[rust-lightning] / lightning / src / routing / gossip.rs

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! The [`NetworkGraph`] stores the network gossip and [`P2PGossipSync`] fetches it from peers

use bitcoin::blockdata::constants::ChainHash;

use bitcoin::secp256k1::constants::PUBLIC_KEY_SIZE;
use bitcoin::secp256k1::{PublicKey, Verification};
use bitcoin::secp256k1::Secp256k1;
use bitcoin::secp256k1;

use bitcoin::hashes::sha256d::Hash as Sha256dHash;
use bitcoin::hashes::Hash;
use bitcoin::network::constants::Network;

use crate::events::{MessageSendEvent, MessageSendEventsProvider};
use crate::ln::ChannelId;
use crate::ln::features::{ChannelFeatures, NodeFeatures, InitFeatures};
use crate::ln::msgs::{DecodeError, ErrorAction, Init, LightningError, RoutingMessageHandler, SocketAddress, MAX_VALUE_MSAT};
use crate::ln::msgs::{ChannelAnnouncement, ChannelUpdate, NodeAnnouncement, GossipTimestampFilter};
use crate::ln::msgs::{QueryChannelRange, ReplyChannelRange, QueryShortChannelIds, ReplyShortChannelIdsEnd};
use crate::ln::msgs;
use crate::routing::utxo::{self, UtxoLookup, UtxoResolver};
use crate::util::ser::{Readable, ReadableArgs, Writeable, Writer, MaybeReadable};
use crate::util::logger::{Logger, Level};
use crate::util::scid_utils::{block_from_scid, scid_from_parts, MAX_SCID_BLOCK};
use crate::util::string::PrintableString;
use crate::util::indexed_map::{IndexedMap, Entry as IndexedMapEntry};

use crate::io;
use crate::io_extras::{copy, sink};
use crate::prelude::*;
use core::{cmp, fmt};
use core::convert::TryFrom;
use crate::sync::{RwLock, RwLockReadGuard, LockTestExt};
use core::sync::atomic::{AtomicUsize, Ordering};
use crate::sync::Mutex;
use core::ops::{Bound, Deref};
use core::str::FromStr;

#[cfg(feature = "std")]
use std::time::{SystemTime, UNIX_EPOCH};

/// We remove stale channel directional info two weeks after the last update, per BOLT 7's
/// suggestion.
const STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS: u64 = 60 * 60 * 24 * 14;

/// We stop tracking the removal of permanently failed nodes and channels one week after removal
const REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS: u64 = 60 * 60 * 24 * 7;

/// The maximum number of extra bytes which we do not understand in a gossip message before we will
/// refuse to relay the message.
const MAX_EXCESS_BYTES_FOR_RELAY: usize = 1024;

/// Maximum number of short_channel_ids that will be encoded in one gossip reply message.
/// This value ensures a reply fits within the 65k payload limit and is consistent with other implementations.
const MAX_SCIDS_PER_REPLY: usize = 8000;

/// Represents the compressed public key of a node
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct NodeId([u8; PUBLIC_KEY_SIZE]);

impl NodeId {
        /// Create a new NodeId from a public key
        pub fn from_pubkey(pubkey: &PublicKey) -> Self {
                NodeId(pubkey.serialize())
        }

        /// Get the public key slice from this NodeId
        pub fn as_slice(&self) -> &[u8] {
                &self.0
        }

        /// Get the public key as an array from this NodeId
        pub fn as_array(&self) -> &[u8; PUBLIC_KEY_SIZE] {
                &self.0
        }

        /// Get the public key from this NodeId
        pub fn as_pubkey(&self) -> Result<PublicKey, secp256k1::Error> {
                PublicKey::from_slice(&self.0)
        }
}

impl fmt::Debug for NodeId {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                write!(f, "NodeId({})", crate::util::logger::DebugBytes(&self.0))
        }
}
impl fmt::Display for NodeId {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                crate::util::logger::DebugBytes(&self.0).fmt(f)
        }
}

impl core::hash::Hash for NodeId {
        fn hash<H: core::hash::Hasher>(&self, hasher: &mut H) {
                self.0.hash(hasher);
        }
}

impl cmp::PartialOrd for NodeId {
        fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
                Some(self.cmp(other))
        }
}

impl Ord for NodeId {
        fn cmp(&self, other: &Self) -> cmp::Ordering {
                self.0[..].cmp(&other.0[..])
        }
}

impl Writeable for NodeId {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                writer.write_all(&self.0)?;
                Ok(())
        }
}

impl Readable for NodeId {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                let mut buf = [0; PUBLIC_KEY_SIZE];
                reader.read_exact(&mut buf)?;
                Ok(Self(buf))
        }
}

impl From<PublicKey> for NodeId {
        fn from(pubkey: PublicKey) -> Self {
                Self::from_pubkey(&pubkey)
        }
}

impl TryFrom<NodeId> for PublicKey {
        type Error = secp256k1::Error;

        fn try_from(node_id: NodeId) -> Result<Self, Self::Error> {
                node_id.as_pubkey()
        }
}

impl FromStr for NodeId {
        type Err = hex::parse::HexToArrayError;

        fn from_str(s: &str) -> Result<Self, Self::Err> {
                let data: [u8; PUBLIC_KEY_SIZE] = hex::FromHex::from_hex(s)?;
                Ok(NodeId(data))
        }
}

/// Represents the network as nodes and channels between them
pub struct NetworkGraph<L: Deref> where L::Target: Logger {
        secp_ctx: Secp256k1<secp256k1::VerifyOnly>,
        last_rapid_gossip_sync_timestamp: Mutex<Option<u32>>,
        chain_hash: ChainHash,
        logger: L,
        // Lock order: channels -> nodes
        channels: RwLock<IndexedMap<u64, ChannelInfo>>,
        nodes: RwLock<IndexedMap<NodeId, NodeInfo>>,
        removed_node_counters: Mutex<Vec<u32>>,
        next_node_counter: AtomicUsize,
        // Lock order: removed_channels -> removed_nodes
        //
        // NOTE: In the following `removed_*` maps, we use seconds since UNIX epoch to track time instead
        // of `std::time::Instant`s for a few reasons:
        //   * We want it to be possible to do tracking in no-std environments where we can compare
        //     a provided current UNIX timestamp with the time at which we started tracking.
        //   * In the future, if we decide to persist these maps, they will already be serializable.
        //   * Although we lose out on the platform's monotonic clock, the system clock in a std
        //     environment should be practical over the time period we are considering (on the order of a
        //     week).
        //
        /// Keeps track of short channel IDs for channels we have explicitly removed due to permanent
        /// failure so that we don't resync them from gossip. Each SCID is mapped to the time (in seconds)
        /// it was removed so that once some time passes, we can potentially resync it from gossip again.
        removed_channels: Mutex<HashMap<u64, Option<u64>>>,
        /// Keeps track of `NodeId`s we have explicitly removed due to permanent failure so that we don't
        /// resync them from gossip. Each `NodeId` is mapped to the time (in seconds) it was removed so
        /// that once some time passes, we can potentially resync it from gossip again.
        removed_nodes: Mutex<HashMap<NodeId, Option<u64>>>,
        /// Announcement messages which are awaiting an on-chain lookup to be processed.
        pub(super) pending_checks: utxo::PendingChecks,
}

/// A read-only view of [`NetworkGraph`].
pub struct ReadOnlyNetworkGraph<'a> {
        channels: RwLockReadGuard<'a, IndexedMap<u64, ChannelInfo>>,
        nodes: RwLockReadGuard<'a, IndexedMap<NodeId, NodeInfo>>,
        max_node_counter: u32,
}

/// Update to the [`NetworkGraph`] based on payment failure information conveyed via the Onion
/// return packet by a node along the route. See [BOLT #4] for details.
///
/// [BOLT #4]: https://github.com/lightning/bolts/blob/master/04-onion-routing.md
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum NetworkUpdate {
        /// An error indicating a `channel_update` messages should be applied via
        /// [`NetworkGraph::update_channel`].
        ChannelUpdateMessage {
                /// The update to apply via [`NetworkGraph::update_channel`].
                msg: ChannelUpdate,
        },
        /// An error indicating that a channel failed to route a payment, which should be applied via
        /// [`NetworkGraph::channel_failed_permanent`] if permanent.
        ChannelFailure {
                /// The short channel id of the closed channel.
                short_channel_id: u64,
                /// Whether the channel should be permanently removed or temporarily disabled until a new
                /// `channel_update` message is received.
                is_permanent: bool,
        },
        /// An error indicating that a node failed to route a payment, which should be applied via
        /// [`NetworkGraph::node_failed_permanent`] if permanent.
        NodeFailure {
                /// The node id of the failed node.
                node_id: PublicKey,
                /// Whether the node should be permanently removed from consideration or can be restored
                /// when a new `channel_update` message is received.
                is_permanent: bool,
        }
}

impl_writeable_tlv_based_enum_upgradable!(NetworkUpdate,
        (0, ChannelUpdateMessage) => {
                (0, msg, required),
        },
        (2, ChannelFailure) => {
                (0, short_channel_id, required),
                (2, is_permanent, required),
        },
        (4, NodeFailure) => {
                (0, node_id, required),
                (2, is_permanent, required),
        },
);

/// Receives and validates network updates from peers,
/// stores authentic and relevant data as a network graph.
/// This network graph is then used for routing payments.
/// Provides interface to help with initial routing sync by
/// serving historical announcements.
pub struct P2PGossipSync<G: Deref<Target=NetworkGraph<L>>, U: Deref, L: Deref>
where U::Target: UtxoLookup, L::Target: Logger
{
        network_graph: G,
        utxo_lookup: RwLock<Option<U>>,
        #[cfg(feature = "std")]
        full_syncs_requested: AtomicUsize,
        pending_events: Mutex<Vec<MessageSendEvent>>,
        logger: L,
}

impl<G: Deref<Target=NetworkGraph<L>>, U: Deref, L: Deref> P2PGossipSync<G, U, L>
where U::Target: UtxoLookup, L::Target: Logger
{
        /// Creates a new tracker of the actual state of the network of channels and nodes,
        /// assuming an existing [`NetworkGraph`].
        /// UTXO lookup is used to make sure announced channels exist on-chain, channel data is
        /// correct, and the announcement is signed with channel owners' keys.
        pub fn new(network_graph: G, utxo_lookup: Option<U>, logger: L) -> Self {
                P2PGossipSync {
                        network_graph,
                        #[cfg(feature = "std")]
                        full_syncs_requested: AtomicUsize::new(0),
                        utxo_lookup: RwLock::new(utxo_lookup),
                        pending_events: Mutex::new(vec![]),
                        logger,
                }
        }

        /// Adds a provider used to check new announcements. Does not affect
        /// existing announcements unless they are updated.
        /// Add, update or remove the provider would replace the current one.
        pub fn add_utxo_lookup(&self, utxo_lookup: Option<U>) {
                *self.utxo_lookup.write().unwrap() = utxo_lookup;
        }

        /// Gets a reference to the underlying [`NetworkGraph`] which was provided in
        /// [`P2PGossipSync::new`].
        ///
        /// This is not exported to bindings users as bindings don't support a reference-to-a-reference yet
        pub fn network_graph(&self) -> &G {
                &self.network_graph
        }

        #[cfg(feature = "std")]
        /// Returns true when a full routing table sync should be performed with a peer.
        fn should_request_full_sync(&self, _node_id: &PublicKey) -> bool {
                //TODO: Determine whether to request a full sync based on the network map.
                const FULL_SYNCS_TO_REQUEST: usize = 5;
                if self.full_syncs_requested.load(Ordering::Acquire) < FULL_SYNCS_TO_REQUEST {
                        self.full_syncs_requested.fetch_add(1, Ordering::AcqRel);
                        true
                } else {
                        false
                }
        }

        /// Used to broadcast forward gossip messages which were validated async.
        ///
        /// Note that this will ignore events other than `Broadcast*` or messages with too much excess
        /// data.
        pub(super) fn forward_gossip_msg(&self, mut ev: MessageSendEvent) {
                match &mut ev {
                        MessageSendEvent::BroadcastChannelAnnouncement { msg, ref mut update_msg } => {
                                if msg.contents.excess_data.len() > MAX_EXCESS_BYTES_FOR_RELAY { return; }
                                if update_msg.as_ref()
                                        .map(|msg| msg.contents.excess_data.len()).unwrap_or(0) > MAX_EXCESS_BYTES_FOR_RELAY
                                {
                                        *update_msg = None;
                                }
                        },
                        MessageSendEvent::BroadcastChannelUpdate { msg } => {
                                if msg.contents.excess_data.len() > MAX_EXCESS_BYTES_FOR_RELAY { return; }
                        },
                        MessageSendEvent::BroadcastNodeAnnouncement { msg } => {
                                if msg.contents.excess_data.len() >  MAX_EXCESS_BYTES_FOR_RELAY ||
                                   msg.contents.excess_address_data.len() > MAX_EXCESS_BYTES_FOR_RELAY ||
                                   msg.contents.excess_data.len() + msg.contents.excess_address_data.len() > MAX_EXCESS_BYTES_FOR_RELAY
                                {
                                        return;
                                }
                        },
                        _ => return,
                }
                self.pending_events.lock().unwrap().push(ev);
        }
}

impl<L: Deref> NetworkGraph<L> where L::Target: Logger {
        /// Handles any network updates originating from [`Event`]s.
        //
        /// Note that this will skip applying any [`NetworkUpdate::ChannelUpdateMessage`] to avoid
        /// leaking possibly identifying information of the sender to the public network.
        ///
        /// [`Event`]: crate::events::Event
        pub fn handle_network_update(&self, network_update: &NetworkUpdate) {
                match *network_update {
                        NetworkUpdate::ChannelUpdateMessage { ref msg } => {
                                let short_channel_id = msg.contents.short_channel_id;
                                let is_enabled = msg.contents.flags & (1 << 1) != (1 << 1);
                                let status = if is_enabled { "enabled" } else { "disabled" };
                                log_debug!(self.logger, "Skipping application of a channel update from a payment failure. Channel {} is {}.", short_channel_id, status);
                        },
                        NetworkUpdate::ChannelFailure { short_channel_id, is_permanent } => {
                                if is_permanent {
                                        log_debug!(self.logger, "Removing channel graph entry for {} due to a payment failure.", short_channel_id);
                                        self.channel_failed_permanent(short_channel_id);
                                }
                        },
                        NetworkUpdate::NodeFailure { ref node_id, is_permanent } => {
                                if is_permanent {
                                        log_debug!(self.logger,
                                                "Removed node graph entry for {} due to a payment failure.", log_pubkey!(node_id));
                                        self.node_failed_permanent(node_id);
                                };
                        },
                }
        }

        /// Gets the chain hash for this network graph.
        pub fn get_chain_hash(&self) -> ChainHash {
                self.chain_hash
        }
}

macro_rules! secp_verify_sig {
        ( $secp_ctx: expr, $msg: expr, $sig: expr, $pubkey: expr, $msg_type: expr ) => {
                match $secp_ctx.verify_ecdsa($msg, $sig, $pubkey) {
                        Ok(_) => {},
                        Err(_) => {
                                return Err(LightningError {
                                        err: format!("Invalid signature on {} message", $msg_type),
                                        action: ErrorAction::SendWarningMessage {
                                                msg: msgs::WarningMessage {
                                                        channel_id: ChannelId::new_zero(),
                                                        data: format!("Invalid signature on {} message", $msg_type),
                                                },
                                                log_level: Level::Trace,
                                        },
                                });
                        },
                }
        };
}

macro_rules! get_pubkey_from_node_id {
        ( $node_id: expr, $msg_type: expr ) => {
                PublicKey::from_slice($node_id.as_slice())
                        .map_err(|_| LightningError {
                                err: format!("Invalid public key on {} message", $msg_type),
                                action: ErrorAction::SendWarningMessage {
                                        msg: msgs::WarningMessage {
                                                channel_id: ChannelId::new_zero(),
                                                data: format!("Invalid public key on {} message", $msg_type),
                                        },
                                        log_level: Level::Trace
                                }
                        })?
        }
}

fn message_sha256d_hash<M: Writeable>(msg: &M) -> Sha256dHash {
        let mut engine = Sha256dHash::engine();
        msg.write(&mut engine).expect("In-memory structs should not fail to serialize");
        Sha256dHash::from_engine(engine)
}

/// Verifies the signature of a [`NodeAnnouncement`].
///
/// Returns an error if it is invalid.
pub fn verify_node_announcement<C: Verification>(msg: &NodeAnnouncement, secp_ctx: &Secp256k1<C>) -> Result<(), LightningError> {
        let msg_hash = hash_to_message!(&message_sha256d_hash(&msg.contents)[..]);
        secp_verify_sig!(secp_ctx, &msg_hash, &msg.signature, &get_pubkey_from_node_id!(msg.contents.node_id, "node_announcement"), "node_announcement");

        Ok(())
}

/// Verifies all signatures included in a [`ChannelAnnouncement`].
///
/// Returns an error if one of the signatures is invalid.
pub fn verify_channel_announcement<C: Verification>(msg: &ChannelAnnouncement, secp_ctx: &Secp256k1<C>) -> Result<(), LightningError> {
        let msg_hash = hash_to_message!(&message_sha256d_hash(&msg.contents)[..]);
        secp_verify_sig!(secp_ctx, &msg_hash, &msg.node_signature_1, &get_pubkey_from_node_id!(msg.contents.node_id_1, "channel_announcement"), "channel_announcement");
        secp_verify_sig!(secp_ctx, &msg_hash, &msg.node_signature_2, &get_pubkey_from_node_id!(msg.contents.node_id_2, "channel_announcement"), "channel_announcement");
        secp_verify_sig!(secp_ctx, &msg_hash, &msg.bitcoin_signature_1, &get_pubkey_from_node_id!(msg.contents.bitcoin_key_1, "channel_announcement"), "channel_announcement");
        secp_verify_sig!(secp_ctx, &msg_hash, &msg.bitcoin_signature_2, &get_pubkey_from_node_id!(msg.contents.bitcoin_key_2, "channel_announcement"), "channel_announcement");

        Ok(())
}

impl<G: Deref<Target=NetworkGraph<L>>, U: Deref, L: Deref> RoutingMessageHandler for P2PGossipSync<G, U, L>
where U::Target: UtxoLookup, L::Target: Logger
{
        fn handle_node_announcement(&self, msg: &msgs::NodeAnnouncement) -> Result<bool, LightningError> {
                self.network_graph.update_node_from_announcement(msg)?;
                Ok(msg.contents.excess_data.len() <=  MAX_EXCESS_BYTES_FOR_RELAY &&
                   msg.contents.excess_address_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY &&
                   msg.contents.excess_data.len() + msg.contents.excess_address_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY)
        }

        fn handle_channel_announcement(&self, msg: &msgs::ChannelAnnouncement) -> Result<bool, LightningError> {
                self.network_graph.update_channel_from_announcement(msg, &*self.utxo_lookup.read().unwrap())?;
                Ok(msg.contents.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY)
        }

        fn handle_channel_update(&self, msg: &msgs::ChannelUpdate) -> Result<bool, LightningError> {
                self.network_graph.update_channel(msg)?;
                Ok(msg.contents.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY)
        }

        fn get_next_channel_announcement(&self, starting_point: u64) -> Option<(ChannelAnnouncement, Option<ChannelUpdate>, Option<ChannelUpdate>)> {
                let mut channels = self.network_graph.channels.write().unwrap();
                for (_, ref chan) in channels.range(starting_point..) {
                        if chan.announcement_message.is_some() {
                                let chan_announcement = chan.announcement_message.clone().unwrap();
                                let mut one_to_two_announcement: Option<msgs::ChannelUpdate> = None;
                                let mut two_to_one_announcement: Option<msgs::ChannelUpdate> = None;
                                if let Some(one_to_two) = chan.one_to_two.as_ref() {
                                        one_to_two_announcement = one_to_two.last_update_message.clone();
                                }
                                if let Some(two_to_one) = chan.two_to_one.as_ref() {
                                        two_to_one_announcement = two_to_one.last_update_message.clone();
                                }
                                return Some((chan_announcement, one_to_two_announcement, two_to_one_announcement));
                        } else {
                                // TODO: We may end up sending un-announced channel_updates if we are sending
                                // initial sync data while receiving announce/updates for this channel.
                        }
                }
                None
        }

        fn get_next_node_announcement(&self, starting_point: Option<&NodeId>) -> Option<NodeAnnouncement> {
                let mut nodes = self.network_graph.nodes.write().unwrap();
                let iter = if let Some(node_id) = starting_point {
                                nodes.range((Bound::Excluded(node_id), Bound::Unbounded))
                        } else {
                                nodes.range(..)
                        };
                for (_, ref node) in iter {
                        if let Some(node_info) = node.announcement_info.as_ref() {
                                if let Some(msg) = node_info.announcement_message.clone() {
                                        return Some(msg);
                                }
                        }
                }
                None
        }

        /// Initiates a stateless sync of routing gossip information with a peer
        /// using [`gossip_queries`]. The default strategy used by this implementation
        /// is to sync the full block range with several peers.
        ///
        /// We should expect one or more [`reply_channel_range`] messages in response
        /// to our [`query_channel_range`]. Each reply will enqueue a [`query_scid`] message
        /// to request gossip messages for each channel. The sync is considered complete
        /// when the final [`reply_scids_end`] message is received, though we are not
        /// tracking this directly.
        ///
        /// [`gossip_queries`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#query-messages
        /// [`reply_channel_range`]: msgs::ReplyChannelRange
        /// [`query_channel_range`]: msgs::QueryChannelRange
        /// [`query_scid`]: msgs::QueryShortChannelIds
        /// [`reply_scids_end`]: msgs::ReplyShortChannelIdsEnd
        fn peer_connected(&self, their_node_id: &PublicKey, init_msg: &Init, _inbound: bool) -> Result<(), ()> {
                // We will only perform a sync with peers that support gossip_queries.
                if !init_msg.features.supports_gossip_queries() {
                        // Don't disconnect peers for not supporting gossip queries. We may wish to have
                        // channels with peers even without being able to exchange gossip.
                        return Ok(());
                }

                // The lightning network's gossip sync system is completely broken in numerous ways.
                //
                // Given no broadly-available set-reconciliation protocol, the only reasonable approach is
                // to do a full sync from the first few peers we connect to, and then receive gossip
                // updates from all our peers normally.
                //
                // Originally, we could simply tell a peer to dump us the entire gossip table on startup,
                // wasting lots of bandwidth but ensuring we have the full network graph. After the initial
                // dump peers would always send gossip and we'd stay up-to-date with whatever our peer has
                // seen.
                //
                // In order to reduce the bandwidth waste, "gossip queries" were introduced, allowing you
                // to ask for the SCIDs of all channels in your peer's routing graph, and then only request
                // channel data which you are missing. Except there was no way at all to identify which
                // `channel_update`s you were missing, so you still had to request everything, just in a
                // very complicated way with some queries instead of just getting the dump.
                //
                // Later, an option was added to fetch the latest timestamps of the `channel_update`s to
                // make efficient sync possible, however it has yet to be implemented in lnd, which makes
                // relying on it useless.
                //
                // After gossip queries were introduced, support for receiving a full gossip table dump on
                // connection was removed from several nodes, making it impossible to get a full sync
                // without using the "gossip queries" messages.
                //
                // Once you opt into "gossip queries" the only way to receive any gossip updates that a
                // peer receives after you connect, you must send a `gossip_timestamp_filter` message. This
                // message, as the name implies, tells the peer to not forward any gossip messages with a
                // timestamp older than a given value (not the time the peer received the filter, but the
                // timestamp in the update message, which is often hours behind when the peer received the
                // message).
                //
                // Obnoxiously, `gossip_timestamp_filter` isn't *just* a filter, but its also a request for
                // your peer to send you the full routing graph (subject to the filter). Thus, in order to
                // tell a peer to send you any updates as it sees them, you have to also ask for the full
                // routing graph to be synced. If you set a timestamp filter near the current time, peers
                // will simply not forward any new updates they see to you which were generated some time
                // ago (which is not uncommon). If you instead set a timestamp filter near 0 (or two weeks
                // ago), you will always get the full routing graph from all your peers.
                //
                // Most lightning nodes today opt to simply turn off receiving gossip data which only
                // propagated some time after it was generated, and, worse, often disable gossiping with
                // several peers after their first connection. The second behavior can cause gossip to not
                // propagate fully if there are cuts in the gossiping subgraph.
                //
                // In an attempt to cut a middle ground between always fetching the full graph from all of
                // our peers and never receiving gossip from peers at all, we send all of our peers a
                // `gossip_timestamp_filter`, with the filter time set either two weeks ago or an hour ago.
                //
                // For no-std builds, we bury our head in the sand and do a full sync on each connection.
                #[allow(unused_mut, unused_assignments)]
                let mut gossip_start_time = 0;
                #[cfg(feature = "std")]
                {
                        gossip_start_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                        if self.should_request_full_sync(&their_node_id) {
                                gossip_start_time -= 60 * 60 * 24 * 7 * 2; // 2 weeks ago
                        } else {
                                gossip_start_time -= 60 * 60; // an hour ago
                        }
                }

                let mut pending_events = self.pending_events.lock().unwrap();
                pending_events.push(MessageSendEvent::SendGossipTimestampFilter {
                        node_id: their_node_id.clone(),
                        msg: GossipTimestampFilter {
                                chain_hash: self.network_graph.chain_hash,
                                first_timestamp: gossip_start_time as u32, // 2106 issue!
                                timestamp_range: u32::max_value(),
                        },
                });
                Ok(())
        }

        fn handle_reply_channel_range(&self, _their_node_id: &PublicKey, _msg: ReplyChannelRange) -> Result<(), LightningError> {
                // We don't make queries, so should never receive replies. If, in the future, the set
                // reconciliation extensions to gossip queries become broadly supported, we should revert
                // this code to its state pre-0.0.106.
                Ok(())
        }

        fn handle_reply_short_channel_ids_end(&self, _their_node_id: &PublicKey, _msg: ReplyShortChannelIdsEnd) -> Result<(), LightningError> {
                // We don't make queries, so should never receive replies. If, in the future, the set
                // reconciliation extensions to gossip queries become broadly supported, we should revert
                // this code to its state pre-0.0.106.
                Ok(())
        }

        /// Processes a query from a peer by finding announced/public channels whose funding UTXOs
        /// are in the specified block range. Due to message size limits, large range
        /// queries may result in several reply messages. This implementation enqueues
        /// all reply messages into pending events. Each message will allocate just under 65KiB. A full
        /// sync of the public routing table with 128k channels will generated 16 messages and allocate ~1MB.
        /// Logic can be changed to reduce allocation if/when a full sync of the routing table impacts
        /// memory constrained systems.
        fn handle_query_channel_range(&self, their_node_id: &PublicKey, msg: QueryChannelRange) -> Result<(), LightningError> {
                log_debug!(self.logger, "Handling query_channel_range peer={}, first_blocknum={}, number_of_blocks={}", log_pubkey!(their_node_id), msg.first_blocknum, msg.number_of_blocks);

                let inclusive_start_scid = scid_from_parts(msg.first_blocknum as u64, 0, 0);

                // We might receive valid queries with end_blocknum that would overflow SCID conversion.
                // If so, we manually cap the ending block to avoid this overflow.
                let exclusive_end_scid = scid_from_parts(cmp::min(msg.end_blocknum() as u64, MAX_SCID_BLOCK), 0, 0);

                // Per spec, we must reply to a query. Send an empty message when things are invalid.
                if msg.chain_hash != self.network_graph.chain_hash || inclusive_start_scid.is_err() || exclusive_end_scid.is_err() || msg.number_of_blocks == 0 {
                        let mut pending_events = self.pending_events.lock().unwrap();
                        pending_events.push(MessageSendEvent::SendReplyChannelRange {
                                node_id: their_node_id.clone(),
                                msg: ReplyChannelRange {
                                        chain_hash: msg.chain_hash.clone(),
                                        first_blocknum: msg.first_blocknum,
                                        number_of_blocks: msg.number_of_blocks,
                                        sync_complete: true,
                                        short_channel_ids: vec![],
                                }
                        });
                        return Err(LightningError {
                                err: String::from("query_channel_range could not be processed"),
                                action: ErrorAction::IgnoreError,
                        });
                }

                // Creates channel batches. We are not checking if the channel is routable
                // (has at least one update). A peer may still want to know the channel
                // exists even if its not yet routable.
                let mut batches: Vec<Vec<u64>> = vec![Vec::with_capacity(MAX_SCIDS_PER_REPLY)];
                let mut channels = self.network_graph.channels.write().unwrap();
                for (_, ref chan) in channels.range(inclusive_start_scid.unwrap()..exclusive_end_scid.unwrap()) {
                        if let Some(chan_announcement) = &chan.announcement_message {
                                // Construct a new batch if last one is full
                                if batches.last().unwrap().len() == batches.last().unwrap().capacity() {
                                        batches.push(Vec::with_capacity(MAX_SCIDS_PER_REPLY));
                                }

                                let batch = batches.last_mut().unwrap();
                                batch.push(chan_announcement.contents.short_channel_id);
                        }
                }
                drop(channels);

                let mut pending_events = self.pending_events.lock().unwrap();
                let batch_count = batches.len();
                let mut prev_batch_endblock = msg.first_blocknum;
                for (batch_index, batch) in batches.into_iter().enumerate() {
                        // Per spec, the initial `first_blocknum` needs to be <= the query's `first_blocknum`
                        // and subsequent `first_blocknum`s must be >= the prior reply's `first_blocknum`.
                        //
                        // Additionally, c-lightning versions < 0.10 require that the `first_blocknum` of each
                        // reply is >= the previous reply's `first_blocknum` and either exactly the previous
                        // reply's `first_blocknum + number_of_blocks` or exactly one greater. This is a
                        // significant diversion from the requirements set by the spec, and, in case of blocks
                        // with no channel opens (e.g. empty blocks), requires that we use the previous value
                        // and *not* derive the first_blocknum from the actual first block of the reply.
                        let first_blocknum = prev_batch_endblock;

                        // Each message carries the number of blocks (from the `first_blocknum`) its contents
                        // fit in. Though there is no requirement that we use exactly the number of blocks its
                        // contents are from, except for the bogus requirements c-lightning enforces, above.
                        //
                        // Per spec, the last end block (ie `first_blocknum + number_of_blocks`) needs to be
                        // >= the query's end block. Thus, for the last reply, we calculate the difference
                        // between the query's end block and the start of the reply.
                        //
                        // Overflow safe since end_blocknum=msg.first_block_num+msg.number_of_blocks and
                        // first_blocknum will be either msg.first_blocknum or a higher block height.
                        let (sync_complete, number_of_blocks) = if batch_index == batch_count-1 {
                                (true, msg.end_blocknum() - first_blocknum)
                        }
                        // Prior replies should use the number of blocks that fit into the reply. Overflow
                        // safe since first_blocknum is always <= last SCID's block.
                        else {
                                (false, block_from_scid(batch.last().unwrap()) - first_blocknum)
                        };

                        prev_batch_endblock = first_blocknum + number_of_blocks;

                        pending_events.push(MessageSendEvent::SendReplyChannelRange {
                                node_id: their_node_id.clone(),
                                msg: ReplyChannelRange {
                                        chain_hash: msg.chain_hash.clone(),
                                        first_blocknum,
                                        number_of_blocks,
                                        sync_complete,
                                        short_channel_ids: batch,
                                }
                        });
                }

                Ok(())
        }

        fn handle_query_short_channel_ids(&self, _their_node_id: &PublicKey, _msg: QueryShortChannelIds) -> Result<(), LightningError> {
                // TODO
                Err(LightningError {
                        err: String::from("Not implemented"),
                        action: ErrorAction::IgnoreError,
                })
        }

        fn provided_node_features(&self) -> NodeFeatures {
                let mut features = NodeFeatures::empty();
                features.set_gossip_queries_optional();
                features
        }

        fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
                let mut features = InitFeatures::empty();
                features.set_gossip_queries_optional();
                features
        }

        fn processing_queue_high(&self) -> bool {
                self.network_graph.pending_checks.too_many_checks_pending()
        }
}

impl<G: Deref<Target=NetworkGraph<L>>, U: Deref, L: Deref> MessageSendEventsProvider for P2PGossipSync<G, U, L>
where
        U::Target: UtxoLookup,
        L::Target: Logger,
{
        fn get_and_clear_pending_msg_events(&self) -> Vec<MessageSendEvent> {
                let mut ret = Vec::new();
                let mut pending_events = self.pending_events.lock().unwrap();
                core::mem::swap(&mut ret, &mut pending_events);
                ret
        }
}

#[derive(Clone, Debug, PartialEq, Eq)]
/// Details about one direction of a channel as received within a [`ChannelUpdate`].
pub struct ChannelUpdateInfo {
        /// When the last update to the channel direction was issued.
        /// Value is opaque, as set in the announcement.
        pub last_update: u32,
        /// Whether the channel can be currently used for payments (in this one direction).
        pub enabled: bool,
        /// The difference in CLTV values that you must have when routing through this channel.
        pub cltv_expiry_delta: u16,
        /// The minimum value, which must be relayed to the next hop via the channel
        pub htlc_minimum_msat: u64,
        /// The maximum value which may be relayed to the next hop via the channel.
        pub htlc_maximum_msat: u64,
        /// Fees charged when the channel is used for routing
        pub fees: RoutingFees,
        /// Most recent update for the channel received from the network
        /// Mostly redundant with the data we store in fields explicitly.
        /// Everything else is useful only for sending out for initial routing sync.
        /// Not stored if contains excess data to prevent DoS.
        pub last_update_message: Option<ChannelUpdate>,
}

impl fmt::Display for ChannelUpdateInfo {
        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
                write!(f, "last_update {}, enabled {}, cltv_expiry_delta {}, htlc_minimum_msat {}, fees {:?}", self.last_update, self.enabled, self.cltv_expiry_delta, self.htlc_minimum_msat, self.fees)?;
                Ok(())
        }
}

impl Writeable for ChannelUpdateInfo {
        fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                write_tlv_fields!(writer, {
                        (0, self.last_update, required),
                        (2, self.enabled, required),
                        (4, self.cltv_expiry_delta, required),
                        (6, self.htlc_minimum_msat, required),
                        // Writing htlc_maximum_msat as an Option<u64> is required to maintain backwards
                        // compatibility with LDK versions prior to v0.0.110.
                        (8, Some(self.htlc_maximum_msat), required),
                        (10, self.fees, required),
                        (12, self.last_update_message, required),
                });
                Ok(())
        }
}

impl Readable for ChannelUpdateInfo {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                _init_tlv_field_var!(last_update, required);
                _init_tlv_field_var!(enabled, required);
                _init_tlv_field_var!(cltv_expiry_delta, required);
                _init_tlv_field_var!(htlc_minimum_msat, required);
                _init_tlv_field_var!(htlc_maximum_msat, option);
                _init_tlv_field_var!(fees, required);
                _init_tlv_field_var!(last_update_message, required);

                read_tlv_fields!(reader, {
                        (0, last_update, required),
                        (2, enabled, required),
                        (4, cltv_expiry_delta, required),
                        (6, htlc_minimum_msat, required),
                        (8, htlc_maximum_msat, required),
                        (10, fees, required),
                        (12, last_update_message, required)
                });

                if let Some(htlc_maximum_msat) = htlc_maximum_msat {
                        Ok(ChannelUpdateInfo {
                                last_update: _init_tlv_based_struct_field!(last_update, required),
                                enabled: _init_tlv_based_struct_field!(enabled, required),
                                cltv_expiry_delta: _init_tlv_based_struct_field!(cltv_expiry_delta, required),
                                htlc_minimum_msat: _init_tlv_based_struct_field!(htlc_minimum_msat, required),
                                htlc_maximum_msat,
                                fees: _init_tlv_based_struct_field!(fees, required),
                                last_update_message: _init_tlv_based_struct_field!(last_update_message, required),
                        })
                } else {
                        Err(DecodeError::InvalidValue)
                }
        }
}

#[derive(Clone, Debug, Eq)]
/// Details about a channel (both directions).
/// Received within a channel announcement.
pub struct ChannelInfo {
        /// Protocol features of a channel communicated during its announcement
        pub features: ChannelFeatures,
        /// Source node of the first direction of a channel
        pub node_one: NodeId,
        /// Details about the first direction of a channel
        pub one_to_two: Option<ChannelUpdateInfo>,
        /// Source node of the second direction of a channel
        pub node_two: NodeId,
        /// Details about the second direction of a channel
        pub two_to_one: Option<ChannelUpdateInfo>,
        /// The channel capacity as seen on-chain, if chain lookup is available.
        pub capacity_sats: Option<u64>,
        /// An initial announcement of the channel
        /// Mostly redundant with the data we store in fields explicitly.
        /// Everything else is useful only for sending out for initial routing sync.
        /// Not stored if contains excess data to prevent DoS.
        pub announcement_message: Option<ChannelAnnouncement>,
        /// The timestamp when we received the announcement, if we are running with feature = "std"
        /// (which we can probably assume we are - no-std environments probably won't have a full
        /// network graph in memory!).
        announcement_received_time: u64,

        /// The [`NodeInfo::node_counter`] of the node pointed to by [`Self::node_one`].
        pub(crate) node_one_counter: u32,
        /// The [`NodeInfo::node_counter`] of the node pointed to by [`Self::node_two`].
        pub(crate) node_two_counter: u32,
}

impl PartialEq for ChannelInfo {
        fn eq(&self, o: &ChannelInfo) -> bool {
                self.features == o.features &&
                        self.node_one == o.node_one &&
                        self.one_to_two == o.one_to_two &&
                        self.node_two == o.node_two &&
                        self.two_to_one == o.two_to_one &&
                        self.capacity_sats == o.capacity_sats &&
                        self.announcement_message == o.announcement_message &&
                        self.announcement_received_time == o.announcement_received_time
        }
}

impl ChannelInfo {
        /// Returns a [`DirectedChannelInfo`] for the channel directed to the given `target` from a
        /// returned `source`, or `None` if `target` is not one of the channel's counterparties.
        pub fn as_directed_to(&self, target: &NodeId) -> Option<(DirectedChannelInfo, &NodeId)> {
                let (direction, source, outbound) = {
                        if target == &self.node_one {
                                (self.two_to_one.as_ref(), &self.node_two, false)
                        } else if target == &self.node_two {
                                (self.one_to_two.as_ref(), &self.node_one, true)
                        } else {
                                return None;
                        }
                };
                direction.map(|dir| (DirectedChannelInfo::new(self, dir, outbound), source))
        }

        /// Returns a [`DirectedChannelInfo`] for the channel directed from the given `source` to a
        /// returned `target`, or `None` if `source` is not one of the channel's counterparties.
        pub fn as_directed_from(&self, source: &NodeId) -> Option<(DirectedChannelInfo, &NodeId)> {
                let (direction, target, outbound) = {
                        if source == &self.node_one {
                                (self.one_to_two.as_ref(), &self.node_two, true)
                        } else if source == &self.node_two {
                                (self.two_to_one.as_ref(), &self.node_one, false)
                        } else {
                                return None;
                        }
                };
                direction.map(|dir| (DirectedChannelInfo::new(self, dir, outbound), target))
        }

        /// Returns a [`ChannelUpdateInfo`] based on the direction implied by the channel_flag.
        pub fn get_directional_info(&self, channel_flags: u8) -> Option<&ChannelUpdateInfo> {
                let direction = channel_flags & 1u8;
                if direction == 0 {
                        self.one_to_two.as_ref()
                } else {
                        self.two_to_one.as_ref()
                }
        }
}

impl fmt::Display for ChannelInfo {
        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
                write!(f, "features: {}, node_one: {}, one_to_two: {:?}, node_two: {}, two_to_one: {:?}",
                   log_bytes!(self.features.encode()), &self.node_one, self.one_to_two, &self.node_two, self.two_to_one)?;
                Ok(())
        }
}

impl Writeable for ChannelInfo {
        fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                write_tlv_fields!(writer, {
                        (0, self.features, required),
                        (1, self.announcement_received_time, (default_value, 0)),
                        (2, self.node_one, required),
                        (4, self.one_to_two, required),
                        (6, self.node_two, required),
                        (8, self.two_to_one, required),
                        (10, self.capacity_sats, required),
                        (12, self.announcement_message, required),
                });
                Ok(())
        }
}

// A wrapper allowing for the optional deseralization of ChannelUpdateInfo. Utilizing this is
// necessary to maintain backwards compatibility with previous serializations of `ChannelUpdateInfo`
// that may have no `htlc_maximum_msat` field set. In case the field is absent, we simply ignore
// the error and continue reading the `ChannelInfo`. Hopefully, we'll then eventually receive newer
// channel updates via the gossip network.
struct ChannelUpdateInfoDeserWrapper(Option<ChannelUpdateInfo>);

impl MaybeReadable for ChannelUpdateInfoDeserWrapper {
        fn read<R: io::Read>(reader: &mut R) -> Result<Option<Self>, DecodeError> {
                match crate::util::ser::Readable::read(reader) {
                        Ok(channel_update_option) => Ok(Some(Self(channel_update_option))),
                        Err(DecodeError::ShortRead) => Ok(None),
                        Err(DecodeError::InvalidValue) => Ok(None),
                        Err(err) => Err(err),
                }
        }
}

impl Readable for ChannelInfo {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                _init_tlv_field_var!(features, required);
                _init_tlv_field_var!(announcement_received_time, (default_value, 0));
                _init_tlv_field_var!(node_one, required);
                let mut one_to_two_wrap: Option<ChannelUpdateInfoDeserWrapper> = None;
                _init_tlv_field_var!(node_two, required);
                let mut two_to_one_wrap: Option<ChannelUpdateInfoDeserWrapper> = None;
                _init_tlv_field_var!(capacity_sats, required);
                _init_tlv_field_var!(announcement_message, required);
                read_tlv_fields!(reader, {
                        (0, features, required),
                        (1, announcement_received_time, (default_value, 0)),
                        (2, node_one, required),
                        (4, one_to_two_wrap, upgradable_option),
                        (6, node_two, required),
                        (8, two_to_one_wrap, upgradable_option),
                        (10, capacity_sats, required),
                        (12, announcement_message, required),
                });

                Ok(ChannelInfo {
                        features: _init_tlv_based_struct_field!(features, required),
                        node_one: _init_tlv_based_struct_field!(node_one, required),
                        one_to_two: one_to_two_wrap.map(|w| w.0).unwrap_or(None),
                        node_two: _init_tlv_based_struct_field!(node_two, required),
                        two_to_one: two_to_one_wrap.map(|w| w.0).unwrap_or(None),
                        capacity_sats: _init_tlv_based_struct_field!(capacity_sats, required),
                        announcement_message: _init_tlv_based_struct_field!(announcement_message, required),
                        announcement_received_time: _init_tlv_based_struct_field!(announcement_received_time, (default_value, 0)),
                        node_one_counter: u32::max_value(),
                        node_two_counter: u32::max_value(),
                })
        }
}

/// A wrapper around [`ChannelInfo`] representing information about the channel as directed from a
/// source node to a target node.
#[derive(Clone)]
pub struct DirectedChannelInfo<'a> {
        channel: &'a ChannelInfo,
        direction: &'a ChannelUpdateInfo,
        /// The direction this channel is in - if set, it indicates that we're traversing the channel
        /// from [`ChannelInfo::node_one`] to [`ChannelInfo::node_two`].
        from_node_one: bool,
}

impl<'a> DirectedChannelInfo<'a> {
        #[inline]
        fn new(channel: &'a ChannelInfo, direction: &'a ChannelUpdateInfo, from_node_one: bool) -> Self {
                Self { channel, direction, from_node_one }
        }

        /// Returns information for the channel.
        #[inline]
        pub fn channel(&self) -> &'a ChannelInfo { self.channel }

        /// Returns the [`EffectiveCapacity`] of the channel in the direction.
        ///
        /// This is either the total capacity from the funding transaction, if known, or the
        /// `htlc_maximum_msat` for the direction as advertised by the gossip network, if known,
        /// otherwise.
        #[inline]
        pub fn effective_capacity(&self) -> EffectiveCapacity {
                let mut htlc_maximum_msat = self.direction().htlc_maximum_msat;
                let capacity_msat = self.channel.capacity_sats.map(|capacity_sats| capacity_sats * 1000);

                match capacity_msat {
                        Some(capacity_msat) => {
                                htlc_maximum_msat = cmp::min(htlc_maximum_msat, capacity_msat);
                                EffectiveCapacity::Total { capacity_msat, htlc_maximum_msat }
                        },
                        None => EffectiveCapacity::AdvertisedMaxHTLC { amount_msat: htlc_maximum_msat },
                }
        }

        /// Returns information for the direction.
        #[inline]
        pub(super) fn direction(&self) -> &'a ChannelUpdateInfo { self.direction }

        /// Returns the `node_id` of the source hop.
        ///
        /// Refers to the `node_id` forwarding the payment to the next hop.
        #[inline]
        pub(super) fn source(&self) -> &'a NodeId { if self.from_node_one { &self.channel.node_one } else { &self.channel.node_two } }

        /// Returns the `node_id` of the target hop.
        ///
        /// Refers to the `node_id` receiving the payment from the previous hop.
        #[inline]
        pub(super) fn target(&self) -> &'a NodeId { if self.from_node_one { &self.channel.node_two } else { &self.channel.node_one } }

        /// Returns the source node's counter
        #[inline]
        pub(super) fn source_counter(&self) -> u32 { if self.from_node_one { self.channel.node_one_counter } else { self.channel.node_two_counter } }

        /// Returns the target node's counter
        #[inline]
        pub(super) fn target_counter(&self) -> u32 { if self.from_node_one { self.channel.node_two_counter } else { self.channel.node_one_counter } }
}

impl<'a> fmt::Debug for DirectedChannelInfo<'a> {
        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
                f.debug_struct("DirectedChannelInfo")
                        .field("channel", &self.channel)
                        .finish()
        }
}

/// The effective capacity of a channel for routing purposes.
///
/// While this may be smaller than the actual channel capacity, amounts greater than
/// [`Self::as_msat`] should not be routed through the channel.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum EffectiveCapacity {
        /// The available liquidity in the channel known from being a channel counterparty, and thus a
        /// direct hop.
        ExactLiquidity {
                /// Either the inbound or outbound liquidity depending on the direction, denominated in
                /// millisatoshi.
                liquidity_msat: u64,
        },
        /// The maximum HTLC amount in one direction as advertised on the gossip network.
        AdvertisedMaxHTLC {
                /// The maximum HTLC amount denominated in millisatoshi.
                amount_msat: u64,
        },
        /// The total capacity of the channel as determined by the funding transaction.
        Total {
                /// The funding amount denominated in millisatoshi.
                capacity_msat: u64,
                /// The maximum HTLC amount denominated in millisatoshi.
                htlc_maximum_msat: u64
        },
        /// A capacity sufficient to route any payment, typically used for private channels provided by
        /// an invoice.
        Infinite,
        /// The maximum HTLC amount as provided by an invoice route hint.
        HintMaxHTLC {
                /// The maximum HTLC amount denominated in millisatoshi.
                amount_msat: u64,
        },
        /// A capacity that is unknown possibly because either the chain state is unavailable to know
        /// the total capacity or the `htlc_maximum_msat` was not advertised on the gossip network.
        Unknown,
}

/// The presumed channel capacity denominated in millisatoshi for [`EffectiveCapacity::Unknown`] to
/// use when making routing decisions.
pub const UNKNOWN_CHANNEL_CAPACITY_MSAT: u64 = 250_000 * 1000;

impl EffectiveCapacity {
        /// Returns the effective capacity denominated in millisatoshi.
        pub fn as_msat(&self) -> u64 {
                match self {
                        EffectiveCapacity::ExactLiquidity { liquidity_msat } => *liquidity_msat,
                        EffectiveCapacity::AdvertisedMaxHTLC { amount_msat } => *amount_msat,
                        EffectiveCapacity::Total { capacity_msat, .. } => *capacity_msat,
                        EffectiveCapacity::HintMaxHTLC { amount_msat } => *amount_msat,
                        EffectiveCapacity::Infinite => u64::max_value(),
                        EffectiveCapacity::Unknown => UNKNOWN_CHANNEL_CAPACITY_MSAT,
                }
        }
}

/// Fees for routing via a given channel or a node
#[derive(Eq, PartialEq, Copy, Clone, Debug, Hash, Ord, PartialOrd)]
pub struct RoutingFees {
        /// Flat routing fee in millisatoshis.
        pub base_msat: u32,
        /// Liquidity-based routing fee in millionths of a routed amount.
        /// In other words, 10000 is 1%.
        pub proportional_millionths: u32,
}

impl_writeable_tlv_based!(RoutingFees, {
        (0, base_msat, required),
        (2, proportional_millionths, required)
});

#[derive(Clone, Debug, PartialEq, Eq)]
/// Information received in the latest node_announcement from this node.
pub struct NodeAnnouncementInfo {
        /// Protocol features the node announced support for
        pub features: NodeFeatures,
        /// When the last known update to the node state was issued.
        /// Value is opaque, as set in the announcement.
        pub last_update: u32,
        /// Color assigned to the node
        pub rgb: [u8; 3],
        /// Moniker assigned to the node.
        /// May be invalid or malicious (eg control chars),
        /// should not be exposed to the user.
        pub alias: NodeAlias,
        /// An initial announcement of the node
        /// Mostly redundant with the data we store in fields explicitly.
        /// Everything else is useful only for sending out for initial routing sync.
        /// Not stored if contains excess data to prevent DoS.
        pub announcement_message: Option<NodeAnnouncement>
}

impl NodeAnnouncementInfo {
        /// Internet-level addresses via which one can connect to the node
        pub fn addresses(&self) -> &[SocketAddress] {
                self.announcement_message.as_ref()
                        .map(|msg| msg.contents.addresses.as_slice())
                        .unwrap_or_default()
        }
}

impl Writeable for NodeAnnouncementInfo {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                let empty_addresses = Vec::<SocketAddress>::new();
                write_tlv_fields!(writer, {
                        (0, self.features, required),
                        (2, self.last_update, required),
                        (4, self.rgb, required),
                        (6, self.alias, required),
                        (8, self.announcement_message, option),
                        (10, empty_addresses, required_vec), // Versions prior to 0.0.115 require this field
                });
                Ok(())
        }
}

impl Readable for NodeAnnouncementInfo {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                _init_and_read_len_prefixed_tlv_fields!(reader, {
                        (0, features, required),
                        (2, last_update, required),
                        (4, rgb, required),
                        (6, alias, required),
                        (8, announcement_message, option),
                        (10, _addresses, optional_vec), // deprecated, not used anymore
                });
                let _: Option<Vec<SocketAddress>> = _addresses;
                Ok(Self { features: features.0.unwrap(), last_update: last_update.0.unwrap(), rgb: rgb.0.unwrap(),
                        alias: alias.0.unwrap(), announcement_message })
        }
}

/// A user-defined name for a node, which may be used when displaying the node in a graph.
///
/// Since node aliases are provided by third parties, they are a potential avenue for injection
/// attacks. Care must be taken when processing.
#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
pub struct NodeAlias(pub [u8; 32]);

impl fmt::Display for NodeAlias {
        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
                let first_null = self.0.iter().position(|b| *b == 0).unwrap_or(self.0.len());
                let bytes = self.0.split_at(first_null).0;
                match core::str::from_utf8(bytes) {
                        Ok(alias) => PrintableString(alias).fmt(f)?,
                        Err(_) => {
                                use core::fmt::Write;
                                for c in bytes.iter().map(|b| *b as char) {
                                        // Display printable ASCII characters
                                        let control_symbol = core::char::REPLACEMENT_CHARACTER;
                                        let c = if c >= '\x20' && c <= '\x7e' { c } else { control_symbol };
                                        f.write_char(c)?;
                                }
                        },
                };
                Ok(())
        }
}

impl Writeable for NodeAlias {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
                self.0.write(w)
        }
}

impl Readable for NodeAlias {
        fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                Ok(NodeAlias(Readable::read(r)?))
        }
}

#[derive(Clone, Debug, Eq)]
/// Details about a node in the network, known from the network announcement.
pub struct NodeInfo {
        /// All valid channels a node has announced
        pub channels: Vec<u64>,
        /// More information about a node from node_announcement.
        /// Optional because we store a Node entry after learning about it from
        /// a channel announcement, but before receiving a node announcement.
        pub announcement_info: Option<NodeAnnouncementInfo>,
        /// In memory, each node is assigned a unique ID. They are eagerly reused, ensuring they remain
        /// relatively dense.
        ///
        /// These IDs allow the router to avoid a `HashMap` lookup by simply using this value as an
        /// index in a `Vec`, skipping a big step in some of the hottest code when routing.
        pub(crate) node_counter: u32,
}

impl PartialEq for NodeInfo {
        fn eq(&self, o: &NodeInfo) -> bool {
                self.channels == o.channels && self.announcement_info == o.announcement_info
        }
}

impl fmt::Display for NodeInfo {
        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
                write!(f, " channels: {:?}, announcement_info: {:?}",
                        &self.channels[..], self.announcement_info)?;
                Ok(())
        }
}

impl Writeable for NodeInfo {
        fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                write_tlv_fields!(writer, {
                        // Note that older versions of LDK wrote the lowest inbound fees here at type 0
                        (2, self.announcement_info, option),
                        (4, self.channels, required_vec),
                });
                Ok(())
        }
}

// A wrapper allowing for the optional deserialization of `NodeAnnouncementInfo`. Utilizing this is
// necessary to maintain compatibility with previous serializations of `SocketAddress` that have an
// invalid hostname set. We ignore and eat all errors until we are either able to read a
// `NodeAnnouncementInfo` or hit a `ShortRead`, i.e., read the TLV field to the end.
struct NodeAnnouncementInfoDeserWrapper(NodeAnnouncementInfo);

impl MaybeReadable for NodeAnnouncementInfoDeserWrapper {
        fn read<R: io::Read>(reader: &mut R) -> Result<Option<Self>, DecodeError> {
                match crate::util::ser::Readable::read(reader) {
                        Ok(node_announcement_info) => return Ok(Some(Self(node_announcement_info))),
                        Err(_) => {
                                copy(reader, &mut sink()).unwrap();
                                return Ok(None)
                        },
                };
        }
}

impl Readable for NodeInfo {
        fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                // Historically, we tracked the lowest inbound fees for any node in order to use it as an
                // A* heuristic when routing. Sadly, these days many, many nodes have at least one channel
                // with zero inbound fees, causing that heuristic to provide little gain. Worse, because it
                // requires additional complexity and lookups during routing, it ends up being a
                // performance loss. Thus, we simply ignore the old field here and no longer track it.
                _init_and_read_len_prefixed_tlv_fields!(reader, {
                        (0, _lowest_inbound_channel_fees, option),
                        (2, announcement_info_wrap, upgradable_option),
                        (4, channels, required_vec),
                });
                let _: Option<RoutingFees> = _lowest_inbound_channel_fees;
                let announcement_info_wrap: Option<NodeAnnouncementInfoDeserWrapper> = announcement_info_wrap;

                Ok(NodeInfo {
                        announcement_info: announcement_info_wrap.map(|w| w.0),
                        channels,
                        node_counter: u32::max_value(),
                })
        }
}

const SERIALIZATION_VERSION: u8 = 1;
const MIN_SERIALIZATION_VERSION: u8 = 1;

impl<L: Deref> Writeable for NetworkGraph<L> where L::Target: Logger {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                self.test_node_counter_consistency();

                write_ver_prefix!(writer, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);

                self.chain_hash.write(writer)?;
                let channels = self.channels.read().unwrap();
                (channels.len() as u64).write(writer)?;
                for (ref chan_id, ref chan_info) in channels.unordered_iter() {
                        (*chan_id).write(writer)?;
                        chan_info.write(writer)?;
                }
                let nodes = self.nodes.read().unwrap();
                (nodes.len() as u64).write(writer)?;
                for (ref node_id, ref node_info) in nodes.unordered_iter() {
                        node_id.write(writer)?;
                        node_info.write(writer)?;
                }

                let last_rapid_gossip_sync_timestamp = self.get_last_rapid_gossip_sync_timestamp();
                write_tlv_fields!(writer, {
                        (1, last_rapid_gossip_sync_timestamp, option),
                });
                Ok(())
        }
}

impl<L: Deref> ReadableArgs<L> for NetworkGraph<L> where L::Target: Logger {
        fn read<R: io::Read>(reader: &mut R, logger: L) -> Result<NetworkGraph<L>, DecodeError> {
                let _ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);

                let chain_hash: ChainHash = Readable::read(reader)?;
                let channels_count: u64 = Readable::read(reader)?;
                // In Nov, 2023 there were about 15,000 nodes; we cap allocations to 1.5x that.
                let mut channels = IndexedMap::with_capacity(cmp::min(channels_count as usize, 22500));
                for _ in 0..channels_count {
                        let chan_id: u64 = Readable::read(reader)?;
                        let chan_info: ChannelInfo = Readable::read(reader)?;
                        channels.insert(chan_id, chan_info);
                }
                let nodes_count: u64 = Readable::read(reader)?;
                if nodes_count > u32::max_value() as u64 / 2 { return Err(DecodeError::InvalidValue); }
                // In Nov, 2023 there were about 69K channels; we cap allocations to 1.5x that.
                let mut nodes = IndexedMap::with_capacity(cmp::min(nodes_count as usize, 103500));
                for i in 0..nodes_count {
                        let node_id = Readable::read(reader)?;
                        let mut node_info: NodeInfo = Readable::read(reader)?;
                        node_info.node_counter = i as u32;
                        nodes.insert(node_id, node_info);
                }

                for (_, chan) in channels.unordered_iter_mut() {
                        chan.node_one_counter =
                                nodes.get(&chan.node_one).ok_or(DecodeError::InvalidValue)?.node_counter;
                        chan.node_two_counter =
                                nodes.get(&chan.node_two).ok_or(DecodeError::InvalidValue)?.node_counter;
                }

                let mut last_rapid_gossip_sync_timestamp: Option<u32> = None;
                read_tlv_fields!(reader, {
                        (1, last_rapid_gossip_sync_timestamp, option),
                });

                Ok(NetworkGraph {
                        secp_ctx: Secp256k1::verification_only(),
                        chain_hash,
                        logger,
                        channels: RwLock::new(channels),
                        nodes: RwLock::new(nodes),
                        removed_node_counters: Mutex::new(Vec::new()),
                        next_node_counter: AtomicUsize::new(nodes_count as usize),
                        last_rapid_gossip_sync_timestamp: Mutex::new(last_rapid_gossip_sync_timestamp),
                        removed_nodes: Mutex::new(HashMap::new()),
                        removed_channels: Mutex::new(HashMap::new()),
                        pending_checks: utxo::PendingChecks::new(),
                })
        }
}

impl<L: Deref> fmt::Display for NetworkGraph<L> where L::Target: Logger {
        fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
                writeln!(f, "Network map\n[Channels]")?;
                for (key, val) in self.channels.read().unwrap().unordered_iter() {
                        writeln!(f, " {}: {}", key, val)?;
                }
                writeln!(f, "[Nodes]")?;
                for (&node_id, val) in self.nodes.read().unwrap().unordered_iter() {
                        writeln!(f, " {}: {}", &node_id, val)?;
                }
                Ok(())
        }
}

impl<L: Deref> Eq for NetworkGraph<L> where L::Target: Logger {}
impl<L: Deref> PartialEq for NetworkGraph<L> where L::Target: Logger {
        fn eq(&self, other: &Self) -> bool {
                // For a total lockorder, sort by position in memory and take the inner locks in that order.
                // (Assumes that we can't move within memory while a lock is held).
                let ord = ((self as *const _) as usize) < ((other as *const _) as usize);
                let a = if ord { (&self.channels, &self.nodes) } else { (&other.channels, &other.nodes) };
                let b = if ord { (&other.channels, &other.nodes) } else { (&self.channels, &self.nodes) };
                let (channels_a, channels_b) = (a.0.unsafe_well_ordered_double_lock_self(), b.0.unsafe_well_ordered_double_lock_self());
                let (nodes_a, nodes_b) = (a.1.unsafe_well_ordered_double_lock_self(), b.1.unsafe_well_ordered_double_lock_self());
                self.chain_hash.eq(&other.chain_hash) && channels_a.eq(&channels_b) && nodes_a.eq(&nodes_b)
        }
}

impl<L: Deref> NetworkGraph<L> where L::Target: Logger {
        /// Creates a new, empty, network graph.
        pub fn new(network: Network, logger: L) -> NetworkGraph<L> {
                Self {
                        secp_ctx: Secp256k1::verification_only(),
                        chain_hash: ChainHash::using_genesis_block(network),
                        logger,
                        channels: RwLock::new(IndexedMap::new()),
                        nodes: RwLock::new(IndexedMap::new()),
                        next_node_counter: AtomicUsize::new(0),
                        removed_node_counters: Mutex::new(Vec::new()),
                        last_rapid_gossip_sync_timestamp: Mutex::new(None),
                        removed_channels: Mutex::new(HashMap::new()),
                        removed_nodes: Mutex::new(HashMap::new()),
                        pending_checks: utxo::PendingChecks::new(),
                }
        }

        fn test_node_counter_consistency(&self) {
                #[cfg(debug_assertions)] {
                        let channels = self.channels.read().unwrap();
                        let nodes = self.nodes.read().unwrap();
                        let removed_node_counters = self.removed_node_counters.lock().unwrap();
                        let next_counter = self.next_node_counter.load(Ordering::Acquire);
                        assert!(next_counter < (u32::max_value() as usize) / 2);
                        let mut used_node_counters = vec![0u8; next_counter / 8 + 1];

                        for counter in removed_node_counters.iter() {
                                let pos = (*counter as usize) / 8;
                                let bit = 1 << (counter % 8);
                                assert_eq!(used_node_counters[pos] & bit, 0);
                                used_node_counters[pos] |= bit;
                        }
                        for (_, node) in nodes.unordered_iter() {
                                assert!((node.node_counter as usize) < next_counter);
                                let pos = (node.node_counter as usize) / 8;
                                let bit = 1 << (node.node_counter % 8);
                                assert_eq!(used_node_counters[pos] & bit, 0);
                                used_node_counters[pos] |= bit;
                        }

                        for (_, chan) in channels.unordered_iter() {
                                assert_eq!(chan.node_one_counter, nodes.get(&chan.node_one).unwrap().node_counter);
                                assert_eq!(chan.node_two_counter, nodes.get(&chan.node_two).unwrap().node_counter);
                        }
                }
        }

        /// Returns a read-only view of the network graph.
        pub fn read_only(&'_ self) -> ReadOnlyNetworkGraph<'_> {
                self.test_node_counter_consistency();
                let channels = self.channels.read().unwrap();
                let nodes = self.nodes.read().unwrap();
                ReadOnlyNetworkGraph {
                        channels,
                        nodes,
                        max_node_counter: (self.next_node_counter.load(Ordering::Acquire) as u32).saturating_sub(1),
                }
        }

        /// The unix timestamp provided by the most recent rapid gossip sync.
        /// It will be set by the rapid sync process after every sync completion.
        pub fn get_last_rapid_gossip_sync_timestamp(&self) -> Option<u32> {
                self.last_rapid_gossip_sync_timestamp.lock().unwrap().clone()
        }

        /// Update the unix timestamp provided by the most recent rapid gossip sync.
        /// This should be done automatically by the rapid sync process after every sync completion.
        pub fn set_last_rapid_gossip_sync_timestamp(&self, last_rapid_gossip_sync_timestamp: u32) {
                self.last_rapid_gossip_sync_timestamp.lock().unwrap().replace(last_rapid_gossip_sync_timestamp);
        }

        /// Clears the `NodeAnnouncementInfo` field for all nodes in the `NetworkGraph` for testing
        /// purposes.
        #[cfg(test)]
        pub fn clear_nodes_announcement_info(&self) {
                for node in self.nodes.write().unwrap().unordered_iter_mut() {
                        node.1.announcement_info = None;
                }
        }

        /// For an already known node (from channel announcements), update its stored properties from a
        /// given node announcement.
        ///
        /// You probably don't want to call this directly, instead relying on a P2PGossipSync's
        /// RoutingMessageHandler implementation to call it indirectly. This may be useful to accept
        /// routing messages from a source using a protocol other than the lightning P2P protocol.
        pub fn update_node_from_announcement(&self, msg: &msgs::NodeAnnouncement) -> Result<(), LightningError> {
                verify_node_announcement(msg, &self.secp_ctx)?;
                self.update_node_from_announcement_intern(&msg.contents, Some(&msg))
        }

        /// For an already known node (from channel announcements), update its stored properties from a
        /// given node announcement without verifying the associated signatures. Because we aren't
        /// given the associated signatures here we cannot relay the node announcement to any of our
        /// peers.
        pub fn update_node_from_unsigned_announcement(&self, msg: &msgs::UnsignedNodeAnnouncement) -> Result<(), LightningError> {
                self.update_node_from_announcement_intern(msg, None)
        }

        fn update_node_from_announcement_intern(&self, msg: &msgs::UnsignedNodeAnnouncement, full_msg: Option<&msgs::NodeAnnouncement>) -> Result<(), LightningError> {
                let mut nodes = self.nodes.write().unwrap();
                match nodes.get_mut(&msg.node_id) {
                        None => {
                                core::mem::drop(nodes);
                                self.pending_checks.check_hold_pending_node_announcement(msg, full_msg)?;
                                Err(LightningError{err: "No existing channels for node_announcement".to_owned(), action: ErrorAction::IgnoreError})
                        },
                        Some(node) => {
                                if let Some(node_info) = node.announcement_info.as_ref() {
                                        // The timestamp field is somewhat of a misnomer - the BOLTs use it to order
                                        // updates to ensure you always have the latest one, only vaguely suggesting
                                        // that it be at least the current time.
                                        if node_info.last_update  > msg.timestamp {
                                                return Err(LightningError{err: "Update older than last processed update".to_owned(), action: ErrorAction::IgnoreDuplicateGossip});
                                        } else if node_info.last_update  == msg.timestamp {
                                                return Err(LightningError{err: "Update had the same timestamp as last processed update".to_owned(), action: ErrorAction::IgnoreDuplicateGossip});
                                        }
                                }

                                let should_relay =
                                        msg.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY &&
                                        msg.excess_address_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY &&
                                        msg.excess_data.len() + msg.excess_address_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY;
                                node.announcement_info = Some(NodeAnnouncementInfo {
                                        features: msg.features.clone(),
                                        last_update: msg.timestamp,
                                        rgb: msg.rgb,
                                        alias: msg.alias,
                                        announcement_message: if should_relay { full_msg.cloned() } else { None },
                                });

                                Ok(())
                        }
                }
        }

        /// Store or update channel info from a channel announcement.
        ///
        /// You probably don't want to call this directly, instead relying on a [`P2PGossipSync`]'s
        /// [`RoutingMessageHandler`] implementation to call it indirectly. This may be useful to accept
        /// routing messages from a source using a protocol other than the lightning P2P protocol.
        ///
        /// If a [`UtxoLookup`] object is provided via `utxo_lookup`, it will be called to verify
        /// the corresponding UTXO exists on chain and is correctly-formatted.
        pub fn update_channel_from_announcement<U: Deref>(
                &self, msg: &msgs::ChannelAnnouncement, utxo_lookup: &Option<U>,
        ) -> Result<(), LightningError>
        where
                U::Target: UtxoLookup,
        {
                verify_channel_announcement(msg, &self.secp_ctx)?;
                self.update_channel_from_unsigned_announcement_intern(&msg.contents, Some(msg), utxo_lookup)
        }

        /// Store or update channel info from a channel announcement.
        ///
        /// You probably don't want to call this directly, instead relying on a [`P2PGossipSync`]'s
        /// [`RoutingMessageHandler`] implementation to call it indirectly. This may be useful to accept
        /// routing messages from a source using a protocol other than the lightning P2P protocol.
        ///
        /// This will skip verification of if the channel is actually on-chain.
        pub fn update_channel_from_announcement_no_lookup(
                &self, msg: &ChannelAnnouncement
        ) -> Result<(), LightningError> {
                self.update_channel_from_announcement::<&UtxoResolver>(msg, &None)
        }

        /// Store or update channel info from a channel announcement without verifying the associated
        /// signatures. Because we aren't given the associated signatures here we cannot relay the
        /// channel announcement to any of our peers.
        ///
        /// If a [`UtxoLookup`] object is provided via `utxo_lookup`, it will be called to verify
        /// the corresponding UTXO exists on chain and is correctly-formatted.
        pub fn update_channel_from_unsigned_announcement<U: Deref>(
                &self, msg: &msgs::UnsignedChannelAnnouncement, utxo_lookup: &Option<U>
        ) -> Result<(), LightningError>
        where
                U::Target: UtxoLookup,
        {
                self.update_channel_from_unsigned_announcement_intern(msg, None, utxo_lookup)
        }

        /// Update channel from partial announcement data received via rapid gossip sync
        ///
        /// `timestamp: u64`: Timestamp emulating the backdated original announcement receipt (by the
        /// rapid gossip sync server)
        ///
        /// All other parameters as used in [`msgs::UnsignedChannelAnnouncement`] fields.
        pub fn add_channel_from_partial_announcement(&self, short_channel_id: u64, timestamp: u64, features: ChannelFeatures, node_id_1: PublicKey, node_id_2: PublicKey) -> Result<(), LightningError> {
                if node_id_1 == node_id_2 {
                        return Err(LightningError{err: "Channel announcement node had a channel with itself".to_owned(), action: ErrorAction::IgnoreError});
                };

                let node_1 = NodeId::from_pubkey(&node_id_1);
                let node_2 = NodeId::from_pubkey(&node_id_2);
                let channel_info = ChannelInfo {
                        features,
                        node_one: node_1.clone(),
                        one_to_two: None,
                        node_two: node_2.clone(),
                        two_to_one: None,
                        capacity_sats: None,
                        announcement_message: None,
                        announcement_received_time: timestamp,
                        node_one_counter: u32::max_value(),
                        node_two_counter: u32::max_value(),
                };

                self.add_channel_between_nodes(short_channel_id, channel_info, None)
        }

        fn add_channel_between_nodes(&self, short_channel_id: u64, channel_info: ChannelInfo, utxo_value: Option<u64>) -> Result<(), LightningError> {
                let mut channels = self.channels.write().unwrap();
                let mut nodes = self.nodes.write().unwrap();

                let node_id_a = channel_info.node_one.clone();
                let node_id_b = channel_info.node_two.clone();

                log_gossip!(self.logger, "Adding channel {} between nodes {} and {}", short_channel_id, node_id_a, node_id_b);

                let channel_entry = channels.entry(short_channel_id);
                let channel_info = match channel_entry {
                        IndexedMapEntry::Occupied(mut entry) => {
                                //TODO: because asking the blockchain if short_channel_id is valid is only optional
                                //in the blockchain API, we need to handle it smartly here, though it's unclear
                                //exactly how...
                                if utxo_value.is_some() {
                                        // Either our UTXO provider is busted, there was a reorg, or the UTXO provider
                                        // only sometimes returns results. In any case remove the previous entry. Note
                                        // that the spec expects us to "blacklist" the node_ids involved, but we can't
                                        // do that because
                                        // a) we don't *require* a UTXO provider that always returns results.
                                        // b) we don't track UTXOs of channels we know about and remove them if they
                                        //    get reorg'd out.
                                        // c) it's unclear how to do so without exposing ourselves to massive DoS risk.
                                        self.remove_channel_in_nodes(&mut nodes, &entry.get(), short_channel_id);
                                        *entry.get_mut() = channel_info;
                                        entry.into_mut()
                                } else {
                                        return Err(LightningError{err: "Already have knowledge of channel".to_owned(), action: ErrorAction::IgnoreDuplicateGossip});
                                }
                        },
                        IndexedMapEntry::Vacant(entry) => {
                                entry.insert(channel_info)
                        }
                };

                let mut node_counter_id = [
                        (&mut channel_info.node_one_counter, node_id_a),
                        (&mut channel_info.node_two_counter, node_id_b)
                ];
                for (node_counter, current_node_id) in node_counter_id.iter_mut() {
                        match nodes.entry(current_node_id.clone()) {
                                IndexedMapEntry::Occupied(node_entry) => {
                                        let node = node_entry.into_mut();
                                        node.channels.push(short_channel_id);
                                        **node_counter = node.node_counter;
                                },
                                IndexedMapEntry::Vacant(node_entry) => {
                                        let mut removed_node_counters = self.removed_node_counters.lock().unwrap();
                                        **node_counter = removed_node_counters.pop()
                                                .unwrap_or(self.next_node_counter.fetch_add(1, Ordering::Relaxed) as u32);
                                        node_entry.insert(NodeInfo {
                                                channels: vec!(short_channel_id),
                                                announcement_info: None,
                                                node_counter: **node_counter,
                                        });
                                }
                        };
                };

                Ok(())
        }

        fn update_channel_from_unsigned_announcement_intern<U: Deref>(
                &self, msg: &msgs::UnsignedChannelAnnouncement, full_msg: Option<&msgs::ChannelAnnouncement>, utxo_lookup: &Option<U>
        ) -> Result<(), LightningError>
        where
                U::Target: UtxoLookup,
        {
                if msg.node_id_1 == msg.node_id_2 || msg.bitcoin_key_1 == msg.bitcoin_key_2 {
                        return Err(LightningError{err: "Channel announcement node had a channel with itself".to_owned(), action: ErrorAction::IgnoreError});
                }

                if msg.chain_hash != self.chain_hash {
                        return Err(LightningError {
                                err: "Channel announcement chain hash does not match genesis hash".to_owned(),
                                action: ErrorAction::IgnoreAndLog(Level::Debug),
                        });
                }

                {
                        let channels = self.channels.read().unwrap();

                        if let Some(chan) = channels.get(&msg.short_channel_id) {
                                if chan.capacity_sats.is_some() {
                                        // If we'd previously looked up the channel on-chain and checked the script
                                        // against what appears on-chain, ignore the duplicate announcement.
                                        //
                                        // Because a reorg could replace one channel with another at the same SCID, if
                                        // the channel appears to be different, we re-validate. This doesn't expose us
                                        // to any more DoS risk than not, as a peer can always flood us with
                                        // randomly-generated SCID values anyway.
                                        //
                                        // We use the Node IDs rather than the bitcoin_keys to check for "equivalence"
                                        // as we didn't (necessarily) store the bitcoin keys, and we only really care
                                        // if the peers on the channel changed anyway.
                                        if msg.node_id_1 == chan.node_one && msg.node_id_2 == chan.node_two {
                                                return Err(LightningError {
                                                        err: "Already have chain-validated channel".to_owned(),
                                                        action: ErrorAction::IgnoreDuplicateGossip
                                                });
                                        }
                                } else if utxo_lookup.is_none() {
                                        // Similarly, if we can't check the chain right now anyway, ignore the
                                        // duplicate announcement without bothering to take the channels write lock.
                                        return Err(LightningError {
                                                err: "Already have non-chain-validated channel".to_owned(),
                                                action: ErrorAction::IgnoreDuplicateGossip
                                        });
                                }
                        }
                }

                {
                        let removed_channels = self.removed_channels.lock().unwrap();
                        let removed_nodes = self.removed_nodes.lock().unwrap();
                        if removed_channels.contains_key(&msg.short_channel_id) ||
                                removed_nodes.contains_key(&msg.node_id_1) ||
                                removed_nodes.contains_key(&msg.node_id_2) {
                                return Err(LightningError{
                                        err: format!("Channel with SCID {} or one of its nodes was removed from our network graph recently", &msg.short_channel_id),
                                        action: ErrorAction::IgnoreAndLog(Level::Gossip)});
                        }
                }

                let utxo_value = self.pending_checks.check_channel_announcement(
                        utxo_lookup, msg, full_msg)?;

                #[allow(unused_mut, unused_assignments)]
                let mut announcement_received_time = 0;
                #[cfg(feature = "std")]
                {
                        announcement_received_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                }

                let chan_info = ChannelInfo {
                        features: msg.features.clone(),
                        node_one: msg.node_id_1,
                        one_to_two: None,
                        node_two: msg.node_id_2,
                        two_to_one: None,
                        capacity_sats: utxo_value,
                        announcement_message: if msg.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY
                                { full_msg.cloned() } else { None },
                        announcement_received_time,
                        node_one_counter: u32::max_value(),
                        node_two_counter: u32::max_value(),
                };

                self.add_channel_between_nodes(msg.short_channel_id, chan_info, utxo_value)?;

                log_gossip!(self.logger, "Added channel_announcement for {}{}", msg.short_channel_id, if !msg.excess_data.is_empty() { " with excess uninterpreted data!" } else { "" });
                Ok(())
        }

        /// Marks a channel in the graph as failed permanently.
        ///
        /// The channel and any node for which this was their last channel are removed from the graph.
        pub fn channel_failed_permanent(&self, short_channel_id: u64) {
                #[cfg(feature = "std")]
                let current_time_unix = Some(SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs());
                #[cfg(not(feature = "std"))]
                let current_time_unix = None;

                self.channel_failed_permanent_with_time(short_channel_id, current_time_unix)
        }

        /// Marks a channel in the graph as failed permanently.
        ///
        /// The channel and any node for which this was their last channel are removed from the graph.
        fn channel_failed_permanent_with_time(&self, short_channel_id: u64, current_time_unix: Option<u64>) {
                let mut channels = self.channels.write().unwrap();
                if let Some(chan) = channels.remove(&short_channel_id) {
                        let mut nodes = self.nodes.write().unwrap();
                        self.removed_channels.lock().unwrap().insert(short_channel_id, current_time_unix);
                        self.remove_channel_in_nodes(&mut nodes, &chan, short_channel_id);
                }
        }

        /// Marks a node in the graph as permanently failed, effectively removing it and its channels
        /// from local storage.
        pub fn node_failed_permanent(&self, node_id: &PublicKey) {
                #[cfg(feature = "std")]
                let current_time_unix = Some(SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs());
                #[cfg(not(feature = "std"))]
                let current_time_unix = None;

                let node_id = NodeId::from_pubkey(node_id);
                let mut channels = self.channels.write().unwrap();
                let mut nodes = self.nodes.write().unwrap();
                let mut removed_channels = self.removed_channels.lock().unwrap();
                let mut removed_nodes = self.removed_nodes.lock().unwrap();

                if let Some(node) = nodes.remove(&node_id) {
                        let mut removed_node_counters = self.removed_node_counters.lock().unwrap();
                        for scid in node.channels.iter() {
                                if let Some(chan_info) = channels.remove(scid) {
                                        let other_node_id = if node_id == chan_info.node_one { chan_info.node_two } else { chan_info.node_one };
                                        if let IndexedMapEntry::Occupied(mut other_node_entry) = nodes.entry(other_node_id) {
                                                other_node_entry.get_mut().channels.retain(|chan_id| {
                                                        *scid != *chan_id
                                                });
                                                if other_node_entry.get().channels.is_empty() {
                                                        removed_node_counters.push(other_node_entry.get().node_counter);
                                                        other_node_entry.remove_entry();
                                                }
                                        }
                                        removed_channels.insert(*scid, current_time_unix);
                                }
                        }
                        removed_node_counters.push(node.node_counter);
                        removed_nodes.insert(node_id, current_time_unix);
                }
        }

        #[cfg(feature = "std")]
        /// Removes information about channels that we haven't heard any updates about in some time.
        /// This can be used regularly to prune the network graph of channels that likely no longer
        /// exist.
        ///
        /// While there is no formal requirement that nodes regularly re-broadcast their channel
        /// updates every two weeks, the non-normative section of BOLT 7 currently suggests that
        /// pruning occur for updates which are at least two weeks old, which we implement here.
        ///
        /// Note that for users of the `lightning-background-processor` crate this method may be
        /// automatically called regularly for you.
        ///
        /// This method will also cause us to stop tracking removed nodes and channels if they have been
        /// in the map for a while so that these can be resynced from gossip in the future.
        ///
        /// This method is only available with the `std` feature. See
        /// [`NetworkGraph::remove_stale_channels_and_tracking_with_time`] for `no-std` use.
        pub fn remove_stale_channels_and_tracking(&self) {
                let time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                self.remove_stale_channels_and_tracking_with_time(time);
        }

        /// Removes information about channels that we haven't heard any updates about in some time.
        /// This can be used regularly to prune the network graph of channels that likely no longer
        /// exist.
        ///
        /// While there is no formal requirement that nodes regularly re-broadcast their channel
        /// updates every two weeks, the non-normative section of BOLT 7 currently suggests that
        /// pruning occur for updates which are at least two weeks old, which we implement here.
        ///
        /// This method will also cause us to stop tracking removed nodes and channels if they have been
        /// in the map for a while so that these can be resynced from gossip in the future.
        ///
        /// This function takes the current unix time as an argument. For users with the `std` feature
        /// enabled, [`NetworkGraph::remove_stale_channels_and_tracking`] may be preferable.
        pub fn remove_stale_channels_and_tracking_with_time(&self, current_time_unix: u64) {
                let mut channels = self.channels.write().unwrap();
                // Time out if we haven't received an update in at least 14 days.
                if current_time_unix > u32::max_value() as u64 { return; } // Remove by 2106
                if current_time_unix < STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS { return; }
                let min_time_unix: u32 = (current_time_unix - STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS) as u32;
                // Sadly BTreeMap::retain was only stabilized in 1.53 so we can't switch to it for some
                // time.
                let mut scids_to_remove = Vec::new();
                for (scid, info) in channels.unordered_iter_mut() {
                        if info.one_to_two.is_some() && info.one_to_two.as_ref().unwrap().last_update < min_time_unix {
                                log_gossip!(self.logger, "Removing directional update one_to_two (0) for channel {} due to its timestamp {} being below {}",
                                        scid, info.one_to_two.as_ref().unwrap().last_update, min_time_unix);
                                info.one_to_two = None;
                        }
                        if info.two_to_one.is_some() && info.two_to_one.as_ref().unwrap().last_update < min_time_unix {
                                log_gossip!(self.logger, "Removing directional update two_to_one (1) for channel {} due to its timestamp {} being below {}",
                                        scid, info.two_to_one.as_ref().unwrap().last_update, min_time_unix);
                                info.two_to_one = None;
                        }
                        if info.one_to_two.is_none() || info.two_to_one.is_none() {
                                // We check the announcement_received_time here to ensure we don't drop
                                // announcements that we just received and are just waiting for our peer to send a
                                // channel_update for.
                                let announcement_received_timestamp = info.announcement_received_time;
                                if announcement_received_timestamp < min_time_unix as u64 {
                                        log_gossip!(self.logger, "Removing channel {} because both directional updates are missing and its announcement timestamp {} being below {}",
                                                scid, announcement_received_timestamp, min_time_unix);
                                        scids_to_remove.push(*scid);
                                }
                        }
                }
                if !scids_to_remove.is_empty() {
                        let mut nodes = self.nodes.write().unwrap();
                        for scid in scids_to_remove {
                                let info = channels.remove(&scid).expect("We just accessed this scid, it should be present");
                                self.remove_channel_in_nodes(&mut nodes, &info, scid);
                                self.removed_channels.lock().unwrap().insert(scid, Some(current_time_unix));
                        }
                }

                let should_keep_tracking = |time: &mut Option<u64>| {
                        if let Some(time) = time {
                                current_time_unix.saturating_sub(*time) < REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS
                        } else {
                                // NOTE: In the case of no-std, we won't have access to the current UNIX time at the time of removal,
                                // so we'll just set the removal time here to the current UNIX time on the very next invocation
                                // of this function.
                                #[cfg(feature = "no-std")]
                                {
                                        let mut tracked_time = Some(current_time_unix);
                                        core::mem::swap(time, &mut tracked_time);
                                        return true;
                                }
                                #[allow(unreachable_code)]
                                false
                        }};

                self.removed_channels.lock().unwrap().retain(|_, time| should_keep_tracking(time));
                self.removed_nodes.lock().unwrap().retain(|_, time| should_keep_tracking(time));
        }

        /// For an already known (from announcement) channel, update info about one of the directions
        /// of the channel.
        ///
        /// You probably don't want to call this directly, instead relying on a [`P2PGossipSync`]'s
        /// [`RoutingMessageHandler`] implementation to call it indirectly. This may be useful to accept
        /// routing messages from a source using a protocol other than the lightning P2P protocol.
        ///
        /// If built with `no-std`, any updates with a timestamp more than two weeks in the past or
        /// materially in the future will be rejected.
        pub fn update_channel(&self, msg: &msgs::ChannelUpdate) -> Result<(), LightningError> {
                self.update_channel_internal(&msg.contents, Some(&msg), Some(&msg.signature), false)
        }

        /// For an already known (from announcement) channel, update info about one of the directions
        /// of the channel without verifying the associated signatures. Because we aren't given the
        /// associated signatures here we cannot relay the channel update to any of our peers.
        ///
        /// If built with `no-std`, any updates with a timestamp more than two weeks in the past or
        /// materially in the future will be rejected.
        pub fn update_channel_unsigned(&self, msg: &msgs::UnsignedChannelUpdate) -> Result<(), LightningError> {
                self.update_channel_internal(msg, None, None, false)
        }

        /// For an already known (from announcement) channel, verify the given [`ChannelUpdate`].
        ///
        /// This checks whether the update currently is applicable by [`Self::update_channel`].
        ///
        /// If built with `no-std`, any updates with a timestamp more than two weeks in the past or
        /// materially in the future will be rejected.
        pub fn verify_channel_update(&self, msg: &msgs::ChannelUpdate) -> Result<(), LightningError> {
                self.update_channel_internal(&msg.contents, Some(&msg), Some(&msg.signature), true)
        }

        fn update_channel_internal(&self, msg: &msgs::UnsignedChannelUpdate,
                full_msg: Option<&msgs::ChannelUpdate>, sig: Option<&secp256k1::ecdsa::Signature>,
                only_verify: bool) -> Result<(), LightningError>
        {
                let chan_enabled = msg.flags & (1 << 1) != (1 << 1);

                if msg.chain_hash != self.chain_hash {
                        return Err(LightningError {
                                err: "Channel update chain hash does not match genesis hash".to_owned(),
                                action: ErrorAction::IgnoreAndLog(Level::Debug),
                        });
                }

                #[cfg(all(feature = "std", not(test), not(feature = "_test_utils")))]
                {
                        // Note that many tests rely on being able to set arbitrarily old timestamps, thus we
                        // disable this check during tests!
                        let time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                        if (msg.timestamp as u64) < time - STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS {
                                return Err(LightningError{err: "channel_update is older than two weeks old".to_owned(), action: ErrorAction::IgnoreAndLog(Level::Gossip)});
                        }
                        if msg.timestamp as u64 > time + 60 * 60 * 24 {
                                return Err(LightningError{err: "channel_update has a timestamp more than a day in the future".to_owned(), action: ErrorAction::IgnoreAndLog(Level::Gossip)});
                        }
                }

                log_gossip!(self.logger, "Updating channel {} in direction {} with timestamp {}", msg.short_channel_id, msg.flags & 1, msg.timestamp);

                let mut channels = self.channels.write().unwrap();
                match channels.get_mut(&msg.short_channel_id) {
                        None => {
                                core::mem::drop(channels);
                                self.pending_checks.check_hold_pending_channel_update(msg, full_msg)?;
                                return Err(LightningError{err: "Couldn't find channel for update".to_owned(), action: ErrorAction::IgnoreError});
                        },
                        Some(channel) => {
                                if msg.htlc_maximum_msat > MAX_VALUE_MSAT {
                                        return Err(LightningError{err:
                                                "htlc_maximum_msat is larger than maximum possible msats".to_owned(),
                                                action: ErrorAction::IgnoreError});
                                }

                                if let Some(capacity_sats) = channel.capacity_sats {
                                        // It's possible channel capacity is available now, although it wasn't available at announcement (so the field is None).
                                        // Don't query UTXO set here to reduce DoS risks.
                                        if capacity_sats > MAX_VALUE_MSAT / 1000 || msg.htlc_maximum_msat > capacity_sats * 1000 {
                                                return Err(LightningError{err:
                                                        "htlc_maximum_msat is larger than channel capacity or capacity is bogus".to_owned(),
                                                        action: ErrorAction::IgnoreError});
                                        }
                                }
                                macro_rules! check_update_latest {
                                        ($target: expr) => {
                                                if let Some(existing_chan_info) = $target.as_ref() {
                                                        // The timestamp field is somewhat of a misnomer - the BOLTs use it to
                                                        // order updates to ensure you always have the latest one, only
                                                        // suggesting  that it be at least the current time. For
                                                        // channel_updates specifically, the BOLTs discuss the possibility of
                                                        // pruning based on the timestamp field being more than two weeks old,
                                                        // but only in the non-normative section.
                                                        if existing_chan_info.last_update > msg.timestamp {
                                                                return Err(LightningError{err: "Update older than last processed update".to_owned(), action: ErrorAction::IgnoreDuplicateGossip});
                                                        } else if existing_chan_info.last_update == msg.timestamp {
                                                                return Err(LightningError{err: "Update had same timestamp as last processed update".to_owned(), action: ErrorAction::IgnoreDuplicateGossip});
                                                        }
                                                }
                                        }
                                }

                                macro_rules! get_new_channel_info {
                                        () => { {
                                                let last_update_message = if msg.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY
                                                        { full_msg.cloned() } else { None };

                                                let updated_channel_update_info = ChannelUpdateInfo {
                                                        enabled: chan_enabled,
                                                        last_update: msg.timestamp,
                                                        cltv_expiry_delta: msg.cltv_expiry_delta,
                                                        htlc_minimum_msat: msg.htlc_minimum_msat,
                                                        htlc_maximum_msat: msg.htlc_maximum_msat,
                                                        fees: RoutingFees {
                                                                base_msat: msg.fee_base_msat,
                                                                proportional_millionths: msg.fee_proportional_millionths,
                                                        },
                                                        last_update_message
                                                };
                                                Some(updated_channel_update_info)
                                        } }
                                }

                                let msg_hash = hash_to_message!(&message_sha256d_hash(&msg)[..]);
                                if msg.flags & 1 == 1 {
                                        check_update_latest!(channel.two_to_one);
                                        if let Some(sig) = sig {
                                                secp_verify_sig!(self.secp_ctx, &msg_hash, &sig, &PublicKey::from_slice(channel.node_two.as_slice()).map_err(|_| LightningError{
                                                        err: "Couldn't parse source node pubkey".to_owned(),
                                                        action: ErrorAction::IgnoreAndLog(Level::Debug)
                                                })?, "channel_update");
                                        }
                                        if !only_verify {
                                                channel.two_to_one = get_new_channel_info!();
                                        }
                                } else {
                                        check_update_latest!(channel.one_to_two);
                                        if let Some(sig) = sig {
                                                secp_verify_sig!(self.secp_ctx, &msg_hash, &sig, &PublicKey::from_slice(channel.node_one.as_slice()).map_err(|_| LightningError{
                                                        err: "Couldn't parse destination node pubkey".to_owned(),
                                                        action: ErrorAction::IgnoreAndLog(Level::Debug)
                                                })?, "channel_update");
                                        }
                                        if !only_verify {
                                                channel.one_to_two = get_new_channel_info!();
                                        }
                                }
                        }
                }

                Ok(())
        }

        fn remove_channel_in_nodes(&self, nodes: &mut IndexedMap<NodeId, NodeInfo>, chan: &ChannelInfo, short_channel_id: u64) {
                macro_rules! remove_from_node {
                        ($node_id: expr) => {
                                if let IndexedMapEntry::Occupied(mut entry) = nodes.entry($node_id) {
                                        entry.get_mut().channels.retain(|chan_id| {
                                                short_channel_id != *chan_id
                                        });
                                        if entry.get().channels.is_empty() {
                                                self.removed_node_counters.lock().unwrap().push(entry.get().node_counter);
                                                entry.remove_entry();
                                        }
                                } else {
                                        panic!("Had channel that pointed to unknown node (ie inconsistent network map)!");
                                }
                        }
                }

                remove_from_node!(chan.node_one);
                remove_from_node!(chan.node_two);
        }
}

impl ReadOnlyNetworkGraph<'_> {
        /// Returns all known valid channels' short ids along with announced channel info.
        ///
        /// This is not exported to bindings users because we don't want to return lifetime'd references
        pub fn channels(&self) -> &IndexedMap<u64, ChannelInfo> {
                &*self.channels
        }

        /// Returns information on a channel with the given id.
        pub fn channel(&self, short_channel_id: u64) -> Option<&ChannelInfo> {
                self.channels.get(&short_channel_id)
        }

        #[cfg(c_bindings)] // Non-bindings users should use `channels`
        /// Returns the list of channels in the graph
        pub fn list_channels(&self) -> Vec<u64> {
                self.channels.unordered_keys().map(|c| *c).collect()
        }

        /// Returns all known nodes' public keys along with announced node info.
        ///
        /// This is not exported to bindings users because we don't want to return lifetime'd references
        pub fn nodes(&self) -> &IndexedMap<NodeId, NodeInfo> {
                &*self.nodes
        }

        /// Returns information on a node with the given id.
        pub fn node(&self, node_id: &NodeId) -> Option<&NodeInfo> {
                self.nodes.get(node_id)
        }

        #[cfg(c_bindings)] // Non-bindings users should use `nodes`
        /// Returns the list of nodes in the graph
        pub fn list_nodes(&self) -> Vec<NodeId> {
                self.nodes.unordered_keys().map(|n| *n).collect()
        }

        /// Get network addresses by node id.
        /// Returns None if the requested node is completely unknown,
        /// or if node announcement for the node was never received.
        pub fn get_addresses(&self, pubkey: &PublicKey) -> Option<Vec<SocketAddress>> {
                self.nodes.get(&NodeId::from_pubkey(&pubkey))
                        .and_then(|node| node.announcement_info.as_ref().map(|ann| ann.addresses().to_vec()))
        }

        /// Gets the maximum possible node_counter for a node in this graph
        pub(crate) fn max_node_counter(&self) -> u32 {
                self.max_node_counter
        }
}

#[cfg(test)]
pub(crate) mod tests {
        use crate::events::{MessageSendEvent, MessageSendEventsProvider};
        use crate::ln::channelmanager;
        use crate::ln::chan_utils::make_funding_redeemscript;
        #[cfg(feature = "std")]
        use crate::ln::features::InitFeatures;
        use crate::routing::gossip::{P2PGossipSync, NetworkGraph, NetworkUpdate, NodeAlias, MAX_EXCESS_BYTES_FOR_RELAY, NodeId, RoutingFees, ChannelUpdateInfo, ChannelInfo, NodeAnnouncementInfo, NodeInfo};
        use crate::routing::utxo::{UtxoLookupError, UtxoResult};
        use crate::ln::msgs::{RoutingMessageHandler, UnsignedNodeAnnouncement, NodeAnnouncement,
                UnsignedChannelAnnouncement, ChannelAnnouncement, UnsignedChannelUpdate, ChannelUpdate,
                ReplyChannelRange, QueryChannelRange, QueryShortChannelIds, MAX_VALUE_MSAT};
        use crate::util::config::UserConfig;
        use crate::util::test_utils;
        use crate::util::ser::{ReadableArgs, Readable, Writeable};
        use crate::util::scid_utils::scid_from_parts;

        use crate::routing::gossip::REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS;
        use super::STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS;

        use bitcoin::hashes::sha256d::Hash as Sha256dHash;
        use bitcoin::hashes::Hash;
        use bitcoin::hashes::hex::FromHex;
        use bitcoin::network::constants::Network;
        use bitcoin::blockdata::constants::ChainHash;
        use bitcoin::blockdata::script::ScriptBuf;
        use bitcoin::blockdata::transaction::TxOut;
        use bitcoin::secp256k1::{PublicKey, SecretKey};
        use bitcoin::secp256k1::{All, Secp256k1};

        use crate::io;
        use bitcoin::secp256k1;
        use crate::prelude::*;
        use crate::sync::Arc;

        fn create_network_graph() -> NetworkGraph<Arc<test_utils::TestLogger>> {
                let logger = Arc::new(test_utils::TestLogger::new());
                NetworkGraph::new(Network::Testnet, logger)
        }

        fn create_gossip_sync(network_graph: &NetworkGraph<Arc<test_utils::TestLogger>>) -> (
                Secp256k1<All>, P2PGossipSync<&NetworkGraph<Arc<test_utils::TestLogger>>,
                Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>
        ) {
                let secp_ctx = Secp256k1::new();
                let logger = Arc::new(test_utils::TestLogger::new());
                let gossip_sync = P2PGossipSync::new(network_graph, None, Arc::clone(&logger));
                (secp_ctx, gossip_sync)
        }

        #[test]
        #[cfg(feature = "std")]
        fn request_full_sync_finite_times() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);
                let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&<Vec<u8>>::from_hex("0202020202020202020202020202020202020202020202020202020202020202").unwrap()[..]).unwrap());

                assert!(gossip_sync.should_request_full_sync(&node_id));
                assert!(gossip_sync.should_request_full_sync(&node_id));
                assert!(gossip_sync.should_request_full_sync(&node_id));
                assert!(gossip_sync.should_request_full_sync(&node_id));
                assert!(gossip_sync.should_request_full_sync(&node_id));
                assert!(!gossip_sync.should_request_full_sync(&node_id));
        }

        pub(crate) fn get_signed_node_announcement<F: Fn(&mut UnsignedNodeAnnouncement)>(f: F, node_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> NodeAnnouncement {
                let node_id = NodeId::from_pubkey(&PublicKey::from_secret_key(&secp_ctx, node_key));
                let mut unsigned_announcement = UnsignedNodeAnnouncement {
                        features: channelmanager::provided_node_features(&UserConfig::default()),
                        timestamp: 100,
                        node_id,
                        rgb: [0; 3],
                        alias: NodeAlias([0; 32]),
                        addresses: Vec::new(),
                        excess_address_data: Vec::new(),
                        excess_data: Vec::new(),
                };
                f(&mut unsigned_announcement);
                let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_announcement.encode()[..])[..]);
                NodeAnnouncement {
                        signature: secp_ctx.sign_ecdsa(&msghash, node_key),
                        contents: unsigned_announcement
                }
        }

        pub(crate) fn get_signed_channel_announcement<F: Fn(&mut UnsignedChannelAnnouncement)>(f: F, node_1_key: &SecretKey, node_2_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> ChannelAnnouncement {
                let node_id_1 = PublicKey::from_secret_key(&secp_ctx, node_1_key);
                let node_id_2 = PublicKey::from_secret_key(&secp_ctx, node_2_key);
                let node_1_btckey = &SecretKey::from_slice(&[40; 32]).unwrap();
                let node_2_btckey = &SecretKey::from_slice(&[39; 32]).unwrap();

                let mut unsigned_announcement = UnsignedChannelAnnouncement {
                        features: channelmanager::provided_channel_features(&UserConfig::default()),
                        chain_hash: ChainHash::using_genesis_block(Network::Testnet),
                        short_channel_id: 0,
                        node_id_1: NodeId::from_pubkey(&node_id_1),
                        node_id_2: NodeId::from_pubkey(&node_id_2),
                        bitcoin_key_1: NodeId::from_pubkey(&PublicKey::from_secret_key(&secp_ctx, node_1_btckey)),
                        bitcoin_key_2: NodeId::from_pubkey(&PublicKey::from_secret_key(&secp_ctx, node_2_btckey)),
                        excess_data: Vec::new(),
                };
                f(&mut unsigned_announcement);
                let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_announcement.encode()[..])[..]);
                ChannelAnnouncement {
                        node_signature_1: secp_ctx.sign_ecdsa(&msghash, node_1_key),
                        node_signature_2: secp_ctx.sign_ecdsa(&msghash, node_2_key),
                        bitcoin_signature_1: secp_ctx.sign_ecdsa(&msghash, node_1_btckey),
                        bitcoin_signature_2: secp_ctx.sign_ecdsa(&msghash, node_2_btckey),
                        contents: unsigned_announcement,
                }
        }

        pub(crate) fn get_channel_script(secp_ctx: &Secp256k1<secp256k1::All>) -> ScriptBuf {
                let node_1_btckey = SecretKey::from_slice(&[40; 32]).unwrap();
                let node_2_btckey = SecretKey::from_slice(&[39; 32]).unwrap();
                make_funding_redeemscript(&PublicKey::from_secret_key(secp_ctx, &node_1_btckey),
                        &PublicKey::from_secret_key(secp_ctx, &node_2_btckey)).to_v0_p2wsh()
        }

        pub(crate) fn get_signed_channel_update<F: Fn(&mut UnsignedChannelUpdate)>(f: F, node_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> ChannelUpdate {
                let mut unsigned_channel_update = UnsignedChannelUpdate {
                        chain_hash: ChainHash::using_genesis_block(Network::Testnet),
                        short_channel_id: 0,
                        timestamp: 100,
                        flags: 0,
                        cltv_expiry_delta: 144,
                        htlc_minimum_msat: 1_000_000,
                        htlc_maximum_msat: 1_000_000,
                        fee_base_msat: 10_000,
                        fee_proportional_millionths: 20,
                        excess_data: Vec::new()
                };
                f(&mut unsigned_channel_update);
                let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_channel_update.encode()[..])[..]);
                ChannelUpdate {
                        signature: secp_ctx.sign_ecdsa(&msghash, node_key),
                        contents: unsigned_channel_update
                }
        }

        #[test]
        fn handling_node_announcements() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);

                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
                let zero_hash = Sha256dHash::hash(&[0; 32]);

                let valid_announcement = get_signed_node_announcement(|_| {}, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_node_announcement(&valid_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!("No existing channels for node_announcement", e.err)
                };

                {
                        // Announce a channel to add a corresponding node.
                        let valid_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                        match gossip_sync.handle_channel_announcement(&valid_announcement) {
                                Ok(res) => assert!(res),
                                _ => panic!()
                        };
                }

                match gossip_sync.handle_node_announcement(&valid_announcement) {
                        Ok(res) => assert!(res),
                        Err(_) => panic!()
                };

                let fake_msghash = hash_to_message!(zero_hash.as_byte_array());
                match gossip_sync.handle_node_announcement(
                        &NodeAnnouncement {
                                signature: secp_ctx.sign_ecdsa(&fake_msghash, node_1_privkey),
                                contents: valid_announcement.contents.clone()
                }) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Invalid signature on node_announcement message")
                };

                let announcement_with_data = get_signed_node_announcement(|unsigned_announcement| {
                        unsigned_announcement.timestamp += 1000;
                        unsigned_announcement.excess_data.resize(MAX_EXCESS_BYTES_FOR_RELAY + 1, 0);
                }, node_1_privkey, &secp_ctx);
                // Return false because contains excess data.
                match gossip_sync.handle_node_announcement(&announcement_with_data) {
                        Ok(res) => assert!(!res),
                        Err(_) => panic!()
                };

                // Even though previous announcement was not relayed further, we still accepted it,
                // so we now won't accept announcements before the previous one.
                let outdated_announcement = get_signed_node_announcement(|unsigned_announcement| {
                        unsigned_announcement.timestamp += 1000 - 10;
                }, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_node_announcement(&outdated_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Update older than last processed update")
                };
        }

        #[test]
        fn handling_channel_announcements() {
                let secp_ctx = Secp256k1::new();
                let logger = test_utils::TestLogger::new();

                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();

                let good_script = get_channel_script(&secp_ctx);
                let valid_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);

                // Test if the UTXO lookups were not supported
                let network_graph = NetworkGraph::new(Network::Testnet, &logger);
                let mut gossip_sync = P2PGossipSync::new(&network_graph, None, &logger);
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(res) => assert!(res),
                        _ => panic!()
                };

                {
                        match network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id) {
                                None => panic!(),
                                Some(_) => ()
                        };
                }

                // If we receive announcement for the same channel (with UTXO lookups disabled),
                // drop new one on the floor, since we can't see any changes.
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Already have non-chain-validated channel")
                };

                // Test if an associated transaction were not on-chain (or not confirmed).
                let chain_source = test_utils::TestChainSource::new(Network::Testnet);
                *chain_source.utxo_ret.lock().unwrap() = UtxoResult::Sync(Err(UtxoLookupError::UnknownTx));
                let network_graph = NetworkGraph::new(Network::Testnet, &logger);
                gossip_sync = P2PGossipSync::new(&network_graph, Some(&chain_source), &logger);

                let valid_announcement = get_signed_channel_announcement(|unsigned_announcement| {
                        unsigned_announcement.short_channel_id += 1;
                }, node_1_privkey, node_2_privkey, &secp_ctx);
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Channel announced without corresponding UTXO entry")
                };

                // Now test if the transaction is found in the UTXO set and the script is correct.
                *chain_source.utxo_ret.lock().unwrap() =
                        UtxoResult::Sync(Ok(TxOut { value: 0, script_pubkey: good_script.clone() }));
                let valid_announcement = get_signed_channel_announcement(|unsigned_announcement| {
                        unsigned_announcement.short_channel_id += 2;
                }, node_1_privkey, node_2_privkey, &secp_ctx);
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(res) => assert!(res),
                        _ => panic!()
                };

                {
                        match network_graph.read_only().channels().get(&valid_announcement.contents.short_channel_id) {
                                None => panic!(),
                                Some(_) => ()
                        };
                }

                // If we receive announcement for the same channel, once we've validated it against the
                // chain, we simply ignore all new (duplicate) announcements.
                *chain_source.utxo_ret.lock().unwrap() =
                        UtxoResult::Sync(Ok(TxOut { value: 0, script_pubkey: good_script }));
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Already have chain-validated channel")
                };

                #[cfg(feature = "std")]
                {
                        use std::time::{SystemTime, UNIX_EPOCH};

                        let tracking_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                        // Mark a node as permanently failed so it's tracked as removed.
                        gossip_sync.network_graph().node_failed_permanent(&PublicKey::from_secret_key(&secp_ctx, node_1_privkey));

                        // Return error and ignore valid channel announcement if one of the nodes has been tracked as removed.
                        let valid_announcement = get_signed_channel_announcement(|unsigned_announcement| {
                                unsigned_announcement.short_channel_id += 3;
                        }, node_1_privkey, node_2_privkey, &secp_ctx);
                        match gossip_sync.handle_channel_announcement(&valid_announcement) {
                                Ok(_) => panic!(),
                                Err(e) => assert_eq!(e.err, "Channel with SCID 3 or one of its nodes was removed from our network graph recently")
                        }

                        gossip_sync.network_graph().remove_stale_channels_and_tracking_with_time(tracking_time + REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS);

                        // The above channel announcement should be handled as per normal now.
                        match gossip_sync.handle_channel_announcement(&valid_announcement) {
                                Ok(res) => assert!(res),
                                _ => panic!()
                        }
                }

                // Don't relay valid channels with excess data
                let valid_announcement = get_signed_channel_announcement(|unsigned_announcement| {
                        unsigned_announcement.short_channel_id += 4;
                        unsigned_announcement.excess_data.resize(MAX_EXCESS_BYTES_FOR_RELAY + 1, 0);
                }, node_1_privkey, node_2_privkey, &secp_ctx);
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(res) => assert!(!res),
                        _ => panic!()
                };

                let mut invalid_sig_announcement = valid_announcement.clone();
                invalid_sig_announcement.contents.excess_data = Vec::new();
                match gossip_sync.handle_channel_announcement(&invalid_sig_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Invalid signature on channel_announcement message")
                };

                let channel_to_itself_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_channel_announcement(&channel_to_itself_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Channel announcement node had a channel with itself")
                };

                // Test that channel announcements with the wrong chain hash are ignored (network graph is testnet,
                // announcement is mainnet).
                let incorrect_chain_announcement = get_signed_channel_announcement(|unsigned_announcement| {
                        unsigned_announcement.chain_hash = ChainHash::using_genesis_block(Network::Bitcoin);
                }, node_1_privkey, node_2_privkey, &secp_ctx);
                match gossip_sync.handle_channel_announcement(&incorrect_chain_announcement) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Channel announcement chain hash does not match genesis hash")
                };
        }

        #[test]
        fn handling_channel_update() {
                let secp_ctx = Secp256k1::new();
                let logger = test_utils::TestLogger::new();
                let chain_source = test_utils::TestChainSource::new(Network::Testnet);
                let network_graph = NetworkGraph::new(Network::Testnet, &logger);
                let gossip_sync = P2PGossipSync::new(&network_graph, Some(&chain_source), &logger);

                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();

                let amount_sats = 1000_000;
                let short_channel_id;

                {
                        // Announce a channel we will update
                        let good_script = get_channel_script(&secp_ctx);
                        *chain_source.utxo_ret.lock().unwrap() =
                                UtxoResult::Sync(Ok(TxOut { value: amount_sats, script_pubkey: good_script.clone() }));

                        let valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                        short_channel_id = valid_channel_announcement.contents.short_channel_id;
                        match gossip_sync.handle_channel_announcement(&valid_channel_announcement) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };

                }

                let valid_channel_update = get_signed_channel_update(|_| {}, node_1_privkey, &secp_ctx);
                network_graph.verify_channel_update(&valid_channel_update).unwrap();
                match gossip_sync.handle_channel_update(&valid_channel_update) {
                        Ok(res) => assert!(res),
                        _ => panic!(),
                };

                {
                        match network_graph.read_only().channels().get(&short_channel_id) {
                                None => panic!(),
                                Some(channel_info) => {
                                        assert_eq!(channel_info.one_to_two.as_ref().unwrap().cltv_expiry_delta, 144);
                                        assert!(channel_info.two_to_one.is_none());
                                }
                        };
                }

                let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.timestamp += 100;
                        unsigned_channel_update.excess_data.resize(MAX_EXCESS_BYTES_FOR_RELAY + 1, 0);
                }, node_1_privkey, &secp_ctx);
                // Return false because contains excess data
                match gossip_sync.handle_channel_update(&valid_channel_update) {
                        Ok(res) => assert!(!res),
                        _ => panic!()
                };

                let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.timestamp += 110;
                        unsigned_channel_update.short_channel_id += 1;
                }, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_channel_update(&valid_channel_update) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Couldn't find channel for update")
                };

                let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.htlc_maximum_msat = MAX_VALUE_MSAT + 1;
                        unsigned_channel_update.timestamp += 110;
                }, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_channel_update(&valid_channel_update) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "htlc_maximum_msat is larger than maximum possible msats")
                };

                let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.htlc_maximum_msat = amount_sats * 1000 + 1;
                        unsigned_channel_update.timestamp += 110;
                }, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_channel_update(&valid_channel_update) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "htlc_maximum_msat is larger than channel capacity or capacity is bogus")
                };

                // Even though previous update was not relayed further, we still accepted it,
                // so we now won't accept update before the previous one.
                let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.timestamp += 100;
                }, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_channel_update(&valid_channel_update) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Update had same timestamp as last processed update")
                };

                let mut invalid_sig_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.timestamp += 500;
                }, node_1_privkey, &secp_ctx);
                let zero_hash = Sha256dHash::hash(&[0; 32]);
                let fake_msghash = hash_to_message!(zero_hash.as_byte_array());
                invalid_sig_channel_update.signature = secp_ctx.sign_ecdsa(&fake_msghash, node_1_privkey);
                match gossip_sync.handle_channel_update(&invalid_sig_channel_update) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Invalid signature on channel_update message")
                };

                // Test that channel updates with the wrong chain hash are ignored (network graph is testnet, channel
                // update is mainet).
                let incorrect_chain_update = get_signed_channel_update(|unsigned_channel_update| {
                        unsigned_channel_update.chain_hash = ChainHash::using_genesis_block(Network::Bitcoin);
                }, node_1_privkey, &secp_ctx);

                match gossip_sync.handle_channel_update(&incorrect_chain_update) {
                        Ok(_) => panic!(),
                        Err(e) => assert_eq!(e.err, "Channel update chain hash does not match genesis hash")
                };
        }

        #[test]
        fn handling_network_update() {
                let logger = test_utils::TestLogger::new();
                let network_graph = NetworkGraph::new(Network::Testnet, &logger);
                let secp_ctx = Secp256k1::new();

                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
                let node_2_id = PublicKey::from_secret_key(&secp_ctx, node_2_privkey);

                {
                        // There is no nodes in the table at the beginning.
                        assert_eq!(network_graph.read_only().nodes().len(), 0);
                }

                let short_channel_id;
                {
                        // Check we won't apply an update via `handle_network_update` for privacy reasons, but
                        // can continue fine if we manually apply it.
                        let valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                        short_channel_id = valid_channel_announcement.contents.short_channel_id;
                        let chain_source: Option<&test_utils::TestChainSource> = None;
                        assert!(network_graph.update_channel_from_announcement(&valid_channel_announcement, &chain_source).is_ok());
                        assert!(network_graph.read_only().channels().get(&short_channel_id).is_some());

                        let valid_channel_update = get_signed_channel_update(|_| {}, node_1_privkey, &secp_ctx);
                        assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_none());

                        network_graph.handle_network_update(&NetworkUpdate::ChannelUpdateMessage {
                                msg: valid_channel_update.clone(),
                        });

                        assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_none());
                        network_graph.update_channel(&valid_channel_update).unwrap();
                }

                // Non-permanent failure doesn't touch the channel at all
                {
                        match network_graph.read_only().channels().get(&short_channel_id) {
                                None => panic!(),
                                Some(channel_info) => {
                                        assert!(channel_info.one_to_two.as_ref().unwrap().enabled);
                                }
                        };

                        network_graph.handle_network_update(&NetworkUpdate::ChannelFailure {
                                short_channel_id,
                                is_permanent: false,
                        });

                        match network_graph.read_only().channels().get(&short_channel_id) {
                                None => panic!(),
                                Some(channel_info) => {
                                        assert!(channel_info.one_to_two.as_ref().unwrap().enabled);
                                }
                        };
                }

                // Permanent closing deletes a channel
                network_graph.handle_network_update(&NetworkUpdate::ChannelFailure {
                        short_channel_id,
                        is_permanent: true,
                });

                assert_eq!(network_graph.read_only().channels().len(), 0);
                // Nodes are also deleted because there are no associated channels anymore
                assert_eq!(network_graph.read_only().nodes().len(), 0);

                {
                        // Get a new network graph since we don't want to track removed nodes in this test with "std"
                        let network_graph = NetworkGraph::new(Network::Testnet, &logger);

                        // Announce a channel to test permanent node failure
                        let valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                        let short_channel_id = valid_channel_announcement.contents.short_channel_id;
                        let chain_source: Option<&test_utils::TestChainSource> = None;
                        assert!(network_graph.update_channel_from_announcement(&valid_channel_announcement, &chain_source).is_ok());
                        assert!(network_graph.read_only().channels().get(&short_channel_id).is_some());

                        // Non-permanent node failure does not delete any nodes or channels
                        network_graph.handle_network_update(&NetworkUpdate::NodeFailure {
                                node_id: node_2_id,
                                is_permanent: false,
                        });

                        assert!(network_graph.read_only().channels().get(&short_channel_id).is_some());
                        assert!(network_graph.read_only().nodes().get(&NodeId::from_pubkey(&node_2_id)).is_some());

                        // Permanent node failure deletes node and its channels
                        network_graph.handle_network_update(&NetworkUpdate::NodeFailure {
                                node_id: node_2_id,
                                is_permanent: true,
                        });

                        assert_eq!(network_graph.read_only().nodes().len(), 0);
                        // Channels are also deleted because the associated node has been deleted
                        assert_eq!(network_graph.read_only().channels().len(), 0);
                }
        }

        #[test]
        fn test_channel_timeouts() {
                // Test the removal of channels with `remove_stale_channels_and_tracking`.
                let logger = test_utils::TestLogger::new();
                let chain_source = test_utils::TestChainSource::new(Network::Testnet);
                let network_graph = NetworkGraph::new(Network::Testnet, &logger);
                let gossip_sync = P2PGossipSync::new(&network_graph, Some(&chain_source), &logger);
                let secp_ctx = Secp256k1::new();

                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();

                let valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                let short_channel_id = valid_channel_announcement.contents.short_channel_id;
                let chain_source: Option<&test_utils::TestChainSource> = None;
                assert!(network_graph.update_channel_from_announcement(&valid_channel_announcement, &chain_source).is_ok());
                assert!(network_graph.read_only().channels().get(&short_channel_id).is_some());

                // Submit two channel updates for each channel direction (update.flags bit).
                let valid_channel_update = get_signed_channel_update(|_| {}, node_1_privkey, &secp_ctx);
                assert!(gossip_sync.handle_channel_update(&valid_channel_update).is_ok());
                assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_some());

                let valid_channel_update_2 = get_signed_channel_update(|update| {update.flags |=1;}, node_2_privkey, &secp_ctx);
                gossip_sync.handle_channel_update(&valid_channel_update_2).unwrap();
                assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().two_to_one.is_some());

                network_graph.remove_stale_channels_and_tracking_with_time(100 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS);
                assert_eq!(network_graph.read_only().channels().len(), 1);
                assert_eq!(network_graph.read_only().nodes().len(), 2);

                network_graph.remove_stale_channels_and_tracking_with_time(101 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS);
                #[cfg(not(feature = "std"))] {
                        // Make sure removed channels are tracked.
                        assert_eq!(network_graph.removed_channels.lock().unwrap().len(), 1);
                }
                network_graph.remove_stale_channels_and_tracking_with_time(101 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS +
                        REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS);

                #[cfg(feature = "std")]
                {
                        // In std mode, a further check is performed before fully removing the channel -
                        // the channel_announcement must have been received at least two weeks ago. We
                        // fudge that here by indicating the time has jumped two weeks.
                        assert_eq!(network_graph.read_only().channels().len(), 1);
                        assert_eq!(network_graph.read_only().nodes().len(), 2);

                        // Note that the directional channel information will have been removed already..
                        // We want to check that this will work even if *one* of the channel updates is recent,
                        // so we should add it with a recent timestamp.
                        assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_none());
                        use std::time::{SystemTime, UNIX_EPOCH};
                        let announcement_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                        let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                                unsigned_channel_update.timestamp = (announcement_time + 1 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS) as u32;
                        }, node_1_privkey, &secp_ctx);
                        assert!(gossip_sync.handle_channel_update(&valid_channel_update).is_ok());
                        assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_some());
                        network_graph.remove_stale_channels_and_tracking_with_time(announcement_time + 1 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS);
                        // Make sure removed channels are tracked.
                        assert_eq!(network_graph.removed_channels.lock().unwrap().len(), 1);
                        // Provide a later time so that sufficient time has passed
                        network_graph.remove_stale_channels_and_tracking_with_time(announcement_time + 1 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS +
                                REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS);
                }

                assert_eq!(network_graph.read_only().channels().len(), 0);
                assert_eq!(network_graph.read_only().nodes().len(), 0);
                assert!(network_graph.removed_channels.lock().unwrap().is_empty());

                #[cfg(feature = "std")]
                {
                        use std::time::{SystemTime, UNIX_EPOCH};

                        let tracking_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();

                        // Clear tracked nodes and channels for clean slate
                        network_graph.removed_channels.lock().unwrap().clear();
                        network_graph.removed_nodes.lock().unwrap().clear();

                        // Add a channel and nodes from channel announcement. So our network graph will
                        // now only consist of two nodes and one channel between them.
                        assert!(network_graph.update_channel_from_announcement(
                                &valid_channel_announcement, &chain_source).is_ok());

                        // Mark the channel as permanently failed. This will also remove the two nodes
                        // and all of the entries will be tracked as removed.
                        network_graph.channel_failed_permanent_with_time(short_channel_id, Some(tracking_time));

                        // Should not remove from tracking if insufficient time has passed
                        network_graph.remove_stale_channels_and_tracking_with_time(
                                tracking_time + REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS - 1);
                        assert_eq!(network_graph.removed_channels.lock().unwrap().len(), 1, "Removed channel count ≠ 1 with tracking_time {}", tracking_time);

                        // Provide a later time so that sufficient time has passed
                        network_graph.remove_stale_channels_and_tracking_with_time(
                                tracking_time + REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS);
                        assert!(network_graph.removed_channels.lock().unwrap().is_empty(), "Unexpectedly removed channels with tracking_time {}", tracking_time);
                        assert!(network_graph.removed_nodes.lock().unwrap().is_empty(), "Unexpectedly removed nodes with tracking_time {}", tracking_time);
                }

                #[cfg(not(feature = "std"))]
                {
                        // When we don't have access to the system clock, the time we started tracking removal will only
                        // be that provided by the first call to `remove_stale_channels_and_tracking_with_time`. Hence,
                        // only if sufficient time has passed after that first call, will the next call remove it from
                        // tracking.
                        let removal_time = 1664619654;

                        // Clear removed nodes and channels for clean slate
                        network_graph.removed_channels.lock().unwrap().clear();
                        network_graph.removed_nodes.lock().unwrap().clear();

                        // Add a channel and nodes from channel announcement. So our network graph will
                        // now only consist of two nodes and one channel between them.
                        assert!(network_graph.update_channel_from_announcement(
                                &valid_channel_announcement, &chain_source).is_ok());

                        // Mark the channel as permanently failed. This will also remove the two nodes
                        // and all of the entries will be tracked as removed.
                        network_graph.channel_failed_permanent(short_channel_id);

                        // The first time we call the following, the channel will have a removal time assigned.
                        network_graph.remove_stale_channels_and_tracking_with_time(removal_time);
                        assert_eq!(network_graph.removed_channels.lock().unwrap().len(), 1);

                        // Provide a later time so that sufficient time has passed
                        network_graph.remove_stale_channels_and_tracking_with_time(
                                removal_time + REMOVED_ENTRIES_TRACKING_AGE_LIMIT_SECS);
                        assert!(network_graph.removed_channels.lock().unwrap().is_empty());
                        assert!(network_graph.removed_nodes.lock().unwrap().is_empty());
                }
        }

        #[test]
        fn getting_next_channel_announcements() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);
                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();

                // Channels were not announced yet.
                let channels_with_announcements = gossip_sync.get_next_channel_announcement(0);
                assert!(channels_with_announcements.is_none());

                let short_channel_id;
                {
                        // Announce a channel we will update
                        let valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                        short_channel_id = valid_channel_announcement.contents.short_channel_id;
                        match gossip_sync.handle_channel_announcement(&valid_channel_announcement) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };
                }

                // Contains initial channel announcement now.
                let channels_with_announcements = gossip_sync.get_next_channel_announcement(short_channel_id);
                if let Some(channel_announcements) = channels_with_announcements {
                        let (_, ref update_1, ref update_2) = channel_announcements;
                        assert_eq!(update_1, &None);
                        assert_eq!(update_2, &None);
                } else {
                        panic!();
                }

                {
                        // Valid channel update
                        let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                                unsigned_channel_update.timestamp = 101;
                        }, node_1_privkey, &secp_ctx);
                        match gossip_sync.handle_channel_update(&valid_channel_update) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };
                }

                // Now contains an initial announcement and an update.
                let channels_with_announcements = gossip_sync.get_next_channel_announcement(short_channel_id);
                if let Some(channel_announcements) = channels_with_announcements {
                        let (_, ref update_1, ref update_2) = channel_announcements;
                        assert_ne!(update_1, &None);
                        assert_eq!(update_2, &None);
                } else {
                        panic!();
                }

                {
                        // Channel update with excess data.
                        let valid_channel_update = get_signed_channel_update(|unsigned_channel_update| {
                                unsigned_channel_update.timestamp = 102;
                                unsigned_channel_update.excess_data = [1; MAX_EXCESS_BYTES_FOR_RELAY + 1].to_vec();
                        }, node_1_privkey, &secp_ctx);
                        match gossip_sync.handle_channel_update(&valid_channel_update) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };
                }

                // Test that announcements with excess data won't be returned
                let channels_with_announcements = gossip_sync.get_next_channel_announcement(short_channel_id);
                if let Some(channel_announcements) = channels_with_announcements {
                        let (_, ref update_1, ref update_2) = channel_announcements;
                        assert_eq!(update_1, &None);
                        assert_eq!(update_2, &None);
                } else {
                        panic!();
                }

                // Further starting point have no channels after it
                let channels_with_announcements = gossip_sync.get_next_channel_announcement(short_channel_id + 1000);
                assert!(channels_with_announcements.is_none());
        }

        #[test]
        fn getting_next_node_announcements() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);
                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
                let node_id_1 = NodeId::from_pubkey(&PublicKey::from_secret_key(&secp_ctx, node_1_privkey));

                // No nodes yet.
                let next_announcements = gossip_sync.get_next_node_announcement(None);
                assert!(next_announcements.is_none());

                {
                        // Announce a channel to add 2 nodes
                        let valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                        match gossip_sync.handle_channel_announcement(&valid_channel_announcement) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };
                }

                // Nodes were never announced
                let next_announcements = gossip_sync.get_next_node_announcement(None);
                assert!(next_announcements.is_none());

                {
                        let valid_announcement = get_signed_node_announcement(|_| {}, node_1_privkey, &secp_ctx);
                        match gossip_sync.handle_node_announcement(&valid_announcement) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };

                        let valid_announcement = get_signed_node_announcement(|_| {}, node_2_privkey, &secp_ctx);
                        match gossip_sync.handle_node_announcement(&valid_announcement) {
                                Ok(_) => (),
                                Err(_) => panic!()
                        };
                }

                let next_announcements = gossip_sync.get_next_node_announcement(None);
                assert!(next_announcements.is_some());

                // Skip the first node.
                let next_announcements = gossip_sync.get_next_node_announcement(Some(&node_id_1));
                assert!(next_announcements.is_some());

                {
                        // Later announcement which should not be relayed (excess data) prevent us from sharing a node
                        let valid_announcement = get_signed_node_announcement(|unsigned_announcement| {
                                unsigned_announcement.timestamp += 10;
                                unsigned_announcement.excess_data = [1; MAX_EXCESS_BYTES_FOR_RELAY + 1].to_vec();
                        }, node_2_privkey, &secp_ctx);
                        match gossip_sync.handle_node_announcement(&valid_announcement) {
                                Ok(res) => assert!(!res),
                                Err(_) => panic!()
                        };
                }

                let next_announcements = gossip_sync.get_next_node_announcement(Some(&node_id_1));
                assert!(next_announcements.is_none());
        }

        #[test]
        fn network_graph_serialization() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);

                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();

                // Announce a channel to add a corresponding node.
                let valid_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
                match gossip_sync.handle_channel_announcement(&valid_announcement) {
                        Ok(res) => assert!(res),
                        _ => panic!()
                };

                let valid_announcement = get_signed_node_announcement(|_| {}, node_1_privkey, &secp_ctx);
                match gossip_sync.handle_node_announcement(&valid_announcement) {
                        Ok(_) => (),
                        Err(_) => panic!()
                };

                let mut w = test_utils::TestVecWriter(Vec::new());
                assert!(!network_graph.read_only().nodes().is_empty());
                assert!(!network_graph.read_only().channels().is_empty());
                network_graph.write(&mut w).unwrap();

                let logger = Arc::new(test_utils::TestLogger::new());
                assert!(<NetworkGraph<_>>::read(&mut io::Cursor::new(&w.0), logger).unwrap() == network_graph);
        }

        #[test]
        fn network_graph_tlv_serialization() {
                let network_graph = create_network_graph();
                network_graph.set_last_rapid_gossip_sync_timestamp(42);

                let mut w = test_utils::TestVecWriter(Vec::new());
                network_graph.write(&mut w).unwrap();

                let logger = Arc::new(test_utils::TestLogger::new());
                let reassembled_network_graph: NetworkGraph<_> = ReadableArgs::read(&mut io::Cursor::new(&w.0), logger).unwrap();
                assert!(reassembled_network_graph == network_graph);
                assert_eq!(reassembled_network_graph.get_last_rapid_gossip_sync_timestamp().unwrap(), 42);
        }

        #[test]
        #[cfg(feature = "std")]
        fn calling_sync_routing_table() {
                use std::time::{SystemTime, UNIX_EPOCH};
                use crate::ln::msgs::Init;

                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);
                let node_privkey_1 = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_id_1 = PublicKey::from_secret_key(&secp_ctx, node_privkey_1);

                let chain_hash = ChainHash::using_genesis_block(Network::Testnet);

                // It should ignore if gossip_queries feature is not enabled
                {
                        let init_msg = Init { features: InitFeatures::empty(), networks: None, remote_network_address: None };
                        gossip_sync.peer_connected(&node_id_1, &init_msg, true).unwrap();
                        let events = gossip_sync.get_and_clear_pending_msg_events();
                        assert_eq!(events.len(), 0);
                }

                // It should send a gossip_timestamp_filter with the correct information
                {
                        let mut features = InitFeatures::empty();
                        features.set_gossip_queries_optional();
                        let init_msg = Init { features, networks: None, remote_network_address: None };
                        gossip_sync.peer_connected(&node_id_1, &init_msg, true).unwrap();
                        let events = gossip_sync.get_and_clear_pending_msg_events();
                        assert_eq!(events.len(), 1);
                        match &events[0] {
                                MessageSendEvent::SendGossipTimestampFilter{ node_id, msg } => {
                                        assert_eq!(node_id, &node_id_1);
                                        assert_eq!(msg.chain_hash, chain_hash);
                                        let expected_timestamp = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
                                        assert!((msg.first_timestamp as u64) >= expected_timestamp - 60*60*24*7*2);
                                        assert!((msg.first_timestamp as u64) < expected_timestamp - 60*60*24*7*2 + 10);
                                        assert_eq!(msg.timestamp_range, u32::max_value());
                                },
                                _ => panic!("Expected MessageSendEvent::SendChannelRangeQuery")
                        };
                }
        }

        #[test]
        fn handling_query_channel_range() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);

                let chain_hash = ChainHash::using_genesis_block(Network::Testnet);
                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
                let node_id_2 = PublicKey::from_secret_key(&secp_ctx, node_2_privkey);

                let mut scids: Vec<u64> = vec![
                        scid_from_parts(0xfffffe, 0xffffff, 0xffff).unwrap(), // max
                        scid_from_parts(0xffffff, 0xffffff, 0xffff).unwrap(), // never
                ];

                // used for testing multipart reply across blocks
                for block in 100000..=108001 {
                        scids.push(scid_from_parts(block, 0, 0).unwrap());
                }

                // used for testing resumption on same block
                scids.push(scid_from_parts(108001, 1, 0).unwrap());

                for scid in scids {
                        let valid_announcement = get_signed_channel_announcement(|unsigned_announcement| {
                                unsigned_announcement.short_channel_id = scid;
                        }, node_1_privkey, node_2_privkey, &secp_ctx);
                        match gossip_sync.handle_channel_announcement(&valid_announcement) {
                                Ok(_) => (),
                                _ => panic!()
                        };
                }

                // Error when number_of_blocks=0
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 0,
                                number_of_blocks: 0,
                        },
                        false,
                        vec![ReplyChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 0,
                                number_of_blocks: 0,
                                sync_complete: true,
                                short_channel_ids: vec![]
                        }]
                );

                // Error when wrong chain
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: ChainHash::using_genesis_block(Network::Bitcoin),
                                first_blocknum: 0,
                                number_of_blocks: 0xffff_ffff,
                        },
                        false,
                        vec![ReplyChannelRange {
                                chain_hash: ChainHash::using_genesis_block(Network::Bitcoin),
                                first_blocknum: 0,
                                number_of_blocks: 0xffff_ffff,
                                sync_complete: true,
                                short_channel_ids: vec![],
                        }]
                );

                // Error when first_blocknum > 0xffffff
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 0x01000000,
                                number_of_blocks: 0xffff_ffff,
                        },
                        false,
                        vec![ReplyChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 0x01000000,
                                number_of_blocks: 0xffff_ffff,
                                sync_complete: true,
                                short_channel_ids: vec![]
                        }]
                );

                // Empty reply when max valid SCID block num
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 0xffffff,
                                number_of_blocks: 1,
                        },
                        true,
                        vec![
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 0xffffff,
                                        number_of_blocks: 1,
                                        sync_complete: true,
                                        short_channel_ids: vec![]
                                },
                        ]
                );

                // No results in valid query range
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 1000,
                                number_of_blocks: 1000,
                        },
                        true,
                        vec![
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 1000,
                                        number_of_blocks: 1000,
                                        sync_complete: true,
                                        short_channel_ids: vec![],
                                }
                        ]
                );

                // Overflow first_blocknum + number_of_blocks
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 0xfe0000,
                                number_of_blocks: 0xffffffff,
                        },
                        true,
                        vec![
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 0xfe0000,
                                        number_of_blocks: 0xffffffff - 0xfe0000,
                                        sync_complete: true,
                                        short_channel_ids: vec![
                                                0xfffffe_ffffff_ffff, // max
                                        ]
                                }
                        ]
                );

                // Single block exactly full
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 100000,
                                number_of_blocks: 8000,
                        },
                        true,
                        vec![
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 100000,
                                        number_of_blocks: 8000,
                                        sync_complete: true,
                                        short_channel_ids: (100000..=107999)
                                                .map(|block| scid_from_parts(block, 0, 0).unwrap())
                                                .collect(),
                                },
                        ]
                );

                // Multiple split on new block
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 100000,
                                number_of_blocks: 8001,
                        },
                        true,
                        vec![
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 100000,
                                        number_of_blocks: 7999,
                                        sync_complete: false,
                                        short_channel_ids: (100000..=107999)
                                                .map(|block| scid_from_parts(block, 0, 0).unwrap())
                                                .collect(),
                                },
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 107999,
                                        number_of_blocks: 2,
                                        sync_complete: true,
                                        short_channel_ids: vec![
                                                scid_from_parts(108000, 0, 0).unwrap(),
                                        ],
                                }
                        ]
                );

                // Multiple split on same block
                do_handling_query_channel_range(
                        &gossip_sync,
                        &node_id_2,
                        QueryChannelRange {
                                chain_hash: chain_hash.clone(),
                                first_blocknum: 100002,
                                number_of_blocks: 8000,
                        },
                        true,
                        vec![
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 100002,
                                        number_of_blocks: 7999,
                                        sync_complete: false,
                                        short_channel_ids: (100002..=108001)
                                                .map(|block| scid_from_parts(block, 0, 0).unwrap())
                                                .collect(),
                                },
                                ReplyChannelRange {
                                        chain_hash: chain_hash.clone(),
                                        first_blocknum: 108001,
                                        number_of_blocks: 1,
                                        sync_complete: true,
                                        short_channel_ids: vec![
                                                scid_from_parts(108001, 1, 0).unwrap(),
                                        ],
                                }
                        ]
                );
        }

        fn do_handling_query_channel_range(
                gossip_sync: &P2PGossipSync<&NetworkGraph<Arc<test_utils::TestLogger>>, Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
                test_node_id: &PublicKey,
                msg: QueryChannelRange,
                expected_ok: bool,
                expected_replies: Vec<ReplyChannelRange>
        ) {
                let mut max_firstblocknum = msg.first_blocknum.saturating_sub(1);
                let mut c_lightning_0_9_prev_end_blocknum = max_firstblocknum;
                let query_end_blocknum = msg.end_blocknum();
                let result = gossip_sync.handle_query_channel_range(test_node_id, msg);

                if expected_ok {
                        assert!(result.is_ok());
                } else {
                        assert!(result.is_err());
                }

                let events = gossip_sync.get_and_clear_pending_msg_events();
                assert_eq!(events.len(), expected_replies.len());

                for i in 0..events.len() {
                        let expected_reply = &expected_replies[i];
                        match &events[i] {
                                MessageSendEvent::SendReplyChannelRange { node_id, msg } => {
                                        assert_eq!(node_id, test_node_id);
                                        assert_eq!(msg.chain_hash, expected_reply.chain_hash);
                                        assert_eq!(msg.first_blocknum, expected_reply.first_blocknum);
                                        assert_eq!(msg.number_of_blocks, expected_reply.number_of_blocks);
                                        assert_eq!(msg.sync_complete, expected_reply.sync_complete);
                                        assert_eq!(msg.short_channel_ids, expected_reply.short_channel_ids);

                                        // Enforce exactly the sequencing requirements present on c-lightning v0.9.3
                                        assert!(msg.first_blocknum == c_lightning_0_9_prev_end_blocknum || msg.first_blocknum == c_lightning_0_9_prev_end_blocknum.saturating_add(1));
                                        assert!(msg.first_blocknum >= max_firstblocknum);
                                        max_firstblocknum = msg.first_blocknum;
                                        c_lightning_0_9_prev_end_blocknum = msg.first_blocknum.saturating_add(msg.number_of_blocks);

                                        // Check that the last block count is >= the query's end_blocknum
                                        if i == events.len() - 1 {
                                                assert!(msg.first_blocknum.saturating_add(msg.number_of_blocks) >= query_end_blocknum);
                                        }
                                },
                                _ => panic!("expected MessageSendEvent::SendReplyChannelRange"),
                        }
                }
        }

        #[test]
        fn handling_query_short_channel_ids() {
                let network_graph = create_network_graph();
                let (secp_ctx, gossip_sync) = create_gossip_sync(&network_graph);
                let node_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
                let node_id = PublicKey::from_secret_key(&secp_ctx, node_privkey);

                let chain_hash = ChainHash::using_genesis_block(Network::Testnet);

                let result = gossip_sync.handle_query_short_channel_ids(&node_id, QueryShortChannelIds {
                        chain_hash,
                        short_channel_ids: vec![0x0003e8_000000_0000],
                });
                assert!(result.is_err());
        }

        #[test]
        fn displays_node_alias() {
                let format_str_alias = |alias: &str| {
                        let mut bytes = [0u8; 32];
                        bytes[..alias.as_bytes().len()].copy_from_slice(alias.as_bytes());
                        format!("{}", NodeAlias(bytes))
                };

                assert_eq!(format_str_alias("I\u{1F496}LDK! \u{26A1}"), "I\u{1F496}LDK! \u{26A1}");
                assert_eq!(format_str_alias("I\u{1F496}LDK!\0\u{26A1}"), "I\u{1F496}LDK!");
                assert_eq!(format_str_alias("I\u{1F496}LDK!\t\u{26A1}"), "I\u{1F496}LDK!\u{FFFD}\u{26A1}");

                let format_bytes_alias = |alias: &[u8]| {
                        let mut bytes = [0u8; 32];
                        bytes[..alias.len()].copy_from_slice(alias);
                        format!("{}", NodeAlias(bytes))
                };

                assert_eq!(format_bytes_alias(b"\xFFI <heart> LDK!"), "\u{FFFD}I <heart> LDK!");
                assert_eq!(format_bytes_alias(b"\xFFI <heart>\0LDK!"), "\u{FFFD}I <heart>");
                assert_eq!(format_bytes_alias(b"\xFFI <heart>\tLDK!"), "\u{FFFD}I <heart>\u{FFFD}LDK!");
        }

        #[test]
        fn channel_info_is_readable() {
                let chanmon_cfgs = crate::ln::functional_test_utils::create_chanmon_cfgs(2);
                let node_cfgs = crate::ln::functional_test_utils::create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = crate::ln::functional_test_utils::create_node_chanmgrs(2, &node_cfgs, &[None, None, None, None]);
                let nodes = crate::ln::functional_test_utils::create_network(2, &node_cfgs, &node_chanmgrs);
                let config = crate::ln::functional_test_utils::test_default_channel_config();

                // 1. Test encoding/decoding of ChannelUpdateInfo
                let chan_update_info = ChannelUpdateInfo {
                        last_update: 23,
                        enabled: true,
                        cltv_expiry_delta: 42,
                        htlc_minimum_msat: 1234,
                        htlc_maximum_msat: 5678,
                        fees: RoutingFees { base_msat: 9, proportional_millionths: 10 },
                        last_update_message: None,
                };

                let mut encoded_chan_update_info: Vec<u8> = Vec::new();
                assert!(chan_update_info.write(&mut encoded_chan_update_info).is_ok());

                // First make sure we can read ChannelUpdateInfos we just wrote
                let read_chan_update_info: ChannelUpdateInfo = crate::util::ser::Readable::read(&mut encoded_chan_update_info.as_slice()).unwrap();
                assert_eq!(chan_update_info, read_chan_update_info);

                // Check the serialization hasn't changed.
                let legacy_chan_update_info_with_some: Vec<u8> = <Vec<u8>>::from_hex("340004000000170201010402002a060800000000000004d2080909000000000000162e0a0d0c00040000000902040000000a0c0100").unwrap();
                assert_eq!(encoded_chan_update_info, legacy_chan_update_info_with_some);

                // Check we fail if htlc_maximum_msat is not present in either the ChannelUpdateInfo itself
                // or the ChannelUpdate enclosed with `last_update_message`.
                let legacy_chan_update_info_with_some_and_fail_update: Vec<u8> = <Vec<u8>>::from_hex("b40004000000170201010402002a060800000000000004d2080909000000000000162e0a0d0c00040000000902040000000a0c8181d977cb9b53d93a6ff64bb5f1e158b4094b66e798fb12911168a3ccdf80a83096340a6a95da0ae8d9f776528eecdbb747eb6b545495a4319ed5378e35b21e073a000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f00083a840000034d013413a70000009000000000000f42400000271000000014").unwrap();
                let read_chan_update_info_res: Result<ChannelUpdateInfo, crate::ln::msgs::DecodeError> = crate::util::ser::Readable::read(&mut legacy_chan_update_info_with_some_and_fail_update.as_slice());
                assert!(read_chan_update_info_res.is_err());

                let legacy_chan_update_info_with_none: Vec<u8> = <Vec<u8>>::from_hex("2c0004000000170201010402002a060800000000000004d20801000a0d0c00040000000902040000000a0c0100").unwrap();
                let read_chan_update_info_res: Result<ChannelUpdateInfo, crate::ln::msgs::DecodeError> = crate::util::ser::Readable::read(&mut legacy_chan_update_info_with_none.as_slice());
                assert!(read_chan_update_info_res.is_err());

                // 2. Test encoding/decoding of ChannelInfo
                // Check we can encode/decode ChannelInfo without ChannelUpdateInfo fields present.
                let chan_info_none_updates = ChannelInfo {
                        features: channelmanager::provided_channel_features(&config),
                        node_one: NodeId::from_pubkey(&nodes[0].node.get_our_node_id()),
                        one_to_two: None,
                        node_two: NodeId::from_pubkey(&nodes[1].node.get_our_node_id()),
                        two_to_one: None,
                        capacity_sats: None,
                        announcement_message: None,
                        announcement_received_time: 87654,
                        node_one_counter: 0,
                        node_two_counter: 1,
                };

                let mut encoded_chan_info: Vec<u8> = Vec::new();
                assert!(chan_info_none_updates.write(&mut encoded_chan_info).is_ok());

                let read_chan_info: ChannelInfo = crate::util::ser::Readable::read(&mut encoded_chan_info.as_slice()).unwrap();
                assert_eq!(chan_info_none_updates, read_chan_info);

                // Check we can encode/decode ChannelInfo with ChannelUpdateInfo fields present.
                let chan_info_some_updates = ChannelInfo {
                        features: channelmanager::provided_channel_features(&config),
                        node_one: NodeId::from_pubkey(&nodes[0].node.get_our_node_id()),
                        one_to_two: Some(chan_update_info.clone()),
                        node_two: NodeId::from_pubkey(&nodes[1].node.get_our_node_id()),
                        two_to_one: Some(chan_update_info.clone()),
                        capacity_sats: None,
                        announcement_message: None,
                        announcement_received_time: 87654,
                        node_one_counter: 0,
                        node_two_counter: 1,
                };

                let mut encoded_chan_info: Vec<u8> = Vec::new();
                assert!(chan_info_some_updates.write(&mut encoded_chan_info).is_ok());

                let read_chan_info: ChannelInfo = crate::util::ser::Readable::read(&mut encoded_chan_info.as_slice()).unwrap();
                assert_eq!(chan_info_some_updates, read_chan_info);

                // Check the serialization hasn't changed.
                let legacy_chan_info_with_some: Vec<u8> = <Vec<u8>>::from_hex("ca00020000010800000000000156660221027f921585f2ac0c7c70e36110adecfd8fd14b8a99bfb3d000a283fcac358fce88043636340004000000170201010402002a060800000000000004d2080909000000000000162e0a0d0c00040000000902040000000a0c010006210355f8d2238a322d16b602bd0ceaad5b01019fb055971eaadcc9b29226a4da6c23083636340004000000170201010402002a060800000000000004d2080909000000000000162e0a0d0c00040000000902040000000a0c01000a01000c0100").unwrap();
                assert_eq!(encoded_chan_info, legacy_chan_info_with_some);

                // Check we can decode legacy ChannelInfo, even if the `two_to_one` / `one_to_two` /
                // `last_update_message` fields fail to decode due to missing htlc_maximum_msat.
                let legacy_chan_info_with_some_and_fail_update = <Vec<u8>>::from_hex("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").unwrap();
                let read_chan_info: ChannelInfo = crate::util::ser::Readable::read(&mut legacy_chan_info_with_some_and_fail_update.as_slice()).unwrap();
                assert_eq!(read_chan_info.announcement_received_time, 87654);
                assert_eq!(read_chan_info.one_to_two, None);
                assert_eq!(read_chan_info.two_to_one, None);

                let legacy_chan_info_with_none: Vec<u8> = <Vec<u8>>::from_hex("ba00020000010800000000000156660221027f921585f2ac0c7c70e36110adecfd8fd14b8a99bfb3d000a283fcac358fce88042e2e2c0004000000170201010402002a060800000000000004d20801000a0d0c00040000000902040000000a0c010006210355f8d2238a322d16b602bd0ceaad5b01019fb055971eaadcc9b29226a4da6c23082e2e2c0004000000170201010402002a060800000000000004d20801000a0d0c00040000000902040000000a0c01000a01000c0100").unwrap();
                let read_chan_info: ChannelInfo = crate::util::ser::Readable::read(&mut legacy_chan_info_with_none.as_slice()).unwrap();
                assert_eq!(read_chan_info.announcement_received_time, 87654);
                assert_eq!(read_chan_info.one_to_two, None);
                assert_eq!(read_chan_info.two_to_one, None);
        }

        #[test]
        fn node_info_is_readable() {
                // 1. Check we can read a valid NodeAnnouncementInfo and fail on an invalid one
                let announcement_message = <Vec<u8>>::from_hex("d977cb9b53d93a6ff64bb5f1e158b4094b66e798fb12911168a3ccdf80a83096340a6a95da0ae8d9f776528eecdbb747eb6b545495a4319ed5378e35b21e073a000122013413a7031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f2020201010101010101010101010101010101010101010101010101010101010101010000701fffefdfc2607").unwrap();
                let announcement_message = NodeAnnouncement::read(&mut announcement_message.as_slice()).unwrap();
                let valid_node_ann_info = NodeAnnouncementInfo {
                        features: channelmanager::provided_node_features(&UserConfig::default()),
                        last_update: 0,
                        rgb: [0u8; 3],
                        alias: NodeAlias([0u8; 32]),
                        announcement_message: Some(announcement_message)
                };

                let mut encoded_valid_node_ann_info = Vec::new();
                assert!(valid_node_ann_info.write(&mut encoded_valid_node_ann_info).is_ok());
                let read_valid_node_ann_info = NodeAnnouncementInfo::read(&mut encoded_valid_node_ann_info.as_slice()).unwrap();
                assert_eq!(read_valid_node_ann_info, valid_node_ann_info);
                assert_eq!(read_valid_node_ann_info.addresses().len(), 1);

                let encoded_invalid_node_ann_info = <Vec<u8>>::from_hex("3f0009000788a000080a51a20204000000000403000000062000000000000000000000000000000000000000000000000000000000000000000a0505014004d2").unwrap();
                let read_invalid_node_ann_info_res = NodeAnnouncementInfo::read(&mut encoded_invalid_node_ann_info.as_slice());
                assert!(read_invalid_node_ann_info_res.is_err());

                // 2. Check we can read a NodeInfo anyways, but set the NodeAnnouncementInfo to None if invalid
                let valid_node_info = NodeInfo {
                        channels: Vec::new(),
                        announcement_info: Some(valid_node_ann_info),
                        node_counter: 0,
                };

                let mut encoded_valid_node_info = Vec::new();
                assert!(valid_node_info.write(&mut encoded_valid_node_info).is_ok());
                let read_valid_node_info = NodeInfo::read(&mut encoded_valid_node_info.as_slice()).unwrap();
                assert_eq!(read_valid_node_info, valid_node_info);

                let encoded_invalid_node_info_hex = <Vec<u8>>::from_hex("4402403f0009000788a000080a51a20204000000000403000000062000000000000000000000000000000000000000000000000000000000000000000a0505014004d20400").unwrap();
                let read_invalid_node_info = NodeInfo::read(&mut encoded_invalid_node_info_hex.as_slice()).unwrap();
                assert_eq!(read_invalid_node_info.announcement_info, None);
        }

        #[test]
        fn test_node_info_keeps_compatibility() {
                let old_ann_info_with_addresses = <Vec<u8>>::from_hex("3f0009000708a000080a51220204000000000403000000062000000000000000000000000000000000000000000000000000000000000000000a0505014104d2").unwrap();
                let ann_info_with_addresses = NodeAnnouncementInfo::read(&mut old_ann_info_with_addresses.as_slice())
                                .expect("to be able to read an old NodeAnnouncementInfo with addresses");
                // This serialized info has an address field but no announcement_message, therefore the addresses returned by our function will still be empty
                assert!(ann_info_with_addresses.addresses().is_empty());
        }

        #[test]
        fn test_node_id_display() {
                let node_id = NodeId([42; 33]);
                assert_eq!(format!("{}", &node_id), "2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a");
        }
}

#[cfg(ldk_bench)]
pub mod benches {
        use super::*;
        use std::io::Read;
        use criterion::{black_box, Criterion};

        pub fn read_network_graph(bench: &mut Criterion) {
                let logger = crate::util::test_utils::TestLogger::new();
                let (mut d, _) = crate::routing::router::bench_utils::get_graph_scorer_file().unwrap();
                let mut v = Vec::new();
                d.read_to_end(&mut v).unwrap();
                bench.bench_function("read_network_graph", |b| b.iter(||
                        NetworkGraph::read(&mut std::io::Cursor::new(black_box(&v)), &logger).unwrap()
                ));
        }

        pub fn write_network_graph(bench: &mut Criterion) {
                let logger = crate::util::test_utils::TestLogger::new();
                let (mut d, _) = crate::routing::router::bench_utils::get_graph_scorer_file().unwrap();
                let net_graph = NetworkGraph::read(&mut d, &logger).unwrap();
                bench.bench_function("write_network_graph", |b| b.iter(||
                        black_box(&net_graph).encode()
                ));
        }
}