Merge pull request #828 from bmancini55/reply_channel_range
[rust-lightning] / lightning / src / ln / channelmanager.rs
index 3109b8529057661cdafa06383d967ead3ac923b4..970ad2d18a8542620daf54a7b6b24be1f9202cb2 100644 (file)
@@ -206,7 +206,7 @@ pub struct PaymentPreimage(pub [u8;32]);
 #[derive(Hash, Copy, Clone, PartialEq, Eq, Debug)]
 pub struct PaymentSecret(pub [u8;32]);
 
-type ShutdownResult = (Option<OutPoint>, ChannelMonitorUpdate, Vec<(HTLCSource, PaymentHash)>);
+type ShutdownResult = (Option<(OutPoint, ChannelMonitorUpdate)>, Vec<(HTLCSource, PaymentHash)>);
 
 /// Error type returned across the channel_state mutex boundary. When an Err is generated for a
 /// Channel, we generally end up with a ChannelError::Close for which we have to close the channel
@@ -333,6 +333,15 @@ pub(super) struct ChannelHolder<Signer: Sign> {
        pub(super) pending_msg_events: Vec<MessageSendEvent>,
 }
 
+/// Events which we process internally but cannot be procsesed immediately at the generation site
+/// for some reason. They are handled in timer_chan_freshness_every_min, so may be processed with
+/// quite some time lag.
+enum BackgroundEvent {
+       /// Handle a ChannelMonitorUpdate that closes a channel, broadcasting its current latest holder
+       /// commitment transaction.
+       ClosingMonitorUpdate((OutPoint, ChannelMonitorUpdate)),
+}
+
 /// State we hold per-peer. In the future we should put channels in here, but for now we only hold
 /// the latest Init features we heard from the peer.
 struct PeerState {
@@ -380,7 +389,7 @@ pub type SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, M, T, F, L> = ChannelManage
 /// ChannelMonitors passed by reference to read(), those channels will be force-closed based on the
 /// ChannelMonitor state and no funds will be lost (mod on-chain transaction fees).
 ///
-/// Note that the deserializer is only implemented for (Option<BlockHash>, ChannelManager), which
+/// Note that the deserializer is only implemented for (BlockHash, ChannelManager), which
 /// tells you the last block hash which was block_connect()ed. You MUST rescan any blocks along
 /// the "reorg path" (ie call block_disconnected() until you get to a common block and then call
 /// block_connected() to step towards your best block) upon deserialization before using the
@@ -414,7 +423,7 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        pub(super) latest_block_height: AtomicUsize,
        #[cfg(not(test))]
        latest_block_height: AtomicUsize,
-       last_block_hash: Mutex<BlockHash>,
+       last_block_hash: RwLock<BlockHash>,
        secp_ctx: Secp256k1<secp256k1::All>,
 
        #[cfg(any(test, feature = "_test_utils"))]
@@ -436,6 +445,7 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        per_peer_state: RwLock<HashMap<PublicKey, Mutex<PeerState>>>,
 
        pending_events: Mutex<Vec<events::Event>>,
+       pending_background_events: Mutex<Vec<BackgroundEvent>>,
        /// Used when we have to take a BIG lock to make sure everything is self-consistent.
        /// Essentially just when we're serializing ourselves out.
        /// Taken first everywhere where we are making changes before any other locks.
@@ -451,11 +461,30 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        logger: L,
 }
 
+/// Chain-related parameters used to construct a new `ChannelManager`.
+///
+/// Typically, the block-specific parameters are derived from the best block hash for the network,
+/// as a newly constructed `ChannelManager` will not have created any channels yet. These parameters
+/// are not needed when deserializing a previously constructed `ChannelManager`.
+pub struct ChainParameters {
+       /// The network for determining the `chain_hash` in Lightning messages.
+       pub network: Network,
+
+       /// The hash of the latest block successfully connected.
+       pub latest_hash: BlockHash,
+
+       /// The height of the latest block successfully connected.
+       ///
+       /// Used to track on-chain channel funding outputs and send payments with reliable timelocks.
+       pub latest_height: usize,
+}
+
 /// Whenever we release the `ChannelManager`'s `total_consistency_lock`, from read mode, it is
-/// desirable to notify any listeners on `wait_timeout`/`wait` that new updates are available for
-/// persistence. Therefore, this struct is responsible for locking the total consistency lock and,
-/// upon going out of scope, sending the aforementioned notification (since the lock being released
-/// indicates that the updates are ready for persistence).
+/// desirable to notify any listeners on `await_persistable_update_timeout`/
+/// `await_persistable_update` that new updates are available for persistence. Therefore, this
+/// struct is responsible for locking the total consistency lock and, upon going out of scope,
+/// sending the aforementioned notification (since the lock being released indicates that the
+/// updates are ready for persistence).
 struct PersistenceNotifierGuard<'a> {
        persistence_notifier: &'a PersistenceNotifier,
        // We hold onto this result so the lock doesn't get released immediately.
@@ -479,11 +508,12 @@ impl<'a> Drop for PersistenceNotifierGuard<'a> {
        }
 }
 
-/// The amount of time we require our counterparty wait to claim their money (ie time between when
-/// we, or our watchtower, must check for them having broadcast a theft transaction).
+/// The amount of time in blocks we require our counterparty wait to claim their money (ie time
+/// between when we, or our watchtower, must check for them having broadcast a theft transaction).
 pub(crate) const BREAKDOWN_TIMEOUT: u16 = 6 * 24;
-/// The amount of time we're willing to wait to claim money back to us
-pub(crate) const MAX_LOCAL_BREAKDOWN_TIMEOUT: u16 = 6 * 24 * 7;
+/// The amount of time in blocks we're willing to wait to claim money back to us. This matches
+/// the maximum required amount in lnd as of March 2021.
+pub(crate) const MAX_LOCAL_BREAKDOWN_TIMEOUT: u16 = 2 * 6 * 24 * 7;
 
 /// The minimum number of blocks between an inbound HTLC's CLTV and the corresponding outbound
 /// HTLC's CLTV. This should always be a few blocks greater than channelmonitor::CLTV_CLAIM_BUFFER,
@@ -760,24 +790,22 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        ///
        /// panics if channel_value_satoshis is >= `MAX_FUNDING_SATOSHIS`!
        ///
-       /// Users must provide the current blockchain height from which to track onchain channel
-       /// funding outpoints and send payments with reliable timelocks.
-       ///
        /// Users need to notify the new ChannelManager when a new block is connected or
-       /// disconnected using its `block_connected` and `block_disconnected` methods.
-       pub fn new(network: Network, fee_est: F, chain_monitor: M, tx_broadcaster: T, logger: L, keys_manager: K, config: UserConfig, current_blockchain_height: usize) -> Self {
+       /// disconnected using its `block_connected` and `block_disconnected` methods, starting
+       /// from after `params.latest_hash`.
+       pub fn new(fee_est: F, chain_monitor: M, tx_broadcaster: T, logger: L, keys_manager: K, config: UserConfig, params: ChainParameters) -> Self {
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
 
                ChannelManager {
                        default_configuration: config.clone(),
-                       genesis_hash: genesis_block(network).header.block_hash(),
+                       genesis_hash: genesis_block(params.network).header.block_hash(),
                        fee_estimator: fee_est,
                        chain_monitor,
                        tx_broadcaster,
 
-                       latest_block_height: AtomicUsize::new(current_blockchain_height),
-                       last_block_hash: Mutex::new(Default::default()),
+                       latest_block_height: AtomicUsize::new(params.latest_height),
+                       last_block_hash: RwLock::new(params.latest_hash),
                        secp_ctx,
 
                        channel_state: Mutex::new(ChannelHolder{
@@ -794,6 +822,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        per_peer_state: RwLock::new(HashMap::new()),
 
                        pending_events: Mutex::new(Vec::new()),
+                       pending_background_events: Mutex::new(Vec::new()),
                        total_consistency_lock: RwLock::new(()),
                        persistence_notifier: PersistenceNotifier::new(),
 
@@ -942,12 +971,12 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
        #[inline]
        fn finish_force_close_channel(&self, shutdown_res: ShutdownResult) {
-               let (funding_txo_option, monitor_update, mut failed_htlcs) = shutdown_res;
+               let (monitor_update_option, mut failed_htlcs) = shutdown_res;
                log_trace!(self.logger, "Finishing force-closure of channel {} HTLCs to fail", failed_htlcs.len());
                for htlc_source in failed_htlcs.drain(..) {
                        self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_source.0, &htlc_source.1, HTLCFailReason::Reason { failure_code: 0x4000 | 8, data: Vec::new() });
                }
-               if let Some(funding_txo) = funding_txo_option {
+               if let Some((funding_txo, monitor_update)) = monitor_update_option {
                        // There isn't anything we can do if we get an update failure - we're already
                        // force-closing. The monitor update on the required in-memory copy should broadcast
                        // the latest local state, which is the best we can do anyway. Thus, it is safe to
@@ -1854,13 +1883,42 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                events.append(&mut new_events);
        }
 
+       /// Free the background events, generally called from timer_chan_freshness_every_min.
+       ///
+       /// Exposed for testing to allow us to process events quickly without generating accidental
+       /// BroadcastChannelUpdate events in timer_chan_freshness_every_min.
+       ///
+       /// Expects the caller to have a total_consistency_lock read lock.
+       fn process_background_events(&self) {
+               let mut background_events = Vec::new();
+               mem::swap(&mut *self.pending_background_events.lock().unwrap(), &mut background_events);
+               for event in background_events.drain(..) {
+                       match event {
+                               BackgroundEvent::ClosingMonitorUpdate((funding_txo, update)) => {
+                                       // The channel has already been closed, so no use bothering to care about the
+                                       // monitor updating completing.
+                                       let _ = self.chain_monitor.update_channel(funding_txo, update);
+                               },
+                       }
+               }
+       }
+
+       #[cfg(any(test, feature = "_test_utils"))]
+       pub(crate) fn test_process_background_events(&self) {
+               self.process_background_events();
+       }
+
        /// If a peer is disconnected we mark any channels with that peer as 'disabled'.
        /// After some time, if channels are still disabled we need to broadcast a ChannelUpdate
        /// to inform the network about the uselessness of these channels.
        ///
        /// This method handles all the details, and must be called roughly once per minute.
+       ///
+       /// Note that in some rare cases this may generate a `chain::Watch::update_channel` call.
        pub fn timer_chan_freshness_every_min(&self) {
                let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+               self.process_background_events();
+
                let mut channel_state_lock = self.channel_state.lock().unwrap();
                let channel_state = &mut *channel_state_lock;
                for (_, chan) in channel_state.by_id.iter_mut() {
@@ -1953,6 +2011,10 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                //identify whether we sent it or not based on the (I presume) very different runtime
                //between the branches here. We should make this async and move it into the forward HTLCs
                //timer handling.
+
+               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
+               // from block_connected which may run during initialization prior to the chain_monitor
+               // being fully configured. See the docs for `ChannelManagerReadArgs` for more.
                match source {
                        HTLCSource::OutboundRoute { ref path, .. } => {
                                log_trace!(self.logger, "Failing outbound payment HTLC with payment_hash {}", log_bytes!(payment_hash.0));
@@ -2394,6 +2456,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
        fn internal_funding_created(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingCreated) -> Result<(), MsgHandleErrInternal> {
                let ((funding_msg, monitor), mut chan) = {
+                       let last_block_hash = *self.last_block_hash.read().unwrap();
                        let mut channel_lock = self.channel_state.lock().unwrap();
                        let channel_state = &mut *channel_lock;
                        match channel_state.by_id.entry(msg.temporary_channel_id.clone()) {
@@ -2401,7 +2464,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        if chan.get().get_counterparty_node_id() != *counterparty_node_id {
                                                return Err(MsgHandleErrInternal::send_err_msg_no_close("Got a message for a channel from the wrong node!".to_owned(), msg.temporary_channel_id));
                                        }
-                                       (try_chan_entry!(self, chan.get_mut().funding_created(msg, &self.logger), channel_state, chan), chan.remove())
+                                       (try_chan_entry!(self, chan.get_mut().funding_created(msg, last_block_hash, &self.logger), channel_state, chan), chan.remove())
                                },
                                hash_map::Entry::Vacant(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close("Failed to find corresponding channel".to_owned(), msg.temporary_channel_id))
                        }
@@ -2418,7 +2481,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        // We do not do a force-close here as that would generate a monitor update for
                                        // a monitor that we didn't manage to store (and that we don't care about - we
                                        // don't respond with the funding_signed so the channel can never go on chain).
-                                       let (_funding_txo_option, _monitor_update, failed_htlcs) = chan.force_shutdown(true);
+                                       let (_monitor_update, failed_htlcs) = chan.force_shutdown(true);
                                        assert!(failed_htlcs.is_empty());
                                        return Err(MsgHandleErrInternal::send_err_msg_no_close("ChannelMonitor storage failure".to_owned(), funding_msg.channel_id));
                                },
@@ -2450,6 +2513,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
        fn internal_funding_signed(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingSigned) -> Result<(), MsgHandleErrInternal> {
                let (funding_txo, user_id) = {
+                       let last_block_hash = *self.last_block_hash.read().unwrap();
                        let mut channel_lock = self.channel_state.lock().unwrap();
                        let channel_state = &mut *channel_lock;
                        match channel_state.by_id.entry(msg.channel_id) {
@@ -2457,7 +2521,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        if chan.get().get_counterparty_node_id() != *counterparty_node_id {
                                                return Err(MsgHandleErrInternal::send_err_msg_no_close("Got a message for a channel from the wrong node!".to_owned(), msg.channel_id));
                                        }
-                                       let monitor = match chan.get_mut().funding_signed(&msg, &self.logger) {
+                                       let monitor = match chan.get_mut().funding_signed(&msg, last_block_hash, &self.logger) {
                                                Ok(update) => update,
                                                Err(e) => try_chan_entry!(self, Err(e), channel_state, chan),
                                        };
@@ -3100,6 +3164,29 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        self.finish_force_close_channel(failure);
                }
        }
+
+       /// Handle a list of channel failures during a block_connected or block_disconnected call,
+       /// pushing the channel monitor update (if any) to the background events queue and removing the
+       /// Channel object.
+       fn handle_init_event_channel_failures(&self, mut failed_channels: Vec<ShutdownResult>) {
+               for mut failure in failed_channels.drain(..) {
+                       // Either a commitment transactions has been confirmed on-chain or
+                       // Channel::block_disconnected detected that the funding transaction has been
+                       // reorganized out of the main chain.
+                       // We cannot broadcast our latest local state via monitor update (as
+                       // Channel::force_shutdown tries to make us do) as we may still be in initialization,
+                       // so we track the update internally and handle it when the user next calls
+                       // timer_chan_freshness_every_min, guaranteeing we're running normally.
+                       if let Some((funding_txo, update)) = failure.0.take() {
+                               assert_eq!(update.updates.len(), 1);
+                               if let ChannelMonitorUpdateStep::ChannelForceClosed { should_broadcast } = update.updates[0] {
+                                       assert!(should_broadcast);
+                               } else { unreachable!(); }
+                               self.pending_background_events.lock().unwrap().push(BackgroundEvent::ClosingMonitorUpdate((funding_txo, update)));
+                       }
+                       self.finish_force_close_channel(failure);
+               }
+       }
 }
 
 impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> MessageSendEventsProvider for ChannelManager<Signer, M, T, K, F, L>
@@ -3167,9 +3254,17 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 {
        /// Updates channel state based on transactions seen in a connected block.
        pub fn block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
-               let header_hash = header.block_hash();
-               log_trace!(self.logger, "Block {} at height {} connected", header_hash, height);
+               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
+               // during initialization prior to the chain_monitor being fully configured in some cases.
+               // See the docs for `ChannelManagerReadArgs` for more.
+               let block_hash = header.block_hash();
+               log_trace!(self.logger, "Block {} at height {} connected", block_hash, height);
+
                let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+
+               self.latest_block_height.store(height as usize, Ordering::Release);
+               *self.last_block_hash.write().unwrap() = block_hash;
+
                let mut failed_channels = Vec::new();
                let mut timed_out_htlcs = Vec::new();
                {
@@ -3218,9 +3313,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                if let Some(short_id) = channel.get_short_channel_id() {
                                                                        short_to_id.remove(&short_id);
                                                                }
-                                                               // It looks like our counterparty went on-chain. We go ahead and
-                                                               // broadcast our latest local state as well here, just in case its
-                                                               // some kind of SPV attack, though we expect these to be dropped.
+                                                               // It looks like our counterparty went on-chain. Close the channel.
                                                                failed_channels.push(channel.force_shutdown(true));
                                                                if let Ok(update) = self.get_channel_update(&channel) {
                                                                        pending_msg_events.push(events::MessageSendEvent::BroadcastChannelUpdate {
@@ -3254,15 +3347,13 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                !htlcs.is_empty() // Only retain this entry if htlcs has at least one entry.
                        });
                }
-               for failure in failed_channels.drain(..) {
-                       self.finish_force_close_channel(failure);
-               }
+
+               self.handle_init_event_channel_failures(failed_channels);
 
                for (source, payment_hash, reason) in timed_out_htlcs.drain(..) {
                        self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), source, &payment_hash, reason);
                }
-               self.latest_block_height.store(height as usize, Ordering::Release);
-               *self.last_block_hash.try_lock().expect("block_(dis)connected must not be called in parallel") = header_hash;
+
                loop {
                        // Update last_node_announcement_serial to be the max of its current value and the
                        // block timestamp. This should keep us close to the current time without relying on
@@ -3282,7 +3373,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        /// If necessary, the channel may be force-closed without letting the counterparty participate
        /// in the shutdown.
        pub fn block_disconnected(&self, header: &BlockHeader) {
+               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
+               // during initialization prior to the chain_monitor being fully configured in some cases.
+               // See the docs for `ChannelManagerReadArgs` for more.
                let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+
+               self.latest_block_height.fetch_sub(1, Ordering::AcqRel);
+               *self.last_block_hash.write().unwrap() = header.prev_blockhash;
+
                let mut failed_channels = Vec::new();
                {
                        let mut channel_lock = self.channel_state.lock().unwrap();
@@ -3306,25 +3404,24 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                }
                        });
                }
-               for failure in failed_channels.drain(..) {
-                       self.finish_force_close_channel(failure);
-               }
-               self.latest_block_height.fetch_sub(1, Ordering::AcqRel);
-               *self.last_block_hash.try_lock().expect("block_(dis)connected must not be called in parallel") = header.block_hash();
+
+               self.handle_init_event_channel_failures(failed_channels);
        }
 
        /// Blocks until ChannelManager needs to be persisted or a timeout is reached. It returns a bool
-       /// indicating whether persistence is necessary. Only one listener on `wait_timeout` is
-       /// guaranteed to be woken up.
+       /// indicating whether persistence is necessary. Only one listener on
+       /// `await_persistable_update` or `await_persistable_update_timeout` is guaranteed to be woken
+       /// up.
        /// Note that the feature `allow_wallclock_use` must be enabled to use this function.
        #[cfg(any(test, feature = "allow_wallclock_use"))]
-       pub fn wait_timeout(&self, max_wait: Duration) -> bool {
+       pub fn await_persistable_update_timeout(&self, max_wait: Duration) -> bool {
                self.persistence_notifier.wait_timeout(max_wait)
        }
 
-       /// Blocks until ChannelManager needs to be persisted. Only one listener on `wait` is
-       /// guaranteed to be woken up.
-       pub fn wait(&self) {
+       /// Blocks until ChannelManager needs to be persisted. Only one listener on
+       /// `await_persistable_update` or `await_persistable_update_timeout` is guaranteed to be woken
+       /// up.
+       pub fn await_persistable_update(&self) {
                self.persistence_notifier.wait()
        }
 
@@ -3577,7 +3674,7 @@ impl<Signer: Sign, M: Deref + Sync + Send, T: Deref + Sync + Send, K: Deref + Sy
 }
 
 /// Used to signal to the ChannelManager persister that the manager needs to be re-persisted to
-/// disk/backups, through `wait_timeout` and `wait`.
+/// disk/backups, through `await_persistable_update_timeout` and `await_persistable_update`.
 struct PersistenceNotifier {
        /// Users won't access the persistence_lock directly, but rather wait on its bool using
        /// `wait_timeout` and `wait`.
@@ -3867,7 +3964,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
 
                self.genesis_hash.write(writer)?;
                (self.latest_block_height.load(Ordering::Acquire) as u32).write(writer)?;
-               self.last_block_hash.lock().unwrap().write(writer)?;
+               self.last_block_hash.read().unwrap().write(writer)?;
 
                let channel_state = self.channel_state.lock().unwrap();
                let mut unfunded_channels = 0;
@@ -3915,6 +4012,18 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
                        event.write(writer)?;
                }
 
+               let background_events = self.pending_background_events.lock().unwrap();
+               (background_events.len() as u64).write(writer)?;
+               for event in background_events.iter() {
+                       match event {
+                               BackgroundEvent::ClosingMonitorUpdate((funding_txo, monitor_update)) => {
+                                       0u8.write(writer)?;
+                                       funding_txo.write(writer)?;
+                                       monitor_update.write(writer)?;
+                               },
+                       }
+               }
+
                (self.last_node_announcement_serial.load(Ordering::Acquire) as u32).write(writer)?;
 
                Ok(())
@@ -3926,15 +4035,26 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
 /// At a high-level, the process for deserializing a ChannelManager and resuming normal operation
 /// is:
 /// 1) Deserialize all stored ChannelMonitors.
-/// 2) Deserialize the ChannelManager by filling in this struct and calling <(Option<BlockHash>,
-///    ChannelManager)>::read(reader, args).
+/// 2) Deserialize the ChannelManager by filling in this struct and calling:
+///    <(BlockHash, ChannelManager)>::read(reader, args)
 ///    This may result in closing some Channels if the ChannelMonitor is newer than the stored
 ///    ChannelManager state to ensure no loss of funds. Thus, transactions may be broadcasted.
-/// 3) Register all relevant ChannelMonitor outpoints with your chain watch mechanism using
-///    ChannelMonitor::get_outputs_to_watch() and ChannelMonitor::get_funding_txo().
+/// 3) If you are not fetching full blocks, register all relevant ChannelMonitor outpoints the same
+///    way you would handle a `chain::Filter` call using ChannelMonitor::get_outputs_to_watch() and
+///    ChannelMonitor::get_funding_txo().
 /// 4) Reconnect blocks on your ChannelMonitors.
-/// 5) Move the ChannelMonitors into your local chain::Watch.
-/// 6) Disconnect/connect blocks on the ChannelManager.
+/// 5) Disconnect/connect blocks on the ChannelManager.
+/// 6) Move the ChannelMonitors into your local chain::Watch.
+///
+/// Note that the ordering of #4-6 is not of importance, however all three must occur before you
+/// call any other methods on the newly-deserialized ChannelManager.
+///
+/// Note that because some channels may be closed during deserialization, it is critical that you
+/// always deserialize only the latest version of a ChannelManager and ChannelMonitors available to
+/// you. If you deserialize an old ChannelManager (during which force-closure transactions may be
+/// broadcast), and then later deserialize a newer version of the same ChannelManager (which will
+/// not force-close the same channels but consider them live), you may end up revoking a state for
+/// which you've already broadcasted the transaction.
 pub struct ChannelManagerReadArgs<'a, Signer: 'a + Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
        where M::Target: chain::Watch<Signer>,
         T::Target: BroadcasterInterface,
@@ -4007,7 +4127,7 @@ impl<'a, Signer: 'a + Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
 // Implement ReadableArgs for an Arc'd ChannelManager to make it a bit easier to work with the
 // SipmleArcChannelManager type:
 impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
-       ReadableArgs<ChannelManagerReadArgs<'a, Signer, M, T, K, F, L>> for (Option<BlockHash>, Arc<ChannelManager<Signer, M, T, K, F, L>>)
+       ReadableArgs<ChannelManagerReadArgs<'a, Signer, M, T, K, F, L>> for (BlockHash, Arc<ChannelManager<Signer, M, T, K, F, L>>)
        where M::Target: chain::Watch<Signer>,
         T::Target: BroadcasterInterface,
         K::Target: KeysInterface<Signer = Signer>,
@@ -4015,13 +4135,13 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
         L::Target: Logger,
 {
        fn read<R: ::std::io::Read>(reader: &mut R, args: ChannelManagerReadArgs<'a, Signer, M, T, K, F, L>) -> Result<Self, DecodeError> {
-               let (blockhash, chan_manager) = <(Option<BlockHash>, ChannelManager<Signer, M, T, K, F, L>)>::read(reader, args)?;
+               let (blockhash, chan_manager) = <(BlockHash, ChannelManager<Signer, M, T, K, F, L>)>::read(reader, args)?;
                Ok((blockhash, Arc::new(chan_manager)))
        }
 }
 
 impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
-       ReadableArgs<ChannelManagerReadArgs<'a, Signer, M, T, K, F, L>> for (Option<BlockHash>, ChannelManager<Signer, M, T, K, F, L>)
+       ReadableArgs<ChannelManagerReadArgs<'a, Signer, M, T, K, F, L>> for (BlockHash, ChannelManager<Signer, M, T, K, F, L>)
        where M::Target: chain::Watch<Signer>,
         T::Target: BroadcasterInterface,
         K::Target: KeysInterface<Signer = Signer>,
@@ -4047,10 +4167,6 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                let mut short_to_id = HashMap::with_capacity(cmp::min(channel_count as usize, 128));
                for _ in 0..channel_count {
                        let mut channel: Channel<Signer> = Channel::read(reader, &args.keys_manager)?;
-                       if channel.last_block_connected != Default::default() && channel.last_block_connected != last_block_hash {
-                               return Err(DecodeError::InvalidValue);
-                       }
-
                        let funding_txo = channel.get_funding_txo().ok_or(DecodeError::InvalidValue)?;
                        funding_txo_set.insert(funding_txo.clone());
                        if let Some(ref mut monitor) = args.channel_monitors.get_mut(&funding_txo) {
@@ -4065,7 +4181,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                                                channel.get_cur_counterparty_commitment_transaction_number() > monitor.get_cur_counterparty_commitment_number() ||
                                                channel.get_latest_monitor_update_id() < monitor.get_latest_update_id() {
                                        // But if the channel is behind of the monitor, close the channel:
-                                       let (_, _, mut new_failed_htlcs) = channel.force_shutdown(true);
+                                       let (_, mut new_failed_htlcs) = channel.force_shutdown(true);
                                        failed_htlcs.append(&mut new_failed_htlcs);
                                        monitor.broadcast_latest_holder_commitment_txn(&args.tx_broadcaster, &args.logger);
                                } else {
@@ -4129,6 +4245,15 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                        }
                }
 
+               let background_event_count: u64 = Readable::read(reader)?;
+               let mut pending_background_events_read: Vec<BackgroundEvent> = Vec::with_capacity(cmp::min(background_event_count as usize, MAX_ALLOC_SIZE/mem::size_of::<BackgroundEvent>()));
+               for _ in 0..background_event_count {
+                       match <u8 as Readable>::read(reader)? {
+                               0 => pending_background_events_read.push(BackgroundEvent::ClosingMonitorUpdate((Readable::read(reader)?, Readable::read(reader)?))),
+                               _ => return Err(DecodeError::InvalidValue),
+                       }
+               }
+
                let last_node_announcement_serial: u32 = Readable::read(reader)?;
 
                let mut secp_ctx = Secp256k1::new();
@@ -4141,7 +4266,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                        tx_broadcaster: args.tx_broadcaster,
 
                        latest_block_height: AtomicUsize::new(latest_block_height as usize),
-                       last_block_hash: Mutex::new(last_block_hash),
+                       last_block_hash: RwLock::new(last_block_hash),
                        secp_ctx,
 
                        channel_state: Mutex::new(ChannelHolder {
@@ -4158,6 +4283,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                        per_peer_state: RwLock::new(per_peer_state),
 
                        pending_events: Mutex::new(pending_events_read),
+                       pending_background_events: Mutex::new(pending_background_events_read),
                        total_consistency_lock: RwLock::new(()),
                        persistence_notifier: PersistenceNotifier::new(),
 
@@ -4173,12 +4299,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                //TODO: Broadcast channel update for closed channels, but only after we've made a
                //connection or two.
 
-               let last_seen_block_hash = if last_block_hash == Default::default() {
-                       None
-               } else {
-                       Some(last_block_hash)
-               };
-               Ok((last_seen_block_hash, channel_manager))
+               Ok((last_block_hash.clone(), channel_manager))
        }
 }