during fork detection.
+pub struct SpvClient<'a, P: Poll, C: Cache, L: Deref>
+where L::Target: chain::Listen {
+ chain_tip: ValidatedBlockHeader,
+ chain_poller: P,
+ chain_notifier: ChainNotifier<'a, C, L>,
}
/// The `Cache` trait defines behavior for managing a block header cache, where block headers are
}
}
+impl<'a, P: Poll, C: Cache, L: Deref> SpvClient<'a, P, C, L> where L::Target: chain::Listen {
+ /// Creates a new SPV client using `chain_tip` as the best known chain tip.
+ ///
+ /// Subsequent calls to [`poll_best_tip`] will poll for the best chain tip using the given chain
+ /// poller, which may be configured with one or more block sources to query. At least one block
+ /// source must provide headers back from the best chain tip to its common ancestor with
+ /// `chain_tip`.
+ /// * `header_cache` is used to look up and store headers on the best chain
+ /// * `chain_listener` is notified of any blocks connected or disconnected
+ ///
+ /// [`poll_best_tip`]: struct.SpvClient.html#method.poll_best_tip
+ pub fn new(
+ chain_tip: ValidatedBlockHeader,
+ chain_poller: P,
+ header_cache: &'a mut C,
+ chain_listener: L,
+ ) -> Self {
+ let chain_notifier = ChainNotifier { header_cache, chain_listener };
+ Self { chain_tip, chain_poller, chain_notifier }
+ }
+
+ /// Polls for the best tip and updates the chain listener with any connected or disconnected
+ /// blocks accordingly.
+ ///
+ /// Returns the best polled chain tip relative to the previous best known tip and whether any
+ /// blocks were indeed connected or disconnected.
+ pub async fn poll_best_tip(&mut self) -> BlockSourceResult<(ChainTip, bool)> {
+ let chain_tip = self.chain_poller.poll_chain_tip(self.chain_tip).await?;
+ let blocks_connected = match chain_tip {
+ ChainTip::Common => false,
+ ChainTip::Better(chain_tip) => {
+ debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash);
+ debug_assert!(chain_tip.chainwork > self.chain_tip.chainwork);
+ self.update_chain_tip(chain_tip).await
+ },
+ ChainTip::Worse(chain_tip) => {
+ debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash);
+ debug_assert!(chain_tip.chainwork <= self.chain_tip.chainwork);
+ false
+ },
+ };
+ Ok((chain_tip, blocks_connected))
+ }
+
+ /// Updates the chain tip, syncing the chain listener with any connected or disconnected
+ /// blocks. Returns whether there were any such blocks.
+ async fn update_chain_tip(&mut self, best_chain_tip: ValidatedBlockHeader) -> bool {
+ match self.chain_notifier.synchronize_listener(
+ best_chain_tip, &self.chain_tip, &mut self.chain_poller).await
+ {
+ Ok(_) => {
+ self.chain_tip = best_chain_tip;
+ true
+ },
+ Err((_, Some(chain_tip))) if chain_tip.block_hash != self.chain_tip.block_hash => {
+ self.chain_tip = chain_tip;
+ true
+ },
+ Err(_) => false,
+ }
+ }
+}
+
/// Notifies [listeners] of blocks that have been connected or disconnected from the chain.
///
-/// [listeners]: trait.ChainListener.html
-struct ChainNotifier<C: Cache> {
+/// [listeners]: ../../lightning/chain/trait.Listen.html
+pub struct ChainNotifier<'a, C: Cache, L: Deref> where L::Target: chain::Listen {
/// Cache for looking up headers before fetching from a block source.
- header_cache: C,
+ header_cache: &'a mut C,
+
+ /// Listener that will be notified of connected or disconnected blocks.
+ chain_listener: L,
}
/// Changes made to the chain between subsequent polls that transformed it from having one chain tip
/// Blocks are given in height-descending order. Therefore, blocks are first disconnected in order
/// before new blocks are connected in reverse order.
struct ChainDifference {
+ /// The most recent ancestor common between the chain tips.
+ ///
+ /// If there are any disconnected blocks, this is where the chain forked.
+ common_ancestor: ValidatedBlockHeader,
+
/// Blocks that were disconnected from the chain since the last poll.
disconnected_blocks: Vec<ValidatedBlockHeader>,
connected_blocks: Vec<ValidatedBlockHeader>,
}
-impl<C: Cache> ChainNotifier<C> {
- /// Finds the fork point between `new_header` and `old_header`, disconnecting blocks from
- /// `old_header` to get to that point and then connecting blocks until `new_header`.
+impl<'a, C: Cache, L: Deref> ChainNotifier<'a, C, L> where L::Target: chain::Listen {
+ /// Finds the first common ancestor between `new_header` and `old_header`, disconnecting blocks
+ /// from `old_header` to get to that point and then connecting blocks until `new_header`.
///
/// Validates headers along the transition path, but doesn't fetch blocks until the chain is
/// disconnected to the fork point. Thus, this may return an `Err` that includes where the tip
/// ended up which may not be `new_header`. Note that the returned `Err` contains `Some` header
/// if and only if the transition from `old_header` to `new_header` is valid.
- async fn synchronize_listener<L: ChainListener, P: Poll>(
+ async fn synchronize_listener<P: Poll>(
&mut self,
new_header: ValidatedBlockHeader,
old_header: &ValidatedBlockHeader,
chain_poller: &mut P,
- chain_listener: &mut L,
) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
- let mut difference = self.find_difference(new_header, old_header, chain_poller).await
+ let difference = self.find_difference(new_header, old_header, chain_poller).await
.map_err(|e| (e, None))?;
-
- let mut new_tip = *old_header;
- for header in difference.disconnected_blocks.drain(..) {
- if let Some(cached_header) = self.header_cache.block_disconnected(&header.block_hash) {
- assert_eq!(cached_header, header);
- }
- chain_listener.block_disconnected(&header.header, header.height);
- new_tip = header;
- }
-
- for header in difference.connected_blocks.drain(..).rev() {
- let block = chain_poller
- .fetch_block(&header).await
- .or_else(|e| Err((e, Some(new_tip))))?;
- debug_assert_eq!(block.block_hash, header.block_hash);
-
- self.header_cache.block_connected(header.block_hash, header);
- chain_listener.block_connected(&block, header.height);
- new_tip = header;
- }
-
- Ok(())
+ self.disconnect_blocks(difference.disconnected_blocks);
+ self.connect_blocks(
+ difference.common_ancestor,
+ difference.connected_blocks,
+ chain_poller,
+ ).await
}
/// Returns the changes needed to produce the chain with `current_header` as its tip from the
}
}
- Ok(ChainDifference { disconnected_blocks, connected_blocks })
+ let common_ancestor = current;
+ Ok(ChainDifference { common_ancestor, disconnected_blocks, connected_blocks })
}
/// Returns the previous header for the given header, either by looking it up in the cache or
None => chain_poller.look_up_previous_header(header).await,
}
}
+
+ /// Notifies the chain listeners of disconnected blocks.
+ fn disconnect_blocks(&mut self, mut disconnected_blocks: Vec<ValidatedBlockHeader>) {
+ for header in disconnected_blocks.drain(..) {
+ if let Some(cached_header) = self.header_cache.block_disconnected(&header.block_hash) {
+ assert_eq!(cached_header, header);
+ }
+ self.chain_listener.block_disconnected(&header.header, header.height);
+ }
+ }
+
+ /// Notifies the chain listeners of connected blocks.
+ async fn connect_blocks<P: Poll>(
+ &mut self,
+ mut new_tip: ValidatedBlockHeader,
+ mut connected_blocks: Vec<ValidatedBlockHeader>,
+ chain_poller: &mut P,
+ ) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
+ for header in connected_blocks.drain(..).rev() {
+ let block = chain_poller
+ .fetch_block(&header).await
+ .or_else(|e| Err((e, Some(new_tip))))?;
+ debug_assert_eq!(block.block_hash, header.block_hash);
+
+ self.header_cache.block_connected(header.block_hash, header);
+ self.chain_listener.block_connected(&block, header.height);
+ new_tip = header;
+ }
+
+ Ok(())
+ }
+}
+
+#[cfg(test)]
+mod spv_client_tests {
+ use crate::test_utils::{Blockchain, NullChainListener};
+ use super::*;
+
+ use bitcoin::network::constants::Network;
+
+ #[tokio::test]
+ async fn poll_from_chain_without_headers() {
+ let mut chain = Blockchain::default().with_height(3).without_headers();
+ let best_tip = chain.at_height(1);
+
+ let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ let mut cache = UnboundedCache::new();
+ let mut listener = NullChainListener {};
+ let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener);
+ match client.poll_best_tip().await {
+ Err(e) => {
+ assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
+ assert_eq!(e.into_inner().as_ref().to_string(), "header not found");
+ },
+ Ok(_) => panic!("Expected error"),
+ }
+ assert_eq!(client.chain_tip, best_tip);
+ }
+
+ #[tokio::test]
+ async fn poll_from_chain_with_common_tip() {
+ let mut chain = Blockchain::default().with_height(3);
+ let common_tip = chain.tip();
+
+ let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ let mut cache = UnboundedCache::new();
+ let mut listener = NullChainListener {};
+ let mut client = SpvClient::new(common_tip, poller, &mut cache, &mut listener);
+ match client.poll_best_tip().await {
+ Err(e) => panic!("Unexpected error: {:?}", e),
+ Ok((chain_tip, blocks_connected)) => {
+ assert_eq!(chain_tip, ChainTip::Common);
+ assert!(!blocks_connected);
+ },
+ }
+ assert_eq!(client.chain_tip, common_tip);
+ }
+
+ #[tokio::test]
+ async fn poll_from_chain_with_better_tip() {
+ let mut chain = Blockchain::default().with_height(3);
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+
+ let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ let mut cache = UnboundedCache::new();
+ let mut listener = NullChainListener {};
+ let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
+ match client.poll_best_tip().await {
+ Err(e) => panic!("Unexpected error: {:?}", e),
+ Ok((chain_tip, blocks_connected)) => {
+ assert_eq!(chain_tip, ChainTip::Better(new_tip));
+ assert!(blocks_connected);
+ },
+ }
+ assert_eq!(client.chain_tip, new_tip);
+ }
+
+ #[tokio::test]
+ async fn poll_from_chain_with_better_tip_and_without_any_new_blocks() {
+ let mut chain = Blockchain::default().with_height(3).without_blocks(2..);
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+
+ let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ let mut cache = UnboundedCache::new();
+ let mut listener = NullChainListener {};
+ let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
+ match client.poll_best_tip().await {
+ Err(e) => panic!("Unexpected error: {:?}", e),
+ Ok((chain_tip, blocks_connected)) => {
+ assert_eq!(chain_tip, ChainTip::Better(new_tip));
+ assert!(!blocks_connected);
+ },
+ }
+ assert_eq!(client.chain_tip, old_tip);
+ }
+
+ #[tokio::test]
+ async fn poll_from_chain_with_better_tip_and_without_some_new_blocks() {
+ let mut chain = Blockchain::default().with_height(3).without_blocks(3..);
+ let new_tip = chain.tip();
+ let old_tip = chain.at_height(1);
+
+ let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ let mut cache = UnboundedCache::new();
+ let mut listener = NullChainListener {};
+ let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
+ match client.poll_best_tip().await {
+ Err(e) => panic!("Unexpected error: {:?}", e),
+ Ok((chain_tip, blocks_connected)) => {
+ assert_eq!(chain_tip, ChainTip::Better(new_tip));
+ assert!(blocks_connected);
+ },
+ }
+ assert_eq!(client.chain_tip, chain.at_height(2));
+ }
+
+ #[tokio::test]
+ async fn poll_from_chain_with_worse_tip() {
+ let mut chain = Blockchain::default().with_height(3);
+ let best_tip = chain.tip();
+ chain.disconnect_tip();
+ let worse_tip = chain.tip();
+
+ let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
+ let mut cache = UnboundedCache::new();
+ let mut listener = NullChainListener {};
+ let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener);
+ match client.poll_best_tip().await {
+ Err(e) => panic!("Unexpected error: {:?}", e),
+ Ok((chain_tip, blocks_connected)) => {
+ assert_eq!(chain_tip, ChainTip::Worse(worse_tip));
+ assert!(!blocks_connected);
+ },
+ }
+ assert_eq!(client.chain_tip, best_tip);
+ }
}
#[cfg(test)]
let new_tip = chain.tip();
let old_tip = chain.at_height(1);
- let mut listener = MockChainListener::new()
+ let chain_listener = &MockChainListener::new()
.expect_block_connected(*chain.at_height(2))
.expect_block_connected(*new_tip);
- let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=1) };
+ 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, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((e, _)) => panic!("Unexpected error: {:?}", e),
Ok(_) => {},
}
let new_tip = test_chain.tip();
let old_tip = main_chain.tip();
- let mut listener = MockChainListener::new();
- let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=1) };
+ let chain_listener = &MockChainListener::new();
+ let mut notifier = ChainNotifier {
+ header_cache: &mut main_chain.header_cache(0..=1),
+ chain_listener,
+ };
let mut poller = poll::ChainPoller::new(&mut test_chain, Network::Testnet);
- match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((e, _)) => {
assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
assert_eq!(e.into_inner().as_ref().to_string(), "genesis block reached");
let new_tip = fork_chain.tip();
let old_tip = main_chain.tip();
- let mut listener = MockChainListener::new()
+ let chain_listener = &MockChainListener::new()
.expect_block_disconnected(*old_tip)
.expect_block_connected(*new_tip);
- let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=2) };
+ let mut notifier = ChainNotifier {
+ header_cache: &mut main_chain.header_cache(0..=2),
+ chain_listener,
+ };
let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
- match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((e, _)) => panic!("Unexpected error: {:?}", e),
Ok(_) => {},
}
let new_tip = fork_chain.tip();
let old_tip = main_chain.tip();
- let mut listener = MockChainListener::new()
+ let chain_listener = &MockChainListener::new()
.expect_block_disconnected(*old_tip)
.expect_block_disconnected(*main_chain.at_height(2))
.expect_block_connected(*new_tip);
- let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=3) };
+ let mut notifier = ChainNotifier {
+ header_cache: &mut main_chain.header_cache(0..=3),
+ chain_listener,
+ };
let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
- match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((e, _)) => panic!("Unexpected error: {:?}", e),
Ok(_) => {},
}
let new_tip = fork_chain.tip();
let old_tip = main_chain.tip();
- let mut listener = MockChainListener::new()
+ let chain_listener = &MockChainListener::new()
.expect_block_disconnected(*old_tip)
.expect_block_connected(*fork_chain.at_height(2))
.expect_block_connected(*new_tip);
- let mut notifier = ChainNotifier { header_cache: main_chain.header_cache(0..=2) };
+ let mut notifier = ChainNotifier {
+ header_cache: &mut main_chain.header_cache(0..=2),
+ chain_listener,
+ };
let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
- match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((e, _)) => panic!("Unexpected error: {:?}", e),
Ok(_) => {},
}
let new_tip = chain.tip();
let old_tip = chain.at_height(1);
- let mut listener = MockChainListener::new();
- let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=1) };
+ let chain_listener = &MockChainListener::new();
+ 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, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((_, tip)) => assert_eq!(tip, None),
Ok(_) => panic!("Expected error"),
}
let new_tip = chain.tip();
let old_tip = chain.at_height(1);
- let mut listener = MockChainListener::new();
- let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=3) };
+ let chain_listener = &MockChainListener::new();
+ let mut notifier = ChainNotifier {
+ header_cache: &mut chain.header_cache(0..=3),
+ chain_listener,
+ };
let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
- match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((_, tip)) => assert_eq!(tip, Some(old_tip)),
Ok(_) => panic!("Expected error"),
}
let new_tip = chain.tip();
let old_tip = chain.at_height(1);
- let mut listener = MockChainListener::new()
+ let chain_listener = &MockChainListener::new()
.expect_block_connected(*chain.at_height(2));
- let mut notifier = ChainNotifier { header_cache: chain.header_cache(0..=3) };
+ let mut notifier = ChainNotifier {
+ header_cache: &mut chain.header_cache(0..=3),
+ chain_listener,
+ };
let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
- match notifier.synchronize_listener(new_tip, &old_tip, &mut poller, &mut listener).await {
+ match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
Err((_, tip)) => assert_eq!(tip, Some(chain.at_height(2))),
Ok(_) => panic!("Expected error"),
}
projects / rust-lightning / blobdiff