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);
162 match self.get_confirmed_transactions(&sync_state) {
163 Ok(confirmed_txs) => {
164 // Double-check the tip hash. If it changed, a reorg happened since
165 // we started syncing and we need to restart last-minute.
166 match self.check_update_tip(&mut tip_header, &mut tip_height) {
168 num_confirmed += confirmed_txs.len();
169 sync_state.sync_confirmed_transactions(
175 log_debug!(self.logger,
176 "Encountered inconsistency during transaction sync, restarting.");
177 sync_state.pending_sync = true;
181 // (Semi-)permanent failure, retry later.
182 log_error!(self.logger,
183 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
187 sync_state.pending_sync = true;
188 return Err(TxSyncError::from(err));
192 Err(InternalError::Inconsistency) => {
193 // Immediately restart syncing when we encounter any inconsistencies.
194 log_debug!(self.logger,
195 "Encountered inconsistency during transaction sync, restarting.");
196 sync_state.pending_sync = true;
200 // (Semi-)permanent failure, retry later.
201 log_error!(self.logger,
202 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
206 sync_state.pending_sync = true;
207 return Err(TxSyncError::from(err));
210 sync_state.last_sync_hash = Some(tip_header.block_hash());
211 sync_state.pending_sync = false;
214 #[cfg(feature = "time")]
215 log_debug!(self.logger,
216 "Finished transaction sync at tip {} in {}ms: {} confirmed, {} unconfirmed.",
217 tip_header.block_hash(), start_time.elapsed().as_millis(), num_confirmed,
219 #[cfg(not(feature = "time"))]
220 log_debug!(self.logger,
221 "Finished transaction sync at tip {}: {} confirmed, {} unconfirmed.",
222 tip_header.block_hash(), num_confirmed, num_unconfirmed);
226 fn check_update_tip(&self, cur_tip_header: &mut Header, cur_tip_height: &mut u32)
227 -> Result<bool, InternalError>
229 let check_notification = self.client.block_headers_subscribe()?;
230 let check_tip_hash = check_notification.header.block_hash();
232 // Restart if either the tip changed or we got some divergent tip
233 // change notification since we started. In the latter case we
234 // make sure we clear the queue before continuing.
235 let mut restart_sync = check_tip_hash != cur_tip_header.block_hash();
236 while let Some(queued_notif) = self.client.block_headers_pop()? {
237 if queued_notif.header.block_hash() != check_tip_hash {
243 *cur_tip_header = check_notification.header;
244 *cur_tip_height = check_notification.height as u32;
251 fn get_confirmed_transactions(
252 &self, sync_state: &SyncState,
253 ) -> Result<Vec<ConfirmedTx>, InternalError> {
255 // First, check the confirmation status of registered transactions as well as the
256 // status of dependent transactions of registered outputs.
257 let mut confirmed_txs = Vec::new();
258 let mut watched_script_pubkeys = Vec::with_capacity(
259 sync_state.watched_transactions.len() + sync_state.watched_outputs.len());
260 let mut watched_txs = Vec::with_capacity(sync_state.watched_transactions.len());
262 for txid in &sync_state.watched_transactions {
263 match self.client.transaction_get(&txid) {
265 watched_txs.push((txid, tx.clone()));
266 if let Some(tx_out) = tx.output.first() {
267 // We watch an arbitrary output of the transaction of interest in order to
268 // retrieve the associated script history, before narrowing down our search
269 // through `filter`ing by `txid` below.
270 watched_script_pubkeys.push(tx_out.script_pubkey.clone());
272 debug_assert!(false, "Failed due to retrieving invalid tx data.");
273 log_error!(self.logger, "Failed due to retrieving invalid tx data.");
274 return Err(InternalError::Failed);
277 Err(electrum_client::Error::Protocol(_)) => {
278 // We couldn't find the tx, do nothing.
281 log_error!(self.logger, "Failed to look up transaction {}: {}.", txid, e);
282 return Err(InternalError::Failed);
287 let num_tx_lookups = watched_script_pubkeys.len();
288 debug_assert_eq!(num_tx_lookups, watched_txs.len());
290 for output in sync_state.watched_outputs.values() {
291 watched_script_pubkeys.push(output.script_pubkey.clone());
294 let num_output_spend_lookups = watched_script_pubkeys.len() - num_tx_lookups;
295 debug_assert_eq!(num_output_spend_lookups, sync_state.watched_outputs.len());
297 match self.client.batch_script_get_history(watched_script_pubkeys.iter().map(|s| s.deref()))
300 let (tx_results, output_results) = results.split_at(num_tx_lookups);
301 debug_assert_eq!(num_output_spend_lookups, output_results.len());
303 for (i, script_history) in tx_results.iter().enumerate() {
304 let (txid, tx) = &watched_txs[i];
305 let mut filtered_history = script_history.iter().filter(|h| h.tx_hash == **txid);
306 if let Some(history) = filtered_history.next()
308 let prob_conf_height = history.height as u32;
309 let confirmed_tx = self.get_confirmed_tx(tx, prob_conf_height)?;
310 confirmed_txs.push(confirmed_tx);
312 debug_assert!(filtered_history.next().is_none());
315 for (watched_output, script_history) in sync_state.watched_outputs.values()
318 for possible_output_spend in script_history {
319 if possible_output_spend.height <= 0 {
323 let txid = possible_output_spend.tx_hash;
324 match self.client.transaction_get(&txid) {
326 let mut is_spend = false;
327 for txin in &tx.input {
328 let watched_outpoint = watched_output.outpoint
329 .into_bitcoin_outpoint();
330 if txin.previous_output == watched_outpoint {
340 let prob_conf_height = possible_output_spend.height as u32;
341 let confirmed_tx = self.get_confirmed_tx(&tx, prob_conf_height)?;
342 confirmed_txs.push(confirmed_tx);
345 log_trace!(self.logger,
346 "Inconsistency: Tx {} was unconfirmed during syncing: {}",
348 return Err(InternalError::Inconsistency);
355 log_error!(self.logger, "Failed to look up script histories: {}.", e);
356 return Err(InternalError::Failed);
360 // Sort all confirmed transactions first by block height, then by in-block
361 // position, and finally feed them to the interface in order.
362 confirmed_txs.sort_unstable_by(|tx1, tx2| {
363 tx1.block_height.cmp(&tx2.block_height).then_with(|| tx1.pos.cmp(&tx2.pos))
369 fn get_unconfirmed_transactions(
370 &self, confirmables: &Vec<&(dyn Confirm + Sync + Send)>,
371 ) -> Result<Vec<Txid>, InternalError> {
372 // Query the interface for relevant txids and check whether the relevant blocks are still
373 // in the best chain, mark them unconfirmed otherwise
374 let relevant_txids = confirmables
376 .flat_map(|c| c.get_relevant_txids())
377 .collect::<HashSet<(Txid, u32, Option<BlockHash>)>>();
379 let mut unconfirmed_txs = Vec::new();
381 for (txid, conf_height, block_hash_opt) in relevant_txids {
382 if let Some(block_hash) = block_hash_opt {
383 let block_header = self.client.block_header(conf_height as usize)?;
384 if block_header.block_hash() == block_hash {
385 // Skip if the tx is still confirmed in the block in question.
389 unconfirmed_txs.push(txid);
391 log_error!(self.logger,
392 "Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
393 panic!("Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
399 fn get_confirmed_tx(&self, tx: &Transaction, prob_conf_height: u32)
400 -> Result<ConfirmedTx, InternalError>
402 let txid = tx.txid();
403 match self.client.transaction_get_merkle(&txid, prob_conf_height as usize) {
405 debug_assert_eq!(prob_conf_height, merkle_res.block_height as u32);
406 match self.client.block_header(prob_conf_height as usize) {
407 Ok(block_header) => {
408 let pos = merkle_res.pos;
409 if !self.validate_merkle_proof(&txid,
410 &block_header.merkle_root, merkle_res)?
412 log_trace!(self.logger,
413 "Inconsistency: Block {} was unconfirmed during syncing.",
414 block_header.block_hash());
415 return Err(InternalError::Inconsistency);
417 let confirmed_tx = ConfirmedTx {
419 block_header, block_height: prob_conf_height,
425 log_error!(self.logger,
426 "Failed to retrieve block header for height {}: {}.",
427 prob_conf_height, e);
428 Err(InternalError::Failed)
433 log_trace!(self.logger,
434 "Inconsistency: Tx {} was unconfirmed during syncing: {}",
436 Err(InternalError::Inconsistency)
441 /// Returns a reference to the underlying Electrum client.
442 pub fn client(&self) -> &ElectrumClient {
446 fn validate_merkle_proof(&self, txid: &Txid, merkle_root: &TxMerkleNode,
447 merkle_res: GetMerkleRes) -> Result<bool, InternalError>
449 let mut index = merkle_res.pos;
450 let mut cur = txid.to_raw_hash();
451 for mut bytes in merkle_res.merkle {
453 // unwrap() safety: `bytes` has len 32 so `from_slice` can never fail.
454 let next_hash = Sha256d::from_slice(&bytes).unwrap();
455 let (left, right) = if index % 2 == 0 {
461 let data = [&left[..], &right[..]].concat();
462 cur = Sha256d::hash(&data);
466 Ok(cur == merkle_root.to_raw_hash())
470 impl<L: Deref> Filter for ElectrumSyncClient<L>
474 fn register_tx(&self, txid: &Txid, _script_pubkey: &Script) {
475 let mut locked_queue = self.queue.lock().unwrap();
476 locked_queue.transactions.insert(*txid);
479 fn register_output(&self, output: WatchedOutput) {
480 let mut locked_queue = self.queue.lock().unwrap();
481 locked_queue.outputs.insert(output.outpoint.into_bitcoin_outpoint(), output);