Merge pull request #2368 from wpaulino/inbound-anchors-manual-acceptance
[rust-lightning] / lightning / src / ln / channelmanager.rs
index 808c7ffcd3ac2196e5961f406f13d5f347fee0c5..a03f11d57443f340713909cac761e057d7637ead 100644 (file)
@@ -50,7 +50,7 @@ use crate::routing::scoring::{ProbabilisticScorer, ProbabilisticScoringFeeParame
 use crate::ln::msgs;
 use crate::ln::onion_utils;
 use crate::ln::onion_utils::HTLCFailReason;
-use crate::ln::msgs::{ChannelMessageHandler, DecodeError, LightningError, MAX_VALUE_MSAT};
+use crate::ln::msgs::{ChannelMessageHandler, DecodeError, LightningError};
 #[cfg(test)]
 use crate::ln::outbound_payment;
 use crate::ln::outbound_payment::{OutboundPayments, PaymentAttempts, PendingOutboundPayment};
@@ -633,6 +633,13 @@ pub(super) struct PeerState<Signer: ChannelSigner> {
        /// Messages to send to the peer - pushed to in the same lock that they are generated in (except
        /// for broadcast messages, where ordering isn't as strict).
        pub(super) pending_msg_events: Vec<MessageSendEvent>,
+       /// Map from Channel IDs to pending [`ChannelMonitorUpdate`]s which have been passed to the
+       /// user but which have not yet completed.
+       ///
+       /// Note that the channel may no longer exist. For example if the channel was closed but we
+       /// later needed to claim an HTLC which is pending on-chain, we may generate a monitor update
+       /// for a missing channel.
+       in_flight_monitor_updates: BTreeMap<OutPoint, Vec<ChannelMonitorUpdate>>,
        /// Map from a specific channel to some action(s) that should be taken when all pending
        /// [`ChannelMonitorUpdate`]s for the channel complete updating.
        ///
@@ -668,6 +675,7 @@ impl <Signer: ChannelSigner> PeerState<Signer> {
                        return false
                }
                self.channel_by_id.is_empty() && self.monitor_update_blocked_actions.is_empty()
+                       && self.in_flight_monitor_updates.is_empty()
        }
 
        // Returns a count of all channels we have with this peer, including pending channels.
@@ -1811,7 +1819,7 @@ macro_rules! emit_channel_ready_event {
 }
 
 macro_rules! handle_monitor_update_completion {
-       ($self: ident, $update_id: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan: expr) => { {
+       ($self: ident, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan: expr) => { {
                let mut updates = $chan.monitor_updating_restored(&$self.logger,
                        &$self.node_signer, $self.genesis_hash, &$self.default_configuration,
                        $self.best_block.read().unwrap().height());
@@ -1860,7 +1868,7 @@ macro_rules! handle_monitor_update_completion {
 }
 
 macro_rules! handle_new_monitor_update {
-       ($self: ident, $update_res: expr, $update_id: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan: expr, MANUALLY_REMOVING, $remove: expr) => { {
+       ($self: ident, $update_res: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan: expr, _internal, $remove: expr, $completed: expr) => { {
                // update_maps_on_chan_removal needs to be able to take id_to_peer, so make sure we can in
                // any case so that it won't deadlock.
                debug_assert_ne!($self.id_to_peer.held_by_thread(), LockHeldState::HeldByThread);
@@ -1871,13 +1879,13 @@ macro_rules! handle_new_monitor_update {
                        ChannelMonitorUpdateStatus::InProgress => {
                                log_debug!($self.logger, "ChannelMonitor update for {} in flight, holding messages until the update completes.",
                                        log_bytes!($chan.context.channel_id()[..]));
-                               Ok(())
+                               Ok(false)
                        },
                        ChannelMonitorUpdateStatus::PermanentFailure => {
                                log_error!($self.logger, "Closing channel {} due to monitor update ChannelMonitorUpdateStatus::PermanentFailure",
                                        log_bytes!($chan.context.channel_id()[..]));
                                update_maps_on_chan_removal!($self, &$chan.context);
-                               let res: Result<(), _> = Err(MsgHandleErrInternal::from_finish_shutdown(
+                               let res = Err(MsgHandleErrInternal::from_finish_shutdown(
                                        "ChannelMonitor storage failure".to_owned(), $chan.context.channel_id(),
                                        $chan.context.get_user_id(), $chan.context.force_shutdown(false),
                                        $self.get_channel_update_for_broadcast(&$chan).ok()));
@@ -1885,16 +1893,42 @@ macro_rules! handle_new_monitor_update {
                                res
                        },
                        ChannelMonitorUpdateStatus::Completed => {
-                               $chan.complete_one_mon_update($update_id);
-                               if $chan.no_monitor_updates_pending() {
-                                       handle_monitor_update_completion!($self, $update_id, $peer_state_lock, $peer_state, $per_peer_state_lock, $chan);
-                               }
-                               Ok(())
+                               $completed;
+                               Ok(true)
                        },
                }
        } };
-       ($self: ident, $update_res: expr, $update_id: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan_entry: expr) => {
-               handle_new_monitor_update!($self, $update_res, $update_id, $peer_state_lock, $peer_state, $per_peer_state_lock, $chan_entry.get_mut(), MANUALLY_REMOVING, $chan_entry.remove_entry())
+       ($self: ident, $update_res: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan: expr, MANUALLY_REMOVING_INITIAL_MONITOR, $remove: expr) => {
+               handle_new_monitor_update!($self, $update_res, $peer_state_lock, $peer_state,
+                       $per_peer_state_lock, $chan, _internal, $remove,
+                       handle_monitor_update_completion!($self, $peer_state_lock, $peer_state, $per_peer_state_lock, $chan))
+       };
+       ($self: ident, $update_res: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan_entry: expr, INITIAL_MONITOR) => {
+               handle_new_monitor_update!($self, $update_res, $peer_state_lock, $peer_state, $per_peer_state_lock, $chan_entry.get_mut(), MANUALLY_REMOVING_INITIAL_MONITOR, $chan_entry.remove_entry())
+       };
+       ($self: ident, $funding_txo: expr, $update: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan: expr, MANUALLY_REMOVING, $remove: expr) => { {
+               let in_flight_updates = $peer_state.in_flight_monitor_updates.entry($funding_txo)
+                       .or_insert_with(Vec::new);
+               // During startup, we push monitor updates as background events through to here in
+               // order to replay updates that were in-flight when we shut down. Thus, we have to
+               // filter for uniqueness here.
+               let idx = in_flight_updates.iter().position(|upd| upd == &$update)
+                       .unwrap_or_else(|| {
+                               in_flight_updates.push($update);
+                               in_flight_updates.len() - 1
+                       });
+               let update_res = $self.chain_monitor.update_channel($funding_txo, &in_flight_updates[idx]);
+               handle_new_monitor_update!($self, update_res, $peer_state_lock, $peer_state,
+                       $per_peer_state_lock, $chan, _internal, $remove,
+                       {
+                               let _ = in_flight_updates.remove(idx);
+                               if in_flight_updates.is_empty() && $chan.blocked_monitor_updates_pending() == 0 {
+                                       handle_monitor_update_completion!($self, $peer_state_lock, $peer_state, $per_peer_state_lock, $chan);
+                               }
+                       })
+       } };
+       ($self: ident, $funding_txo: expr, $update: expr, $peer_state_lock: expr, $peer_state: expr, $per_peer_state_lock: expr, $chan_entry: expr) => {
+               handle_new_monitor_update!($self, $funding_txo, $update, $peer_state_lock, $peer_state, $per_peer_state_lock, $chan_entry.get_mut(), MANUALLY_REMOVING, $chan_entry.remove_entry())
        }
 }
 
@@ -2309,9 +2343,8 @@ where
 
                                        // Update the monitor with the shutdown script if necessary.
                                        if let Some(monitor_update) = monitor_update_opt.take() {
-                                               let update_id = monitor_update.update_id;
-                                               let update_res = self.chain_monitor.update_channel(funding_txo_opt.unwrap(), monitor_update);
-                                               break handle_new_monitor_update!(self, update_res, update_id, peer_state_lock, peer_state, per_peer_state, chan_entry);
+                                               break handle_new_monitor_update!(self, funding_txo_opt.unwrap(), monitor_update,
+                                                       peer_state_lock, peer_state, per_peer_state, chan_entry).map(|_| ());
                                        }
 
                                        if chan_entry.get().is_shutdown() {
@@ -2526,9 +2559,11 @@ where
                }
        }
 
-       fn construct_recv_pending_htlc_info(&self, hop_data: msgs::OnionHopData, shared_secret: [u8; 32],
-               payment_hash: PaymentHash, amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>) -> Result<PendingHTLCInfo, ReceiveError>
-       {
+       fn construct_recv_pending_htlc_info(
+               &self, hop_data: msgs::OnionHopData, shared_secret: [u8; 32], payment_hash: PaymentHash,
+               amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>, allow_underpay: bool,
+               counterparty_skimmed_fee_msat: Option<u64>,
+       ) -> Result<PendingHTLCInfo, ReceiveError> {
                // final_incorrect_cltv_expiry
                if hop_data.outgoing_cltv_value > cltv_expiry {
                        return Err(ReceiveError {
@@ -2554,7 +2589,10 @@ where
                                msg: "The final CLTV expiry is too soon to handle",
                        });
                }
-               if hop_data.amt_to_forward > amt_msat {
+               if (!allow_underpay && hop_data.amt_to_forward > amt_msat) ||
+                       (allow_underpay && hop_data.amt_to_forward >
+                        amt_msat.saturating_add(counterparty_skimmed_fee_msat.unwrap_or(0)))
+               {
                        return Err(ReceiveError {
                                err_code: 19,
                                err_data: amt_msat.to_be_bytes().to_vec(),
@@ -2621,7 +2659,7 @@ where
                        incoming_amt_msat: Some(amt_msat),
                        outgoing_amt_msat: hop_data.amt_to_forward,
                        outgoing_cltv_value: hop_data.outgoing_cltv_value,
-                       skimmed_fee_msat: None,
+                       skimmed_fee_msat: counterparty_skimmed_fee_msat,
                })
        }
 
@@ -2841,7 +2879,7 @@ where
 
        fn construct_pending_htlc_status<'a>(
                &self, msg: &msgs::UpdateAddHTLC, shared_secret: [u8; 32], decoded_hop: onion_utils::Hop,
-               next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
+               allow_underpay: bool, next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
        ) -> PendingHTLCStatus {
                macro_rules! return_err {
                        ($msg: expr, $err_code: expr, $data: expr) => {
@@ -2859,7 +2897,9 @@ where
                match decoded_hop {
                        onion_utils::Hop::Receive(next_hop_data) => {
                                // OUR PAYMENT!
-                               match self.construct_recv_pending_htlc_info(next_hop_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry, None) {
+                               match self.construct_recv_pending_htlc_info(next_hop_data, shared_secret, msg.payment_hash,
+                                       msg.amount_msat, msg.cltv_expiry, None, allow_underpay, msg.skimmed_fee_msat)
+                               {
                                        Ok(info) => {
                                                // Note that we could obviously respond immediately with an update_fulfill_htlc
                                                // message, however that would leak that we are the recipient of this payment, so
@@ -3025,22 +3065,21 @@ where
                                                session_priv: session_priv.clone(),
                                                first_hop_htlc_msat: htlc_msat,
                                                payment_id,
-                                       }, onion_packet, &self.logger);
+                                       }, onion_packet, None, &self.logger);
                                match break_chan_entry!(self, send_res, chan) {
                                        Some(monitor_update) => {
-                                               let update_id = monitor_update.update_id;
-                                               let update_res = self.chain_monitor.update_channel(funding_txo, monitor_update);
-                                               if let Err(e) = handle_new_monitor_update!(self, update_res, update_id, peer_state_lock, peer_state, per_peer_state, chan) {
-                                                       break Err(e);
-                                               }
-                                               if update_res == ChannelMonitorUpdateStatus::InProgress {
-                                                       // Note that MonitorUpdateInProgress here indicates (per function
-                                                       // docs) that we will resend the commitment update once monitor
-                                                       // updating completes. Therefore, we must return an error
-                                                       // indicating that it is unsafe to retry the payment wholesale,
-                                                       // which we do in the send_payment check for
-                                                       // MonitorUpdateInProgress, below.
-                                                       return Err(APIError::MonitorUpdateInProgress);
+                                               match handle_new_monitor_update!(self, funding_txo, monitor_update, peer_state_lock, peer_state, per_peer_state, chan) {
+                                                       Err(e) => break Err(e),
+                                                       Ok(false) => {
+                                                               // Note that MonitorUpdateInProgress here indicates (per function
+                                                               // docs) that we will resend the commitment update once monitor
+                                                               // updating completes. Therefore, we must return an error
+                                                               // indicating that it is unsafe to retry the payment wholesale,
+                                                               // which we do in the send_payment check for
+                                                               // MonitorUpdateInProgress, below.
+                                                               return Err(APIError::MonitorUpdateInProgress);
+                                                       },
+                                                       Ok(true) => {},
                                                }
                                        },
                                        None => { },
@@ -3675,7 +3714,10 @@ where
                                                                                                };
                                                                                                match next_hop {
                                                                                                        onion_utils::Hop::Receive(hop_data) => {
-                                                                                                               match self.construct_recv_pending_htlc_info(hop_data, incoming_shared_secret, payment_hash, outgoing_amt_msat, outgoing_cltv_value, Some(phantom_shared_secret)) {
+                                                                                                               match self.construct_recv_pending_htlc_info(hop_data,
+                                                                                                                       incoming_shared_secret, payment_hash, outgoing_amt_msat,
+                                                                                                                       outgoing_cltv_value, Some(phantom_shared_secret), false, None)
+                                                                                                               {
                                                                                                                        Ok(info) => phantom_receives.push((prev_short_channel_id, prev_funding_outpoint, prev_user_channel_id, vec![(info, prev_htlc_id)])),
                                                                                                                        Err(ReceiveError { err_code, err_data, msg }) => failed_payment!(msg, err_code, err_data, Some(phantom_shared_secret))
                                                                                                                }
@@ -3726,7 +3768,7 @@ where
                                                                                prev_short_channel_id, prev_htlc_id, prev_funding_outpoint, prev_user_channel_id: _,
                                                                                forward_info: PendingHTLCInfo {
                                                                                        incoming_shared_secret, payment_hash, outgoing_amt_msat, outgoing_cltv_value,
-                                                                                       routing: PendingHTLCRouting::Forward { onion_packet, .. }, ..
+                                                                                       routing: PendingHTLCRouting::Forward { onion_packet, .. }, skimmed_fee_msat, ..
                                                                                },
                                                                        }) => {
                                                                                log_trace!(self.logger, "Adding HTLC from short id {} with payment_hash {} to channel with short id {} after delay", prev_short_channel_id, log_bytes!(payment_hash.0), short_chan_id);
@@ -3740,7 +3782,7 @@ where
                                                                                });
                                                                                if let Err(e) = chan.get_mut().queue_add_htlc(outgoing_amt_msat,
                                                                                        payment_hash, outgoing_cltv_value, htlc_source.clone(),
-                                                                                       onion_packet, &self.logger)
+                                                                                       onion_packet, skimmed_fee_msat, &self.logger)
                                                                                {
                                                                                        if let ChannelError::Ignore(msg) = e {
                                                                                                log_trace!(self.logger, "Failed to forward HTLC with payment_hash {}: {}", log_bytes!(payment_hash.0), msg);
@@ -3923,11 +3965,16 @@ where
                                                                                        htlcs.push(claimable_htlc);
                                                                                        let amount_msat = htlcs.iter().map(|htlc| htlc.value).sum();
                                                                                        htlcs.iter_mut().for_each(|htlc| htlc.total_value_received = Some(amount_msat));
+                                                                                       let counterparty_skimmed_fee_msat = htlcs.iter()
+                                                                                               .map(|htlc| htlc.counterparty_skimmed_fee_msat.unwrap_or(0)).sum();
+                                                                                       debug_assert!(total_value.saturating_sub(amount_msat) <=
+                                                                                               counterparty_skimmed_fee_msat);
                                                                                        new_events.push_back((events::Event::PaymentClaimable {
                                                                                                receiver_node_id: Some(receiver_node_id),
                                                                                                payment_hash,
                                                                                                purpose: $purpose,
                                                                                                amount_msat,
+                                                                                               counterparty_skimmed_fee_msat,
                                                                                                via_channel_id: Some(prev_channel_id),
                                                                                                via_user_channel_id: Some(prev_user_channel_id),
                                                                                                claim_deadline: Some(earliest_expiry - HTLC_FAIL_BACK_BUFFER),
@@ -4067,8 +4114,7 @@ where
                                        let _ = self.chain_monitor.update_channel(funding_txo, &update);
                                },
                                BackgroundEvent::MonitorUpdateRegeneratedOnStartup { counterparty_node_id, funding_txo, update } => {
-                                       let update_res = self.chain_monitor.update_channel(funding_txo, &update);
-
+                                       let mut updated_chan = false;
                                        let res = {
                                                let per_peer_state = self.per_peer_state.read().unwrap();
                                                if let Some(peer_state_mutex) = per_peer_state.get(&counterparty_node_id) {
@@ -4076,12 +4122,18 @@ where
                                                        let peer_state = &mut *peer_state_lock;
                                                        match peer_state.channel_by_id.entry(funding_txo.to_channel_id()) {
                                                                hash_map::Entry::Occupied(mut chan) => {
-                                                                       handle_new_monitor_update!(self, update_res, update.update_id, peer_state_lock, peer_state, per_peer_state, chan)
+                                                                       updated_chan = true;
+                                                                       handle_new_monitor_update!(self, funding_txo, update.clone(),
+                                                                               peer_state_lock, peer_state, per_peer_state, chan).map(|_| ())
                                                                },
                                                                hash_map::Entry::Vacant(_) => Ok(()),
                                                        }
                                                } else { Ok(()) }
                                        };
+                                       if !updated_chan {
+                                               // TODO: Track this as in-flight even though the channel is closed.
+                                               let _ = self.chain_monitor.update_channel(funding_txo, &update);
+                                       }
                                        // TODO: If this channel has since closed, we're likely providing a payment
                                        // preimage update, which we must ensure is durable! We currently don't,
                                        // however, ensure that.
@@ -4662,9 +4714,7 @@ where
                                                                log_bytes!(chan_id), action);
                                                        peer_state.monitor_update_blocked_actions.entry(chan_id).or_insert(Vec::new()).push(action);
                                                }
-                                               let update_id = monitor_update.update_id;
-                                               let update_res = self.chain_monitor.update_channel(prev_hop.outpoint, monitor_update);
-                                               let res = handle_new_monitor_update!(self, update_res, update_id, peer_state_lock,
+                                               let res = handle_new_monitor_update!(self, prev_hop.outpoint, monitor_update, peer_state_lock,
                                                        peer_state, per_peer_state, chan);
                                                if let Err(e) = res {
                                                        // TODO: This is a *critical* error - we probably updated the outbound edge
@@ -4872,12 +4922,18 @@ where
                                hash_map::Entry::Vacant(_) => return,
                        }
                };
-               log_trace!(self.logger, "ChannelMonitor updated to {}. Current highest is {}",
-                       highest_applied_update_id, channel.get().context.get_latest_monitor_update_id());
+               let remaining_in_flight =
+                       if let Some(pending) = peer_state.in_flight_monitor_updates.get_mut(funding_txo) {
+                               pending.retain(|upd| upd.update_id > highest_applied_update_id);
+                               pending.len()
+                       } else { 0 };
+               log_trace!(self.logger, "ChannelMonitor updated to {}. Current highest is {}. {} pending in-flight updates.",
+                       highest_applied_update_id, channel.get().context.get_latest_monitor_update_id(),
+                       remaining_in_flight);
                if !channel.get().is_awaiting_monitor_update() || channel.get().context.get_latest_monitor_update_id() != highest_applied_update_id {
                        return;
                }
-               handle_monitor_update_completion!(self, highest_applied_update_id, peer_state_lock, peer_state, per_peer_state, channel.get_mut());
+               handle_monitor_update_completion!(self, peer_state_lock, peer_state, per_peer_state, channel.get_mut());
        }
 
        /// Accepts a request to open a channel after a [`Event::OpenChannelRequest`].
@@ -5088,9 +5144,13 @@ where
                        return Err(MsgHandleErrInternal::send_err_msg_no_close("temporary_channel_id collision for the same peer!".to_owned(), msg.temporary_channel_id.clone()))
                } else {
                        if !self.default_configuration.manually_accept_inbound_channels {
-                               if channel.context.get_channel_type().requires_zero_conf() {
+                               let channel_type = channel.context.get_channel_type();
+                               if channel_type.requires_zero_conf() {
                                        return Err(MsgHandleErrInternal::send_err_msg_no_close("No zero confirmation channels accepted".to_owned(), msg.temporary_channel_id.clone()));
                                }
+                               if channel_type.requires_anchors_zero_fee_htlc_tx() {
+                                       return Err(MsgHandleErrInternal::send_err_msg_no_close("No channels with anchor outputs accepted".to_owned(), msg.temporary_channel_id.clone()));
+                               }
                                peer_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannel {
                                        node_id: counterparty_node_id.clone(),
                                        msg: channel.accept_inbound_channel(user_channel_id),
@@ -5200,8 +5260,9 @@ where
                                let monitor_res = self.chain_monitor.watch_channel(monitor.get_funding_txo().0, monitor);
 
                                let chan = e.insert(chan);
-                               let mut res = handle_new_monitor_update!(self, monitor_res, 0, peer_state_lock, peer_state,
-                                       per_peer_state, chan, MANUALLY_REMOVING, { peer_state.channel_by_id.remove(&new_channel_id) });
+                               let mut res = handle_new_monitor_update!(self, monitor_res, peer_state_lock, peer_state,
+                                       per_peer_state, chan, MANUALLY_REMOVING_INITIAL_MONITOR,
+                                       { peer_state.channel_by_id.remove(&new_channel_id) });
 
                                // Note that we reply with the new channel_id in error messages if we gave up on the
                                // channel, not the temporary_channel_id. This is compatible with ourselves, but the
@@ -5213,7 +5274,7 @@ where
                                if let Err(MsgHandleErrInternal { shutdown_finish: Some((res, _)), .. }) = &mut res {
                                        res.0 = None;
                                }
-                               res
+                               res.map(|_| ())
                        }
                }
        }
@@ -5234,7 +5295,7 @@ where
                                let monitor = try_chan_entry!(self,
                                        chan.get_mut().funding_signed(&msg, best_block, &self.signer_provider, &self.logger), chan);
                                let update_res = self.chain_monitor.watch_channel(chan.get().context.get_funding_txo().unwrap(), monitor);
-                               let mut res = handle_new_monitor_update!(self, update_res, 0, peer_state_lock, peer_state, per_peer_state, chan);
+                               let mut res = handle_new_monitor_update!(self, update_res, peer_state_lock, peer_state, per_peer_state, chan, INITIAL_MONITOR);
                                if let Err(MsgHandleErrInternal { ref mut shutdown_finish, .. }) = res {
                                        // We weren't able to watch the channel to begin with, so no updates should be made on
                                        // it. Previously, full_stack_target found an (unreachable) panic when the
@@ -5243,7 +5304,7 @@ where
                                                shutdown_finish.0.take();
                                        }
                                }
-                               res
+                               res.map(|_| ())
                        },
                        hash_map::Entry::Vacant(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close("Failed to find corresponding channel".to_owned(), msg.channel_id))
                }
@@ -5331,9 +5392,8 @@ where
 
                                        // Update the monitor with the shutdown script if necessary.
                                        if let Some(monitor_update) = monitor_update_opt {
-                                               let update_id = monitor_update.update_id;
-                                               let update_res = self.chain_monitor.update_channel(funding_txo_opt.unwrap(), monitor_update);
-                                               break handle_new_monitor_update!(self, update_res, update_id, peer_state_lock, peer_state, per_peer_state, chan_entry);
+                                               break handle_new_monitor_update!(self, funding_txo_opt.unwrap(), monitor_update,
+                                                       peer_state_lock, peer_state, per_peer_state, chan_entry).map(|_| ());
                                        }
                                        break Ok(());
                                },
@@ -5421,7 +5481,8 @@ where
 
                                let pending_forward_info = match decoded_hop_res {
                                        Ok((next_hop, shared_secret, next_packet_pk_opt)) =>
-                                               self.construct_pending_htlc_status(msg, shared_secret, next_hop, next_packet_pk_opt),
+                                               self.construct_pending_htlc_status(msg, shared_secret, next_hop,
+                                                       chan.get().context.config().accept_underpaying_htlcs, next_packet_pk_opt),
                                        Err(e) => PendingHTLCStatus::Fail(e)
                                };
                                let create_pending_htlc_status = |chan: &Channel<<SP::Target as SignerProvider>::Signer>, pending_forward_info: PendingHTLCStatus, error_code: u16| {
@@ -5528,10 +5589,8 @@ where
                                let funding_txo = chan.get().context.get_funding_txo();
                                let monitor_update_opt = try_chan_entry!(self, chan.get_mut().commitment_signed(&msg, &self.logger), chan);
                                if let Some(monitor_update) = monitor_update_opt {
-                                       let update_res = self.chain_monitor.update_channel(funding_txo.unwrap(), monitor_update);
-                                       let update_id = monitor_update.update_id;
-                                       handle_new_monitor_update!(self, update_res, update_id, peer_state_lock,
-                                               peer_state, per_peer_state, chan)
+                                       handle_new_monitor_update!(self, funding_txo.unwrap(), monitor_update, peer_state_lock,
+                                               peer_state, per_peer_state, chan).map(|_| ())
                                } else { Ok(()) }
                        },
                        hash_map::Entry::Vacant(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close(format!("Got a message for a channel from the wrong node! No such channel for the passed counterparty_node_id {}", counterparty_node_id), msg.channel_id))
@@ -5667,10 +5726,8 @@ where
                                        let funding_txo = chan.get().context.get_funding_txo();
                                        let (htlcs_to_fail, monitor_update_opt) = try_chan_entry!(self, chan.get_mut().revoke_and_ack(&msg, &self.logger), chan);
                                        let res = if let Some(monitor_update) = monitor_update_opt {
-                                               let update_res = self.chain_monitor.update_channel(funding_txo.unwrap(), monitor_update);
-                                               let update_id = monitor_update.update_id;
-                                               handle_new_monitor_update!(self, update_res, update_id,
-                                                       peer_state_lock, peer_state, per_peer_state, chan)
+                                               handle_new_monitor_update!(self, funding_txo.unwrap(), monitor_update,
+                                                       peer_state_lock, peer_state, per_peer_state, chan).map(|_| ())
                                        } else { Ok(()) };
                                        (htlcs_to_fail, res)
                                },
@@ -5945,11 +6002,8 @@ where
                                                if let Some(monitor_update) = monitor_opt {
                                                        has_monitor_update = true;
 
-                                                       let update_res = self.chain_monitor.update_channel(
-                                                               funding_txo.expect("channel is live"), monitor_update);
-                                                       let update_id = monitor_update.update_id;
                                                        let channel_id: [u8; 32] = *channel_id;
-                                                       let res = handle_new_monitor_update!(self, update_res, update_id,
+                                                       let res = handle_new_monitor_update!(self, funding_txo.unwrap(), monitor_update,
                                                                peer_state_lock, peer_state, per_peer_state, chan, MANUALLY_REMOVING,
                                                                peer_state.channel_by_id.remove(&channel_id));
                                                        if res.is_err() {
@@ -6059,37 +6113,6 @@ where
                }
        }
 
-       fn set_payment_hash_secret_map(&self, payment_hash: PaymentHash, payment_preimage: Option<PaymentPreimage>, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32) -> Result<PaymentSecret, APIError> {
-               assert!(invoice_expiry_delta_secs <= 60*60*24*365); // Sadly bitcoin timestamps are u32s, so panic before 2106
-
-               if min_value_msat.is_some() && min_value_msat.unwrap() > MAX_VALUE_MSAT {
-                       return Err(APIError::APIMisuseError { err: format!("min_value_msat of {} greater than total 21 million bitcoin supply", min_value_msat.unwrap()) });
-               }
-
-               let payment_secret = PaymentSecret(self.entropy_source.get_secure_random_bytes());
-
-               let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
-               let mut payment_secrets = self.pending_inbound_payments.lock().unwrap();
-               match payment_secrets.entry(payment_hash) {
-                       hash_map::Entry::Vacant(e) => {
-                               e.insert(PendingInboundPayment {
-                                       payment_secret, min_value_msat, payment_preimage,
-                                       user_payment_id: 0, // For compatibility with version 0.0.103 and earlier
-                                       // We assume that highest_seen_timestamp is pretty close to the current time -
-                                       // it's updated when we receive a new block with the maximum time we've seen in
-                                       // a header. It should never be more than two hours in the future.
-                                       // Thus, we add two hours here as a buffer to ensure we absolutely
-                                       // never fail a payment too early.
-                                       // Note that we assume that received blocks have reasonably up-to-date
-                                       // timestamps.
-                                       expiry_time: self.highest_seen_timestamp.load(Ordering::Acquire) as u64 + invoice_expiry_delta_secs as u64 + 7200,
-                               });
-                       },
-                       hash_map::Entry::Occupied(_) => return Err(APIError::APIMisuseError { err: "Duplicate payment hash".to_owned() }),
-               }
-               Ok(payment_secret)
-       }
-
        /// Gets a payment secret and payment hash for use in an invoice given to a third party wishing
        /// to pay us.
        ///
@@ -6129,23 +6152,6 @@ where
                        min_final_cltv_expiry_delta)
        }
 
-       /// Legacy version of [`create_inbound_payment`]. Use this method if you wish to share
-       /// serialized state with LDK node(s) running 0.0.103 and earlier.
-       ///
-       /// May panic if `invoice_expiry_delta_secs` is greater than one year.
-       ///
-       /// # Note
-       /// This method is deprecated and will be removed soon.
-       ///
-       /// [`create_inbound_payment`]: Self::create_inbound_payment
-       #[deprecated]
-       pub fn create_inbound_payment_legacy(&self, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32) -> Result<(PaymentHash, PaymentSecret), APIError> {
-               let payment_preimage = PaymentPreimage(self.entropy_source.get_secure_random_bytes());
-               let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
-               let payment_secret = self.set_payment_hash_secret_map(payment_hash, Some(payment_preimage), min_value_msat, invoice_expiry_delta_secs)?;
-               Ok((payment_hash, payment_secret))
-       }
-
        /// Gets a [`PaymentSecret`] for a given [`PaymentHash`], for which the payment preimage is
        /// stored external to LDK.
        ///
@@ -6199,20 +6205,6 @@ where
                        min_final_cltv_expiry)
        }
 
-       /// Legacy version of [`create_inbound_payment_for_hash`]. Use this method if you wish to share
-       /// serialized state with LDK node(s) running 0.0.103 and earlier.
-       ///
-       /// May panic if `invoice_expiry_delta_secs` is greater than one year.
-       ///
-       /// # Note
-       /// This method is deprecated and will be removed soon.
-       ///
-       /// [`create_inbound_payment_for_hash`]: Self::create_inbound_payment_for_hash
-       #[deprecated]
-       pub fn create_inbound_payment_for_hash_legacy(&self, payment_hash: PaymentHash, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32) -> Result<PaymentSecret, APIError> {
-               self.set_payment_hash_secret_map(payment_hash, None, min_value_msat, invoice_expiry_delta_secs)
-       }
-
        /// Gets an LDK-generated payment preimage from a payment hash and payment secret that were
        /// previously returned from [`create_inbound_payment`].
        ///
@@ -6287,7 +6279,7 @@ where
                inflight_htlcs
        }
 
-       #[cfg(any(test, fuzzing, feature = "_test_utils"))]
+       #[cfg(any(test, feature = "_test_utils"))]
        pub fn get_and_clear_pending_events(&self) -> Vec<events::Event> {
                let events = core::cell::RefCell::new(Vec::new());
                let event_handler = |event: events::Event| events.borrow_mut().push(event);
@@ -6353,9 +6345,7 @@ where
                                        if let Some((monitor_update, further_update_exists)) = chan.get_mut().unblock_next_blocked_monitor_update() {
                                                log_debug!(self.logger, "Unlocking monitor updating for channel {} and updating monitor",
                                                        log_bytes!(&channel_funding_outpoint.to_channel_id()[..]));
-                                               let update_res = self.chain_monitor.update_channel(channel_funding_outpoint, monitor_update);
-                                               let update_id = monitor_update.update_id;
-                                               if let Err(e) = handle_new_monitor_update!(self, update_res, update_id,
+                                               if let Err(e) = handle_new_monitor_update!(self, channel_funding_outpoint, monitor_update,
                                                        peer_state_lck, peer_state, per_peer_state, chan)
                                                {
                                                        errors.push((e, counterparty_node_id));
@@ -7076,6 +7066,7 @@ where
                                                inbound_v1_channel_by_id: HashMap::new(),
                                                latest_features: init_msg.features.clone(),
                                                pending_msg_events: Vec::new(),
+                                               in_flight_monitor_updates: BTreeMap::new(),
                                                monitor_update_blocked_actions: BTreeMap::new(),
                                                actions_blocking_raa_monitor_updates: BTreeMap::new(),
                                                is_connected: true,
@@ -7278,7 +7269,7 @@ pub(crate) fn provided_channel_type_features(config: &UserConfig) -> ChannelType
 
 /// Fetches the set of [`InitFeatures`] flags which are provided by or required by
 /// [`ChannelManager`].
-pub fn provided_init_features(_config: &UserConfig) -> InitFeatures {
+pub fn provided_init_features(config: &UserConfig) -> InitFeatures {
        // Note that if new features are added here which other peers may (eventually) require, we
        // should also add the corresponding (optional) bit to the [`ChannelMessageHandler`] impl for
        // [`ErroringMessageHandler`].
@@ -7294,11 +7285,8 @@ pub fn provided_init_features(_config: &UserConfig) -> InitFeatures {
        features.set_channel_type_optional();
        features.set_scid_privacy_optional();
        features.set_zero_conf_optional();
-       #[cfg(anchors)]
-       { // Attributes are not allowed on if expressions on our current MSRV of 1.41.
-               if _config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx {
-                       features.set_anchors_zero_fee_htlc_tx_optional();
-               }
+       if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx {
+               features.set_anchors_zero_fee_htlc_tx_optional();
        }
        features
 }
@@ -7907,6 +7895,16 @@ where
                        pending_claiming_payments = None;
                }
 
+               let mut in_flight_monitor_updates: Option<HashMap<(&PublicKey, &OutPoint), &Vec<ChannelMonitorUpdate>>> = None;
+               for ((counterparty_id, _), peer_state) in per_peer_state.iter().zip(peer_states.iter()) {
+                       for (funding_outpoint, updates) in peer_state.in_flight_monitor_updates.iter() {
+                               if !updates.is_empty() {
+                                       if in_flight_monitor_updates.is_none() { in_flight_monitor_updates = Some(HashMap::new()); }
+                                       in_flight_monitor_updates.as_mut().unwrap().insert((counterparty_id, funding_outpoint), updates);
+                               }
+                       }
+               }
+
                write_tlv_fields!(writer, {
                        (1, pending_outbound_payments_no_retry, required),
                        (2, pending_intercepted_htlcs, option),
@@ -7917,6 +7915,7 @@ where
                        (7, self.fake_scid_rand_bytes, required),
                        (8, if events_not_backwards_compatible { Some(&*events) } else { None }, option),
                        (9, htlc_purposes, vec_type),
+                       (10, in_flight_monitor_updates, option),
                        (11, self.probing_cookie_secret, required),
                        (13, htlc_onion_fields, optional_vec),
                });
@@ -8133,7 +8132,7 @@ where
                let mut id_to_peer = HashMap::with_capacity(cmp::min(channel_count as usize, 128));
                let mut short_to_chan_info = HashMap::with_capacity(cmp::min(channel_count as usize, 128));
                let mut channel_closures = VecDeque::new();
-               let mut pending_background_events = Vec::new();
+               let mut close_background_events = Vec::new();
                for _ in 0..channel_count {
                        let mut channel: Channel<<SP::Target as SignerProvider>::Signer> = Channel::read(reader, (
                                &args.entropy_source, &args.signer_provider, best_block_height, &provided_channel_type_features(&args.default_config)
@@ -8141,17 +8140,7 @@ where
                        let funding_txo = channel.context.get_funding_txo().ok_or(DecodeError::InvalidValue)?;
                        funding_txo_set.insert(funding_txo.clone());
                        if let Some(ref mut monitor) = args.channel_monitors.get_mut(&funding_txo) {
-                               if channel.get_latest_complete_monitor_update_id() > monitor.get_latest_update_id() {
-                                       // If the channel is ahead of the monitor, return InvalidValue:
-                                       log_error!(args.logger, "A ChannelMonitor is stale compared to the current ChannelManager! This indicates a potentially-critical violation of the chain::Watch API!");
-                                       log_error!(args.logger, " The ChannelMonitor for channel {} is at update_id {} but the ChannelManager is at update_id {}.",
-                                               log_bytes!(channel.context.channel_id()), monitor.get_latest_update_id(), channel.get_latest_complete_monitor_update_id());
-                                       log_error!(args.logger, " The chain::Watch API *requires* that monitors are persisted durably before returning,");
-                                       log_error!(args.logger, " client applications must ensure that ChannelMonitor data is always available and the latest to avoid funds loss!");
-                                       log_error!(args.logger, " Without the latest ChannelMonitor we cannot continue without risking funds.");
-                                       log_error!(args.logger, " Please ensure the chain::Watch API requirements are met and file a bug report at https://github.com/lightningdevkit/rust-lightning");
-                                       return Err(DecodeError::InvalidValue);
-                               } else if channel.get_cur_holder_commitment_transaction_number() > monitor.get_cur_holder_commitment_number() ||
+                               if channel.get_cur_holder_commitment_transaction_number() > monitor.get_cur_holder_commitment_number() ||
                                                channel.get_revoked_counterparty_commitment_transaction_number() > monitor.get_min_seen_secret() ||
                                                channel.get_cur_counterparty_commitment_transaction_number() > monitor.get_cur_counterparty_commitment_number() ||
                                                channel.context.get_latest_monitor_update_id() < monitor.get_latest_update_id() {
@@ -8162,7 +8151,7 @@ where
                                                log_bytes!(channel.context.channel_id()), monitor.get_latest_update_id(), channel.context.get_latest_monitor_update_id());
                                        let (monitor_update, mut new_failed_htlcs) = channel.context.force_shutdown(true);
                                        if let Some((counterparty_node_id, funding_txo, update)) = monitor_update {
-                                               pending_background_events.push(BackgroundEvent::MonitorUpdateRegeneratedOnStartup {
+                                               close_background_events.push(BackgroundEvent::MonitorUpdateRegeneratedOnStartup {
                                                        counterparty_node_id, funding_txo, update
                                                });
                                        }
@@ -8195,7 +8184,6 @@ where
                                        log_info!(args.logger, "Successfully loaded channel {} at update_id {} against monitor at update id {}",
                                                log_bytes!(channel.context.channel_id()), channel.context.get_latest_monitor_update_id(),
                                                monitor.get_latest_update_id());
-                                       channel.complete_all_mon_updates_through(monitor.get_latest_update_id());
                                        if let Some(short_channel_id) = channel.context.get_short_channel_id() {
                                                short_to_chan_info.insert(short_channel_id, (channel.context.get_counterparty_node_id(), channel.context.channel_id()));
                                        }
@@ -8242,7 +8230,7 @@ where
                                        update_id: CLOSED_CHANNEL_UPDATE_ID,
                                        updates: vec![ChannelMonitorUpdateStep::ChannelForceClosed { should_broadcast: true }],
                                };
-                               pending_background_events.push(BackgroundEvent::ClosingMonitorUpdateRegeneratedOnStartup((*funding_txo, monitor_update)));
+                               close_background_events.push(BackgroundEvent::ClosingMonitorUpdateRegeneratedOnStartup((*funding_txo, monitor_update)));
                        }
                }
 
@@ -8271,20 +8259,27 @@ where
                        claimable_htlcs_list.push((payment_hash, previous_hops));
                }
 
-               let peer_count: u64 = Readable::read(reader)?;
-               let mut per_peer_state = HashMap::with_capacity(cmp::min(peer_count as usize, MAX_ALLOC_SIZE/mem::size_of::<(PublicKey, Mutex<PeerState<<SP::Target as SignerProvider>::Signer>>)>()));
-               for _ in 0..peer_count {
-                       let peer_pubkey = Readable::read(reader)?;
-                       let peer_state = PeerState {
-                               channel_by_id: peer_channels.remove(&peer_pubkey).unwrap_or(HashMap::new()),
+               let peer_state_from_chans = |channel_by_id| {
+                       PeerState {
+                               channel_by_id,
                                outbound_v1_channel_by_id: HashMap::new(),
                                inbound_v1_channel_by_id: HashMap::new(),
-                               latest_features: Readable::read(reader)?,
+                               latest_features: InitFeatures::empty(),
                                pending_msg_events: Vec::new(),
+                               in_flight_monitor_updates: BTreeMap::new(),
                                monitor_update_blocked_actions: BTreeMap::new(),
                                actions_blocking_raa_monitor_updates: BTreeMap::new(),
                                is_connected: false,
-                       };
+                       }
+               };
+
+               let peer_count: u64 = Readable::read(reader)?;
+               let mut per_peer_state = HashMap::with_capacity(cmp::min(peer_count as usize, MAX_ALLOC_SIZE/mem::size_of::<(PublicKey, Mutex<PeerState<<SP::Target as SignerProvider>::Signer>>)>()));
+               for _ in 0..peer_count {
+                       let peer_pubkey = Readable::read(reader)?;
+                       let peer_chans = peer_channels.remove(&peer_pubkey).unwrap_or(HashMap::new());
+                       let mut peer_state = peer_state_from_chans(peer_chans);
+                       peer_state.latest_features = Readable::read(reader)?;
                        per_peer_state.insert(peer_pubkey, Mutex::new(peer_state));
                }
 
@@ -8312,24 +8307,6 @@ where
                        }
                }
 
-               for (node_id, peer_mtx) in per_peer_state.iter() {
-                       let peer_state = peer_mtx.lock().unwrap();
-                       for (_, chan) in peer_state.channel_by_id.iter() {
-                               for update in chan.uncompleted_unblocked_mon_updates() {
-                                       if let Some(funding_txo) = chan.context.get_funding_txo() {
-                                               log_trace!(args.logger, "Replaying ChannelMonitorUpdate {} for channel {}",
-                                                       update.update_id, log_bytes!(funding_txo.to_channel_id()));
-                                               pending_background_events.push(
-                                                       BackgroundEvent::MonitorUpdateRegeneratedOnStartup {
-                                                               counterparty_node_id: *node_id, funding_txo, update: update.clone(),
-                                                       });
-                                       } else {
-                                               return Err(DecodeError::InvalidValue);
-                                       }
-                               }
-                       }
-               }
-
                let _last_node_announcement_serial: u32 = Readable::read(reader)?; // Only used < 0.0.111
                let highest_seen_timestamp: u32 = Readable::read(reader)?;
 
@@ -8366,6 +8343,7 @@ where
                let mut pending_claiming_payments = Some(HashMap::new());
                let mut monitor_update_blocked_actions_per_peer: Option<Vec<(_, BTreeMap<_, Vec<_>>)>> = Some(Vec::new());
                let mut events_override = None;
+               let mut in_flight_monitor_updates: Option<HashMap<(PublicKey, OutPoint), Vec<ChannelMonitorUpdate>>> = None;
                read_tlv_fields!(reader, {
                        (1, pending_outbound_payments_no_retry, option),
                        (2, pending_intercepted_htlcs, option),
@@ -8376,6 +8354,7 @@ where
                        (7, fake_scid_rand_bytes, option),
                        (8, events_override, option),
                        (9, claimable_htlc_purposes, vec_type),
+                       (10, in_flight_monitor_updates, option),
                        (11, probing_cookie_secret, option),
                        (13, claimable_htlc_onion_fields, optional_vec),
                });
@@ -8409,6 +8388,103 @@ where
                        retry_lock: Mutex::new(())
                };
 
+               // We have to replay (or skip, if they were completed after we wrote the `ChannelManager`)
+               // each `ChannelMonitorUpdate` in `in_flight_monitor_updates`. After doing so, we have to
+               // check that each channel we have isn't newer than the latest `ChannelMonitorUpdate`(s) we
+               // replayed, and for each monitor update we have to replay we have to ensure there's a
+               // `ChannelMonitor` for it.
+               //
+               // In order to do so we first walk all of our live channels (so that we can check their
+               // state immediately after doing the update replays, when we have the `update_id`s
+               // available) and then walk any remaining in-flight updates.
+               //
+               // Because the actual handling of the in-flight updates is the same, it's macro'ized here:
+               let mut pending_background_events = Vec::new();
+               macro_rules! handle_in_flight_updates {
+                       ($counterparty_node_id: expr, $chan_in_flight_upds: expr, $funding_txo: expr,
+                        $monitor: expr, $peer_state: expr, $channel_info_log: expr
+                       ) => { {
+                               let mut max_in_flight_update_id = 0;
+                               $chan_in_flight_upds.retain(|upd| upd.update_id > $monitor.get_latest_update_id());
+                               for update in $chan_in_flight_upds.iter() {
+                                       log_trace!(args.logger, "Replaying ChannelMonitorUpdate {} for {}channel {}",
+                                               update.update_id, $channel_info_log, log_bytes!($funding_txo.to_channel_id()));
+                                       max_in_flight_update_id = cmp::max(max_in_flight_update_id, update.update_id);
+                                       pending_background_events.push(
+                                               BackgroundEvent::MonitorUpdateRegeneratedOnStartup {
+                                                       counterparty_node_id: $counterparty_node_id,
+                                                       funding_txo: $funding_txo,
+                                                       update: update.clone(),
+                                               });
+                               }
+                               if $peer_state.in_flight_monitor_updates.insert($funding_txo, $chan_in_flight_upds).is_some() {
+                                       log_error!(args.logger, "Duplicate in-flight monitor update set for the same channel!");
+                                       return Err(DecodeError::InvalidValue);
+                               }
+                               max_in_flight_update_id
+                       } }
+               }
+
+               for (counterparty_id, peer_state_mtx) in per_peer_state.iter_mut() {
+                       let mut peer_state_lock = peer_state_mtx.lock().unwrap();
+                       let peer_state = &mut *peer_state_lock;
+                       for (_, chan) in peer_state.channel_by_id.iter() {
+                               // Channels that were persisted have to be funded, otherwise they should have been
+                               // discarded.
+                               let funding_txo = chan.context.get_funding_txo().ok_or(DecodeError::InvalidValue)?;
+                               let monitor = args.channel_monitors.get(&funding_txo)
+                                       .expect("We already checked for monitor presence when loading channels");
+                               let mut max_in_flight_update_id = monitor.get_latest_update_id();
+                               if let Some(in_flight_upds) = &mut in_flight_monitor_updates {
+                                       if let Some(mut chan_in_flight_upds) = in_flight_upds.remove(&(*counterparty_id, funding_txo)) {
+                                               max_in_flight_update_id = cmp::max(max_in_flight_update_id,
+                                                       handle_in_flight_updates!(*counterparty_id, chan_in_flight_upds,
+                                                               funding_txo, monitor, peer_state, ""));
+                                       }
+                               }
+                               if chan.get_latest_unblocked_monitor_update_id() > max_in_flight_update_id {
+                                       // If the channel is ahead of the monitor, return InvalidValue:
+                                       log_error!(args.logger, "A ChannelMonitor is stale compared to the current ChannelManager! This indicates a potentially-critical violation of the chain::Watch API!");
+                                       log_error!(args.logger, " The ChannelMonitor for channel {} is at update_id {} with update_id through {} in-flight",
+                                               log_bytes!(chan.context.channel_id()), monitor.get_latest_update_id(), max_in_flight_update_id);
+                                       log_error!(args.logger, " but the ChannelManager is at update_id {}.", chan.get_latest_unblocked_monitor_update_id());
+                                       log_error!(args.logger, " The chain::Watch API *requires* that monitors are persisted durably before returning,");
+                                       log_error!(args.logger, " client applications must ensure that ChannelMonitor data is always available and the latest to avoid funds loss!");
+                                       log_error!(args.logger, " Without the latest ChannelMonitor we cannot continue without risking funds.");
+                                       log_error!(args.logger, " Please ensure the chain::Watch API requirements are met and file a bug report at https://github.com/lightningdevkit/rust-lightning");
+                                       return Err(DecodeError::InvalidValue);
+                               }
+                       }
+               }
+
+               if let Some(in_flight_upds) = in_flight_monitor_updates {
+                       for ((counterparty_id, funding_txo), mut chan_in_flight_updates) in in_flight_upds {
+                               if let Some(monitor) = args.channel_monitors.get(&funding_txo) {
+                                       // Now that we've removed all the in-flight monitor updates for channels that are
+                                       // still open, we need to replay any monitor updates that are for closed channels,
+                                       // creating the neccessary peer_state entries as we go.
+                                       let peer_state_mutex = per_peer_state.entry(counterparty_id).or_insert_with(|| {
+                                               Mutex::new(peer_state_from_chans(HashMap::new()))
+                                       });
+                                       let mut peer_state = peer_state_mutex.lock().unwrap();
+                                       handle_in_flight_updates!(counterparty_id, chan_in_flight_updates,
+                                               funding_txo, monitor, peer_state, "closed ");
+                               } else {
+                                       log_error!(args.logger, "A ChannelMonitor is missing even though we have in-flight updates for it! This indicates a potentially-critical violation of the chain::Watch API!");
+                                       log_error!(args.logger, " The ChannelMonitor for channel {} is missing.",
+                                               log_bytes!(funding_txo.to_channel_id()));
+                                       log_error!(args.logger, " The chain::Watch API *requires* that monitors are persisted durably before returning,");
+                                       log_error!(args.logger, " client applications must ensure that ChannelMonitor data is always available and the latest to avoid funds loss!");
+                                       log_error!(args.logger, " Without the latest ChannelMonitor we cannot continue without risking funds.");
+                                       log_error!(args.logger, " Please ensure the chain::Watch API requirements are met and file a bug report at https://github.com/lightningdevkit/rust-lightning");
+                                       return Err(DecodeError::InvalidValue);
+                               }
+                       }
+               }
+
+               // Note that we have to do the above replays before we push new monitor updates.
+               pending_background_events.append(&mut close_background_events);
+
                {
                        // If we're tracking pending payments, ensure we haven't lost any by looking at the
                        // ChannelMonitor data for any channels for which we do not have authorative state
@@ -8781,7 +8857,7 @@ mod tests {
        use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
        use crate::ln::channelmanager::{inbound_payment, PaymentId, PaymentSendFailure, RecipientOnionFields, InterceptId};
        use crate::ln::functional_test_utils::*;
-       use crate::ln::msgs;
+       use crate::ln::msgs::{self, ErrorAction};
        use crate::ln::msgs::ChannelMessageHandler;
        use crate::routing::router::{PaymentParameters, RouteParameters, find_route};
        use crate::util::errors::APIError;
@@ -9733,7 +9809,94 @@ mod tests {
                get_event_msg!(nodes[1], MessageSendEvent::SendAcceptChannel, last_random_pk);
        }
 
-       #[cfg(anchors)]
+       #[test]
+       fn reject_excessively_underpaying_htlcs() {
+               let chanmon_cfg = create_chanmon_cfgs(1);
+               let node_cfg = create_node_cfgs(1, &chanmon_cfg);
+               let node_chanmgr = create_node_chanmgrs(1, &node_cfg, &[None]);
+               let node = create_network(1, &node_cfg, &node_chanmgr);
+               let sender_intended_amt_msat = 100;
+               let extra_fee_msat = 10;
+               let hop_data = msgs::OnionHopData {
+                       amt_to_forward: 100,
+                       outgoing_cltv_value: 42,
+                       format: msgs::OnionHopDataFormat::FinalNode {
+                               keysend_preimage: None,
+                               payment_metadata: None,
+                               payment_data: Some(msgs::FinalOnionHopData {
+                                       payment_secret: PaymentSecret([0; 32]), total_msat: sender_intended_amt_msat,
+                               }),
+                       }
+               };
+               // Check that if the amount we received + the penultimate hop extra fee is less than the sender
+               // intended amount, we fail the payment.
+               if let Err(crate::ln::channelmanager::ReceiveError { err_code, .. }) =
+                       node[0].node.construct_recv_pending_htlc_info(hop_data, [0; 32], PaymentHash([0; 32]),
+                               sender_intended_amt_msat - extra_fee_msat - 1, 42, None, true, Some(extra_fee_msat))
+               {
+                       assert_eq!(err_code, 19);
+               } else { panic!(); }
+
+               // If amt_received + extra_fee is equal to the sender intended amount, we're fine.
+               let hop_data = msgs::OnionHopData { // This is the same hop_data as above, OnionHopData doesn't implement Clone
+                       amt_to_forward: 100,
+                       outgoing_cltv_value: 42,
+                       format: msgs::OnionHopDataFormat::FinalNode {
+                               keysend_preimage: None,
+                               payment_metadata: None,
+                               payment_data: Some(msgs::FinalOnionHopData {
+                                       payment_secret: PaymentSecret([0; 32]), total_msat: sender_intended_amt_msat,
+                               }),
+                       }
+               };
+               assert!(node[0].node.construct_recv_pending_htlc_info(hop_data, [0; 32], PaymentHash([0; 32]),
+                       sender_intended_amt_msat - extra_fee_msat, 42, None, true, Some(extra_fee_msat)).is_ok());
+       }
+
+       #[test]
+       fn test_inbound_anchors_manual_acceptance() {
+               // Tests that we properly limit inbound channels when we have the manual-channel-acceptance
+               // flag set and (sometimes) accept channels as 0conf.
+               let mut anchors_cfg = test_default_channel_config();
+               anchors_cfg.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = true;
+
+               let mut anchors_manual_accept_cfg = anchors_cfg.clone();
+               anchors_manual_accept_cfg.manually_accept_inbound_channels = true;
+
+               let chanmon_cfgs = create_chanmon_cfgs(3);
+               let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
+               let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs,
+                       &[Some(anchors_cfg.clone()), Some(anchors_cfg.clone()), Some(anchors_manual_accept_cfg.clone())]);
+               let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
+
+               nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), 100_000, 0, 42, None).unwrap();
+               let open_channel_msg = get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, nodes[1].node.get_our_node_id());
+
+               nodes[1].node.handle_open_channel(&nodes[0].node.get_our_node_id(), &open_channel_msg);
+               assert!(nodes[1].node.get_and_clear_pending_events().is_empty());
+               let msg_events = nodes[1].node.get_and_clear_pending_msg_events();
+               match &msg_events[0] {
+                       MessageSendEvent::HandleError { node_id, action } => {
+                               assert_eq!(*node_id, nodes[0].node.get_our_node_id());
+                               match action {
+                                       ErrorAction::SendErrorMessage { msg } =>
+                                               assert_eq!(msg.data, "No channels with anchor outputs accepted".to_owned()),
+                                       _ => panic!("Unexpected error action"),
+                               }
+                       }
+                       _ => panic!("Unexpected event"),
+               }
+
+               nodes[2].node.handle_open_channel(&nodes[0].node.get_our_node_id(), &open_channel_msg);
+               let events = nodes[2].node.get_and_clear_pending_events();
+               match events[0] {
+                       Event::OpenChannelRequest { temporary_channel_id, .. } =>
+                               nodes[2].node.accept_inbound_channel(&temporary_channel_id, &nodes[0].node.get_our_node_id(), 23).unwrap(),
+                       _ => panic!("Unexpected event"),
+               }
+               get_event_msg!(nodes[2], MessageSendEvent::SendAcceptChannel, nodes[0].node.get_our_node_id());
+       }
+
        #[test]
        fn test_anchors_zero_fee_htlc_tx_fallback() {
                // Tests that if both nodes support anchors, but the remote node does not want to accept