Consider channels "live" even if they are awaiting a monitor update
[rust-lightning] / lightning / src / ln / channel.rs
index 413dc8313a6c5d18c73b92f74c5ee9d685c44dda..2672511115ef6fd9ae159e1572fa5e953d9a1308 100644 (file)
@@ -15,6 +15,7 @@ use bitcoin::consensus::encode;
 
 use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
+use bitcoin::hashes::sha256d::Hash as Sha256d;
 use bitcoin::hash_types::{Txid, BlockHash, WPubkeyHash};
 
 use bitcoin::secp256k1::key::{PublicKey,SecretKey};
@@ -39,9 +40,9 @@ use util::errors::APIError;
 use util::config::{UserConfig,ChannelConfig};
 use util::scid_utils::scid_from_parts;
 
-use std;
-use std::{cmp,mem,fmt};
-use std::ops::Deref;
+use prelude::*;
+use core::{cmp,mem,fmt};
+use core::ops::Deref;
 #[cfg(any(test, feature = "fuzztarget"))]
 use std::sync::Mutex;
 use bitcoin::hashes::hex::ToHex;
@@ -248,18 +249,21 @@ const MULTI_STATE_FLAGS: u32 = BOTH_SIDES_SHUTDOWN_MASK | ChannelState::PeerDisc
 
 pub const INITIAL_COMMITMENT_NUMBER: u64 = (1 << 48) - 1;
 
-/// Liveness is called to fluctuate given peer disconnecton/monitor failures/closing.
-/// If channel is public, network should have a liveness view announced by us on a
-/// best-effort, which means we may filter out some status transitions to avoid spam.
-/// See further timer_tick_occurred.
-#[derive(PartialEq)]
-enum UpdateStatus {
-       /// Status has been gossiped.
-       Fresh,
-       /// Status has been changed.
-       DisabledMarked,
-       /// Status has been marked to be gossiped at next flush
+/// The "channel disabled" bit in channel_update must be set based on whether we are connected to
+/// our counterparty or not. However, we don't want to announce updates right away to avoid
+/// spamming the network with updates if the connection is flapping. Instead, we "stage" updates to
+/// our channel_update message and track the current state here.
+/// See implementation at [`super::channelmanager::ChannelManager::timer_tick_occurred`].
+#[derive(Clone, Copy, PartialEq)]
+pub(super) enum ChannelUpdateStatus {
+       /// We've announced the channel as enabled and are connected to our peer.
+       Enabled,
+       /// Our channel is no longer live, but we haven't announced the channel as disabled yet.
        DisabledStaged,
+       /// Our channel is live again, but we haven't announced the channel as enabled yet.
+       EnabledStaged,
+       /// We've announced the channel as disabled.
+       Disabled,
 }
 
 /// An enum indicating whether the local or remote side offered a given HTLC.
@@ -416,7 +420,11 @@ pub(super) struct Channel<Signer: Sign> {
 
        commitment_secrets: CounterpartyCommitmentSecrets,
 
-       network_sync: UpdateStatus,
+       channel_update_status: ChannelUpdateStatus,
+
+       /// Our counterparty's channel_announcement signatures provided in announcement_signatures.
+       /// This can be used to rebroadcast the channel_announcement message later.
+       announcement_sigs: Option<(Signature, Signature)>,
 
        // We save these values so we can make sure `next_local_commit_tx_fee_msat` and
        // `next_remote_commit_tx_fee_msat` properly predict what the next commitment transaction fee will
@@ -617,7 +625,9 @@ impl<Signer: Sign> Channel<Signer> {
 
                        commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
-                       network_sync: UpdateStatus::Fresh,
+                       channel_update_status: ChannelUpdateStatus::Enabled,
+
+                       announcement_sigs: None,
 
                        #[cfg(any(test, feature = "fuzztarget"))]
                        next_local_commitment_tx_fee_info_cached: Mutex::new(None),
@@ -858,7 +868,9 @@ impl<Signer: Sign> Channel<Signer> {
 
                        commitment_secrets: CounterpartyCommitmentSecrets::new(),
 
-                       network_sync: UpdateStatus::Fresh,
+                       channel_update_status: ChannelUpdateStatus::Enabled,
+
+                       announcement_sigs: None,
 
                        #[cfg(any(test, feature = "fuzztarget"))]
                        next_local_commitment_tx_fee_info_cached: Mutex::new(None),
@@ -1217,7 +1229,7 @@ impl<Signer: Sign> Channel<Signer> {
                // on-chain ChannelsMonitors during block rescan. Ideally we'd figure out a way to drop
                // these, but for now we just have to treat them as normal.
 
-               let mut pending_idx = std::usize::MAX;
+               let mut pending_idx = core::usize::MAX;
                for (idx, htlc) in self.pending_inbound_htlcs.iter().enumerate() {
                        if htlc.htlc_id == htlc_id_arg {
                                assert_eq!(htlc.payment_hash, payment_hash_calc);
@@ -1240,7 +1252,7 @@ impl<Signer: Sign> Channel<Signer> {
                                break;
                        }
                }
-               if pending_idx == std::usize::MAX {
+               if pending_idx == core::usize::MAX {
                        return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
                }
 
@@ -1329,7 +1341,7 @@ impl<Signer: Sign> Channel<Signer> {
        ///
        /// Note that it is still possible to hit these assertions in case we find a preimage on-chain
        /// but then have a reorg which settles on an HTLC-failure on chain.
-       pub fn get_update_fail_htlc(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket) -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> {
+       pub fn get_update_fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, logger: &L) -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> where L::Target: Logger {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        panic!("Was asked to fail an HTLC when channel was not in an operational state");
                }
@@ -1339,7 +1351,7 @@ impl<Signer: Sign> Channel<Signer> {
                // on-chain ChannelsMonitors during block rescan. Ideally we'd figure out a way to drop
                // these, but for now we just have to treat them as normal.
 
-               let mut pending_idx = std::usize::MAX;
+               let mut pending_idx = core::usize::MAX;
                for (idx, htlc) in self.pending_inbound_htlcs.iter().enumerate() {
                        if htlc.htlc_id == htlc_id_arg {
                                match htlc.state {
@@ -1356,7 +1368,7 @@ impl<Signer: Sign> Channel<Signer> {
                                pending_idx = idx;
                        }
                }
-               if pending_idx == std::usize::MAX {
+               if pending_idx == core::usize::MAX {
                        return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
                }
 
@@ -1379,6 +1391,7 @@ impl<Signer: Sign> Channel<Signer> {
                                        _ => {}
                                }
                        }
+                       log_trace!(logger, "Placing failure for HTLC ID {} in holding cell", htlc_id_arg);
                        self.holding_cell_htlc_updates.push(HTLCUpdateAwaitingACK::FailHTLC {
                                htlc_id: htlc_id_arg,
                                err_packet,
@@ -1386,6 +1399,7 @@ impl<Signer: Sign> Channel<Signer> {
                        return Ok(None);
                }
 
+               log_trace!(logger, "Failing HTLC ID {} back with a update_fail_htlc message", htlc_id_arg);
                {
                        let htlc = &mut self.pending_inbound_htlcs[pending_idx];
                        htlc.state = InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::FailRelay(err_packet.clone()));
@@ -1414,9 +1428,6 @@ impl<Signer: Sign> Channel<Signer> {
                if msg.channel_reserve_satoshis > self.channel_value_satoshis {
                        return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than ({})", msg.channel_reserve_satoshis, self.channel_value_satoshis)));
                }
-               if msg.dust_limit_satoshis > msg.channel_reserve_satoshis {
-                       return Err(ChannelError::Close(format!("Bogus channel_reserve ({}) and dust_limit ({})", msg.channel_reserve_satoshis, msg.dust_limit_satoshis)));
-               }
                if msg.channel_reserve_satoshis < self.holder_dust_limit_satoshis {
                        return Err(ChannelError::Close(format!("Peer never wants payout outputs? channel_reserve_satoshis was ({}). dust_limit is ({})", msg.channel_reserve_satoshis, self.holder_dust_limit_satoshis)));
                }
@@ -2305,6 +2316,16 @@ impl<Signer: Sign> Channel<Signer> {
                }, commitment_signed, closing_signed, monitor_update))
        }
 
+       /// Public version of the below, checking relevant preconditions first.
+       /// If we're not in a state where freeing the holding cell makes sense, this is a no-op and
+       /// returns `(None, Vec::new())`.
+       pub fn maybe_free_holding_cell_htlcs<L: Deref>(&mut self, logger: &L) -> Result<(Option<(msgs::CommitmentUpdate, ChannelMonitorUpdate)>, Vec<(HTLCSource, PaymentHash)>), ChannelError> where L::Target: Logger {
+               if self.channel_state >= ChannelState::ChannelFunded as u32 &&
+                  (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateFailed as u32)) == 0 {
+                       self.free_holding_cell_htlcs(logger)
+               } else { Ok((None, Vec::new())) }
+       }
+
        /// Used to fulfill holding_cell_htlcs when we get a remote ack (or implicitly get it by them
        /// fulfilling or failing the last pending HTLC)
        fn free_holding_cell_htlcs<L: Deref>(&mut self, logger: &L) -> Result<(Option<(msgs::CommitmentUpdate, ChannelMonitorUpdate)>, Vec<(HTLCSource, PaymentHash)>), ChannelError> where L::Target: Logger {
@@ -2369,7 +2390,7 @@ impl<Signer: Sign> Channel<Signer> {
                                                }
                                        },
                                        &HTLCUpdateAwaitingACK::FailHTLC { htlc_id, ref err_packet } => {
-                                               match self.get_update_fail_htlc(htlc_id, err_packet.clone()) {
+                                               match self.get_update_fail_htlc(htlc_id, err_packet.clone(), logger) {
                                                        Ok(update_fail_msg_option) => update_fail_htlcs.push(update_fail_msg_option.unwrap()),
                                                        Err(e) => {
                                                                if let ChannelError::Ignore(_) = e {}
@@ -2682,19 +2703,16 @@ impl<Signer: Sign> Channel<Signer> {
                }
        }
 
-       /// Removes any uncommitted HTLCs, to be used on peer disconnection, including any pending
-       /// HTLCs that we intended to add but haven't as we were waiting on a remote revoke.
-       /// Returns the set of PendingHTLCStatuses from remote uncommitted HTLCs (which we're
-       /// implicitly dropping) and the payment_hashes of HTLCs we tried to add but are dropping.
+       /// Removes any uncommitted inbound HTLCs and resets the state of uncommitted outbound HTLC
+       /// updates, to be used on peer disconnection. After this, update_*_htlc messages need to be
+       /// resent.
        /// No further message handling calls may be made until a channel_reestablish dance has
        /// completed.
-       pub fn remove_uncommitted_htlcs_and_mark_paused<L: Deref>(&mut self, logger: &L) -> Vec<(HTLCSource, PaymentHash)> where L::Target: Logger {
-               let mut outbound_drops = Vec::new();
-
+       pub fn remove_uncommitted_htlcs_and_mark_paused<L: Deref>(&mut self, logger: &L)  where L::Target: Logger {
                assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
                if self.channel_state < ChannelState::FundingSent as u32 {
                        self.channel_state = ChannelState::ShutdownComplete as u32;
-                       return outbound_drops;
+                       return;
                }
                // Upon reconnect we have to start the closing_signed dance over, but shutdown messages
                // will be retransmitted.
@@ -2737,23 +2755,8 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
 
-               self.holding_cell_htlc_updates.retain(|htlc_update| {
-                       match htlc_update {
-                               // Note that currently on channel reestablish we assert that there are
-                               // no holding cell HTLC update_adds, so if in the future we stop
-                               // dropping added HTLCs here and failing them backwards, then there will
-                               // need to be corresponding changes made in the Channel's re-establish
-                               // logic.
-                               &HTLCUpdateAwaitingACK::AddHTLC { ref payment_hash, ref source, .. } => {
-                                       outbound_drops.push((source.clone(), payment_hash.clone()));
-                                       false
-                               },
-                               &HTLCUpdateAwaitingACK::ClaimHTLC {..} | &HTLCUpdateAwaitingACK::FailHTLC {..} => true,
-                       }
-               });
                self.channel_state |= ChannelState::PeerDisconnected as u32;
-               log_debug!(logger, "Peer disconnection resulted in {} remote-announced HTLC drops and {} waiting-to-locally-announced HTLC drops on channel {}", outbound_drops.len(), inbound_drop_count, log_bytes!(self.channel_id()));
-               outbound_drops
+               log_debug!(logger, "Peer disconnection resulted in {} remote-announced HTLC drops on channel {}", inbound_drop_count, log_bytes!(self.channel_id()));
        }
 
        /// Indicates that a ChannelMonitor update failed to be stored by the client and further
@@ -2912,7 +2915,7 @@ impl<Signer: Sign> Channel<Signer> {
 
        /// May panic if some calls other than message-handling calls (which will all Err immediately)
        /// have been called between remove_uncommitted_htlcs_and_mark_paused and this call.
-       pub fn channel_reestablish<L: Deref>(&mut self, msg: &msgs::ChannelReestablish, logger: &L) -> Result<(Option<msgs::FundingLocked>, Option<msgs::RevokeAndACK>, Option<msgs::CommitmentUpdate>, Option<ChannelMonitorUpdate>, RAACommitmentOrder, Option<msgs::Shutdown>), ChannelError> where L::Target: Logger {
+       pub fn channel_reestablish<L: Deref>(&mut self, msg: &msgs::ChannelReestablish, logger: &L) -> Result<(Option<msgs::FundingLocked>, Option<msgs::RevokeAndACK>, Option<msgs::CommitmentUpdate>, Option<ChannelMonitorUpdate>, RAACommitmentOrder, Vec<(HTLCSource, PaymentHash)>, Option<msgs::Shutdown>), ChannelError> where L::Target: Logger {
                if self.channel_state & (ChannelState::PeerDisconnected as u32) == 0 {
                        // While BOLT 2 doesn't indicate explicitly we should error this channel here, it
                        // almost certainly indicates we are going to end up out-of-sync in some way, so we
@@ -2963,7 +2966,7 @@ impl<Signer: Sign> Channel<Signer> {
                                        return Err(ChannelError::Close("Peer claimed they saw a revoke_and_ack but we haven't sent funding_locked yet".to_owned()));
                                }
                                // Short circuit the whole handler as there is nothing we can resend them
-                               return Ok((None, None, None, None, RAACommitmentOrder::CommitmentFirst, shutdown_msg));
+                               return Ok((None, None, None, None, RAACommitmentOrder::CommitmentFirst, Vec::new(), shutdown_msg));
                        }
 
                        // We have OurFundingLocked set!
@@ -2971,7 +2974,7 @@ impl<Signer: Sign> Channel<Signer> {
                        return Ok((Some(msgs::FundingLocked {
                                channel_id: self.channel_id(),
                                next_per_commitment_point,
-                       }), None, None, None, RAACommitmentOrder::CommitmentFirst, shutdown_msg));
+                       }), None, None, None, RAACommitmentOrder::CommitmentFirst, Vec::new(), shutdown_msg));
                }
 
                let required_revoke = if msg.next_remote_commitment_number + 1 == INITIAL_COMMITMENT_NUMBER - self.cur_holder_commitment_transaction_number {
@@ -3012,14 +3015,6 @@ impl<Signer: Sign> Channel<Signer> {
                        }
 
                        if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::MonitorUpdateFailed as u32)) == 0 {
-                               // Note that if in the future we no longer drop holding cell update_adds on peer
-                               // disconnect, this logic will need to be updated.
-                               for htlc_update in self.holding_cell_htlc_updates.iter() {
-                                       if let &HTLCUpdateAwaitingACK::AddHTLC { .. } = htlc_update {
-                                               debug_assert!(false, "There shouldn't be any add-HTLCs in the holding cell now because they should have been dropped on peer disconnect. Panic here because said HTLCs won't be handled correctly.");
-                                       }
-                               }
-
                                // We're up-to-date and not waiting on a remote revoke (if we are our
                                // channel_reestablish should result in them sending a revoke_and_ack), but we may
                                // have received some updates while we were disconnected. Free the holding cell
@@ -3028,20 +3023,14 @@ impl<Signer: Sign> Channel<Signer> {
                                        Err(ChannelError::Close(msg)) => return Err(ChannelError::Close(msg)),
                                        Err(ChannelError::Ignore(_)) | Err(ChannelError::CloseDelayBroadcast(_)) => panic!("Got non-channel-failing result from free_holding_cell_htlcs"),
                                        Ok((Some((commitment_update, monitor_update)), htlcs_to_fail)) => {
-                                               // If in the future we no longer drop holding cell update_adds on peer
-                                               // disconnect, we may be handed some HTLCs to fail backwards here.
-                                               assert!(htlcs_to_fail.is_empty());
-                                               return Ok((resend_funding_locked, required_revoke, Some(commitment_update), Some(monitor_update), self.resend_order.clone(), shutdown_msg));
+                                               return Ok((resend_funding_locked, required_revoke, Some(commitment_update), Some(monitor_update), self.resend_order.clone(), htlcs_to_fail, shutdown_msg));
                                        },
                                        Ok((None, htlcs_to_fail)) => {
-                                               // If in the future we no longer drop holding cell update_adds on peer
-                                               // disconnect, we may be handed some HTLCs to fail backwards here.
-                                               assert!(htlcs_to_fail.is_empty());
-                                               return Ok((resend_funding_locked, required_revoke, None, None, self.resend_order.clone(), shutdown_msg));
+                                               return Ok((resend_funding_locked, required_revoke, None, None, self.resend_order.clone(), htlcs_to_fail, shutdown_msg));
                                        },
                                }
                        } else {
-                               return Ok((resend_funding_locked, required_revoke, None, None, self.resend_order.clone(), shutdown_msg));
+                               return Ok((resend_funding_locked, required_revoke, None, None, self.resend_order.clone(), Vec::new(), shutdown_msg));
                        }
                } else if msg.next_local_commitment_number == next_counterparty_commitment_number - 1 {
                        if required_revoke.is_some() {
@@ -3052,10 +3041,10 @@ impl<Signer: Sign> Channel<Signer> {
 
                        if self.channel_state & (ChannelState::MonitorUpdateFailed as u32) != 0 {
                                self.monitor_pending_commitment_signed = true;
-                               return Ok((resend_funding_locked, None, None, None, self.resend_order.clone(), shutdown_msg));
+                               return Ok((resend_funding_locked, None, None, None, self.resend_order.clone(), Vec::new(), shutdown_msg));
                        }
 
-                       return Ok((resend_funding_locked, required_revoke, Some(self.get_last_commitment_update(logger)), None, self.resend_order.clone(), shutdown_msg));
+                       return Ok((resend_funding_locked, required_revoke, Some(self.get_last_commitment_update(logger)), None, self.resend_order.clone(), Vec::new(), shutdown_msg));
                } else {
                        return Err(ChannelError::Close("Peer attempted to reestablish channel with a very old remote commitment transaction".to_owned()));
                }
@@ -3471,7 +3460,7 @@ impl<Signer: Sign> Channel<Signer> {
        /// is_usable() and considers things like the channel being temporarily disabled.
        /// Allowed in any state (including after shutdown)
        pub fn is_live(&self) -> bool {
-               self.is_usable() && (self.channel_state & (ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateFailed as u32) == 0)
+               self.is_usable() && (self.channel_state & (ChannelState::PeerDisconnected as u32) == 0)
        }
 
        /// Returns true if this channel has been marked as awaiting a monitor update to move forward.
@@ -3495,24 +3484,12 @@ impl<Signer: Sign> Channel<Signer> {
                } else { false }
        }
 
-       pub fn to_disabled_staged(&mut self) {
-               self.network_sync = UpdateStatus::DisabledStaged;
-       }
-
-       pub fn to_disabled_marked(&mut self) {
-               self.network_sync = UpdateStatus::DisabledMarked;
-       }
-
-       pub fn to_fresh(&mut self) {
-               self.network_sync = UpdateStatus::Fresh;
-       }
-
-       pub fn is_disabled_staged(&self) -> bool {
-               self.network_sync == UpdateStatus::DisabledStaged
+       pub fn channel_update_status(&self) -> ChannelUpdateStatus {
+               self.channel_update_status
        }
 
-       pub fn is_disabled_marked(&self) -> bool {
-               self.network_sync == UpdateStatus::DisabledMarked
+       pub fn set_channel_update_status(&mut self, status: ChannelUpdateStatus) {
+               self.channel_update_status = status;
        }
 
        fn check_get_funding_locked(&mut self, height: u32) -> Option<msgs::FundingLocked> {
@@ -3852,6 +3829,8 @@ impl<Signer: Sign> Channel<Signer> {
        /// closing).
        /// Note that the "channel must be funded" requirement is stricter than BOLT 7 requires - see
        /// https://github.com/lightningnetwork/lightning-rfc/issues/468
+       ///
+       /// This will only return ChannelError::Ignore upon failure.
        pub fn get_channel_announcement(&self, node_id: PublicKey, chain_hash: BlockHash) -> Result<(msgs::UnsignedChannelAnnouncement, Signature), ChannelError> {
                if !self.config.announced_channel {
                        return Err(ChannelError::Ignore("Channel is not available for public announcements".to_owned()));
@@ -3882,6 +3861,63 @@ impl<Signer: Sign> Channel<Signer> {
                Ok((msg, sig))
        }
 
+       /// Signs the given channel announcement, returning a ChannelError::Ignore if no keys are
+       /// available.
+       fn sign_channel_announcement(&self, our_node_secret: &SecretKey, our_node_id: PublicKey, msghash: secp256k1::Message, announcement: msgs::UnsignedChannelAnnouncement, our_bitcoin_sig: Signature) -> Result<msgs::ChannelAnnouncement, ChannelError> {
+               if let Some((their_node_sig, their_bitcoin_sig)) = self.announcement_sigs {
+                       let were_node_one = announcement.node_id_1 == our_node_id;
+
+                       let our_node_sig = self.secp_ctx.sign(&msghash, our_node_secret);
+                       Ok(msgs::ChannelAnnouncement {
+                               node_signature_1: if were_node_one { our_node_sig } else { their_node_sig },
+                               node_signature_2: if were_node_one { their_node_sig } else { our_node_sig },
+                               bitcoin_signature_1: if were_node_one { our_bitcoin_sig } else { their_bitcoin_sig },
+                               bitcoin_signature_2: if were_node_one { their_bitcoin_sig } else { our_bitcoin_sig },
+                               contents: announcement,
+                       })
+               } else {
+                       Err(ChannelError::Ignore("Attempted to sign channel announcement before we'd received announcement_signatures".to_string()))
+               }
+       }
+
+       /// Processes an incoming announcement_signatures message, providing a fully-signed
+       /// channel_announcement message which we can broadcast and storing our counterparty's
+       /// signatures for later reconstruction/rebroadcast of the channel_announcement.
+       pub fn announcement_signatures(&mut self, our_node_secret: &SecretKey, our_node_id: PublicKey, chain_hash: BlockHash, msg: &msgs::AnnouncementSignatures) -> Result<msgs::ChannelAnnouncement, ChannelError> {
+               let (announcement, our_bitcoin_sig) = self.get_channel_announcement(our_node_id.clone(), chain_hash)?;
+
+               let msghash = hash_to_message!(&Sha256d::hash(&announcement.encode()[..])[..]);
+
+               if self.secp_ctx.verify(&msghash, &msg.node_signature, &self.get_counterparty_node_id()).is_err() {
+                       return Err(ChannelError::Close(format!(
+                               "Bad announcement_signatures. Failed to verify node_signature. UnsignedChannelAnnouncement used for verification is {:?}. their_node_key is {:?}",
+                                &announcement, self.get_counterparty_node_id())));
+               }
+               if self.secp_ctx.verify(&msghash, &msg.bitcoin_signature, self.counterparty_funding_pubkey()).is_err() {
+                       return Err(ChannelError::Close(format!(
+                               "Bad announcement_signatures. Failed to verify bitcoin_signature. UnsignedChannelAnnouncement used for verification is {:?}. their_bitcoin_key is ({:?})",
+                               &announcement, self.counterparty_funding_pubkey())));
+               }
+
+               self.announcement_sigs = Some((msg.node_signature, msg.bitcoin_signature));
+
+               self.sign_channel_announcement(our_node_secret, our_node_id, msghash, announcement, our_bitcoin_sig)
+       }
+
+       /// Gets a signed channel_announcement for this channel, if we previously received an
+       /// announcement_signatures from our counterparty.
+       pub fn get_signed_channel_announcement(&self, our_node_secret: &SecretKey, our_node_id: PublicKey, chain_hash: BlockHash) -> Option<msgs::ChannelAnnouncement> {
+               let (announcement, our_bitcoin_sig) = match self.get_channel_announcement(our_node_id.clone(), chain_hash) {
+                       Ok(res) => res,
+                       Err(_) => return None,
+               };
+               let msghash = hash_to_message!(&Sha256d::hash(&announcement.encode()[..])[..]);
+               match self.sign_channel_announcement(our_node_secret, our_node_id, msghash, announcement, our_bitcoin_sig) {
+                       Ok(res) => Some(res),
+                       Err(_) => None,
+               }
+       }
+
        /// 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 {
@@ -3938,10 +3974,18 @@ impl<Signer: Sign> Channel<Signer> {
 
        /// Adds a pending outbound HTLC to this channel, note that you probably want
        /// send_htlc_and_commit instead cause you'll want both messages at once.
-       /// This returns an option instead of a pure UpdateAddHTLC as we may be in a state where we are
-       /// waiting on the remote peer to send us a revoke_and_ack during which time we cannot add new
-       /// HTLCs on the wire or we wouldn't be able to determine what they actually ACK'ed.
-       /// You MUST call send_commitment prior to any other calls on this Channel
+       ///
+       /// This returns an optional UpdateAddHTLC as we may be in a state where we cannot add HTLCs on
+       /// the wire:
+       /// * In cases where we're waiting on the remote peer to send us a revoke_and_ack, we
+       ///   wouldn't be able to determine what they actually ACK'ed if we have two sets of updates
+       ///   awaiting ACK.
+       /// * In cases where we're marked MonitorUpdateFailed, we cannot commit to a new state as we
+       ///   may not yet have sent the previous commitment update messages and will need to regenerate
+       ///   them.
+       ///
+       /// You MUST call send_commitment prior to calling any other methods on this Channel!
+       ///
        /// If an Err is returned, it's a ChannelError::Ignore!
        pub fn send_htlc(&mut self, amount_msat: u64, payment_hash: PaymentHash, cltv_expiry: u32, source: HTLCSource, onion_routing_packet: msgs::OnionPacket) -> Result<Option<msgs::UpdateAddHTLC>, ChannelError> {
                if (self.channel_state & (ChannelState::ChannelFunded as u32 | BOTH_SIDES_SHUTDOWN_MASK)) != (ChannelState::ChannelFunded as u32) {
@@ -3960,14 +4004,14 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Ignore(format!("Cannot send less than their minimum HTLC value ({})", self.counterparty_htlc_minimum_msat)));
                }
 
-               if (self.channel_state & (ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateFailed as u32)) != 0 {
+               if (self.channel_state & (ChannelState::PeerDisconnected as u32)) != 0 {
                        // Note that this should never really happen, if we're !is_live() on receipt of an
                        // incoming HTLC for relay will result in us rejecting the HTLC and we won't allow
                        // the user to send directly into a !is_live() channel. However, if we
                        // disconnected during the time the previous hop was doing the commitment dance we may
                        // end up getting here after the forwarding delay. In any case, returning an
                        // IgnoreError will get ChannelManager to do the right thing and fail backwards now.
-                       return Err(ChannelError::Ignore("Cannot send an HTLC while disconnected/frozen for channel monitor update".to_owned()));
+                       return Err(ChannelError::Ignore("Cannot send an HTLC while disconnected from channel counterparty".to_owned()));
                }
 
                let (outbound_htlc_count, htlc_outbound_value_msat) = self.get_outbound_pending_htlc_stats();
@@ -4012,7 +4056,7 @@ impl<Signer: Sign> Channel<Signer> {
                }
 
                // Now update local state:
-               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
+               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::MonitorUpdateFailed as u32)) != 0 {
                        self.holding_cell_htlc_updates.push(HTLCUpdateAwaitingACK::AddHTLC {
                                amount_msat,
                                payment_hash,
@@ -4343,33 +4387,32 @@ fn is_unsupported_shutdown_script(their_features: &InitFeatures, script: &Script
 const SERIALIZATION_VERSION: u8 = 1;
 const MIN_SERIALIZATION_VERSION: u8 = 1;
 
-impl Writeable for InboundHTLCRemovalReason {
+impl_writeable_tlv_based_enum!(InboundHTLCRemovalReason,;
+       (0, FailRelay),
+       (1, FailMalformed),
+       (2, Fulfill),
+);
+
+impl Writeable for ChannelUpdateStatus {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+               // We only care about writing out the current state as it was announced, ie only either
+               // Enabled or Disabled. In the case of DisabledStaged, we most recently announced the
+               // channel as enabled, so we write 0. For EnabledStaged, we similarly write a 1.
                match self {
-                       &InboundHTLCRemovalReason::FailRelay(ref error_packet) => {
-                               0u8.write(writer)?;
-                               error_packet.write(writer)?;
-                       },
-                       &InboundHTLCRemovalReason::FailMalformed((ref onion_hash, ref err_code)) => {
-                               1u8.write(writer)?;
-                               onion_hash.write(writer)?;
-                               err_code.write(writer)?;
-                       },
-                       &InboundHTLCRemovalReason::Fulfill(ref payment_preimage) => {
-                               2u8.write(writer)?;
-                               payment_preimage.write(writer)?;
-                       },
+                       ChannelUpdateStatus::Enabled => 0u8.write(writer)?,
+                       ChannelUpdateStatus::DisabledStaged => 0u8.write(writer)?,
+                       ChannelUpdateStatus::EnabledStaged => 1u8.write(writer)?,
+                       ChannelUpdateStatus::Disabled => 1u8.write(writer)?,
                }
                Ok(())
        }
 }
 
-impl Readable for InboundHTLCRemovalReason {
+impl Readable for ChannelUpdateStatus {
        fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                Ok(match <u8 as Readable>::read(reader)? {
-                       0 => InboundHTLCRemovalReason::FailRelay(Readable::read(reader)?),
-                       1 => InboundHTLCRemovalReason::FailMalformed((Readable::read(reader)?, Readable::read(reader)?)),
-                       2 => InboundHTLCRemovalReason::Fulfill(Readable::read(reader)?),
+                       0 => ChannelUpdateStatus::Enabled,
+                       1 => ChannelUpdateStatus::Disabled,
                        _ => return Err(DecodeError::InvalidValue),
                })
        }
@@ -4378,10 +4421,9 @@ impl Readable for InboundHTLCRemovalReason {
 impl<Signer: Sign> Writeable for Channel<Signer> {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                // Note that we write out as if remove_uncommitted_htlcs_and_mark_paused had just been
-               // called but include holding cell updates (and obviously we don't modify self).
+               // called.
 
-               writer.write_all(&[SERIALIZATION_VERSION; 1])?;
-               writer.write_all(&[MIN_SERIALIZATION_VERSION; 1])?;
+               write_ver_prefix!(writer, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);
 
                self.user_id.write(writer)?;
                self.config.write(writer)?;
@@ -4394,8 +4436,8 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
 
                let mut key_data = VecWriter(Vec::new());
                self.holder_signer.write(&mut key_data)?;
-               assert!(key_data.0.len() < std::usize::MAX);
-               assert!(key_data.0.len() < std::u32::MAX as usize);
+               assert!(key_data.0.len() < core::usize::MAX);
+               assert!(key_data.0.len() < core::u32::MAX as usize);
                (key_data.0.len() as u32).write(writer)?;
                writer.write_all(&key_data.0[..])?;
 
@@ -4456,9 +4498,10 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
                                &OutboundHTLCState::Committed => {
                                        1u8.write(writer)?;
                                },
-                               &OutboundHTLCState::RemoteRemoved(ref fail_reason) => {
-                                       2u8.write(writer)?;
-                                       fail_reason.write(writer)?;
+                               &OutboundHTLCState::RemoteRemoved(_) => {
+                                       // Treat this as a Committed because we haven't received the CS - they'll
+                                       // resend the claim/fail on reconnect as we all (hopefully) the missing CS.
+                                       1u8.write(writer)?;
                                },
                                &OutboundHTLCState::AwaitingRemoteRevokeToRemove(ref fail_reason) => {
                                        3u8.write(writer)?;
@@ -4568,6 +4611,11 @@ impl<Signer: Sign> Writeable for Channel<Signer> {
                self.counterparty_shutdown_scriptpubkey.write(writer)?;
 
                self.commitment_secrets.write(writer)?;
+
+               self.channel_update_status.write(writer)?;
+
+               write_tlv_fields!(writer, {}, {(0, self.announcement_sigs)});
+
                Ok(())
        }
 }
@@ -4576,11 +4624,7 @@ const MAX_ALLOC_SIZE: usize = 64*1024;
 impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                where K::Target: KeysInterface<Signer = Signer> {
        fn read<R : ::std::io::Read>(reader: &mut R, keys_source: &'a K) -> Result<Self, DecodeError> {
-               let _ver: u8 = Readable::read(reader)?;
-               let min_ver: u8 = Readable::read(reader)?;
-               if min_ver > SERIALIZATION_VERSION {
-                       return Err(DecodeError::UnknownVersion);
-               }
+               let _ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);
 
                let user_id = Readable::read(reader)?;
                let config: ChannelConfig = Readable::read(reader)?;
@@ -4740,6 +4784,11 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
                let counterparty_shutdown_scriptpubkey = Readable::read(reader)?;
                let commitment_secrets = Readable::read(reader)?;
 
+               let channel_update_status = Readable::read(reader)?;
+
+               let mut announcement_sigs = None;
+               read_tlv_fields!(reader, {}, {(0, announcement_sigs)});
+
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_source.get_secure_random_bytes());
 
@@ -4814,7 +4863,9 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel<Signer>
 
                        commitment_secrets,
 
-                       network_sync: UpdateStatus::Fresh,
+                       channel_update_status,
+
+                       announcement_sigs,
 
                        #[cfg(any(test, feature = "fuzztarget"))]
                        next_local_commitment_tx_fee_info_cached: Mutex::new(None),
@@ -4858,6 +4909,7 @@ mod tests {
        use bitcoin::hashes::Hash;
        use bitcoin::hash_types::{Txid, WPubkeyHash};
        use std::sync::Arc;
+       use prelude::*;
 
        struct TestFeeEstimator {
                fee_est: u32