chainmonitor.rs

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! Logic to connect off-chain channel management with on-chain transaction monitoring.
//!
//! [`ChainMonitor`] is an implementation of [`chain::Watch`] used both to process blocks and to
//! update [`ChannelMonitor`]s accordingly. If any on-chain events need further processing, it will
//! make those available as [`MonitorEvent`]s to be consumed.
//!
//! [`ChainMonitor`] is parameterized by an optional chain source, which must implement the
//! [`chain::Filter`] trait. This provides a mechanism to signal new relevant outputs back to light
//! clients, such that transactions spending those outputs are included in block data.
//!
//! [`ChainMonitor`] may be used directly to monitor channels locally or as a part of a distributed
//! setup to monitor channels remotely. In the latter case, a custom [`chain::Watch`] implementation
//! would be responsible for routing each update to a remote server and for retrieving monitor
//! events. The remote server would make use of [`ChainMonitor`] for block processing and for
//! servicing [`ChannelMonitor`] updates from the client.

use bitcoin::blockdata::block::BlockHeader;
use bitcoin::hash_types::Txid;

use chain;
use chain::{ChannelMonitorUpdateErr, Filter, WatchedOutput};
use chain::chaininterface::{BroadcasterInterface, FeeEstimator};
use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, Balance, MonitorEvent, TransactionOutputs, LATENCY_GRACE_PERIOD_BLOCKS};
use chain::transaction::{OutPoint, TransactionData};
use chain::keysinterface::Sign;
use util::atomic_counter::AtomicCounter;
use util::logger::Logger;
use util::errors::APIError;
use util::events;
use util::events::EventHandler;
use ln::channelmanager::ChannelDetails;

use prelude::*;
use sync::{RwLock, RwLockReadGuard, Mutex, MutexGuard};
use core::ops::Deref;
use core::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
use bitcoin::secp256k1::PublicKey;

#[derive(Clone, Copy, Hash, PartialEq, Eq)]
/// A specific update's ID stored in a `MonitorUpdateId`, separated out to make the contents
/// entirely opaque.
enum UpdateOrigin {
	/// An update that was generated by the `ChannelManager` (via our `chain::Watch`
	/// implementation). This corresponds to an actual [`ChannelMonitorUpdate::update_id`] field
	/// and [`ChannelMonitor::get_latest_update_id`].
	OffChain(u64),
	/// An update that was generated during blockchain processing. The ID here is specific to the
	/// generating [`ChainMonitor`] and does *not* correspond to any on-disk IDs.
	ChainSync(u64),
}

/// An opaque identifier describing a specific [`Persist`] method call.
#[derive(Clone, Copy, Hash, PartialEq, Eq)]
pub struct MonitorUpdateId {
	contents: UpdateOrigin,
}

impl MonitorUpdateId {
	pub(crate) fn from_monitor_update(update: &ChannelMonitorUpdate) -> Self {
		Self { contents: UpdateOrigin::OffChain(update.update_id) }
	}
	pub(crate) fn from_new_monitor<ChannelSigner: Sign>(monitor: &ChannelMonitor<ChannelSigner>) -> Self {
		Self { contents: UpdateOrigin::OffChain(monitor.get_latest_update_id()) }
	}
}

/// `Persist` defines behavior for persisting channel monitors: this could mean
/// writing once to disk, and/or uploading to one or more backup services.
///
/// Each method can return three possible values:
///  * If persistence (including any relevant `fsync()` calls) happens immediately, the
///    implementation should return `Ok(())`, indicating normal channel operation should continue.
///  * If persistence happens asynchronously, implementations should first ensure the
///    [`ChannelMonitor`] or [`ChannelMonitorUpdate`] are written durably to disk, and then return
///    `Err(ChannelMonitorUpdateErr::TemporaryFailure)` while the update continues in the
///    background. Once the update completes, [`ChainMonitor::channel_monitor_updated`] should be
///    called with the corresponding [`MonitorUpdateId`].
///
///    Note that unlike the direct [`chain::Watch`] interface,
///    [`ChainMonitor::channel_monitor_updated`] must be called once for *each* update which occurs.
///
///  * If persistence fails for some reason, implementations should return
///    `Err(ChannelMonitorUpdateErr::PermanentFailure)`, in which case the channel will likely be
///    closed without broadcasting the latest state. See
///    [`ChannelMonitorUpdateErr::PermanentFailure`] for more details.
pub trait Persist<ChannelSigner: Sign> {
	/// Persist a new channel's data in response to a [`chain::Watch::watch_channel`] call. This is
	/// called by [`ChannelManager`] for new channels, or may be called directly, e.g. on startup.
	///
	/// The data can be stored any way you want, but the identifier provided by LDK is the
	/// channel's outpoint (and it is up to you to maintain a correct mapping between the outpoint
	/// and the stored channel data). Note that you **must** persist every new monitor to disk.
	///
	/// The `update_id` is used to identify this call to [`ChainMonitor::channel_monitor_updated`],
	/// if you return [`ChannelMonitorUpdateErr::TemporaryFailure`].
	///
	/// See [`Writeable::write`] on [`ChannelMonitor`] for writing out a `ChannelMonitor`
	/// and [`ChannelMonitorUpdateErr`] for requirements when returning errors.
	///
	/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
	/// [`Writeable::write`]: crate::util::ser::Writeable::write
	fn persist_new_channel(&self, channel_id: OutPoint, data: &ChannelMonitor<ChannelSigner>, update_id: MonitorUpdateId) -> Result<(), ChannelMonitorUpdateErr>;

	/// Update one channel's data. The provided [`ChannelMonitor`] has already applied the given
	/// update.
	///
	/// Note that on every update, you **must** persist either the [`ChannelMonitorUpdate`] or the
	/// updated monitor itself to disk/backups. See the [`Persist`] trait documentation for more
	/// details.
	///
	/// During blockchain synchronization operations, this may be called with no
	/// [`ChannelMonitorUpdate`], in which case the full [`ChannelMonitor`] needs to be persisted.
	/// Note that after the full [`ChannelMonitor`] is persisted any previous
	/// [`ChannelMonitorUpdate`]s which were persisted should be discarded - they can no longer be
	/// applied to the persisted [`ChannelMonitor`] as they were already applied.
	///
	/// If an implementer chooses to persist the updates only, they need to make
	/// sure that all the updates are applied to the `ChannelMonitors` *before*
	/// the set of channel monitors is given to the `ChannelManager`
	/// deserialization routine. See [`ChannelMonitor::update_monitor`] for
	/// applying a monitor update to a monitor. If full `ChannelMonitors` are
	/// persisted, then there is no need to persist individual updates.
	///
	/// Note that there could be a performance tradeoff between persisting complete
	/// channel monitors on every update vs. persisting only updates and applying
	/// them in batches. The size of each monitor grows `O(number of state updates)`
	/// whereas updates are small and `O(1)`.
	///
	/// The `update_id` is used to identify this call to [`ChainMonitor::channel_monitor_updated`],
	/// if you return [`ChannelMonitorUpdateErr::TemporaryFailure`].
	///
	/// See [`Writeable::write`] on [`ChannelMonitor`] for writing out a `ChannelMonitor`,
	/// [`Writeable::write`] on [`ChannelMonitorUpdate`] for writing out an update, and
	/// [`ChannelMonitorUpdateErr`] for requirements when returning errors.
	///
	/// [`Writeable::write`]: crate::util::ser::Writeable::write
	fn update_persisted_channel(&self, channel_id: OutPoint, update: &Option<ChannelMonitorUpdate>, data: &ChannelMonitor<ChannelSigner>, update_id: MonitorUpdateId) -> Result<(), ChannelMonitorUpdateErr>;
}

struct MonitorHolder<ChannelSigner: Sign> {
	monitor: ChannelMonitor<ChannelSigner>,
	/// The full set of pending monitor updates for this Channel.
	///
	/// Note that this lock must be held during updates to prevent a race where we call
	/// update_persisted_channel, the user returns a TemporaryFailure, and then calls
	/// channel_monitor_updated immediately, racing our insertion of the pending update into the
	/// contained Vec.
	///
	/// Beyond the synchronization of updates themselves, we cannot handle user events until after
	/// any chain updates have been stored on disk. Thus, we scan this list when returning updates
	/// to the ChannelManager, refusing to return any updates for a ChannelMonitor which is still
	/// being persisted fully to disk after a chain update.
	///
	/// This avoids the possibility of handling, e.g. an on-chain claim, generating a claim monitor
	/// event, resulting in the relevant ChannelManager generating a PaymentSent event and dropping
	/// the pending payment entry, and then reloading before the monitor is persisted, resulting in
	/// the ChannelManager re-adding the same payment entry, before the same block is replayed,
	/// resulting in a duplicate PaymentSent event.
	pending_monitor_updates: Mutex<Vec<MonitorUpdateId>>,
	/// When the user returns a PermanentFailure error from an update_persisted_channel call during
	/// block processing, we inform the ChannelManager that the channel should be closed
	/// asynchronously. In order to ensure no further changes happen before the ChannelManager has
	/// processed the closure event, we set this to true and return PermanentFailure for any other
	/// chain::Watch events.
	channel_perm_failed: AtomicBool,
	/// The last block height at which no [`UpdateOrigin::ChainSync`] monitor updates were present
	/// in `pending_monitor_updates`.
	/// If it's been more than [`LATENCY_GRACE_PERIOD_BLOCKS`] since we started waiting on a chain
	/// sync event, we let monitor events return to `ChannelManager` because we cannot hold them up
	/// forever or we'll end up with HTLC preimages waiting to feed back into an upstream channel
	/// forever, risking funds loss.
	last_chain_persist_height: AtomicUsize,
}

impl<ChannelSigner: Sign> MonitorHolder<ChannelSigner> {
	fn has_pending_offchain_updates(&self, pending_monitor_updates_lock: &MutexGuard<Vec<MonitorUpdateId>>) -> bool {
		pending_monitor_updates_lock.iter().any(|update_id|
			if let UpdateOrigin::OffChain(_) = update_id.contents { true } else { false })
	}
	fn has_pending_chainsync_updates(&self, pending_monitor_updates_lock: &MutexGuard<Vec<MonitorUpdateId>>) -> bool {
		pending_monitor_updates_lock.iter().any(|update_id|
			if let UpdateOrigin::ChainSync(_) = update_id.contents { true } else { false })
	}
}

/// A read-only reference to a current ChannelMonitor.
///
/// Note that this holds a mutex in [`ChainMonitor`] and may block other events until it is
/// released.
pub struct LockedChannelMonitor<'a, ChannelSigner: Sign> {
	lock: RwLockReadGuard<'a, HashMap<OutPoint, MonitorHolder<ChannelSigner>>>,
	funding_txo: OutPoint,
}

impl<ChannelSigner: Sign> Deref for LockedChannelMonitor<'_, ChannelSigner> {
	type Target = ChannelMonitor<ChannelSigner>;
	fn deref(&self) -> &ChannelMonitor<ChannelSigner> {
		&self.lock.get(&self.funding_txo).expect("Checked at construction").monitor
	}
}

/// An implementation of [`chain::Watch`] for monitoring channels.
///
/// Connected and disconnected blocks must be provided to `ChainMonitor` as documented by
/// [`chain::Watch`]. May be used in conjunction with [`ChannelManager`] to monitor channels locally
/// or used independently to monitor channels remotely. See the [module-level documentation] for
/// details.
///
/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
/// [module-level documentation]: crate::chain::chainmonitor
pub struct ChainMonitor<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
	where C::Target: chain::Filter,
        T::Target: BroadcasterInterface,
        F::Target: FeeEstimator,
        L::Target: Logger,
        P::Target: Persist<ChannelSigner>,
{
	monitors: RwLock<HashMap<OutPoint, MonitorHolder<ChannelSigner>>>,
	/// When we generate a [`MonitorUpdateId`] for a chain-event monitor persistence, we need a
	/// unique ID, which we calculate by simply getting the next value from this counter. Note that
	/// the ID is never persisted so it's ok that they reset on restart.
	sync_persistence_id: AtomicCounter,
	chain_source: Option<C>,
	broadcaster: T,
	logger: L,
	fee_estimator: F,
	persister: P,
	/// "User-provided" (ie persistence-completion/-failed) [`MonitorEvent`]s. These came directly
	/// from the user and not from a [`ChannelMonitor`].
	pending_monitor_events: Mutex<Vec<(OutPoint, Vec<MonitorEvent>, Option<PublicKey>)>>,
	/// The best block height seen, used as a proxy for the passage of time.
	highest_chain_height: AtomicUsize,
}

impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> ChainMonitor<ChannelSigner, C, T, F, L, P>
where C::Target: chain::Filter,
	    T::Target: BroadcasterInterface,
	    F::Target: FeeEstimator,
	    L::Target: Logger,
	    P::Target: Persist<ChannelSigner>,
{
	/// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
	/// of a channel and reacting accordingly based on transactions in the given chain data. See
	/// [`ChannelMonitor::block_connected`] for details. Any HTLCs that were resolved on chain will
	/// be returned by [`chain::Watch::release_pending_monitor_events`].
	///
	/// Calls back to [`chain::Filter`] if any monitor indicated new outputs to watch. Subsequent
	/// calls must not exclude any transactions matching the new outputs nor any in-block
	/// descendants of such transactions. It is not necessary to re-fetch the block to obtain
	/// updated `txdata`.
	///
	/// Calls which represent a new blockchain tip height should set `best_height`.
	fn process_chain_data<FN>(&self, header: &BlockHeader, best_height: Option<u32>, txdata: &TransactionData, process: FN)
	where
		FN: Fn(&ChannelMonitor<ChannelSigner>, &TransactionData) -> Vec<TransactionOutputs>
	{
		let mut dependent_txdata = Vec::new();
		{
			let monitor_states = self.monitors.write().unwrap();
			if let Some(height) = best_height {
				// If the best block height is being updated, update highest_chain_height under the
				// monitors write lock.
				let old_height = self.highest_chain_height.load(Ordering::Acquire);
				let new_height = height as usize;
				if new_height > old_height {
					self.highest_chain_height.store(new_height, Ordering::Release);
				}
			}

			for (funding_outpoint, monitor_state) in monitor_states.iter() {
				let monitor = &monitor_state.monitor;
				let mut txn_outputs;
				{
					txn_outputs = process(monitor, txdata);
					let update_id = MonitorUpdateId {
						contents: UpdateOrigin::ChainSync(self.sync_persistence_id.get_increment()),
					};
					let mut pending_monitor_updates = monitor_state.pending_monitor_updates.lock().unwrap();
					if let Some(height) = best_height {
						if !monitor_state.has_pending_chainsync_updates(&pending_monitor_updates) {
							// If there are not ChainSync persists awaiting completion, go ahead and
							// set last_chain_persist_height here - we wouldn't want the first
							// TemporaryFailure to always immediately be considered "overly delayed".
							monitor_state.last_chain_persist_height.store(height as usize, Ordering::Release);
						}
					}

					log_trace!(self.logger, "Syncing Channel Monitor for channel {}", log_funding_info!(monitor));
					match self.persister.update_persisted_channel(*funding_outpoint, &None, monitor, update_id) {
						Ok(()) =>
							log_trace!(self.logger, "Finished syncing Channel Monitor for channel {}", log_funding_info!(monitor)),
						Err(ChannelMonitorUpdateErr::PermanentFailure) => {
							monitor_state.channel_perm_failed.store(true, Ordering::Release);
							self.pending_monitor_events.lock().unwrap().push((*funding_outpoint, vec![MonitorEvent::UpdateFailed(*funding_outpoint)], monitor.get_counterparty_node_id()));
						},
						Err(ChannelMonitorUpdateErr::TemporaryFailure) => {
							log_debug!(self.logger, "Channel Monitor sync for channel {} in progress, holding events until completion!", log_funding_info!(monitor));
							pending_monitor_updates.push(update_id);
						},
					}
				}

				// Register any new outputs with the chain source for filtering, storing any dependent
				// transactions from within the block that previously had not been included in txdata.
				if let Some(ref chain_source) = self.chain_source {
					let block_hash = header.block_hash();
					for (txid, mut outputs) in txn_outputs.drain(..) {
						for (idx, output) in outputs.drain(..) {
							// Register any new outputs with the chain source for filtering and recurse
							// if it indicates that there are dependent transactions within the block
							// that had not been previously included in txdata.
							let output = WatchedOutput {
								block_hash: Some(block_hash),
								outpoint: OutPoint { txid, index: idx as u16 },
								script_pubkey: output.script_pubkey,
							};
							if let Some(tx) = chain_source.register_output(output) {
								dependent_txdata.push(tx);
							}
						}
					}
				}
			}
		}

		// Recursively call for any dependent transactions that were identified by the chain source.
		if !dependent_txdata.is_empty() {
			dependent_txdata.sort_unstable_by_key(|(index, _tx)| *index);
			dependent_txdata.dedup_by_key(|(index, _tx)| *index);
			let txdata: Vec<_> = dependent_txdata.iter().map(|(index, tx)| (*index, tx)).collect();
			self.process_chain_data(header, None, &txdata, process); // We skip the best height the second go-around
		}
	}

	/// Creates a new `ChainMonitor` used to watch on-chain activity pertaining to channels.
	///
	/// When an optional chain source implementing [`chain::Filter`] is provided, the chain monitor
	/// will call back to it indicating transactions and outputs of interest. This allows clients to
	/// pre-filter blocks or only fetch blocks matching a compact filter. Otherwise, clients may
	/// always need to fetch full blocks absent another means for determining which blocks contain
	/// transactions relevant to the watched channels.
	pub fn new(chain_source: Option<C>, broadcaster: T, logger: L, feeest: F, persister: P) -> Self {
		Self {
			monitors: RwLock::new(HashMap::new()),
			sync_persistence_id: AtomicCounter::new(),
			chain_source,
			broadcaster,
			logger,
			fee_estimator: feeest,
			persister,
			pending_monitor_events: Mutex::new(Vec::new()),
			highest_chain_height: AtomicUsize::new(0),
		}
	}

	/// Gets the balances in the contained [`ChannelMonitor`]s which are claimable on-chain or
	/// claims which are awaiting confirmation.
	///
	/// Includes the balances from each [`ChannelMonitor`] *except* those included in
	/// `ignored_channels`, allowing you to filter out balances from channels which are still open
	/// (and whose balance should likely be pulled from the [`ChannelDetails`]).
	///
	/// See [`ChannelMonitor::get_claimable_balances`] for more details on the exact criteria for
	/// inclusion in the return value.
	pub fn get_claimable_balances(&self, ignored_channels: &[&ChannelDetails]) -> Vec<Balance> {
		let mut ret = Vec::new();
		let monitor_states = self.monitors.read().unwrap();
		for (_, monitor_state) in monitor_states.iter().filter(|(funding_outpoint, _)| {
			for chan in ignored_channels {
				if chan.funding_txo.as_ref() == Some(funding_outpoint) {
					return false;
				}
			}
			true
		}) {
			ret.append(&mut monitor_state.monitor.get_claimable_balances());
		}
		ret
	}

	/// Gets the [`LockedChannelMonitor`] for a given funding outpoint, returning an `Err` if no
	/// such [`ChannelMonitor`] is currently being monitored for.
	///
	/// Note that the result holds a mutex over our monitor set, and should not be held
	/// indefinitely.
	pub fn get_monitor(&self, funding_txo: OutPoint) -> Result<LockedChannelMonitor<'_, ChannelSigner>, ()> {
		let lock = self.monitors.read().unwrap();
		if lock.get(&funding_txo).is_some() {
			Ok(LockedChannelMonitor { lock, funding_txo })
		} else {
			Err(())
		}
	}

	/// Lists the funding outpoint of each [`ChannelMonitor`] being monitored.
	///
	/// Note that [`ChannelMonitor`]s are not removed when a channel is closed as they are always
	/// monitoring for on-chain state resolutions.
	pub fn list_monitors(&self) -> Vec<OutPoint> {
		self.monitors.read().unwrap().keys().map(|outpoint| *outpoint).collect()
	}

	#[cfg(test)]
	pub fn remove_monitor(&self, funding_txo: &OutPoint) -> ChannelMonitor<ChannelSigner> {
		self.monitors.write().unwrap().remove(funding_txo).unwrap().monitor
	}

	/// Indicates the persistence of a [`ChannelMonitor`] has completed after
	/// [`ChannelMonitorUpdateErr::TemporaryFailure`] was returned from an update operation.
	///
	/// Thus, the anticipated use is, at a high level:
	///  1) This [`ChainMonitor`] calls [`Persist::update_persisted_channel`] which stores the
	///     update to disk and begins updating any remote (e.g. watchtower/backup) copies,
	///     returning [`ChannelMonitorUpdateErr::TemporaryFailure`],
	///  2) once all remote copies are updated, you call this function with the
	///     `completed_update_id` that completed, and once all pending updates have completed the
	///     channel will be re-enabled.
	//      Note that we re-enable only after `UpdateOrigin::OffChain` updates complete, we don't
	//      care about `UpdateOrigin::ChainSync` updates for the channel state being updated. We
	//      only care about `UpdateOrigin::ChainSync` for returning `MonitorEvent`s.
	///
	/// Returns an [`APIError::APIMisuseError`] if `funding_txo` does not match any currently
	/// registered [`ChannelMonitor`]s.
	pub fn channel_monitor_updated(&self, funding_txo: OutPoint, completed_update_id: MonitorUpdateId) -> Result<(), APIError> {
		let monitors = self.monitors.read().unwrap();
		let monitor_data = if let Some(mon) = monitors.get(&funding_txo) { mon } else {
			return Err(APIError::APIMisuseError { err: format!("No ChannelMonitor matching funding outpoint {:?} found", funding_txo) });
		};
		let mut pending_monitor_updates = monitor_data.pending_monitor_updates.lock().unwrap();
		pending_monitor_updates.retain(|update_id| *update_id != completed_update_id);

		match completed_update_id {
			MonitorUpdateId { contents: UpdateOrigin::OffChain(_) } => {
				// Note that we only check for `UpdateOrigin::OffChain` failures here - if
				// we're being told that a `UpdateOrigin::OffChain` monitor update completed,
				// we only care about ensuring we don't tell the `ChannelManager` to restore
				// the channel to normal operation until all `UpdateOrigin::OffChain` updates
				// complete.
				// If there's some `UpdateOrigin::ChainSync` update still pending that's okay
				// - we can still update our channel state, just as long as we don't return
				// `MonitorEvent`s from the monitor back to the `ChannelManager` until they
				// complete.
				let monitor_is_pending_updates = monitor_data.has_pending_offchain_updates(&pending_monitor_updates);
				if monitor_is_pending_updates || monitor_data.channel_perm_failed.load(Ordering::Acquire) {
					// If there are still monitor updates pending (or an old monitor update
					// finished after a later one perm-failed), we cannot yet construct an
					// UpdateCompleted event.
					return Ok(());
				}
				self.pending_monitor_events.lock().unwrap().push((funding_txo, vec![MonitorEvent::UpdateCompleted {
					funding_txo,
					monitor_update_id: monitor_data.monitor.get_latest_update_id(),
				}], monitor_data.monitor.get_counterparty_node_id()));
			},
			MonitorUpdateId { contents: UpdateOrigin::ChainSync(_) } => {
				if !monitor_data.has_pending_chainsync_updates(&pending_monitor_updates) {
					monitor_data.last_chain_persist_height.store(self.highest_chain_height.load(Ordering::Acquire), Ordering::Release);
					// The next time release_pending_monitor_events is called, any events for this
					// ChannelMonitor will be returned.
				}
			},
		}
		Ok(())
	}

	/// This wrapper avoids having to update some of our tests for now as they assume the direct
	/// chain::Watch API wherein we mark a monitor fully-updated by just calling
	/// channel_monitor_updated once with the highest ID.
	#[cfg(any(test, fuzzing))]
	pub fn force_channel_monitor_updated(&self, funding_txo: OutPoint, monitor_update_id: u64) {
		let monitors = self.monitors.read().unwrap();
		let counterparty_node_id = if let Some(mon) = monitors.get(&funding_txo) { mon.monitor.get_counterparty_node_id() } else { None };
		self.pending_monitor_events.lock().unwrap().push((funding_txo, vec![MonitorEvent::UpdateCompleted {
			funding_txo,
			monitor_update_id,
		}], counterparty_node_id));
	}

	#[cfg(any(test, fuzzing, feature = "_test_utils"))]
	pub fn get_and_clear_pending_events(&self) -> Vec<events::Event> {
		use util::events::EventsProvider;
		let events = core::cell::RefCell::new(Vec::new());
		let event_handler = |event: &events::Event| events.borrow_mut().push(event.clone());
		self.process_pending_events(&event_handler);
		events.into_inner()
	}
}

impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
where
	C::Target: chain::Filter,
	T::Target: BroadcasterInterface,
	F::Target: FeeEstimator,
	L::Target: Logger,
	P::Target: Persist<ChannelSigner>,
{
	fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
		log_debug!(self.logger, "New best block {} at height {} provided via block_connected", header.block_hash(), height);
		self.process_chain_data(header, Some(height), &txdata, |monitor, txdata| {
			monitor.block_connected(
				header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
		});
	}

	fn block_disconnected(&self, header: &BlockHeader, height: u32) {
		let monitor_states = self.monitors.read().unwrap();
		log_debug!(self.logger, "Latest block {} at height {} removed via block_disconnected", header.block_hash(), height);
		for monitor_state in monitor_states.values() {
			monitor_state.monitor.block_disconnected(
				header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
		}
	}
}

impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
chain::Confirm for ChainMonitor<ChannelSigner, C, T, F, L, P>
where
	C::Target: chain::Filter,
	T::Target: BroadcasterInterface,
	F::Target: FeeEstimator,
	L::Target: Logger,
	P::Target: Persist<ChannelSigner>,
{
	fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
		log_debug!(self.logger, "{} provided transactions confirmed at height {} in block {}", txdata.len(), height, header.block_hash());
		self.process_chain_data(header, None, txdata, |monitor, txdata| {
			monitor.transactions_confirmed(
				header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
		});
	}

	fn transaction_unconfirmed(&self, txid: &Txid) {
		log_debug!(self.logger, "Transaction {} reorganized out of chain", txid);
		let monitor_states = self.monitors.read().unwrap();
		for monitor_state in monitor_states.values() {
			monitor_state.monitor.transaction_unconfirmed(txid, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
		}
	}

	fn best_block_updated(&self, header: &BlockHeader, height: u32) {
		log_debug!(self.logger, "New best block {} at height {} provided via best_block_updated", header.block_hash(), height);
		self.process_chain_data(header, Some(height), &[], |monitor, txdata| {
			// While in practice there shouldn't be any recursive calls when given empty txdata,
			// it's still possible if a chain::Filter implementation returns a transaction.
			debug_assert!(txdata.is_empty());
			monitor.best_block_updated(
				header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
		});
	}

	fn get_relevant_txids(&self) -> Vec<Txid> {
		let mut txids = Vec::new();
		let monitor_states = self.monitors.read().unwrap();
		for monitor_state in monitor_states.values() {
			txids.append(&mut monitor_state.monitor.get_relevant_txids());
		}

		txids.sort_unstable();
		txids.dedup();
		txids
	}
}

impl<ChannelSigner: Sign, C: Deref , T: Deref , F: Deref , L: Deref , P: Deref >
chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
where C::Target: chain::Filter,
	    T::Target: BroadcasterInterface,
	    F::Target: FeeEstimator,
	    L::Target: Logger,
	    P::Target: Persist<ChannelSigner>,
{
	/// Adds the monitor that watches the channel referred to by the given outpoint.
	///
	/// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
	///
	/// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
	/// monitors lock.
	fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
		let mut monitors = self.monitors.write().unwrap();
		let entry = match monitors.entry(funding_outpoint) {
			hash_map::Entry::Occupied(_) => {
				log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
				return Err(ChannelMonitorUpdateErr::PermanentFailure)},
			hash_map::Entry::Vacant(e) => e,
		};
		log_trace!(self.logger, "Got new ChannelMonitor for channel {}", log_funding_info!(monitor));
		let update_id = MonitorUpdateId::from_new_monitor(&monitor);
		let mut pending_monitor_updates = Vec::new();
		let persist_res = self.persister.persist_new_channel(funding_outpoint, &monitor, update_id);
		if persist_res.is_err() {
			log_error!(self.logger, "Failed to persist new ChannelMonitor for channel {}: {:?}", log_funding_info!(monitor), persist_res);
		} else {
			log_trace!(self.logger, "Finished persisting new ChannelMonitor for channel {}", log_funding_info!(monitor));
		}
		if persist_res == Err(ChannelMonitorUpdateErr::PermanentFailure) {
			return persist_res;
		} else if persist_res.is_err() {
			pending_monitor_updates.push(update_id);
		}
		if let Some(ref chain_source) = self.chain_source {
			monitor.load_outputs_to_watch(chain_source);
		}
		entry.insert(MonitorHolder {
			monitor,
			pending_monitor_updates: Mutex::new(pending_monitor_updates),
			channel_perm_failed: AtomicBool::new(false),
			last_chain_persist_height: AtomicUsize::new(self.highest_chain_height.load(Ordering::Acquire)),
		});
		persist_res
	}

	/// Note that we persist the given `ChannelMonitor` update while holding the
	/// `ChainMonitor` monitors lock.
	fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
		// Update the monitor that watches the channel referred to by the given outpoint.
		let monitors = self.monitors.read().unwrap();
		match monitors.get(&funding_txo) {
			None => {
				log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");

				// We should never ever trigger this from within ChannelManager. Technically a
				// user could use this object with some proxying in between which makes this
				// possible, but in tests and fuzzing, this should be a panic.
				#[cfg(any(test, fuzzing))]
				panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
				#[cfg(not(any(test, fuzzing)))]
				Err(ChannelMonitorUpdateErr::PermanentFailure)
			},
			Some(monitor_state) => {
				let monitor = &monitor_state.monitor;
				log_trace!(self.logger, "Updating ChannelMonitor for channel {}", log_funding_info!(monitor));
				let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
				if update_res.is_err() {
					log_error!(self.logger, "Failed to update ChannelMonitor for channel {}.", log_funding_info!(monitor));
				}
				// Even if updating the monitor returns an error, the monitor's state will
				// still be changed. So, persist the updated monitor despite the error.
				let update_id = MonitorUpdateId::from_monitor_update(&update);
				let mut pending_monitor_updates = monitor_state.pending_monitor_updates.lock().unwrap();
				let persist_res = self.persister.update_persisted_channel(funding_txo, &Some(update), monitor, update_id);
				if let Err(e) = persist_res {
					if e == ChannelMonitorUpdateErr::TemporaryFailure {
						pending_monitor_updates.push(update_id);
					} else {
						monitor_state.channel_perm_failed.store(true, Ordering::Release);
					}
					log_error!(self.logger, "Failed to persist ChannelMonitor update for channel {}: {:?}", log_funding_info!(monitor), e);
				} else {
					log_trace!(self.logger, "Finished persisting ChannelMonitor update for channel {}", log_funding_info!(monitor));
				}
				if update_res.is_err() {
					Err(ChannelMonitorUpdateErr::PermanentFailure)
				} else if monitor_state.channel_perm_failed.load(Ordering::Acquire) {
					Err(ChannelMonitorUpdateErr::PermanentFailure)
				} else {
					persist_res
				}
			}
		}
	}

	fn release_pending_monitor_events(&self) -> Vec<(OutPoint, Vec<MonitorEvent>, Option<PublicKey>)> {
		let mut pending_monitor_events = self.pending_monitor_events.lock().unwrap().split_off(0);
		for monitor_state in self.monitors.read().unwrap().values() {
			let is_pending_monitor_update = monitor_state.has_pending_chainsync_updates(&monitor_state.pending_monitor_updates.lock().unwrap());
			if is_pending_monitor_update &&
					monitor_state.last_chain_persist_height.load(Ordering::Acquire) + LATENCY_GRACE_PERIOD_BLOCKS as usize
						> self.highest_chain_height.load(Ordering::Acquire)
			{
				log_info!(self.logger, "A Channel Monitor sync is still in progress, refusing to provide monitor events!");
			} else {
				if monitor_state.channel_perm_failed.load(Ordering::Acquire) {
					// If a `UpdateOrigin::ChainSync` persistence failed with `PermanantFailure`,
					// we don't really know if the latest `ChannelMonitor` state is on disk or not.
					// We're supposed to hold monitor updates until the latest state is on disk to
					// avoid duplicate events, but the user told us persistence is screw-y and may
					// not complete. We can't hold events forever because we may learn some payment
					// preimage, so instead we just log and hope the user complied with the
					// `PermanentFailure` requirements of having at least the local-disk copy
					// updated.
					log_info!(self.logger, "A Channel Monitor sync returned PermanentFailure. Returning monitor events but duplicate events may appear after reload!");
				}
				if is_pending_monitor_update {
					log_error!(self.logger, "A ChannelMonitor sync took longer than {} blocks to complete.", LATENCY_GRACE_PERIOD_BLOCKS);
					log_error!(self.logger, "   To avoid funds-loss, we are allowing monitor updates to be released.");
					log_error!(self.logger, "   This may cause duplicate payment events to be generated.");
				}
				let monitor_events = monitor_state.monitor.get_and_clear_pending_monitor_events();
				if monitor_events.len() > 0 {
					let monitor_outpoint = monitor_state.monitor.get_funding_txo().0;
					let counterparty_node_id = monitor_state.monitor.get_counterparty_node_id();
					pending_monitor_events.push((monitor_outpoint, monitor_events, counterparty_node_id));
				}
			}
		}
		pending_monitor_events
	}
}

impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
	where C::Target: chain::Filter,
	      T::Target: BroadcasterInterface,
	      F::Target: FeeEstimator,
	      L::Target: Logger,
	      P::Target: Persist<ChannelSigner>,
{
	/// Processes [`SpendableOutputs`] events produced from each [`ChannelMonitor`] upon maturity.
	///
	/// An [`EventHandler`] may safely call back to the provider, though this shouldn't be needed in
	/// order to handle these events.
	///
	/// [`SpendableOutputs`]: events::Event::SpendableOutputs
	fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
		let mut pending_events = Vec::new();
		for monitor_state in self.monitors.read().unwrap().values() {
			pending_events.append(&mut monitor_state.monitor.get_and_clear_pending_events());
		}
		for event in pending_events.drain(..) {
			handler.handle_event(&event);
		}
	}
}

#[cfg(test)]
mod tests {
	use bitcoin::BlockHeader;
	use ::{check_added_monitors, check_closed_broadcast, check_closed_event};
	use ::{expect_payment_sent, expect_payment_claimed, expect_payment_sent_without_paths, expect_payment_path_successful, get_event_msg};
	use ::{get_htlc_update_msgs, get_local_commitment_txn, get_revoke_commit_msgs, get_route_and_payment_hash, unwrap_send_err};
	use chain::{ChannelMonitorUpdateErr, Confirm, Watch};
	use chain::channelmonitor::LATENCY_GRACE_PERIOD_BLOCKS;
	use ln::channelmanager::PaymentSendFailure;
	use ln::features::InitFeatures;
	use ln::functional_test_utils::*;
	use ln::msgs::ChannelMessageHandler;
	use util::errors::APIError;
	use util::events::{ClosureReason, MessageSendEvent, MessageSendEventsProvider};
	use util::test_utils::{OnRegisterOutput, TxOutReference};

	/// Tests that in-block dependent transactions are processed by `block_connected` when not
	/// included in `txdata` but returned by [`chain::Filter::register_output`]. For instance,
	/// a (non-anchor) commitment transaction's HTLC output may be spent in the same block as the
	/// commitment transaction itself. An Electrum client may filter the commitment transaction but
	/// needs to return the HTLC transaction so it can be processed.
	#[test]
	fn connect_block_checks_dependent_transactions() {
		let chanmon_cfgs = create_chanmon_cfgs(2);
		let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
		let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
		let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
		let channel = create_announced_chan_between_nodes(
			&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());

		// Send a payment, saving nodes[0]'s revoked commitment and HTLC-Timeout transactions.
		let (commitment_tx, htlc_tx) = {
			let payment_preimage = route_payment(&nodes[0], &vec!(&nodes[1])[..], 5_000_000).0;
			let mut txn = get_local_commitment_txn!(nodes[0], channel.2);
			claim_payment(&nodes[0], &vec!(&nodes[1])[..], payment_preimage);

			assert_eq!(txn.len(), 2);
			(txn.remove(0), txn.remove(0))
		};

		// Set expectations on nodes[1]'s chain source to return dependent transactions.
		let htlc_output = TxOutReference(commitment_tx.clone(), 0);
		let to_local_output = TxOutReference(commitment_tx.clone(), 1);
		let htlc_timeout_output = TxOutReference(htlc_tx.clone(), 0);
		nodes[1].chain_source
			.expect(OnRegisterOutput { with: htlc_output, returns: Some((1, htlc_tx)) })
			.expect(OnRegisterOutput { with: to_local_output, returns: None })
			.expect(OnRegisterOutput { with: htlc_timeout_output, returns: None });

		// Notify nodes[1] that nodes[0]'s revoked commitment transaction was mined. The chain
		// source should return the dependent HTLC transaction when the HTLC output is registered.
		mine_transaction(&nodes[1], &commitment_tx);

		// Clean up so uninteresting assertions don't fail.
		check_added_monitors!(nodes[1], 1);
		nodes[1].node.get_and_clear_pending_msg_events();
		nodes[1].node.get_and_clear_pending_events();
	}

	#[test]
	fn test_async_ooo_offchain_updates() {
		// Test that if we have multiple offchain updates being persisted and they complete
		// out-of-order, the ChainMonitor waits until all have completed before informing the
		// ChannelManager.
		let chanmon_cfgs = create_chanmon_cfgs(2);
		let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
		let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
		let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
		create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());

		// Route two payments to be claimed at the same time.
		let (payment_preimage_1, payment_hash_1, _) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);
		let (payment_preimage_2, payment_hash_2, _) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);

		chanmon_cfgs[1].persister.offchain_monitor_updates.lock().unwrap().clear();
		chanmon_cfgs[1].persister.set_update_ret(Err(ChannelMonitorUpdateErr::TemporaryFailure));

		nodes[1].node.claim_funds(payment_preimage_1);
		check_added_monitors!(nodes[1], 1);
		expect_payment_claimed!(nodes[1], payment_hash_1, 1_000_000);
		nodes[1].node.claim_funds(payment_preimage_2);
		check_added_monitors!(nodes[1], 1);
		expect_payment_claimed!(nodes[1], payment_hash_2, 1_000_000);

		chanmon_cfgs[1].persister.set_update_ret(Ok(()));

		let persistences = chanmon_cfgs[1].persister.offchain_monitor_updates.lock().unwrap().clone();
		assert_eq!(persistences.len(), 1);
		let (funding_txo, updates) = persistences.iter().next().unwrap();
		assert_eq!(updates.len(), 2);

		// Note that updates is a HashMap so the ordering here is actually random. This shouldn't
		// fail either way but if it fails intermittently it's depending on the ordering of updates.
		let mut update_iter = updates.iter();
		nodes[1].chain_monitor.chain_monitor.channel_monitor_updated(*funding_txo, update_iter.next().unwrap().clone()).unwrap();
		assert!(nodes[1].chain_monitor.release_pending_monitor_events().is_empty());
		assert!(nodes[1].node.get_and_clear_pending_msg_events().is_empty());
		nodes[1].chain_monitor.chain_monitor.channel_monitor_updated(*funding_txo, update_iter.next().unwrap().clone()).unwrap();

		// Now manually walk the commitment signed dance - because we claimed two payments
		// back-to-back it doesn't fit into the neat walk commitment_signed_dance does.

		let updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
		nodes[0].node.handle_update_fulfill_htlc(&nodes[1].node.get_our_node_id(), &updates.update_fulfill_htlcs[0]);
		expect_payment_sent_without_paths!(nodes[0], payment_preimage_1);
		nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &updates.commitment_signed);
		check_added_monitors!(nodes[0], 1);
		let (as_first_raa, as_first_update) = get_revoke_commit_msgs!(nodes[0], nodes[1].node.get_our_node_id());

		nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_first_raa);
		check_added_monitors!(nodes[1], 1);
		let bs_second_updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
		nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &as_first_update);
		check_added_monitors!(nodes[1], 1);
		let bs_first_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());

		nodes[0].node.handle_update_fulfill_htlc(&nodes[1].node.get_our_node_id(), &bs_second_updates.update_fulfill_htlcs[0]);
		expect_payment_sent_without_paths!(nodes[0], payment_preimage_2);
		nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &bs_second_updates.commitment_signed);
		check_added_monitors!(nodes[0], 1);
		nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_first_raa);
		expect_payment_path_successful!(nodes[0]);
		check_added_monitors!(nodes[0], 1);
		let (as_second_raa, as_second_update) = get_revoke_commit_msgs!(nodes[0], nodes[1].node.get_our_node_id());

		nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_second_raa);
		check_added_monitors!(nodes[1], 1);
		nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &as_second_update);
		check_added_monitors!(nodes[1], 1);
		let bs_second_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());

		nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_second_raa);
		expect_payment_path_successful!(nodes[0]);
		check_added_monitors!(nodes[0], 1);
	}

	fn do_chainsync_pauses_events(block_timeout: bool) {
		// When a chainsync monitor update occurs, any MonitorUpdates should be held before being
		// passed upstream to a `ChannelManager` via `Watch::release_pending_monitor_events`. This
		// tests that behavior, as well as some ways it might go wrong.
		let chanmon_cfgs = create_chanmon_cfgs(2);
		let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
		let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
		let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
		let channel = create_announced_chan_between_nodes(
			&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());

		// Get a route for later and rebalance the channel somewhat
		send_payment(&nodes[0], &[&nodes[1]], 10_000_000);
		let (route, second_payment_hash, _, second_payment_secret) = get_route_and_payment_hash!(nodes[0], nodes[1], 100_000);

		// First route a payment that we will claim on chain and give the recipient the preimage.
		let (payment_preimage, payment_hash, _) = route_payment(&nodes[0], &[&nodes[1]], 1_000_000);
		nodes[1].node.claim_funds(payment_preimage);
		expect_payment_claimed!(nodes[1], payment_hash, 1_000_000);
		nodes[1].node.get_and_clear_pending_msg_events();
		check_added_monitors!(nodes[1], 1);
		let remote_txn = get_local_commitment_txn!(nodes[1], channel.2);
		assert_eq!(remote_txn.len(), 2);

		// Temp-fail the block connection which will hold the channel-closed event
		chanmon_cfgs[0].persister.chain_sync_monitor_persistences.lock().unwrap().clear();
		chanmon_cfgs[0].persister.set_update_ret(Err(ChannelMonitorUpdateErr::TemporaryFailure));

		// Connect B's commitment transaction, but only to the ChainMonitor/ChannelMonitor. The
		// channel is now closed, but the ChannelManager doesn't know that yet.
		let new_header = BlockHeader {
			version: 2, time: 0, bits: 0, nonce: 0,
			prev_blockhash: nodes[0].best_block_info().0,
			merkle_root: Default::default() };
		nodes[0].chain_monitor.chain_monitor.transactions_confirmed(&new_header,
			&[(0, &remote_txn[0]), (1, &remote_txn[1])], nodes[0].best_block_info().1 + 1);
		assert!(nodes[0].chain_monitor.release_pending_monitor_events().is_empty());
		nodes[0].chain_monitor.chain_monitor.best_block_updated(&new_header, nodes[0].best_block_info().1 + 1);
		assert!(nodes[0].chain_monitor.release_pending_monitor_events().is_empty());

		// If the ChannelManager tries to update the channel, however, the ChainMonitor will pass
		// the update through to the ChannelMonitor which will refuse it (as the channel is closed).
		chanmon_cfgs[0].persister.set_update_ret(Ok(()));
		unwrap_send_err!(nodes[0].node.send_payment(&route, second_payment_hash, &Some(second_payment_secret)),
			true, APIError::ChannelUnavailable { ref err },
			assert!(err.contains("ChannelMonitor storage failure")));
		check_added_monitors!(nodes[0], 2); // After the failure we generate a close-channel monitor update
		check_closed_broadcast!(nodes[0], true);
		check_closed_event!(nodes[0], 1, ClosureReason::ProcessingError { err: "ChannelMonitor storage failure".to_string() });

		// However, as the ChainMonitor is still waiting for the original persistence to complete,
		// it won't yet release the MonitorEvents.
		assert!(nodes[0].chain_monitor.release_pending_monitor_events().is_empty());

		if block_timeout {
			// After three blocks, pending MontiorEvents should be released either way.
			let latest_header = BlockHeader {
				version: 2, time: 0, bits: 0, nonce: 0,
				prev_blockhash: nodes[0].best_block_info().0,
				merkle_root: Default::default() };
			nodes[0].chain_monitor.chain_monitor.best_block_updated(&latest_header, nodes[0].best_block_info().1 + LATENCY_GRACE_PERIOD_BLOCKS);
		} else {
			let persistences = chanmon_cfgs[0].persister.chain_sync_monitor_persistences.lock().unwrap().clone();
			for (funding_outpoint, update_ids) in persistences {
				for update_id in update_ids {
					nodes[0].chain_monitor.chain_monitor.channel_monitor_updated(funding_outpoint, update_id).unwrap();
				}
			}
		}

		expect_payment_sent!(nodes[0], payment_preimage);
	}

	#[test]
	fn chainsync_pauses_events() {
		do_chainsync_pauses_events(false);
		do_chainsync_pauses_events(true);
	}

	#[test]
	fn update_during_chainsync_fails_channel() {
		let chanmon_cfgs = create_chanmon_cfgs(2);
		let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
		let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
		let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
		create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());

		chanmon_cfgs[0].persister.chain_sync_monitor_persistences.lock().unwrap().clear();
		chanmon_cfgs[0].persister.set_update_ret(Err(ChannelMonitorUpdateErr::PermanentFailure));

		connect_blocks(&nodes[0], 1);
		// Before processing events, the ChannelManager will still think the Channel is open and
		// there won't be any ChannelMonitorUpdates
		assert_eq!(nodes[0].node.list_channels().len(), 1);
		check_added_monitors!(nodes[0], 0);
		// ... however once we get events once, the channel will close, creating a channel-closed
		// ChannelMonitorUpdate.
		check_closed_broadcast!(nodes[0], true);
		check_closed_event!(nodes[0], 1, ClosureReason::ProcessingError { err: "Failed to persist ChannelMonitor update during chain sync".to_string() });
		check_added_monitors!(nodes[0], 1);
	}
}