Use core replacements for std members
[rust-lightning] / lightning / src / chain / channelmonitor.rs
index c2c791c4b172b8335c43117ff191e93320c3cddc..8526ce51722afefa80d14657f095fbcbfdf41ab2 100644 (file)
@@ -19,8 +19,6 @@
 //! ChannelMonitors should do so). Thus, if you're building rust-lightning into an HSM or other
 //! security-domain-separated system design, you should consider having multiple paths for
 //! ChannelMonitors to get out of the HSM and onto monitoring devices.
-//!
-//! [`chain::Watch`]: ../trait.Watch.html
 
 use bitcoin::blockdata::block::{Block, BlockHeader};
 use bitcoin::blockdata::transaction::{TxOut,Transaction};
@@ -36,12 +34,14 @@ use bitcoin::secp256k1::{Secp256k1,Signature};
 use bitcoin::secp256k1::key::{SecretKey,PublicKey};
 use bitcoin::secp256k1;
 
+use ln::{PaymentHash, PaymentPreimage};
 use ln::msgs::DecodeError;
 use ln::chan_utils;
 use ln::chan_utils::{CounterpartyCommitmentSecrets, HTLCOutputInCommitment, HTLCType, ChannelTransactionParameters, HolderCommitmentTransaction};
-use ln::channelmanager::{HTLCSource, PaymentPreimage, PaymentHash};
+use ln::channelmanager::{BestBlock, HTLCSource};
 use ln::onchaintx::{OnchainTxHandler, InputDescriptors};
 use chain;
+use chain::WatchedOutput;
 use chain::chaininterface::{BroadcasterInterface, FeeEstimator};
 use chain::transaction::{OutPoint, TransactionData};
 use chain::keysinterface::{SpendableOutputDescriptor, StaticPaymentOutputDescriptor, DelayedPaymentOutputDescriptor, Sign, KeysInterface};
@@ -51,10 +51,10 @@ use util::ser::{Readable, ReadableArgs, MaybeReadable, Writer, Writeable, U48};
 use util::byte_utils;
 use util::events::Event;
 
-use std::collections::{HashMap, HashSet, hash_map};
-use std::{cmp, mem};
+use std::collections::{HashMap, HashSet};
+use core::{cmp, mem};
 use std::io::Error;
-use std::ops::Deref;
+use core::ops::Deref;
 use std::sync::Mutex;
 
 /// An update generated by the underlying Channel itself which contains some new information the
@@ -75,8 +75,6 @@ pub struct ChannelMonitorUpdate {
        /// The only instance where update_id values are not strictly increasing is the case where we
        /// allow post-force-close updates with a special update ID of [`CLOSED_CHANNEL_UPDATE_ID`]. See
        /// its docs for more details.
-       ///
-       /// [`CLOSED_CHANNEL_UPDATE_ID`]: constant.CLOSED_CHANNEL_UPDATE_ID.html
        pub update_id: u64,
 }
 
@@ -87,7 +85,7 @@ pub struct ChannelMonitorUpdate {
 /// then we allow the `ChannelManager` to send a `ChannelMonitorUpdate` with this update ID,
 /// with the update providing said payment preimage. No other update types are allowed after
 /// force-close.
-pub const CLOSED_CHANNEL_UPDATE_ID: u64 = std::u64::MAX;
+pub const CLOSED_CHANNEL_UPDATE_ID: u64 = core::u64::MAX;
 
 impl Writeable for ChannelMonitorUpdate {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
@@ -103,7 +101,7 @@ impl Readable for ChannelMonitorUpdate {
        fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                let update_id: u64 = Readable::read(r)?;
                let len: u64 = Readable::read(r)?;
-               let mut updates = Vec::with_capacity(cmp::min(len as usize, MAX_ALLOC_SIZE / ::std::mem::size_of::<ChannelMonitorUpdateStep>()));
+               let mut updates = Vec::with_capacity(cmp::min(len as usize, MAX_ALLOC_SIZE / ::core::mem::size_of::<ChannelMonitorUpdateStep>()));
                for _ in 0..len {
                        updates.push(Readable::read(r)?);
                }
@@ -193,8 +191,6 @@ pub enum MonitorEvent {
 /// Simple structure sent back by `chain::Watch` when an HTLC from a forward channel is detected on
 /// chain. Used to update the corresponding HTLC in the backward channel. Failing to pass the
 /// preimage claim backward will lead to loss of funds.
-///
-/// [`chain::Watch`]: ../trait.Watch.html
 #[derive(Clone, PartialEq)]
 pub struct HTLCUpdate {
        pub(crate) payment_hash: PaymentHash,
@@ -210,7 +206,7 @@ pub(crate) const CLTV_SHARED_CLAIM_BUFFER: u32 = 12;
 /// HTLC-Success transaction.
 /// In other words, this is an upper bound on how many blocks we think it can take us to get a
 /// transaction confirmed (and we use it in a few more, equivalent, places).
-pub(crate) const CLTV_CLAIM_BUFFER: u32 = 6;
+pub(crate) const CLTV_CLAIM_BUFFER: u32 = 18;
 /// Number of blocks by which point we expect our counterparty to have seen new blocks on the
 /// network and done a full update_fail_htlc/commitment_signed dance (+ we've updated all our
 /// copies of ChannelMonitors, including watchtowers). We could enforce the contract by failing
@@ -470,9 +466,30 @@ pub(crate) struct ClaimRequest {
        pub(crate) witness_data: InputMaterial
 }
 
+/// An entry for an [`OnchainEvent`], stating the block height when the event was observed and the
+/// transaction causing it.
+///
+/// Used to determine when the on-chain event can be considered safe from a chain reorganization.
+#[derive(PartialEq)]
+struct OnchainEventEntry {
+       txid: Txid,
+       height: u32,
+       event: OnchainEvent,
+}
+
+impl OnchainEventEntry {
+       fn confirmation_threshold(&self) -> u32 {
+               self.height + ANTI_REORG_DELAY - 1
+       }
+
+       fn has_reached_confirmation_threshold(&self, height: u32) -> bool {
+               height >= self.confirmation_threshold()
+       }
+}
+
 /// Upon discovering of some classes of onchain tx by ChannelMonitor, we may have to take actions on it
 /// once they mature to enough confirmations (ANTI_REORG_DELAY)
-#[derive(Clone, PartialEq)]
+#[derive(PartialEq)]
 enum OnchainEvent {
        /// HTLC output getting solved by a timeout, at maturation we pass upstream payment source information to solve
        /// inbound HTLC in backward channel. Note, in case of preimage, we pass info to upstream without delay as we can
@@ -689,10 +706,10 @@ pub(crate) struct ChannelMonitorImpl<Signer: Sign> {
        pending_monitor_events: Vec<MonitorEvent>,
        pending_events: Vec<Event>,
 
-       // Used to track onchain events, i.e transactions parts of channels confirmed on chain, on which
-       // we have to take actions once they reach enough confs. Key is a block height timer, i.e we enforce
-       // actions when we receive a block with given height. Actions depend on OnchainEvent type.
-       onchain_events_waiting_threshold_conf: HashMap<u32, Vec<OnchainEvent>>,
+       // Used to track on-chain events (i.e., transactions part of channels confirmed on chain) on
+       // which to take actions once they reach enough confirmations. Each entry includes the
+       // transaction's id and the height when the transaction was confirmed on chain.
+       onchain_events_awaiting_threshold_conf: Vec<OnchainEventEntry>,
 
        // If we get serialized out and re-read, we need to make sure that the chain monitoring
        // interface knows about the TXOs that we want to be notified of spends of. We could probably
@@ -719,15 +736,19 @@ pub(crate) struct ChannelMonitorImpl<Signer: Sign> {
        // remote monitor out-of-order with regards to the block view.
        holder_tx_signed: bool,
 
-       // We simply modify last_block_hash in Channel's block_connected so that serialization is
+       // We simply modify best_block in Channel's block_connected so that serialization is
        // consistent but hopefully the users' copy handles block_connected in a consistent way.
        // (we do *not*, however, update them in update_monitor to ensure any local user copies keep
-       // their last_block_hash from its state and not based on updated copies that didn't run through
+       // their best_block from its state and not based on updated copies that didn't run through
        // the full block_connected).
-       last_block_hash: BlockHash,
+       best_block: BestBlock,
+
        secp_ctx: Secp256k1<secp256k1::All>, //TODO: dedup this a bit...
 }
 
+/// Transaction outputs to watch for on-chain spends.
+pub type TransactionOutputs = (Txid, Vec<(u32, TxOut)>);
+
 #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
 /// Used only in testing and fuzztarget to check serialization roundtrips don't change the
 /// underlying object
@@ -770,7 +791,7 @@ impl<Signer: Sign> PartialEq for ChannelMonitorImpl<Signer> {
                        self.payment_preimages != other.payment_preimages ||
                        self.pending_monitor_events != other.pending_monitor_events ||
                        self.pending_events.len() != other.pending_events.len() || // We trust events to round-trip properly
-                       self.onchain_events_waiting_threshold_conf != other.onchain_events_waiting_threshold_conf ||
+                       self.onchain_events_awaiting_threshold_conf != other.onchain_events_awaiting_threshold_conf ||
                        self.outputs_to_watch != other.outputs_to_watch ||
                        self.lockdown_from_offchain != other.lockdown_from_offchain ||
                        self.holder_tx_signed != other.holder_tx_signed
@@ -936,24 +957,23 @@ impl<Signer: Sign> Writeable for ChannelMonitorImpl<Signer> {
                        event.write(writer)?;
                }
 
-               self.last_block_hash.write(writer)?;
+               self.best_block.block_hash().write(writer)?;
+               writer.write_all(&byte_utils::be32_to_array(self.best_block.height()))?;
 
-               writer.write_all(&byte_utils::be64_to_array(self.onchain_events_waiting_threshold_conf.len() as u64))?;
-               for (ref target, ref events) in self.onchain_events_waiting_threshold_conf.iter() {
-                       writer.write_all(&byte_utils::be32_to_array(**target))?;
-                       writer.write_all(&byte_utils::be64_to_array(events.len() as u64))?;
-                       for ev in events.iter() {
-                               match *ev {
-                                       OnchainEvent::HTLCUpdate { ref htlc_update } => {
-                                               0u8.write(writer)?;
-                                               htlc_update.0.write(writer)?;
-                                               htlc_update.1.write(writer)?;
-                                       },
-                                       OnchainEvent::MaturingOutput { ref descriptor } => {
-                                               1u8.write(writer)?;
-                                               descriptor.write(writer)?;
-                                       },
-                               }
+               writer.write_all(&byte_utils::be64_to_array(self.onchain_events_awaiting_threshold_conf.len() as u64))?;
+               for ref entry in self.onchain_events_awaiting_threshold_conf.iter() {
+                       entry.txid.write(writer)?;
+                       writer.write_all(&byte_utils::be32_to_array(entry.height))?;
+                       match entry.event {
+                               OnchainEvent::HTLCUpdate { ref htlc_update } => {
+                                       0u8.write(writer)?;
+                                       htlc_update.0.write(writer)?;
+                                       htlc_update.1.write(writer)?;
+                               },
+                               OnchainEvent::MaturingOutput { ref descriptor } => {
+                                       1u8.write(writer)?;
+                                       descriptor.write(writer)?;
+                               },
                        }
                }
 
@@ -982,7 +1002,7 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
                          funding_redeemscript: Script, channel_value_satoshis: u64,
                          commitment_transaction_number_obscure_factor: u64,
                          initial_holder_commitment_tx: HolderCommitmentTransaction,
-                         last_block_hash: BlockHash) -> ChannelMonitor<Signer> {
+                         best_block: BestBlock) -> ChannelMonitor<Signer> {
 
                assert!(commitment_transaction_number_obscure_factor <= (1 << 48));
                let our_channel_close_key_hash = WPubkeyHash::hash(&shutdown_pubkey.serialize());
@@ -1061,7 +1081,7 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
                                pending_monitor_events: Vec::new(),
                                pending_events: Vec::new(),
 
-                               onchain_events_waiting_threshold_conf: HashMap::new(),
+                               onchain_events_awaiting_threshold_conf: Vec::new(),
                                outputs_to_watch,
 
                                onchain_tx_handler,
@@ -1069,7 +1089,8 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
                                lockdown_from_offchain: false,
                                holder_tx_signed: false,
 
-                               last_block_hash,
+                               best_block,
+
                                secp_ctx,
                        }),
                }
@@ -1180,15 +1201,17 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
                for (txid, outputs) in lock.get_outputs_to_watch().iter() {
                        for (index, script_pubkey) in outputs.iter() {
                                assert!(*index <= u16::max_value() as u32);
-                               filter.register_output(&OutPoint { txid: *txid, index: *index as u16 }, script_pubkey);
+                               filter.register_output(WatchedOutput {
+                                       block_hash: None,
+                                       outpoint: OutPoint { txid: *txid, index: *index as u16 },
+                                       script_pubkey: script_pubkey.clone(),
+                               });
                        }
                }
        }
 
        /// Get the list of HTLCs who's status has been updated on chain. This should be called by
        /// ChannelManager via [`chain::Watch::release_pending_monitor_events`].
-       ///
-       /// [`chain::Watch::release_pending_monitor_events`]: ../trait.Watch.html#tymethod.release_pending_monitor_events
        pub fn get_and_clear_pending_monitor_events(&self) -> Vec<MonitorEvent> {
                self.inner.lock().unwrap().get_and_clear_pending_monitor_events()
        }
@@ -1257,7 +1280,7 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
                broadcaster: B,
                fee_estimator: F,
                logger: L,
-       ) -> Vec<(Txid, Vec<(u32, TxOut)>)>
+       ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
@@ -1284,6 +1307,89 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
                self.inner.lock().unwrap().block_disconnected(
                        header, height, broadcaster, fee_estimator, logger)
        }
+
+       /// Processes transactions confirmed in a block with the given header and height, returning new
+       /// outputs to watch. See [`block_connected`] for details.
+       ///
+       /// Used instead of [`block_connected`] by clients that are notified of transactions rather than
+       /// blocks. See [`chain::Confirm`] for calling expectations.
+       ///
+       /// [`block_connected`]: Self::block_connected
+       pub fn transactions_confirmed<B: Deref, F: Deref, L: Deref>(
+               &self,
+               header: &BlockHeader,
+               txdata: &TransactionData,
+               height: u32,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) -> Vec<TransactionOutputs>
+       where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
+       {
+               self.inner.lock().unwrap().transactions_confirmed(
+                       header, txdata, height, broadcaster, fee_estimator, logger)
+       }
+
+       /// Processes a transaction that was reorganized out of the chain.
+       ///
+       /// Used instead of [`block_disconnected`] by clients that are notified of transactions rather
+       /// than blocks. See [`chain::Confirm`] for calling expectations.
+       ///
+       /// [`block_disconnected`]: Self::block_disconnected
+       pub fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
+               &self,
+               txid: &Txid,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
+       {
+               self.inner.lock().unwrap().transaction_unconfirmed(
+                       txid, broadcaster, fee_estimator, logger);
+       }
+
+       /// Updates the monitor with the current best chain tip, returning new outputs to watch. See
+       /// [`block_connected`] for details.
+       ///
+       /// Used instead of [`block_connected`] by clients that are notified of transactions rather than
+       /// blocks. See [`chain::Confirm`] for calling expectations.
+       ///
+       /// [`block_connected`]: Self::block_connected
+       pub fn best_block_updated<B: Deref, F: Deref, L: Deref>(
+               &self,
+               header: &BlockHeader,
+               height: u32,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) -> Vec<TransactionOutputs>
+       where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
+       {
+               self.inner.lock().unwrap().best_block_updated(
+                       header, height, broadcaster, fee_estimator, logger)
+       }
+
+       /// Returns the set of txids that should be monitored for re-organization out of the chain.
+       pub fn get_relevant_txids(&self) -> Vec<Txid> {
+               let inner = self.inner.lock().unwrap();
+               let mut txids: Vec<Txid> = inner.onchain_events_awaiting_threshold_conf
+                       .iter()
+                       .map(|entry| entry.txid)
+                       .chain(inner.onchain_tx_handler.get_relevant_txids().into_iter())
+                       .collect();
+               txids.sort_unstable();
+               txids.dedup();
+               txids
+       }
 }
 
 impl<Signer: Sign> ChannelMonitorImpl<Signer> {
@@ -1462,6 +1568,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                        L::Target: Logger,
        {
                for tx in self.get_latest_holder_commitment_txn(logger).iter() {
+                       log_info!(logger, "Broadcasting local {}", log_tx!(tx));
                        broadcaster.broadcast_transaction(tx);
                }
                self.pending_monitor_events.push(MonitorEvent::CommitmentTxBroadcasted(self.funding_info.0));
@@ -1509,8 +1616,13 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                        self.lockdown_from_offchain = true;
                                        if *should_broadcast {
                                                self.broadcast_latest_holder_commitment_txn(broadcaster, logger);
-                                       } else {
+                                       } else if !self.holder_tx_signed {
                                                log_error!(logger, "You have a toxic holder commitment transaction avaible in channel monitor, read comment in ChannelMonitor::get_latest_holder_commitment_txn to be informed of manual action to take");
+                                       } else {
+                                               // If we generated a MonitorEvent::CommitmentTxBroadcasted, the ChannelManager
+                                               // will still give us a ChannelForceClosed event with !should_broadcast, but we
+                                               // shouldn't print the scary warning above.
+                                               log_info!(logger, "Channel off-chain state closed after we broadcasted our latest commitment transaction.");
                                        }
                                }
                        }
@@ -1572,7 +1684,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
        /// HTLC-Success/HTLC-Timeout transactions.
        /// Return updates for HTLC pending in the channel and failed automatically by the broadcast of
        /// revoked counterparty commitment tx
-       fn check_spend_counterparty_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> (Vec<ClaimRequest>, (Txid, Vec<(u32, TxOut)>)) where L::Target: Logger {
+       fn check_spend_counterparty_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> (Vec<ClaimRequest>, TransactionOutputs) where L::Target: Logger {
                // Most secp and related errors trying to create keys means we have no hope of constructing
                // a spend transaction...so we return no transactions to broadcast
                let mut claimable_outpoints = Vec::new();
@@ -1637,24 +1749,24 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                                if let Some(ref outpoints) = self.counterparty_claimable_outpoints.get($txid) {
                                                        for &(ref htlc, ref source_option) in outpoints.iter() {
                                                                if let &Some(ref source) = source_option {
-                                                                       log_info!(logger, "Failing HTLC with payment_hash {} from {} counterparty commitment tx due to broadcast of revoked counterparty commitment transaction, waiting for confirmation (at height {})", log_bytes!(htlc.payment_hash.0), $commitment_tx, height + ANTI_REORG_DELAY - 1);
-                                                                       match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
-                                                                               hash_map::Entry::Occupied(mut entry) => {
-                                                                                       let e = entry.get_mut();
-                                                                                       e.retain(|ref event| {
-                                                                                               match **event {
-                                                                                                       OnchainEvent::HTLCUpdate { ref htlc_update } => {
-                                                                                                               return htlc_update.0 != **source
-                                                                                                       },
-                                                                                                       _ => true
-                                                                                               }
-                                                                                       });
-                                                                                       e.push(OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())});
-                                                                               }
-                                                                               hash_map::Entry::Vacant(entry) => {
-                                                                                       entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())}]);
+                                                                       self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
+                                                                               if entry.height != height { return true; }
+                                                                               match entry.event {
+                                                                                        OnchainEvent::HTLCUpdate { ref htlc_update } => {
+                                                                                                htlc_update.0 != **source
+                                                                                        },
+                                                                                        _ => true,
                                                                                }
-                                                                       }
+                                                                       });
+                                                                       let entry = OnchainEventEntry {
+                                                                               txid: *$txid,
+                                                                               height,
+                                                                               event: OnchainEvent::HTLCUpdate {
+                                                                                       htlc_update: ((**source).clone(), htlc.payment_hash.clone())
+                                                                               },
+                                                                       };
+                                                                       log_info!(logger, "Failing HTLC with payment_hash {} from {} counterparty commitment tx due to broadcast of revoked counterparty commitment transaction, waiting for confirmation (at height {})", log_bytes!(htlc.payment_hash.0), $commitment_tx, entry.confirmation_threshold());
+                                                                       self.onchain_events_awaiting_threshold_conf.push(entry);
                                                                }
                                                        }
                                                }
@@ -1703,23 +1815,22 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                                                        }
                                                                }
                                                                log_trace!(logger, "Failing HTLC with payment_hash {} from {} counterparty commitment tx due to broadcast of counterparty commitment transaction", log_bytes!(htlc.payment_hash.0), $commitment_tx);
-                                                               match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
-                                                                       hash_map::Entry::Occupied(mut entry) => {
-                                                                               let e = entry.get_mut();
-                                                                               e.retain(|ref event| {
-                                                                                       match **event {
-                                                                                               OnchainEvent::HTLCUpdate { ref htlc_update } => {
-                                                                                                       return htlc_update.0 != **source
-                                                                                               },
-                                                                                               _ => true
-                                                                                       }
-                                                                               });
-                                                                               e.push(OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())});
+                                                               self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
+                                                                       if entry.height != height { return true; }
+                                                                       match entry.event {
+                                                                                OnchainEvent::HTLCUpdate { ref htlc_update } => {
+                                                                                        htlc_update.0 != **source
+                                                                                },
+                                                                                _ => true,
                                                                        }
-                                                                       hash_map::Entry::Vacant(entry) => {
-                                                                               entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())}]);
-                                                                       }
-                                                               }
+                                                               });
+                                                               self.onchain_events_awaiting_threshold_conf.push(OnchainEventEntry {
+                                                                       txid: *$txid,
+                                                                       height,
+                                                                       event: OnchainEvent::HTLCUpdate {
+                                                                               htlc_update: ((**source).clone(), htlc.payment_hash.clone())
+                                                                       },
+                                                               });
                                                        }
                                                }
                                        }
@@ -1784,7 +1895,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
        }
 
        /// Attempts to claim a counterparty HTLC-Success/HTLC-Timeout's outputs using the revocation key
-       fn check_spend_counterparty_htlc<L: Deref>(&mut self, tx: &Transaction, commitment_number: u64, height: u32, logger: &L) -> (Vec<ClaimRequest>, Option<(Txid, Vec<(u32, TxOut)>)>) where L::Target: Logger {
+       fn check_spend_counterparty_htlc<L: Deref>(&mut self, tx: &Transaction, commitment_number: u64, height: u32, logger: &L) -> (Vec<ClaimRequest>, Option<TransactionOutputs>) where L::Target: Logger {
                let htlc_txid = tx.txid();
                if tx.input.len() != 1 || tx.output.len() != 1 || tx.input[0].witness.len() != 5 {
                        return (Vec::new(), None)
@@ -1821,7 +1932,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 
                for &(ref htlc, _, _) in holder_tx.htlc_outputs.iter() {
                        if let Some(transaction_output_index) = htlc.transaction_output_index {
-                               claim_requests.push(ClaimRequest { absolute_timelock: ::std::u32::MAX, aggregable: false, outpoint: BitcoinOutPoint { txid: holder_tx.txid, vout: transaction_output_index as u32 },
+                               claim_requests.push(ClaimRequest { absolute_timelock: ::core::u32::MAX, aggregable: false, outpoint: BitcoinOutPoint { txid: holder_tx.txid, vout: transaction_output_index as u32 },
                                        witness_data: InputMaterial::HolderHTLC {
                                                preimage: if !htlc.offered {
                                                                if let Some(preimage) = self.payment_preimages.get(&htlc.payment_hash) {
@@ -1853,31 +1964,29 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
        /// Attempts to claim any claimable HTLCs in a commitment transaction which was not (yet)
        /// revoked using data in holder_claimable_outpoints.
        /// Should not be used if check_spend_revoked_transaction succeeds.
-       fn check_spend_holder_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> (Vec<ClaimRequest>, (Txid, Vec<(u32, TxOut)>)) where L::Target: Logger {
+       fn check_spend_holder_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> (Vec<ClaimRequest>, TransactionOutputs) where L::Target: Logger {
                let commitment_txid = tx.txid();
                let mut claim_requests = Vec::new();
                let mut watch_outputs = Vec::new();
 
                macro_rules! wait_threshold_conf {
-                       ($height: expr, $source: expr, $commitment_tx: expr, $payment_hash: expr) => {
-                               log_trace!(logger, "Failing HTLC with payment_hash {} from {} holder commitment tx due to broadcast of transaction, waiting confirmation (at height{})", log_bytes!($payment_hash.0), $commitment_tx, height + ANTI_REORG_DELAY - 1);
-                               match self.onchain_events_waiting_threshold_conf.entry($height + ANTI_REORG_DELAY - 1) {
-                                       hash_map::Entry::Occupied(mut entry) => {
-                                               let e = entry.get_mut();
-                                               e.retain(|ref event| {
-                                                       match **event {
-                                                               OnchainEvent::HTLCUpdate { ref htlc_update } => {
-                                                                       return htlc_update.0 != $source
-                                                               },
-                                                               _ => true
-                                                       }
-                                               });
-                                               e.push(OnchainEvent::HTLCUpdate { htlc_update: ($source, $payment_hash)});
-                                       }
-                                       hash_map::Entry::Vacant(entry) => {
-                                               entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: ($source, $payment_hash)}]);
+                       ($source: expr, $commitment_tx: expr, $payment_hash: expr) => {
+                               self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
+                                       if entry.height != height { return true; }
+                                       match entry.event {
+                                                OnchainEvent::HTLCUpdate { ref htlc_update } => {
+                                                        htlc_update.0 != $source
+                                                },
+                                                _ => true,
                                        }
-                               }
+                               });
+                               let entry = OnchainEventEntry {
+                                       txid: commitment_txid,
+                                       height,
+                                       event: OnchainEvent::HTLCUpdate { htlc_update: ($source, $payment_hash) },
+                               };
+                               log_trace!(logger, "Failing HTLC with payment_hash {} from {} holder commitment tx due to broadcast of transaction, waiting confirmation (at height{})", log_bytes!($payment_hash.0), $commitment_tx, entry.confirmation_threshold());
+                               self.onchain_events_awaiting_threshold_conf.push(entry);
                        }
                }
 
@@ -1913,7 +2022,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                for &(ref htlc, _, ref source) in &$holder_tx.htlc_outputs {
                                        if htlc.transaction_output_index.is_none() {
                                                if let &Some(ref source) = source {
-                                                       wait_threshold_conf!(height, source.clone(), "lastest", htlc.payment_hash.clone());
+                                                       wait_threshold_conf!(source.clone(), "lastest", htlc.payment_hash.clone());
                                                }
                                        }
                                }
@@ -1978,10 +2087,58 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                return res
        }
 
-       pub fn block_connected<B: Deref, F: Deref, L: Deref>(&mut self, header: &BlockHeader, txdata: &TransactionData, height: u32, broadcaster: B, fee_estimator: F, logger: L)-> Vec<(Txid, Vec<(u32, TxOut)>)>
+       pub fn block_connected<B: Deref, F: Deref, L: Deref>(&mut self, header: &BlockHeader, txdata: &TransactionData, height: u32, broadcaster: B, fee_estimator: F, logger: L) -> Vec<TransactionOutputs>
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator,
                                        L::Target: Logger,
+       {
+               let block_hash = header.block_hash();
+               log_trace!(logger, "New best block {} at height {}", block_hash, height);
+               self.best_block = BestBlock::new(block_hash, height);
+
+               self.transactions_confirmed(header, txdata, height, broadcaster, fee_estimator, logger)
+       }
+
+       fn best_block_updated<B: Deref, F: Deref, L: Deref>(
+               &mut self,
+               header: &BlockHeader,
+               height: u32,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) -> Vec<TransactionOutputs>
+       where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
+       {
+               let block_hash = header.block_hash();
+               log_trace!(logger, "New best block {} at height {}", block_hash, height);
+
+               if height > self.best_block.height() {
+                       self.best_block = BestBlock::new(block_hash, height);
+                       self.block_confirmed(height, vec![], vec![], vec![], broadcaster, fee_estimator, logger)
+               } else {
+                       self.best_block = BestBlock::new(block_hash, height);
+                       self.onchain_events_awaiting_threshold_conf.retain(|ref entry| entry.height <= height);
+                       self.onchain_tx_handler.block_disconnected(height + 1, broadcaster, fee_estimator, logger);
+                       Vec::new()
+               }
+       }
+
+       fn transactions_confirmed<B: Deref, F: Deref, L: Deref>(
+               &mut self,
+               header: &BlockHeader,
+               txdata: &TransactionData,
+               height: u32,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) -> Vec<TransactionOutputs>
+       where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
        {
                let txn_matched = self.filter_block(txdata);
                for tx in &txn_matched {
@@ -2037,11 +2194,28 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 
                        self.is_paying_spendable_output(&tx, height, &logger);
                }
+
+               self.block_confirmed(height, txn_matched, watch_outputs, claimable_outpoints, broadcaster, fee_estimator, logger)
+       }
+
+       fn block_confirmed<B: Deref, F: Deref, L: Deref>(
+               &mut self,
+               height: u32,
+               txn_matched: Vec<&Transaction>,
+               mut watch_outputs: Vec<TransactionOutputs>,
+               mut claimable_outpoints: Vec<ClaimRequest>,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) -> Vec<TransactionOutputs>
+       where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
+       {
                let should_broadcast = self.would_broadcast_at_height(height, &logger);
                if should_broadcast {
                        claimable_outpoints.push(ClaimRequest { absolute_timelock: height, aggregable: false, outpoint: BitcoinOutPoint { txid: self.funding_info.0.txid.clone(), vout: self.funding_info.0.index as u32 }, witness_data: InputMaterial::Funding { funding_redeemscript: self.funding_redeemscript.clone() }});
-               }
-               if should_broadcast {
                        self.pending_monitor_events.push(MonitorEvent::CommitmentTxBroadcasted(self.funding_info.0));
                        let commitment_tx = self.onchain_tx_handler.get_fully_signed_holder_tx(&self.funding_redeemscript);
                        self.holder_tx_signed = true;
@@ -2052,29 +2226,68 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                        }
                        claimable_outpoints.append(&mut new_outpoints);
                }
-               if let Some(events) = self.onchain_events_waiting_threshold_conf.remove(&height) {
-                       for ev in events {
-                               match ev {
-                                       OnchainEvent::HTLCUpdate { htlc_update } => {
-                                               log_trace!(logger, "HTLC {} failure update has got enough confirmations to be passed upstream", log_bytes!((htlc_update.1).0));
-                                               self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
-                                                       payment_hash: htlc_update.1,
-                                                       payment_preimage: None,
-                                                       source: htlc_update.0,
-                                               }));
-                                       },
-                                       OnchainEvent::MaturingOutput { descriptor } => {
-                                               log_trace!(logger, "Descriptor {} has got enough confirmations to be passed upstream", log_spendable!(descriptor));
-                                               self.pending_events.push(Event::SpendableOutputs {
-                                                       outputs: vec![descriptor]
-                                               });
+
+               // Find which on-chain events have reached their confirmation threshold.
+               let onchain_events_awaiting_threshold_conf =
+                       self.onchain_events_awaiting_threshold_conf.drain(..).collect::<Vec<_>>();
+               let mut onchain_events_reaching_threshold_conf = Vec::new();
+               for entry in onchain_events_awaiting_threshold_conf {
+                       if entry.has_reached_confirmation_threshold(height) {
+                               onchain_events_reaching_threshold_conf.push(entry);
+                       } else {
+                               self.onchain_events_awaiting_threshold_conf.push(entry);
+                       }
+               }
+
+               // Used to check for duplicate HTLC resolutions.
+               #[cfg(debug_assertions)]
+               let unmatured_htlcs: Vec<_> = self.onchain_events_awaiting_threshold_conf
+                       .iter()
+                       .filter_map(|entry| match &entry.event {
+                               OnchainEvent::HTLCUpdate { htlc_update } => Some(htlc_update.0.clone()),
+                               OnchainEvent::MaturingOutput { .. } => None,
+                       })
+                       .collect();
+               #[cfg(debug_assertions)]
+               let mut matured_htlcs = Vec::new();
+
+               // Produce actionable events from on-chain events having reached their threshold.
+               for entry in onchain_events_reaching_threshold_conf.drain(..) {
+                       match entry.event {
+                               OnchainEvent::HTLCUpdate { htlc_update } => {
+                                       // Check for duplicate HTLC resolutions.
+                                       #[cfg(debug_assertions)]
+                                       {
+                                               debug_assert!(
+                                                       unmatured_htlcs.iter().find(|&htlc| htlc == &htlc_update.0).is_none(),
+                                                       "An unmature HTLC transaction conflicts with a maturing one; failed to \
+                                                        call either transaction_unconfirmed for the conflicting transaction \
+                                                        or block_disconnected for a block containing it.");
+                                               debug_assert!(
+                                                       matured_htlcs.iter().find(|&htlc| htlc == &htlc_update.0).is_none(),
+                                                       "A matured HTLC transaction conflicts with a maturing one; failed to \
+                                                        call either transaction_unconfirmed for the conflicting transaction \
+                                                        or block_disconnected for a block containing it.");
+                                               matured_htlcs.push(htlc_update.0.clone());
                                        }
+
+                                       log_trace!(logger, "HTLC {} failure update has got enough confirmations to be passed upstream", log_bytes!((htlc_update.1).0));
+                                       self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
+                                               payment_hash: htlc_update.1,
+                                               payment_preimage: None,
+                                               source: htlc_update.0,
+                                       }));
+                               },
+                               OnchainEvent::MaturingOutput { descriptor } => {
+                                       log_trace!(logger, "Descriptor {} has got enough confirmations to be passed upstream", log_spendable!(descriptor));
+                                       self.pending_events.push(Event::SpendableOutputs {
+                                               outputs: vec![descriptor]
+                                       });
                                }
                        }
                }
 
                self.onchain_tx_handler.update_claims_view(&txn_matched, claimable_outpoints, Some(height), &&*broadcaster, &&*fee_estimator, &&*logger);
-               self.last_block_hash = block_hash;
 
                // Determine new outputs to watch by comparing against previously known outputs to watch,
                // updating the latter in the process.
@@ -2106,15 +2319,29 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
        {
                log_trace!(logger, "Block {} at height {} disconnected", header.block_hash(), height);
 
-               if let Some(_) = self.onchain_events_waiting_threshold_conf.remove(&(height + ANTI_REORG_DELAY - 1)) {
-                       //We may discard:
-                       //- htlc update there as failure-trigger tx (revoked commitment tx, non-revoked commitment tx, HTLC-timeout tx) has been disconnected
-                       //- maturing spendable output has transaction paying us has been disconnected
-               }
+               //We may discard:
+               //- htlc update there as failure-trigger tx (revoked commitment tx, non-revoked commitment tx, HTLC-timeout tx) has been disconnected
+               //- maturing spendable output has transaction paying us has been disconnected
+               self.onchain_events_awaiting_threshold_conf.retain(|ref entry| entry.height < height);
 
                self.onchain_tx_handler.block_disconnected(height, broadcaster, fee_estimator, logger);
 
-               self.last_block_hash = header.prev_blockhash;
+               self.best_block = BestBlock::new(header.prev_blockhash, height - 1);
+       }
+
+       fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
+               &mut self,
+               txid: &Txid,
+               broadcaster: B,
+               fee_estimator: F,
+               logger: L,
+       ) where
+               B::Target: BroadcasterInterface,
+               F::Target: FeeEstimator,
+               L::Target: Logger,
+       {
+               self.onchain_events_awaiting_threshold_conf.retain(|ref entry| entry.txid != *txid);
+               self.onchain_tx_handler.transaction_unconfirmed(txid, broadcaster, fee_estimator, logger);
        }
 
        /// Filters a block's `txdata` for transactions spending watched outputs or for any child
@@ -2342,24 +2569,22 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                                }));
                                        }
                                } else {
-                                       log_info!(logger, "Failing HTLC with payment_hash {} timeout by a spend tx, waiting for confirmation (at height{})", log_bytes!(payment_hash.0), height + ANTI_REORG_DELAY - 1);
-                                       match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
-                                               hash_map::Entry::Occupied(mut entry) => {
-                                                       let e = entry.get_mut();
-                                                       e.retain(|ref event| {
-                                                               match **event {
-                                                                       OnchainEvent::HTLCUpdate { ref htlc_update } => {
-                                                                               return htlc_update.0 != source
-                                                                       },
-                                                                       _ => true
-                                                               }
-                                                       });
-                                                       e.push(OnchainEvent::HTLCUpdate { htlc_update: (source, payment_hash)});
+                                       self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
+                                               if entry.height != height { return true; }
+                                               match entry.event {
+                                                        OnchainEvent::HTLCUpdate { ref htlc_update } => {
+                                                                htlc_update.0 != source
+                                                        },
+                                                        _ => true,
                                                }
-                                               hash_map::Entry::Vacant(entry) => {
-                                                       entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: (source, payment_hash)}]);
-                                               }
-                                       }
+                                       });
+                                       let entry = OnchainEventEntry {
+                                               txid: tx.txid(),
+                                               height,
+                                               event: OnchainEvent::HTLCUpdate { htlc_update: (source, payment_hash) },
+                                       };
+                                       log_info!(logger, "Failing HTLC with payment_hash {} timeout by a spend tx, waiting for confirmation (at height{})", log_bytes!(payment_hash.0), entry.confirmation_threshold());
+                                       self.onchain_events_awaiting_threshold_conf.push(entry);
                                }
                        }
                }
@@ -2369,7 +2594,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
        fn is_paying_spendable_output<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) where L::Target: Logger {
                let mut spendable_output = None;
                for (i, outp) in tx.output.iter().enumerate() { // There is max one spendable output for any channel tx, including ones generated by us
-                       if i > ::std::u16::MAX as usize {
+                       if i > ::core::u16::MAX as usize {
                                // While it is possible that an output exists on chain which is greater than the
                                // 2^16th output in a given transaction, this is only possible if the output is not
                                // in a lightning transaction and was instead placed there by some third party who
@@ -2418,16 +2643,13 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                        }
                }
                if let Some(spendable_output) = spendable_output {
-                       log_trace!(logger, "Maturing {} until {}", log_spendable!(spendable_output), height + ANTI_REORG_DELAY - 1);
-                       match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
-                               hash_map::Entry::Occupied(mut entry) => {
-                                       let e = entry.get_mut();
-                                       e.push(OnchainEvent::MaturingOutput { descriptor: spendable_output });
-                               }
-                               hash_map::Entry::Vacant(entry) => {
-                                       entry.insert(vec![OnchainEvent::MaturingOutput { descriptor: spendable_output }]);
-                               }
-                       }
+                       let entry = OnchainEventEntry {
+                               txid: tx.txid(),
+                               height: height,
+                               event: OnchainEvent::MaturingOutput { descriptor: spendable_output.clone() },
+                       };
+                       log_trace!(logger, "Maturing {} until {}", log_spendable!(spendable_output), entry.confirmation_threshold());
+                       self.onchain_events_awaiting_threshold_conf.push(entry);
                }
        }
 }
@@ -2443,18 +2665,15 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 /// transaction and losing money. This is a risk because previous channel states
 /// are toxic, so it's important that whatever channel state is persisted is
 /// kept up-to-date.
-pub trait Persist<ChannelSigner: Sign>: Send + Sync {
+pub trait Persist<ChannelSigner: Sign> {
        /// Persist a new channel's data. The data can be stored any way you want, but
        /// the identifier provided by Rust-Lightning 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. See the `Persist` trait documentation for more details.
        ///
-       /// See [`ChannelMonitor::serialize_for_disk`] for writing out a `ChannelMonitor`,
+       /// See [`ChannelMonitor::write`] for writing out a `ChannelMonitor`,
        /// and [`ChannelMonitorUpdateErr`] for requirements when returning errors.
-       ///
-       /// [`ChannelMonitor::serialize_for_disk`]: struct.ChannelMonitor.html#method.serialize_for_disk
-       /// [`ChannelMonitorUpdateErr`]: enum.ChannelMonitorUpdateErr.html
        fn persist_new_channel(&self, id: OutPoint, data: &ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr>;
 
        /// Update one channel's data. The provided `ChannelMonitor` has already
@@ -2476,14 +2695,9 @@ pub trait Persist<ChannelSigner: Sign>: Send + Sync {
        /// them in batches. The size of each monitor grows `O(number of state updates)`
        /// whereas updates are small and `O(1)`.
        ///
-       /// See [`ChannelMonitor::serialize_for_disk`] for writing out a `ChannelMonitor`,
+       /// See [`ChannelMonitor::write`] for writing out a `ChannelMonitor`,
        /// [`ChannelMonitorUpdate::write`] for writing out an update, and
        /// [`ChannelMonitorUpdateErr`] for requirements when returning errors.
-       ///
-       /// [`ChannelMonitor::update_monitor`]: struct.ChannelMonitor.html#impl-1
-       /// [`ChannelMonitor::serialize_for_disk`]: struct.ChannelMonitor.html#method.serialize_for_disk
-       /// [`ChannelMonitorUpdate::write`]: struct.ChannelMonitorUpdate.html#method.write
-       /// [`ChannelMonitorUpdateErr`]: enum.ChannelMonitorUpdateErr.html
        fn update_persisted_channel(&self, id: OutPoint, update: &ChannelMonitorUpdate, data: &ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr>;
 }
 
@@ -2503,6 +2717,29 @@ where
        }
 }
 
+impl<Signer: Sign, T: Deref, F: Deref, L: Deref> chain::Confirm for (ChannelMonitor<Signer>, T, F, L)
+where
+       T::Target: BroadcasterInterface,
+       F::Target: FeeEstimator,
+       L::Target: Logger,
+{
+       fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
+               self.0.transactions_confirmed(header, txdata, height, &*self.1, &*self.2, &*self.3);
+       }
+
+       fn transaction_unconfirmed(&self, txid: &Txid) {
+               self.0.transaction_unconfirmed(txid, &*self.1, &*self.2, &*self.3);
+       }
+
+       fn best_block_updated(&self, header: &BlockHeader, height: u32) {
+               self.0.best_block_updated(header, height, &*self.1, &*self.2, &*self.3);
+       }
+
+       fn get_relevant_txids(&self) -> Vec<Txid> {
+               self.0.get_relevant_txids()
+       }
+}
+
 const MAX_ALLOC_SIZE: usize = 64*1024;
 
 impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
@@ -2698,34 +2935,30 @@ impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
                        }
                }
 
-               let last_block_hash: BlockHash = Readable::read(reader)?;
+               let best_block = BestBlock::new(Readable::read(reader)?, Readable::read(reader)?);
 
                let waiting_threshold_conf_len: u64 = Readable::read(reader)?;
-               let mut onchain_events_waiting_threshold_conf = HashMap::with_capacity(cmp::min(waiting_threshold_conf_len as usize, MAX_ALLOC_SIZE / 128));
+               let mut onchain_events_awaiting_threshold_conf = Vec::with_capacity(cmp::min(waiting_threshold_conf_len as usize, MAX_ALLOC_SIZE / 128));
                for _ in 0..waiting_threshold_conf_len {
-                       let height_target = Readable::read(reader)?;
-                       let events_len: u64 = Readable::read(reader)?;
-                       let mut events = Vec::with_capacity(cmp::min(events_len as usize, MAX_ALLOC_SIZE / 128));
-                       for _ in 0..events_len {
-                               let ev = match <u8 as Readable>::read(reader)? {
-                                       0 => {
-                                               let htlc_source = Readable::read(reader)?;
-                                               let hash = Readable::read(reader)?;
-                                               OnchainEvent::HTLCUpdate {
-                                                       htlc_update: (htlc_source, hash)
-                                               }
-                                       },
-                                       1 => {
-                                               let descriptor = Readable::read(reader)?;
-                                               OnchainEvent::MaturingOutput {
-                                                       descriptor
-                                               }
-                                       },
-                                       _ => return Err(DecodeError::InvalidValue),
-                               };
-                               events.push(ev);
-                       }
-                       onchain_events_waiting_threshold_conf.insert(height_target, events);
+                       let txid = Readable::read(reader)?;
+                       let height = Readable::read(reader)?;
+                       let event = match <u8 as Readable>::read(reader)? {
+                               0 => {
+                                       let htlc_source = Readable::read(reader)?;
+                                       let hash = Readable::read(reader)?;
+                                       OnchainEvent::HTLCUpdate {
+                                               htlc_update: (htlc_source, hash)
+                                       }
+                               },
+                               1 => {
+                                       let descriptor = Readable::read(reader)?;
+                                       OnchainEvent::MaturingOutput {
+                                               descriptor
+                                       }
+                               },
+                               _ => return Err(DecodeError::InvalidValue),
+                       };
+                       onchain_events_awaiting_threshold_conf.push(OnchainEventEntry { txid, height, event });
                }
 
                let outputs_to_watch_len: u64 = Readable::read(reader)?;
@@ -2749,7 +2982,7 @@ impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
 
-               Ok((last_block_hash.clone(), ChannelMonitor {
+               Ok((best_block.block_hash(), ChannelMonitor {
                        inner: Mutex::new(ChannelMonitorImpl {
                                latest_update_id,
                                commitment_transaction_number_obscure_factor,
@@ -2786,7 +3019,7 @@ impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
                                pending_monitor_events,
                                pending_events,
 
-                               onchain_events_waiting_threshold_conf,
+                               onchain_events_awaiting_threshold_conf,
                                outputs_to_watch,
 
                                onchain_tx_handler,
@@ -2794,7 +3027,8 @@ impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
                                lockdown_from_offchain,
                                holder_tx_signed,
 
-                               last_block_hash,
+                               best_block,
+
                                secp_ctx,
                        }),
                }))
@@ -2803,7 +3037,6 @@ impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
 
 #[cfg(test)]
 mod tests {
-       use bitcoin::blockdata::constants::genesis_block;
        use bitcoin::blockdata::script::{Script, Builder};
        use bitcoin::blockdata::opcodes;
        use bitcoin::blockdata::transaction::{Transaction, TxIn, TxOut, SigHashType};
@@ -2817,7 +3050,8 @@ mod tests {
        use hex;
        use chain::channelmonitor::ChannelMonitor;
        use chain::transaction::OutPoint;
-       use ln::channelmanager::{PaymentPreimage, PaymentHash};
+       use ln::{PaymentPreimage, PaymentHash};
+       use ln::channelmanager::BestBlock;
        use ln::onchaintx::{OnchainTxHandler, InputDescriptors};
        use ln::chan_utils;
        use ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, ChannelTransactionParameters, HolderCommitmentTransaction, CounterpartyChannelTransactionParameters};
@@ -2913,13 +3147,13 @@ mod tests {
                };
                // Prune with one old state and a holder commitment tx holding a few overlaps with the
                // old state.
-               let last_block_hash = genesis_block(Network::Testnet).block_hash();
+               let best_block = BestBlock::from_genesis(Network::Testnet);
                let monitor = ChannelMonitor::new(Secp256k1::new(), keys,
                                                  &PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap()), 0, &Script::new(),
                                                  (OutPoint { txid: Txid::from_slice(&[43; 32]).unwrap(), index: 0 }, Script::new()),
                                                  &channel_parameters,
                                                  Script::new(), 46, 0,
-                                                 HolderCommitmentTransaction::dummy(), last_block_hash);
+                                                 HolderCommitmentTransaction::dummy(), best_block);
 
                monitor.provide_latest_holder_commitment_tx(HolderCommitmentTransaction::dummy(), preimages_to_holder_htlcs!(preimages[0..10])).unwrap();
                let dummy_txid = dummy_tx.txid();