1 use crate::common::{ConfirmedTx, SyncState, FilterQueue};
2 use crate::error::{TxSyncError, InternalError};
4 use electrum_client::Client as ElectrumClient;
5 use electrum_client::ElectrumApi;
6 use electrum_client::GetMerkleRes;
8 use lightning::util::logger::Logger;
9 use lightning::{log_error, log_debug, log_trace};
10 use lightning::chain::WatchedOutput;
11 use lightning::chain::{Confirm, Filter};
13 use bitcoin::{BlockHash, Script, Transaction, Txid};
14 use bitcoin::block::Header;
15 use bitcoin::hash_types::TxMerkleNode;
16 use bitcoin::hashes::Hash;
17 use bitcoin::hashes::sha256d::Hash as Sha256d;
21 use std::collections::HashSet;
22 use std::time::Instant;
24 /// Synchronizes LDK with a given Electrum server.
26 /// Needs to be registered with a [`ChainMonitor`] via the [`Filter`] interface to be informed of
27 /// transactions and outputs to monitor for on-chain confirmation, unconfirmation, and
30 /// Note that registration via [`Filter`] needs to happen before any calls to
31 /// [`Watch::watch_channel`] to ensure we get notified of the items to monitor.
33 /// [`ChainMonitor`]: lightning::chain::chainmonitor::ChainMonitor
34 /// [`Watch::watch_channel`]: lightning::chain::Watch::watch_channel
35 /// [`Filter`]: lightning::chain::Filter
36 pub struct ElectrumSyncClient<L: Deref>
40 sync_state: Mutex<SyncState>,
41 queue: Mutex<FilterQueue>,
42 client: ElectrumClient,
46 impl<L: Deref> ElectrumSyncClient<L>
50 /// Returns a new [`ElectrumSyncClient`] object.
51 pub fn new(server_url: String, logger: L) -> Result<Self, TxSyncError> {
52 let client = ElectrumClient::new(&server_url).map_err(|e| {
53 log_error!(logger, "Failed to connect to electrum server '{}': {}", server_url, e);
57 Self::from_client(client, logger)
60 /// Returns a new [`ElectrumSyncClient`] object using the given Electrum client.
61 pub fn from_client(client: ElectrumClient, logger: L) -> Result<Self, TxSyncError> {
62 let sync_state = Mutex::new(SyncState::new());
63 let queue = Mutex::new(FilterQueue::new());
73 /// Synchronizes the given `confirmables` via their [`Confirm`] interface implementations. This
74 /// method should be called regularly to keep LDK up-to-date with current chain data.
76 /// For example, instances of [`ChannelManager`] and [`ChainMonitor`] can be informed about the
77 /// newest on-chain activity related to the items previously registered via the [`Filter`]
80 /// [`Confirm`]: lightning::chain::Confirm
81 /// [`ChainMonitor`]: lightning::chain::chainmonitor::ChainMonitor
82 /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
83 /// [`Filter`]: lightning::chain::Filter
84 pub fn sync(&self, confirmables: Vec<&(dyn Confirm + Sync + Send)>) -> Result<(), TxSyncError> {
85 // This lock makes sure we're syncing once at a time.
86 let mut sync_state = self.sync_state.lock().unwrap();
88 log_trace!(self.logger, "Starting transaction sync.");
89 #[cfg(feature = "time")]
90 let start_time = Instant::now();
91 let mut num_confirmed = 0;
92 let mut num_unconfirmed = 0;
94 // Clear any header notifications we might have gotten to keep the queue count low.
95 while let Some(_) = self.client.block_headers_pop()? {}
97 let tip_notification = self.client.block_headers_subscribe()?;
98 let mut tip_header = tip_notification.header;
99 let mut tip_height = tip_notification.height as u32;
102 let pending_registrations = self.queue.lock().unwrap().process_queues(&mut sync_state);
103 let tip_is_new = Some(tip_header.block_hash()) != sync_state.last_sync_hash;
105 // We loop until any registered transactions have been processed at least once, or the
106 // tip hasn't been updated during the last iteration.
107 if !sync_state.pending_sync && !pending_registrations && !tip_is_new {
111 // Update the known tip to the newest one.
113 // First check for any unconfirmed transactions and act on it immediately.
114 match self.get_unconfirmed_transactions(&confirmables) {
115 Ok(unconfirmed_txs) => {
116 // Double-check the tip hash. If it changed, a reorg happened since
117 // we started syncing and we need to restart last-minute.
118 match self.check_update_tip(&mut tip_header, &mut tip_height) {
120 num_unconfirmed += unconfirmed_txs.len();
121 sync_state.sync_unconfirmed_transactions(
127 log_debug!(self.logger,
128 "Encountered inconsistency during transaction sync, restarting.");
129 sync_state.pending_sync = true;
133 // (Semi-)permanent failure, retry later.
134 log_error!(self.logger,
135 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
139 sync_state.pending_sync = true;
140 return Err(TxSyncError::from(err));
145 // (Semi-)permanent failure, retry later.
146 log_error!(self.logger,
147 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
151 sync_state.pending_sync = true;
152 return Err(TxSyncError::from(err));
156 // Update the best block.
157 for c in &confirmables {
158 c.best_block_updated(&tip_header, tip_height);
161 // Prune any sufficiently confirmed output spends
162 sync_state.prune_output_spends(tip_height);
165 match self.get_confirmed_transactions(&sync_state) {
166 Ok(confirmed_txs) => {
167 // Double-check the tip hash. If it changed, a reorg happened since
168 // we started syncing and we need to restart last-minute.
169 match self.check_update_tip(&mut tip_header, &mut tip_height) {
171 num_confirmed += confirmed_txs.len();
172 sync_state.sync_confirmed_transactions(
178 log_debug!(self.logger,
179 "Encountered inconsistency during transaction sync, restarting.");
180 sync_state.pending_sync = true;
184 // (Semi-)permanent failure, retry later.
185 log_error!(self.logger,
186 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
190 sync_state.pending_sync = true;
191 return Err(TxSyncError::from(err));
195 Err(InternalError::Inconsistency) => {
196 // Immediately restart syncing when we encounter any inconsistencies.
197 log_debug!(self.logger,
198 "Encountered inconsistency during transaction sync, restarting.");
199 sync_state.pending_sync = true;
203 // (Semi-)permanent failure, retry later.
204 log_error!(self.logger,
205 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
209 sync_state.pending_sync = true;
210 return Err(TxSyncError::from(err));
213 sync_state.last_sync_hash = Some(tip_header.block_hash());
214 sync_state.pending_sync = false;
217 #[cfg(feature = "time")]
218 log_debug!(self.logger,
219 "Finished transaction sync at tip {} in {}ms: {} confirmed, {} unconfirmed.",
220 tip_header.block_hash(), start_time.elapsed().as_millis(), num_confirmed,
222 #[cfg(not(feature = "time"))]
223 log_debug!(self.logger,
224 "Finished transaction sync at tip {}: {} confirmed, {} unconfirmed.",
225 tip_header.block_hash(), num_confirmed, num_unconfirmed);
229 fn check_update_tip(&self, cur_tip_header: &mut Header, cur_tip_height: &mut u32)
230 -> Result<bool, InternalError>
232 let check_notification = self.client.block_headers_subscribe()?;
233 let check_tip_hash = check_notification.header.block_hash();
235 // Restart if either the tip changed or we got some divergent tip
236 // change notification since we started. In the latter case we
237 // make sure we clear the queue before continuing.
238 let mut restart_sync = check_tip_hash != cur_tip_header.block_hash();
239 while let Some(queued_notif) = self.client.block_headers_pop()? {
240 if queued_notif.header.block_hash() != check_tip_hash {
246 *cur_tip_header = check_notification.header;
247 *cur_tip_height = check_notification.height as u32;
254 fn get_confirmed_transactions(
255 &self, sync_state: &SyncState,
256 ) -> Result<Vec<ConfirmedTx>, InternalError> {
258 // First, check the confirmation status of registered transactions as well as the
259 // status of dependent transactions of registered outputs.
260 let mut confirmed_txs: Vec<ConfirmedTx> = Vec::new();
261 let mut watched_script_pubkeys = Vec::with_capacity(
262 sync_state.watched_transactions.len() + sync_state.watched_outputs.len());
263 let mut watched_txs = Vec::with_capacity(sync_state.watched_transactions.len());
265 for txid in &sync_state.watched_transactions {
266 match self.client.transaction_get(&txid) {
268 watched_txs.push((txid, tx.clone()));
269 if let Some(tx_out) = tx.output.first() {
270 // We watch an arbitrary output of the transaction of interest in order to
271 // retrieve the associated script history, before narrowing down our search
272 // through `filter`ing by `txid` below.
273 watched_script_pubkeys.push(tx_out.script_pubkey.clone());
275 debug_assert!(false, "Failed due to retrieving invalid tx data.");
276 log_error!(self.logger, "Failed due to retrieving invalid tx data.");
277 return Err(InternalError::Failed);
280 Err(electrum_client::Error::Protocol(_)) => {
281 // We couldn't find the tx, do nothing.
284 log_error!(self.logger, "Failed to look up transaction {}: {}.", txid, e);
285 return Err(InternalError::Failed);
290 let num_tx_lookups = watched_script_pubkeys.len();
291 debug_assert_eq!(num_tx_lookups, watched_txs.len());
293 for output in sync_state.watched_outputs.values() {
294 watched_script_pubkeys.push(output.script_pubkey.clone());
297 let num_output_spend_lookups = watched_script_pubkeys.len() - num_tx_lookups;
298 debug_assert_eq!(num_output_spend_lookups, sync_state.watched_outputs.len());
300 match self.client.batch_script_get_history(watched_script_pubkeys.iter().map(|s| s.deref()))
303 let (tx_results, output_results) = results.split_at(num_tx_lookups);
304 debug_assert_eq!(num_output_spend_lookups, output_results.len());
306 for (i, script_history) in tx_results.iter().enumerate() {
307 let (txid, tx) = &watched_txs[i];
308 if confirmed_txs.iter().any(|ctx| ctx.txid == **txid) {
311 let mut filtered_history = script_history.iter().filter(|h| h.tx_hash == **txid);
312 if let Some(history) = filtered_history.next()
314 let prob_conf_height = history.height as u32;
315 let confirmed_tx = self.get_confirmed_tx(tx, prob_conf_height)?;
316 confirmed_txs.push(confirmed_tx);
318 debug_assert!(filtered_history.next().is_none());
321 for (watched_output, script_history) in sync_state.watched_outputs.values()
324 for possible_output_spend in script_history {
325 if possible_output_spend.height <= 0 {
329 let txid = possible_output_spend.tx_hash;
330 if confirmed_txs.iter().any(|ctx| ctx.txid == txid) {
334 match self.client.transaction_get(&txid) {
336 let mut is_spend = false;
337 for txin in &tx.input {
338 let watched_outpoint = watched_output.outpoint
339 .into_bitcoin_outpoint();
340 if txin.previous_output == watched_outpoint {
350 let prob_conf_height = possible_output_spend.height as u32;
351 let confirmed_tx = self.get_confirmed_tx(&tx, prob_conf_height)?;
352 confirmed_txs.push(confirmed_tx);
355 log_trace!(self.logger,
356 "Inconsistency: Tx {} was unconfirmed during syncing: {}",
358 return Err(InternalError::Inconsistency);
365 log_error!(self.logger, "Failed to look up script histories: {}.", e);
366 return Err(InternalError::Failed);
370 // Sort all confirmed transactions first by block height, then by in-block
371 // position, and finally feed them to the interface in order.
372 confirmed_txs.sort_unstable_by(|tx1, tx2| {
373 tx1.block_height.cmp(&tx2.block_height).then_with(|| tx1.pos.cmp(&tx2.pos))
379 fn get_unconfirmed_transactions(
380 &self, confirmables: &Vec<&(dyn Confirm + Sync + Send)>,
381 ) -> Result<Vec<Txid>, InternalError> {
382 // Query the interface for relevant txids and check whether the relevant blocks are still
383 // in the best chain, mark them unconfirmed otherwise
384 let relevant_txids = confirmables
386 .flat_map(|c| c.get_relevant_txids())
387 .collect::<HashSet<(Txid, u32, Option<BlockHash>)>>();
389 let mut unconfirmed_txs = Vec::new();
391 for (txid, conf_height, block_hash_opt) in relevant_txids {
392 if let Some(block_hash) = block_hash_opt {
393 let block_header = self.client.block_header(conf_height as usize)?;
394 if block_header.block_hash() == block_hash {
395 // Skip if the tx is still confirmed in the block in question.
399 unconfirmed_txs.push(txid);
401 log_error!(self.logger,
402 "Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
403 panic!("Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
409 fn get_confirmed_tx(&self, tx: &Transaction, prob_conf_height: u32)
410 -> Result<ConfirmedTx, InternalError>
412 let txid = tx.txid();
413 match self.client.transaction_get_merkle(&txid, prob_conf_height as usize) {
415 debug_assert_eq!(prob_conf_height, merkle_res.block_height as u32);
416 match self.client.block_header(prob_conf_height as usize) {
417 Ok(block_header) => {
418 let pos = merkle_res.pos;
419 if !self.validate_merkle_proof(&txid,
420 &block_header.merkle_root, merkle_res)?
422 log_trace!(self.logger,
423 "Inconsistency: Block {} was unconfirmed during syncing.",
424 block_header.block_hash());
425 return Err(InternalError::Inconsistency);
427 let confirmed_tx = ConfirmedTx {
430 block_header, block_height: prob_conf_height,
436 log_error!(self.logger,
437 "Failed to retrieve block header for height {}: {}.",
438 prob_conf_height, e);
439 Err(InternalError::Failed)
444 log_trace!(self.logger,
445 "Inconsistency: Tx {} was unconfirmed during syncing: {}",
447 Err(InternalError::Inconsistency)
452 /// Returns a reference to the underlying Electrum client.
453 pub fn client(&self) -> &ElectrumClient {
457 fn validate_merkle_proof(&self, txid: &Txid, merkle_root: &TxMerkleNode,
458 merkle_res: GetMerkleRes) -> Result<bool, InternalError>
460 let mut index = merkle_res.pos;
461 let mut cur = txid.to_raw_hash();
462 for mut bytes in merkle_res.merkle {
464 // unwrap() safety: `bytes` has len 32 so `from_slice` can never fail.
465 let next_hash = Sha256d::from_slice(&bytes).unwrap();
466 let (left, right) = if index % 2 == 0 {
472 let data = [&left[..], &right[..]].concat();
473 cur = Sha256d::hash(&data);
477 Ok(cur == merkle_root.to_raw_hash())
481 impl<L: Deref> Filter for ElectrumSyncClient<L>
485 fn register_tx(&self, txid: &Txid, _script_pubkey: &Script) {
486 let mut locked_queue = self.queue.lock().unwrap();
487 locked_queue.transactions.insert(*txid);
490 fn register_output(&self, output: WatchedOutput) {
491 let mut locked_queue = self.queue.lock().unwrap();
492 locked_queue.outputs.insert(output.outpoint.into_bitcoin_outpoint(), output);