_ 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 #[cfg(feature = "rest-client")]
  32 pub mod rest;
  33
  34 #[cfg(feature = "rpc-client")]
  35 pub mod rpc;
  36
  37 #[cfg(any(feature = "rest-client", feature = "rpc-client"))]
  38 mod convert;
  39
  40 #[cfg(test)]
  41 mod test_utils;
  42
  43 #[cfg(any(feature = "rest-client", feature = "rpc-client"))]
  44 mod utils;
  45
  46 use crate::poll::{ChainTip, Poll, ValidatedBlockHeader};
  47
  48 use bitcoin::blockdata::block::{Block, BlockHeader};
  49 use bitcoin::hash_types::BlockHash;
  50 use bitcoin::util::uint::Uint256;
  51
  52 use lightning::chain;
  53 use lightning::chain::Listen;
  54
  55 use std::future::Future;
  56 use std::ops::Deref;
  57 use std::pin::Pin;
  58
  59 /// Abstract type for retrieving block headers and data.
  60 pub trait BlockSource : Sync + Send {
  61         /// Returns the header for a given hash. A height hint may be provided in case a block source
  62         /// cannot easily find headers based on a hash. This is merely a hint and thus the returned
  63         /// header must have the same hash as was requested. Otherwise, an error must be returned.
  64         ///
  65         /// Implementations that cannot find headers based on the hash should return a `Transient` error
  66         /// when `height_hint` is `None`.
  67         fn get_header<'a>(&'a self, header_hash: &'a BlockHash, height_hint: Option<u32>) -> AsyncBlockSourceResult<'a, BlockHeaderData>;
  68
  69         /// Returns the block for a given hash. A headers-only block source should return a `Transient`
  70         /// error.
  71         fn get_block<'a>(&'a self, header_hash: &'a BlockHash) -> AsyncBlockSourceResult<'a, BlockData>;
  72
  73         /// Returns the hash of the best block and, optionally, its height.
  74         ///
  75         /// When polling a block source, [`Poll`] implementations may pass the height to [`get_header`]
  76         /// to allow for a more efficient lookup.
  77         ///
  78         /// [`get_header`]: Self::get_header
  79         fn get_best_block<'a>(&'a self) -> AsyncBlockSourceResult<(BlockHash, Option<u32>)>;
  80 }
  81
  82 /// Result type for `BlockSource` requests.
  83 pub type BlockSourceResult<T> = Result<T, BlockSourceError>;
  84
  85 // TODO: Replace with BlockSourceResult once `async` trait functions are supported. For details,
  86 // see: https://areweasyncyet.rs.
  87 /// Result type for asynchronous `BlockSource` requests.
  88 pub type AsyncBlockSourceResult<'a, T> = Pin<Box<dyn Future<Output = BlockSourceResult<T>> + 'a + Send>>;
  89
  90 /// Error type for `BlockSource` requests.
  91 ///
  92 /// Transient errors may be resolved when re-polling, but no attempt will be made to re-poll on
  93 /// persistent errors.
  94 #[derive(Debug)]
  95 pub struct BlockSourceError {
  96         kind: BlockSourceErrorKind,
  97         error: Box<dyn std::error::Error + Send + Sync>,
  98 }
  99
 100 /// The kind of `BlockSourceError`, either persistent or transient.
 101 #[derive(Clone, Copy, Debug, PartialEq)]
 102 pub enum BlockSourceErrorKind {
 103         /// Indicates an error that won't resolve when retrying a request (e.g., invalid data).
 104         Persistent,
 105
 106         /// Indicates an error that may resolve when retrying a request (e.g., unresponsive).
 107         Transient,
 108 }
 109
 110 impl BlockSourceError {
 111         /// Creates a new persistent error originated from the given error.
 112         pub fn persistent<E>(error: E) -> Self
 113         where E: Into<Box<dyn std::error::Error + Send + Sync>> {
 114                 Self {
 115                         kind: BlockSourceErrorKind::Persistent,
 116                         error: error.into(),
 117                 }
 118         }
 119
 120         /// Creates a new transient error originated from the given error.
 121         pub fn transient<E>(error: E) -> Self
 122         where E: Into<Box<dyn std::error::Error + Send + Sync>> {
 123                 Self {
 124                         kind: BlockSourceErrorKind::Transient,
 125                         error: error.into(),
 126                 }
 127         }
 128
 129         /// Returns the kind of error.
 130         pub fn kind(&self) -> BlockSourceErrorKind {
 131                 self.kind
 132         }
 133
 134         /// Converts the error into the underlying error.
 135         pub fn into_inner(self) -> Box<dyn std::error::Error + Send + Sync> {
 136                 self.error
 137         }
 138 }
 139
 140 /// A block header and some associated data. This information should be available from most block
 141 /// sources (and, notably, is available in Bitcoin Core's RPC and REST interfaces).
 142 #[derive(Clone, Copy, Debug, PartialEq)]
 143 pub struct BlockHeaderData {
 144         /// The block header itself.
 145         pub header: BlockHeader,
 146
 147         /// The block height where the genesis block has height 0.
 148         pub height: u32,
 149
 150         /// The total chain work in expected number of double-SHA256 hashes required to build a chain
 151         /// of equivalent weight.
 152         pub chainwork: Uint256,
 153 }
 154
 155 /// A block including either all its transactions or only the block header.
 156 ///
 157 /// [`BlockSource`] may be implemented to either always return full blocks or, in the case of
 158 /// compact block filters (BIP 157/158), return header-only blocks when no pertinent transactions
 159 /// match. See [`chain::Filter`] for details on how to notify a source of such transactions.
 160 pub enum BlockData {
 161         /// A block containing all its transactions.
 162         FullBlock(Block),
 163         /// A block header for when the block does not contain any pertinent transactions.
 164         HeaderOnly(BlockHeader),
 165 }
 166
 167 /// A lightweight client for keeping a listener in sync with the chain, allowing for Simplified
 168 /// Payment Verification (SPV).
 169 ///
 170 /// The client is parameterized by a chain poller which is responsible for polling one or more block
 171 /// sources for the best chain tip. During this process it detects any chain forks, determines which
 172 /// constitutes the best chain, and updates the listener accordingly with any blocks that were
 173 /// connected or disconnected since the last poll.
 174 ///
 175 /// Block headers for the best chain are maintained in the parameterized cache, allowing for a
 176 /// custom cache eviction policy. This offers flexibility to those sensitive to resource usage.
 177 /// Hence, there is a trade-off between a lower memory footprint and potentially increased network
 178 /// I/O as headers are re-fetched during fork detection.
 179 pub struct SpvClient<'a, P: Poll, C: Cache, L: Deref>
 180 where L::Target: chain::Listen {
 181         chain_tip: ValidatedBlockHeader,
 182         chain_poller: P,
 183         chain_notifier: ChainNotifier<'a, C, L>,
 184 }
 185
 186 /// The `Cache` trait defines behavior for managing a block header cache, where block headers are
 187 /// keyed by block hash.
 188 ///
 189 /// Used by [`ChainNotifier`] to store headers along the best chain, which is important for ensuring
 190 /// that blocks can be disconnected if they are no longer accessible from a block source (e.g., if
 191 /// the block source does not store stale forks indefinitely).
 192 ///
 193 /// Implementations may define how long to retain headers such that it's unlikely they will ever be
 194 /// needed to disconnect a block.  In cases where block sources provide access to headers on stale
 195 /// forks reliably, caches may be entirely unnecessary.
 196 pub trait Cache {
 197         /// Retrieves the block header keyed by the given block hash.
 198         fn look_up(&self, block_hash: &BlockHash) -> Option<&ValidatedBlockHeader>;
 199
 200         /// Called when a block has been connected to the best chain to ensure it is available to be
 201         /// disconnected later if needed.
 202         fn block_connected(&mut self, block_hash: BlockHash, block_header: ValidatedBlockHeader);
 203
 204         /// Called when a block has been disconnected from the best chain. Once disconnected, a block's
 205         /// header is no longer needed and thus can be removed.
 206         fn block_disconnected(&mut self, block_hash: &BlockHash) -> Option<ValidatedBlockHeader>;
 207 }
 208
 209 /// Unbounded cache of block headers keyed by block hash.
 210 pub type UnboundedCache = std::collections::HashMap<BlockHash, ValidatedBlockHeader>;
 211
 212 impl Cache for UnboundedCache {
 213         fn look_up(&self, block_hash: &BlockHash) -> Option<&ValidatedBlockHeader> {
 214                 self.get(block_hash)
 215         }
 216
 217         fn block_connected(&mut self, block_hash: BlockHash, block_header: ValidatedBlockHeader) {
 218                 self.insert(block_hash, block_header);
 219         }
 220
 221         fn block_disconnected(&mut self, block_hash: &BlockHash) -> Option<ValidatedBlockHeader> {
 222                 self.remove(block_hash)
 223         }
 224 }
 225
 226 impl<'a, P: Poll, C: Cache, L: Deref> SpvClient<'a, P, C, L> where L::Target: chain::Listen {
 227         /// Creates a new SPV client using `chain_tip` as the best known chain tip.
 228         ///
 229         /// Subsequent calls to [`poll_best_tip`] will poll for the best chain tip using the given chain
 230         /// poller, which may be configured with one or more block sources to query. At least one block
 231         /// source must provide headers back from the best chain tip to its common ancestor with
 232         /// `chain_tip`.
 233         /// * `header_cache` is used to look up and store headers on the best chain
 234         /// * `chain_listener` is notified of any blocks connected or disconnected
 235         ///
 236         /// [`poll_best_tip`]: SpvClient::poll_best_tip
 237         pub fn new(
 238                 chain_tip: ValidatedBlockHeader,
 239                 chain_poller: P,
 240                 header_cache: &'a mut C,
 241                 chain_listener: L,
 242         ) -> Self {
 243                 let chain_notifier = ChainNotifier { header_cache, chain_listener };
 244                 Self { chain_tip, chain_poller, chain_notifier }
 245         }
 246
 247         /// Polls for the best tip and updates the chain listener with any connected or disconnected
 248         /// blocks accordingly.
 249         ///
 250         /// Returns the best polled chain tip relative to the previous best known tip and whether any
 251         /// blocks were indeed connected or disconnected.
 252         pub async fn poll_best_tip(&mut self) -> BlockSourceResult<(ChainTip, bool)> {
 253                 let chain_tip = self.chain_poller.poll_chain_tip(self.chain_tip).await?;
 254                 let blocks_connected = match chain_tip {
 255                         ChainTip::Common => false,
 256                         ChainTip::Better(chain_tip) => {
 257                                 debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash);
 258                                 debug_assert!(chain_tip.chainwork > self.chain_tip.chainwork);
 259                                 self.update_chain_tip(chain_tip).await
 260                         },
 261                         ChainTip::Worse(chain_tip) => {
 262                                 debug_assert_ne!(chain_tip.block_hash, self.chain_tip.block_hash);
 263                                 debug_assert!(chain_tip.chainwork <= self.chain_tip.chainwork);
 264                                 false
 265                         },
 266                 };
 267                 Ok((chain_tip, blocks_connected))
 268         }
 269
 270         /// Updates the chain tip, syncing the chain listener with any connected or disconnected
 271         /// blocks. Returns whether there were any such blocks.
 272         async fn update_chain_tip(&mut self, best_chain_tip: ValidatedBlockHeader) -> bool {
 273                 match self.chain_notifier.synchronize_listener(
 274                         best_chain_tip, &self.chain_tip, &mut self.chain_poller).await
 275                 {
 276                         Ok(_) => {
 277                                 self.chain_tip = best_chain_tip;
 278                                 true
 279                         },
 280                         Err((_, Some(chain_tip))) if chain_tip.block_hash != self.chain_tip.block_hash => {
 281                                 self.chain_tip = chain_tip;
 282                                 true
 283                         },
 284                         Err(_) => false,
 285                 }
 286         }
 287 }
 288
 289 /// Notifies [listeners] of blocks that have been connected or disconnected from the chain.
 290 ///
 291 /// [listeners]: lightning::chain::Listen
 292 pub struct ChainNotifier<'a, C: Cache, L: Deref> where L::Target: chain::Listen {
 293         /// Cache for looking up headers before fetching from a block source.
 294         header_cache: &'a mut C,
 295
 296         /// Listener that will be notified of connected or disconnected blocks.
 297         chain_listener: L,
 298 }
 299
 300 /// Changes made to the chain between subsequent polls that transformed it from having one chain tip
 301 /// to another.
 302 ///
 303 /// Blocks are given in height-descending order. Therefore, blocks are first disconnected in order
 304 /// before new blocks are connected in reverse order.
 305 struct ChainDifference {
 306         /// The most recent ancestor common between the chain tips.
 307         ///
 308         /// If there are any disconnected blocks, this is where the chain forked.
 309         common_ancestor: ValidatedBlockHeader,
 310
 311         /// Blocks that were disconnected from the chain since the last poll.
 312         disconnected_blocks: Vec<ValidatedBlockHeader>,
 313
 314         /// Blocks that were connected to the chain since the last poll.
 315         connected_blocks: Vec<ValidatedBlockHeader>,
 316 }
 317
 318 impl<'a, C: Cache, L: Deref> ChainNotifier<'a, C, L> where L::Target: chain::Listen {
 319         /// Finds the first common ancestor between `new_header` and `old_header`, disconnecting blocks
 320         /// from `old_header` to get to that point and then connecting blocks until `new_header`.
 321         ///
 322         /// Validates headers along the transition path, but doesn't fetch blocks until the chain is
 323         /// disconnected to the fork point. Thus, this may return an `Err` that includes where the tip
 324         /// ended up which may not be `new_header`. Note that the returned `Err` contains `Some` header
 325         /// if and only if the transition from `old_header` to `new_header` is valid.
 326         async fn synchronize_listener<P: Poll>(
 327                 &mut self,
 328                 new_header: ValidatedBlockHeader,
 329                 old_header: &ValidatedBlockHeader,
 330                 chain_poller: &mut P,
 331         ) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
 332                 let difference = self.find_difference(new_header, old_header, chain_poller).await
 333                         .map_err(|e| (e, None))?;
 334                 self.disconnect_blocks(difference.disconnected_blocks);
 335                 self.connect_blocks(
 336                         difference.common_ancestor,
 337                         difference.connected_blocks,
 338                         chain_poller,
 339                 ).await
 340         }
 341
 342         /// Returns the changes needed to produce the chain with `current_header` as its tip from the
 343         /// chain with `prev_header` as its tip.
 344         ///
 345         /// Walks backwards from `current_header` and `prev_header`, finding the common ancestor.
 346         async fn find_difference<P: Poll>(
 347                 &self,
 348                 current_header: ValidatedBlockHeader,
 349                 prev_header: &ValidatedBlockHeader,
 350                 chain_poller: &mut P,
 351         ) -> BlockSourceResult<ChainDifference> {
 352                 let mut disconnected_blocks = Vec::new();
 353                 let mut connected_blocks = Vec::new();
 354                 let mut current = current_header;
 355                 let mut previous = *prev_header;
 356                 loop {
 357                         // Found the common ancestor.
 358                         if current.block_hash == previous.block_hash {
 359                                 break;
 360                         }
 361
 362                         // Walk back the chain, finding blocks needed to connect and disconnect. Only walk back
 363                         // the header with the greater height, or both if equal heights.
 364                         let current_height = current.height;
 365                         let previous_height = previous.height;
 366                         if current_height <= previous_height {
 367                                 disconnected_blocks.push(previous);
 368                                 previous = self.look_up_previous_header(chain_poller, &previous).await?;
 369                         }
 370                         if current_height >= previous_height {
 371                                 connected_blocks.push(current);
 372                                 current = self.look_up_previous_header(chain_poller, &current).await?;
 373                         }
 374                 }
 375
 376                 let common_ancestor = current;
 377                 Ok(ChainDifference { common_ancestor, disconnected_blocks, connected_blocks })
 378         }
 379
 380         /// Returns the previous header for the given header, either by looking it up in the cache or
 381         /// fetching it if not found.
 382         async fn look_up_previous_header<P: Poll>(
 383                 &self,
 384                 chain_poller: &mut P,
 385                 header: &ValidatedBlockHeader,
 386         ) -> BlockSourceResult<ValidatedBlockHeader> {
 387                 match self.header_cache.look_up(&header.header.prev_blockhash) {
 388                         Some(prev_header) => Ok(*prev_header),
 389                         None => chain_poller.look_up_previous_header(header).await,
 390                 }
 391         }
 392
 393         /// Notifies the chain listeners of disconnected blocks.
 394         fn disconnect_blocks(&mut self, mut disconnected_blocks: Vec<ValidatedBlockHeader>) {
 395                 for header in disconnected_blocks.drain(..) {
 396                         if let Some(cached_header) = self.header_cache.block_disconnected(&header.block_hash) {
 397                                 assert_eq!(cached_header, header);
 398                         }
 399                         self.chain_listener.block_disconnected(&header.header, header.height);
 400                 }
 401         }
 402
 403         /// Notifies the chain listeners of connected blocks.
 404         async fn connect_blocks<P: Poll>(
 405                 &mut self,
 406                 mut new_tip: ValidatedBlockHeader,
 407                 mut connected_blocks: Vec<ValidatedBlockHeader>,
 408                 chain_poller: &mut P,
 409         ) -> Result<(), (BlockSourceError, Option<ValidatedBlockHeader>)> {
 410                 for header in connected_blocks.drain(..).rev() {
 411                         let height = header.height;
 412                         let block_data = chain_poller
 413                                 .fetch_block(&header).await
 414                                 .or_else(|e| Err((e, Some(new_tip))))?;
 415                         debug_assert_eq!(block_data.block_hash, header.block_hash);
 416
 417                         match block_data.deref() {
 418                                 BlockData::FullBlock(block) => {
 419                                         self.chain_listener.block_connected(&block, height);
 420                                 },
 421                                 BlockData::HeaderOnly(header) => {
 422                                         self.chain_listener.filtered_block_connected(&header, &[], height);
 423                                 },
 424                         }
 425
 426                         self.header_cache.block_connected(header.block_hash, header);
 427                         new_tip = header;
 428                 }
 429
 430                 Ok(())
 431         }
 432 }
 433
 434 #[cfg(test)]
 435 mod spv_client_tests {
 436         use crate::test_utils::{Blockchain, NullChainListener};
 437         use super::*;
 438
 439         use bitcoin::network::constants::Network;
 440
 441         #[tokio::test]
 442         async fn poll_from_chain_without_headers() {
 443                 let mut chain = Blockchain::default().with_height(3).without_headers();
 444                 let best_tip = chain.at_height(1);
 445
 446                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 447                 let mut cache = UnboundedCache::new();
 448                 let mut listener = NullChainListener {};
 449                 let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener);
 450                 match client.poll_best_tip().await {
 451                         Err(e) => {
 452                                 assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
 453                                 assert_eq!(e.into_inner().as_ref().to_string(), "header not found");
 454                         },
 455                         Ok(_) => panic!("Expected error"),
 456                 }
 457                 assert_eq!(client.chain_tip, best_tip);
 458         }
 459
 460         #[tokio::test]
 461         async fn poll_from_chain_with_common_tip() {
 462                 let mut chain = Blockchain::default().with_height(3);
 463                 let common_tip = chain.tip();
 464
 465                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 466                 let mut cache = UnboundedCache::new();
 467                 let mut listener = NullChainListener {};
 468                 let mut client = SpvClient::new(common_tip, poller, &mut cache, &mut listener);
 469                 match client.poll_best_tip().await {
 470                         Err(e) => panic!("Unexpected error: {:?}", e),
 471                         Ok((chain_tip, blocks_connected)) => {
 472                                 assert_eq!(chain_tip, ChainTip::Common);
 473                                 assert!(!blocks_connected);
 474                         },
 475                 }
 476                 assert_eq!(client.chain_tip, common_tip);
 477         }
 478
 479         #[tokio::test]
 480         async fn poll_from_chain_with_better_tip() {
 481                 let mut chain = Blockchain::default().with_height(3);
 482                 let new_tip = chain.tip();
 483                 let old_tip = chain.at_height(1);
 484
 485                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 486                 let mut cache = UnboundedCache::new();
 487                 let mut listener = NullChainListener {};
 488                 let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
 489                 match client.poll_best_tip().await {
 490                         Err(e) => panic!("Unexpected error: {:?}", e),
 491                         Ok((chain_tip, blocks_connected)) => {
 492                                 assert_eq!(chain_tip, ChainTip::Better(new_tip));
 493                                 assert!(blocks_connected);
 494                         },
 495                 }
 496                 assert_eq!(client.chain_tip, new_tip);
 497         }
 498
 499         #[tokio::test]
 500         async fn poll_from_chain_with_better_tip_and_without_any_new_blocks() {
 501                 let mut chain = Blockchain::default().with_height(3).without_blocks(2..);
 502                 let new_tip = chain.tip();
 503                 let old_tip = chain.at_height(1);
 504
 505                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 506                 let mut cache = UnboundedCache::new();
 507                 let mut listener = NullChainListener {};
 508                 let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
 509                 match client.poll_best_tip().await {
 510                         Err(e) => panic!("Unexpected error: {:?}", e),
 511                         Ok((chain_tip, blocks_connected)) => {
 512                                 assert_eq!(chain_tip, ChainTip::Better(new_tip));
 513                                 assert!(!blocks_connected);
 514                         },
 515                 }
 516                 assert_eq!(client.chain_tip, old_tip);
 517         }
 518
 519         #[tokio::test]
 520         async fn poll_from_chain_with_better_tip_and_without_some_new_blocks() {
 521                 let mut chain = Blockchain::default().with_height(3).without_blocks(3..);
 522                 let new_tip = chain.tip();
 523                 let old_tip = chain.at_height(1);
 524
 525                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 526                 let mut cache = UnboundedCache::new();
 527                 let mut listener = NullChainListener {};
 528                 let mut client = SpvClient::new(old_tip, poller, &mut cache, &mut listener);
 529                 match client.poll_best_tip().await {
 530                         Err(e) => panic!("Unexpected error: {:?}", e),
 531                         Ok((chain_tip, blocks_connected)) => {
 532                                 assert_eq!(chain_tip, ChainTip::Better(new_tip));
 533                                 assert!(blocks_connected);
 534                         },
 535                 }
 536                 assert_eq!(client.chain_tip, chain.at_height(2));
 537         }
 538
 539         #[tokio::test]
 540         async fn poll_from_chain_with_worse_tip() {
 541                 let mut chain = Blockchain::default().with_height(3);
 542                 let best_tip = chain.tip();
 543                 chain.disconnect_tip();
 544                 let worse_tip = chain.tip();
 545
 546                 let poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 547                 let mut cache = UnboundedCache::new();
 548                 let mut listener = NullChainListener {};
 549                 let mut client = SpvClient::new(best_tip, poller, &mut cache, &mut listener);
 550                 match client.poll_best_tip().await {
 551                         Err(e) => panic!("Unexpected error: {:?}", e),
 552                         Ok((chain_tip, blocks_connected)) => {
 553                                 assert_eq!(chain_tip, ChainTip::Worse(worse_tip));
 554                                 assert!(!blocks_connected);
 555                         },
 556                 }
 557                 assert_eq!(client.chain_tip, best_tip);
 558         }
 559 }
 560
 561 #[cfg(test)]
 562 mod chain_notifier_tests {
 563         use crate::test_utils::{Blockchain, MockChainListener};
 564         use super::*;
 565
 566         use bitcoin::network::constants::Network;
 567
 568         #[tokio::test]
 569         async fn sync_from_same_chain() {
 570                 let mut chain = Blockchain::default().with_height(3);
 571
 572                 let new_tip = chain.tip();
 573                 let old_tip = chain.at_height(1);
 574                 let chain_listener = &MockChainListener::new()
 575                         .expect_block_connected(*chain.at_height(2))
 576                         .expect_block_connected(*new_tip);
 577                 let mut notifier = ChainNotifier {
 578                         header_cache: &mut chain.header_cache(0..=1),
 579                         chain_listener,
 580                 };
 581                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 582                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 583                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 584                         Ok(_) => {},
 585                 }
 586         }
 587
 588         #[tokio::test]
 589         async fn sync_from_different_chains() {
 590                 let mut test_chain = Blockchain::with_network(Network::Testnet).with_height(1);
 591                 let main_chain = Blockchain::with_network(Network::Bitcoin).with_height(1);
 592
 593                 let new_tip = test_chain.tip();
 594                 let old_tip = main_chain.tip();
 595                 let chain_listener = &MockChainListener::new();
 596                 let mut notifier = ChainNotifier {
 597                         header_cache: &mut main_chain.header_cache(0..=1),
 598                         chain_listener,
 599                 };
 600                 let mut poller = poll::ChainPoller::new(&mut test_chain, Network::Testnet);
 601                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 602                         Err((e, _)) => {
 603                                 assert_eq!(e.kind(), BlockSourceErrorKind::Persistent);
 604                                 assert_eq!(e.into_inner().as_ref().to_string(), "genesis block reached");
 605                         },
 606                         Ok(_) => panic!("Expected error"),
 607                 }
 608         }
 609
 610         #[tokio::test]
 611         async fn sync_from_equal_length_fork() {
 612                 let main_chain = Blockchain::default().with_height(2);
 613                 let mut fork_chain = main_chain.fork_at_height(1);
 614
 615                 let new_tip = fork_chain.tip();
 616                 let old_tip = main_chain.tip();
 617                 let chain_listener = &MockChainListener::new()
 618                         .expect_block_disconnected(*old_tip)
 619                         .expect_block_connected(*new_tip);
 620                 let mut notifier = ChainNotifier {
 621                         header_cache: &mut main_chain.header_cache(0..=2),
 622                         chain_listener,
 623                 };
 624                 let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
 625                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 626                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 627                         Ok(_) => {},
 628                 }
 629         }
 630
 631         #[tokio::test]
 632         async fn sync_from_shorter_fork() {
 633                 let main_chain = Blockchain::default().with_height(3);
 634                 let mut fork_chain = main_chain.fork_at_height(1);
 635                 fork_chain.disconnect_tip();
 636
 637                 let new_tip = fork_chain.tip();
 638                 let old_tip = main_chain.tip();
 639                 let chain_listener = &MockChainListener::new()
 640                         .expect_block_disconnected(*old_tip)
 641                         .expect_block_disconnected(*main_chain.at_height(2))
 642                         .expect_block_connected(*new_tip);
 643                 let mut notifier = ChainNotifier {
 644                         header_cache: &mut main_chain.header_cache(0..=3),
 645                         chain_listener,
 646                 };
 647                 let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
 648                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 649                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 650                         Ok(_) => {},
 651                 }
 652         }
 653
 654         #[tokio::test]
 655         async fn sync_from_longer_fork() {
 656                 let mut main_chain = Blockchain::default().with_height(3);
 657                 let mut fork_chain = main_chain.fork_at_height(1);
 658                 main_chain.disconnect_tip();
 659
 660                 let new_tip = fork_chain.tip();
 661                 let old_tip = main_chain.tip();
 662                 let chain_listener = &MockChainListener::new()
 663                         .expect_block_disconnected(*old_tip)
 664                         .expect_block_connected(*fork_chain.at_height(2))
 665                         .expect_block_connected(*new_tip);
 666                 let mut notifier = ChainNotifier {
 667                         header_cache: &mut main_chain.header_cache(0..=2),
 668                         chain_listener,
 669                 };
 670                 let mut poller = poll::ChainPoller::new(&mut fork_chain, Network::Testnet);
 671                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 672                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 673                         Ok(_) => {},
 674                 }
 675         }
 676
 677         #[tokio::test]
 678         async fn sync_from_chain_without_headers() {
 679                 let mut chain = Blockchain::default().with_height(3).without_headers();
 680
 681                 let new_tip = chain.tip();
 682                 let old_tip = chain.at_height(1);
 683                 let chain_listener = &MockChainListener::new();
 684                 let mut notifier = ChainNotifier {
 685                         header_cache: &mut chain.header_cache(0..=1),
 686                         chain_listener,
 687                 };
 688                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 689                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 690                         Err((_, tip)) => assert_eq!(tip, None),
 691                         Ok(_) => panic!("Expected error"),
 692                 }
 693         }
 694
 695         #[tokio::test]
 696         async fn sync_from_chain_without_any_new_blocks() {
 697                 let mut chain = Blockchain::default().with_height(3).without_blocks(2..);
 698
 699                 let new_tip = chain.tip();
 700                 let old_tip = chain.at_height(1);
 701                 let chain_listener = &MockChainListener::new();
 702                 let mut notifier = ChainNotifier {
 703                         header_cache: &mut chain.header_cache(0..=3),
 704                         chain_listener,
 705                 };
 706                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 707                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 708                         Err((_, tip)) => assert_eq!(tip, Some(old_tip)),
 709                         Ok(_) => panic!("Expected error"),
 710                 }
 711         }
 712
 713         #[tokio::test]
 714         async fn sync_from_chain_without_some_new_blocks() {
 715                 let mut chain = Blockchain::default().with_height(3).without_blocks(3..);
 716
 717                 let new_tip = chain.tip();
 718                 let old_tip = chain.at_height(1);
 719                 let chain_listener = &MockChainListener::new()
 720                         .expect_block_connected(*chain.at_height(2));
 721                 let mut notifier = ChainNotifier {
 722                         header_cache: &mut chain.header_cache(0..=3),
 723                         chain_listener,
 724                 };
 725                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 726                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 727                         Err((_, tip)) => assert_eq!(tip, Some(chain.at_height(2))),
 728                         Ok(_) => panic!("Expected error"),
 729                 }
 730         }
 731
 732         #[tokio::test]
 733         async fn sync_from_chain_with_filtered_blocks() {
 734                 let mut chain = Blockchain::default().with_height(3).filtered_blocks();
 735
 736                 let new_tip = chain.tip();
 737                 let old_tip = chain.at_height(1);
 738                 let chain_listener = &MockChainListener::new()
 739                         .expect_filtered_block_connected(*chain.at_height(2))
 740                         .expect_filtered_block_connected(*new_tip);
 741                 let mut notifier = ChainNotifier {
 742                         header_cache: &mut chain.header_cache(0..=1),
 743                         chain_listener,
 744                 };
 745                 let mut poller = poll::ChainPoller::new(&mut chain, Network::Testnet);
 746                 match notifier.synchronize_listener(new_tip, &old_tip, &mut poller).await {
 747                         Err((e, _)) => panic!("Unexpected error: {:?}", e),
 748                         Ok(_) => {},
 749                 }
 750         }
 751
 752 }