1 //! Traits and utility impls which allow other parts of rust-lightning to interact with the
4 //! Includes traits for monitoring and receiving notifications of new blocks and block
5 //! disconnections, transaction broadcasting, and feerate information requests.
7 use bitcoin::blockdata::block::{Block, BlockHeader};
8 use bitcoin::blockdata::transaction::Transaction;
9 use bitcoin::blockdata::script::Script;
10 use bitcoin::blockdata::constants::genesis_block;
11 use bitcoin::util::hash::BitcoinHash;
12 use bitcoin::network::constants::Network;
13 use bitcoin::hash_types::{Txid, BlockHash};
15 use std::sync::{Mutex, MutexGuard, Arc};
16 use std::sync::atomic::{AtomicUsize, Ordering};
17 use std::collections::HashSet;
19 use std::marker::PhantomData;
22 /// Used to give chain error details upstream
25 /// Client doesn't support UTXO lookup (but the chain hash matches our genesis block hash)
27 /// Chain isn't the one watched
29 /// Tx doesn't exist or is unconfirmed
33 /// An interface to request notification of certain scripts as they appear the
36 /// Note that all of the functions implemented here *must* be reentrant-safe (obviously - they're
37 /// called from inside the library in response to ChainListener events, P2P events, or timer
39 pub trait ChainWatchInterface: Sync + Send {
40 /// Provides a txid/random-scriptPubKey-in-the-tx which much be watched for.
41 fn install_watch_tx(&self, txid: &Txid, script_pub_key: &Script);
43 /// Provides an outpoint which must be watched for, providing any transactions which spend the
45 fn install_watch_outpoint(&self, outpoint: (Txid, u32), out_script: &Script);
47 /// Indicates that a listener needs to see all transactions.
48 fn watch_all_txn(&self);
50 /// Gets the script and value in satoshis for a given unspent transaction output given a
51 /// short_channel_id (aka unspent_tx_output_identier). For BTC/tBTC channels the top three
52 /// bytes are the block height, the next 3 the transaction index within the block, and the
53 /// final two the output within the transaction.
54 fn get_chain_utxo(&self, genesis_hash: BlockHash, unspent_tx_output_identifier: u64) -> Result<(Script, u64), ChainError>;
56 /// Gets the list of transaction indices within a given block that the ChainWatchInterface is
58 fn filter_block(&self, block: &Block) -> Vec<usize>;
60 /// Returns a usize that changes when the ChainWatchInterface's watched data is modified.
61 /// Users of `filter_block` should pre-save a copy of `reentered`'s return value and use it to
62 /// determine whether they need to re-filter a given block.
63 fn reentered(&self) -> usize;
66 /// An interface to send a transaction to the Bitcoin network.
67 pub trait BroadcasterInterface: Sync + Send {
68 /// Sends a transaction out to (hopefully) be mined.
69 fn broadcast_transaction(&self, tx: &Transaction);
72 /// A trait indicating a desire to listen for events from the chain
73 pub trait ChainListener: Sync + Send {
74 /// Notifies a listener that a block was connected.
76 /// The txn_matched array should be set to references to transactions which matched the
77 /// relevant installed watch outpoints/txn, or the full set of transactions in the block.
79 /// Note that if txn_matched includes only matched transactions, and a new
80 /// transaction/outpoint is watched during a block_connected call, the block *must* be
81 /// re-scanned with the new transaction/outpoints and block_connected should be called
82 /// again with the same header and (at least) the new transactions.
84 /// Note that if non-new transaction/outpoints are be registered during a call, a second call
85 /// *must not* happen.
87 /// This also means those counting confirmations using block_connected callbacks should watch
88 /// for duplicate headers and not count them towards confirmations!
89 fn block_connected(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[usize]);
90 /// Notifies a listener that a block was disconnected.
91 /// Unlike block_connected, this *must* never be called twice for the same disconnect event.
92 /// Height must be the one of the block which was disconnected (not new height of the best chain)
93 fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32);
96 /// An enum that represents the speed at which we want a transaction to confirm used for feerate
98 pub enum ConfirmationTarget {
99 /// We are happy with this transaction confirming slowly when feerate drops some.
101 /// We'd like this transaction to confirm without major delay, but 12-18 blocks is fine.
103 /// We'd like this transaction to confirm in the next few blocks.
107 /// A trait which should be implemented to provide feerate information on a number of time
110 /// Note that all of the functions implemented here *must* be reentrant-safe (obviously - they're
111 /// called from inside the library in response to ChainListener events, P2P events, or timer
113 pub trait FeeEstimator: Sync + Send {
114 /// Gets estimated satoshis of fee required per 1000 Weight-Units.
116 /// Must be no smaller than 253 (ie 1 satoshi-per-byte rounded up to ensure later round-downs
117 /// don't put us below 1 satoshi-per-byte).
119 /// This translates to:
120 /// * satoshis-per-byte * 250
121 /// * ceil(satoshis-per-kbyte / 4)
122 fn get_est_sat_per_1000_weight(&self, confirmation_target: ConfirmationTarget) -> u32;
125 /// Minimum relay fee as required by bitcoin network mempool policy.
126 pub const MIN_RELAY_FEE_SAT_PER_1000_WEIGHT: u64 = 4000;
128 /// Utility for tracking registered txn/outpoints and checking for matches
129 #[cfg_attr(test, derive(PartialEq))]
130 pub struct ChainWatchedUtil {
133 // We are more conservative in matching during testing to ensure everything matches *exactly*,
134 // even though during normal runtime we take more optimized match approaches...
136 watched_txn: HashSet<(Txid, Script)>,
138 watched_txn: HashSet<Script>,
140 watched_outpoints: HashSet<(Txid, u32)>,
143 impl ChainWatchedUtil {
144 /// Constructs an empty (watches nothing) ChainWatchedUtil
145 pub fn new() -> Self {
148 watched_txn: HashSet::new(),
149 watched_outpoints: HashSet::new(),
153 /// Registers a tx for monitoring, returning true if it was a new tx and false if we'd already
154 /// been watching for it.
155 pub fn register_tx(&mut self, txid: &Txid, script_pub_key: &Script) -> bool {
156 if self.watch_all { return false; }
159 self.watched_txn.insert((txid.clone(), script_pub_key.clone()))
163 let _tx_unused = txid; // It's used in cfg(test), though
164 self.watched_txn.insert(script_pub_key.clone())
168 /// Registers an outpoint for monitoring, returning true if it was a new outpoint and false if
169 /// we'd already been watching for it
170 pub fn register_outpoint(&mut self, outpoint: (Txid, u32), _script_pub_key: &Script) -> bool {
171 if self.watch_all { return false; }
172 self.watched_outpoints.insert(outpoint)
175 /// Sets us to match all transactions, returning true if this is a new setting and false if
176 /// we'd already been set to match everything.
177 pub fn watch_all(&mut self) -> bool {
178 if self.watch_all { return false; }
179 self.watch_all = true;
183 /// Checks if a given transaction matches the current filter.
184 pub fn does_match_tx(&self, tx: &Transaction) -> bool {
188 for out in tx.output.iter() {
190 for &(ref txid, ref script) in self.watched_txn.iter() {
191 if *script == out.script_pubkey {
192 if tx.txid() == *txid {
198 for script in self.watched_txn.iter() {
199 if *script == out.script_pubkey {
204 for input in tx.input.iter() {
205 for outpoint in self.watched_outpoints.iter() {
206 let &(outpoint_hash, outpoint_index) = outpoint;
207 if outpoint_hash == input.previous_output.txid && outpoint_index == input.previous_output.vout {
216 /// BlockNotifierArc is useful when you need a BlockNotifier that points to ChainListeners with
217 /// static lifetimes, e.g. when you're using lightning-net-tokio (since tokio::spawn requires
218 /// parameters with static lifetimes). Other times you can afford a reference, which is more
219 /// efficient, in which case BlockNotifierRef is a more appropriate type. Defining these type
220 /// aliases prevents issues such as overly long function definitions.
221 pub type BlockNotifierArc<C> = Arc<BlockNotifier<'static, Arc<ChainListener>, C>>;
223 /// BlockNotifierRef is useful when you want a BlockNotifier that points to ChainListeners
224 /// with nonstatic lifetimes. This is useful for when static lifetimes are not needed. Nonstatic
225 /// lifetimes are more efficient but less flexible, and should be used by default unless static
226 /// lifetimes are required, e.g. when you're using lightning-net-tokio (since tokio::spawn
227 /// requires parameters with static lifetimes), in which case BlockNotifierArc is a more
228 /// appropriate type. Defining these type aliases for common usages prevents issues such as
229 /// overly long function definitions.
230 pub type BlockNotifierRef<'a, C> = BlockNotifier<'a, &'a ChainListener, C>;
232 /// Utility for notifying listeners about new blocks, and handling block rescans if new watch
233 /// data is registered.
235 /// Rather than using a plain BlockNotifier, it is preferable to use either a BlockNotifierArc
236 /// or a BlockNotifierRef for conciseness. See their documentation for more details, but essentially
237 /// you should default to using a BlockNotifierRef, and use a BlockNotifierArc instead when you
238 /// require ChainListeners with static lifetimes, such as when you're using lightning-net-tokio.
239 pub struct BlockNotifier<'a, CL: Deref<Target = ChainListener + 'a> + 'a, C: Deref> where C::Target: ChainWatchInterface {
240 listeners: Mutex<Vec<CL>>,
242 phantom: PhantomData<&'a ()>,
245 impl<'a, CL: Deref<Target = ChainListener + 'a> + 'a, C: Deref> BlockNotifier<'a, CL, C> where C::Target: ChainWatchInterface {
246 /// Constructs a new BlockNotifier without any listeners.
247 pub fn new(chain_monitor: C) -> BlockNotifier<'a, CL, C> {
249 listeners: Mutex::new(Vec::new()),
251 phantom: PhantomData,
255 /// Register the given listener to receive events.
256 pub fn register_listener(&self, listener: CL) {
257 let mut vec = self.listeners.lock().unwrap();
260 /// Unregister the given listener to no longer
263 /// If the same listener is registered multiple times, unregistering
264 /// will remove ALL occurrences of that listener. Comparison is done using
265 /// the pointer returned by the Deref trait implementation.
266 pub fn unregister_listener(&self, listener: CL) {
267 let mut vec = self.listeners.lock().unwrap();
268 // item is a ref to an abstract thing that dereferences to a ChainListener,
269 // so dereference it twice to get the ChainListener itself
270 vec.retain(|item | !ptr::eq(&(**item), &(*listener)));
273 /// Notify listeners that a block was connected given a full, unfiltered block.
275 /// Handles re-scanning the block and calling block_connected again if listeners register new
276 /// watch data during the callbacks for you (see ChainListener::block_connected for more info).
277 pub fn block_connected(&self, block: &Block, height: u32) {
278 let mut reentered = true;
280 let matched_indexes = self.chain_monitor.filter_block(block);
281 let mut matched_txn = Vec::new();
282 for index in matched_indexes.iter() {
283 matched_txn.push(&block.txdata[*index]);
285 reentered = self.block_connected_checked(&block.header, height, matched_txn.as_slice(), matched_indexes.as_slice());
289 /// Notify listeners that a block was connected, given pre-filtered list of transactions in the
290 /// block which matched the filter (probably using does_match_tx).
292 /// Returns true if notified listeners registered additional watch data (implying that the
293 /// block must be re-scanned and this function called again prior to further block_connected
294 /// calls, see ChainListener::block_connected for more info).
295 pub fn block_connected_checked(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[usize]) -> bool {
296 let last_seen = self.chain_monitor.reentered();
298 let listeners = self.listeners.lock().unwrap();
299 for listener in listeners.iter() {
300 listener.block_connected(header, height, txn_matched, indexes_of_txn_matched);
302 return last_seen != self.chain_monitor.reentered();
305 /// Notify listeners that a block was disconnected.
306 pub fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32) {
307 let listeners = self.listeners.lock().unwrap();
308 for listener in listeners.iter() {
309 listener.block_disconnected(&header, disconnected_height);
314 /// Utility to capture some common parts of ChainWatchInterface implementors.
316 /// Keeping a local copy of this in a ChainWatchInterface implementor is likely useful.
317 pub struct ChainWatchInterfaceUtil {
319 watched: Mutex<ChainWatchedUtil>,
320 reentered: AtomicUsize,
323 // We only expose PartialEq in test since its somewhat unclear exactly what it should do and we're
324 // only comparing a subset of fields (essentially just checking that the set of things we're
325 // watching is the same).
327 impl PartialEq for ChainWatchInterfaceUtil {
328 fn eq(&self, o: &Self) -> bool {
329 self.network == o.network &&
330 *self.watched.lock().unwrap() == *o.watched.lock().unwrap()
334 /// Register listener
335 impl ChainWatchInterface for ChainWatchInterfaceUtil {
336 fn install_watch_tx(&self, txid: &Txid, script_pub_key: &Script) {
337 let mut watched = self.watched.lock().unwrap();
338 if watched.register_tx(txid, script_pub_key) {
339 self.reentered.fetch_add(1, Ordering::Relaxed);
343 fn install_watch_outpoint(&self, outpoint: (Txid, u32), out_script: &Script) {
344 let mut watched = self.watched.lock().unwrap();
345 if watched.register_outpoint(outpoint, out_script) {
346 self.reentered.fetch_add(1, Ordering::Relaxed);
350 fn watch_all_txn(&self) {
351 let mut watched = self.watched.lock().unwrap();
352 if watched.watch_all() {
353 self.reentered.fetch_add(1, Ordering::Relaxed);
357 fn get_chain_utxo(&self, genesis_hash: BlockHash, _unspent_tx_output_identifier: u64) -> Result<(Script, u64), ChainError> {
358 if genesis_hash != genesis_block(self.network).header.bitcoin_hash() {
359 return Err(ChainError::NotWatched);
361 Err(ChainError::NotSupported)
364 fn filter_block(&self, block: &Block) -> Vec<usize> {
365 let mut matched_index = Vec::new();
367 let watched = self.watched.lock().unwrap();
368 for (index, transaction) in block.txdata.iter().enumerate() {
369 if self.does_match_tx_unguarded(transaction, &watched) {
370 matched_index.push(index);
377 fn reentered(&self) -> usize {
378 self.reentered.load(Ordering::Relaxed)
382 impl ChainWatchInterfaceUtil {
383 /// Creates a new ChainWatchInterfaceUtil for the given network
384 pub fn new(network: Network) -> ChainWatchInterfaceUtil {
385 ChainWatchInterfaceUtil {
387 watched: Mutex::new(ChainWatchedUtil::new()),
388 reentered: AtomicUsize::new(1),
392 /// Checks if a given transaction matches the current filter.
393 pub fn does_match_tx(&self, tx: &Transaction) -> bool {
394 let watched = self.watched.lock().unwrap();
395 self.does_match_tx_unguarded (tx, &watched)
398 fn does_match_tx_unguarded(&self, tx: &Transaction, watched: &MutexGuard<ChainWatchedUtil>) -> bool {
399 watched.does_match_tx(tx)
405 use ln::functional_test_utils::{create_chanmon_cfgs, create_node_cfgs};
406 use super::{BlockNotifier, ChainListener};
410 fn register_listener_test() {
411 let chanmon_cfgs = create_chanmon_cfgs(1);
412 let node_cfgs = create_node_cfgs(1, &chanmon_cfgs);
413 let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor);
414 assert_eq!(block_notifier.listeners.lock().unwrap().len(), 0);
415 let listener = &node_cfgs[0].chan_monitor.simple_monitor as &ChainListener;
416 block_notifier.register_listener(listener);
417 let vec = block_notifier.listeners.lock().unwrap();
418 assert_eq!(vec.len(), 1);
419 let item = vec.first().clone().unwrap();
420 assert!(ptr::eq(&(**item), &(*listener)));
424 fn unregister_single_listener_test() {
425 let chanmon_cfgs = create_chanmon_cfgs(2);
426 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
427 let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor);
428 let listener1 = &node_cfgs[0].chan_monitor.simple_monitor as &ChainListener;
429 let listener2 = &node_cfgs[1].chan_monitor.simple_monitor as &ChainListener;
430 block_notifier.register_listener(listener1);
431 block_notifier.register_listener(listener2);
432 let vec = block_notifier.listeners.lock().unwrap();
433 assert_eq!(vec.len(), 2);
435 block_notifier.unregister_listener(listener1);
436 let vec = block_notifier.listeners.lock().unwrap();
437 assert_eq!(vec.len(), 1);
438 let item = vec.first().clone().unwrap();
439 assert!(ptr::eq(&(**item), &(*listener2)));
443 fn unregister_single_listener_ref_test() {
444 let chanmon_cfgs = create_chanmon_cfgs(2);
445 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
446 let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor);
447 block_notifier.register_listener(&node_cfgs[0].chan_monitor.simple_monitor as &ChainListener);
448 block_notifier.register_listener(&node_cfgs[1].chan_monitor.simple_monitor as &ChainListener);
449 let vec = block_notifier.listeners.lock().unwrap();
450 assert_eq!(vec.len(), 2);
452 block_notifier.unregister_listener(&node_cfgs[0].chan_monitor.simple_monitor);
453 let vec = block_notifier.listeners.lock().unwrap();
454 assert_eq!(vec.len(), 1);
455 let item = vec.first().clone().unwrap();
456 assert!(ptr::eq(&(**item), &(*&node_cfgs[1].chan_monitor.simple_monitor)));
460 fn unregister_multiple_of_the_same_listeners_test() {
461 let chanmon_cfgs = create_chanmon_cfgs(2);
462 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
463 let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor);
464 let listener1 = &node_cfgs[0].chan_monitor.simple_monitor as &ChainListener;
465 let listener2 = &node_cfgs[1].chan_monitor.simple_monitor as &ChainListener;
466 block_notifier.register_listener(listener1);
467 block_notifier.register_listener(listener1);
468 block_notifier.register_listener(listener2);
469 let vec = block_notifier.listeners.lock().unwrap();
470 assert_eq!(vec.len(), 3);
472 block_notifier.unregister_listener(listener1);
473 let vec = block_notifier.listeners.lock().unwrap();
474 assert_eq!(vec.len(), 1);
475 let item = vec.first().clone().unwrap();
476 assert!(ptr::eq(&(**item), &(*listener2)));