_ Git - rust-lightning/blob - lightning-block-sync/src/lib.rs

   1 //! A lightweight client for keeping in sync with chain activity.
   2 //!
   3 //! Defines an [`SpvClient`] utility for polling one or more block sources for the best chain tip.
   4 //! It is used to notify listeners of blocks connected or disconnected since the last poll. Useful
   5 //! for keeping a Lightning node in sync with the chain.
   6 //!
   7 //! Defines a [`BlockSource`] trait, which is an asynchronous interface for retrieving block headers
   8 //! and data.
   9 //!
  10 //! Enabling feature `rest-client` or `rpc-client` allows configuring the client to fetch blocks
  11 //! using Bitcoin Core's REST or RPC interface, respectively.
  12 //!
  13 //! Both features support either blocking I/O using `std::net::TcpStream` or, with feature `tokio`,
  14 //! non-blocking I/O using `tokio::net::TcpStream` from inside a Tokio runtime.
  15
  16 // Prefix these with `rustdoc::` when we update our MSRV to be >= 1.52 to remove warnings.
  17 #![deny(broken_intra_doc_links)]
  18 #![deny(private_intra_doc_links)]
  19
  20 #![deny(missing_docs)]
  21 #![deny(unsafe_code)]
  22
  23 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
  24
  25 #[cfg(any(feature = "rest-client", feature = "rpc-client"))]
  26 pub mod http;
  27
  28 pub mod init;
  29 pub mod poll;
  30
  31 pub mod gossip;
  32
  33 #[cfg(feature = "rest-client")]
  34 pub mod rest;
  35
  36 #[cfg(feature = "rpc-client")]
  37 pub mod rpc;
  38
  39 #[cfg(any(feature = "rest-client", feature = "rpc-client"))]
  40 mod convert;
  41
  42 #[cfg(test)]
  43 mod test_utils;
  44
  45 #[cfg(any(feature = "rest-client", feature = "rpc-client"))]
  46 mod utils;
  47
  48 use crate::poll::{ChainTip, Poll, ValidatedBlockHeader};
  49
  50 use bitcoin::blockdata::block::{Block, Header};
  51 use bitcoin::hash_types::BlockHash;
  52 use bitcoin::pow::Work;
  53
  54 use lightning::chain;
  55 use lightning::chain::Listen;
  56
  57 use std::future::Future;
  58 use std::ops::Deref;
  59 use std::pin::Pin;
  60
  61 /// Abstract type for retrieving block headers and data.
  62 pub trait BlockSource : Sync + Send {
  63         /// Returns the header for a given hash. A height hint may be provided in case a block source
  64         /// cannot easily find headers based on a hash. This is merely a hint and thus the returned
  65         /// header must have the same hash as was requested. Otherwise, an error must be returned.
  66         ///
  67         /// Implementations that cannot find headers based on the hash should return a `Transient` error
  68         /// when `height_hint` is `None`.
  69         fn get_header<'a>(&'a self, header_hash: &'a BlockHash, height_hint: Option<u32>) -> AsyncBlockSourceResult<'a, BlockHeaderData>;
  70
  71         /// Returns the block for a given hash. A headers-only block source should return a `Transient`
  72         /// error.
  73         fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, BlockData>;
  74
  75         /// Returns the hash of the best block and, optionally, its height.
  76         ///
  77         /// When polling a block source, [`Poll`] implementations may pass the height to [`get_header`]
  78         /// to allow for a more efficient lookup.
  79         ///
  80         /// [`get_header`]: Self::get_header
  81         fn get_best_block<'a>(&'a self) -> AsyncBlockSourceResult<(BlockHash, Option<u32>)>;
  82 }
  83
  84 /// Result type for `BlockSource` requests.
  85 pub type BlockSourceResult<T> = Result<T, BlockSourceError>;
  86
  87 // TODO: Replace with BlockSourceResult once `async` trait functions are supported. For details,
  88 // see: https://areweasyncyet.rs.
  89 /// Result type for asynchronous `BlockSource` requests.
  90 pub type AsyncBlockSourceResult<'a, T> = Pin<Box<dyn Future<Output = BlockSourceResult<T>> + 'a + Send>>;
  91
  92 /// Error type for `BlockSource` requests.
  93 ///
  94 /// Transient errors may be resolved when re-polling, but no attempt will be made to re-poll on
  95 /// persistent errors.
  96 #[derive(Debug)]
  97 pub struct BlockSourceError {
  98         kind: BlockSourceErrorKind,
  99         error: Box<dyn std::error::Error + Send + Sync>,
 100 }
 101
 102 /// The kind of `BlockSourceError`, either persistent or transient.
 103 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 104 pub enum BlockSourceErrorKind {
 105         /// Indicates an error that won't resolve when retrying a request (e.g., invalid data).
 106         Persistent,
 107
 108         /// Indicates an error that may resolve when retrying a request (e.g., unresponsive).
 109         Transient,
 110 }
 111
 112 impl BlockSourceError {
 113         /// Creates a new persistent error originated from the given error.
 114         pub fn persistent<E>(error: E) -> Self
 115         where E: Into<Box<dyn std::error::Error + Send + Sync>> {
 116                 Self {
 117                         kind: BlockSourceErrorKind::Persistent,
 118                         error: error.into(),
 119                 }
 120         }
 121
 122         /// Creates a new transient error originated from the given error.
 123         pub fn transient<E>(error: E) -> Self
 124         where E: Into<Box<dyn std::error::Error + Send + Sync>> {
 125                 Self {
 126                         kind: BlockSourceErrorKind::Transient,
 127                         error: error.into(),
 128                 }
 129         }
 130
 131         /// Returns the kind of error.
 132         pub fn kind(&self) -> BlockSourceErrorKind {
 133                 self.kind
 134         }
 135
 136         /// Converts the error into the underlying error.
 137         ///
 138         /// May contain an [`std::io::Error`] from the [`BlockSource`]. See implementations for further
 139         /// details, if any.
 140         pub fn into_inner(self) -> Box<dyn std::error::Error + Send + Sync> {
 141                 self.error
 142         }
 143 }
 144
 145 /// A block header and some associated data. This information should be available from most block
 146 /// sources (and, notably, is available in Bitcoin Core's RPC and REST interfaces).
 147 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 148 pub struct BlockHeaderData {
 149         /// The block header itself.
 150         pub header: Header,
 151
 152         /// The block height where the genesis block has height 0.
 153         pub height: u32,
 154
 155         /// The total chain work required to build a chain of equivalent weight.
 156         pub chainwork: Work,
 157 }
 158
 159 /// A block including either all its transactions or only the block header.
 160 ///
 161 /// [`BlockSource`] may be implemented to either always return full blocks or, in the case of
 162 /// compact block filters (BIP 157/158), return header-only blocks when no pertinent transactions
 163 /// match. See [`chain::Filter`] for details on how to notify a source of such transactions.
 164 pub enum BlockData {
 165         /// A block containing all its transactions.
 166         FullBlock(Block),
 167         /// A block header for when the block does not contain any pertinent transactions.
 168         HeaderOnly(Header),
 169 }
 170
 171 /// A lightweight client for keeping a listener in sync with the chain, allowing for Simplified
 172 /// Payment Verification (SPV).
 173 ///
 174 /// The client is parameterized by a chain poller which is responsible for polling one or more block
 175 /// sources for the best chain tip. During this process it detects any chain forks, determines which
 176 /// constitutes the best chain, and updates the listener accordingly with any blocks that were
 177 /// connected or disconnected since the last poll.
 178 ///
 179 /// Block headers for the best chain are maintained in the parameterized cache, allowing for a
 180 /// custom cache eviction policy. This offers flexibility to those sensitive to resource usage.
 181 /// Hence, there is a trade-off between a lower memory footprint and potentially increased network
 182 /// I/O as headers are re-fetched during fork detection.
 183 pub struct SpvClient<'a, P: Poll, C: Cache, L: Deref>
 184 where L::Target: chain::Listen {
 185         chain_tip: ValidatedBlockHeader,
 186         chain_poller: P,
 187         chain_notifier: ChainNotifier<'a, C, L>,
 188 }
 189
 190 /// The `Cache` trait defines behavior for managing a block header cache, where block headers are
 191 /// keyed by block hash.
 192 ///
 193 /// Used by [`ChainNotifier`] to store headers along the best chain, which is important for ensuring
 194 /// that blocks can be disconnected if they are no longer accessible from a block source (e.g., if
 195 /// the block source does not store stale forks indefinitely).
 196 ///
 197 /// Implementations may define how long to retain headers such that it's unlikely they will ever be
 198 /// needed to disconnect a block.  In cases where block sources provide access to headers on stale
 199 /// forks reliably, caches may be entirely unnecessary.
 200 pub trait Cache {
 201         /// Retrieves the block header keyed by the given block hash.
 202         fn look_up(&self, block_hash: &BlockHash) -> Option<&ValidatedBlockHeader>;
 203
 204         /// Called when a block has been connected to the best chain to ensure it is available to be
 205         /// disconnected later if needed.
 206         fn block_connected(&mut self, block_hash: BlockHash, block_header: ValidatedBlockHeader);
 207
 208         /// Called when a block has been disconnected from the best chain. Once disconnected, a block's
 209         /// header is no longer needed and thus can be removed.
 210         fn block_disconnected(&mut self, block_hash: &BlockHash) -> Option<ValidatedBlockHeader>;
 211 }
 212
 213 /// Unbounded cache of block headers keyed by block hash.
 214 pub type UnboundedCache = std::collections::HashMap<BlockHash, ValidatedBlockHeader>;
 215
 216 impl Cache for UnboundedCache {
 217         fn look_up(&self, block_hash: &BlockHash) -> Option<&ValidatedBlockHeader> {
 218                 self.get(block_hash)
 219         }
 220
 221         fn block_connected(&mut self, block_hash: BlockHash, block_header: ValidatedBlockHeader) {
 222                 self.insert(block_hash, block_header);
 223         }
 224
 225         fn block_disconnected(&mut self, block_hash: &BlockHash) -> Option<ValidatedBlockHeader> {
 226                 self.remove(block_hash)
 227         }
 228 }
 229
 230 impl<'a, P: Poll, C: Cache, L: Deref> SpvClient<'a, P, C, L> where L::Target: chain::Listen {
 231         /// Creates a new SPV client using `chain_tip` as the best known chain tip.
 232         ///
 233         /// Subsequent calls to [`poll_best_tip`] will poll for the best chain tip using the given chain
 234         /// poller, which may be configured with one or more block sources to query. At least one block
 235         /// source must provide headers back from the best chain tip to its common ancestor with
 236         /// `chain_tip`.
 237         /// * `header_cache` is used to look up and store headers on the best chain
 238         /// * `chain_listener` is notified of any blocks connected or disconnected
 239         ///
 240         /// [`poll_best_tip`]: SpvClient::poll_best_tip
 241         pub fn new(
 242                 chain_tip: ValidatedBlockHeader,
 243                 chain_poller: P,
 244                 header_cache: &'a mut C,
 245                 chain_listener: L,
 246         ) -> Self {
 247                 let chain_notifier = ChainNotifier { header_cache, chain_listener };
 248                 Self { chain_tip, chain_poller, chain_notifier }
 249         }
 250
 251         /// Polls for the best tip and updates the chain listener with any connected or disconnected
 252         /// blocks accordingly.
 253         ///
 254         /// Returns the best polled chain tip relative to the previous best known tip and whether any
 255         /// blocks were indeed connected or disconnected.
 256         pub async fn poll_best_tip(&mut self) -> BlockSourceResult<(ChainTip, bool)> {
 257                 let chain_tip = self.chain_poller.poll_chain_tip(self.chain_tip).await?;
 258                 let blocks_connected = match chain_tip {
 259                         ChainTip::Common => false,
 260                         ChainTip::Better(chain_tip) => {
 261                                 debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash);
 262                                 debug_assert!(chain_tip.chainwork > self.chain_tip.chainwork);
 263                                 self.update_chain_tip(chain_tip).await
 264                         },
 265                         ChainTip::Worse(chain_tip) => {
 266                                 debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash);
 267                                 debug_assert!(chain_tip.chainwork <= self.chain_tip.chainwork);
 268                                 false
 269                         },
 270                 };
 271                 Ok((chain_tip, blocks_connected))
 272         }
 273
 274         /// Updates the chain tip, syncing the chain listener with any connected or disconnected
 275         /// blocks. Returns whether there were any such blocks.
 276         async fn update_chain_tip(&mut self, best_chain_tip: ValidatedBlockHeader) -> bool {
 277                 match self.chain_notifier.synchronize_listener(
 278                         best_chain_tip, &self.chain_tip, &mut self.chain_poller).await
 279                 {
 280                         Ok(_) => {
 281                                 self.chain_tip = best_chain_tip;
 282                                 true
 283                         },
 284                         Err((_, Some(chain_tip))) if chain_tip.block_hash != self.chain_tip.block_hash => {
 285                                 self.chain_tip = chain_tip;
 286                                 true
 287                         },
 288                         Err(_) => false,
 289                 }
 290         }
 291 }
 292
 293 /// Notifies [listeners] of blocks that have been connected or disconnected from the chain.
 294 ///
 295 /// [listeners]: lightning::chain::Listen
 296 pub struct ChainNotifier<'a, C: Cache, L: Deref> where L::Target: chain::Listen {
 297         /// Cache for looking up headers before fetching from a block source.
 298         header_cache: &'a mut C,
 299
 300         /// Listener that will be notified of connected or disconnected blocks.
 301         chain_listener: L,
 302 }
 303
 304 /// Changes made to the chain between subsequent polls that transformed it from having one chain tip
 305 /// to another.
 306 ///
 307 /// Blocks are given in height-descending order. Therefore, blocks are first disconnected in order
 308 /// before new blocks are connected in reverse order.
 309 struct ChainDifference {
 310         /// The most recent ancestor common between the chain tips.
 311         ///
 312         /// If there are any disconnected blocks, this is where the chain forked.
 313         common_ancestor: ValidatedBlockHeader,
 314
 315         /// Blocks that were disconnected from the chain since the last poll.
 316         disconnected_blocks: Vec<ValidatedBlockHeader>,
 317
 318         /// Blocks that were connected to the chain since the last poll.
 319         connected_blocks: Vec<ValidatedBlockHeader>,
 320 }
 321
 322 impl<'a, C: Cache, L: Deref> ChainNotifier<'a, C, L> where L::Target: chain::Listen {
 323         /// Finds the first common ancestor between `new_header` and `old_header`, disconnecting blocks
 324         /// from `old_header` to get to that point and then connecting blocks until `new_header`.
 325         ///
 326         /// Validates headers along the transition path, but doesn't fetch blocks until the chain is
 327         /// disconnected to the fork point. Thus, this may return an `Err` that includes where the tip
 328         /// ended up which may not be `new_header`. Note that the returned `Err` contains `Some` header
 329         /// if and only if the transition from `old_header` to `new_header` is valid.
 330         async fn synchronize_listener<P: Poll>(
 331                 &mut self,
 332                 new_header: ValidatedBlockHeader,
 333                 old_header: &ValidatedBlockHeader,
 334                 chain_poller: &mut P,
 335         ) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
 336                 let difference = self.find_difference(new_header, old_header, chain_poller).await
 337                         .map_err(|e| (e, None))?;
 338                 self.disconnect_blocks(difference.disconnected_blocks);
 339                 self.connect_blocks(
 340                         difference.common_ancestor,
 341                         difference.connected_blocks,
 342                         chain_poller,
 343                 ).await
 344         }
 345
 346         /// Returns the changes needed to produce the chain with `current_header` as its tip from the
 347         /// chain with `prev_header` as its tip.
 348         ///
 349         /// Walks backwards from `current_header` and `prev_header`, finding the common ancestor.
 350         async fn find_difference<P: Poll>(
 351                 &self,
 352                 current_header: ValidatedBlockHeader,
 353                 prev_header: &ValidatedBlockHeader,
 354                 chain_poller: &mut P,
 355         ) -> BlockSourceResult<ChainDifference> {
 356                 let mut disconnected_blocks = Vec::new();
 357                 let mut connected_blocks = Vec::new();
 358                 let mut current = current_header;
 359                 let mut previous = *prev_header;
 360                 loop {
 361                         // Found the common ancestor.
 362                         if current.block_hash == previous.block_hash {
 363                                 break;
 364                         }
 365
 366                         // Walk back the chain, finding blocks needed to connect and disconnect. Only walk back
 367                         // the header with the greater height, or both if equal heights.
 368                         let current_height = current.height;
 369                         let previous_height = previous.height;
 370                         if current_height <= previous_height {
 371                                 disconnected_blocks.push(previous);
 372                                 previous = self.look_up_previous_header(chain_poller, &previous).await?;
 373                         }
 374                         if current_height >= previous_height {
 375                                 connected_blocks.push(current);
 376                                 current = self.look_up_previous_header(chain_poller, &current).await?;
 377                         }
 378                 }
 379
 380                 let common_ancestor = current;
 381                 Ok(ChainDifference { common_ancestor, disconnected_blocks, connected_blocks })
 382         }
 383
 384         /// Returns the previous header for the given header, either by looking it up in the cache or
 385         /// fetching it if not found.
 386         async fn look_up_previous_header<P: Poll>(
 387                 &self,
 388                 chain_poller: &mut P,
 389                 header: &ValidatedBlockHeader,
 390         ) -> BlockSourceResult<ValidatedBlockHeader> {
 391                 match self.header_cache.look_up(&header.header.prev_blockhash) {
 392                         Some(prev_header) => Ok(*prev_header),
 393                         None => chain_poller.look_up_previous_header(header).await,
 394                 }
 395         }
 396
 397         /// Notifies the chain listeners of disconnected blocks.
 398         fn disconnect_blocks(&mut self, mut disconnected_blocks: Vec<ValidatedBlockHeader>) {
 399                 for header in disconnected_blocks.drain(..) {
 400                         if let Some(cached_header) = self.header_cache.block_disconnected(&header.block_hash) {
 401                                 assert_eq!(cached_header, header);
 402                         }
 403                         self.chain_listener.block_disconnected(&header.header, header.height);
 404                 }
 405         }
 406
 407         /// Notifies the chain listeners of connected blocks.
 408         async fn connect_blocks<P: Poll>(
 409                 &mut self,
 410                 mut new_tip: ValidatedBlockHeader,
 411                 mut connected_blocks: Vec<ValidatedBlockHeader>,
 412                 chain_poller: &mut P,
 413         ) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
 414                 for header in connected_blocks.drain(..).rev() {
 415                         let height = header.height;
 416                         let block_data = chain_poller
 417                                 .fetch_block(&header).await
 418                                 .map_err(|e| (e, Some(new_tip)))?;
 419                         debug_assert_eq!(block_data.block_hash, header.block_hash);
 420
 421                         match block_data.deref() {
 422                                 BlockData::FullBlock(block) => {
 423                                         self.chain_listener.block_connected(block, height);
 424                                 },
 425                                 BlockData::HeaderOnly(header) => {
 426                                         self.chain_listener.filtered_block_connected(header, &[], height);
 427                                 },
 428                         }
 429
 430                         self.header_cache.block_connected(header.block_hash, header);
 431                         new_tip = header;
 432                 }
 433
 434                 Ok(())
 435         }
 436 }
 437
 438 #[cfg(test)]
 439 mod spv_client_tests {
 440         use crate::test_utils::{Blockchain, NullChainListener};
 441         use super::*;
 442
 443         use bitcoin::network::constants::Network;
 444
 445         #[tokio::test]
 446         async fn poll_from_chain_without_headers() {
 447                 let mut chain = Blockchain::default().with_height(3).without_headers();
 448                 let best_tip = chain.at_height(1);
 449
 450                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 451                 let mut cache = UnboundedCache::new();
 452                 let mut listener = NullChainListener {};
 453                 let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener);
 454                 match client.poll_best_tip().await {
 455                         Err(e) => {
 456                                 assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
 457                                 assert_eq!(e.into_inner().as_ref().to_string(), "header not found");
 458                         },
 459                         Ok(_) => panic!("Expected error"),
 460                 }
 461                 assert_eq!(client.chain_tip, best_tip);
 462         }
 463
 464         #[tokio::test]
 465         async fn poll_from_chain_with_common_tip() {
 466                 let mut chain = Blockchain::default().with_height(3);
 467                 let common_tip = chain.tip();
 468
 469                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 470                 let mut cache = UnboundedCache::new();
 471                 let mut listener = NullChainListener {};
 472                 let mut client = SpvClient::new(common_tip, poller, &mut cache, &mut listener);
 473                 match client.poll_best_tip().await {
 474                         Err(e) => panic!("Unexpected error: {:?}", e),
 475                         Ok((chain_tip, blocks_connected)) => {
 476                                 assert_eq!(chain_tip, ChainTip::Common);
 477                                 assert!(!blocks_connected);
 478                         },
 479                 }
 480                 assert_eq!(client.chain_tip, common_tip);
 481         }
 482
 483         #[tokio::test]
 484         async fn poll_from_chain_with_better_tip() {
 485                 let mut chain = Blockchain::default().with_height(3);
 486                 let new_tip = chain.tip();
 487                 let old_tip = chain.at_height(1);
 488
 489                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 490                 let mut cache = UnboundedCache::new();
 491                 let mut listener = NullChainListener {};
 492                 let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
 493                 match client.poll_best_tip().await {
 494                         Err(e) => panic!("Unexpected error: {:?}", e),
 495                         Ok((chain_tip, blocks_connected)) => {
 496                                 assert_eq!(chain_tip, ChainTip::Better(new_tip));
 497                                 assert!(blocks_connected);
 498                         },
 499                 }
 500                 assert_eq!(client.chain_tip, new_tip);
 501         }
 502
 503         #[tokio::test]
 504         async fn poll_from_chain_with_better_tip_and_without_any_new_blocks() {
 505                 let mut chain = Blockchain::default().with_height(3).without_blocks(2..);
 506                 let new_tip = chain.tip();
 507                 let old_tip = chain.at_height(1);
 508
 509                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 510                 let mut cache = UnboundedCache::new();
 511                 let mut listener = NullChainListener {};
 512                 let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
 513                 match client.poll_best_tip().await {
 514                         Err(e) => panic!("Unexpected error: {:?}", e),
 515                         Ok((chain_tip, blocks_connected)) => {
 516                                 assert_eq!(chain_tip, ChainTip::Better(new_tip));
 517                                 assert!(!blocks_connected);
 518                         },
 519                 }
 520                 assert_eq!(client.chain_tip, old_tip);
 521         }
 522
 523         #[tokio::test]
 524         async fn poll_from_chain_with_better_tip_and_without_some_new_blocks() {
 525                 let mut chain = Blockchain::default().with_height(3).without_blocks(3..);
 526                 let new_tip = chain.tip();
 527                 let old_tip = chain.at_height(1);
 528
 529                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 530                 let mut cache = UnboundedCache::new();
 531                 let mut listener = NullChainListener {};
 532                 let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
 533                 match client.poll_best_tip().await {
 534                         Err(e) => panic!("Unexpected error: {:?}", e),
 535                         Ok((chain_tip, blocks_connected)) => {
 536                                 assert_eq!(chain_tip, ChainTip::Better(new_tip));
 537                                 assert!(blocks_connected);
 538                         },
 539                 }
 540                 assert_eq!(client.chain_tip, chain.at_height(2));
 541         }
 542
 543         #[tokio::test]
 544         async fn poll_from_chain_with_worse_tip() {
 545                 let mut chain = Blockchain::default().with_height(3);
 546                 let best_tip = chain.tip();
 547                 chain.disconnect_tip();
 548                 let worse_tip = chain.tip();
 549
 550                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 551                 let mut cache = UnboundedCache::new();
 552                 let mut listener = NullChainListener {};
 553                 let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener);
 554                 match client.poll_best_tip().await {
 555                         Err(e) => panic!("Unexpected error: {:?}", e),
 556                         Ok((chain_tip, blocks_connected)) => {
 557                                 assert_eq!(chain_tip, ChainTip::Worse(worse_tip));
 558                                 assert!(!blocks_connected);
 559                         },
 560                 }
 561                 assert_eq!(client.chain_tip, best_tip);
 562         }
 563 }
 564
 565 #[cfg(test)]
 566 mod chain_notifier_tests {
 567         use crate::test_utils::{Blockchain, MockChainListener};
 568         use super::*;
 569
 570         use bitcoin::network::constants::Network;
 571
 572         #[tokio::test]
 573         async fn sync_from_same_chain() {
 574                 let mut chain = Blockchain::default().with_height(3);
 575
 576                 let new_tip = chain.tip();
 577                 let old_tip = chain.at_height(1);
 578                 let chain_listener = &MockChainListener::new()
 579                         .expect_block_connected(*chain.at_height(2))
 580                         .expect_block_connected(*new_tip);
 581                 let mut notifier = ChainNotifier {
 582                         header_cache: &mut chain.header_cache(0..=1),
 583                         chain_listener,
 584                 };
 585                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 586                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 587                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 588                         Ok(_) => {},
 589                 }
 590         }
 591
 592         #[tokio::test]
 593         async fn sync_from_different_chains() {
 594                 let mut test_chain = Blockchain::with_network(Network::Testnet).with_height(1);
 595                 let main_chain = Blockchain::with_network(Network::Bitcoin).with_height(1);
 596
 597                 let new_tip = test_chain.tip();
 598                 let old_tip = main_chain.tip();
 599                 let chain_listener = &MockChainListener::new();
 600                 let mut notifier = ChainNotifier {
 601                         header_cache: &mut main_chain.header_cache(0..=1),
 602                         chain_listener,
 603                 };
 604                 let mut poller = poll::ChainPoller::new(&mut test_chain, Network::Testnet);
 605                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 606                         Err((e, _)) => {
 607                                 assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
 608                                 assert_eq!(e.into_inner().as_ref().to_string(), "genesis block reached");
 609                         },
 610                         Ok(_) => panic!("Expected error"),
 611                 }
 612         }
 613
 614         #[tokio::test]
 615         async fn sync_from_equal_length_fork() {
 616                 let main_chain = Blockchain::default().with_height(2);
 617                 let mut fork_chain = main_chain.fork_at_height(1);
 618
 619                 let new_tip = fork_chain.tip();
 620                 let old_tip = main_chain.tip();
 621                 let chain_listener = &MockChainListener::new()
 622                         .expect_block_disconnected(*old_tip)
 623                         .expect_block_connected(*new_tip);
 624                 let mut notifier = ChainNotifier {
 625                         header_cache: &mut main_chain.header_cache(0..=2),
 626                         chain_listener,
 627                 };
 628                 let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
 629                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 630                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 631                         Ok(_) => {},
 632                 }
 633         }
 634
 635         #[tokio::test]
 636         async fn sync_from_shorter_fork() {
 637                 let main_chain = Blockchain::default().with_height(3);
 638                 let mut fork_chain = main_chain.fork_at_height(1);
 639                 fork_chain.disconnect_tip();
 640
 641                 let new_tip = fork_chain.tip();
 642                 let old_tip = main_chain.tip();
 643                 let chain_listener = &MockChainListener::new()
 644                         .expect_block_disconnected(*old_tip)
 645                         .expect_block_disconnected(*main_chain.at_height(2))
 646                         .expect_block_connected(*new_tip);
 647                 let mut notifier = ChainNotifier {
 648                         header_cache: &mut main_chain.header_cache(0..=3),
 649                         chain_listener,
 650                 };
 651                 let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
 652                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 653                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 654                         Ok(_) => {},
 655                 }
 656         }
 657
 658         #[tokio::test]
 659         async fn sync_from_longer_fork() {
 660                 let mut main_chain = Blockchain::default().with_height(3);
 661                 let mut fork_chain = main_chain.fork_at_height(1);
 662                 main_chain.disconnect_tip();
 663
 664                 let new_tip = fork_chain.tip();
 665                 let old_tip = main_chain.tip();
 666                 let chain_listener = &MockChainListener::new()
 667                         .expect_block_disconnected(*old_tip)
 668                         .expect_block_connected(*fork_chain.at_height(2))
 669                         .expect_block_connected(*new_tip);
 670                 let mut notifier = ChainNotifier {
 671                         header_cache: &mut main_chain.header_cache(0..=2),
 672                         chain_listener,
 673                 };
 674                 let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
 675                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 676                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 677                         Ok(_) => {},
 678                 }
 679         }
 680
 681         #[tokio::test]
 682         async fn sync_from_chain_without_headers() {
 683                 let mut chain = Blockchain::default().with_height(3).without_headers();
 684
 685                 let new_tip = chain.tip();
 686                 let old_tip = chain.at_height(1);
 687                 let chain_listener = &MockChainListener::new();
 688                 let mut notifier = ChainNotifier {
 689                         header_cache: &mut chain.header_cache(0..=1),
 690                         chain_listener,
 691                 };
 692                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 693                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 694                         Err((_, tip)) => assert_eq!(tip, None),
 695                         Ok(_) => panic!("Expected error"),
 696                 }
 697         }
 698
 699         #[tokio::test]
 700         async fn sync_from_chain_without_any_new_blocks() {
 701                 let mut chain = Blockchain::default().with_height(3).without_blocks(2..);
 702
 703                 let new_tip = chain.tip();
 704                 let old_tip = chain.at_height(1);
 705                 let chain_listener = &MockChainListener::new();
 706                 let mut notifier = ChainNotifier {
 707                         header_cache: &mut chain.header_cache(0..=3),
 708                         chain_listener,
 709                 };
 710                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 711                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 712                         Err((_, tip)) => assert_eq!(tip, Some(old_tip)),
 713                         Ok(_) => panic!("Expected error"),
 714                 }
 715         }
 716
 717         #[tokio::test]
 718         async fn sync_from_chain_without_some_new_blocks() {
 719                 let mut chain = Blockchain::default().with_height(3).without_blocks(3..);
 720
 721                 let new_tip = chain.tip();
 722                 let old_tip = chain.at_height(1);
 723                 let chain_listener = &MockChainListener::new()
 724                         .expect_block_connected(*chain.at_height(2));
 725                 let mut notifier = ChainNotifier {
 726                         header_cache: &mut chain.header_cache(0..=3),
 727                         chain_listener,
 728                 };
 729                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 730                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 731                         Err((_, tip)) => assert_eq!(tip, Some(chain.at_height(2))),
 732                         Ok(_) => panic!("Expected error"),
 733                 }
 734         }
 735
 736         #[tokio::test]
 737         async fn sync_from_chain_with_filtered_blocks() {
 738                 let mut chain = Blockchain::default().with_height(3).filtered_blocks();
 739
 740                 let new_tip = chain.tip();
 741                 let old_tip = chain.at_height(1);
 742                 let chain_listener = &MockChainListener::new()
 743                         .expect_filtered_block_connected(*chain.at_height(2))
 744                         .expect_filtered_block_connected(*new_tip);
 745                 let mut notifier = ChainNotifier {
 746                         header_cache: &mut chain.header_cache(0..=1),
 747                         chain_listener,
 748                 };
 749                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 750                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 751                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 752                         Ok(_) => {},
 753                 }
 754         }
 755
 756 }