[rust-lightning] / lightning / src / chain / onchaintx.rs

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

//! The logic to build claims and bump in-flight transactions until confirmations.
//!
//! OnchainTxHandler objects are fully-part of ChannelMonitor and encapsulates all
//! building, tracking, bumping and notifications functions.

use bitcoin::PackedLockTime;
use bitcoin::blockdata::transaction::Transaction;
use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
use bitcoin::blockdata::script::Script;
use bitcoin::hashes::{Hash, HashEngine};
use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hash_types::{Txid, BlockHash};
use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
use bitcoin::secp256k1;

use crate::sign::{ChannelSigner, EntropySource, SignerProvider};
use crate::ln::msgs::DecodeError;
use crate::ln::PaymentPreimage;
use crate::ln::chan_utils::{self, ChannelTransactionParameters, HTLCOutputInCommitment, HolderCommitmentTransaction};
use crate::chain::ClaimId;
use crate::chain::chaininterface::{ConfirmationTarget, FeeEstimator, BroadcasterInterface, LowerBoundedFeeEstimator};
use crate::chain::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER};
use crate::sign::WriteableEcdsaChannelSigner;
use crate::chain::package::{PackageSolvingData, PackageTemplate};
use crate::util::logger::Logger;
use crate::util::ser::{Readable, ReadableArgs, MaybeReadable, UpgradableRequired, Writer, Writeable, VecWriter};

use crate::io;
use crate::prelude::*;
use alloc::collections::BTreeMap;
use core::cmp;
use core::ops::Deref;
use core::mem::replace;
use core::mem::swap;
use crate::ln::features::ChannelTypeFeatures;

const MAX_ALLOC_SIZE: usize = 64*1024;

/// 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, Eq)]
struct OnchainEventEntry {
        txid: Txid,
        height: u32,
        block_hash: Option<BlockHash>, // Added as optional, will be filled in for any entry generated on 0.0.113 or after
        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()
        }
}

/// Events for claims the [`OnchainTxHandler`] has generated. Once the events are considered safe
/// from a chain reorg, the [`OnchainTxHandler`] will act accordingly.
#[derive(PartialEq, Eq)]
enum OnchainEvent {
        /// A pending request has been claimed by a transaction spending the exact same set of outpoints
        /// as the request. This claim can either be ours or from the counterparty. Once the claiming
        /// transaction has met [`ANTI_REORG_DELAY`] confirmations, we consider it final and remove the
        /// pending request.
        Claim {
                claim_id: ClaimId,
        },
        /// The counterparty has claimed an outpoint from one of our pending requests through a
        /// different transaction than ours. If our transaction was attempting to claim multiple
        /// outputs, we need to drop the outpoint claimed by the counterparty and regenerate a new claim
        /// transaction for ourselves. We keep tracking, separately, the outpoint claimed by the
        /// counterparty up to [`ANTI_REORG_DELAY`] confirmations to ensure we attempt to re-claim it
        /// if the counterparty's claim is reorged from the chain.
        ContentiousOutpoint {
                package: PackageTemplate,
        }
}

impl Writeable for OnchainEventEntry {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                write_tlv_fields!(writer, {
                        (0, self.txid, required),
                        (1, self.block_hash, option),
                        (2, self.height, required),
                        (4, self.event, required),
                });
                Ok(())
        }
}

impl MaybeReadable for OnchainEventEntry {
        fn read<R: io::Read>(reader: &mut R) -> Result<Option<Self>, DecodeError> {
                let mut txid = Txid::all_zeros();
                let mut height = 0;
                let mut block_hash = None;
                let mut event = UpgradableRequired(None);
                read_tlv_fields!(reader, {
                        (0, txid, required),
                        (1, block_hash, option),
                        (2, height, required),
                        (4, event, upgradable_required),
                });
                Ok(Some(Self { txid, height, block_hash, event: _init_tlv_based_struct_field!(event, upgradable_required) }))
        }
}

impl_writeable_tlv_based_enum_upgradable!(OnchainEvent,
        (0, Claim) => {
                (0, claim_id, required),
        },
        (1, ContentiousOutpoint) => {
                (0, package, required),
        },
);

impl Readable for Option<Vec<Option<(usize, Signature)>>> {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                match Readable::read(reader)? {
                        0u8 => Ok(None),
                        1u8 => {
                                let vlen: u64 = Readable::read(reader)?;
                                let mut ret = Vec::with_capacity(cmp::min(vlen as usize, MAX_ALLOC_SIZE / ::core::mem::size_of::<Option<(usize, Signature)>>()));
                                for _ in 0..vlen {
                                        ret.push(match Readable::read(reader)? {
                                                0u8 => None,
                                                1u8 => Some((<u64 as Readable>::read(reader)? as usize, Readable::read(reader)?)),
                                                _ => return Err(DecodeError::InvalidValue)
                                        });
                                }
                                Ok(Some(ret))
                        },
                        _ => Err(DecodeError::InvalidValue),
                }
        }
}

impl Writeable for Option<Vec<Option<(usize, Signature)>>> {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                match self {
                        &Some(ref vec) => {
                                1u8.write(writer)?;
                                (vec.len() as u64).write(writer)?;
                                for opt in vec.iter() {
                                        match opt {
                                                &Some((ref idx, ref sig)) => {
                                                        1u8.write(writer)?;
                                                        (*idx as u64).write(writer)?;
                                                        sig.write(writer)?;
                                                },
                                                &None => 0u8.write(writer)?,
                                        }
                                }
                        },
                        &None => 0u8.write(writer)?,
                }
                Ok(())
        }
}

/// The claim commonly referred to as the pre-signed second-stage HTLC transaction.
pub(crate) struct ExternalHTLCClaim {
        pub(crate) commitment_txid: Txid,
        pub(crate) per_commitment_number: u64,
        pub(crate) htlc: HTLCOutputInCommitment,
        pub(crate) preimage: Option<PaymentPreimage>,
        pub(crate) counterparty_sig: Signature,
}

// Represents the different types of claims for which events are yielded externally to satisfy said
// claims.
pub(crate) enum ClaimEvent {
        /// Event yielded to signal that the commitment transaction fee must be bumped to claim any
        /// encumbered funds and proceed to HTLC resolution, if any HTLCs exist.
        BumpCommitment {
                package_target_feerate_sat_per_1000_weight: u32,
                commitment_tx: Transaction,
                anchor_output_idx: u32,
        },
        /// Event yielded to signal that the commitment transaction has confirmed and its HTLCs must be
        /// resolved by broadcasting a transaction with sufficient fee to claim them.
        BumpHTLC {
                target_feerate_sat_per_1000_weight: u32,
                htlcs: Vec<ExternalHTLCClaim>,
                tx_lock_time: PackedLockTime,
        },
}

/// Represents the different ways an output can be claimed (i.e., spent to an address under our
/// control) onchain.
pub(crate) enum OnchainClaim {
        /// A finalized transaction pending confirmation spending the output to claim.
        Tx(Transaction),
        /// An event yielded externally to signal additional inputs must be added to a transaction
        /// pending confirmation spending the output to claim.
        Event(ClaimEvent),
}

/// OnchainTxHandler receives claiming requests, aggregates them if it's sound, broadcast and
/// do RBF bumping if possible.
pub struct OnchainTxHandler<ChannelSigner: WriteableEcdsaChannelSigner> {
        destination_script: Script,
        holder_commitment: HolderCommitmentTransaction,
        // holder_htlc_sigs and prev_holder_htlc_sigs are in the order as they appear in the commitment
        // transaction outputs (hence the Option<>s inside the Vec). The first usize is the index in
        // the set of HTLCs in the HolderCommitmentTransaction.
        holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,
        prev_holder_commitment: Option<HolderCommitmentTransaction>,
        prev_holder_htlc_sigs: Option<Vec<Option<(usize, Signature)>>>,

        pub(super) signer: ChannelSigner,
        pub(crate) channel_transaction_parameters: ChannelTransactionParameters,

        // Used to track claiming requests. If claim tx doesn't confirm before height timer expiration we need to bump
        // it (RBF or CPFP). If an input has been part of an aggregate tx at first claim try, we need to keep it within
        // another bumped aggregate tx to comply with RBF rules. We may have multiple claiming txn in the flight for the
        // same set of outpoints. One of the outpoints may be spent by a transaction not issued by us. That's why at
        // block connection we scan all inputs and if any of them is among a set of a claiming request we test for set
        // equality between spending transaction and claim request. If true, it means transaction was one our claiming one
        // after a security delay of 6 blocks we remove pending claim request. If false, it means transaction wasn't and
        // we need to regenerate new claim request with reduced set of still-claimable outpoints.
        // Key is identifier of the pending claim request, i.e the txid of the initial claiming transaction generated by
        // us and is immutable until all outpoint of the claimable set are post-anti-reorg-delay solved.
        // Entry is cache of elements need to generate a bumped claiming transaction (see ClaimTxBumpMaterial)
        #[cfg(test)] // Used in functional_test to verify sanitization
        pub(crate) pending_claim_requests: HashMap<ClaimId, PackageTemplate>,
        #[cfg(not(test))]
        pending_claim_requests: HashMap<ClaimId, PackageTemplate>,

        // Used to track external events that need to be forwarded to the `ChainMonitor`. This `Vec`
        // essentially acts as an insertion-ordered `HashMap` – there should only ever be one occurrence
        // of a `ClaimId`, which tracks its latest `ClaimEvent`, i.e., if a pending claim exists, and
        // a new block has been connected, resulting in a new claim, the previous will be replaced with
        // the new.
        //
        // These external events may be generated in the following cases:
        //      - A channel has been force closed by broadcasting the holder's latest commitment transaction
        //      - A block being connected/disconnected
        //      - Learning the preimage for an HTLC we can claim onchain
        pending_claim_events: Vec<(ClaimId, ClaimEvent)>,

        // Used to link outpoints claimed in a connected block to a pending claim request. The keys
        // represent the outpoints that our `ChannelMonitor` has detected we have keys/scripts to
        // claim. The values track the pending claim request identifier and the initial confirmation
        // block height, and are immutable until the outpoint has enough confirmations to meet our
        // [`ANTI_REORG_DELAY`]. The initial confirmation block height is used to remove the entry if
        // the block gets disconnected.
        #[cfg(test)] // Used in functional_test to verify sanitization
        pub claimable_outpoints: HashMap<BitcoinOutPoint, (ClaimId, u32)>,
        #[cfg(not(test))]
        claimable_outpoints: HashMap<BitcoinOutPoint, (ClaimId, u32)>,

        locktimed_packages: BTreeMap<u32, Vec<PackageTemplate>>,

        onchain_events_awaiting_threshold_conf: Vec<OnchainEventEntry>,

        pub(super) secp_ctx: Secp256k1<secp256k1::All>,
}

impl<ChannelSigner: WriteableEcdsaChannelSigner> PartialEq for OnchainTxHandler<ChannelSigner> {
        fn eq(&self, other: &Self) -> bool {
                // `signer`, `secp_ctx`, and `pending_claim_events` are excluded on purpose.
                self.destination_script == other.destination_script &&
                        self.holder_commitment == other.holder_commitment &&
                        self.holder_htlc_sigs == other.holder_htlc_sigs &&
                        self.prev_holder_commitment == other.prev_holder_commitment &&
                        self.prev_holder_htlc_sigs == other.prev_holder_htlc_sigs &&
                        self.channel_transaction_parameters == other.channel_transaction_parameters &&
                        self.pending_claim_requests == other.pending_claim_requests &&
                        self.claimable_outpoints == other.claimable_outpoints &&
                        self.locktimed_packages == other.locktimed_packages &&
                        self.onchain_events_awaiting_threshold_conf == other.onchain_events_awaiting_threshold_conf
        }
}

const SERIALIZATION_VERSION: u8 = 1;
const MIN_SERIALIZATION_VERSION: u8 = 1;

impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner> {
        pub(crate) fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                write_ver_prefix!(writer, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);

                self.destination_script.write(writer)?;
                self.holder_commitment.write(writer)?;
                self.holder_htlc_sigs.write(writer)?;
                self.prev_holder_commitment.write(writer)?;
                self.prev_holder_htlc_sigs.write(writer)?;

                self.channel_transaction_parameters.write(writer)?;

                let mut key_data = VecWriter(Vec::new());
                self.signer.write(&mut key_data)?;
                assert!(key_data.0.len() < core::usize::MAX);
                assert!(key_data.0.len() < core::u32::MAX as usize);
                (key_data.0.len() as u32).write(writer)?;
                writer.write_all(&key_data.0[..])?;

                writer.write_all(&(self.pending_claim_requests.len() as u64).to_be_bytes())?;
                for (ref ancestor_claim_txid, request) in self.pending_claim_requests.iter() {
                        ancestor_claim_txid.write(writer)?;
                        request.write(writer)?;
                }

                writer.write_all(&(self.claimable_outpoints.len() as u64).to_be_bytes())?;
                for (ref outp, ref claim_and_height) in self.claimable_outpoints.iter() {
                        outp.write(writer)?;
                        claim_and_height.0.write(writer)?;
                        claim_and_height.1.write(writer)?;
                }

                writer.write_all(&(self.locktimed_packages.len() as u64).to_be_bytes())?;
                for (ref locktime, ref packages) in self.locktimed_packages.iter() {
                        locktime.write(writer)?;
                        writer.write_all(&(packages.len() as u64).to_be_bytes())?;
                        for ref package in packages.iter() {
                                package.write(writer)?;
                        }
                }

                writer.write_all(&(self.onchain_events_awaiting_threshold_conf.len() as u64).to_be_bytes())?;
                for ref entry in self.onchain_events_awaiting_threshold_conf.iter() {
                        entry.write(writer)?;
                }

                write_tlv_fields!(writer, {});
                Ok(())
        }
}

impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP, u64, [u8; 32])> for OnchainTxHandler<SP::Signer> {
        fn read<R: io::Read>(reader: &mut R, args: (&'a ES, &'b SP, u64, [u8; 32])) -> Result<Self, DecodeError> {
                let entropy_source = args.0;
                let signer_provider = args.1;
                let channel_value_satoshis = args.2;
                let channel_keys_id = args.3;

                let _ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);

                let destination_script = Readable::read(reader)?;

                let holder_commitment = Readable::read(reader)?;
                let holder_htlc_sigs = Readable::read(reader)?;
                let prev_holder_commitment = Readable::read(reader)?;
                let prev_holder_htlc_sigs = Readable::read(reader)?;

                let channel_parameters = Readable::read(reader)?;

                // Read the serialized signer bytes, but don't deserialize them, as we'll obtain our signer
                // by re-deriving the private key material.
                let keys_len: u32 = Readable::read(reader)?;
                let mut bytes_read = 0;
                while bytes_read != keys_len as usize {
                        // Read 1KB at a time to avoid accidentally allocating 4GB on corrupted channel keys
                        let mut data = [0; 1024];
                        let bytes_to_read = cmp::min(1024, keys_len as usize - bytes_read);
                        let read_slice = &mut data[0..bytes_to_read];
                        reader.read_exact(read_slice)?;
                        bytes_read += bytes_to_read;
                }

                let mut signer = signer_provider.derive_channel_signer(channel_value_satoshis, channel_keys_id);
                signer.provide_channel_parameters(&channel_parameters);

                let pending_claim_requests_len: u64 = Readable::read(reader)?;
                let mut pending_claim_requests = HashMap::with_capacity(cmp::min(pending_claim_requests_len as usize, MAX_ALLOC_SIZE / 128));
                for _ in 0..pending_claim_requests_len {
                        pending_claim_requests.insert(Readable::read(reader)?, Readable::read(reader)?);
                }

                let claimable_outpoints_len: u64 = Readable::read(reader)?;
                let mut claimable_outpoints = HashMap::with_capacity(cmp::min(pending_claim_requests_len as usize, MAX_ALLOC_SIZE / 128));
                for _ in 0..claimable_outpoints_len {
                        let outpoint = Readable::read(reader)?;
                        let ancestor_claim_txid = Readable::read(reader)?;
                        let height = Readable::read(reader)?;
                        claimable_outpoints.insert(outpoint, (ancestor_claim_txid, height));
                }

                let locktimed_packages_len: u64 = Readable::read(reader)?;
                let mut locktimed_packages = BTreeMap::new();
                for _ in 0..locktimed_packages_len {
                        let locktime = Readable::read(reader)?;
                        let packages_len: u64 = Readable::read(reader)?;
                        let mut packages = Vec::with_capacity(cmp::min(packages_len as usize, MAX_ALLOC_SIZE / core::mem::size_of::<PackageTemplate>()));
                        for _ in 0..packages_len {
                                packages.push(Readable::read(reader)?);
                        }
                        locktimed_packages.insert(locktime, packages);
                }

                let waiting_threshold_conf_len: u64 = Readable::read(reader)?;
                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 {
                        if let Some(val) = MaybeReadable::read(reader)? {
                                onchain_events_awaiting_threshold_conf.push(val);
                        }
                }

                read_tlv_fields!(reader, {});

                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());

                Ok(OnchainTxHandler {
                        destination_script,
                        holder_commitment,
                        holder_htlc_sigs,
                        prev_holder_commitment,
                        prev_holder_htlc_sigs,
                        signer,
                        channel_transaction_parameters: channel_parameters,
                        claimable_outpoints,
                        locktimed_packages,
                        pending_claim_requests,
                        onchain_events_awaiting_threshold_conf,
                        pending_claim_events: Vec::new(),
                        secp_ctx,
                })
        }
}

impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner> {
        pub(crate) fn new(destination_script: Script, signer: ChannelSigner, channel_parameters: ChannelTransactionParameters, holder_commitment: HolderCommitmentTransaction, secp_ctx: Secp256k1<secp256k1::All>) -> Self {
                OnchainTxHandler {
                        destination_script,
                        holder_commitment,
                        holder_htlc_sigs: None,
                        prev_holder_commitment: None,
                        prev_holder_htlc_sigs: None,
                        signer,
                        channel_transaction_parameters: channel_parameters,
                        pending_claim_requests: HashMap::new(),
                        claimable_outpoints: HashMap::new(),
                        locktimed_packages: BTreeMap::new(),
                        onchain_events_awaiting_threshold_conf: Vec::new(),
                        pending_claim_events: Vec::new(),
                        secp_ctx,
                }
        }

        pub(crate) fn get_prev_holder_commitment_to_self_value(&self) -> Option<u64> {
                self.prev_holder_commitment.as_ref().map(|commitment| commitment.to_broadcaster_value_sat())
        }

        pub(crate) fn get_cur_holder_commitment_to_self_value(&self) -> u64 {
                self.holder_commitment.to_broadcaster_value_sat()
        }

        pub(crate) fn get_and_clear_pending_claim_events(&mut self) -> Vec<(ClaimId, ClaimEvent)> {
                let mut events = Vec::new();
                swap(&mut events, &mut self.pending_claim_events);
                events
        }

        /// Triggers rebroadcasts/fee-bumps of pending claims from a force-closed channel. This is
        /// crucial in preventing certain classes of pinning attacks, detecting substantial mempool
        /// feerate changes between blocks, and ensuring reliability if broadcasting fails. We recommend
        /// invoking this every 30 seconds, or lower if running in an environment with spotty
        /// connections, like on mobile.
        pub(crate) fn rebroadcast_pending_claims<B: Deref, F: Deref, L: Deref>(
                &mut self, current_height: u32, broadcaster: &B, fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: &L,
        )
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let mut bump_requests = Vec::with_capacity(self.pending_claim_requests.len());
                for (claim_id, request) in self.pending_claim_requests.iter() {
                        let inputs = request.outpoints();
                        log_info!(logger, "Triggering rebroadcast/fee-bump for request with inputs {:?}", inputs);
                        bump_requests.push((*claim_id, request.clone()));
                }
                for (claim_id, request) in bump_requests {
                        self.generate_claim(current_height, &request, false /* force_feerate_bump */, fee_estimator, logger)
                                .map(|(_, new_feerate, claim)| {
                                        let mut bumped_feerate = false;
                                        if let Some(mut_request) = self.pending_claim_requests.get_mut(&claim_id) {
                                                bumped_feerate = request.previous_feerate() > new_feerate;
                                                mut_request.set_feerate(new_feerate);
                                        }
                                        match claim {
                                                OnchainClaim::Tx(tx) => {
                                                        let log_start = if bumped_feerate { "Broadcasting RBF-bumped" } else { "Rebroadcasting" };
                                                        log_info!(logger, "{} onchain {}", log_start, log_tx!(tx));
                                                        broadcaster.broadcast_transactions(&[&tx]);
                                                },
                                                OnchainClaim::Event(event) => {
                                                        let log_start = if bumped_feerate { "Yielding fee-bumped" } else { "Replaying" };
                                                        log_info!(logger, "{} onchain event to spend inputs {:?}", log_start,
                                                                request.outpoints());
                                                        #[cfg(debug_assertions)] {
                                                                debug_assert!(request.requires_external_funding());
                                                                let num_existing = self.pending_claim_events.iter()
                                                                        .filter(|entry| entry.0 == claim_id).count();
                                                                assert!(num_existing == 0 || num_existing == 1);
                                                        }
                                                        self.pending_claim_events.retain(|event| event.0 != claim_id);
                                                        self.pending_claim_events.push((claim_id, event));
                                                }
                                        }
                                });
                }
        }

        /// Lightning security model (i.e being able to redeem/timeout HTLC or penalize counterparty
        /// onchain) lays on the assumption of claim transactions getting confirmed before timelock
        /// expiration (CSV or CLTV following cases). In case of high-fee spikes, claim tx may get stuck
        /// in the mempool, so you need to bump its feerate quickly using Replace-By-Fee or
        /// Child-Pay-For-Parent.
        ///
        /// Panics if there are signing errors, because signing operations in reaction to on-chain
        /// events are not expected to fail, and if they do, we may lose funds.
        fn generate_claim<F: Deref, L: Deref>(
                &mut self, cur_height: u32, cached_request: &PackageTemplate, force_feerate_bump: bool,
                fee_estimator: &LowerBoundedFeeEstimator<F>, logger: &L,
        ) -> Option<(u32, u64, OnchainClaim)>
        where
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let request_outpoints = cached_request.outpoints();
                if request_outpoints.is_empty() {
                        // Don't prune pending claiming request yet, we may have to resurrect HTLCs. Untractable
                        // packages cannot be aggregated and will never be split, so we cannot end up with an
                        // empty claim.
                        debug_assert!(cached_request.is_malleable());
                        return None;
                }
                // If we've seen transaction inclusion in the chain for all outpoints in our request, we
                // don't need to continue generating more claims. We'll keep tracking the request to fully
                // remove it once it reaches the confirmation threshold, or to generate a new claim if the
                // transaction is reorged out.
                let mut all_inputs_have_confirmed_spend = true;
                for outpoint in request_outpoints.iter() {
                        if let Some((request_claim_id, _)) = self.claimable_outpoints.get(*outpoint) {
                                // We check for outpoint spends within claims individually rather than as a set
                                // since requests can have outpoints split off.
                                if !self.onchain_events_awaiting_threshold_conf.iter()
                                        .any(|event_entry| if let OnchainEvent::Claim { claim_id } = event_entry.event {
                                                *request_claim_id == claim_id
                                        } else {
                                                // The onchain event is not a claim, keep seeking until we find one.
                                                false
                                        })
                                {
                                        // Either we had no `OnchainEvent::Claim`, or we did but none matched the
                                        // outpoint's registered spend.
                                        all_inputs_have_confirmed_spend = false;
                                }
                        } else {
                                // The request's outpoint spend does not exist yet.
                                all_inputs_have_confirmed_spend = false;
                        }
                }
                if all_inputs_have_confirmed_spend {
                        return None;
                }

                // Compute new height timer to decide when we need to regenerate a new bumped version of the claim tx (if we
                // didn't receive confirmation of it before, or not enough reorg-safe depth on top of it).
                let new_timer = cached_request.get_height_timer(cur_height);
                if cached_request.is_malleable() {
                        if cached_request.requires_external_funding() {
                                let target_feerate_sat_per_1000_weight = cached_request.compute_package_feerate(
                                        fee_estimator, ConfirmationTarget::HighPriority, force_feerate_bump
                                );
                                if let Some(htlcs) = cached_request.construct_malleable_package_with_external_funding(self) {
                                        return Some((
                                                new_timer,
                                                target_feerate_sat_per_1000_weight as u64,
                                                OnchainClaim::Event(ClaimEvent::BumpHTLC {
                                                        target_feerate_sat_per_1000_weight,
                                                        htlcs,
                                                        tx_lock_time: PackedLockTime(cached_request.package_locktime(cur_height)),
                                                }),
                                        ));
                                } else {
                                        return None;
                                }
                        }

                        let predicted_weight = cached_request.package_weight(&self.destination_script);
                        if let Some((output_value, new_feerate)) = cached_request.compute_package_output(
                                predicted_weight, self.destination_script.dust_value().to_sat(),
                                force_feerate_bump, fee_estimator, logger,
                        ) {
                                assert!(new_feerate != 0);

                                let transaction = cached_request.finalize_malleable_package(
                                        cur_height, self, output_value, self.destination_script.clone(), logger
                                ).unwrap();
                                log_trace!(logger, "...with timer {} and feerate {}", new_timer, new_feerate);
                                assert!(predicted_weight >= transaction.weight());
                                return Some((new_timer, new_feerate, OnchainClaim::Tx(transaction)));
                        }
                } else {
                        // Untractable packages cannot have their fees bumped through Replace-By-Fee. Some
                        // packages may support fee bumping through Child-Pays-For-Parent, indicated by those
                        // which require external funding.
                        let mut inputs = cached_request.inputs();
                        debug_assert_eq!(inputs.len(), 1);
                        let tx = match cached_request.finalize_untractable_package(self, logger) {
                                Some(tx) => tx,
                                None => return None,
                        };
                        if !cached_request.requires_external_funding() {
                                return Some((new_timer, 0, OnchainClaim::Tx(tx)));
                        }
                        return inputs.find_map(|input| match input {
                                // Commitment inputs with anchors support are the only untractable inputs supported
                                // thus far that require external funding.
                                PackageSolvingData::HolderFundingOutput(..) => {
                                        debug_assert_eq!(tx.txid(), self.holder_commitment.trust().txid(),
                                                "Holder commitment transaction mismatch");
                                        // We'll locate an anchor output we can spend within the commitment transaction.
                                        let funding_pubkey = &self.channel_transaction_parameters.holder_pubkeys.funding_pubkey;
                                        match chan_utils::get_anchor_output(&tx, funding_pubkey) {
                                                // An anchor output was found, so we should yield a funding event externally.
                                                Some((idx, _)) => {
                                                        // TODO: Use a lower confirmation target when both our and the
                                                        // counterparty's latest commitment don't have any HTLCs present.
                                                        let conf_target = ConfirmationTarget::HighPriority;
                                                        let package_target_feerate_sat_per_1000_weight = cached_request
                                                                .compute_package_feerate(fee_estimator, conf_target, force_feerate_bump);
                                                        Some((
                                                                new_timer,
                                                                package_target_feerate_sat_per_1000_weight as u64,
                                                                OnchainClaim::Event(ClaimEvent::BumpCommitment {
                                                                        package_target_feerate_sat_per_1000_weight,
                                                                        commitment_tx: tx.clone(),
                                                                        anchor_output_idx: idx,
                                                                }),
                                                        ))
                                                },
                                                // An anchor output was not found. There's nothing we can do other than
                                                // attempt to broadcast the transaction with its current fee rate and hope
                                                // it confirms. This is essentially the same behavior as a commitment
                                                // transaction without anchor outputs.
                                                None => Some((new_timer, 0, OnchainClaim::Tx(tx.clone()))),
                                        }
                                },
                                _ => {
                                        debug_assert!(false, "Only HolderFundingOutput inputs should be untractable and require external funding");
                                        None
                                },
                        })
                }
                None
        }

        /// Upon channelmonitor.block_connected(..) or upon provision of a preimage on the forward link
        /// for this channel, provide new relevant on-chain transactions and/or new claim requests.
        /// Together with `update_claims_view_from_matched_txn` this used to be named
        /// `block_connected`, but it is now also used for claiming an HTLC output if we receive a
        /// preimage after force-close.
        ///
        /// `conf_height` represents the height at which the request was generated. This
        /// does not need to equal the current blockchain tip height, which should be provided via
        /// `cur_height`, however it must never be higher than `cur_height`.
        pub(crate) fn update_claims_view_from_requests<B: Deref, F: Deref, L: Deref>(
                &mut self, requests: Vec<PackageTemplate>, conf_height: u32, cur_height: u32,
                broadcaster: &B, fee_estimator: &LowerBoundedFeeEstimator<F>, logger: &L
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                log_debug!(logger, "Updating claims view at height {} with {} claim requests", cur_height, requests.len());
                let mut preprocessed_requests = Vec::with_capacity(requests.len());
                let mut aggregated_request = None;

                // Try to aggregate outputs if their timelock expiration isn't imminent (package timelock
                // <= CLTV_SHARED_CLAIM_BUFFER) and they don't require an immediate nLockTime (aggregable).
                for req in requests {
                        // Don't claim a outpoint twice that would be bad for privacy and may uselessly lock a CPFP input for a while
                        if let Some(_) = self.claimable_outpoints.get(req.outpoints()[0]) {
                                log_info!(logger, "Ignoring second claim for outpoint {}:{}, already registered its claiming request", req.outpoints()[0].txid, req.outpoints()[0].vout);
                        } else {
                                let timelocked_equivalent_package = self.locktimed_packages.iter().map(|v| v.1.iter()).flatten()
                                        .find(|locked_package| locked_package.outpoints() == req.outpoints());
                                if let Some(package) = timelocked_equivalent_package {
                                        log_info!(logger, "Ignoring second claim for outpoint {}:{}, we already have one which we're waiting on a timelock at {} for.",
                                                req.outpoints()[0].txid, req.outpoints()[0].vout, package.package_locktime(cur_height));
                                        continue;
                                }

                                let package_locktime = req.package_locktime(cur_height);
                                if package_locktime > cur_height + 1 {
                                        log_info!(logger, "Delaying claim of package until its timelock at {} (current height {}), the following outpoints are spent:", package_locktime, cur_height);
                                        for outpoint in req.outpoints() {
                                                log_info!(logger, "  Outpoint {}", outpoint);
                                        }
                                        self.locktimed_packages.entry(package_locktime).or_insert(Vec::new()).push(req);
                                        continue;
                                }

                                log_trace!(logger, "Test if outpoint can be aggregated with expiration {} against {}", req.timelock(), cur_height + CLTV_SHARED_CLAIM_BUFFER);
                                if req.timelock() <= cur_height + CLTV_SHARED_CLAIM_BUFFER || !req.aggregable() {
                                        // Don't aggregate if outpoint package timelock is soon or marked as non-aggregable
                                        preprocessed_requests.push(req);
                                } else if aggregated_request.is_none() {
                                        aggregated_request = Some(req);
                                } else {
                                        aggregated_request.as_mut().unwrap().merge_package(req);
                                }
                        }
                }
                if let Some(req) = aggregated_request {
                        preprocessed_requests.push(req);
                }

                // Claim everything up to and including `cur_height`
                let remaining_locked_packages = self.locktimed_packages.split_off(&(cur_height + 1));
                for (pop_height, mut entry) in self.locktimed_packages.iter_mut() {
                        log_trace!(logger, "Restoring delayed claim of package(s) at their timelock at {}.", pop_height);
                        preprocessed_requests.append(&mut entry);
                }
                self.locktimed_packages = remaining_locked_packages;

                // Generate claim transactions and track them to bump if necessary at
                // height timer expiration (i.e in how many blocks we're going to take action).
                for mut req in preprocessed_requests {
                        if let Some((new_timer, new_feerate, claim)) = self.generate_claim(
                                cur_height, &req, true /* force_feerate_bump */, &*fee_estimator, &*logger,
                        ) {
                                req.set_timer(new_timer);
                                req.set_feerate(new_feerate);
                                let claim_id = match claim {
                                        OnchainClaim::Tx(tx) => {
                                                log_info!(logger, "Broadcasting onchain {}", log_tx!(tx));
                                                broadcaster.broadcast_transactions(&[&tx]);
                                                ClaimId(tx.txid().into_inner())
                                        },
                                        OnchainClaim::Event(claim_event) => {
                                                log_info!(logger, "Yielding onchain event to spend inputs {:?}", req.outpoints());
                                                let claim_id = match claim_event {
                                                        ClaimEvent::BumpCommitment { ref commitment_tx, .. } =>
                                                                // For commitment claims, we can just use their txid as it should
                                                                // already be unique.
                                                                ClaimId(commitment_tx.txid().into_inner()),
                                                        ClaimEvent::BumpHTLC { ref htlcs, .. } => {
                                                                // For HTLC claims, commit to the entire set of HTLC outputs to
                                                                // claim, which will always be unique per request. Once a claim ID
                                                                // is generated, it is assigned and remains unchanged, even if the
                                                                // underlying set of HTLCs changes.
                                                                let mut engine = Sha256::engine();
                                                                for htlc in htlcs {
                                                                        engine.input(&htlc.commitment_txid.into_inner());
                                                                        engine.input(&htlc.htlc.transaction_output_index.unwrap().to_be_bytes());
                                                                }
                                                                ClaimId(Sha256::from_engine(engine).into_inner())
                                                        },
                                                };
                                                debug_assert!(self.pending_claim_requests.get(&claim_id).is_none());
                                                debug_assert_eq!(self.pending_claim_events.iter().filter(|entry| entry.0 == claim_id).count(), 0);
                                                self.pending_claim_events.push((claim_id, claim_event));
                                                claim_id
                                        },
                                };
                                debug_assert!(self.pending_claim_requests.get(&claim_id).is_none());
                                for k in req.outpoints() {
                                        log_info!(logger, "Registering claiming request for {}:{}", k.txid, k.vout);
                                        self.claimable_outpoints.insert(k.clone(), (claim_id, conf_height));
                                }
                                self.pending_claim_requests.insert(claim_id, req);
                        }
                }
        }

        /// Upon channelmonitor.block_connected(..) or upon provision of a preimage on the forward link
        /// for this channel, provide new relevant on-chain transactions and/or new claim requests.
        /// Together with `update_claims_view_from_requests` this used to be named `block_connected`,
        /// but it is now also used for claiming an HTLC output if we receive a preimage after force-close.
        ///
        /// `conf_height` represents the height at which the transactions in `txn_matched` were
        /// confirmed. This does not need to equal the current blockchain tip height, which should be
        /// provided via `cur_height`, however it must never be higher than `cur_height`.
        pub(crate) fn update_claims_view_from_matched_txn<B: Deref, F: Deref, L: Deref>(
                &mut self, txn_matched: &[&Transaction], conf_height: u32, conf_hash: BlockHash,
                cur_height: u32, broadcaster: &B, fee_estimator: &LowerBoundedFeeEstimator<F>, logger: &L
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                log_debug!(logger, "Updating claims view at height {} with {} matched transactions in block {}", cur_height, txn_matched.len(), conf_height);
                let mut bump_candidates = HashMap::new();
                for tx in txn_matched {
                        // Scan all input to verify is one of the outpoint spent is of interest for us
                        let mut claimed_outputs_material = Vec::new();
                        for inp in &tx.input {
                                if let Some((claim_id, _)) = self.claimable_outpoints.get(&inp.previous_output) {
                                        // If outpoint has claim request pending on it...
                                        if let Some(request) = self.pending_claim_requests.get_mut(claim_id) {
                                                //... we need to verify equality between transaction outpoints and claim request
                                                // outpoints to know if transaction is the original claim or a bumped one issued
                                                // by us.
                                                let mut are_sets_equal = true;
                                                let mut tx_inputs = tx.input.iter().map(|input| &input.previous_output).collect::<Vec<_>>();
                                                tx_inputs.sort_unstable();
                                                for request_input in request.outpoints() {
                                                        if tx_inputs.binary_search(&request_input).is_err() {
                                                                are_sets_equal = false;
                                                                break;
                                                        }
                                                }

                                                macro_rules! clean_claim_request_after_safety_delay {
                                                        () => {
                                                                let entry = OnchainEventEntry {
                                                                        txid: tx.txid(),
                                                                        height: conf_height,
                                                                        block_hash: Some(conf_hash),
                                                                        event: OnchainEvent::Claim { claim_id: *claim_id }
                                                                };
                                                                if !self.onchain_events_awaiting_threshold_conf.contains(&entry) {
                                                                        self.onchain_events_awaiting_threshold_conf.push(entry);
                                                                }
                                                        }
                                                }

                                                // If this is our transaction (or our counterparty spent all the outputs
                                                // before we could anyway with same inputs order than us), wait for
                                                // ANTI_REORG_DELAY and clean the RBF tracking map.
                                                if are_sets_equal {
                                                        clean_claim_request_after_safety_delay!();
                                                } else { // If false, generate new claim request with update outpoint set
                                                        let mut at_least_one_drop = false;
                                                        for input in tx.input.iter() {
                                                                if let Some(package) = request.split_package(&input.previous_output) {
                                                                        claimed_outputs_material.push(package);
                                                                        at_least_one_drop = true;
                                                                }
                                                                // If there are no outpoints left to claim in this request, drop it entirely after ANTI_REORG_DELAY.
                                                                if request.outpoints().is_empty() {
                                                                        clean_claim_request_after_safety_delay!();
                                                                }
                                                        }
                                                        //TODO: recompute soonest_timelock to avoid wasting a bit on fees
                                                        if at_least_one_drop {
                                                                bump_candidates.insert(*claim_id, request.clone());
                                                                // If we have any pending claim events for the request being updated
                                                                // that have yet to be consumed, we'll remove them since they will
                                                                // end up producing an invalid transaction by double spending
                                                                // input(s) that already have a confirmed spend. If such spend is
                                                                // reorged out of the chain, then we'll attempt to re-spend the
                                                                // inputs once we see it.
                                                                #[cfg(debug_assertions)] {
                                                                        let existing = self.pending_claim_events.iter()
                                                                                .filter(|entry| entry.0 == *claim_id).count();
                                                                        assert!(existing == 0 || existing == 1);
                                                                }
                                                                self.pending_claim_events.retain(|entry| entry.0 != *claim_id);
                                                        }
                                                }
                                                break; //No need to iterate further, either tx is our or their
                                        } else {
                                                panic!("Inconsistencies between pending_claim_requests map and claimable_outpoints map");
                                        }
                                }
                        }
                        for package in claimed_outputs_material.drain(..) {
                                let entry = OnchainEventEntry {
                                        txid: tx.txid(),
                                        height: conf_height,
                                        block_hash: Some(conf_hash),
                                        event: OnchainEvent::ContentiousOutpoint { package },
                                };
                                if !self.onchain_events_awaiting_threshold_conf.contains(&entry) {
                                        self.onchain_events_awaiting_threshold_conf.push(entry);
                                }
                        }
                }

                // After security delay, either our claim tx got enough confs or outpoint is definetely out of reach
                let onchain_events_awaiting_threshold_conf =
                        self.onchain_events_awaiting_threshold_conf.drain(..).collect::<Vec<_>>();
                for entry in onchain_events_awaiting_threshold_conf {
                        if entry.has_reached_confirmation_threshold(cur_height) {
                                match entry.event {
                                        OnchainEvent::Claim { claim_id } => {
                                                // We may remove a whole set of claim outpoints here, as these one may have
                                                // been aggregated in a single tx and claimed so atomically
                                                if let Some(request) = self.pending_claim_requests.remove(&claim_id) {
                                                        for outpoint in request.outpoints() {
                                                                log_debug!(logger, "Removing claim tracking for {} due to maturation of claim package {}.",
                                                                        outpoint, log_bytes!(claim_id.0));
                                                                self.claimable_outpoints.remove(outpoint);
                                                        }
                                                        #[cfg(debug_assertions)] {
                                                                let num_existing = self.pending_claim_events.iter()
                                                                        .filter(|entry| entry.0 == claim_id).count();
                                                                assert!(num_existing == 0 || num_existing == 1);
                                                        }
                                                        self.pending_claim_events.retain(|(id, _)| *id != claim_id);
                                                }
                                        },
                                        OnchainEvent::ContentiousOutpoint { package } => {
                                                log_debug!(logger, "Removing claim tracking due to maturation of claim tx for outpoints:");
                                                log_debug!(logger, " {:?}", package.outpoints());
                                                self.claimable_outpoints.remove(package.outpoints()[0]);
                                        }
                                }
                        } else {
                                self.onchain_events_awaiting_threshold_conf.push(entry);
                        }
                }

                // Check if any pending claim request must be rescheduled
                for (claim_id, request) in self.pending_claim_requests.iter() {
                        if cur_height >= request.timer() {
                                bump_candidates.insert(*claim_id, request.clone());
                        }
                }

                // Build, bump and rebroadcast tx accordingly
                log_trace!(logger, "Bumping {} candidates", bump_candidates.len());
                for (claim_id, request) in bump_candidates.iter() {
                        if let Some((new_timer, new_feerate, bump_claim)) = self.generate_claim(
                                cur_height, &request, true /* force_feerate_bump */, &*fee_estimator, &*logger,
                        ) {
                                match bump_claim {
                                        OnchainClaim::Tx(bump_tx) => {
                                                log_info!(logger, "Broadcasting RBF-bumped onchain {}", log_tx!(bump_tx));
                                                broadcaster.broadcast_transactions(&[&bump_tx]);
                                        },
                                        OnchainClaim::Event(claim_event) => {
                                                log_info!(logger, "Yielding RBF-bumped onchain event to spend inputs {:?}", request.outpoints());
                                                #[cfg(debug_assertions)] {
                                                        let num_existing = self.pending_claim_events.iter().
                                                                filter(|entry| entry.0 == *claim_id).count();
                                                        assert!(num_existing == 0 || num_existing == 1);
                                                }
                                                self.pending_claim_events.retain(|event| event.0 != *claim_id);
                                                self.pending_claim_events.push((*claim_id, claim_event));
                                        },
                                }
                                if let Some(request) = self.pending_claim_requests.get_mut(claim_id) {
                                        request.set_timer(new_timer);
                                        request.set_feerate(new_feerate);
                                }
                        }
                }
        }

        pub(crate) fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
                &mut self,
                txid: &Txid,
                broadcaster: B,
                fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: L,
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let mut height = None;
                for entry in self.onchain_events_awaiting_threshold_conf.iter() {
                        if entry.txid == *txid {
                                height = Some(entry.height);
                                break;
                        }
                }

                if let Some(height) = height {
                        self.block_disconnected(height, broadcaster, fee_estimator, logger);
                }
        }

        pub(crate) fn block_disconnected<B: Deref, F: Deref, L: Deref>(&mut self, height: u32, broadcaster: B, fee_estimator: &LowerBoundedFeeEstimator<F>, logger: L)
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator,
                                        L::Target: Logger,
        {
                let mut bump_candidates = HashMap::new();
                let onchain_events_awaiting_threshold_conf =
                        self.onchain_events_awaiting_threshold_conf.drain(..).collect::<Vec<_>>();
                for entry in onchain_events_awaiting_threshold_conf {
                        if entry.height >= height {
                                //- our claim tx on a commitment tx output
                                //- resurect outpoint back in its claimable set and regenerate tx
                                match entry.event {
                                        OnchainEvent::ContentiousOutpoint { package } => {
                                                if let Some(pending_claim) = self.claimable_outpoints.get(package.outpoints()[0]) {
                                                        if let Some(request) = self.pending_claim_requests.get_mut(&pending_claim.0) {
                                                                request.merge_package(package);
                                                                // Using a HashMap guarantee us than if we have multiple outpoints getting
                                                                // resurrected only one bump claim tx is going to be broadcast
                                                                bump_candidates.insert(pending_claim.clone(), request.clone());
                                                        }
                                                }
                                        },
                                        _ => {},
                                }
                        } else {
                                self.onchain_events_awaiting_threshold_conf.push(entry);
                        }
                }
                for ((_claim_id, _), ref mut request) in bump_candidates.iter_mut() {
                        // `height` is the height being disconnected, so our `current_height` is 1 lower.
                        let current_height = height - 1;
                        if let Some((new_timer, new_feerate, bump_claim)) = self.generate_claim(
                                current_height, &request, true /* force_feerate_bump */, fee_estimator, &&*logger
                        ) {
                                request.set_timer(new_timer);
                                request.set_feerate(new_feerate);
                                match bump_claim {
                                        OnchainClaim::Tx(bump_tx) => {
                                                log_info!(logger, "Broadcasting onchain {}", log_tx!(bump_tx));
                                                broadcaster.broadcast_transactions(&[&bump_tx]);
                                        },
                                        OnchainClaim::Event(claim_event) => {
                                                log_info!(logger, "Yielding onchain event after reorg to spend inputs {:?}", request.outpoints());
                                                #[cfg(debug_assertions)] {
                                                        let num_existing = self.pending_claim_events.iter()
                                                                .filter(|entry| entry.0 == *_claim_id).count();
                                                        assert!(num_existing == 0 || num_existing == 1);
                                                }
                                                self.pending_claim_events.retain(|event| event.0 != *_claim_id);
                                                self.pending_claim_events.push((*_claim_id, claim_event));
                                        },
                                }
                        }
                }
                for (ancestor_claim_txid, request) in bump_candidates.drain() {
                        self.pending_claim_requests.insert(ancestor_claim_txid.0, request);
                }
                //TODO: if we implement cross-block aggregated claim transaction we need to refresh set of outpoints and regenerate tx but
                // right now if one of the outpoint get disconnected, just erase whole pending claim request.
                let mut remove_request = Vec::new();
                self.claimable_outpoints.retain(|_, ref v|
                        if v.1 >= height {
                        remove_request.push(v.0.clone());
                        false
                        } else { true });
                for req in remove_request {
                        self.pending_claim_requests.remove(&req);
                }
        }

        pub(crate) fn is_output_spend_pending(&self, outpoint: &BitcoinOutPoint) -> bool {
                self.claimable_outpoints.get(outpoint).is_some()
        }

        pub(crate) fn get_relevant_txids(&self) -> Vec<(Txid, Option<BlockHash>)> {
                let mut txids: Vec<(Txid, Option<BlockHash>)> = self.onchain_events_awaiting_threshold_conf
                        .iter()
                        .map(|entry| (entry.txid, entry.block_hash))
                        .collect();
                txids.sort_unstable_by_key(|(txid, _)| *txid);
                txids.dedup();
                txids
        }

        pub(crate) fn provide_latest_holder_tx(&mut self, tx: HolderCommitmentTransaction) {
                self.prev_holder_commitment = Some(replace(&mut self.holder_commitment, tx));
                self.holder_htlc_sigs = None;
        }

        // Normally holder HTLCs are signed at the same time as the holder commitment tx.  However,
        // in some configurations, the holder commitment tx has been signed and broadcast by a
        // ChannelMonitor replica, so we handle that case here.
        fn sign_latest_holder_htlcs(&mut self) {
                if self.holder_htlc_sigs.is_none() {
                        let (_sig, sigs) = self.signer.sign_holder_commitment_and_htlcs(&self.holder_commitment, &self.secp_ctx).expect("sign holder commitment");
                        self.holder_htlc_sigs = Some(Self::extract_holder_sigs(&self.holder_commitment, sigs));
                }
        }

        // Normally only the latest commitment tx and HTLCs need to be signed.  However, in some
        // configurations we may have updated our holder commitment but a replica of the ChannelMonitor
        // broadcast the previous one before we sync with it.  We handle that case here.
        fn sign_prev_holder_htlcs(&mut self) {
                if self.prev_holder_htlc_sigs.is_none() {
                        if let Some(ref holder_commitment) = self.prev_holder_commitment {
                                let (_sig, sigs) = self.signer.sign_holder_commitment_and_htlcs(holder_commitment, &self.secp_ctx).expect("sign previous holder commitment");
                                self.prev_holder_htlc_sigs = Some(Self::extract_holder_sigs(holder_commitment, sigs));
                        }
                }
        }

        fn extract_holder_sigs(holder_commitment: &HolderCommitmentTransaction, sigs: Vec<Signature>) -> Vec<Option<(usize, Signature)>> {
                let mut ret = Vec::new();
                for (htlc_idx, (holder_sig, htlc)) in sigs.iter().zip(holder_commitment.htlcs().iter()).enumerate() {
                        let tx_idx = htlc.transaction_output_index.unwrap();
                        if ret.len() <= tx_idx as usize { ret.resize(tx_idx as usize + 1, None); }
                        ret[tx_idx as usize] = Some((htlc_idx, holder_sig.clone()));
                }
                ret
        }

        //TODO: getting lastest holder transactions should be infallible and result in us "force-closing the channel", but we may
        // have empty holder commitment transaction if a ChannelMonitor is asked to force-close just after Channel::get_outbound_funding_created,
        // before providing a initial commitment transaction. For outbound channel, init ChannelMonitor at Channel::funding_signed, there is nothing
        // to monitor before.
        pub(crate) fn get_fully_signed_holder_tx(&mut self, funding_redeemscript: &Script) -> Transaction {
                let (sig, htlc_sigs) = self.signer.sign_holder_commitment_and_htlcs(&self.holder_commitment, &self.secp_ctx).expect("signing holder commitment");
                self.holder_htlc_sigs = Some(Self::extract_holder_sigs(&self.holder_commitment, htlc_sigs));
                self.holder_commitment.add_holder_sig(funding_redeemscript, sig)
        }

        #[cfg(any(test, feature="unsafe_revoked_tx_signing"))]
        pub(crate) fn get_fully_signed_copy_holder_tx(&mut self, funding_redeemscript: &Script) -> Transaction {
                let (sig, htlc_sigs) = self.signer.unsafe_sign_holder_commitment_and_htlcs(&self.holder_commitment, &self.secp_ctx).expect("sign holder commitment");
                self.holder_htlc_sigs = Some(Self::extract_holder_sigs(&self.holder_commitment, htlc_sigs));
                self.holder_commitment.add_holder_sig(funding_redeemscript, sig)
        }

        pub(crate) fn get_fully_signed_htlc_tx(&mut self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>) -> Option<Transaction> {
                let mut htlc_tx = None;
                let commitment_txid = self.holder_commitment.trust().txid();
                // Check if the HTLC spends from the current holder commitment
                if commitment_txid == outp.txid {
                        self.sign_latest_holder_htlcs();
                        if let &Some(ref htlc_sigs) = &self.holder_htlc_sigs {
                                let &(ref htlc_idx, ref htlc_sig) = htlc_sigs[outp.vout as usize].as_ref().unwrap();
                                let trusted_tx = self.holder_commitment.trust();
                                let counterparty_htlc_sig = self.holder_commitment.counterparty_htlc_sigs[*htlc_idx];
                                htlc_tx = Some(trusted_tx
                                        .get_signed_htlc_tx(&self.channel_transaction_parameters.as_holder_broadcastable(), *htlc_idx, &counterparty_htlc_sig, htlc_sig, preimage));
                        }
                }
                // If the HTLC doesn't spend the current holder commitment, check if it spends the previous one
                if htlc_tx.is_none() && self.prev_holder_commitment.is_some() {
                        let commitment_txid = self.prev_holder_commitment.as_ref().unwrap().trust().txid();
                        if commitment_txid == outp.txid {
                                self.sign_prev_holder_htlcs();
                                if let &Some(ref htlc_sigs) = &self.prev_holder_htlc_sigs {
                                        let &(ref htlc_idx, ref htlc_sig) = htlc_sigs[outp.vout as usize].as_ref().unwrap();
                                        let holder_commitment = self.prev_holder_commitment.as_ref().unwrap();
                                        let trusted_tx = holder_commitment.trust();
                                        let counterparty_htlc_sig = holder_commitment.counterparty_htlc_sigs[*htlc_idx];
                                        htlc_tx = Some(trusted_tx
                                                .get_signed_htlc_tx(&self.channel_transaction_parameters.as_holder_broadcastable(), *htlc_idx, &counterparty_htlc_sig, htlc_sig, preimage));
                                }
                        }
                }
                htlc_tx
        }

        pub(crate) fn generate_external_htlc_claim(
                &self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>
        ) -> Option<ExternalHTLCClaim> {
                let find_htlc = |holder_commitment: &HolderCommitmentTransaction| -> Option<ExternalHTLCClaim> {
                        let trusted_tx = holder_commitment.trust();
                        if outp.txid != trusted_tx.txid() {
                                return None;
                        }
                        trusted_tx.htlcs().iter().enumerate()
                                .find(|(_, htlc)| if let Some(output_index) = htlc.transaction_output_index {
                                        output_index == outp.vout
                                } else {
                                        false
                                })
                                .map(|(htlc_idx, htlc)| {
                                        let counterparty_htlc_sig = holder_commitment.counterparty_htlc_sigs[htlc_idx];
                                        ExternalHTLCClaim {
                                                commitment_txid: trusted_tx.txid(),
                                                per_commitment_number: trusted_tx.commitment_number(),
                                                htlc: htlc.clone(),
                                                preimage: *preimage,
                                                counterparty_sig: counterparty_htlc_sig,
                                        }
                                })
                };
                // Check if the HTLC spends from the current holder commitment or the previous one otherwise.
                find_htlc(&self.holder_commitment)
                        .or_else(|| self.prev_holder_commitment.as_ref().map(|c| find_htlc(c)).flatten())
        }

        pub(crate) fn channel_type_features(&self) -> &ChannelTypeFeatures {
                &self.channel_transaction_parameters.channel_type_features
        }

        #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
        pub(crate) fn unsafe_get_fully_signed_htlc_tx(&mut self, outp: &::bitcoin::OutPoint, preimage: &Option<PaymentPreimage>) -> Option<Transaction> {
                let latest_had_sigs = self.holder_htlc_sigs.is_some();
                let prev_had_sigs = self.prev_holder_htlc_sigs.is_some();
                let ret = self.get_fully_signed_htlc_tx(outp, preimage);
                if !latest_had_sigs {
                        self.holder_htlc_sigs = None;
                }
                if !prev_had_sigs {
                        self.prev_holder_htlc_sigs = None;
                }
                ret
        }
}