[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::blockdata::transaction::Transaction;
use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
use bitcoin::blockdata::script::Script;

use bitcoin::hash_types::Txid;

use bitcoin::secp256k1::{Secp256k1, Signature};
use bitcoin::secp256k1;

use ln::msgs::DecodeError;
use ln::PaymentPreimage;
use ln::chan_utils::{ChannelTransactionParameters, HolderCommitmentTransaction};
use chain::chaininterface::{FeeEstimator, BroadcasterInterface};
use chain::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER};
use chain::keysinterface::{Sign, KeysInterface};
use chain::package::PackageTemplate;
use chain::package;
use util::logger::Logger;
use util::ser::{Readable, ReadableArgs, Writer, Writeable, VecWriter};
use util::byte_utils;

use std::collections::HashMap;
use core::cmp;
use core::ops::Deref;
use core::mem::replace;

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)]
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(PartialEq)]
enum OnchainEvent {
        /// Outpoint under claim process by our own tx, once this one get enough confirmations, we remove it from
        /// bump-txn candidate buffer.
        Claim {
                claim_request: Txid,
        },
        /// Claim tx aggregate multiple claimable outpoints. One of the outpoint may be claimed by a counterparty party tx.
        /// In this case, we need to drop the outpoint and regenerate a new claim tx. By safety, we keep tracking
        /// the outpoint to be sure to resurect it back to the claim tx if reorgs happen.
        ContentiousOutpoint {
                package: PackageTemplate,
        }
}

impl Readable for Option<Vec<Option<(usize, Signature)>>> {
        fn read<R: ::std::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<(), ::std::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(())
        }
}


/// OnchainTxHandler receives claiming requests, aggregates them if it's sound, broadcast and
/// do RBF bumping if possible.
pub struct OnchainTxHandler<ChannelSigner: Sign> {
        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<Txid, PackageTemplate>,
        #[cfg(not(test))]
        pending_claim_requests: HashMap<Txid, PackageTemplate>,

        // Used to link outpoints claimed in a connected block to a pending claim request.
        // Key is outpoint than monitor parsing has detected we have keys/scripts to claim
        // Value is (pending claim request identifier, confirmation_block), identifier
        // is txid of the initial claiming transaction and is immutable until outpoint is
        // post-anti-reorg-delay solved, confirmaiton_block is used to erase entry if
        // block with output gets disconnected.
        #[cfg(test)] // Used in functional_test to verify sanitization
        pub claimable_outpoints: HashMap<BitcoinOutPoint, (Txid, u32)>,
        #[cfg(not(test))]
        claimable_outpoints: HashMap<BitcoinOutPoint, (Txid, u32)>,

        onchain_events_awaiting_threshold_conf: Vec<OnchainEventEntry>,

        latest_height: u32,

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

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

impl<ChannelSigner: Sign> OnchainTxHandler<ChannelSigner> {
        pub(crate) fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::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(&byte_utils::be64_to_array(self.pending_claim_requests.len() as u64))?;
                for (ref ancestor_claim_txid, request) in self.pending_claim_requests.iter() {
                        ancestor_claim_txid.write(writer)?;
                        request.write(writer)?;
                }

                writer.write_all(&byte_utils::be64_to_array(self.claimable_outpoints.len() as u64))?;
                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(&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::Claim { ref claim_request } => {
                                        writer.write_all(&[0; 1])?;
                                        claim_request.write(writer)?;
                                },
                                OnchainEvent::ContentiousOutpoint { ref package } => {
                                        writer.write_all(&[1; 1])?;
                                        package.write(writer)?;
                                }
                        }
                }
                self.latest_height.write(writer)?;

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

impl<'a, K: KeysInterface> ReadableArgs<&'a K> for OnchainTxHandler<K::Signer> {
        fn read<R: ::std::io::Read>(reader: &mut R, keys_manager: &'a K) -> Result<Self, DecodeError> {
                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)?;

                let keys_len: u32 = Readable::read(reader)?;
                let mut keys_data = Vec::with_capacity(cmp::min(keys_len as usize, MAX_ALLOC_SIZE));
                while keys_data.len() != keys_len as usize {
                        // Read 1KB at a time to avoid accidentally allocating 4GB on corrupted channel keys
                        let mut data = [0; 1024];
                        let read_slice = &mut data[0..cmp::min(1024, keys_len as usize - keys_data.len())];
                        reader.read_exact(read_slice)?;
                        keys_data.extend_from_slice(read_slice);
                }
                let signer = keys_manager.read_chan_signer(&keys_data)?;

                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 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 {
                        let txid = Readable::read(reader)?;
                        let height = Readable::read(reader)?;
                        let event = match <u8 as Readable>::read(reader)? {
                                0 => {
                                        let claim_request = Readable::read(reader)?;
                                        OnchainEvent::Claim {
                                                claim_request
                                        }
                                },
                                1 => {
                                        let package = Readable::read(reader)?;
                                        OnchainEvent::ContentiousOutpoint {
                                                package
                                        }
                                }
                                _ => return Err(DecodeError::InvalidValue),
                        };
                        onchain_events_awaiting_threshold_conf.push(OnchainEventEntry { txid, height, event });
                }
                let latest_height = Readable::read(reader)?;

                read_tlv_fields!(reader, {}, {});

                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_manager.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,
                        pending_claim_requests,
                        onchain_events_awaiting_threshold_conf,
                        latest_height,
                        secp_ctx,
                })
        }
}

impl<ChannelSigner: Sign> 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(),
                        onchain_events_awaiting_threshold_conf: Vec::new(),
                        latest_height: 0,

                        secp_ctx,
                }
        }

        /// In LN, output claimed are time-sensitive, which means we have to spend them before reaching some timelock expiration. At in-channel
        /// output detection, we generate a first version of a claim tx and associate to it a height timer. A height timer is an absolute block
        /// height than once reached we should generate a new bumped "version" of the claim tx to be sure than we safely claim outputs before
        /// than our counterparty can do it too. If timelock expires soon, height timer is going to be scale down in consequence to increase
        /// frequency of the bump and so increase our bets of success.
        fn get_height_timer(current_height: u32, timelock_expiration: u32) -> u32 {
                if timelock_expiration <= current_height + 3 {
                        return current_height + 1
                } else if timelock_expiration - current_height <= 15 {
                        return current_height + 3
                }
                current_height + 15
        }

        /// Lightning security model (i.e being able to redeem/timeout HTLC or penalize coutnerparty 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 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_tx<F: Deref, L: Deref>(&mut self, height: u32, cached_request: &PackageTemplate, fee_estimator: &F, logger: &L) -> Option<(Option<u32>, u64, Transaction)>
                where F::Target: FeeEstimator,
                                        L::Target: Logger,
        {
                if cached_request.outpoints().len() == 0 { return None } // But don't prune pending claiming request yet, we may have to resurrect HTLCs

                // 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 = Some(Self::get_height_timer(height, cached_request.timelock()));
                let amt = cached_request.package_amount();
                if cached_request.is_malleable() {
                        let predicted_weight = cached_request.package_weight(&self.destination_script);
                        if let Some((output_value, new_feerate)) = package::compute_output_value(predicted_weight, amt, cached_request.feerate(), fee_estimator, logger) {
                                assert!(new_feerate != 0);

                                let transaction = cached_request.finalize_package(self, output_value, self.destination_script.clone(), logger).unwrap();
                                log_trace!(logger, "...with timer {} and feerate {}", new_timer.unwrap(), new_feerate);
                                assert!(predicted_weight >= transaction.get_weight());
                                return Some((new_timer, new_feerate, transaction))
                        }
                } else {
                        // Note: Currently, amounts of holder outputs spending witnesses aren't used
                        // as we can't malleate spending package to increase their feerate. This
                        // should change with the remaining anchor output patchset.
                        debug_assert!(amt == 0);
                        if let Some(transaction) = cached_request.finalize_package(self, amt, self.destination_script.clone(), logger) {
                                return Some((None, 0, transaction));
                        }
                }
                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.
        /// Formerly this was named `block_connected`, but it is now also used for claiming an HTLC output
        /// if we receive a preimage after force-close.
        pub(crate) fn update_claims_view<B: Deref, F: Deref, L: Deref>(&mut self, txn_matched: &[&Transaction], requests: Vec<PackageTemplate>, latest_height: Option<u32>, broadcaster: &B, fee_estimator: &F, logger: &L)
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator,
                                        L::Target: Logger,
        {
                let height = match latest_height {
                        Some(h) => h,
                        None => self.latest_height,
                };
                log_trace!(logger, "Updating claims view at height {} with {} matched transactions and {} claim requests", height, txn_matched.len(), 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_trace!(logger, "Bouncing off outpoint {}:{}, already registered its claiming request", req.outpoints()[0].txid, req.outpoints()[0].vout); } else {
                                log_trace!(logger, "Test if outpoint can be aggregated with expiration {} against {}", req.timelock(), height + CLTV_SHARED_CLAIM_BUFFER);
                                if req.timelock() <= 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);
                }

                // 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, tx)) = self.generate_claim_tx(height, &req, &*fee_estimator, &*logger) {
                                req.set_timer(new_timer);
                                req.set_feerate(new_feerate);
                                let txid = tx.txid();
                                for k in req.outpoints() {
                                        log_trace!(logger, "Registering claiming request for {}:{}", k.txid, k.vout);
                                        self.claimable_outpoints.insert(k.clone(), (txid, height));
                                }
                                self.pending_claim_requests.insert(txid, req);
                                log_trace!(logger, "Broadcasting onchain {}", log_tx!(tx));
                                broadcaster.broadcast_transaction(&tx);
                        }
                }

                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(first_claim_txid_height) = 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(&first_claim_txid_height.0) {
                                                //... 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 set_equality = true;
                                                if request.outpoints().len() != tx.input.len() {
                                                        set_equality = false;
                                                } else {
                                                        for (claim_inp, tx_inp) in request.outpoints().iter().zip(tx.input.iter()) {
                                                                if **claim_inp != tx_inp.previous_output {
                                                                        set_equality = false;
                                                                }
                                                        }
                                                }

                                                macro_rules! clean_claim_request_after_safety_delay {
                                                        () => {
                                                                let entry = OnchainEventEntry {
                                                                        txid: tx.txid(),
                                                                        height,
                                                                        event: OnchainEvent::Claim { claim_request: first_claim_txid_height.0.clone() }
                                                                };
                                                                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 set_equality {
                                                        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(first_claim_txid_height.0.clone(), request.clone());
                                                        }
                                                }
                                                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,
                                        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(height) {
                                match entry.event {
                                        OnchainEvent::Claim { claim_request } => {
                                                // 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_request) {
                                                        for outpoint in request.outpoints() {
                                                                self.claimable_outpoints.remove(&outpoint);
                                                        }
                                                }
                                        },
                                        OnchainEvent::ContentiousOutpoint { package } => {
                                                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 (first_claim_txid, ref request) in self.pending_claim_requests.iter() {
                        if let Some(h) = request.timer() {
                                if height >= h {
                                        bump_candidates.insert(*first_claim_txid, (*request).clone());
                                }
                        }
                }

                // Build, bump and rebroadcast tx accordingly
                log_trace!(logger, "Bumping {} candidates", bump_candidates.len());
                for (first_claim_txid, request) in bump_candidates.iter() {
                        if let Some((new_timer, new_feerate, bump_tx)) = self.generate_claim_tx(height, &request, &*fee_estimator, &*logger) {
                                log_trace!(logger, "Broadcasting onchain {}", log_tx!(bump_tx));
                                broadcaster.broadcast_transaction(&bump_tx);
                                if let Some(request) = self.pending_claim_requests.get_mut(first_claim_txid) {
                                        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: 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: 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(ancestor_claimable_txid) = self.claimable_outpoints.get(&package.outpoints()[0]) {
                                                        if let Some(request) = self.pending_claim_requests.get_mut(&ancestor_claimable_txid.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(ancestor_claimable_txid.clone(), request.clone());
                                                        }
                                                }
                                        },
                                        _ => {},
                                }
                        } else {
                                self.onchain_events_awaiting_threshold_conf.push(entry);
                        }
                }
                for (_, request) in bump_candidates.iter_mut() {
                        if let Some((new_timer, new_feerate, bump_tx)) = self.generate_claim_tx(height, &request, &&*fee_estimator, &&*logger) {
                                request.set_timer(new_timer);
                                request.set_feerate(new_feerate);
                                log_info!(logger, "Broadcasting onchain {}", log_tx!(bump_tx));
                                broadcaster.broadcast_transaction(&bump_tx);
                        }
                }
                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 get_relevant_txids(&self) -> Vec<Txid> {
                let mut txids: Vec<Txid> = self.onchain_events_awaiting_threshold_conf
                        .iter()
                        .map(|entry| entry.txid)
                        .collect();
                txids.sort_unstable();
                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
        }

        #[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
        }
}