Factor out low-level build_closing_transaction
[rust-lightning] / lightning / src / ln / channel.rs
index 0d5ffb038c9585853270e507b4664b0d3e60efaf..2c835080a061d54c6951f65fadca3525b70c319d 100644 (file)
@@ -8,16 +8,16 @@
 // licenses.
 
 use bitcoin::blockdata::script::{Script,Builder};
-use bitcoin::blockdata::transaction::{TxIn, TxOut, Transaction, SigHashType};
-use bitcoin::blockdata::opcodes;
+use bitcoin::blockdata::transaction::{Transaction, SigHashType};
 use bitcoin::util::bip143;
 use bitcoin::consensus::encode;
 
 use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hashes::sha256d::Hash as Sha256d;
-use bitcoin::hash_types::{Txid, BlockHash, WPubkeyHash};
+use bitcoin::hash_types::{Txid, BlockHash};
 
+use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
 use bitcoin::secp256k1::key::{PublicKey,SecretKey};
 use bitcoin::secp256k1::{Secp256k1,Signature};
 use bitcoin::secp256k1;
@@ -26,28 +26,29 @@ use ln::{PaymentPreimage, PaymentHash};
 use ln::features::{ChannelFeatures, InitFeatures};
 use ln::msgs;
 use ln::msgs::{DecodeError, OptionalField, DataLossProtect};
+use ln::script::ShutdownScript;
 use ln::channelmanager::{PendingHTLCStatus, HTLCSource, HTLCFailReason, HTLCFailureMsg, PendingHTLCInfo, RAACommitmentOrder, BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA, MAX_LOCAL_BREAKDOWN_TIMEOUT};
-use ln::chan_utils::{CounterpartyCommitmentSecrets, TxCreationKeys, HTLCOutputInCommitment, HTLC_SUCCESS_TX_WEIGHT, HTLC_TIMEOUT_TX_WEIGHT, make_funding_redeemscript, ChannelPublicKeys, CommitmentTransaction, HolderCommitmentTransaction, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, MAX_HTLCS, get_commitment_transaction_number_obscure_factor};
+use ln::chan_utils::{CounterpartyCommitmentSecrets, TxCreationKeys, HTLCOutputInCommitment, HTLC_SUCCESS_TX_WEIGHT, HTLC_TIMEOUT_TX_WEIGHT, make_funding_redeemscript, ChannelPublicKeys, CommitmentTransaction, HolderCommitmentTransaction, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, MAX_HTLCS, get_commitment_transaction_number_obscure_factor, build_closing_transaction};
 use ln::chan_utils;
 use chain::BestBlock;
 use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
 use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateStep, HTLC_FAIL_BACK_BUFFER};
 use chain::transaction::{OutPoint, TransactionData};
 use chain::keysinterface::{Sign, KeysInterface};
-use util::transaction_utils;
 use util::ser::{Readable, ReadableArgs, Writeable, Writer, VecWriter};
 use util::logger::Logger;
 use util::errors::APIError;
 use util::config::{UserConfig,ChannelConfig};
 use util::scid_utils::scid_from_parts;
 
+use io;
 use prelude::*;
 use core::{cmp,mem,fmt};
+use core::convert::TryFrom;
 use core::ops::Deref;
 #[cfg(any(test, feature = "fuzztarget", debug_assertions))]
 use sync::Mutex;
 use bitcoin::hashes::hex::ToHex;
-use bitcoin::blockdata::opcodes::all::OP_PUSHBYTES_0;
 
 #[cfg(test)]
 pub struct ChannelValueStat {
@@ -61,6 +62,21 @@ pub struct ChannelValueStat {
        pub counterparty_dust_limit_msat: u64,
 }
 
+#[derive(Clone, Copy, PartialEq)]
+enum FeeUpdateState {
+       // Inbound states mirroring InboundHTLCState
+       RemoteAnnounced,
+       AwaitingRemoteRevokeToAnnounce,
+       // Note that we do not have a AwaitingAnnouncedRemoteRevoke variant here as it is universally
+       // handled the same as `Committed`, with the only exception in `InboundHTLCState` being the
+       // distinction of when we allow ourselves to forward the HTLC. Because we aren't "forwarding"
+       // the fee update anywhere, we can simply consider the fee update `Committed` immediately
+       // instead of setting it to AwaitingAnnouncedRemoteRevoke.
+
+       // Outbound state can only be `LocalAnnounced` or `Committed`
+       Outbound,
+}
+
 enum InboundHTLCRemovalReason {
        FailRelay(msgs::OnionErrorPacket),
        FailMalformed(([u8; 32], u16)),
@@ -238,8 +254,6 @@ enum ChannelState {
        RemoteShutdownSent = 1 << 10,
        /// Flag which is set on ChannelFunded or FundingSent after sending a shutdown message. At this
        /// point, we may not add any new HTLCs to the channel.
-       /// TODO: Investigate some kind of timeout mechanism by which point the remote end must provide
-       /// us their shutdown.
        LocalShutdownSent = 1 << 11,
        /// We've successfully negotiated a closing_signed dance. At this point ChannelManager is about
        /// to drop us, but we store this anyway.
@@ -273,6 +287,14 @@ enum HTLCInitiator {
        RemoteOffered,
 }
 
+/// An enum gathering stats on pending HTLCs, either inbound or outbound side.
+struct HTLCStats {
+       pending_htlcs: u32,
+       pending_htlcs_value_msat: u64,
+       on_counterparty_tx_dust_exposure_msat: u64,
+       on_holder_tx_dust_exposure_msat: u64,
+}
+
 /// Used when calculating whether we or the remote can afford an additional HTLC.
 struct HTLCCandidate {
        amount_msat: u64,
@@ -301,6 +323,52 @@ pub struct CounterpartyForwardingInfo {
        pub cltv_expiry_delta: u16,
 }
 
+/// A return value enum for get_update_fulfill_htlc. See UpdateFulfillCommitFetch variants for
+/// description
+enum UpdateFulfillFetch {
+       NewClaim {
+               monitor_update: ChannelMonitorUpdate,
+               htlc_value_msat: u64,
+               msg: Option<msgs::UpdateFulfillHTLC>,
+       },
+       DuplicateClaim {},
+}
+
+/// The return type of get_update_fulfill_htlc_and_commit.
+pub enum UpdateFulfillCommitFetch {
+       /// Indicates the HTLC fulfill is new, and either generated an update_fulfill message, placed
+       /// it in the holding cell, or re-generated the update_fulfill message after the same claim was
+       /// previously placed in the holding cell (and has since been removed).
+       NewClaim {
+               /// The ChannelMonitorUpdate which places the new payment preimage in the channel monitor
+               monitor_update: ChannelMonitorUpdate,
+               /// The value of the HTLC which was claimed, in msat.
+               htlc_value_msat: u64,
+               /// The update_fulfill message and commitment_signed message (if the claim was not placed
+               /// in the holding cell).
+               msgs: Option<(msgs::UpdateFulfillHTLC, msgs::CommitmentSigned)>,
+       },
+       /// Indicates the HTLC fulfill is duplicative and already existed either in the holding cell
+       /// or has been forgotten (presumably previously claimed).
+       DuplicateClaim {},
+}
+
+/// If the majority of the channels funds are to the fundee and the initiator holds only just
+/// enough funds to cover their reserve value, channels are at risk of getting "stuck". Because the
+/// initiator controls the feerate, if they then go to increase the channel fee, they may have no
+/// balance but the fundee is unable to send a payment as the increase in fee more than drains
+/// their reserve value. Thus, neither side can send a new HTLC and the channel becomes useless.
+/// Thus, before sending an HTLC when we are the initiator, we check that the feerate can increase
+/// by this multiple without hitting this case, before sending.
+/// This multiple is effectively the maximum feerate "jump" we expect until more HTLCs flow over
+/// the channel. Sadly, there isn't really a good number for this - if we expect to have no new
+/// HTLCs for days we may need this to suffice for feerate increases across days, but that may
+/// leave the channel less usable as we hold a bigger reserve.
+#[cfg(fuzzing)]
+pub const FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE: u64 = 2;
+#[cfg(not(fuzzing))]
+const FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE: u64 = 2;
+
 // TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
 // has been completed, and then turn into a Channel to get compiler-time enforcement of things like
 // calling channel_id() before we're set up or things like get_outbound_funding_signed on an
@@ -309,6 +377,9 @@ pub struct CounterpartyForwardingInfo {
 // Holder designates channel data owned for the benefice of the user client.
 // Counterparty designates channel data owned by the another channel participant entity.
 pub(super) struct Channel<Signer: Sign> {
+       #[cfg(any(test, feature = "_test_utils"))]
+       pub(crate) config: ChannelConfig,
+       #[cfg(not(any(test, feature = "_test_utils")))]
        config: ChannelConfig,
 
        user_id: u64,
@@ -321,7 +392,7 @@ pub(super) struct Channel<Signer: Sign> {
        latest_monitor_update_id: u64,
 
        holder_signer: Signer,
-       shutdown_pubkey: PublicKey,
+       shutdown_scriptpubkey: Option<ShutdownScript>,
        destination_script: Script,
 
        // Our commitment numbers start at 2^48-1 and count down, whereas the ones used in transaction
@@ -361,7 +432,7 @@ pub(super) struct Channel<Signer: Sign> {
        // revoke_and_ack is received and new commitment_signed is generated to be
        // sent to the funder. Otherwise, the pending value is removed when receiving
        // commitment_signed.
-       pending_update_fee: Option<u32>,
+       pending_update_fee: Option<(u32, FeeUpdateState)>,
        // update_fee() during ChannelState::AwaitingRemoteRevoke is hold in
        // holdina_cell_update_fee then moved to pending_udpate_fee when revoke_and_ack
        // is received. holding_cell_update_fee is updated when there are additional
@@ -379,7 +450,20 @@ pub(super) struct Channel<Signer: Sign> {
        /// Max to_local and to_remote outputs in a remote-generated commitment transaction
        counterparty_max_commitment_tx_output: Mutex<(u64, u64)>,
 
-       last_sent_closing_fee: Option<(u32, u64, Signature)>, // (feerate, fee, holder_sig)
+       last_sent_closing_fee: Option<(u64, Signature)>, // (fee, holder_sig)
+       target_closing_feerate_sats_per_kw: Option<u32>,
+
+       /// If our counterparty sent us a closing_signed while we were waiting for a `ChannelMonitor`
+       /// update, we need to delay processing it until later. We do that here by simply storing the
+       /// closing_signed message and handling it in `maybe_propose_closing_signed`.
+       pending_counterparty_closing_signed: Option<msgs::ClosingSigned>,
+
+       /// The minimum and maximum absolute fee we are willing to place on the closing transaction.
+       /// These are set once we reach `closing_negotiation_ready`.
+       #[cfg(test)]
+       pub(crate) closing_fee_limits: Option<(u64, u64)>,
+       #[cfg(not(test))]
+       closing_fee_limits: Option<(u64, u64)>,
 
        /// The hash of the block in which the funding transaction was included.
        funding_tx_confirmed_in: Option<BlockHash>,
@@ -422,6 +506,13 @@ pub(super) struct Channel<Signer: Sign> {
        commitment_secrets: CounterpartyCommitmentSecrets,
 
        channel_update_status: ChannelUpdateStatus,
+       /// Once we reach `closing_negotiation_ready`, we set this, indicating if closing_signed does
+       /// not complete within a single timer tick (one minute), we should force-close the channel.
+       /// This prevents us from keeping unusable channels around forever if our counterparty wishes
+       /// to DoS us.
+       /// Note that this field is reset to false on deserialization to give us a chance to connect to
+       /// our peer and start the closing_signed negotiation fresh.
+       closing_signed_in_flight: bool,
 
        /// Our counterparty's channel_announcement signatures provided in announcement_signatures.
        /// This can be used to rebroadcast the channel_announcement message later.
@@ -444,6 +535,15 @@ pub(super) struct Channel<Signer: Sign> {
        ///
        /// See-also <https://github.com/lightningnetwork/lnd/issues/4006>
        pub workaround_lnd_bug_4006: Option<msgs::FundingLocked>,
+
+       #[cfg(any(test, feature = "fuzztarget"))]
+       // When we receive an HTLC fulfill on an outbound path, we may immediately fulfill the
+       // corresponding HTLC on the inbound path. If, then, the outbound path channel is
+       // disconnected and reconnected (before we've exchange commitment_signed and revoke_and_ack
+       // messages), they may re-broadcast their update_fulfill_htlc, causing a duplicate claim. This
+       // is fine, but as a sanity check in our failure to generate the second claim, we check here
+       // that the original was a claim, and that we aren't now trying to fulfill a failed HTLC.
+       historical_inbound_htlc_fulfills: HashSet<u64>,
 }
 
 #[cfg(any(test, feature = "fuzztarget"))]
@@ -466,7 +566,9 @@ const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
 #[cfg(test)]
 pub const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
 
-/// Maximmum `funding_satoshis` value, according to the BOLT #2 specification
+pub const ANCHOR_OUTPUT_VALUE_SATOSHI: u64 = 330;
+
+/// Maximum `funding_satoshis` value, according to the BOLT #2 specification
 /// it's 2^24.
 pub const MAX_FUNDING_SATOSHIS: u64 = 1 << 24;
 
@@ -491,6 +593,7 @@ pub const MIN_DUST_LIMIT_SATOSHIS: u64 = 330;
 /// channel_id in ChannelManager.
 pub(super) enum ChannelError {
        Ignore(String),
+       Warn(String),
        Close(String),
        CloseDelayBroadcast(String),
 }
@@ -499,6 +602,7 @@ impl fmt::Debug for ChannelError {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                match self {
                        &ChannelError::Ignore(ref e) => write!(f, "Ignore : {}", e),
+                       &ChannelError::Warn(ref e) => write!(f, "Warn : {}", e),
                        &ChannelError::Close(ref e) => write!(f, "Close : {}", e),
                        &ChannelError::CloseDelayBroadcast(ref e) => write!(f, "CloseDelayBroadcast : {}", e)
                }
@@ -530,7 +634,7 @@ impl<Signer: Sign> Channel<Signer> {
        }
 
        // Constructors:
-       pub fn new_outbound<K: Deref, F: Deref>(fee_estimator: &F, keys_provider: &K, counterparty_node_id: PublicKey, channel_value_satoshis: u64, push_msat: u64, user_id: u64, config: &UserConfig) -> Result<Channel<Signer>, APIError>
+       pub fn new_outbound<K: Deref, F: Deref>(fee_estimator: &F, keys_provider: &K, counterparty_node_id: PublicKey, their_features: &InitFeatures, channel_value_satoshis: u64, push_msat: u64, user_id: u64, config: &UserConfig) -> Result<Channel<Signer>, APIError>
        where K::Target: KeysInterface<Signer = Signer>,
              F::Target: FeeEstimator,
        {
@@ -558,6 +662,16 @@ impl<Signer: Sign> Channel<Signer> {
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_provider.get_secure_random_bytes());
 
+               let shutdown_scriptpubkey = if config.channel_options.commit_upfront_shutdown_pubkey {
+                       Some(keys_provider.get_shutdown_scriptpubkey())
+               } else { None };
+
+               if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
+                       if !shutdown_scriptpubkey.is_compatible(&their_features) {
+                               return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
+                       }
+               }
+
                Ok(Channel {
                        user_id,
                        config: config.channel_options.clone(),
@@ -570,7 +684,7 @@ impl<Signer: Sign> Channel<Signer> {
                        latest_monitor_update_id: 0,
 
                        holder_signer,
-                       shutdown_pubkey: keys_provider.get_shutdown_pubkey(),
+                       shutdown_scriptpubkey,
                        destination_script: keys_provider.get_destination_script(),
 
                        cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
@@ -600,6 +714,9 @@ impl<Signer: Sign> Channel<Signer> {
                        counterparty_max_commitment_tx_output: Mutex::new((channel_value_satoshis * 1000 - push_msat, push_msat)),
 
                        last_sent_closing_fee: None,
+                       pending_counterparty_closing_signed: None,
+                       closing_fee_limits: None,
+                       target_closing_feerate_sats_per_kw: None,
 
                        funding_tx_confirmed_in: None,
                        funding_tx_confirmation_height: 0,
@@ -635,6 +752,7 @@ impl<Signer: Sign> Channel<Signer> {
                        commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
                        channel_update_status: ChannelUpdateStatus::Enabled,
+                       closing_signed_in_flight: false,
 
                        announcement_sigs: None,
 
@@ -644,6 +762,9 @@ impl<Signer: Sign> Channel<Signer> {
                        next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
 
                        workaround_lnd_bug_4006: None,
+
+                       #[cfg(any(test, feature = "fuzztarget"))]
+                       historical_inbound_htlc_fulfills: HashSet::new(),
                })
        }
 
@@ -654,7 +775,12 @@ impl<Signer: Sign> Channel<Signer> {
                if feerate_per_kw < lower_limit {
                        return Err(ChannelError::Close(format!("Peer's feerate much too low. Actual: {}. Our expected lower limit: {}", feerate_per_kw, lower_limit)));
                }
-               let upper_limit = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) as u64  * 2;
+               // We only bound the fee updates on the upper side to prevent completely absurd feerates,
+               // always accepting up to 25 sat/vByte or 10x our fee estimator's "High Priority" fee.
+               // We generally don't care too much if they set the feerate to something very high, but it
+               // could result in the channel being useless due to everything being dust.
+               let upper_limit = cmp::max(250 * 25,
+                       fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::HighPriority) as u64 * 10);
                if feerate_per_kw as u64 > upper_limit {
                        return Err(ChannelError::Close(format!("Peer's feerate much too high. Actual: {}. Our expected upper limit: {}", feerate_per_kw, upper_limit)));
                }
@@ -663,7 +789,7 @@ impl<Signer: Sign> Channel<Signer> {
 
        /// Creates a new channel from a remote sides' request for one.
        /// Assumes chain_hash has already been checked and corresponds with what we expect!
-       pub fn new_from_req<K: Deref, F: Deref>(fee_estimator: &F, keys_provider: &K, counterparty_node_id: PublicKey, their_features: InitFeatures, msg: &msgs::OpenChannel, user_id: u64, config: &UserConfig) -> Result<Channel<Signer>, ChannelError>
+       pub fn new_from_req<K: Deref, F: Deref>(fee_estimator: &F, keys_provider: &K, counterparty_node_id: PublicKey, their_features: &InitFeatures, msg: &msgs::OpenChannel, user_id: u64, config: &UserConfig) -> Result<Channel<Signer>, ChannelError>
                where K::Target: KeysInterface<Signer = Signer>,
           F::Target: FeeEstimator
        {
@@ -783,11 +909,11 @@ impl<Signer: Sign> Channel<Signer> {
                                        // Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
                                        if script.len() == 0 {
                                                None
-                                       // Peer is signaling upfront_shutdown and has provided a non-accepted scriptpubkey format. Fail the channel
-                                       } else if is_unsupported_shutdown_script(&their_features, script) {
-                                               return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided a non-accepted scriptpubkey format. script: ({})", script.to_bytes().to_hex())));
                                        } else {
-                                               Some(script.clone())
+                                               match ShutdownScript::try_from((script.clone(), their_features)) {
+                                                       Ok(shutdown_script) => Some(shutdown_script.into_inner()),
+                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script))),
+                                               }
                                        }
                                },
                                // Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
@@ -797,6 +923,16 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                } else { None };
 
+               let shutdown_scriptpubkey = if config.channel_options.commit_upfront_shutdown_pubkey {
+                       Some(keys_provider.get_shutdown_scriptpubkey())
+               } else { None };
+
+               if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
+                       if !shutdown_scriptpubkey.is_compatible(&their_features) {
+                               return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer: {}", shutdown_scriptpubkey)));
+                       }
+               }
+
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_provider.get_secure_random_bytes());
 
@@ -811,7 +947,7 @@ impl<Signer: Sign> Channel<Signer> {
                        latest_monitor_update_id: 0,
 
                        holder_signer,
-                       shutdown_pubkey: keys_provider.get_shutdown_pubkey(),
+                       shutdown_scriptpubkey,
                        destination_script: keys_provider.get_destination_script(),
 
                        cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
@@ -841,6 +977,9 @@ impl<Signer: Sign> Channel<Signer> {
                        counterparty_max_commitment_tx_output: Mutex::new((msg.push_msat, msg.funding_satoshis * 1000 - msg.push_msat)),
 
                        last_sent_closing_fee: None,
+                       pending_counterparty_closing_signed: None,
+                       closing_fee_limits: None,
+                       target_closing_feerate_sats_per_kw: None,
 
                        funding_tx_confirmed_in: None,
                        funding_tx_confirmation_height: 0,
@@ -880,6 +1019,7 @@ impl<Signer: Sign> Channel<Signer> {
                        commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
                        channel_update_status: ChannelUpdateStatus::Enabled,
+                       closing_signed_in_flight: false,
 
                        announcement_sigs: None,
 
@@ -889,6 +1029,9 @@ impl<Signer: Sign> Channel<Signer> {
                        next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
 
                        workaround_lnd_bug_4006: None,
+
+                       #[cfg(any(test, feature = "fuzztarget"))]
+                       historical_inbound_htlc_fulfills: HashSet::new(),
                };
 
                Ok(chan)
@@ -909,10 +1052,10 @@ impl<Signer: Sign> Channel<Signer> {
        /// which peer generated this transaction and "to whom" this transaction flows.
        /// Returns (the transaction info, the number of HTLC outputs which were present in the
        /// transaction, the list of HTLCs which were not ignored when building the transaction).
-       /// Note that below-dust HTLCs are included in the third return value, but not the second, and
-       /// sources are provided only for outbound HTLCs in the third return value.
+       /// Note that below-dust HTLCs are included in the fourth return value, but not the third, and
+       /// sources are provided only for outbound HTLCs in the fourth return value.
        #[inline]
-       fn build_commitment_transaction<L: Deref>(&self, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool, feerate_per_kw: u32, logger: &L) -> (CommitmentTransaction, usize, Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)>) where L::Target: Logger {
+       fn build_commitment_transaction<L: Deref>(&self, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool, logger: &L) -> (CommitmentTransaction, u32, usize, Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)>) where L::Target: Logger {
                let mut included_dust_htlcs: Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)> = Vec::new();
                let num_htlcs = self.pending_inbound_htlcs.len() + self.pending_outbound_htlcs.len();
                let mut included_non_dust_htlcs: Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)> = Vec::with_capacity(num_htlcs);
@@ -922,6 +1065,19 @@ impl<Signer: Sign> Channel<Signer> {
                let mut local_htlc_total_msat = 0;
                let mut value_to_self_msat_offset = 0;
 
+               let mut feerate_per_kw = self.feerate_per_kw;
+               if let Some((feerate, update_state)) = self.pending_update_fee {
+                       if match update_state {
+                               // Note that these match the inclusion criteria when scanning
+                               // pending_inbound_htlcs below.
+                               FeeUpdateState::RemoteAnnounced => { debug_assert!(!self.is_outbound()); !generated_by_local },
+                               FeeUpdateState::AwaitingRemoteRevokeToAnnounce => { debug_assert!(!self.is_outbound()); !generated_by_local },
+                               FeeUpdateState::Outbound => { assert!(self.is_outbound());  generated_by_local },
+                       } {
+                               feerate_per_kw = feerate;
+                       }
+               }
+
                log_trace!(logger, "Building commitment transaction number {} (really {} xor {}) for channel {} for {}, generated by {} with fee {}...",
                        commitment_number, (INITIAL_COMMITMENT_NUMBER - commitment_number),
                        get_commitment_transaction_number_obscure_factor(&self.get_holder_pubkeys().payment_point, &self.get_counterparty_pubkeys().payment_point, self.is_outbound()),
@@ -1051,6 +1207,11 @@ impl<Signer: Sign> Channel<Signer> {
 
                let mut value_to_a = if local { value_to_self } else { value_to_remote };
                let mut value_to_b = if local { value_to_remote } else { value_to_self };
+               let (funding_pubkey_a, funding_pubkey_b) = if local {
+                       (self.get_holder_pubkeys().funding_pubkey, self.get_counterparty_pubkeys().funding_pubkey)
+               } else {
+                       (self.get_counterparty_pubkeys().funding_pubkey, self.get_holder_pubkeys().funding_pubkey)
+               };
 
                if value_to_a >= (broadcaster_dust_limit_satoshis as i64) {
                        log_trace!(logger, "   ...including {} output with value {}", if local { "to_local" } else { "to_remote" }, value_to_a);
@@ -1072,6 +1233,9 @@ impl<Signer: Sign> Channel<Signer> {
                let tx = CommitmentTransaction::new_with_auxiliary_htlc_data(commitment_number,
                                                                             value_to_a as u64,
                                                                             value_to_b as u64,
+                                                                            false,
+                                                                            funding_pubkey_a,
+                                                                            funding_pubkey_b,
                                                                             keys.clone(),
                                                                             feerate_per_kw,
                                                                             &mut included_non_dust_htlcs,
@@ -1082,13 +1246,15 @@ impl<Signer: Sign> Channel<Signer> {
                htlcs_included.sort_unstable_by_key(|h| h.0.transaction_output_index.unwrap());
                htlcs_included.append(&mut included_dust_htlcs);
 
-               (tx, num_nondust_htlcs, htlcs_included)
+               (tx, feerate_per_kw, num_nondust_htlcs, htlcs_included)
        }
 
        #[inline]
        fn get_closing_scriptpubkey(&self) -> Script {
-               let channel_close_key_hash = WPubkeyHash::hash(&self.shutdown_pubkey.serialize());
-               Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&channel_close_key_hash[..]).into_script()
+               // The shutdown scriptpubkey is set on channel opening when option_upfront_shutdown_script
+               // is signaled. Otherwise, it is set when sending a shutdown message. Calling this method
+               // outside of those situations will fail.
+               self.shutdown_scriptpubkey.clone().unwrap().into_inner()
        }
 
        #[inline]
@@ -1120,60 +1286,36 @@ impl<Signer: Sign> Channel<Signer> {
 
        #[inline]
        fn build_closing_transaction(&self, proposed_total_fee_satoshis: u64, skip_remote_output: bool) -> (Transaction, u64) {
-               let txins = {
-                       let mut ins: Vec<TxIn> = Vec::new();
-                       ins.push(TxIn {
-                               previous_output: self.funding_outpoint().into_bitcoin_outpoint(),
-                               script_sig: Script::new(),
-                               sequence: 0xffffffff,
-                               witness: Vec::new(),
-                       });
-                       ins
-               };
-
                assert!(self.pending_inbound_htlcs.is_empty());
                assert!(self.pending_outbound_htlcs.is_empty());
-               let mut txouts: Vec<(TxOut, ())> = Vec::new();
+               assert!(self.pending_update_fee.is_none());
 
                let mut total_fee_satoshis = proposed_total_fee_satoshis;
-               let value_to_self: i64 = (self.value_to_self_msat as i64) / 1000 - if self.is_outbound() { total_fee_satoshis as i64 } else { 0 };
-               let value_to_remote: i64 = ((self.channel_value_satoshis * 1000 - self.value_to_self_msat) as i64 / 1000) - if self.is_outbound() { 0 } else { total_fee_satoshis as i64 };
+               let mut value_to_holder: i64 = (self.value_to_self_msat as i64) / 1000 - if self.is_outbound() { total_fee_satoshis as i64 } else { 0 };
+               let mut value_to_counterparty: i64 = ((self.channel_value_satoshis * 1000 - self.value_to_self_msat) as i64 / 1000) - if self.is_outbound() { 0 } else { total_fee_satoshis as i64 };
 
-               if value_to_self < 0 {
+               if value_to_holder < 0 {
                        assert!(self.is_outbound());
-                       total_fee_satoshis += (-value_to_self) as u64;
-               } else if value_to_remote < 0 {
+                       total_fee_satoshis += (-value_to_holder) as u64;
+               } else if value_to_counterparty < 0 {
                        assert!(!self.is_outbound());
-                       total_fee_satoshis += (-value_to_remote) as u64;
+                       total_fee_satoshis += (-value_to_counterparty) as u64;
                }
 
-               if !skip_remote_output && value_to_remote as u64 > self.holder_dust_limit_satoshis {
-                       txouts.push((TxOut {
-                               script_pubkey: self.counterparty_shutdown_scriptpubkey.clone().unwrap(),
-                               value: value_to_remote as u64
-                       }, ()));
+               if skip_remote_output || value_to_counterparty as u64 <= self.holder_dust_limit_satoshis {
+                       value_to_counterparty = 0;
                }
 
-               if value_to_self as u64 > self.holder_dust_limit_satoshis {
-                       txouts.push((TxOut {
-                               script_pubkey: self.get_closing_scriptpubkey(),
-                               value: value_to_self as u64
-                       }, ()));
+               if value_to_holder as u64 <= self.holder_dust_limit_satoshis {
+                       value_to_holder = 0;
                }
 
-               transaction_utils::sort_outputs(&mut txouts, |_, _| { cmp::Ordering::Equal }); // Ordering doesnt matter if they used our pubkey...
+               assert!(self.shutdown_scriptpubkey.is_some());
+               let holder_shutdown_script = self.get_closing_scriptpubkey();
+               let counterparty_shutdown_script = self.counterparty_shutdown_scriptpubkey.clone().unwrap();
+               let funding_outpoint = self.funding_outpoint().into_bitcoin_outpoint();
 
-               let mut outputs: Vec<TxOut> = Vec::new();
-               for out in txouts.drain(..) {
-                       outputs.push(out.0);
-               }
-
-               (Transaction {
-                       version: 2,
-                       lock_time: 0,
-                       input: txins,
-                       output: outputs,
-               }, total_fee_satoshis)
+               (build_closing_transaction(value_to_holder as u64, value_to_counterparty as u64, holder_shutdown_script, counterparty_shutdown_script, funding_outpoint), total_fee_satoshis)
        }
 
        fn funding_outpoint(&self) -> OutPoint {
@@ -1216,13 +1358,7 @@ impl<Signer: Sign> Channel<Signer> {
                make_funding_redeemscript(&self.get_holder_pubkeys().funding_pubkey, self.counterparty_funding_pubkey())
        }
 
-       /// Per HTLC, only one get_update_fail_htlc or get_update_fulfill_htlc call may be made.
-       /// In such cases we debug_assert!(false) and return a ChannelError::Ignore. Thus, will always
-       /// return Ok(_) if debug assertions are turned on or preconditions are met.
-       ///
-       /// Note that it is still possible to hit these assertions in case we find a preimage on-chain
-       /// but then have a reorg which settles on an HTLC-failure on chain.
-       fn get_update_fulfill_htlc<L: Deref>(&mut self, htlc_id_arg: u64, payment_preimage_arg: PaymentPreimage, logger: &L) -> Result<(Option<msgs::UpdateFulfillHTLC>, Option<ChannelMonitorUpdate>), ChannelError> where L::Target: Logger {
+       fn get_update_fulfill_htlc<L: Deref>(&mut self, htlc_id_arg: u64, payment_preimage_arg: PaymentPreimage, logger: &L) -> UpdateFulfillFetch where L::Target: Logger {
                // Either ChannelFunded got set (which means it won't be unset) or there is no way any
                // caller thought we could have something claimed (cause we wouldn't have accepted in an
                // incoming HTLC anyway). If we got to ShutdownComplete, callers aren't allowed to call us,
@@ -1239,6 +1375,7 @@ impl<Signer: Sign> Channel<Signer> {
                // these, but for now we just have to treat them as normal.
 
                let mut pending_idx = core::usize::MAX;
+               let mut htlc_value_msat = 0;
                for (idx, htlc) in self.pending_inbound_htlcs.iter().enumerate() {
                        if htlc.htlc_id == htlc_id_arg {
                                assert_eq!(htlc.payment_hash, payment_hash_calc);
@@ -1248,9 +1385,9 @@ impl<Signer: Sign> Channel<Signer> {
                                                if let &InboundHTLCRemovalReason::Fulfill(_) = reason {
                                                } else {
                                                        log_warn!(logger, "Have preimage and want to fulfill HTLC with payment hash {} we already failed against channel {}", log_bytes!(htlc.payment_hash.0), log_bytes!(self.channel_id()));
+                                                       debug_assert!(false, "Tried to fulfill an HTLC that was already failed");
                                                }
-                                               debug_assert!(false, "Tried to fulfill an HTLC that was already fail/fulfilled");
-                                               return Ok((None, None));
+                                               return UpdateFulfillFetch::DuplicateClaim {};
                                        },
                                        _ => {
                                                debug_assert!(false, "Have an inbound HTLC we tried to claim before it was fully committed to");
@@ -1258,11 +1395,16 @@ impl<Signer: Sign> Channel<Signer> {
                                        }
                                }
                                pending_idx = idx;
+                               htlc_value_msat = htlc.amount_msat;
                                break;
                        }
                }
                if pending_idx == core::usize::MAX {
-                       return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
+                       #[cfg(any(test, feature = "fuzztarget"))]
+                       // If we failed to find an HTLC to fulfill, make sure it was previously fulfilled and
+                       // this is simply a duplicate claim, not previously failed and we lost funds.
+                       debug_assert!(self.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
+                       return UpdateFulfillFetch::DuplicateClaim {};
                }
 
                // Now update local state:
@@ -1284,8 +1426,9 @@ impl<Signer: Sign> Channel<Signer> {
                                                if htlc_id_arg == htlc_id {
                                                        // Make sure we don't leave latest_monitor_update_id incremented here:
                                                        self.latest_monitor_update_id -= 1;
-                                                       debug_assert!(false, "Tried to fulfill an HTLC that was already fulfilled");
-                                                       return Ok((None, None));
+                                                       #[cfg(any(test, feature = "fuzztarget"))]
+                                                       debug_assert!(self.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
+                                                       return UpdateFulfillFetch::DuplicateClaim {};
                                                }
                                        },
                                        &HTLCUpdateAwaitingACK::FailHTLC { htlc_id, .. } => {
@@ -1294,7 +1437,7 @@ impl<Signer: Sign> Channel<Signer> {
                                                        // TODO: We may actually be able to switch to a fulfill here, though its
                                                        // rare enough it may not be worth the complexity burden.
                                                        debug_assert!(false, "Tried to fulfill an HTLC that was already failed");
-                                                       return Ok((None, Some(monitor_update)));
+                                                       return UpdateFulfillFetch::NewClaim { monitor_update, htlc_value_msat, msg: None };
                                                }
                                        },
                                        _ => {}
@@ -1304,52 +1447,60 @@ impl<Signer: Sign> Channel<Signer> {
                        self.holding_cell_htlc_updates.push(HTLCUpdateAwaitingACK::ClaimHTLC {
                                payment_preimage: payment_preimage_arg, htlc_id: htlc_id_arg,
                        });
-                       return Ok((None, Some(monitor_update)));
+                       #[cfg(any(test, feature = "fuzztarget"))]
+                       self.historical_inbound_htlc_fulfills.insert(htlc_id_arg);
+                       return UpdateFulfillFetch::NewClaim { monitor_update, htlc_value_msat, msg: None };
                }
+               #[cfg(any(test, feature = "fuzztarget"))]
+               self.historical_inbound_htlc_fulfills.insert(htlc_id_arg);
 
                {
                        let htlc = &mut self.pending_inbound_htlcs[pending_idx];
                        if let InboundHTLCState::Committed = htlc.state {
                        } else {
                                debug_assert!(false, "Have an inbound HTLC we tried to claim before it was fully committed to");
-                               return Ok((None, Some(monitor_update)));
+                               return UpdateFulfillFetch::NewClaim { monitor_update, htlc_value_msat, msg: None };
                        }
                        log_trace!(logger, "Upgrading HTLC {} to LocalRemoved with a Fulfill in channel {}!", log_bytes!(htlc.payment_hash.0), log_bytes!(self.channel_id));
                        htlc.state = InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::Fulfill(payment_preimage_arg.clone()));
                }
 
-               Ok((Some(msgs::UpdateFulfillHTLC {
-                       channel_id: self.channel_id(),
-                       htlc_id: htlc_id_arg,
-                       payment_preimage: payment_preimage_arg,
-               }), Some(monitor_update)))
+               UpdateFulfillFetch::NewClaim {
+                       monitor_update,
+                       htlc_value_msat,
+                       msg: Some(msgs::UpdateFulfillHTLC {
+                               channel_id: self.channel_id(),
+                               htlc_id: htlc_id_arg,
+                               payment_preimage: payment_preimage_arg,
+                       }),
+               }
        }
 
-       pub fn get_update_fulfill_htlc_and_commit<L: Deref>(&mut self, htlc_id: u64, payment_preimage: PaymentPreimage, logger: &L) -> Result<(Option<(msgs::UpdateFulfillHTLC, msgs::CommitmentSigned)>, Option<ChannelMonitorUpdate>), ChannelError> where L::Target: Logger {
-               match self.get_update_fulfill_htlc(htlc_id, payment_preimage, logger)? {
-                       (Some(update_fulfill_htlc), Some(mut monitor_update)) => {
-                               let (commitment, mut additional_update) = self.send_commitment_no_status_check(logger)?;
+       pub fn get_update_fulfill_htlc_and_commit<L: Deref>(&mut self, htlc_id: u64, payment_preimage: PaymentPreimage, logger: &L) -> Result<UpdateFulfillCommitFetch, (ChannelError, ChannelMonitorUpdate)> where L::Target: Logger {
+               match self.get_update_fulfill_htlc(htlc_id, payment_preimage, logger) {
+                       UpdateFulfillFetch::NewClaim { mut monitor_update, htlc_value_msat, msg: Some(update_fulfill_htlc) } => {
+                               let (commitment, mut additional_update) = match self.send_commitment_no_status_check(logger) {
+                                       Err(e) => return Err((e, monitor_update)),
+                                       Ok(res) => res
+                               };
                                // send_commitment_no_status_check may bump latest_monitor_id but we want them to be
                                // strictly increasing by one, so decrement it here.
                                self.latest_monitor_update_id = monitor_update.update_id;
                                monitor_update.updates.append(&mut additional_update.updates);
-                               Ok((Some((update_fulfill_htlc, commitment)), Some(monitor_update)))
+                               Ok(UpdateFulfillCommitFetch::NewClaim { monitor_update, htlc_value_msat, msgs: Some((update_fulfill_htlc, commitment)) })
                        },
-                       (Some(update_fulfill_htlc), None) => {
-                               let (commitment, monitor_update) = self.send_commitment_no_status_check(logger)?;
-                               Ok((Some((update_fulfill_htlc, commitment)), Some(monitor_update)))
-                       },
-                       (None, Some(monitor_update)) => Ok((None, Some(monitor_update))),
-                       (None, None) => Ok((None, None))
+                       UpdateFulfillFetch::NewClaim { monitor_update, htlc_value_msat, msg: None } =>
+                               Ok(UpdateFulfillCommitFetch::NewClaim { monitor_update, htlc_value_msat, msgs: None }),
+                       UpdateFulfillFetch::DuplicateClaim {} => Ok(UpdateFulfillCommitFetch::DuplicateClaim {}),
                }
        }
 
-       /// Per HTLC, only one get_update_fail_htlc or get_update_fulfill_htlc call may be made.
-       /// In such cases we debug_assert!(false) and return a ChannelError::Ignore. Thus, will always
-       /// return Ok(_) if debug assertions are turned on or preconditions are met.
-       ///
-       /// Note that it is still possible to hit these assertions in case we find a preimage on-chain
-       /// but then have a reorg which settles on an HTLC-failure on chain.
+       /// We can only have one resolution per HTLC. In some cases around reconnect, we may fulfill
+       /// an HTLC more than once or fulfill once and then attempt to fail after reconnect. We cannot,
+       /// however, fail more than once as we wait for an upstream failure to be irrevocably committed
+       /// before we fail backwards.
+       /// If we do fail twice, we debug_assert!(false) and return Ok(None). Thus, will always return
+       /// Ok(_) if debug assertions are turned on or preconditions are met.
        pub fn get_update_fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, logger: &L) -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> where L::Target: Logger {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        panic!("Was asked to fail an HTLC when channel was not in an operational state");
@@ -1365,8 +1516,11 @@ impl<Signer: Sign> Channel<Signer> {
                        if htlc.htlc_id == htlc_id_arg {
                                match htlc.state {
                                        InboundHTLCState::Committed => {},
-                                       InboundHTLCState::LocalRemoved(_) => {
-                                               debug_assert!(false, "Tried to fail an HTLC that was already fail/fulfilled");
+                                       InboundHTLCState::LocalRemoved(ref reason) => {
+                                               if let &InboundHTLCRemovalReason::Fulfill(_) = reason {
+                                               } else {
+                                                       debug_assert!(false, "Tried to fail an HTLC that was already failed");
+                                               }
                                                return Ok(None);
                                        },
                                        _ => {
@@ -1378,7 +1532,11 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
                if pending_idx == core::usize::MAX {
-                       return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
+                       #[cfg(any(test, feature = "fuzztarget"))]
+                       // If we failed to find an HTLC to fail, make sure it was previously fulfilled and this
+                       // is simply a duplicate fail, not previously failed and we failed-back too early.
+                       debug_assert!(self.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
+                       return Ok(None);
                }
 
                // Now update local state:
@@ -1387,8 +1545,9 @@ impl<Signer: Sign> Channel<Signer> {
                                match pending_update {
                                        &HTLCUpdateAwaitingACK::ClaimHTLC { htlc_id, .. } => {
                                                if htlc_id_arg == htlc_id {
-                                                       debug_assert!(false, "Tried to fail an HTLC that was already fulfilled");
-                                                       return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
+                                                       #[cfg(any(test, feature = "fuzztarget"))]
+                                                       debug_assert!(self.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
+                                                       return Ok(None);
                                                }
                                        },
                                        &HTLCUpdateAwaitingACK::FailHTLC { htlc_id, .. } => {
@@ -1423,7 +1582,7 @@ impl<Signer: Sign> Channel<Signer> {
 
        // Message handlers:
 
-       pub fn accept_channel(&mut self, msg: &msgs::AcceptChannel, config: &UserConfig, their_features: InitFeatures) -> Result<(), ChannelError> {
+       pub fn accept_channel(&mut self, msg: &msgs::AcceptChannel, config: &UserConfig, their_features: &InitFeatures) -> Result<(), ChannelError> {
                // Check sanity of message fields:
                if !self.is_outbound() {
                        return Err(ChannelError::Close("Got an accept_channel message from an inbound peer".to_owned()));
@@ -1494,11 +1653,11 @@ impl<Signer: Sign> Channel<Signer> {
                                        // Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
                                        if script.len() == 0 {
                                                None
-                                       // Peer is signaling upfront_shutdown and has provided a non-accepted scriptpubkey format. Fail the channel
-                                       } else if is_unsupported_shutdown_script(&their_features, script) {
-                                               return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided a non-accepted scriptpubkey format. script: ({})", script.to_bytes().to_hex())));
                                        } else {
-                                               Some(script.clone())
+                                               match ShutdownScript::try_from((script.clone(), their_features)) {
+                                                       Ok(shutdown_script) => Some(shutdown_script.into_inner()),
+                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script))),
+                                               }
                                        }
                                },
                                // Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
@@ -1540,7 +1699,7 @@ impl<Signer: Sign> Channel<Signer> {
                let funding_script = self.get_funding_redeemscript();
 
                let keys = self.build_holder_transaction_keys(self.cur_holder_commitment_transaction_number)?;
-               let initial_commitment_tx = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &keys, true, false, self.feerate_per_kw, logger).0;
+               let initial_commitment_tx = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &keys, true, false, logger).0;
                {
                        let trusted_tx = initial_commitment_tx.trust();
                        let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
@@ -1554,7 +1713,7 @@ impl<Signer: Sign> Channel<Signer> {
                }
 
                let counterparty_keys = self.build_remote_transaction_keys()?;
-               let counterparty_initial_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, self.feerate_per_kw, logger).0;
+               let counterparty_initial_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).0;
 
                let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
                let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
@@ -1615,13 +1774,17 @@ impl<Signer: Sign> Channel<Signer> {
                        self.counterparty_funding_pubkey()
                );
 
+               self.holder_signer.validate_holder_commitment(&holder_commitment_tx)
+                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
+
                // Now that we're past error-generating stuff, update our local state:
 
                let funding_redeemscript = self.get_funding_redeemscript();
                let funding_txo_script = funding_redeemscript.to_v0_p2wsh();
                let obscure_factor = get_commitment_transaction_number_obscure_factor(&self.get_holder_pubkeys().payment_point, &self.get_counterparty_pubkeys().payment_point, self.is_outbound());
+               let shutdown_script = self.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
                let channel_monitor = ChannelMonitor::new(self.secp_ctx.clone(), self.holder_signer.clone(),
-                                                         &self.shutdown_pubkey, self.get_holder_selected_contest_delay(),
+                                                         shutdown_script, self.get_holder_selected_contest_delay(),
                                                          &self.destination_script, (funding_txo, funding_txo_script.clone()),
                                                          &self.channel_transaction_parameters,
                                                          funding_redeemscript.clone(), self.channel_value_satoshis,
@@ -1661,7 +1824,7 @@ impl<Signer: Sign> Channel<Signer> {
                let funding_script = self.get_funding_redeemscript();
 
                let counterparty_keys = self.build_remote_transaction_keys()?;
-               let counterparty_initial_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, self.feerate_per_kw, logger).0;
+               let counterparty_initial_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).0;
                let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
                let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
 
@@ -1669,7 +1832,7 @@ impl<Signer: Sign> Channel<Signer> {
                        log_bytes!(self.channel_id()), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));
 
                let holder_signer = self.build_holder_transaction_keys(self.cur_holder_commitment_transaction_number)?;
-               let initial_commitment_tx = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &holder_signer, true, false, self.feerate_per_kw, logger).0;
+               let initial_commitment_tx = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &holder_signer, true, false, logger).0;
                {
                        let trusted_tx = initial_commitment_tx.trust();
                        let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
@@ -1688,13 +1851,17 @@ impl<Signer: Sign> Channel<Signer> {
                        self.counterparty_funding_pubkey()
                );
 
+               self.holder_signer.validate_holder_commitment(&holder_commitment_tx)
+                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
+
 
                let funding_redeemscript = self.get_funding_redeemscript();
                let funding_txo = self.get_funding_txo().unwrap();
                let funding_txo_script = funding_redeemscript.to_v0_p2wsh();
                let obscure_factor = get_commitment_transaction_number_obscure_factor(&self.get_holder_pubkeys().payment_point, &self.get_counterparty_pubkeys().payment_point, self.is_outbound());
+               let shutdown_script = self.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
                let channel_monitor = ChannelMonitor::new(self.secp_ctx.clone(), self.holder_signer.clone(),
-                                                         &self.shutdown_pubkey, self.get_holder_selected_contest_delay(),
+                                                         shutdown_script, self.get_holder_selected_contest_delay(),
                                                          &self.destination_script, (funding_txo, funding_txo_script),
                                                          &self.channel_transaction_parameters,
                                                          funding_redeemscript.clone(), self.channel_value_satoshis,
@@ -1750,32 +1917,63 @@ impl<Signer: Sign> Channel<Signer> {
                Ok(())
        }
 
-       /// Returns (inbound_htlc_count, htlc_inbound_value_msat)
-       fn get_inbound_pending_htlc_stats(&self) -> (u32, u64) {
-               let mut htlc_inbound_value_msat = 0;
+       /// Returns a HTLCStats about inbound pending htlcs
+       fn get_inbound_pending_htlc_stats(&self) -> HTLCStats {
+               let mut stats = HTLCStats {
+                       pending_htlcs: self.pending_inbound_htlcs.len() as u32,
+                       pending_htlcs_value_msat: 0,
+                       on_counterparty_tx_dust_exposure_msat: 0,
+                       on_holder_tx_dust_exposure_msat: 0,
+               };
+
+               let counterparty_dust_limit_timeout_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               let holder_dust_limit_success_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
                for ref htlc in self.pending_inbound_htlcs.iter() {
-                       htlc_inbound_value_msat += htlc.amount_msat;
+                       stats.pending_htlcs_value_msat += htlc.amount_msat;
+                       if htlc.amount_msat / 1000 < counterparty_dust_limit_timeout_sat {
+                               stats.on_counterparty_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
+                       if htlc.amount_msat / 1000 < holder_dust_limit_success_sat {
+                               stats.on_holder_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
                }
-               (self.pending_inbound_htlcs.len() as u32, htlc_inbound_value_msat)
+               stats
        }
 
-       /// Returns (outbound_htlc_count, htlc_outbound_value_msat) *including* pending adds in our
-       /// holding cell.
-       fn get_outbound_pending_htlc_stats(&self) -> (u32, u64) {
-               let mut htlc_outbound_value_msat = 0;
+       /// Returns a HTLCStats about pending outbound htlcs, *including* pending adds in our holding cell.
+       fn get_outbound_pending_htlc_stats(&self) -> HTLCStats {
+               let mut stats = HTLCStats {
+                       pending_htlcs: self.pending_outbound_htlcs.len() as u32,
+                       pending_htlcs_value_msat: 0,
+                       on_counterparty_tx_dust_exposure_msat: 0,
+                       on_holder_tx_dust_exposure_msat: 0,
+               };
+
+               let counterparty_dust_limit_success_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               let holder_dust_limit_timeout_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
                for ref htlc in self.pending_outbound_htlcs.iter() {
-                       htlc_outbound_value_msat += htlc.amount_msat;
+                       stats.pending_htlcs_value_msat += htlc.amount_msat;
+                       if htlc.amount_msat / 1000 < counterparty_dust_limit_success_sat {
+                               stats.on_counterparty_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
+                       if htlc.amount_msat / 1000 < holder_dust_limit_timeout_sat {
+                               stats.on_holder_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
                }
 
-               let mut htlc_outbound_count = self.pending_outbound_htlcs.len();
                for update in self.holding_cell_htlc_updates.iter() {
                        if let &HTLCUpdateAwaitingACK::AddHTLC { ref amount_msat, .. } = update {
-                               htlc_outbound_count += 1;
-                               htlc_outbound_value_msat += amount_msat;
+                               stats.pending_htlcs += 1;
+                               stats.pending_htlcs_value_msat += amount_msat;
+                               if *amount_msat / 1000 < counterparty_dust_limit_success_sat {
+                                       stats.on_counterparty_tx_dust_exposure_msat += amount_msat;
+                               }
+                               if *amount_msat / 1000 < holder_dust_limit_timeout_sat {
+                                       stats.on_holder_tx_dust_exposure_msat += amount_msat;
+                               }
                        }
                }
-
-               (htlc_outbound_count as u32, htlc_outbound_value_msat)
+               stats
        }
 
        /// Get the available (ie not including pending HTLCs) inbound and outbound balance in msat.
@@ -1787,11 +1985,11 @@ impl<Signer: Sign> Channel<Signer> {
                (
                        cmp::max(self.channel_value_satoshis as i64 * 1000
                                - self.value_to_self_msat as i64
-                               - self.get_inbound_pending_htlc_stats().1 as i64
+                               - self.get_inbound_pending_htlc_stats().pending_htlcs_value_msat as i64
                                - Self::get_holder_selected_channel_reserve_satoshis(self.channel_value_satoshis) as i64 * 1000,
                        0) as u64,
                        cmp::max(self.value_to_self_msat as i64
-                               - self.get_outbound_pending_htlc_stats().1 as i64
+                               - self.get_outbound_pending_htlc_stats().pending_htlcs_value_msat as i64
                                - self.counterparty_selected_channel_reserve_satoshis.unwrap_or(0) as i64 * 1000,
                        0) as u64
                )
@@ -2003,12 +2201,13 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Close(format!("Remote side tried to send less than our minimum HTLC value. Lower limit: ({}). Actual: ({})", self.holder_htlc_minimum_msat, msg.amount_msat)));
                }
 
-               let (inbound_htlc_count, htlc_inbound_value_msat) = self.get_inbound_pending_htlc_stats();
-               if inbound_htlc_count + 1 > OUR_MAX_HTLCS as u32 {
+               let inbound_stats = self.get_inbound_pending_htlc_stats();
+               let outbound_stats = self.get_outbound_pending_htlc_stats();
+               if inbound_stats.pending_htlcs + 1 > OUR_MAX_HTLCS as u32 {
                        return Err(ChannelError::Close(format!("Remote tried to push more than our max accepted HTLCs ({})", OUR_MAX_HTLCS)));
                }
                let holder_max_htlc_value_in_flight_msat = Channel::<Signer>::get_holder_max_htlc_value_in_flight_msat(self.channel_value_satoshis);
-               if htlc_inbound_value_msat + msg.amount_msat > holder_max_htlc_value_in_flight_msat {
+               if inbound_stats.pending_htlcs_value_msat + msg.amount_msat > holder_max_htlc_value_in_flight_msat {
                        return Err(ChannelError::Close(format!("Remote HTLC add would put them over our max HTLC value ({})", holder_max_htlc_value_in_flight_msat)));
                }
                // Check holder_selected_channel_reserve_satoshis (we're getting paid, so they have to at least meet
@@ -2032,8 +2231,28 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
 
+               let exposure_dust_limit_timeout_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               if msg.amount_msat / 1000 < exposure_dust_limit_timeout_sats {
+                       let on_counterparty_tx_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat + msg.amount_msat;
+                       if on_counterparty_tx_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on counterparty commitment tx",
+                                       on_counterparty_tx_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat());
+                               pending_forward_status = create_pending_htlc_status(self, pending_forward_status, 0x1000|7);
+                       }
+               }
+
+               let exposure_dust_limit_success_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
+               if msg.amount_msat / 1000 < exposure_dust_limit_success_sats {
+                       let on_holder_tx_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat + msg.amount_msat;
+                       if on_holder_tx_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
+                                       on_holder_tx_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat());
+                               pending_forward_status = create_pending_htlc_status(self, pending_forward_status, 0x1000|7);
+                       }
+               }
+
                let pending_value_to_self_msat =
-                       self.value_to_self_msat + htlc_inbound_value_msat - removed_outbound_total_msat;
+                       self.value_to_self_msat + inbound_stats.pending_htlcs_value_msat - removed_outbound_total_msat;
                let pending_remote_value_msat =
                        self.channel_value_satoshis * 1000 - pending_value_to_self_msat;
                if pending_remote_value_msat < msg.amount_msat {
@@ -2108,7 +2327,7 @@ impl<Signer: Sign> Channel<Signer> {
 
        /// Marks an outbound HTLC which we have received update_fail/fulfill/malformed
        #[inline]
-       fn mark_outbound_htlc_removed(&mut self, htlc_id: u64, check_preimage: Option<PaymentHash>, fail_reason: Option<HTLCFailReason>) -> Result<&HTLCSource, ChannelError> {
+       fn mark_outbound_htlc_removed(&mut self, htlc_id: u64, check_preimage: Option<PaymentHash>, fail_reason: Option<HTLCFailReason>) -> Result<&OutboundHTLCOutput, ChannelError> {
                for htlc in self.pending_outbound_htlcs.iter_mut() {
                        if htlc.htlc_id == htlc_id {
                                match check_preimage {
@@ -2127,13 +2346,13 @@ impl<Signer: Sign> Channel<Signer> {
                                        OutboundHTLCState::AwaitingRemoteRevokeToRemove(_) | OutboundHTLCState::AwaitingRemovedRemoteRevoke(_) | OutboundHTLCState::RemoteRemoved(_) =>
                                                return Err(ChannelError::Close(format!("Remote tried to fulfill/fail HTLC ({}) that they'd already fulfilled/failed", htlc_id))),
                                }
-                               return Ok(&htlc.source);
+                               return Ok(htlc);
                        }
                }
                Err(ChannelError::Close("Remote tried to fulfill/fail an HTLC we couldn't find".to_owned()))
        }
 
-       pub fn update_fulfill_htlc(&mut self, msg: &msgs::UpdateFulfillHTLC) -> Result<HTLCSource, ChannelError> {
+       pub fn update_fulfill_htlc(&mut self, msg: &msgs::UpdateFulfillHTLC) -> Result<(HTLCSource, u64), ChannelError> {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(ChannelError::Close("Got fulfill HTLC message when channel was not in an operational state".to_owned()));
                }
@@ -2142,7 +2361,7 @@ impl<Signer: Sign> Channel<Signer> {
                }
 
                let payment_hash = PaymentHash(Sha256::hash(&msg.payment_preimage.0[..]).into_inner());
-               self.mark_outbound_htlc_removed(msg.htlc_id, Some(payment_hash), None).map(|source| source.clone())
+               self.mark_outbound_htlc_removed(msg.htlc_id, Some(payment_hash), None).map(|htlc| (htlc.source.clone(), htlc.amount_msat))
        }
 
        pub fn update_fail_htlc(&mut self, msg: &msgs::UpdateFailHTLC, fail_reason: HTLCFailReason) -> Result<(), ChannelError> {
@@ -2169,9 +2388,8 @@ impl<Signer: Sign> Channel<Signer> {
                Ok(())
        }
 
-       pub fn commitment_signed<F: Deref, L: Deref>(&mut self, msg: &msgs::CommitmentSigned, fee_estimator: &F, logger: &L) -> Result<(msgs::RevokeAndACK, Option<msgs::CommitmentSigned>, Option<msgs::ClosingSigned>, ChannelMonitorUpdate), (Option<ChannelMonitorUpdate>, ChannelError)>
-       where F::Target: FeeEstimator,
-                               L::Target: Logger
+       pub fn commitment_signed<L: Deref>(&mut self, msg: &msgs::CommitmentSigned, logger: &L) -> Result<(msgs::RevokeAndACK, Option<msgs::CommitmentSigned>, ChannelMonitorUpdate), (Option<ChannelMonitorUpdate>, ChannelError)>
+               where L::Target: Logger
        {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err((None, ChannelError::Close("Got commitment signed message when channel was not in an operational state".to_owned())));
@@ -2187,16 +2405,8 @@ impl<Signer: Sign> Channel<Signer> {
 
                let keys = self.build_holder_transaction_keys(self.cur_holder_commitment_transaction_number).map_err(|e| (None, e))?;
 
-               let mut update_fee = false;
-               let feerate_per_kw = if !self.is_outbound() && self.pending_update_fee.is_some() {
-                       update_fee = true;
-                       self.pending_update_fee.unwrap()
-               } else {
-                       self.feerate_per_kw
-               };
-
-               let (num_htlcs, mut htlcs_cloned, commitment_tx, commitment_txid) = {
-                       let commitment_tx = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &keys, true, false, feerate_per_kw, logger);
+               let (num_htlcs, mut htlcs_cloned, commitment_tx, commitment_txid, feerate_per_kw) = {
+                       let commitment_tx = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &keys, true, false, logger);
                        let commitment_txid = {
                                let trusted_tx = commitment_tx.0.trust();
                                let bitcoin_tx = trusted_tx.built_transaction();
@@ -2211,12 +2421,17 @@ impl<Signer: Sign> Channel<Signer> {
                                }
                                bitcoin_tx.txid
                        };
-                       let htlcs_cloned: Vec<_> = commitment_tx.2.iter().map(|htlc| (htlc.0.clone(), htlc.1.map(|h| h.clone()))).collect();
-                       (commitment_tx.1, htlcs_cloned, commitment_tx.0, commitment_txid)
+                       let htlcs_cloned: Vec<_> = commitment_tx.3.iter().map(|htlc| (htlc.0.clone(), htlc.1.map(|h| h.clone()))).collect();
+                       (commitment_tx.2, htlcs_cloned, commitment_tx.0, commitment_txid, commitment_tx.1)
                };
 
+               // If our counterparty updated the channel fee in this commitment transaction, check that
+               // they can actually afford the new fee now.
+               let update_fee = if let Some((_, update_state)) = self.pending_update_fee {
+                       update_state == FeeUpdateState::RemoteAnnounced
+               } else { false };
+               if update_fee { debug_assert!(!self.is_outbound()); }
                let total_fee = feerate_per_kw as u64 * (COMMITMENT_TX_BASE_WEIGHT + (num_htlcs as u64) * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000;
-               //If channel fee was updated by funder confirm funder can afford the new fee rate when applied to the current local commitment transaction
                if update_fee {
                        let counterparty_reserve_we_require = Channel::<Signer>::get_holder_selected_channel_reserve_satoshis(self.channel_value_satoshis);
                        if self.channel_value_satoshis - self.value_to_self_msat / 1000 < total_fee + counterparty_reserve_we_require {
@@ -2276,20 +2491,16 @@ impl<Signer: Sign> Channel<Signer> {
                );
 
                let next_per_commitment_point = self.holder_signer.get_per_commitment_point(self.cur_holder_commitment_transaction_number - 1, &self.secp_ctx);
+               self.holder_signer.validate_holder_commitment(&holder_commitment_tx)
+                       .map_err(|_| (None, ChannelError::Close("Failed to validate our commitment".to_owned())))?;
                let per_commitment_secret = self.holder_signer.release_commitment_secret(self.cur_holder_commitment_transaction_number + 1);
 
                // Update state now that we've passed all the can-fail calls...
                let mut need_commitment = false;
-               if !self.is_outbound() {
-                       if let Some(fee_update) = self.pending_update_fee {
-                               self.feerate_per_kw = fee_update;
-                               // We later use the presence of pending_update_fee to indicate we should generate a
-                               // commitment_signed upon receipt of revoke_and_ack, so we can only set it to None
-                               // if we're not awaiting a revoke (ie will send a commitment_signed now).
-                               if (self.channel_state & ChannelState::AwaitingRemoteRevoke as u32) == 0 {
-                                       need_commitment = true;
-                                       self.pending_update_fee = None;
-                               }
+               if let &mut Some((_, ref mut update_state)) = &mut self.pending_update_fee {
+                       if *update_state == FeeUpdateState::RemoteAnnounced {
+                               *update_state = FeeUpdateState::AwaitingRemoteRevokeToAnnounce;
+                               need_commitment = true;
                        }
                }
 
@@ -2346,12 +2557,10 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                        log_debug!(logger, "Received valid commitment_signed from peer in channel {}, updated HTLC state but awaiting a monitor update resolution to reply.",
                                log_bytes!(self.channel_id));
-                       // TODO: Call maybe_propose_first_closing_signed on restoration (or call it here and
-                       // re-send the message on restoration)
                        return Err((Some(monitor_update), ChannelError::Ignore("Previous monitor update failure prevented generation of RAA".to_owned())));
                }
 
-               let (commitment_signed, closing_signed) = if need_commitment && (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == 0 {
+               let commitment_signed = if need_commitment && (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == 0 {
                        // If we're AwaitingRemoteRevoke we can't send a new commitment here, but that's ok -
                        // we'll send one right away when we get the revoke_and_ack when we
                        // free_holding_cell_htlcs().
@@ -2360,10 +2569,8 @@ impl<Signer: Sign> Channel<Signer> {
                        // strictly increasing by one, so decrement it here.
                        self.latest_monitor_update_id = monitor_update.update_id;
                        monitor_update.updates.append(&mut additional_update.updates);
-                       (Some(msg), None)
-               } else if !need_commitment {
-                       (None, self.maybe_propose_first_closing_signed(fee_estimator))
-               } else { (None, None) };
+                       Some(msg)
+               } else { None };
 
                log_debug!(logger, "Received valid commitment_signed from peer in channel {}, updating HTLC state and responding with{} a revoke_and_ack.",
                        log_bytes!(self.channel_id()), if commitment_signed.is_some() { " our own commitment_signed and" } else { "" });
@@ -2372,7 +2579,7 @@ impl<Signer: Sign> Channel<Signer> {
                        channel_id: self.channel_id,
                        per_commitment_secret,
                        next_per_commitment_point,
-               }, commitment_signed, closing_signed, monitor_update))
+               }, commitment_signed, monitor_update))
        }
 
        /// Public version of the below, checking relevant preconditions first.
@@ -2435,24 +2642,28 @@ impl<Signer: Sign> Channel<Signer> {
                                                }
                                        },
                                        &HTLCUpdateAwaitingACK::ClaimHTLC { ref payment_preimage, htlc_id, .. } => {
-                                               match self.get_update_fulfill_htlc(htlc_id, *payment_preimage, logger) {
-                                                       Ok((update_fulfill_msg_option, additional_monitor_update_opt)) => {
-                                                               update_fulfill_htlcs.push(update_fulfill_msg_option.unwrap());
-                                                               if let Some(mut additional_monitor_update) = additional_monitor_update_opt {
-                                                                       monitor_update.updates.append(&mut additional_monitor_update.updates);
-                                                               }
-                                                       },
-                                                       Err(e) => {
-                                                               if let ChannelError::Ignore(_) = e {}
-                                                               else {
-                                                                       panic!("Got a non-IgnoreError action trying to fulfill holding cell HTLC");
-                                                               }
-                                                       }
-                                               }
+                                               // If an HTLC claim was previously added to the holding cell (via
+                                               // `get_update_fulfill_htlc`, then generating the claim message itself must
+                                               // not fail - any in between attempts to claim the HTLC will have resulted
+                                               // in it hitting the holding cell again and we cannot change the state of a
+                                               // holding cell HTLC from fulfill to anything else.
+                                               let (update_fulfill_msg_option, mut additional_monitor_update) =
+                                                       if let UpdateFulfillFetch::NewClaim { msg, monitor_update, .. } = self.get_update_fulfill_htlc(htlc_id, *payment_preimage, logger) {
+                                                               (msg, monitor_update)
+                                                       } else { unreachable!() };
+                                               update_fulfill_htlcs.push(update_fulfill_msg_option.unwrap());
+                                               monitor_update.updates.append(&mut additional_monitor_update.updates);
                                        },
                                        &HTLCUpdateAwaitingACK::FailHTLC { htlc_id, ref err_packet } => {
                                                match self.get_update_fail_htlc(htlc_id, err_packet.clone(), logger) {
-                                                       Ok(update_fail_msg_option) => update_fail_htlcs.push(update_fail_msg_option.unwrap()),
+                                                       Ok(update_fail_msg_option) => {
+                                                               // If an HTLC failure was previously added to the holding cell (via
+                                                               // `get_update_fail_htlc`) then generating the fail message itself
+                                                               // must not fail - we should never end up in a state where we
+                                                               // double-fail an HTLC or fail-then-claim an HTLC as it indicates
+                                                               // we didn't wait for a full revocation before failing.
+                                                               update_fail_htlcs.push(update_fail_msg_option.unwrap())
+                                                       },
                                                        Err(e) => {
                                                                if let ChannelError::Ignore(_) = e {}
                                                                else {
@@ -2466,8 +2677,9 @@ impl<Signer: Sign> Channel<Signer> {
                        if update_add_htlcs.is_empty() && update_fulfill_htlcs.is_empty() && update_fail_htlcs.is_empty() && self.holding_cell_update_fee.is_none() {
                                return Ok((None, htlcs_to_fail));
                        }
-                       let update_fee = if let Some(feerate) = self.holding_cell_update_fee {
-                               self.pending_update_fee = self.holding_cell_update_fee.take();
+                       let update_fee = if let Some(feerate) = self.holding_cell_update_fee.take() {
+                               assert!(self.is_outbound());
+                               self.pending_update_fee = Some((feerate, FeeUpdateState::Outbound));
                                Some(msgs::UpdateFee {
                                        channel_id: self.channel_id,
                                        feerate_per_kw: feerate as u32,
@@ -2504,9 +2716,8 @@ impl<Signer: Sign> Channel<Signer> {
        /// waiting on this revoke_and_ack. The generation of this new commitment_signed may also fail,
        /// generating an appropriate error *after* the channel state has been updated based on the
        /// revoke_and_ack message.
-       pub fn revoke_and_ack<F: Deref, L: Deref>(&mut self, msg: &msgs::RevokeAndACK, fee_estimator: &F, logger: &L) -> Result<(Option<msgs::CommitmentUpdate>, Vec<(PendingHTLCInfo, u64)>, Vec<(HTLCSource, PaymentHash, HTLCFailReason)>, Option<msgs::ClosingSigned>, ChannelMonitorUpdate, Vec<(HTLCSource, PaymentHash)>), ChannelError>
-               where F::Target: FeeEstimator,
-                                       L::Target: Logger,
+       pub fn revoke_and_ack<L: Deref>(&mut self, msg: &msgs::RevokeAndACK, logger: &L) -> Result<(Option<msgs::CommitmentUpdate>, Vec<(PendingHTLCInfo, u64)>, Vec<(HTLCSource, PaymentHash, HTLCFailReason)>, ChannelMonitorUpdate, Vec<(HTLCSource, PaymentHash)>), ChannelError>
+               where L::Target: Logger,
        {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(ChannelError::Close("Got revoke/ACK message when channel was not in an operational state".to_owned()));
@@ -2518,8 +2729,10 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Close("Peer sent revoke_and_ack after we'd started exchanging closing_signeds".to_owned()));
                }
 
+               let secret = secp_check!(SecretKey::from_slice(&msg.per_commitment_secret), "Peer provided an invalid per_commitment_secret".to_owned());
+
                if let Some(counterparty_prev_commitment_point) = self.counterparty_prev_commitment_point {
-                       if PublicKey::from_secret_key(&self.secp_ctx, &secp_check!(SecretKey::from_slice(&msg.per_commitment_secret), "Peer provided an invalid per_commitment_secret".to_owned())) != counterparty_prev_commitment_point {
+                       if PublicKey::from_secret_key(&self.secp_ctx, &secret) != counterparty_prev_commitment_point {
                                return Err(ChannelError::Close("Got a revoke commitment secret which didn't correspond to their current pubkey".to_owned()));
                        }
                }
@@ -2541,6 +2754,11 @@ impl<Signer: Sign> Channel<Signer> {
                        *self.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
                }
 
+               self.holder_signer.validate_counterparty_revocation(
+                       self.cur_counterparty_commitment_transaction_number + 1,
+                       &secret
+               ).map_err(|_| ChannelError::Close("Failed to validate revocation from peer".to_owned()))?;
+
                self.commitment_secrets.provide_secret(self.cur_counterparty_commitment_transaction_number + 1, msg.per_commitment_secret)
                        .map_err(|_| ChannelError::Close("Previous secrets did not match new one".to_owned()))?;
                self.latest_monitor_update_id += 1;
@@ -2651,21 +2869,22 @@ impl<Signer: Sign> Channel<Signer> {
                }
                self.value_to_self_msat = (self.value_to_self_msat as i64 + value_to_self_msat_diff) as u64;
 
-               if self.is_outbound() {
-                       if let Some(feerate) = self.pending_update_fee.take() {
-                               self.feerate_per_kw = feerate;
-                       }
-               } else {
-                       if let Some(feerate) = self.pending_update_fee {
-                               // Because a node cannot send two commitment_signeds in a row without getting a
-                               // revoke_and_ack from us (as it would otherwise not know the per_commitment_point
-                               // it should use to create keys with) and because a node can't send a
-                               // commitment_signed without changes, checking if the feerate is equal to the
-                               // pending feerate update is sufficient to detect require_commitment.
-                               if feerate == self.feerate_per_kw {
+               if let Some((feerate, update_state)) = self.pending_update_fee {
+                       match update_state {
+                               FeeUpdateState::Outbound => {
+                                       debug_assert!(self.is_outbound());
+                                       log_trace!(logger, " ...promoting outbound fee update {} to Committed", feerate);
+                                       self.feerate_per_kw = feerate;
+                                       self.pending_update_fee = None;
+                               },
+                               FeeUpdateState::RemoteAnnounced => { debug_assert!(!self.is_outbound()); },
+                               FeeUpdateState::AwaitingRemoteRevokeToAnnounce => {
+                                       debug_assert!(!self.is_outbound());
+                                       log_trace!(logger, " ...promoting inbound AwaitingRemoteRevokeToAnnounce fee update {} to Committed", feerate);
                                        require_commitment = true;
+                                       self.feerate_per_kw = feerate;
                                        self.pending_update_fee = None;
-                               }
+                               },
                        }
                }
 
@@ -2686,7 +2905,7 @@ impl<Signer: Sign> Channel<Signer> {
                        self.monitor_pending_forwards.append(&mut to_forward_infos);
                        self.monitor_pending_failures.append(&mut revoked_htlcs);
                        log_debug!(logger, "Received a valid revoke_and_ack for channel {} but awaiting a monitor update resolution to reply.", log_bytes!(self.channel_id()));
-                       return Ok((None, Vec::new(), Vec::new(), None, monitor_update, Vec::new()))
+                       return Ok((None, Vec::new(), Vec::new(), monitor_update, Vec::new()))
                }
 
                match self.free_holding_cell_htlcs(logger)? {
@@ -2705,7 +2924,7 @@ impl<Signer: Sign> Channel<Signer> {
                                self.latest_monitor_update_id = monitor_update.update_id;
                                monitor_update.updates.append(&mut additional_update.updates);
 
-                               Ok((Some(commitment_update), to_forward_infos, revoked_htlcs, None, monitor_update, htlcs_to_fail))
+                               Ok((Some(commitment_update), to_forward_infos, revoked_htlcs, monitor_update, htlcs_to_fail))
                        },
                        (None, htlcs_to_fail) => {
                                if require_commitment {
@@ -2725,14 +2944,13 @@ impl<Signer: Sign> Channel<Signer> {
                                                update_fail_malformed_htlcs,
                                                update_fee: None,
                                                commitment_signed
-                                       }), to_forward_infos, revoked_htlcs, None, monitor_update, htlcs_to_fail))
+                                       }), to_forward_infos, revoked_htlcs, monitor_update, htlcs_to_fail))
                                } else {
                                        log_debug!(logger, "Received a valid revoke_and_ack for channel {} with no reply necessary.", log_bytes!(self.channel_id()));
-                                       Ok((None, to_forward_infos, revoked_htlcs, self.maybe_propose_first_closing_signed(fee_estimator), monitor_update, htlcs_to_fail))
+                                       Ok((None, to_forward_infos, revoked_htlcs, monitor_update, htlcs_to_fail))
                                }
                        }
                }
-
        }
 
        /// Adds a pending update to this channel. See the doc for send_htlc for
@@ -2749,13 +2967,13 @@ impl<Signer: Sign> Channel<Signer> {
                        panic!("Cannot update fee while peer is disconnected/we're awaiting a monitor update (ChannelManager should have caught this)");
                }
 
-               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
+               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::MonitorUpdateFailed as u32)) != 0 {
                        self.holding_cell_update_fee = Some(feerate_per_kw);
                        return None;
                }
 
                debug_assert!(self.pending_update_fee.is_none());
-               self.pending_update_fee = Some(feerate_per_kw);
+               self.pending_update_fee = Some((feerate_per_kw, FeeUpdateState::Outbound));
 
                Some(msgs::UpdateFee {
                        channel_id: self.channel_id,
@@ -2787,6 +3005,8 @@ impl<Signer: Sign> Channel<Signer> {
                // Upon reconnect we have to start the closing_signed dance over, but shutdown messages
                // will be retransmitted.
                self.last_sent_closing_fee = None;
+               self.pending_counterparty_closing_signed = None;
+               self.closing_fee_limits = None;
 
                let mut inbound_drop_count = 0;
                self.pending_inbound_htlcs.retain(|htlc| {
@@ -2816,6 +3036,13 @@ impl<Signer: Sign> Channel<Signer> {
                });
                self.next_counterparty_htlc_id -= inbound_drop_count;
 
+               if let Some((_, update_state)) = self.pending_update_fee {
+                       if update_state == FeeUpdateState::RemoteAnnounced {
+                               debug_assert!(!self.is_outbound());
+                               self.pending_update_fee = None;
+                       }
+               }
+
                for htlc in self.pending_outbound_htlcs.iter_mut() {
                        if let OutboundHTLCState::RemoteRemoved(_) = htlc.state {
                                // They sent us an update to remove this but haven't yet sent the corresponding
@@ -2910,8 +3137,27 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Close("Peer sent update_fee when we needed a channel_reestablish".to_owned()));
                }
                Channel::<Signer>::check_remote_fee(fee_estimator, msg.feerate_per_kw)?;
-               self.pending_update_fee = Some(msg.feerate_per_kw);
+               let feerate_over_dust_buffer = msg.feerate_per_kw > self.get_dust_buffer_feerate();
+
+               self.pending_update_fee = Some((msg.feerate_per_kw, FeeUpdateState::RemoteAnnounced));
                self.update_time_counter += 1;
+               // If the feerate has increased over the previous dust buffer (note that
+               // `get_dust_buffer_feerate` considers the `pending_update_fee` status), check that we
+               // won't be pushed over our dust exposure limit by the feerate increase.
+               if feerate_over_dust_buffer {
+                       let inbound_stats = self.get_inbound_pending_htlc_stats();
+                       let outbound_stats = self.get_outbound_pending_htlc_stats();
+                       let holder_tx_dust_exposure = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat;
+                       let counterparty_tx_dust_exposure = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat;
+                       if holder_tx_dust_exposure > self.get_max_dust_htlc_exposure_msat() {
+                               return Err(ChannelError::Close(format!("Peer sent update_fee with a feerate ({}) which may over-expose us to dust-in-flight on our own transactions (totaling {} msat)",
+                                       msg.feerate_per_kw, holder_tx_dust_exposure)));
+                       }
+                       if counterparty_tx_dust_exposure > self.get_max_dust_htlc_exposure_msat() {
+                               return Err(ChannelError::Close(format!("Peer sent update_fee with a feerate ({}) which may over-expose us to dust-in-flight on our counterparty's transactions (totaling {} msat)",
+                                       msg.feerate_per_kw, counterparty_tx_dust_exposure)));
+                       }
+               }
                Ok(())
        }
 
@@ -2973,11 +3219,18 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
 
-               log_trace!(logger, "Regenerated latest commitment update in channel {} with {} update_adds, {} update_fulfills, {} update_fails, and {} update_fail_malformeds",
-                               log_bytes!(self.channel_id()), update_add_htlcs.len(), update_fulfill_htlcs.len(), update_fail_htlcs.len(), update_fail_malformed_htlcs.len());
+               let update_fee = if self.is_outbound() && self.pending_update_fee.is_some() {
+                       Some(msgs::UpdateFee {
+                               channel_id: self.channel_id(),
+                               feerate_per_kw: self.pending_update_fee.unwrap().0,
+                       })
+               } else { None };
+
+               log_trace!(logger, "Regenerated latest commitment update in channel {} with{} {} update_adds, {} update_fulfills, {} update_fails, and {} update_fail_malformeds",
+                               log_bytes!(self.channel_id()), if update_fee.is_some() { " update_fee," } else { "" },
+                               update_add_htlcs.len(), update_fulfill_htlcs.len(), update_fail_htlcs.len(), update_fail_malformed_htlcs.len());
                msgs::CommitmentUpdate {
-                       update_add_htlcs, update_fulfill_htlcs, update_fail_htlcs, update_fail_malformed_htlcs,
-                       update_fee: None,
+                       update_add_htlcs, update_fulfill_htlcs, update_fail_htlcs, update_fail_malformed_htlcs, update_fee,
                        commitment_signed: self.send_commitment_no_state_update(logger).expect("It looks like we failed to re-generate a commitment_signed we had previously sent?").0,
                }
        }
@@ -3021,6 +3274,7 @@ impl<Signer: Sign> Channel<Signer> {
                self.channel_state &= !(ChannelState::PeerDisconnected as u32);
 
                let shutdown_msg = if self.channel_state & (ChannelState::LocalShutdownSent as u32) != 0 {
+                       assert!(self.shutdown_scriptpubkey.is_some());
                        Some(msgs::Shutdown {
                                channel_id: self.channel_id,
                                scriptpubkey: self.get_closing_scriptpubkey(),
@@ -3090,7 +3344,8 @@ impl<Signer: Sign> Channel<Signer> {
                                // now!
                                match self.free_holding_cell_htlcs(logger) {
                                        Err(ChannelError::Close(msg)) => return Err(ChannelError::Close(msg)),
-                                       Err(ChannelError::Ignore(_)) | Err(ChannelError::CloseDelayBroadcast(_)) => panic!("Got non-channel-failing result from free_holding_cell_htlcs"),
+                                       Err(ChannelError::Warn(_)) | Err(ChannelError::Ignore(_)) | Err(ChannelError::CloseDelayBroadcast(_)) =>
+                                               panic!("Got non-channel-failing result from free_holding_cell_htlcs"),
                                        Ok((Some((commitment_update, monitor_update)), htlcs_to_fail)) => {
                                                return Ok((resend_funding_locked, required_revoke, Some(commitment_update), Some(monitor_update), self.resend_order.clone(), htlcs_to_fail, shutdown_msg));
                                        },
@@ -3119,39 +3374,125 @@ impl<Signer: Sign> Channel<Signer> {
                }
        }
 
-       fn maybe_propose_first_closing_signed<F: Deref>(&mut self, fee_estimator: &F) -> Option<msgs::ClosingSigned>
+       /// Calculates and returns our minimum and maximum closing transaction fee amounts, in whole
+       /// satoshis. The amounts remain consistent unless a peer disconnects/reconnects or we restart,
+       /// at which point they will be recalculated.
+       fn calculate_closing_fee_limits<F: Deref>(&mut self, fee_estimator: &F) -> (u64, u64)
                where F::Target: FeeEstimator
        {
-               if !self.is_outbound() || !self.pending_inbound_htlcs.is_empty() || !self.pending_outbound_htlcs.is_empty() ||
-                               self.channel_state & (BOTH_SIDES_SHUTDOWN_MASK | ChannelState::AwaitingRemoteRevoke as u32) != BOTH_SIDES_SHUTDOWN_MASK ||
-                               self.last_sent_closing_fee.is_some() || self.pending_update_fee.is_some() {
-                       return None;
-               }
+               if let Some((min, max)) = self.closing_fee_limits { return (min, max); }
 
+               // Propose a range from our current Background feerate to our Normal feerate plus our
+               // force_close_avoidance_max_fee_satoshis.
+               // If we fail to come to consensus, we'll have to force-close.
                let mut proposed_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background);
-               if self.feerate_per_kw > proposed_feerate {
-                       proposed_feerate = self.feerate_per_kw;
-               }
+               let normal_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Normal);
+               let mut proposed_max_feerate = if self.is_outbound() { normal_feerate } else { u32::max_value() };
+
+               // The spec requires that (when the channel does not have anchors) we only send absolute
+               // channel fees no greater than the absolute channel fee on the current commitment
+               // transaction. It's unclear *which* commitment transaction this refers to, and there isn't
+               // very good reason to apply such a limit in any case. We don't bother doing so, risking
+               // some force-closure by old nodes, but we wanted to close the channel anyway.
+
+               if let Some(target_feerate) = self.target_closing_feerate_sats_per_kw {
+                       let min_feerate = if self.is_outbound() { target_feerate } else { cmp::min(self.feerate_per_kw, target_feerate) };
+                       proposed_feerate = cmp::max(proposed_feerate, min_feerate);
+                       proposed_max_feerate = cmp::max(proposed_max_feerate, min_feerate);
+               }
+
+               // Note that technically we could end up with a lower minimum fee if one sides' balance is
+               // below our dust limit, causing the output to disappear. We don't bother handling this
+               // case, however, as this should only happen if a channel is closed before any (material)
+               // payments have been made on it. This may cause slight fee overpayment and/or failure to
+               // come to consensus with our counterparty on appropriate fees, however it should be a
+               // relatively rare case. We can revisit this later, though note that in order to determine
+               // if the funders' output is dust we have to know the absolute fee we're going to use.
                let tx_weight = self.get_closing_transaction_weight(Some(&self.get_closing_scriptpubkey()), Some(self.counterparty_shutdown_scriptpubkey.as_ref().unwrap()));
                let proposed_total_fee_satoshis = proposed_feerate as u64 * tx_weight / 1000;
+               let proposed_max_total_fee_satoshis = if self.is_outbound() {
+                               // We always add force_close_avoidance_max_fee_satoshis to our normal
+                               // feerate-calculated fee, but allow the max to be overridden if we're using a
+                               // target feerate-calculated fee.
+                               cmp::max(normal_feerate as u64 * tx_weight / 1000 + self.config.force_close_avoidance_max_fee_satoshis,
+                                       proposed_max_feerate as u64 * tx_weight / 1000)
+                       } else {
+                               u64::max_value()
+                       };
+
+               self.closing_fee_limits = Some((proposed_total_fee_satoshis, proposed_max_total_fee_satoshis));
+               self.closing_fee_limits.clone().unwrap()
+       }
+
+       /// Returns true if we're ready to commence the closing_signed negotiation phase. This is true
+       /// after both sides have exchanged a `shutdown` message and all HTLCs have been drained. At
+       /// this point if we're the funder we should send the initial closing_signed, and in any case
+       /// shutdown should complete within a reasonable timeframe.
+       fn closing_negotiation_ready(&self) -> bool {
+               self.pending_inbound_htlcs.is_empty() && self.pending_outbound_htlcs.is_empty() &&
+                       self.channel_state &
+                               (BOTH_SIDES_SHUTDOWN_MASK | ChannelState::AwaitingRemoteRevoke as u32 |
+                                ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateFailed as u32)
+                               == BOTH_SIDES_SHUTDOWN_MASK &&
+                       self.pending_update_fee.is_none()
+       }
+
+       /// Checks if the closing_signed negotiation is making appropriate progress, possibly returning
+       /// an Err if no progress is being made and the channel should be force-closed instead.
+       /// Should be called on a one-minute timer.
+       pub fn timer_check_closing_negotiation_progress(&mut self) -> Result<(), ChannelError> {
+               if self.closing_negotiation_ready() {
+                       if self.closing_signed_in_flight {
+                               return Err(ChannelError::Close("closing_signed negotiation failed to finish within two timer ticks".to_owned()));
+                       } else {
+                               self.closing_signed_in_flight = true;
+                       }
+               }
+               Ok(())
+       }
+
+       pub fn maybe_propose_closing_signed<F: Deref, L: Deref>(&mut self, fee_estimator: &F, logger: &L)
+               -> Result<(Option<msgs::ClosingSigned>, Option<Transaction>), ChannelError>
+               where F::Target: FeeEstimator, L::Target: Logger
+       {
+               if self.last_sent_closing_fee.is_some() || !self.closing_negotiation_ready() {
+                       return Ok((None, None));
+               }
+
+               if !self.is_outbound() {
+                       if let Some(msg) = &self.pending_counterparty_closing_signed.take() {
+                               return self.closing_signed(fee_estimator, &msg);
+                       }
+                       return Ok((None, None));
+               }
+
+               let (our_min_fee, our_max_fee) = self.calculate_closing_fee_limits(fee_estimator);
+
+               assert!(self.shutdown_scriptpubkey.is_some());
+               let (closing_tx, total_fee_satoshis) = self.build_closing_transaction(our_min_fee, false);
+               log_trace!(logger, "Proposing initial closing_signed for our counterparty with a fee range of {}-{} sat (with initial proposal {} sats)",
+                       our_min_fee, our_max_fee, total_fee_satoshis);
 
-               let (closing_tx, total_fee_satoshis) = self.build_closing_transaction(proposed_total_fee_satoshis, false);
                let sig = self.holder_signer
                        .sign_closing_transaction(&closing_tx, &self.secp_ctx)
-                       .ok();
-               assert!(closing_tx.get_weight() as u64 <= tx_weight);
-               if sig.is_none() { return None; }
+                       .map_err(|()| ChannelError::Close("Failed to get signature for closing transaction.".to_owned()))?;
 
-               self.last_sent_closing_fee = Some((proposed_feerate, total_fee_satoshis, sig.clone().unwrap()));
-               Some(msgs::ClosingSigned {
+               self.last_sent_closing_fee = Some((total_fee_satoshis, sig.clone()));
+               Ok((Some(msgs::ClosingSigned {
                        channel_id: self.channel_id,
                        fee_satoshis: total_fee_satoshis,
-                       signature: sig.unwrap(),
-               })
+                       signature: sig,
+                       fee_range: Some(msgs::ClosingSignedFeeRange {
+                               min_fee_satoshis: our_min_fee,
+                               max_fee_satoshis: our_max_fee,
+                       }),
+               }), None))
        }
 
-       pub fn shutdown<F: Deref>(&mut self, fee_estimator: &F, their_features: &InitFeatures, msg: &msgs::Shutdown) -> Result<(Option<msgs::Shutdown>, Option<msgs::ClosingSigned>, Vec<(HTLCSource, PaymentHash)>), ChannelError>
-               where F::Target: FeeEstimator
+       pub fn shutdown<K: Deref>(
+               &mut self, keys_provider: &K, their_features: &InitFeatures, msg: &msgs::Shutdown
+       ) -> Result<(Option<msgs::Shutdown>, Option<ChannelMonitorUpdate>, Vec<(HTLCSource, PaymentHash)>), ChannelError>
+       where K::Target: KeysInterface<Signer = Signer>
        {
                if self.channel_state & (ChannelState::PeerDisconnected as u32) == ChannelState::PeerDisconnected as u32 {
                        return Err(ChannelError::Close("Peer sent shutdown when we needed a channel_reestablish".to_owned()));
@@ -3169,23 +3510,58 @@ impl<Signer: Sign> Channel<Signer> {
                }
                assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
 
-               if is_unsupported_shutdown_script(&their_features, &msg.scriptpubkey) {
-                       return Err(ChannelError::Close(format!("Got a nonstandard scriptpubkey ({}) from remote peer", msg.scriptpubkey.to_bytes().to_hex())));
-               }
+               let shutdown_scriptpubkey = match ShutdownScript::try_from((msg.scriptpubkey.clone(), their_features)) {
+                       Ok(script) => script.into_inner(),
+                       Err(_) => return Err(ChannelError::Close(format!("Got a nonstandard scriptpubkey ({}) from remote peer", msg.scriptpubkey.to_bytes().to_hex()))),
+               };
 
                if self.counterparty_shutdown_scriptpubkey.is_some() {
-                       if Some(&msg.scriptpubkey) != self.counterparty_shutdown_scriptpubkey.as_ref() {
-                               return Err(ChannelError::Close(format!("Got shutdown request with a scriptpubkey ({}) which did not match their previous scriptpubkey.", msg.scriptpubkey.to_bytes().to_hex())));
+                       if Some(&shutdown_scriptpubkey) != self.counterparty_shutdown_scriptpubkey.as_ref() {
+                               return Err(ChannelError::Close(format!("Got shutdown request with a scriptpubkey ({}) which did not match their previous scriptpubkey.", shutdown_scriptpubkey.to_bytes().to_hex())));
                        }
                } else {
-                       self.counterparty_shutdown_scriptpubkey = Some(msg.scriptpubkey.clone());
+                       self.counterparty_shutdown_scriptpubkey = Some(shutdown_scriptpubkey);
                }
 
+               // If we have any LocalAnnounced updates we'll probably just get back an update_fail_htlc
+               // immediately after the commitment dance, but we can send a Shutdown because we won't send
+               // any further commitment updates after we set LocalShutdownSent.
+               let send_shutdown = (self.channel_state & ChannelState::LocalShutdownSent as u32) != ChannelState::LocalShutdownSent as u32;
+
+               let update_shutdown_script = match self.shutdown_scriptpubkey {
+                       Some(_) => false,
+                       None => {
+                               assert!(send_shutdown);
+                               let shutdown_scriptpubkey = keys_provider.get_shutdown_scriptpubkey();
+                               if !shutdown_scriptpubkey.is_compatible(their_features) {
+                                       return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer: {}", shutdown_scriptpubkey)));
+                               }
+                               self.shutdown_scriptpubkey = Some(shutdown_scriptpubkey);
+                               true
+                       },
+               };
+
                // From here on out, we may not fail!
 
                self.channel_state |= ChannelState::RemoteShutdownSent as u32;
                self.update_time_counter += 1;
 
+               let monitor_update = if update_shutdown_script {
+                       self.latest_monitor_update_id += 1;
+                       Some(ChannelMonitorUpdate {
+                               update_id: self.latest_monitor_update_id,
+                               updates: vec![ChannelMonitorUpdateStep::ShutdownScript {
+                                       scriptpubkey: self.get_closing_scriptpubkey(),
+                               }],
+                       })
+               } else { None };
+               let shutdown = if send_shutdown {
+                       Some(msgs::Shutdown {
+                               channel_id: self.channel_id,
+                               scriptpubkey: self.get_closing_scriptpubkey(),
+                       })
+               } else { None };
+
                // We can't send our shutdown until we've committed all of our pending HTLCs, but the
                // remote side is unlikely to accept any new HTLCs, so we go ahead and "free" any holding
                // cell HTLCs and return them to fail the payment.
@@ -3200,23 +3576,11 @@ impl<Signer: Sign> Channel<Signer> {
                                _ => true
                        }
                });
-               // If we have any LocalAnnounced updates we'll probably just get back a update_fail_htlc
-               // immediately after the commitment dance, but we can send a Shutdown cause we won't send
-               // any further commitment updates after we set LocalShutdownSent.
-
-               let shutdown = if (self.channel_state & ChannelState::LocalShutdownSent as u32) == ChannelState::LocalShutdownSent as u32 {
-                       None
-               } else {
-                       Some(msgs::Shutdown {
-                               channel_id: self.channel_id,
-                               scriptpubkey: self.get_closing_scriptpubkey(),
-                       })
-               };
 
                self.channel_state |= ChannelState::LocalShutdownSent as u32;
                self.update_time_counter += 1;
 
-               Ok((shutdown, self.maybe_propose_first_closing_signed(fee_estimator), dropped_outbound_htlcs))
+               Ok((shutdown, monitor_update, dropped_outbound_htlcs))
        }
 
        fn build_signed_closing_transaction(&self, tx: &mut Transaction, counterparty_sig: &Signature, sig: &Signature) {
@@ -3257,10 +3621,19 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Close("Remote tried to send us a closing tx with > 21 million BTC fee".to_owned()));
                }
 
+               if self.is_outbound() && self.last_sent_closing_fee.is_none() {
+                       return Err(ChannelError::Close("Remote tried to send a closing_signed when we were supposed to propose the first one".to_owned()));
+               }
+
+               if self.channel_state & ChannelState::MonitorUpdateFailed as u32 != 0 {
+                       self.pending_counterparty_closing_signed = Some(msg.clone());
+                       return Ok((None, None));
+               }
+
                let funding_redeemscript = self.get_funding_redeemscript();
                let (mut closing_tx, used_total_fee) = self.build_closing_transaction(msg.fee_satoshis, false);
                if used_total_fee != msg.fee_satoshis {
-                       return Err(ChannelError::Close(format!("Remote sent us a closing_signed with a fee greater than the value they can claim. Fee in message: {}", msg.fee_satoshis)));
+                       return Err(ChannelError::Close(format!("Remote sent us a closing_signed with a fee other than the value they can claim. Fee in message: {}. Actual closing tx fee: {}", msg.fee_satoshis, used_total_fee)));
                }
                let mut sighash = hash_to_message!(&bip143::SigHashCache::new(&closing_tx).signature_hash(0, &funding_redeemscript, self.channel_value_satoshis, SigHashType::All)[..]);
 
@@ -3275,75 +3648,104 @@ impl<Signer: Sign> Channel<Signer> {
                        },
                };
 
-               let closing_tx_max_weight = self.get_closing_transaction_weight(
-                       if let Some(oup) = closing_tx.output.get(0) { Some(&oup.script_pubkey) } else { None },
-                       if let Some(oup) = closing_tx.output.get(1) { Some(&oup.script_pubkey) } else { None });
-               if let Some((_, last_fee, sig)) = self.last_sent_closing_fee {
+               assert!(self.shutdown_scriptpubkey.is_some());
+               if let Some((last_fee, sig)) = self.last_sent_closing_fee {
                        if last_fee == msg.fee_satoshis {
                                self.build_signed_closing_transaction(&mut closing_tx, &msg.signature, &sig);
-                               assert!(closing_tx.get_weight() as u64 <= closing_tx_max_weight);
-                               debug_assert!(closing_tx.get_weight() as u64 >= closing_tx_max_weight - 2);
                                self.channel_state = ChannelState::ShutdownComplete as u32;
                                self.update_time_counter += 1;
                                return Ok((None, Some(closing_tx)));
                        }
                }
 
-               macro_rules! propose_new_feerate {
-                       ($new_feerate: expr) => {
-                               let tx_weight = self.get_closing_transaction_weight(Some(&self.get_closing_scriptpubkey()), Some(self.counterparty_shutdown_scriptpubkey.as_ref().unwrap()));
-                               let (closing_tx, used_total_fee) = self.build_closing_transaction($new_feerate as u64 * tx_weight / 1000, false);
+               let (our_min_fee, our_max_fee) = self.calculate_closing_fee_limits(fee_estimator);
+
+               macro_rules! propose_fee {
+                       ($new_fee: expr) => {
+                               let (mut tx, used_fee) = if $new_fee == msg.fee_satoshis {
+                                       (closing_tx, $new_fee)
+                               } else {
+                                       self.build_closing_transaction($new_fee, false)
+                               };
+
                                let sig = self.holder_signer
-                                       .sign_closing_transaction(&closing_tx, &self.secp_ctx)
+                                       .sign_closing_transaction(&tx, &self.secp_ctx)
                                        .map_err(|_| ChannelError::Close("External signer refused to sign closing transaction".to_owned()))?;
-                               assert!(closing_tx.get_weight() as u64 <= tx_weight);
-                               self.last_sent_closing_fee = Some(($new_feerate, used_total_fee, sig.clone()));
+
+                               let signed_tx = if $new_fee == msg.fee_satoshis {
+                                       self.channel_state = ChannelState::ShutdownComplete as u32;
+                                       self.update_time_counter += 1;
+                                       self.build_signed_closing_transaction(&mut tx, &msg.signature, &sig);
+                                       Some(tx)
+                               } else { None };
+
+                               self.last_sent_closing_fee = Some((used_fee, sig.clone()));
                                return Ok((Some(msgs::ClosingSigned {
                                        channel_id: self.channel_id,
-                                       fee_satoshis: used_total_fee,
+                                       fee_satoshis: used_fee,
                                        signature: sig,
-                               }), None))
+                                       fee_range: Some(msgs::ClosingSignedFeeRange {
+                                               min_fee_satoshis: our_min_fee,
+                                               max_fee_satoshis: our_max_fee,
+                                       }),
+                               }), signed_tx))
                        }
                }
 
-               let mut min_feerate = 253;
-               if self.is_outbound() {
-                       let max_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Normal);
-                       if (msg.fee_satoshis as u64) > max_feerate as u64 * closing_tx_max_weight / 1000 {
-                               if let Some((last_feerate, _, _)) = self.last_sent_closing_fee {
-                                       if max_feerate <= last_feerate {
-                                               return Err(ChannelError::Close(format!("Unable to come to consensus about closing feerate, remote wanted something higher ({}) than our Normal feerate ({})", last_feerate, max_feerate)));
-                                       }
+               if let Some(msgs::ClosingSignedFeeRange { min_fee_satoshis, max_fee_satoshis }) = msg.fee_range {
+                       if msg.fee_satoshis < min_fee_satoshis || msg.fee_satoshis > max_fee_satoshis {
+                               return Err(ChannelError::Close(format!("Peer sent a bogus closing_signed - suggested fee of {} sat was not in their desired range of {} sat - {} sat", msg.fee_satoshis, min_fee_satoshis, max_fee_satoshis)));
+                       }
+                       if max_fee_satoshis < our_min_fee {
+                               return Err(ChannelError::Warn(format!("Unable to come to consensus about closing feerate, remote's max fee ({} sat) was smaller than our min fee ({} sat)", max_fee_satoshis, our_min_fee)));
+                       }
+                       if min_fee_satoshis > our_max_fee {
+                               return Err(ChannelError::Warn(format!("Unable to come to consensus about closing feerate, remote's min fee ({} sat) was greater than our max fee ({} sat)", min_fee_satoshis, our_max_fee)));
+                       }
+
+                       if !self.is_outbound() {
+                               // They have to pay, so pick the highest fee in the overlapping range.
+                               debug_assert_eq!(our_max_fee, u64::max_value()); // We should never set an upper bound
+                               propose_fee!(cmp::min(max_fee_satoshis, our_max_fee));
+                       } else {
+                               if msg.fee_satoshis < our_min_fee || msg.fee_satoshis > our_max_fee {
+                                       return Err(ChannelError::Close(format!("Peer sent a bogus closing_signed - suggested fee of {} sat was not in our desired range of {} sat - {} sat after we informed them of our range.",
+                                               msg.fee_satoshis, our_min_fee, our_max_fee)));
                                }
-                               propose_new_feerate!(max_feerate);
+                               // The proposed fee is in our acceptable range, accept it and broadcast!
+                               propose_fee!(msg.fee_satoshis);
                        }
                } else {
-                       min_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background);
-               }
-               if (msg.fee_satoshis as u64) < min_feerate as u64 * closing_tx_max_weight / 1000 {
-                       if let Some((last_feerate, _, _)) = self.last_sent_closing_fee {
-                               if min_feerate >= last_feerate {
-                                       return Err(ChannelError::Close(format!("Unable to come to consensus about closing feerate, remote wanted something lower ({}) than our Background feerate ({}).", last_feerate, min_feerate)));
+                       // Old fee style negotiation. We don't bother to enforce whether they are complying
+                       // with the "making progress" requirements, we just comply and hope for the best.
+                       if let Some((last_fee, _)) = self.last_sent_closing_fee {
+                               if msg.fee_satoshis > last_fee {
+                                       if msg.fee_satoshis < our_max_fee {
+                                               propose_fee!(msg.fee_satoshis);
+                                       } else if last_fee < our_max_fee {
+                                               propose_fee!(our_max_fee);
+                                       } else {
+                                               return Err(ChannelError::Close(format!("Unable to come to consensus about closing feerate, remote wants something ({} sat) higher than our max fee ({} sat)", msg.fee_satoshis, our_max_fee)));
+                                       }
+                               } else {
+                                       if msg.fee_satoshis > our_min_fee {
+                                               propose_fee!(msg.fee_satoshis);
+                                       } else if last_fee > our_min_fee {
+                                               propose_fee!(our_min_fee);
+                                       } else {
+                                               return Err(ChannelError::Close(format!("Unable to come to consensus about closing feerate, remote wants something ({} sat) lower than our min fee ({} sat)", msg.fee_satoshis, our_min_fee)));
+                                       }
+                               }
+                       } else {
+                               if msg.fee_satoshis < our_min_fee {
+                                       propose_fee!(our_min_fee);
+                               } else if msg.fee_satoshis > our_max_fee {
+                                       propose_fee!(our_max_fee);
+                               } else {
+                                       propose_fee!(msg.fee_satoshis);
                                }
                        }
-                       propose_new_feerate!(min_feerate);
                }
-
-               let sig = self.holder_signer
-                       .sign_closing_transaction(&closing_tx, &self.secp_ctx)
-                       .map_err(|_| ChannelError::Close("External signer refused to sign closing transaction".to_owned()))?;
-               self.build_signed_closing_transaction(&mut closing_tx, &msg.signature, &sig);
-               assert!(closing_tx.get_weight() as u64 <= closing_tx_max_weight);
-               debug_assert!(closing_tx.get_weight() as u64 >= closing_tx_max_weight - 2);
-
-               self.channel_state = ChannelState::ShutdownComplete as u32;
-               self.update_time_counter += 1;
-
-               Ok((Some(msgs::ClosingSigned {
-                       channel_id: self.channel_id,
-                       fee_satoshis: msg.fee_satoshis,
-                       signature: sig,
-               }), Some(closing_tx)))
        }
 
        // Public utilities:
@@ -3432,11 +3834,27 @@ impl<Signer: Sign> Channel<Signer> {
                cmp::max(self.config.cltv_expiry_delta, MIN_CLTV_EXPIRY_DELTA)
        }
 
-       #[cfg(test)]
+       pub fn get_max_dust_htlc_exposure_msat(&self) -> u64 {
+               self.config.max_dust_htlc_exposure_msat
+       }
+
        pub fn get_feerate(&self) -> u32 {
                self.feerate_per_kw
        }
 
+       pub fn get_dust_buffer_feerate(&self) -> u32 {
+               // When calculating our exposure to dust HTLCs, we assume that the channel feerate
+               // may, at any point, increase by at least 10 sat/vB (i.e 2530 sat/kWU) or 25%,
+               // whichever is higher. This ensures that we aren't suddenly exposed to significantly
+               // more dust balance if the feerate increases when we have several HTLCs pending
+               // which are near the dust limit.
+               let mut feerate_per_kw = self.feerate_per_kw;
+               if let Some((feerate, _)) = self.pending_update_fee {
+                       feerate_per_kw = cmp::max(feerate_per_kw, feerate);
+               }
+               cmp::max(2530, feerate_per_kw * 1250 / 1000)
+       }
+
        pub fn get_cur_holder_commitment_transaction_number(&self) -> u64 {
                self.cur_holder_commitment_transaction_number + 1
        }
@@ -3532,6 +3950,16 @@ impl<Signer: Sign> Channel<Signer> {
                self.channel_state >= ChannelState::FundingSent as u32
        }
 
+       /// Returns true if our peer has either initiated or agreed to shut down the channel.
+       pub fn received_shutdown(&self) -> bool {
+               (self.channel_state & ChannelState::RemoteShutdownSent as u32) != 0
+       }
+
+       /// Returns true if we either initiated or agreed to shut down the channel.
+       pub fn sent_shutdown(&self) -> bool {
+               (self.channel_state & ChannelState::LocalShutdownSent as u32) != 0
+       }
+
        /// Returns true if this channel is fully shut down. True here implies that no further actions
        /// may/will be taken on this channel, and thus this object should be freed. Any future changes
        /// will be handled appropriately by the chain monitor.
@@ -3789,7 +4217,10 @@ impl<Signer: Sign> Channel<Signer> {
                        htlc_basepoint: keys.htlc_basepoint,
                        first_per_commitment_point,
                        channel_flags: if self.config.announced_channel {1} else {0},
-                       shutdown_scriptpubkey: OptionalField::Present(if self.config.commit_upfront_shutdown_pubkey { self.get_closing_scriptpubkey() } else { Builder::new().into_script() })
+                       shutdown_scriptpubkey: OptionalField::Present(match &self.shutdown_scriptpubkey {
+                               Some(script) => script.clone().into_inner(),
+                               None => Builder::new().into_script(),
+                       }),
                }
        }
 
@@ -3822,14 +4253,17 @@ impl<Signer: Sign> Channel<Signer> {
                        delayed_payment_basepoint: keys.delayed_payment_basepoint,
                        htlc_basepoint: keys.htlc_basepoint,
                        first_per_commitment_point,
-                       shutdown_scriptpubkey: OptionalField::Present(if self.config.commit_upfront_shutdown_pubkey { self.get_closing_scriptpubkey() } else { Builder::new().into_script() })
+                       shutdown_scriptpubkey: OptionalField::Present(match &self.shutdown_scriptpubkey {
+                               Some(script) => script.clone().into_inner(),
+                               None => Builder::new().into_script(),
+                       }),
                }
        }
 
        /// If an Err is returned, it is a ChannelError::Close (for get_outbound_funding_created)
        fn get_outbound_funding_created_signature<L: Deref>(&mut self, logger: &L) -> Result<Signature, ChannelError> where L::Target: Logger {
                let counterparty_keys = self.build_remote_transaction_keys()?;
-               let counterparty_initial_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, self.feerate_per_kw, logger).0;
+               let counterparty_initial_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).0;
                Ok(self.holder_signer.sign_counterparty_commitment(&counterparty_initial_commitment_tx, &self.secp_ctx)
                                .map_err(|_| ChannelError::Close("Failed to get signatures for new commitment_signed".to_owned()))?.0)
        }
@@ -4075,19 +4509,20 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Ignore("Cannot send an HTLC while disconnected from channel counterparty".to_owned()));
                }
 
-               let (outbound_htlc_count, htlc_outbound_value_msat) = self.get_outbound_pending_htlc_stats();
-               if outbound_htlc_count + 1 > self.counterparty_max_accepted_htlcs as u32 {
+               let inbound_stats = self.get_inbound_pending_htlc_stats();
+               let outbound_stats = self.get_outbound_pending_htlc_stats();
+               if outbound_stats.pending_htlcs + 1 > self.counterparty_max_accepted_htlcs as u32 {
                        return Err(ChannelError::Ignore(format!("Cannot push more than their max accepted HTLCs ({})", self.counterparty_max_accepted_htlcs)));
                }
                // Check their_max_htlc_value_in_flight_msat
-               if htlc_outbound_value_msat + amount_msat > self.counterparty_max_htlc_value_in_flight_msat {
+               if outbound_stats.pending_htlcs_value_msat + amount_msat > self.counterparty_max_htlc_value_in_flight_msat {
                        return Err(ChannelError::Ignore(format!("Cannot send value that would put us over the max HTLC value in flight our peer will accept ({})", self.counterparty_max_htlc_value_in_flight_msat)));
                }
 
                if !self.is_outbound() {
                        // Check that we won't violate the remote channel reserve by adding this HTLC.
                        let counterparty_balance_msat = self.channel_value_satoshis * 1000 - self.value_to_self_msat;
-                       let holder_selected_chan_reserve_msat = Channel::<Signer>::get_holder_selected_channel_reserve_satoshis(self.channel_value_satoshis);
+                       let holder_selected_chan_reserve_msat = Channel::<Signer>::get_holder_selected_channel_reserve_satoshis(self.channel_value_satoshis) * 1000;
                        let htlc_candidate = HTLCCandidate::new(amount_msat, HTLCInitiator::LocalOffered);
                        let counterparty_commit_tx_fee_msat = self.next_remote_commit_tx_fee_msat(htlc_candidate, None);
                        if counterparty_balance_msat < holder_selected_chan_reserve_msat + counterparty_commit_tx_fee_msat {
@@ -4095,7 +4530,25 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
 
-               let pending_value_to_self_msat = self.value_to_self_msat - htlc_outbound_value_msat;
+               let exposure_dust_limit_success_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               if amount_msat / 1000 < exposure_dust_limit_success_sats {
+                       let on_counterparty_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat + amount_msat;
+                       if on_counterparty_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               return Err(ChannelError::Ignore(format!("Cannot send value that would put our exposure to dust HTLCs at {} over the limit {} on counterparty commitment tx",
+                                       on_counterparty_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat())));
+                       }
+               }
+
+               let exposure_dust_limit_timeout_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
+               if amount_msat / 1000 <  exposure_dust_limit_timeout_sats {
+                       let on_holder_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat + amount_msat;
+                       if on_holder_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               return Err(ChannelError::Ignore(format!("Cannot send value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
+                                       on_holder_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat())));
+                       }
+               }
+
+               let pending_value_to_self_msat = self.value_to_self_msat - outbound_stats.pending_htlcs_value_msat;
                if pending_value_to_self_msat < amount_msat {
                        return Err(ChannelError::Ignore(format!("Cannot send value that would overdraw remaining funds. Amount: {}, pending value to self {}", amount_msat, pending_value_to_self_msat)));
                }
@@ -4103,7 +4556,7 @@ impl<Signer: Sign> Channel<Signer> {
                // `2 *` and extra HTLC are for the fee spike buffer.
                let commit_tx_fee_msat = if self.is_outbound() {
                        let htlc_candidate = HTLCCandidate::new(amount_msat, HTLCInitiator::LocalOffered);
-                       2 * self.next_local_commit_tx_fee_msat(htlc_candidate, Some(()))
+                       FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE * self.next_local_commit_tx_fee_msat(htlc_candidate, Some(()))
                } else { 0 };
                if pending_value_to_self_msat - amount_msat < commit_tx_fee_msat {
                        return Err(ChannelError::Ignore(format!("Cannot send value that would not leave enough to pay for fees. Pending value to self: {}. local_commit_tx_fee {}", pending_value_to_self_msat, commit_tx_fee_msat)));
@@ -4167,7 +4620,7 @@ impl<Signer: Sign> Channel<Signer> {
                if (self.channel_state & (ChannelState::MonitorUpdateFailed as u32)) == (ChannelState::MonitorUpdateFailed as u32) {
                        panic!("Cannot create commitment tx while awaiting monitor update unfreeze, as send_htlc will have returned an Err so a send_commitment precondition has been violated");
                }
-               let mut have_updates = self.pending_update_fee.is_some();
+               let mut have_updates = self.is_outbound() && self.pending_update_fee.is_some();
                for htlc in self.pending_outbound_htlcs.iter() {
                        if let OutboundHTLCState::LocalAnnounced(_) = htlc.state {
                                have_updates = true;
@@ -4187,6 +4640,7 @@ impl<Signer: Sign> Channel<Signer> {
        }
        /// Only fails in case of bad keys
        fn send_commitment_no_status_check<L: Deref>(&mut self, logger: &L) -> Result<(msgs::CommitmentSigned, ChannelMonitorUpdate), ChannelError> where L::Target: Logger {
+               log_trace!(logger, "Updating HTLC state for a newly-sent commitment_signed...");
                // We can upgrade the status of some HTLCs that are waiting on a commitment, even if we
                // fail to generate this, we still are at least at a position where upgrading their status
                // is acceptable.
@@ -4195,6 +4649,7 @@ impl<Signer: Sign> Channel<Signer> {
                                Some(InboundHTLCState::AwaitingAnnouncedRemoteRevoke(forward_info.clone()))
                        } else { None };
                        if let Some(state) = new_state {
+                               log_trace!(logger, " ...promoting inbound AwaitingRemoteRevokeToAnnounce {} to AwaitingAnnouncedRemoteRevoke", log_bytes!(htlc.payment_hash.0));
                                htlc.state = state;
                        }
                }
@@ -4202,9 +4657,18 @@ impl<Signer: Sign> Channel<Signer> {
                        if let Some(fail_reason) = if let &mut OutboundHTLCState::AwaitingRemoteRevokeToRemove(ref mut fail_reason) = &mut htlc.state {
                                Some(fail_reason.take())
                        } else { None } {
+                               log_trace!(logger, " ...promoting outbound AwaitingRemoteRevokeToRemove {} to AwaitingRemovedRemoteRevoke", log_bytes!(htlc.payment_hash.0));
                                htlc.state = OutboundHTLCState::AwaitingRemovedRemoteRevoke(fail_reason);
                        }
                }
+               if let Some((feerate, update_state)) = self.pending_update_fee {
+                       if update_state == FeeUpdateState::AwaitingRemoteRevokeToAnnounce {
+                               debug_assert!(!self.is_outbound());
+                               log_trace!(logger, " ...promoting inbound AwaitingRemoteRevokeToAnnounce fee update {} to Committed", feerate);
+                               self.feerate_per_kw = feerate;
+                               self.pending_update_fee = None;
+                       }
+               }
                self.resend_order = RAACommitmentOrder::RevokeAndACKFirst;
 
                let (res, counterparty_commitment_txid, htlcs) = match self.send_commitment_no_state_update(logger) {
@@ -4234,15 +4698,9 @@ impl<Signer: Sign> Channel<Signer> {
        /// Only fails in case of bad keys. Used for channel_reestablish commitment_signed generation
        /// when we shouldn't change HTLC/channel state.
        fn send_commitment_no_state_update<L: Deref>(&self, logger: &L) -> Result<(msgs::CommitmentSigned, (Txid, Vec<(HTLCOutputInCommitment, Option<&HTLCSource>)>)), ChannelError> where L::Target: Logger {
-               let mut feerate_per_kw = self.feerate_per_kw;
-               if let Some(feerate) = self.pending_update_fee {
-                       if self.is_outbound() {
-                               feerate_per_kw = feerate;
-                       }
-               }
-
                let counterparty_keys = self.build_remote_transaction_keys()?;
-               let counterparty_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, true, feerate_per_kw, logger);
+               let counterparty_commitment_tx = self.build_commitment_transaction(self.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, true, logger);
+               let feerate_per_kw = counterparty_commitment_tx.1;
                let counterparty_commitment_txid = counterparty_commitment_tx.0.trust().txid();
                let (signature, htlc_signatures);
 
@@ -4257,7 +4715,7 @@ impl<Signer: Sign> Channel<Signer> {
                                                && info.next_holder_htlc_id == self.next_holder_htlc_id
                                                && info.next_counterparty_htlc_id == self.next_counterparty_htlc_id
                                                && info.feerate == self.feerate_per_kw {
-                                                       let actual_fee = self.commit_tx_fee_msat(counterparty_commitment_tx.1);
+                                                       let actual_fee = self.commit_tx_fee_msat(counterparty_commitment_tx.2);
                                                        assert_eq!(actual_fee, info.fee);
                                                }
                                }
@@ -4265,8 +4723,8 @@ impl<Signer: Sign> Channel<Signer> {
                }
 
                {
-                       let mut htlcs = Vec::with_capacity(counterparty_commitment_tx.2.len());
-                       for &(ref htlc, _) in counterparty_commitment_tx.2.iter() {
+                       let mut htlcs = Vec::with_capacity(counterparty_commitment_tx.3.len());
+                       for &(ref htlc, _) in counterparty_commitment_tx.3.iter() {
                                htlcs.push(htlc);
                        }
 
@@ -4293,7 +4751,7 @@ impl<Signer: Sign> Channel<Signer> {
                        channel_id: self.channel_id,
                        signature,
                        htlc_signatures,
-               }, (counterparty_commitment_txid, counterparty_commitment_tx.2)))
+               }, (counterparty_commitment_txid, counterparty_commitment_tx.3)))
        }
 
        /// Adds a pending outbound HTLC to this channel, and creates a signed commitment transaction
@@ -4330,7 +4788,9 @@ impl<Signer: Sign> Channel<Signer> {
 
        /// Begins the shutdown process, getting a message for the remote peer and returning all
        /// holding cell HTLCs for payment failure.
-       pub fn get_shutdown(&mut self) -> Result<(msgs::Shutdown, Vec<(HTLCSource, PaymentHash)>), APIError> {
+       pub fn get_shutdown<K: Deref>(&mut self, keys_provider: &K, their_features: &InitFeatures, target_feerate_sats_per_kw: Option<u32>)
+       -> Result<(msgs::Shutdown, Option<ChannelMonitorUpdate>, Vec<(HTLCSource, PaymentHash)>), APIError>
+       where K::Target: KeysInterface<Signer = Signer> {
                for htlc in self.pending_outbound_htlcs.iter() {
                        if let OutboundHTLCState::LocalAnnounced(_) = htlc.state {
                                return Err(APIError::APIMisuseError{err: "Cannot begin shutdown with pending HTLCs. Process pending events first".to_owned()});
@@ -4349,9 +4809,20 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(APIError::ChannelUnavailable{err: "Cannot begin shutdown while peer is disconnected or we're waiting on a monitor update, maybe force-close instead?".to_owned()});
                }
 
-               let closing_script = self.get_closing_scriptpubkey();
+               let update_shutdown_script = match self.shutdown_scriptpubkey {
+                       Some(_) => false,
+                       None => {
+                               let shutdown_scriptpubkey = keys_provider.get_shutdown_scriptpubkey();
+                               if !shutdown_scriptpubkey.is_compatible(their_features) {
+                                       return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
+                               }
+                               self.shutdown_scriptpubkey = Some(shutdown_scriptpubkey);
+                               true
+                       },
+               };
 
                // From here on out, we may not fail!
+               self.target_closing_feerate_sats_per_kw = target_feerate_sats_per_kw;
                if self.channel_state < ChannelState::FundingSent as u32 {
                        self.channel_state = ChannelState::ShutdownComplete as u32;
                } else {
@@ -4359,6 +4830,20 @@ impl<Signer: Sign> Channel<Signer> {
                }
                self.update_time_counter += 1;
 
+               let monitor_update = if update_shutdown_script {
+                       self.latest_monitor_update_id += 1;
+                       Some(ChannelMonitorUpdate {
+                               update_id: self.latest_monitor_update_id,
+                               updates: vec![ChannelMonitorUpdateStep::ShutdownScript {
+                                       scriptpubkey: self.get_closing_scriptpubkey(),
+                               }],
+                       })
+               } else { None };
+               let shutdown = msgs::Shutdown {
+                       channel_id: self.channel_id,
+                       scriptpubkey: self.get_closing_scriptpubkey(),
+               };
+
                // Go ahead and drop holding cell updates as we'd rather fail payments than wait to send
                // our shutdown until we've committed all of the pending changes.
                self.holding_cell_update_fee = None;
@@ -4373,10 +4858,7 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                });
 
-               Ok((msgs::Shutdown {
-                       channel_id: self.channel_id,
-                       scriptpubkey: closing_script,
-               }, dropped_outbound_htlcs))
+               Ok((shutdown, monitor_update, dropped_outbound_htlcs))
        }
 
        /// Gets the latest commitment transaction and any dependent transactions for relay (forcing
@@ -4425,24 +4907,6 @@ impl<Signer: Sign> Channel<Signer> {
        }
 }
 
-fn is_unsupported_shutdown_script(their_features: &InitFeatures, script: &Script) -> bool {
-       // We restrain shutdown scripts to standards forms to avoid transactions not propagating on the p2p tx-relay network
-
-       // BOLT 2 says we must only send a scriptpubkey of certain standard forms,
-       // which for a a BIP-141-compliant witness program is at max 42 bytes in length.
-       // So don't let the remote peer feed us some super fee-heavy script.
-       let is_script_too_long = script.len() > 42;
-       if is_script_too_long {
-               return true;
-       }
-
-       if their_features.supports_shutdown_anysegwit() && script.is_witness_program() && script.as_bytes()[0] != OP_PUSHBYTES_0.into_u8() {
-               return false;
-       }
-
-       return !script.is_p2pkh() && !script.is_p2sh() && !script.is_v0_p2wpkh() && !script.is_v0_p2wsh()
-}
-
 const SERIALIZATION_VERSION: u8 = 2;
 const MIN_SERIALIZATION_VERSION: u8 = 1;
 
@@ -4453,7 +4917,7 @@ impl_writeable_tlv_based_enum!(InboundHTLCRemovalReason,;
 );
 
 impl Writeable for ChannelUpdateStatus {
-       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                // We only care about writing out the current state as it was announced, ie only either
                // Enabled or Disabled. In the case of DisabledStaged, we most recently announced the
                // channel as enabled, so we write 0. For EnabledStaged, we similarly write a 1.
@@ -4468,7 +4932,7 @@ impl Writeable for ChannelUpdateStatus {
 }
 
 impl Readable for ChannelUpdateStatus {
-       fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+       fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                Ok(match <u8 as Readable>::read(reader)? {
                        0 => ChannelUpdateStatus::Enabled,
                        1 => ChannelUpdateStatus::Disabled,
@@ -4478,7 +4942,7 @@ impl Readable for ChannelUpdateStatus {
 }
 
 impl<Signer: Sign> Writeable for Channel<Signer> {
-       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                // Note that we write out as if remove_uncommitted_htlcs_and_mark_paused had just been
                // called.
 
@@ -4506,7 +4970,12 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
                (key_data.0.len() as u32).write(writer)?;
                writer.write_all(&key_data.0[..])?;
 
-               self.shutdown_pubkey.write(writer)?;
+               // Write out the old serialization for shutdown_pubkey for backwards compatibility, if
+               // deserialized from that format.
+               match self.shutdown_scriptpubkey.as_ref().and_then(|script| script.as_legacy_pubkey()) {
+                       Some(shutdown_pubkey) => shutdown_pubkey.write(writer)?,
+                       None => [0u8; PUBLIC_KEY_SIZE].write(writer)?,
+               }
                self.destination_script.write(writer)?;
 
                self.cur_holder_commitment_transaction_number.write(writer)?;
@@ -4625,7 +5094,14 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
                        fail_reason.write(writer)?;
                }
 
-               self.pending_update_fee.write(writer)?;
+               if self.is_outbound() {
+                       self.pending_update_fee.map(|(a, _)| a).write(writer)?;
+               } else if let Some((feerate, FeeUpdateState::AwaitingRemoteRevokeToAnnounce)) = self.pending_update_fee {
+                       // As for inbound HTLCs, if the update was only announced and never committed, drop it.
+                       Some(feerate).write(writer)?;
+               } else {
+                       None::<u32>.write(writer)?;
+               }
                self.holding_cell_update_fee.write(writer)?;
 
                self.next_holder_htlc_id.write(writer)?;
@@ -4633,15 +5109,11 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
                self.update_time_counter.write(writer)?;
                self.feerate_per_kw.write(writer)?;
 
-               match self.last_sent_closing_fee {
-                       Some((feerate, fee, sig)) => {
-                               1u8.write(writer)?;
-                               feerate.write(writer)?;
-                               fee.write(writer)?;
-                               sig.write(writer)?;
-                       },
-                       None => 0u8.write(writer)?,
-               }
+               // Versions prior to 0.0.100 expected to read the fields of `last_sent_closing_fee` here,
+               // however we are supposed to restart shutdown fee negotiation on reconnect (and wipe
+               // `last_send_closing_fee` in `remove_uncommitted_htlcs_and_mark_paused`) so we should never
+               // consider the stale state on reload.
+               0u8.write(writer)?;
 
                self.funding_tx_confirmed_in.write(writer)?;
                self.funding_tx_confirmation_height.write(writer)?;
@@ -4684,6 +5156,13 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
 
                self.channel_update_status.write(writer)?;
 
+               #[cfg(any(test, feature = "fuzztarget"))]
+               (self.historical_inbound_htlc_fulfills.len() as u64).write(writer)?;
+               #[cfg(any(test, feature = "fuzztarget"))]
+               for htlc in self.historical_inbound_htlc_fulfills.iter() {
+                       htlc.write(writer)?;
+               }
+
                write_tlv_fields!(writer, {
                        (0, self.announcement_sigs, option),
                        // minimum_depth and counterparty_selected_channel_reserve_satoshis used to have a
@@ -4695,6 +5174,8 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
                        (1, self.minimum_depth, option),
                        (3, self.counterparty_selected_channel_reserve_satoshis, option),
                        (5, self.config, required),
+                       (7, self.shutdown_scriptpubkey, option),
+                       (9, self.target_closing_feerate_sats_per_kw, option),
                });
 
                Ok(())
@@ -4704,7 +5185,7 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
 const MAX_ALLOC_SIZE: usize = 64*1024;
 impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                where K::Target: KeysInterface<Signer = Signer> {
-       fn read<R : ::std::io::Read>(reader: &mut R, keys_source: &'a K) -> Result<Self, DecodeError> {
+       fn read<R : io::Read>(reader: &mut R, keys_source: &'a K) -> Result<Self, DecodeError> {
                let ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);
 
                let user_id = Readable::read(reader)?;
@@ -4738,7 +5219,11 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                }
                let holder_signer = keys_source.read_chan_signer(&keys_data)?;
 
-               let shutdown_pubkey = Readable::read(reader)?;
+               // Read the old serialization for shutdown_pubkey, preferring the TLV field later if set.
+               let mut shutdown_scriptpubkey = match <PublicKey as Readable>::read(reader) {
+                       Ok(pubkey) => Some(ShutdownScript::new_p2wpkh_from_pubkey(pubkey)),
+                       Err(_) => None,
+               };
                let destination_script = Readable::read(reader)?;
 
                let cur_holder_commitment_transaction_number = Readable::read(reader)?;
@@ -4828,7 +5313,8 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                        monitor_pending_failures.push((Readable::read(reader)?, Readable::read(reader)?, Readable::read(reader)?));
                }
 
-               let pending_update_fee = Readable::read(reader)?;
+               let pending_update_fee_value: Option<u32> = Readable::read(reader)?;
+
                let holding_cell_update_fee = Readable::read(reader)?;
 
                let next_holder_htlc_id = Readable::read(reader)?;
@@ -4836,11 +5322,19 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                let update_time_counter = Readable::read(reader)?;
                let feerate_per_kw = Readable::read(reader)?;
 
-               let last_sent_closing_fee = match <u8 as Readable>::read(reader)? {
-                       0 => None,
-                       1 => Some((Readable::read(reader)?, Readable::read(reader)?, Readable::read(reader)?)),
+               // Versions prior to 0.0.100 expected to read the fields of `last_sent_closing_fee` here,
+               // however we are supposed to restart shutdown fee negotiation on reconnect (and wipe
+               // `last_send_closing_fee` in `remove_uncommitted_htlcs_and_mark_paused`) so we should never
+               // consider the stale state on reload.
+               match <u8 as Readable>::read(reader)? {
+                       0 => {},
+                       1 => {
+                               let _: u32 = Readable::read(reader)?;
+                               let _: u64 = Readable::read(reader)?;
+                               let _: Signature = Readable::read(reader)?;
+                       },
                        _ => return Err(DecodeError::InvalidValue),
-               };
+               }
 
                let funding_tx_confirmed_in = Readable::read(reader)?;
                let funding_tx_confirmation_height = Readable::read(reader)?;
@@ -4880,7 +5374,7 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                        _ => return Err(DecodeError::InvalidValue),
                };
 
-               let channel_parameters = Readable::read(reader)?;
+               let channel_parameters: ChannelTransactionParameters = Readable::read(reader)?;
                let funding_transaction = Readable::read(reader)?;
 
                let counterparty_cur_commitment_point = Readable::read(reader)?;
@@ -4893,12 +5387,35 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
 
                let channel_update_status = Readable::read(reader)?;
 
+               #[cfg(any(test, feature = "fuzztarget"))]
+               let mut historical_inbound_htlc_fulfills = HashSet::new();
+               #[cfg(any(test, feature = "fuzztarget"))]
+               {
+                       let htlc_fulfills_len: u64 = Readable::read(reader)?;
+                       for _ in 0..htlc_fulfills_len {
+                               assert!(historical_inbound_htlc_fulfills.insert(Readable::read(reader)?));
+                       }
+               }
+
+               let pending_update_fee = if let Some(feerate) = pending_update_fee_value {
+                       Some((feerate, if channel_parameters.is_outbound_from_holder {
+                               FeeUpdateState::Outbound
+                       } else {
+                               FeeUpdateState::AwaitingRemoteRevokeToAnnounce
+                       }))
+               } else {
+                       None
+               };
+
                let mut announcement_sigs = None;
+               let mut target_closing_feerate_sats_per_kw = None;
                read_tlv_fields!(reader, {
                        (0, announcement_sigs, option),
                        (1, minimum_depth, option),
                        (3, counterparty_selected_channel_reserve_satoshis, option),
                        (5, config, option), // Note that if none is provided we will *not* overwrite the existing one.
+                       (7, shutdown_scriptpubkey, option),
+                       (9, target_closing_feerate_sats_per_kw, option),
                });
 
                let mut secp_ctx = Secp256k1::new();
@@ -4916,7 +5433,7 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                        latest_monitor_update_id,
 
                        holder_signer,
-                       shutdown_pubkey,
+                       shutdown_scriptpubkey,
                        destination_script,
 
                        cur_holder_commitment_transaction_number,
@@ -4947,7 +5464,10 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                        #[cfg(debug_assertions)]
                        counterparty_max_commitment_tx_output: Mutex::new((0, 0)),
 
-                       last_sent_closing_fee,
+                       last_sent_closing_fee: None,
+                       pending_counterparty_closing_signed: None,
+                       closing_fee_limits: None,
+                       target_closing_feerate_sats_per_kw,
 
                        funding_tx_confirmed_in,
                        funding_tx_confirmation_height,
@@ -4976,6 +5496,7 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                        commitment_secrets,
 
                        channel_update_status,
+                       closing_signed_in_flight: false,
 
                        announcement_sigs,
 
@@ -4985,6 +5506,9 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                        next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
 
                        workaround_lnd_bug_4006: None,
+
+                       #[cfg(any(test, feature = "fuzztarget"))]
+                       historical_inbound_htlc_fulfills,
                })
        }
 }
@@ -5006,6 +5530,7 @@ mod tests {
        use ln::channel::MAX_FUNDING_SATOSHIS;
        use ln::features::InitFeatures;
        use ln::msgs::{ChannelUpdate, DataLossProtect, DecodeError, OptionalField, UnsignedChannelUpdate};
+       use ln::script::ShutdownScript;
        use ln::chan_utils;
        use ln::chan_utils::{ChannelPublicKeys, HolderCommitmentTransaction, CounterpartyChannelTransactionParameters, HTLC_SUCCESS_TX_WEIGHT, HTLC_TIMEOUT_TX_WEIGHT};
        use chain::BestBlock;
@@ -5014,7 +5539,9 @@ mod tests {
        use chain::transaction::OutPoint;
        use util::config::UserConfig;
        use util::enforcing_trait_impls::EnforcingSigner;
+       use util::errors::APIError;
        use util::test_utils;
+       use util::test_utils::OnGetShutdownScriptpubkey;
        use util::logger::Logger;
        use bitcoin::secp256k1::{Secp256k1, Message, Signature, All};
        use bitcoin::secp256k1::ffi::Signature as FFISignature;
@@ -5023,6 +5550,7 @@ mod tests {
        use bitcoin::hashes::sha256::Hash as Sha256;
        use bitcoin::hashes::Hash;
        use bitcoin::hash_types::{Txid, WPubkeyHash};
+       use core::num::NonZeroU8;
        use sync::Arc;
        use prelude::*;
 
@@ -5055,10 +5583,10 @@ mod tests {
                        Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&channel_monitor_claim_key_hash[..]).into_script()
                }
 
-               fn get_shutdown_pubkey(&self) -> PublicKey {
+               fn get_shutdown_scriptpubkey(&self) -> ShutdownScript {
                        let secp_ctx = Secp256k1::signing_only();
                        let channel_close_key = SecretKey::from_slice(&hex::decode("0fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap()[..]).unwrap();
-                       PublicKey::from_secret_key(&secp_ctx, &channel_close_key)
+                       ShutdownScript::new_p2wpkh_from_pubkey(PublicKey::from_secret_key(&secp_ctx, &channel_close_key))
                }
 
                fn get_channel_signer(&self, _inbound: bool, _channel_value_satoshis: u64) -> InMemorySigner {
@@ -5073,6 +5601,32 @@ mod tests {
                PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&hex::decode(hex).unwrap()[..]).unwrap())
        }
 
+       #[test]
+       fn upfront_shutdown_script_incompatibility() {
+               let features = InitFeatures::known().clear_shutdown_anysegwit();
+               let non_v0_segwit_shutdown_script =
+                       ShutdownScript::new_witness_program(NonZeroU8::new(16).unwrap(), &[0, 40]).unwrap();
+
+               let seed = [42; 32];
+               let network = Network::Testnet;
+               let keys_provider = test_utils::TestKeysInterface::new(&seed, network);
+               keys_provider.expect(OnGetShutdownScriptpubkey {
+                       returns: non_v0_segwit_shutdown_script.clone(),
+               });
+
+               let fee_estimator = TestFeeEstimator { fee_est: 253 };
+               let secp_ctx = Secp256k1::new();
+               let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
+               let config = UserConfig::default();
+               match Channel::<EnforcingSigner>::new_outbound(&&fee_estimator, &&keys_provider, node_id, &features, 10000000, 100000, 42, &config) {
+                       Err(APIError::IncompatibleShutdownScript { script }) => {
+                               assert_eq!(script.into_inner(), non_v0_segwit_shutdown_script.into_inner());
+                       },
+                       Err(e) => panic!("Unexpected error: {:?}", e),
+                       Ok(_) => panic!("Expected error"),
+               }
+       }
+
        // Check that, during channel creation, we use the same feerate in the open channel message
        // as we do in the Channel object creation itself.
        #[test]
@@ -5086,7 +5640,7 @@ mod tests {
 
                let node_a_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&fee_est, &&keys_provider, node_a_node_id, 10000000, 100000, 42, &config).unwrap();
+               let node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&fee_est, &&keys_provider, node_a_node_id, &InitFeatures::known(), 10000000, 100000, 42, &config).unwrap();
 
                // Now change the fee so we can check that the fee in the open_channel message is the
                // same as the old fee.
@@ -5111,18 +5665,18 @@ mod tests {
                // Create Node A's channel pointing to Node B's pubkey
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&feeest, &&keys_provider, node_b_node_id, 10000000, 100000, 42, &config).unwrap();
+               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), 10000000, 100000, 42, &config).unwrap();
 
                // Create Node B's channel by receiving Node A's open_channel message
                // Make sure A's dust limit is as we expect.
                let open_channel_msg = node_a_chan.get_open_channel(genesis_block(network).header.block_hash());
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[7; 32]).unwrap());
-               let node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, InitFeatures::known(), &open_channel_msg, 7, &config).unwrap();
+               let node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), &open_channel_msg, 7, &config).unwrap();
 
                // Node B --> Node A: accept channel, explicitly setting B's dust limit.
                let mut accept_channel_msg = node_b_chan.get_accept_channel();
                accept_channel_msg.dust_limit_satoshis = 546;
-               node_a_chan.accept_channel(&accept_channel_msg, &config, InitFeatures::known()).unwrap();
+               node_a_chan.accept_channel(&accept_channel_msg, &config, &InitFeatures::known()).unwrap();
                node_a_chan.holder_dust_limit_satoshis = 1560;
 
                // Put some inbound and outbound HTLCs in A's channel.
@@ -5178,7 +5732,7 @@ mod tests {
 
                let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut chan = Channel::<EnforcingSigner>::new_outbound(&&fee_est, &&keys_provider, node_id, 10000000, 100000, 42, &config).unwrap();
+               let mut chan = Channel::<EnforcingSigner>::new_outbound(&&fee_est, &&keys_provider, node_id, &InitFeatures::known(), 10000000, 100000, 42, &config).unwrap();
 
                let commitment_tx_fee_0_htlcs = chan.commit_tx_fee_msat(0);
                let commitment_tx_fee_1_htlc = chan.commit_tx_fee_msat(1);
@@ -5227,16 +5781,16 @@ mod tests {
                // Create Node A's channel pointing to Node B's pubkey
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&feeest, &&keys_provider, node_b_node_id, 10000000, 100000, 42, &config).unwrap();
+               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), 10000000, 100000, 42, &config).unwrap();
 
                // Create Node B's channel by receiving Node A's open_channel message
                let open_channel_msg = node_a_chan.get_open_channel(chain_hash);
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[7; 32]).unwrap());
-               let mut node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, InitFeatures::known(), &open_channel_msg, 7, &config).unwrap();
+               let mut node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), &open_channel_msg, 7, &config).unwrap();
 
                // Node B --> Node A: accept channel
                let accept_channel_msg = node_b_chan.get_accept_channel();
-               node_a_chan.accept_channel(&accept_channel_msg, &config, InitFeatures::known()).unwrap();
+               node_a_chan.accept_channel(&accept_channel_msg, &config, &InitFeatures::known()).unwrap();
 
                // Node A --> Node B: funding created
                let output_script = node_a_chan.get_funding_redeemscript();
@@ -5289,7 +5843,7 @@ mod tests {
                // Create a channel.
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&feeest, &&keys_provider, node_b_node_id, 10000000, 100000, 42, &config).unwrap();
+               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), 10000000, 100000, 42, &config).unwrap();
                assert!(node_a_chan.counterparty_forwarding_info.is_none());
                assert_eq!(node_a_chan.holder_htlc_minimum_msat, 1); // the default
                assert!(node_a_chan.counterparty_forwarding_info().is_none());
@@ -5353,7 +5907,7 @@ mod tests {
                let counterparty_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let mut config = UserConfig::default();
                config.channel_options.announced_channel = false;
-               let mut chan = Channel::<InMemorySigner>::new_outbound(&&feeest, &&keys_provider, counterparty_node_id, 10_000_000, 100000, 42, &config).unwrap(); // Nothing uses their network key in this test
+               let mut chan = Channel::<InMemorySigner>::new_outbound(&&feeest, &&keys_provider, counterparty_node_id, &InitFeatures::known(), 10_000_000, 100000, 42, &config).unwrap(); // Nothing uses their network key in this test
                chan.holder_dust_limit_satoshis = 546;
                chan.counterparty_selected_channel_reserve_satoshis = Some(0); // Filled in in accept_channel
 
@@ -5397,9 +5951,9 @@ mod tests {
                                $( { $htlc_idx: expr, $counterparty_htlc_sig_hex: expr, $htlc_sig_hex: expr, $htlc_tx_hex: expr } ), *
                        } ) => { {
                                let (commitment_tx, htlcs): (_, Vec<HTLCOutputInCommitment>) = {
-                                       let mut res = chan.build_commitment_transaction(0xffffffffffff - 42, &keys, true, false, chan.feerate_per_kw, &logger);
+                                       let mut res = chan.build_commitment_transaction(0xffffffffffff - 42, &keys, true, false, &logger);
 
-                                       let htlcs = res.2.drain(..)
+                                       let htlcs = res.3.drain(..)
                                                .filter_map(|(htlc, _)| if htlc.transaction_output_index.is_some() { Some(htlc) } else { None })
                                                .collect();
                                        (res.0, htlcs)