Support atomic partial updates to ChannelConfig
[rust-lightning] / lightning / src / ln / channel.rs
index 73683eec32680575e9a97bcc9db5b0f6f89f81a0..99b3c1691149960f599ab532a98419da03b66c8c 100644 (file)
@@ -25,7 +25,7 @@ use bitcoin::secp256k1;
 use crate::ln::{PaymentPreimage, PaymentHash};
 use crate::ln::features::{ChannelTypeFeatures, InitFeatures};
 use crate::ln::msgs;
-use crate::ln::msgs::{DecodeError, OptionalField, DataLossProtect};
+use crate::ln::msgs::DecodeError;
 use crate::ln::script::{self, ShutdownScript};
 use crate::ln::channelmanager::{self, CounterpartyForwardingInfo, PendingHTLCStatus, HTLCSource, SentHTLCId, HTLCFailureMsg, PendingHTLCInfo, RAACommitmentOrder, BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA, MAX_LOCAL_BREAKDOWN_TIMEOUT};
 use crate::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, ClosingTransaction};
@@ -35,7 +35,7 @@ use crate::chain::BestBlock;
 use crate::chain::chaininterface::{FeeEstimator, ConfirmationTarget, LowerBoundedFeeEstimator};
 use crate::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateStep, LATENCY_GRACE_PERIOD_BLOCKS, CLOSED_CHANNEL_UPDATE_ID};
 use crate::chain::transaction::{OutPoint, TransactionData};
-use crate::chain::keysinterface::{WriteableEcdsaChannelSigner, EntropySource, ChannelSigner, SignerProvider, NodeSigner, Recipient};
+use crate::sign::{WriteableEcdsaChannelSigner, EntropySource, ChannelSigner, SignerProvider, NodeSigner, Recipient};
 use crate::events::ClosureReason;
 use crate::routing::gossip::NodeId;
 use crate::util::ser::{Readable, ReadableArgs, Writeable, Writer, VecWriter};
@@ -432,6 +432,12 @@ pub(super) struct ReestablishResponses {
        pub shutdown_msg: Option<msgs::Shutdown>,
 }
 
+/// The return type of `force_shutdown`
+pub(crate) type ShutdownResult = (
+       Option<(PublicKey, OutPoint, ChannelMonitorUpdate)>,
+       Vec<(HTLCSource, PaymentHash, PublicKey, [u8; 32])>
+);
+
 /// 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
@@ -479,6 +485,13 @@ pub(crate) const MIN_AFFORDABLE_HTLC_COUNT: usize = 4;
 ///   * `EXPIRE_PREV_CONFIG_TICKS` = convergence_delay / tick_interval
 pub(crate) const EXPIRE_PREV_CONFIG_TICKS: usize = 5;
 
+/// The number of ticks that may elapse while we're waiting for a response to a
+/// [`msgs::RevokeAndACK`] or [`msgs::ChannelReestablish`] message before we attempt to disconnect
+/// them.
+///
+/// See [`Channel::sent_message_awaiting_response`] for more information.
+pub(crate) const DISCONNECT_PEER_AWAITING_RESPONSE_TICKS: usize = 2;
+
 struct PendingChannelMonitorUpdate {
        update: ChannelMonitorUpdate,
        /// In some cases we need to delay letting the [`ChannelMonitorUpdate`] go until after an
@@ -715,6 +728,19 @@ pub(super) struct Channel<Signer: ChannelSigner> {
        /// See-also <https://github.com/lightningnetwork/lnd/issues/4006>
        pub workaround_lnd_bug_4006: Option<msgs::ChannelReady>,
 
+       /// An option set when we wish to track how many ticks have elapsed while waiting for a response
+       /// from our counterparty after sending a message. If the peer has yet to respond after reaching
+       /// `DISCONNECT_PEER_AWAITING_RESPONSE_TICKS`, a reconnection should be attempted to try to
+       /// unblock the state machine.
+       ///
+       /// This behavior is mostly motivated by a lnd bug in which we don't receive a message we expect
+       /// to in a timely manner, which may lead to channels becoming unusable and/or force-closed. An
+       /// example of such can be found at <https://github.com/lightningnetwork/lnd/issues/7682>.
+       ///
+       /// This is currently only used when waiting for a [`msgs::ChannelReestablish`] or
+       /// [`msgs::RevokeAndACK`] message from the counterparty.
+       sent_message_awaiting_response: Option<usize>,
+
        #[cfg(any(test, fuzzing))]
        // 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
@@ -1001,7 +1027,10 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 
                let shutdown_scriptpubkey = if config.channel_handshake_config.commit_upfront_shutdown_pubkey {
-                       Some(signer_provider.get_shutdown_scriptpubkey())
+                       match signer_provider.get_shutdown_scriptpubkey() {
+                               Ok(scriptpubkey) => Some(scriptpubkey),
+                               Err(_) => return Err(APIError::ChannelUnavailable { err: "Failed to get shutdown scriptpubkey".to_owned()}),
+                       }
                } else { None };
 
                if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
@@ -1010,6 +1039,11 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        }
                }
 
+               let destination_script = match signer_provider.get_destination_script() {
+                       Ok(script) => script,
+                       Err(_) => return Err(APIError::ChannelUnavailable { err: "Failed to get destination script".to_owned()}),
+               };
+
                let temporary_channel_id = entropy_source.get_secure_random_bytes();
 
                Ok(Channel {
@@ -1036,7 +1070,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
                        holder_signer,
                        shutdown_scriptpubkey,
-                       destination_script: signer_provider.get_destination_script(),
+                       destination_script,
 
                        cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
                        cur_counterparty_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
@@ -1122,6 +1156,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
 
                        workaround_lnd_bug_4006: None,
+                       sent_message_awaiting_response: None,
 
                        latest_inbound_scid_alias: None,
                        outbound_scid_alias,
@@ -1329,7 +1364,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
                let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
                        match &msg.shutdown_scriptpubkey {
-                               &OptionalField::Present(ref script) => {
+                               &Some(ref script) => {
                                        // Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
                                        if script.len() == 0 {
                                                None
@@ -1341,14 +1376,17 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                                        }
                                },
                                // 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
-                               &OptionalField::Absent => {
+                               &None => {
                                        return Err(ChannelError::Close("Peer is signaling upfront_shutdown but we don't get any script. Use 0-length script to opt-out".to_owned()));
                                }
                        }
                } else { None };
 
                let shutdown_scriptpubkey = if config.channel_handshake_config.commit_upfront_shutdown_pubkey {
-                       Some(signer_provider.get_shutdown_scriptpubkey())
+                       match signer_provider.get_shutdown_scriptpubkey() {
+                               Ok(scriptpubkey) => Some(scriptpubkey),
+                               Err(_) => return Err(ChannelError::Close("Failed to get upfront shutdown scriptpubkey".to_owned())),
+                       }
                } else { None };
 
                if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
@@ -1357,6 +1395,11 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        }
                }
 
+               let destination_script = match signer_provider.get_destination_script() {
+                       Ok(script) => script,
+                       Err(_) => return Err(ChannelError::Close("Failed to get destination script".to_owned())),
+               };
+
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 
@@ -1383,7 +1426,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
                        holder_signer,
                        shutdown_scriptpubkey,
-                       destination_script: signer_provider.get_destination_script(),
+                       destination_script,
 
                        cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
                        cur_counterparty_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
@@ -1473,6 +1516,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
 
                        workaround_lnd_bug_4006: None,
+                       sent_message_awaiting_response: None,
 
                        latest_inbound_scid_alias: None,
                        outbound_scid_alias,
@@ -2230,7 +2274,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
                let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
                        match &msg.shutdown_scriptpubkey {
-                               &OptionalField::Present(ref script) => {
+                               &Some(ref script) => {
                                        // Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
                                        if script.len() == 0 {
                                                None
@@ -2242,7 +2286,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                                        }
                                },
                                // 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
-                               &OptionalField::Absent => {
+                               &None => {
                                        return Err(ChannelError::Close("Peer is signaling upfront_shutdown but we don't get any script. Use 0-length script to opt-out".to_owned()));
                                }
                        }
@@ -3510,6 +3554,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                // OK, we step the channel here and *then* if the new generation fails we can fail the
                // channel based on that, but stepping stuff here should be safe either way.
                self.channel_state &= !(ChannelState::AwaitingRemoteRevoke as u32);
+               self.sent_message_awaiting_response = None;
                self.counterparty_prev_commitment_point = self.counterparty_cur_commitment_point;
                self.counterparty_cur_commitment_point = Some(msg.next_per_commitment_point);
                self.cur_counterparty_commitment_transaction_number -= 1;
@@ -3825,6 +3870,8 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        }
                }
 
+               self.sent_message_awaiting_response = None;
+
                self.channel_state |= ChannelState::PeerDisconnected as u32;
                log_trace!(logger, "Peer disconnection resulted in {} remote-announced HTLC drops on channel {}", inbound_drop_count, log_bytes!(self.channel_id()));
        }
@@ -3927,6 +3974,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        Some(self.get_last_revoke_and_ack())
                } else { None };
                let commitment_update = if self.monitor_pending_commitment_signed {
+                       self.mark_awaiting_response();
                        Some(self.get_last_commitment_update(logger))
                } else { None };
 
@@ -4076,36 +4124,31 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
                if msg.next_local_commitment_number >= INITIAL_COMMITMENT_NUMBER || msg.next_remote_commitment_number >= INITIAL_COMMITMENT_NUMBER ||
                        msg.next_local_commitment_number == 0 {
-                       return Err(ChannelError::Close("Peer sent a garbage channel_reestablish".to_owned()));
+                       return Err(ChannelError::Close("Peer sent a garbage channel_reestablish (usually an lnd node with lost state asking us to force-close for them)".to_owned()));
                }
 
                if msg.next_remote_commitment_number > 0 {
-                       match msg.data_loss_protect {
-                               OptionalField::Present(ref data_loss) => {
-                                       let expected_point = self.holder_signer.get_per_commitment_point(INITIAL_COMMITMENT_NUMBER - msg.next_remote_commitment_number + 1, &self.secp_ctx);
-                                       let given_secret = SecretKey::from_slice(&data_loss.your_last_per_commitment_secret)
-                                               .map_err(|_| ChannelError::Close("Peer sent a garbage channel_reestablish with unparseable secret key".to_owned()))?;
-                                       if expected_point != PublicKey::from_secret_key(&self.secp_ctx, &given_secret) {
-                                               return Err(ChannelError::Close("Peer sent a garbage channel_reestablish with secret key not matching the commitment height provided".to_owned()));
+                       let expected_point = self.holder_signer.get_per_commitment_point(INITIAL_COMMITMENT_NUMBER - msg.next_remote_commitment_number + 1, &self.secp_ctx);
+                       let given_secret = SecretKey::from_slice(&msg.your_last_per_commitment_secret)
+                               .map_err(|_| ChannelError::Close("Peer sent a garbage channel_reestablish with unparseable secret key".to_owned()))?;
+                       if expected_point != PublicKey::from_secret_key(&self.secp_ctx, &given_secret) {
+                               return Err(ChannelError::Close("Peer sent a garbage channel_reestablish with secret key not matching the commitment height provided".to_owned()));
+                       }
+                       if msg.next_remote_commitment_number > INITIAL_COMMITMENT_NUMBER - self.cur_holder_commitment_transaction_number {
+                               macro_rules! log_and_panic {
+                                       ($err_msg: expr) => {
+                                               log_error!(logger, $err_msg, log_bytes!(self.channel_id), log_pubkey!(self.counterparty_node_id));
+                                               panic!($err_msg, log_bytes!(self.channel_id), log_pubkey!(self.counterparty_node_id));
                                        }
-                                       if msg.next_remote_commitment_number > INITIAL_COMMITMENT_NUMBER - self.cur_holder_commitment_transaction_number {
-                                               macro_rules! log_and_panic {
-                                                       ($err_msg: expr) => {
-                                                               log_error!(logger, $err_msg, log_bytes!(self.channel_id), log_pubkey!(self.counterparty_node_id));
-                                                               panic!($err_msg, log_bytes!(self.channel_id), log_pubkey!(self.counterparty_node_id));
-                                                       }
-                                               }
-                                               log_and_panic!("We have fallen behind - we have received proof that if we broadcast our counterparty is going to claim all our funds.\n\
-                                                       This implies you have restarted with lost ChannelMonitor and ChannelManager state, the first of which is a violation of the LDK chain::Watch requirements.\n\
-                                                       More specifically, this means you have a bug in your implementation that can cause loss of funds, or you are running with an old backup, which is unsafe.\n\
-                                                       If you have restored from an old backup and wish to force-close channels and return to operation, you should start up, call\n\
-                                                       ChannelManager::force_close_without_broadcasting_txn on channel {} with counterparty {} or\n\
-                                                       ChannelManager::force_close_all_channels_without_broadcasting_txn, then reconnect to peer(s).\n\
-                                                       Note that due to a long-standing bug in lnd you may have to reach out to peers running lnd-based nodes to ask them to manually force-close channels\n\
-                                                       See https://github.com/lightningdevkit/rust-lightning/issues/1565 for more info.");
-                                       }
-                               },
-                               OptionalField::Absent => {}
+                               }
+                               log_and_panic!("We have fallen behind - we have received proof that if we broadcast our counterparty is going to claim all our funds.\n\
+                                       This implies you have restarted with lost ChannelMonitor and ChannelManager state, the first of which is a violation of the LDK chain::Watch requirements.\n\
+                                       More specifically, this means you have a bug in your implementation that can cause loss of funds, or you are running with an old backup, which is unsafe.\n\
+                                       If you have restored from an old backup and wish to force-close channels and return to operation, you should start up, call\n\
+                                       ChannelManager::force_close_without_broadcasting_txn on channel {} with counterparty {} or\n\
+                                       ChannelManager::force_close_all_channels_without_broadcasting_txn, then reconnect to peer(s).\n\
+                                       Note that due to a long-standing bug in lnd you may have to reach out to peers running lnd-based nodes to ask them to manually force-close channels\n\
+                                       See https://github.com/lightningdevkit/rust-lightning/issues/1565 for more info.");
                        }
                }
 
@@ -4121,6 +4164,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                // Go ahead and unmark PeerDisconnected as various calls we may make check for it (and all
                // remaining cases either succeed or ErrorMessage-fail).
                self.channel_state &= !(ChannelState::PeerDisconnected as u32);
+               self.sent_message_awaiting_response = None;
 
                let shutdown_msg = if self.channel_state & (ChannelState::LocalShutdownSent as u32) != 0 {
                        assert!(self.shutdown_scriptpubkey.is_some());
@@ -4181,7 +4225,11 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                // revoke_and_ack, not on sending commitment_signed, so we add one if have
                // AwaitingRemoteRevoke set, which indicates we sent a commitment_signed but haven't gotten
                // the corresponding revoke_and_ack back yet.
-               let next_counterparty_commitment_number = INITIAL_COMMITMENT_NUMBER - self.cur_counterparty_commitment_transaction_number + if (self.channel_state & ChannelState::AwaitingRemoteRevoke as u32) != 0 { 1 } else { 0 };
+               let is_awaiting_remote_revoke = self.channel_state & ChannelState::AwaitingRemoteRevoke as u32 != 0;
+               if is_awaiting_remote_revoke && !self.is_awaiting_monitor_update() {
+                       self.mark_awaiting_response();
+               }
+               let next_counterparty_commitment_number = INITIAL_COMMITMENT_NUMBER - self.cur_counterparty_commitment_transaction_number + if is_awaiting_remote_revoke { 1 } else { 0 };
 
                let channel_ready = if msg.next_local_commitment_number == 1 && INITIAL_COMMITMENT_NUMBER - self.cur_holder_commitment_transaction_number == 1 {
                        // We should never have to worry about MonitorUpdateInProgress resending ChannelReady
@@ -4350,6 +4398,28 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                }), None))
        }
 
+       // Marks a channel as waiting for a response from the counterparty. If it's not received
+       // [`DISCONNECT_PEER_AWAITING_RESPONSE_TICKS`] after sending our own to them, then we'll attempt
+       // a reconnection.
+       fn mark_awaiting_response(&mut self) {
+               self.sent_message_awaiting_response = Some(0);
+       }
+
+       /// Determines whether we should disconnect the counterparty due to not receiving a response
+       /// within our expected timeframe.
+       ///
+       /// This should be called on every [`super::channelmanager::ChannelManager::timer_tick_occurred`].
+       pub fn should_disconnect_peer_awaiting_response(&mut self) -> bool {
+               let ticks_elapsed = if let Some(ticks_elapsed) = self.sent_message_awaiting_response.as_mut() {
+                       ticks_elapsed
+               } else {
+                       // Don't disconnect when we're not waiting on a response.
+                       return false;
+               };
+               *ticks_elapsed += 1;
+               *ticks_elapsed >= DISCONNECT_PEER_AWAITING_RESPONSE_TICKS
+       }
+
        pub fn shutdown<SP: Deref>(
                &mut self, signer_provider: &SP, their_features: &InitFeatures, msg: &msgs::Shutdown
        ) -> Result<(Option<msgs::Shutdown>, Option<&ChannelMonitorUpdate>, Vec<(HTLCSource, PaymentHash)>), ChannelError>
@@ -4392,7 +4462,10 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        Some(_) => false,
                        None => {
                                assert!(send_shutdown);
-                               let shutdown_scriptpubkey = signer_provider.get_shutdown_scriptpubkey();
+                               let shutdown_scriptpubkey = match signer_provider.get_shutdown_scriptpubkey() {
+                                       Ok(scriptpubkey) => scriptpubkey,
+                                       Err(_) => return Err(ChannelError::Close("Failed to get shutdown scriptpubkey".to_owned())),
+                               };
                                if !shutdown_scriptpubkey.is_compatible(their_features) {
                                        return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer: {}", shutdown_scriptpubkey)));
                                }
@@ -5030,10 +5103,25 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                self.pending_monitor_updates.is_empty()
        }
 
+       pub fn complete_all_mon_updates_through(&mut self, update_id: u64) {
+               self.pending_monitor_updates.retain(|upd| {
+                       if upd.update.update_id <= update_id {
+                               assert!(!upd.blocked, "Completed update must have flown");
+                               false
+                       } else { true }
+               });
+       }
+
        pub fn complete_one_mon_update(&mut self, update_id: u64) {
                self.pending_monitor_updates.retain(|upd| upd.update.update_id != update_id);
        }
 
+       /// Returns an iterator over all unblocked monitor updates which have not yet completed.
+       pub fn uncompleted_unblocked_mon_updates(&self) -> impl Iterator<Item=&ChannelMonitorUpdate> {
+               self.pending_monitor_updates.iter()
+                       .filter_map(|upd| if upd.blocked { None } else { Some(&upd.update) })
+       }
+
        /// Returns true if funding_created was sent/received.
        pub fn is_funding_initiated(&self) -> bool {
                self.channel_state >= ChannelState::FundingSent as u32
@@ -5402,7 +5490,7 @@ impl<Signer: WriteableEcdsaChannelSigner> 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(match &self.shutdown_scriptpubkey {
+                       shutdown_scriptpubkey: Some(match &self.shutdown_scriptpubkey {
                                Some(script) => script.clone().into_inner(),
                                None => Builder::new().into_script(),
                        }),
@@ -5468,7 +5556,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        delayed_payment_basepoint: keys.delayed_payment_basepoint,
                        htlc_basepoint: keys.htlc_basepoint,
                        first_per_commitment_point,
-                       shutdown_scriptpubkey: OptionalField::Present(match &self.shutdown_scriptpubkey {
+                       shutdown_scriptpubkey: Some(match &self.shutdown_scriptpubkey {
                                Some(script) => script.clone().into_inner(),
                                None => Builder::new().into_script(),
                        }),
@@ -5719,7 +5807,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
        /// May panic if called on a channel that wasn't immediately-previously
        /// self.remove_uncommitted_htlcs_and_mark_paused()'d
-       pub fn get_channel_reestablish<L: Deref>(&self, logger: &L) -> msgs::ChannelReestablish where L::Target: Logger {
+       pub fn get_channel_reestablish<L: Deref>(&mut self, logger: &L) -> msgs::ChannelReestablish where L::Target: Logger {
                assert_eq!(self.channel_state & ChannelState::PeerDisconnected as u32, ChannelState::PeerDisconnected as u32);
                assert_ne!(self.cur_counterparty_commitment_transaction_number, INITIAL_COMMITMENT_NUMBER);
                // Prior to static_remotekey, my_current_per_commitment_point was critical to claiming
@@ -5730,20 +5818,15 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                // valid, and valid in fuzzing mode's arbitrary validity criteria:
                let mut pk = [2; 33]; pk[1] = 0xff;
                let dummy_pubkey = PublicKey::from_slice(&pk).unwrap();
-               let data_loss_protect = if self.cur_counterparty_commitment_transaction_number + 1 < INITIAL_COMMITMENT_NUMBER {
+               let remote_last_secret = if self.cur_counterparty_commitment_transaction_number + 1 < INITIAL_COMMITMENT_NUMBER {
                        let remote_last_secret = self.commitment_secrets.get_secret(self.cur_counterparty_commitment_transaction_number + 2).unwrap();
                        log_trace!(logger, "Enough info to generate a Data Loss Protect with per_commitment_secret {} for channel {}", log_bytes!(remote_last_secret), log_bytes!(self.channel_id()));
-                       OptionalField::Present(DataLossProtect {
-                               your_last_per_commitment_secret: remote_last_secret,
-                               my_current_per_commitment_point: dummy_pubkey
-                       })
+                       remote_last_secret
                } else {
                        log_info!(logger, "Sending a data_loss_protect with no previous remote per_commitment_secret for channel {}", log_bytes!(self.channel_id()));
-                       OptionalField::Present(DataLossProtect {
-                               your_last_per_commitment_secret: [0;32],
-                               my_current_per_commitment_point: dummy_pubkey,
-                       })
+                       [0;32]
                };
+               self.mark_awaiting_response();
                msgs::ChannelReestablish {
                        channel_id: self.channel_id(),
                        // The protocol has two different commitment number concepts - the "commitment
@@ -5764,7 +5847,12 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        // dropped this channel on disconnect as it hasn't yet reached FundingSent so we can't
                        // overflow here.
                        next_remote_commitment_number: INITIAL_COMMITMENT_NUMBER - self.cur_counterparty_commitment_transaction_number - 1,
-                       data_loss_protect,
+                       your_last_per_commitment_secret: remote_last_secret,
+                       my_current_per_commitment_point: dummy_pubkey,
+                       // TODO(dual_funding): If we've sent `commtiment_signed` for an interactive transaction
+                       // construction but have not received `tx_signatures` we MUST set `next_funding_txid` to the
+                       // txid of that interactive transaction, else we MUST NOT set it.
+                       next_funding_txid: None,
                }
        }
 
@@ -6109,7 +6197,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
        /// May jump to the channel being fully shutdown (see [`Self::is_shutdown`]) in which case no
        /// [`ChannelMonitorUpdate`] will be returned).
        pub fn get_shutdown<SP: Deref>(&mut self, signer_provider: &SP, their_features: &InitFeatures,
-               target_feerate_sats_per_kw: Option<u32>)
+               target_feerate_sats_per_kw: Option<u32>, override_shutdown_script: Option<ShutdownScript>)
        -> Result<(msgs::Shutdown, Option<&ChannelMonitorUpdate>, Vec<(HTLCSource, PaymentHash)>), APIError>
        where SP::Target: SignerProvider {
                for htlc in self.pending_outbound_htlcs.iter() {
@@ -6125,6 +6213,9 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                                return Err(APIError::ChannelUnavailable{err: "Shutdown already in progress by remote".to_owned()});
                        }
                }
+               if self.shutdown_scriptpubkey.is_some() && override_shutdown_script.is_some() {
+                       return Err(APIError::APIMisuseError{err: "Cannot override shutdown script for a channel with one already set".to_owned()});
+               }
                assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
                if self.channel_state & (ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateInProgress as u32) != 0 {
                        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()});
@@ -6140,7 +6231,17 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                let update_shutdown_script = match self.shutdown_scriptpubkey {
                        Some(_) => false,
                        None if !chan_closed => {
-                               let shutdown_scriptpubkey = signer_provider.get_shutdown_scriptpubkey();
+                               // use override shutdown script if provided
+                               let shutdown_scriptpubkey = match override_shutdown_script {
+                                       Some(script) => script,
+                                       None => {
+                                               // otherwise, use the shutdown scriptpubkey provided by the signer
+                                               match signer_provider.get_shutdown_scriptpubkey() {
+                                                       Ok(scriptpubkey) => scriptpubkey,
+                                                       Err(_) => return Err(APIError::ChannelUnavailable{err: "Failed to get shutdown scriptpubkey".to_owned()}),
+                                               }
+                                       },
+                               };
                                if !shutdown_scriptpubkey.is_compatible(their_features) {
                                        return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
                                }
@@ -6202,7 +6303,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
        /// those explicitly stated to be allowed after shutdown completes, eg some simple getters).
        /// Also returns the list of payment_hashes for channels which we can safely fail backwards
        /// immediately (others we will have to allow to time out).
-       pub fn force_shutdown(&mut self, should_broadcast: bool) -> (Option<(OutPoint, ChannelMonitorUpdate)>, Vec<(HTLCSource, PaymentHash, PublicKey, [u8; 32])>) {
+       pub fn force_shutdown(&mut self, should_broadcast: bool) -> ShutdownResult {
                // Note that we MUST only generate a monitor update that indicates force-closure - we're
                // called during initialization prior to the chain_monitor in the encompassing ChannelManager
                // being fully configured in some cases. Thus, its likely any monitor events we generate will
@@ -6231,7 +6332,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        // See test_duplicate_chan_id and test_pre_lockin_no_chan_closed_update for more.
                        if self.channel_state & (ChannelState::FundingSent as u32 | ChannelState::ChannelReady as u32 | ChannelState::ShutdownComplete as u32) != 0 {
                                self.latest_monitor_update_id = CLOSED_CHANNEL_UPDATE_ID;
-                               Some((funding_txo, ChannelMonitorUpdate {
+                               Some((self.get_counterparty_node_id(), funding_txo, ChannelMonitorUpdate {
                                        update_id: self.latest_monitor_update_id,
                                        updates: vec![ChannelMonitorUpdateStep::ChannelForceClosed { should_broadcast }],
                                }))
@@ -7064,6 +7165,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
                        next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
 
                        workaround_lnd_bug_4006: None,
+                       sent_message_awaiting_response: None,
 
                        latest_inbound_scid_alias,
                        // Later in the ChannelManager deserialization phase we scan for channels and assign scid aliases if its missing
@@ -7099,13 +7201,13 @@ mod tests {
        use crate::ln::channel::{Channel, InboundHTLCOutput, OutboundHTLCOutput, InboundHTLCState, OutboundHTLCState, HTLCCandidate, HTLCInitiator};
        use crate::ln::channel::{MAX_FUNDING_SATOSHIS_NO_WUMBO, TOTAL_BITCOIN_SUPPLY_SATOSHIS, MIN_THEIR_CHAN_RESERVE_SATOSHIS};
        use crate::ln::features::ChannelTypeFeatures;
-       use crate::ln::msgs::{ChannelUpdate, DataLossProtect, DecodeError, OptionalField, UnsignedChannelUpdate, MAX_VALUE_MSAT};
+       use crate::ln::msgs::{ChannelUpdate, DecodeError, UnsignedChannelUpdate, MAX_VALUE_MSAT};
        use crate::ln::script::ShutdownScript;
        use crate::ln::chan_utils;
        use crate::ln::chan_utils::{htlc_success_tx_weight, htlc_timeout_tx_weight};
        use crate::chain::BestBlock;
        use crate::chain::chaininterface::{FeeEstimator, LowerBoundedFeeEstimator, ConfirmationTarget};
-       use crate::chain::keysinterface::{ChannelSigner, InMemorySigner, EntropySource, SignerProvider};
+       use crate::sign::{ChannelSigner, InMemorySigner, EntropySource, SignerProvider};
        use crate::chain::transaction::OutPoint;
        use crate::routing::router::Path;
        use crate::util::config::UserConfig;
@@ -7170,17 +7272,17 @@ mod tests {
 
                fn read_chan_signer(&self, _data: &[u8]) -> Result<Self::Signer, DecodeError> { panic!(); }
 
-               fn get_destination_script(&self) -> Script {
+               fn get_destination_script(&self) -> Result<Script, ()> {
                        let secp_ctx = Secp256k1::signing_only();
                        let channel_monitor_claim_key = SecretKey::from_slice(&hex::decode("0fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap()[..]).unwrap();
                        let channel_monitor_claim_key_hash = WPubkeyHash::hash(&PublicKey::from_secret_key(&secp_ctx, &channel_monitor_claim_key).serialize());
-                       Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&channel_monitor_claim_key_hash[..]).into_script()
+                       Ok(Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&channel_monitor_claim_key_hash[..]).into_script())
                }
 
-               fn get_shutdown_scriptpubkey(&self) -> ShutdownScript {
+               fn get_shutdown_scriptpubkey(&self) -> Result<ShutdownScript, ()> {
                        let secp_ctx = Secp256k1::signing_only();
                        let channel_close_key = SecretKey::from_slice(&hex::decode("0fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap()[..]).unwrap();
-                       ShutdownScript::new_p2wpkh_from_pubkey(PublicKey::from_secret_key(&secp_ctx, &channel_close_key))
+                       Ok(ShutdownScript::new_p2wpkh_from_pubkey(PublicKey::from_secret_key(&secp_ctx, &channel_close_key)))
                }
        }
 
@@ -7400,12 +7502,7 @@ mod tests {
                let msg = node_b_chan.get_channel_reestablish(&&logger);
                assert_eq!(msg.next_local_commitment_number, 1); // now called next_commitment_number
                assert_eq!(msg.next_remote_commitment_number, 0); // now called next_revocation_number
-               match msg.data_loss_protect {
-                       OptionalField::Present(DataLossProtect { your_last_per_commitment_secret, .. }) => {
-                               assert_eq!(your_last_per_commitment_secret, [0; 32]);
-                       },
-                       _ => panic!()
-               }
+               assert_eq!(msg.your_last_per_commitment_secret, [0; 32]);
 
                // Check that the commitment point in Node A's channel_reestablish message
                // is sane.
@@ -7413,12 +7510,7 @@ mod tests {
                let msg = node_a_chan.get_channel_reestablish(&&logger);
                assert_eq!(msg.next_local_commitment_number, 1); // now called next_commitment_number
                assert_eq!(msg.next_remote_commitment_number, 0); // now called next_revocation_number
-               match msg.data_loss_protect {
-                       OptionalField::Present(DataLossProtect { your_last_per_commitment_secret, .. }) => {
-                               assert_eq!(your_last_per_commitment_secret, [0; 32]);
-                       },
-                       _ => panic!()
-               }
+               assert_eq!(msg.your_last_per_commitment_secret, [0; 32]);
        }
 
        #[test]
@@ -7609,7 +7701,7 @@ mod tests {
                use bitcoin::hashes::hex::FromHex;
                use bitcoin::hash_types::Txid;
                use bitcoin::secp256k1::Message;
-               use crate::chain::keysinterface::EcdsaChannelSigner;
+               use crate::sign::EcdsaChannelSigner;
                use crate::ln::PaymentPreimage;
                use crate::ln::channel::{HTLCOutputInCommitment ,TxCreationKeys};
                use crate::ln::chan_utils::{ChannelPublicKeys, HolderCommitmentTransaction, CounterpartyChannelTransactionParameters};