DRY the get_route_and_payment_hash!() macro duplicated in tests
[rust-lightning] / lightning / src / ln / channelmanager.rs
index d2ea7dfea798baea181dec19838cf2b55ccaad22..4a67d244f196694888477b45e00561b1ff016498 100644 (file)
@@ -28,7 +28,7 @@ use bitcoin::hashes::hmac::{Hmac, HmacEngine};
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hashes::sha256d::Hash as Sha256dHash;
 use bitcoin::hashes::cmp::fixed_time_eq;
-use bitcoin::hash_types::BlockHash;
+use bitcoin::hash_types::{BlockHash, Txid};
 
 use bitcoin::secp256k1::key::{SecretKey,PublicKey};
 use bitcoin::secp256k1::Secp256k1;
@@ -36,6 +36,7 @@ use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1;
 
 use chain;
+use chain::Confirm;
 use chain::Watch;
 use chain::chaininterface::{BroadcasterInterface, FeeEstimator};
 use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateStep, ChannelMonitorUpdateErr, HTLC_FAIL_BACK_BUFFER, CLTV_CLAIM_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS, ANTI_REORG_DELAY, MonitorEvent, CLOSED_CHANNEL_UPDATE_ID};
@@ -352,8 +353,21 @@ struct PeerState {
        latest_features: InitFeatures,
 }
 
-#[cfg(not(any(target_pointer_width = "32", target_pointer_width = "64")))]
-const ERR: () = "You need at least 32 bit pointers (well, usize, but we'll assume they're the same) for ChannelManager::latest_block_height";
+/// Stores a PaymentSecret and any other data we may need to validate an inbound payment is
+/// actually ours and not some duplicate HTLC sent to us by a node along the route.
+///
+/// For users who don't want to bother doing their own payment preimage storage, we also store that
+/// here.
+struct PendingInboundPayment {
+       /// The payment secret that the sender must use for us to accept this payment
+       payment_secret: PaymentSecret,
+       /// Time at which this HTLC expires - blocks with a header time above this value will result in
+       /// this payment being removed.
+       expiry_time: u64,
+       // Other required attributes of the payment, optionally enforced:
+       payment_preimage: Option<PaymentPreimage>,
+       min_value_msat: Option<u64>,
+}
 
 /// SimpleArcChannelManager is useful when you need a ChannelManager with a static lifetime, e.g.
 /// when you're using lightning-net-tokio (since tokio::spawn requires parameters with static
@@ -424,16 +438,23 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        tx_broadcaster: T,
 
        #[cfg(test)]
-       pub(super) latest_block_height: AtomicUsize,
+       pub(super) best_block: RwLock<BestBlock>,
        #[cfg(not(test))]
-       latest_block_height: AtomicUsize,
-       last_block_hash: RwLock<BlockHash>,
+       best_block: RwLock<BestBlock>,
        secp_ctx: Secp256k1<secp256k1::All>,
 
        #[cfg(any(test, feature = "_test_utils"))]
        pub(super) channel_state: Mutex<ChannelHolder<Signer>>,
        #[cfg(not(any(test, feature = "_test_utils")))]
        channel_state: Mutex<ChannelHolder<Signer>>,
+
+       /// Storage for PaymentSecrets and any requirements on future inbound payments before we will
+       /// expose them to users via a PaymentReceived event. HTLCs which do not meet the requirements
+       /// here are failed when we process them as pending-forwardable-HTLCs, and entries are removed
+       /// after we generate a PaymentReceived upon receipt of all MPP parts.
+       /// Locked *after* channel_state.
+       pending_inbound_payments: Mutex<HashMap<PaymentHash, PendingInboundPayment>>,
+
        our_network_key: SecretKey,
        our_network_pubkey: PublicKey,
 
@@ -441,6 +462,11 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        /// value increases strictly since we don't assume access to a time source.
        last_node_announcement_serial: AtomicUsize,
 
+       /// The highest block timestamp we've seen, which is usually a good guess at the current time.
+       /// Assuming most miners are generating blocks with reasonable timestamps, this shouldn't be
+       /// very far in the past, and can only ever be up to two hours in the future.
+       highest_seen_timestamp: AtomicUsize,
+
        /// The bulk of our storage will eventually be here (channels and message queues and the like).
        /// If we are connected to a peer we always at least have an entry here, even if no channels
        /// are currently open with that peer.
@@ -475,13 +501,38 @@ pub struct ChainParameters {
        /// The network for determining the `chain_hash` in Lightning messages.
        pub network: Network,
 
-       /// The hash of the latest block successfully connected.
-       pub latest_hash: BlockHash,
-
-       /// The height of the latest block successfully connected.
+       /// The hash and height of the latest block successfully connected.
        ///
        /// Used to track on-chain channel funding outputs and send payments with reliable timelocks.
-       pub latest_height: usize,
+       pub best_block: BestBlock,
+}
+
+/// The best known block as identified by its hash and height.
+#[derive(Clone, Copy)]
+pub struct BestBlock {
+       block_hash: BlockHash,
+       height: u32,
+}
+
+impl BestBlock {
+       /// Returns the best block from the genesis of the given network.
+       pub fn from_genesis(network: Network) -> Self {
+               BestBlock {
+                       block_hash: genesis_block(network).header.block_hash(),
+                       height: 0,
+               }
+       }
+
+       /// Returns the best block as identified by the given block hash and height.
+       pub fn new(block_hash: BlockHash, height: u32) -> Self {
+               BestBlock { block_hash, height }
+       }
+
+       /// Returns the best block hash.
+       pub fn block_hash(&self) -> BlockHash { self.block_hash }
+
+       /// Returns the best block height.
+       pub fn height(&self) -> u32 { self.height }
 }
 
 /// Whenever we release the `ChannelManager`'s `total_consistency_lock`, from read mode, it is
@@ -822,8 +873,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        chain_monitor,
                        tx_broadcaster,
 
-                       latest_block_height: AtomicUsize::new(params.latest_height),
-                       last_block_hash: RwLock::new(params.latest_hash),
+                       best_block: RwLock::new(params.best_block),
 
                        channel_state: Mutex::new(ChannelHolder{
                                by_id: HashMap::new(),
@@ -832,11 +882,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                claimable_htlcs: HashMap::new(),
                                pending_msg_events: Vec::new(),
                        }),
+                       pending_inbound_payments: Mutex::new(HashMap::new()),
+
                        our_network_key: keys_manager.get_node_secret(),
                        our_network_pubkey: PublicKey::from_secret_key(&secp_ctx, &keys_manager.get_node_secret()),
                        secp_ctx,
 
                        last_node_announcement_serial: AtomicUsize::new(0),
+                       highest_seen_timestamp: AtomicUsize::new(0),
 
                        per_peer_state: RwLock::new(HashMap::new()),
 
@@ -851,6 +904,11 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                }
        }
 
+       /// Gets the current configuration applied to all new channels,  as
+       pub fn get_current_default_configuration(&self) -> &UserConfig {
+               &self.default_configuration
+       }
+
        /// Creates a new outbound channel to the given remote node and with the given value.
        ///
        /// user_id will be provided back as user_channel_id in FundingGenerationReady events to allow
@@ -1171,7 +1229,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                // HTLC_FAIL_BACK_BUFFER blocks to go.
                                // Also, ensure that, in the case of an unknown payment hash, our payment logic has enough time to fail the HTLC backward
                                // before our onchain logic triggers a channel closure (see HTLC_FAIL_BACK_BUFFER rational).
-                               if (msg.cltv_expiry as u64) <= self.latest_block_height.load(Ordering::Acquire) as u64 + HTLC_FAIL_BACK_BUFFER as u64 + 1 {
+                               if (msg.cltv_expiry as u64) <= self.best_block.read().unwrap().height() as u64 + HTLC_FAIL_BACK_BUFFER as u64 + 1 {
                                        return_err!("The final CLTV expiry is too soon to handle", 17, &[0;0]);
                                }
                                // final_incorrect_htlc_amount
@@ -1294,7 +1352,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        if (msg.cltv_expiry as u64) < (*outgoing_cltv_value) as u64 + chan.get_cltv_expiry_delta() as u64 { // incorrect_cltv_expiry
                                                break Some(("Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta", 0x1000 | 13, Some(self.get_channel_update(chan).unwrap())));
                                        }
-                                       let cur_height = self.latest_block_height.load(Ordering::Acquire) as u32 + 1;
+                                       let cur_height = self.best_block.read().unwrap().height() + 1;
                                        // Theoretically, channel counterparty shouldn't send us a HTLC expiring now, but we want to be robust wrt to counterparty
                                        // packet sanitization (see HTLC_FAIL_BACK_BUFFER rational)
                                        if msg.cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
@@ -1511,7 +1569,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        return Err(PaymentSendFailure::PathParameterError(path_errs));
                }
 
-               let cur_height = self.latest_block_height.load(Ordering::Acquire) as u32 + 1;
+               let cur_height = self.best_block.read().unwrap().height() + 1;
                let mut results = Vec::new();
                for path in route.paths.iter() {
                        results.push(self.send_payment_along_path(&path, &payment_hash, payment_secret, total_value, cur_height));
@@ -1538,61 +1596,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                }
        }
 
-       /// Call this upon creation of a funding transaction for the given channel.
-       ///
-       /// Returns an [`APIError::APIMisuseError`] if the funding_transaction spent non-SegWit outputs
-       /// or if no output was found which matches the parameters in [`Event::FundingGenerationReady`].
-       ///
-       /// Panics if a funding transaction has already been provided for this channel.
-       ///
-       /// May panic if the output found in the funding transaction is duplicative with some other
-       /// channel (note that this should be trivially prevented by using unique funding transaction
-       /// keys per-channel).
-       ///
-       /// Do NOT broadcast the funding transaction yourself. When we have safely received our
-       /// counterparty's signature the funding transaction will automatically be broadcast via the
-       /// [`BroadcasterInterface`] provided when this `ChannelManager` was constructed.
-       ///
-       /// Note that this includes RBF or similar transaction replacement strategies - lightning does
-       /// not currently support replacing a funding transaction on an existing channel. Instead,
-       /// create a new channel with a conflicting funding transaction.
-       pub fn funding_transaction_generated(&self, temporary_channel_id: &[u8; 32], funding_transaction: Transaction) -> Result<(), APIError> {
-               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
-
-               for inp in funding_transaction.input.iter() {
-                       if inp.witness.is_empty() {
-                               return Err(APIError::APIMisuseError {
-                                       err: "Funding transaction must be fully signed and spend Segwit outputs".to_owned()
-                               });
-                       }
-               }
-
+       /// Handles the generation of a funding transaction, optionally (for tests) with a function
+       /// which checks the correctness of the funding transaction given the associated channel.
+       fn funding_transaction_generated_intern<FundingOutput: Fn(&Channel<Signer>, &Transaction) -> Result<OutPoint, APIError>>
+                       (&self, temporary_channel_id: &[u8; 32], funding_transaction: Transaction, find_funding_output: FundingOutput) -> Result<(), APIError> {
                let (chan, msg) = {
                        let (res, chan) = match self.channel_state.lock().unwrap().by_id.remove(temporary_channel_id) {
                                Some(mut chan) => {
-                                       let mut output_index = None;
-                                       let expected_spk = chan.get_funding_redeemscript().to_v0_p2wsh();
-                                       for (idx, outp) in funding_transaction.output.iter().enumerate() {
-                                               if outp.script_pubkey == expected_spk && outp.value == chan.get_value_satoshis() {
-                                                       if output_index.is_some() {
-                                                               return Err(APIError::APIMisuseError {
-                                                                       err: "Multiple outputs matched the expected script and value".to_owned()
-                                                               });
-                                                       }
-                                                       if idx > u16::max_value() as usize {
-                                                               return Err(APIError::APIMisuseError {
-                                                                       err: "Transaction had more than 2^16 outputs, which is not supported".to_owned()
-                                                               });
-                                                       }
-                                                       output_index = Some(idx as u16);
-                                               }
-                                       }
-                                       if output_index.is_none() {
-                                               return Err(APIError::APIMisuseError {
-                                                       err: "No output matched the script_pubkey and value in the FundingGenerationReady event".to_owned()
-                                               });
-                                       }
-                                       let funding_txo = OutPoint { txid: funding_transaction.txid(), index: output_index.unwrap() };
+                                       let funding_txo = find_funding_output(&chan, &funding_transaction)?;
 
                                        (chan.get_outbound_funding_created(funding_transaction, funding_txo, &self.logger)
                                                .map_err(|e| if let ChannelError::Close(msg) = e {
@@ -1628,6 +1639,68 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                Ok(())
        }
 
+       #[cfg(test)]
+       pub(crate) fn funding_transaction_generated_unchecked(&self, temporary_channel_id: &[u8; 32], funding_transaction: Transaction, output_index: u16) -> Result<(), APIError> {
+               self.funding_transaction_generated_intern(temporary_channel_id, funding_transaction, |_, tx| {
+                       Ok(OutPoint { txid: tx.txid(), index: output_index })
+               })
+       }
+
+       /// Call this upon creation of a funding transaction for the given channel.
+       ///
+       /// Returns an [`APIError::APIMisuseError`] if the funding_transaction spent non-SegWit outputs
+       /// or if no output was found which matches the parameters in [`Event::FundingGenerationReady`].
+       ///
+       /// Panics if a funding transaction has already been provided for this channel.
+       ///
+       /// May panic if the output found in the funding transaction is duplicative with some other
+       /// channel (note that this should be trivially prevented by using unique funding transaction
+       /// keys per-channel).
+       ///
+       /// Do NOT broadcast the funding transaction yourself. When we have safely received our
+       /// counterparty's signature the funding transaction will automatically be broadcast via the
+       /// [`BroadcasterInterface`] provided when this `ChannelManager` was constructed.
+       ///
+       /// Note that this includes RBF or similar transaction replacement strategies - lightning does
+       /// not currently support replacing a funding transaction on an existing channel. Instead,
+       /// create a new channel with a conflicting funding transaction.
+       pub fn funding_transaction_generated(&self, temporary_channel_id: &[u8; 32], funding_transaction: Transaction) -> Result<(), APIError> {
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+
+               for inp in funding_transaction.input.iter() {
+                       if inp.witness.is_empty() {
+                               return Err(APIError::APIMisuseError {
+                                       err: "Funding transaction must be fully signed and spend Segwit outputs".to_owned()
+                               });
+                       }
+               }
+               self.funding_transaction_generated_intern(temporary_channel_id, funding_transaction, |chan, tx| {
+                       let mut output_index = None;
+                       let expected_spk = chan.get_funding_redeemscript().to_v0_p2wsh();
+                       for (idx, outp) in tx.output.iter().enumerate() {
+                               if outp.script_pubkey == expected_spk && outp.value == chan.get_value_satoshis() {
+                                       if output_index.is_some() {
+                                               return Err(APIError::APIMisuseError {
+                                                       err: "Multiple outputs matched the expected script and value".to_owned()
+                                               });
+                                       }
+                                       if idx > u16::max_value() as usize {
+                                               return Err(APIError::APIMisuseError {
+                                                       err: "Transaction had more than 2^16 outputs, which is not supported".to_owned()
+                                               });
+                                       }
+                                       output_index = Some(idx as u16);
+                               }
+                       }
+                       if output_index.is_none() {
+                               return Err(APIError::APIMisuseError {
+                                       err: "No output matched the script_pubkey and value in the FundingGenerationReady event".to_owned()
+                               });
+                       }
+                       Ok(OutPoint { txid: tx.txid(), index: output_index.unwrap() })
+               })
+       }
+
        fn get_announcement_sigs(&self, chan: &Channel<Signer>) -> Option<msgs::AnnouncementSignatures> {
                if !chan.should_announce() {
                        log_trace!(self.logger, "Can't send announcement_signatures for private channel {}", log_bytes!(chan.channel_id()));
@@ -1905,10 +1978,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                for htlc in htlcs.iter() {
                                                                                        let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
                                                                                        htlc_msat_height_data.extend_from_slice(
-                                                                                               &byte_utils::be32_to_array(
-                                                                                                       self.latest_block_height.load(Ordering::Acquire)
-                                                                                                               as u32,
-                                                                                               ),
+                                                                                               &byte_utils::be32_to_array(self.best_block.read().unwrap().height()),
                                                                                        );
                                                                                        failed_forwards.push((HTLCSource::PreviousHopData(HTLCPreviousHopData {
                                                                                                        short_channel_id: htlc.prev_hop.short_channel_id,
@@ -2028,8 +2098,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap()); }
                                let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
                                htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(
-                                       self.latest_block_height.load(Ordering::Acquire) as u32,
-                               ));
+                                               self.best_block.read().unwrap().height()));
                                self.fail_htlc_backwards_internal(channel_state.take().unwrap(),
                                                HTLCSource::PreviousHopData(htlc.prev_hop), payment_hash,
                                                HTLCFailReason::Reason { failure_code: 0x4000 | 15, data: htlc_msat_height_data });
@@ -2243,8 +2312,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                if (is_mpp && !valid_mpp) || (!is_mpp && (htlc.value < expected_amount || htlc.value > expected_amount * 2)) {
                                        let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
                                        htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(
-                                               self.latest_block_height.load(Ordering::Acquire) as u32,
-                                       ));
+                                                       self.best_block.read().unwrap().height()));
                                        self.fail_htlc_backwards_internal(channel_state.take().unwrap(),
                                                                         HTLCSource::PreviousHopData(htlc.prev_hop), &payment_hash,
                                                                         HTLCFailReason::Reason { failure_code: 0x4000|15, data: htlc_msat_height_data });
@@ -2529,7 +2597,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
        fn internal_funding_created(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingCreated) -> Result<(), MsgHandleErrInternal> {
                let ((funding_msg, monitor), mut chan) = {
-                       let last_block_hash = *self.last_block_hash.read().unwrap();
+                       let best_block = *self.best_block.read().unwrap();
                        let mut channel_lock = self.channel_state.lock().unwrap();
                        let channel_state = &mut *channel_lock;
                        match channel_state.by_id.entry(msg.temporary_channel_id.clone()) {
@@ -2537,7 +2605,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        if chan.get().get_counterparty_node_id() != *counterparty_node_id {
                                                return Err(MsgHandleErrInternal::send_err_msg_no_close("Got a message for a channel from the wrong node!".to_owned(), msg.temporary_channel_id));
                                        }
-                                       (try_chan_entry!(self, chan.get_mut().funding_created(msg, last_block_hash, &self.logger), channel_state, chan), chan.remove())
+                                       (try_chan_entry!(self, chan.get_mut().funding_created(msg, best_block, &self.logger), channel_state, chan), chan.remove())
                                },
                                hash_map::Entry::Vacant(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close("Failed to find corresponding channel".to_owned(), msg.temporary_channel_id))
                        }
@@ -2586,7 +2654,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
        fn internal_funding_signed(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingSigned) -> Result<(), MsgHandleErrInternal> {
                let funding_tx = {
-                       let last_block_hash = *self.last_block_hash.read().unwrap();
+                       let best_block = *self.best_block.read().unwrap();
                        let mut channel_lock = self.channel_state.lock().unwrap();
                        let channel_state = &mut *channel_lock;
                        match channel_state.by_id.entry(msg.channel_id) {
@@ -2594,7 +2662,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        if chan.get().get_counterparty_node_id() != *counterparty_node_id {
                                                return Err(MsgHandleErrInternal::send_err_msg_no_close("Got a message for a channel from the wrong node!".to_owned(), msg.channel_id));
                                        }
-                                       let (monitor, funding_tx) = match chan.get_mut().funding_signed(&msg, last_block_hash, &self.logger) {
+                                       let (monitor, funding_tx) = match chan.get_mut().funding_signed(&msg, best_block, &self.logger) {
                                                Ok(update) => update,
                                                Err(e) => try_chan_entry!(self, Err(e), channel_state, chan),
                                        };
@@ -3285,6 +3353,85 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        self.finish_force_close_channel(failure);
                }
        }
+
+       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
+
+               let payment_secret = PaymentSecret(self.keys_manager.get_secure_random_bytes());
+
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+               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,
+                                       // We assume that highest_seen_timestamp is pretty close to the current time -
+                                       // its 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.
+       ///
+       /// This differs from [`create_inbound_payment_for_hash`] only in that it generates the
+       /// [`PaymentHash`] and [`PaymentPreimage`] for you, returning the first and storing the second.
+       ///
+       /// See [`create_inbound_payment_for_hash`] for detailed documentation on behavior and requirements.
+       ///
+       /// [`create_inbound_payment_for_hash`]: Self::create_inbound_payment_for_hash
+       pub fn create_inbound_payment(&self, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32) -> (PaymentHash, PaymentSecret) {
+               let payment_preimage = PaymentPreimage(self.keys_manager.get_secure_random_bytes());
+               let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
+
+               (payment_hash,
+                       self.set_payment_hash_secret_map(payment_hash, Some(payment_preimage), min_value_msat, invoice_expiry_delta_secs)
+                               .expect("RNG Generated Duplicate PaymentHash"))
+       }
+
+       /// Gets a [`PaymentSecret`] for a given [`PaymentHash`], for which the payment preimage is
+       /// stored external to LDK.
+       ///
+       /// A [`PaymentReceived`] event will only be generated if the [`PaymentSecret`] matches a
+       /// payment secret fetched via this method or [`create_inbound_payment`], and which is at least
+       /// the `min_value_msat` provided here, if one is provided.
+       ///
+       /// The [`PaymentHash`] (and corresponding [`PaymentPreimage`]) must be globally unique. This
+       /// method may return an Err if another payment with the same payment_hash is still pending.
+       ///
+       /// `min_value_msat` should be set if the invoice being generated contains a value. Any payment
+       /// received for the returned [`PaymentHash`] will be required to be at least `min_value_msat`
+       /// before a [`PaymentReceived`] event will be generated, ensuring that we do not provide the
+       /// sender "proof-of-payment" unless they have paid the required amount.
+       ///
+       /// `invoice_expiry_delta_secs` describes the number of seconds that the invoice is valid for
+       /// in excess of the current time. This should roughly match the expiry time set in the invoice.
+       /// After this many seconds, we will remove the inbound payment, resulting in any attempts to
+       /// pay the invoice failing. The BOLT spec suggests 7,200 secs as a default validity time for
+       /// invoices when no timeout is set.
+       ///
+       /// Note that we use block header time to time-out pending inbound payments (with some margin
+       /// to compensate for the inaccuracy of block header timestamps). Thus, in practice we will
+       /// accept a payment and generate a [`PaymentReceived`] event for some time after the expiry.
+       /// If you need exact expiry semantics, you should enforce them upon receipt of
+       /// [`PaymentReceived`].
+       ///
+       /// May panic if `invoice_expiry_delta_secs` is greater than one year.
+       ///
+       /// [`create_inbound_payment`]: Self::create_inbound_payment
+       /// [`PaymentReceived`]: events::Event::PaymentReceived
+       pub fn create_inbound_payment_for_hash(&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)
+       }
 }
 
 impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> MessageSendEventsProvider for ChannelManager<Signer, M, T, K, F, L>
@@ -3334,38 +3481,125 @@ where
        L::Target: Logger,
 {
        fn block_connected(&self, block: &Block, height: u32) {
-               assert_eq!(*self.last_block_hash.read().unwrap(), block.header.prev_blockhash,
-                       "Blocks must be connected in chain-order - the connected header must build on the last connected header");
-               assert_eq!(self.latest_block_height.load(Ordering::Acquire) as u64, height as u64 - 1,
-                       "Blocks must be connected in chain-order - the connected block height must be one greater than the previous height");
+               {
+                       let best_block = self.best_block.read().unwrap();
+                       assert_eq!(best_block.block_hash(), block.header.prev_blockhash,
+                               "Blocks must be connected in chain-order - the connected header must build on the last connected header");
+                       assert_eq!(best_block.height(), height - 1,
+                               "Blocks must be connected in chain-order - the connected block height must be one greater than the previous height");
+               }
+
                let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
-               self.transactions_confirmed(&block.header, height, &txdata);
-               self.update_best_block(&block.header, height);
+               self.transactions_confirmed(&block.header, &txdata, height);
+               self.best_block_updated(&block.header, height);
        }
 
        fn block_disconnected(&self, header: &BlockHeader, height: u32) {
-               assert_eq!(*self.last_block_hash.read().unwrap(), header.block_hash(),
-                       "Blocks must be disconnected in chain-order - the disconnected header must be the last connected header");
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+               let new_height = height - 1;
+               {
+                       let mut best_block = self.best_block.write().unwrap();
+                       assert_eq!(best_block.block_hash(), header.block_hash(),
+                               "Blocks must be disconnected in chain-order - the disconnected header must be the last connected header");
+                       assert_eq!(best_block.height(), height,
+                               "Blocks must be disconnected in chain-order - the disconnected block must have the correct height");
+                       *best_block = BestBlock::new(header.prev_blockhash, new_height)
+               }
+
+               self.do_chain_event(Some(new_height), |channel| channel.best_block_updated(new_height, header.time));
+       }
+}
+
+impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> chain::Confirm for ChannelManager<Signer, M, T, K, F, L>
+where
+       M::Target: chain::Watch<Signer>,
+       T::Target: BroadcasterInterface,
+       K::Target: KeysInterface<Signer = Signer>,
+       F::Target: FeeEstimator,
+       L::Target: Logger,
+{
+       fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
+               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
+               // during initialization prior to the chain_monitor being fully configured in some cases.
+               // See the docs for `ChannelManagerReadArgs` for more.
+
+               let block_hash = header.block_hash();
+               log_trace!(self.logger, "{} transactions included in block {} at height {} provided", txdata.len(), block_hash, height);
 
                let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
-               let new_height = self.latest_block_height.fetch_sub(1, Ordering::AcqRel) as u32 - 1;
-               assert_eq!(new_height, height - 1,
-                       "Blocks must be disconnected in chain-order - the disconnected block must have the correct height");
-               *self.last_block_hash.write().unwrap() = header.prev_blockhash;
+               self.do_chain_event(Some(height), |channel| channel.transactions_confirmed(&block_hash, height, txdata, &self.logger).map(|a| (a, Vec::new())));
+       }
+
+       fn best_block_updated(&self, header: &BlockHeader, height: u32) {
+               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
+               // during initialization prior to the chain_monitor being fully configured in some cases.
+               // See the docs for `ChannelManagerReadArgs` for more.
 
-               self.do_chain_event(new_height, |channel| channel.update_best_block(new_height, header.time));
+               let block_hash = header.block_hash();
+               log_trace!(self.logger, "New best block: {} at height {}", block_hash, height);
+
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+
+               *self.best_block.write().unwrap() = BestBlock::new(block_hash, height);
+
+               self.do_chain_event(Some(height), |channel| channel.best_block_updated(height, header.time));
+
+               macro_rules! max_time {
+                       ($timestamp: expr) => {
+                               loop {
+                                       // Update $timestamp to be the max of its current value and the block
+                                       // timestamp. This should keep us close to the current time without relying on
+                                       // having an explicit local time source.
+                                       // Just in case we end up in a race, we loop until we either successfully
+                                       // update $timestamp or decide we don't need to.
+                                       let old_serial = $timestamp.load(Ordering::Acquire);
+                                       if old_serial >= header.time as usize { break; }
+                                       if $timestamp.compare_exchange(old_serial, header.time as usize, Ordering::AcqRel, Ordering::Relaxed).is_ok() {
+                                               break;
+                                       }
+                               }
+                       }
+               }
+               max_time!(self.last_node_announcement_serial);
+               max_time!(self.highest_seen_timestamp);
+       }
+
+       fn get_relevant_txids(&self) -> Vec<Txid> {
+               let channel_state = self.channel_state.lock().unwrap();
+               let mut res = Vec::with_capacity(channel_state.short_to_id.len());
+               for chan in channel_state.by_id.values() {
+                       if let Some(funding_txo) = chan.get_funding_txo() {
+                               res.push(funding_txo.txid);
+                       }
+               }
+               res
+       }
+
+       fn transaction_unconfirmed(&self, txid: &Txid) {
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+               self.do_chain_event(None, |channel| {
+                       if let Some(funding_txo) = channel.get_funding_txo() {
+                               if funding_txo.txid == *txid {
+                                       channel.funding_transaction_unconfirmed().map(|_| (None, Vec::new()))
+                               } else { Ok((None, Vec::new())) }
+                       } else { Ok((None, Vec::new())) }
+               });
        }
 }
 
 impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelManager<Signer, M, T, K, F, L>
-       where M::Target: chain::Watch<Signer>,
-        T::Target: BroadcasterInterface,
-        K::Target: KeysInterface<Signer = Signer>,
-        F::Target: FeeEstimator,
-        L::Target: Logger,
+where
+       M::Target: chain::Watch<Signer>,
+       T::Target: BroadcasterInterface,
+       K::Target: KeysInterface<Signer = Signer>,
+       F::Target: FeeEstimator,
+       L::Target: Logger,
 {
+       /// Calls a function which handles an on-chain event (blocks dis/connected, transactions
+       /// un/confirmed, etc) on each channel, handling any resulting errors or messages generated by
+       /// the function.
        fn do_chain_event<FN: Fn(&mut Channel<Signer>) -> Result<(Option<msgs::FundingLocked>, Vec<(HTLCSource, PaymentHash)>), msgs::ErrorMessage>>
-                       (&self, height: u32, f: FN) {
+                       (&self, height_opt: Option<u32>, f: FN) {
                // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
                // during initialization prior to the chain_monitor being fully configured in some cases.
                // See the docs for `ChannelManagerReadArgs` for more.
@@ -3424,24 +3658,26 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                true
                        });
 
-                       channel_state.claimable_htlcs.retain(|&(ref payment_hash, _), htlcs| {
-                               htlcs.retain(|htlc| {
-                                       // If height is approaching the number of blocks we think it takes us to get
-                                       // our commitment transaction confirmed before the HTLC expires, plus the
-                                       // number of blocks we generally consider it to take to do a commitment update,
-                                       // just give up on it and fail the HTLC.
-                                       if height >= htlc.cltv_expiry - HTLC_FAIL_BACK_BUFFER {
-                                               let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
-                                               htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(height));
-                                               timed_out_htlcs.push((HTLCSource::PreviousHopData(htlc.prev_hop.clone()), payment_hash.clone(), HTLCFailReason::Reason {
-                                                       failure_code: 0x4000 | 15,
-                                                       data: htlc_msat_height_data
-                                               }));
-                                               false
-                                       } else { true }
+                       if let Some(height) = height_opt {
+                               channel_state.claimable_htlcs.retain(|&(ref payment_hash, _), htlcs| {
+                                       htlcs.retain(|htlc| {
+                                               // If height is approaching the number of blocks we think it takes us to get
+                                               // our commitment transaction confirmed before the HTLC expires, plus the
+                                               // number of blocks we generally consider it to take to do a commitment update,
+                                               // just give up on it and fail the HTLC.
+                                               if height >= htlc.cltv_expiry - HTLC_FAIL_BACK_BUFFER {
+                                                       let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
+                                                       htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(height));
+                                                       timed_out_htlcs.push((HTLCSource::PreviousHopData(htlc.prev_hop.clone()), payment_hash.clone(), HTLCFailReason::Reason {
+                                                               failure_code: 0x4000 | 15,
+                                                               data: htlc_msat_height_data
+                                                       }));
+                                                       false
+                                               } else { true }
+                                       });
+                                       !htlcs.is_empty() // Only retain this entry if htlcs has at least one entry.
                                });
-                               !htlcs.is_empty() // Only retain this entry if htlcs has at least one entry.
-                       });
+                       }
                }
 
                self.handle_init_event_channel_failures(failed_channels);
@@ -3451,77 +3687,6 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                }
        }
 
-       /// Updates channel state to take note of transactions which were confirmed in the given block
-       /// at the given height.
-       ///
-       /// Note that you must still call (or have called) [`update_best_block`] with the block
-       /// information which is included here.
-       ///
-       /// This method may be called before or after [`update_best_block`] for a given block's
-       /// transaction data and may be called multiple times with additional transaction data for a
-       /// given block.
-       ///
-       /// This method may be called for a previous block after an [`update_best_block`] call has
-       /// been made for a later block, however it must *not* be called with transaction data from a
-       /// block which is no longer in the best chain (ie where [`update_best_block`] has already
-       /// been informed about a blockchain reorganization which no longer includes the block which
-       /// corresponds to `header`).
-       ///
-       /// [`update_best_block`]: `Self::update_best_block`
-       pub fn transactions_confirmed(&self, header: &BlockHeader, height: u32, txdata: &TransactionData) {
-               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
-               // during initialization prior to the chain_monitor being fully configured in some cases.
-               // See the docs for `ChannelManagerReadArgs` for more.
-
-               let block_hash = header.block_hash();
-               log_trace!(self.logger, "{} transactions included in block {} at height {} provided", txdata.len(), block_hash, height);
-
-               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
-               self.do_chain_event(height, |channel| channel.transactions_confirmed(&block_hash, height, txdata, &self.logger).map(|a| (a, Vec::new())));
-       }
-
-       /// Updates channel state with the current best blockchain tip. You should attempt to call this
-       /// quickly after a new block becomes available, however if multiple new blocks become
-       /// available at the same time, only a single `update_best_block()` call needs to be made.
-       ///
-       /// This method should also be called immediately after any block disconnections, once at the
-       /// reorganization fork point, and once with the new chain tip. Calling this method at the
-       /// blockchain reorganization fork point ensures we learn when a funding transaction which was
-       /// previously confirmed is reorganized out of the blockchain, ensuring we do not continue to
-       /// accept payments which cannot be enforced on-chain.
-       ///
-       /// In both the block-connection and block-disconnection case, this method may be called either
-       /// once per block connected or disconnected, or simply at the fork point and new tip(s),
-       /// skipping any intermediary blocks.
-       pub fn update_best_block(&self, header: &BlockHeader, height: u32) {
-               // Note that we MUST NOT end up calling methods on self.chain_monitor here - we're called
-               // during initialization prior to the chain_monitor being fully configured in some cases.
-               // See the docs for `ChannelManagerReadArgs` for more.
-
-               let block_hash = header.block_hash();
-               log_trace!(self.logger, "New best block: {} at height {}", block_hash, height);
-
-               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
-
-               self.latest_block_height.store(height as usize, Ordering::Release);
-               *self.last_block_hash.write().unwrap() = block_hash;
-
-               self.do_chain_event(height, |channel| channel.update_best_block(height, header.time));
-
-               loop {
-                       // Update last_node_announcement_serial to be the max of its current value and the
-                       // block timestamp. This should keep us close to the current time without relying on
-                       // having an explicit local time source.
-                       // Just in case we end up in a race, we loop until we either successfully update
-                       // last_node_announcement_serial or decide we don't need to.
-                       let old_serial = self.last_node_announcement_serial.load(Ordering::Acquire);
-                       if old_serial >= header.time as usize { break; }
-                       if self.last_node_announcement_serial.compare_exchange(old_serial, header.time as usize, Ordering::AcqRel, Ordering::Relaxed).is_ok() {
-                               break;
-                       }
-               }
-       }
-
        /// Blocks until ChannelManager needs to be persisted or a timeout is reached. It returns a bool
        /// indicating whether persistence is necessary. Only one listener on
        /// `await_persistable_update` or `await_persistable_update_timeout` is guaranteed to be woken
@@ -4068,6 +4233,13 @@ impl Readable for HTLCForwardInfo {
        }
 }
 
+impl_writeable!(PendingInboundPayment, 0, {
+       payment_secret,
+       expiry_time,
+       payment_preimage,
+       min_value_msat
+});
+
 impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable for ChannelManager<Signer, M, T, K, F, L>
        where M::Target: chain::Watch<Signer>,
         T::Target: BroadcasterInterface,
@@ -4082,8 +4254,11 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
                writer.write_all(&[MIN_SERIALIZATION_VERSION; 1])?;
 
                self.genesis_hash.write(writer)?;
-               (self.latest_block_height.load(Ordering::Acquire) as u32).write(writer)?;
-               self.last_block_hash.read().unwrap().write(writer)?;
+               {
+                       let best_block = self.best_block.read().unwrap();
+                       best_block.height().write(writer)?;
+                       best_block.block_hash().write(writer)?;
+               }
 
                let channel_state = self.channel_state.lock().unwrap();
                let mut unfunded_channels = 0;
@@ -4144,6 +4319,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
                }
 
                (self.last_node_announcement_serial.load(Ordering::Acquire) as u32).write(writer)?;
+               (self.highest_seen_timestamp.load(Ordering::Acquire) as u32).write(writer)?;
+
+               let pending_inbound_payments = self.pending_inbound_payments.lock().unwrap();
+               (pending_inbound_payments.len() as u64).write(writer)?;
+               for (hash, pending_payment) in pending_inbound_payments.iter() {
+                       hash.write(writer)?;
+                       pending_payment.write(writer)?;
+               }
 
                Ok(())
        }
@@ -4275,8 +4458,8 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                }
 
                let genesis_hash: BlockHash = Readable::read(reader)?;
-               let latest_block_height: u32 = Readable::read(reader)?;
-               let last_block_hash: BlockHash = Readable::read(reader)?;
+               let best_block_height: u32 = Readable::read(reader)?;
+               let best_block_hash: BlockHash = Readable::read(reader)?;
 
                let mut failed_htlcs = Vec::new();
 
@@ -4374,6 +4557,15 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                }
 
                let last_node_announcement_serial: u32 = Readable::read(reader)?;
+               let highest_seen_timestamp: u32 = Readable::read(reader)?;
+
+               let pending_inbound_payment_count: u64 = Readable::read(reader)?;
+               let mut pending_inbound_payments: HashMap<PaymentHash, PendingInboundPayment> = HashMap::with_capacity(cmp::min(pending_inbound_payment_count as usize, MAX_ALLOC_SIZE/(3*32)));
+               for _ in 0..pending_inbound_payment_count {
+                       if pending_inbound_payments.insert(Readable::read(reader)?, Readable::read(reader)?).is_some() {
+                               return Err(DecodeError::InvalidValue);
+                       }
+               }
 
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&args.keys_manager.get_secure_random_bytes());
@@ -4384,8 +4576,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                        chain_monitor: args.chain_monitor,
                        tx_broadcaster: args.tx_broadcaster,
 
-                       latest_block_height: AtomicUsize::new(latest_block_height as usize),
-                       last_block_hash: RwLock::new(last_block_hash),
+                       best_block: RwLock::new(BestBlock::new(best_block_hash, best_block_height)),
 
                        channel_state: Mutex::new(ChannelHolder {
                                by_id,
@@ -4394,11 +4585,14 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                                claimable_htlcs,
                                pending_msg_events: Vec::new(),
                        }),
+                       pending_inbound_payments: Mutex::new(pending_inbound_payments),
+
                        our_network_key: args.keys_manager.get_node_secret(),
                        our_network_pubkey: PublicKey::from_secret_key(&secp_ctx, &args.keys_manager.get_node_secret()),
                        secp_ctx,
 
                        last_node_announcement_serial: AtomicUsize::new(last_node_announcement_serial as usize),
+                       highest_seen_timestamp: AtomicUsize::new(highest_seen_timestamp as usize),
 
                        per_peer_state: RwLock::new(per_peer_state),
 
@@ -4419,7 +4613,7 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                //TODO: Broadcast channel update for closed channels, but only after we've made a
                //connection or two.
 
-               Ok((last_block_hash.clone(), channel_manager))
+               Ok((best_block_hash.clone(), channel_manager))
        }
 }
 
@@ -4480,7 +4674,7 @@ pub mod bench {
        use chain::chainmonitor::ChainMonitor;
        use chain::channelmonitor::Persist;
        use chain::keysinterface::{KeysManager, InMemorySigner};
-       use ln::channelmanager::{ChainParameters, ChannelManager, PaymentHash, PaymentPreimage};
+       use ln::channelmanager::{BestBlock, ChainParameters, ChannelManager, PaymentHash, PaymentPreimage};
        use ln::features::InitFeatures;
        use ln::functional_test_utils::*;
        use ln::msgs::ChannelMessageHandler;
@@ -4532,8 +4726,7 @@ pub mod bench {
                let keys_manager_a = KeysManager::new(&seed_a, 42, 42);
                let node_a = ChannelManager::new(&fee_estimator, &chain_monitor_a, &tx_broadcaster, &logger_a, &keys_manager_a, config.clone(), ChainParameters {
                        network,
-                       latest_hash: genesis_hash,
-                       latest_height: 0,
+                       best_block: BestBlock::from_genesis(network),
                });
                let node_a_holder = NodeHolder { node: &node_a };
 
@@ -4543,8 +4736,7 @@ pub mod bench {
                let keys_manager_b = KeysManager::new(&seed_b, 42, 42);
                let node_b = ChannelManager::new(&fee_estimator, &chain_monitor_b, &tx_broadcaster, &logger_b, &keys_manager_b, config.clone(), ChainParameters {
                        network,
-                       latest_hash: genesis_hash,
-                       latest_height: 0,
+                       best_block: BestBlock::from_genesis(network),
                });
                let node_b_holder = NodeHolder { node: &node_b };