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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity is free software: you can redistribute it and/or modify
    // it under the terms of the GNU General Public License as published by
    // the Free Software Foundation, either version 3 of the License, or
    // (at your option) any later version.

    // Parity is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.

    // You should have received a copy of the GNU General Public License
    // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

    use util::bytes::Bytes;
    use std::net::SocketAddr;
    use std::collections::{HashSet, HashMap, BTreeMap, VecDeque};
    use std::mem;
    use std::default::Default;
    use mio::*;
    use mio::deprecated::{Handler, EventLoop};
    use mio::udp::*;
    use util::sha3::*;
    use time;
    use util::hash::*;
    use rlp::*;
    use node_table::*;
    use error::NetworkError;
    use io::{StreamToken, IoContext};
    use ethkey::{Secret, KeyPair, sign, recover};
    use AllowIP;

    use PROTOCOL_VERSION;

    const ADDRESS_BYTES_SIZE: u32 = 32;							// Size of address type in bytes.
    const ADDRESS_BITS: u32 = 8 * ADDRESS_BYTES_SIZE;			// Denoted by n in [Kademlia].
    const NODE_BINS: u32 = ADDRESS_BITS - 1;					// Size of m_state (excludes root, which is us).
    const DISCOVERY_MAX_STEPS: u16 = 8;							// Max iterations of discovery. (discover)
    const BUCKET_SIZE: usize = 16;		// Denoted by k in [Kademlia]. Number of nodes stored in each bucket.
    const ALPHA: usize = 3;				// Denoted by \alpha in [Kademlia]. Number of concurrent FindNode requests.
    const MAX_DATAGRAM_SIZE: usize = 1280;

    const PACKET_PING: u8 = 1;
    const PACKET_PONG: u8 = 2;
    const PACKET_FIND_NODE: u8 = 3;
    const PACKET_NEIGHBOURS: u8 = 4;

    const PING_TIMEOUT_MS: u64 = 300;
    const MAX_NODES_PING: usize = 32; // Max nodes to add/ping at once

    #[derive(Clone, Debug)]
    pub struct NodeEntry {
    	pub id: NodeId,
    	pub endpoint: NodeEndpoint,
    }

    pub struct BucketEntry {
    	pub address: NodeEntry,
    	pub id_hash: H256,
    	pub timeout: Option<u64>,
    }

    pub struct NodeBucket {
    	nodes: VecDeque<BucketEntry>, //sorted by last active
    }

    impl Default for NodeBucket {
    	fn default() -> Self {
    		NodeBucket::new()
    	}
    }

    impl NodeBucket {
    	fn new() -> Self {
    		NodeBucket {
    			nodes: VecDeque::new()
    		}
    	}
    }

    struct Datagramm {
    	payload: Bytes,
    	address: SocketAddr,
    }

    pub struct Discovery {
    	id: NodeId,
    	id_hash: H256,
    	secret: Secret,
    	public_endpoint: NodeEndpoint,
    	udp_socket: UdpSocket,
    	token: StreamToken,
    	discovery_round: u16,
    	discovery_id: NodeId,
    	discovery_nodes: HashSet<NodeId>,
    	node_buckets: Vec<NodeBucket>,
    	send_queue: VecDeque<Datagramm>,
    	check_timestamps: bool,
    	adding_nodes: Vec<NodeEntry>,
    	allow_ips: AllowIP,
    }

    pub struct TableUpdates {
    	pub added: HashMap<NodeId, NodeEntry>,
    	pub removed: HashSet<NodeId>,
    }

    impl Discovery {
    	pub fn new(key: &KeyPair, listen: SocketAddr, public: NodeEndpoint, token: StreamToken, allow_ips: AllowIP) -> Discovery {
    		let socket = UdpSocket::bind(&listen).expect("Error binding UDP socket");
    		Discovery {
    			id: key.public().clone(),
    			id_hash: key.public().sha3(),
    			secret: key.secret().clone(),
    			public_endpoint: public,
    			token: token,
    			discovery_round: 0,
    			discovery_id: NodeId::new(),
    			discovery_nodes: HashSet::new(),
    			node_buckets: (0..NODE_BINS).map(|_| NodeBucket::new()).collect(),
    			udp_socket: socket,
    			send_queue: VecDeque::new(),
    			check_timestamps: true,
    			adding_nodes: Vec::new(),
    			allow_ips: allow_ips,
    		}
    	}

    	/// Add a new node to discovery table. Pings the node.
    	pub fn add_node(&mut self, e: NodeEntry) {
    		if self.is_allowed(&e) {
    			let endpoint = e.endpoint.clone();
    			self.update_node(e);
    			self.ping(&endpoint);
    		}
    	}

    	/// Add a list of nodes. Pings a few nodes each round
    	pub fn add_node_list(&mut self, nodes: Vec<NodeEntry>) {
    		self.adding_nodes = nodes;
    		self.update_new_nodes();
    	}

    	/// Add a list of known nodes to the table.
    	pub fn init_node_list(&mut self, mut nodes: Vec<NodeEntry>) {
    		for n in nodes.drain(..) {
    			if self.is_allowed(&n) {
    				self.update_node(n);
    			}
    		}
    	}

    	fn update_node(&mut self, e: NodeEntry) {
    		trace!(target: "discovery", "Inserting {:?}", &e);
    		let id_hash = e.id.sha3();
    		let ping = {
    			let mut bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &id_hash) as usize];
    			let updated = if let Some(node) = bucket.nodes.iter_mut().find(|n| n.address.id == e.id) {
    				node.address = e.clone();
    				node.timeout = None;
    				true
    			} else { false };

    			if !updated {
    				bucket.nodes.push_front(BucketEntry { address: e, timeout: None, id_hash: id_hash, });
    			}

    			if bucket.nodes.len() > BUCKET_SIZE {
    				//ping least active node
    				let mut last = bucket.nodes.back_mut().expect("Last item is always present when len() > 0");
    				last.timeout = Some(time::precise_time_ns());
    				Some(last.address.endpoint.clone())
    			} else { None }
    		};
    		if let Some(endpoint) = ping {
    			self.ping(&endpoint);
    		}
    	}

    	fn clear_ping(&mut self, id: &NodeId) {
    		let mut bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &id.sha3()) as usize];
    		if let Some(node) = bucket.nodes.iter_mut().find(|n| &n.address.id == id) {
    			node.timeout = None;
    		}
    	}

    	fn start(&mut self) {
    		trace!(target: "discovery", "Starting discovery");
    		self.discovery_round = 0;
    		self.discovery_id.randomize(); //TODO: use cryptographic nonce
    		self.discovery_nodes.clear();
    	}

    	fn update_new_nodes(&mut self) {
    		let mut count = 0usize;
    		while !self.adding_nodes.is_empty() && count < MAX_NODES_PING {
    			let node = self.adding_nodes.pop().expect("pop is always Some if not empty; qed");
    			self.add_node(node);
    			count += 1;
    		}
    	}

    	fn discover(&mut self) {
    		self.update_new_nodes();
    		if self.discovery_round == DISCOVERY_MAX_STEPS {
    			return;
    		}
    		trace!(target: "discovery", "Starting round {:?}", self.discovery_round);
    		let mut tried_count = 0;
    		{
    			let nearest = Discovery::nearest_node_entries(&self.discovery_id, &self.node_buckets).into_iter();
    			let nearest = nearest.filter(|x| !self.discovery_nodes.contains(&x.id)).take(ALPHA).collect::<Vec<_>>();
    			for r in nearest {
    				let rlp = encode(&(&[self.discovery_id.clone()][..]));
    				self.send_packet(PACKET_FIND_NODE, &r.endpoint.udp_address(), &rlp);
    				self.discovery_nodes.insert(r.id.clone());
    				tried_count += 1;
    				trace!(target: "discovery", "Sent FindNode to {:?}", &r.endpoint);
    			}
    		}

    		if tried_count == 0 {
    			trace!(target: "discovery", "Completing discovery");
    			self.discovery_round = DISCOVERY_MAX_STEPS;
    			self.discovery_nodes.clear();
    			return;
    		}
    		self.discovery_round += 1;
    	}

    	fn distance(a: &H256, b: &H256) -> u32 {
    		let d = *a ^ *b;
    		let mut ret:u32 = 0;
    		for i in 0..32 {
    			let mut v: u8 = d[i];
    			while v != 0 {
    				v >>= 1;
    				ret += 1;
    			}
    		}
    		ret
    	}

    	fn ping(&mut self, node: &NodeEndpoint) {
    		let mut rlp = RlpStream::new_list(3);
    		rlp.append(&PROTOCOL_VERSION);
    		self.public_endpoint.to_rlp_list(&mut rlp);
    		node.to_rlp_list(&mut rlp);
    		trace!(target: "discovery", "Sent Ping to {:?}", &node);
    		self.send_packet(PACKET_PING, &node.udp_address(), &rlp.drain());
    	}

    	fn send_packet(&mut self, packet_id: u8, address: &SocketAddr, payload: &[u8]) {
    		let mut rlp = RlpStream::new();
    		rlp.append_raw(&[packet_id], 1);
    		let source = Rlp::new(payload);
    		rlp.begin_list(source.item_count() + 1);
    		for i in 0 .. source.item_count() {
    			rlp.append_raw(source.at(i).as_raw(), 1);
    		}
    		let timestamp = time::get_time().sec as u32 + 60;
    		rlp.append(&timestamp);

    		let bytes = rlp.drain();
    		let hash = bytes.as_ref().sha3();
    		let signature = match sign(&self.secret, &hash) {
    			Ok(s) => s,
    			Err(_) => {
    				warn!("Error signing UDP packet");
    				return;
    			}
    		};
    		let mut packet = Bytes::with_capacity(bytes.len() + 32 + 65);
    		packet.extend(hash.iter());
    		packet.extend(signature.iter());
    		packet.extend(bytes.iter());
    		let signed_hash = (&packet[32..]).sha3();
    		packet[0..32].clone_from_slice(&signed_hash);
    		self.send_to(packet, address.clone());
    	}

    	#[cfg_attr(feature="dev", allow(map_clone))]
    	fn nearest_node_entries(target: &NodeId, buckets: &[NodeBucket]) -> Vec<NodeEntry> {
    		let mut found: BTreeMap<u32, Vec<&NodeEntry>> = BTreeMap::new();
    		let mut count = 0;
    		let target_hash = target.sha3();

    		// Sort nodes by distance to target
    		for bucket in buckets {
    			for node in &bucket.nodes {
    				let distance = Discovery::distance(&target_hash, &node.id_hash);
    				found.entry(distance).or_insert_with(Vec::new).push(&node.address);
    				if count == BUCKET_SIZE {
    					// delete the most distant element
    					let remove = {
    						let (key, last) = found.iter_mut().next_back().expect("Last element is always Some when count > 0");
    						last.pop();
    						if last.is_empty() { Some(key.clone()) } else { None }
    					};
    					if let Some(remove) = remove {
    						found.remove(&remove);
    					}
    				}
    				else {
    					count += 1;
    				}
    			}
    		}

    		let mut ret:Vec<NodeEntry> = Vec::new();
    		for nodes in found.values() {
    			ret.extend(nodes.iter().map(|&n| n.clone()));
    		}
    		ret
    	}

    	pub fn writable<Message>(&mut self, io: &IoContext<Message>) where Message: Send + Sync + Clone {
    		while let Some(data) = self.send_queue.pop_front() {
    			match self.udp_socket.send_to(&data.payload, &data.address) {
    				Ok(Some(size)) if size == data.payload.len() => {
    				},
    				Ok(Some(_)) => {
    					warn!("UDP sent incomplete datagramm");
    				},
    				Ok(None) => {
    					self.send_queue.push_front(data);
    					return;
    				}
    				Err(e) => {
    					debug!("UDP send error: {:?}, address: {:?}", e, &data.address);
    					return;
    				}
    			}
    		}
    		io.update_registration(self.token).unwrap_or_else(|e| debug!("Error updating discovery registration: {:?}", e));
    	}

    	fn send_to(&mut self, payload: Bytes, address: SocketAddr) {
    		self.send_queue.push_back(Datagramm { payload: payload, address: address });
    	}

    	pub fn readable<Message>(&mut self, io: &IoContext<Message>) -> Option<TableUpdates> where Message: Send + Sync + Clone {
    		let mut buf: [u8; MAX_DATAGRAM_SIZE] = unsafe { mem::uninitialized() };
    		let writable = !self.send_queue.is_empty();
    		let res = match self.udp_socket.recv_from(&mut buf) {
    			Ok(Some((len, address))) => self.on_packet(&buf[0..len], address).unwrap_or_else(|e| {
    				debug!("Error processing UDP packet: {:?}", e);
    				None
    			}),
    			Ok(_) => None,
    			Err(e) => {
    				debug!("Error reading UPD socket: {:?}", e);
    				None
    			}
    		};
    		let new_writable = !self.send_queue.is_empty();
    		if writable != new_writable {
    			io.update_registration(self.token).unwrap_or_else(|e| debug!("Error updating discovery registration: {:?}", e));
    		}
    		res
    	}

    	fn on_packet(&mut self, packet: &[u8], from: SocketAddr) -> Result<Option<TableUpdates>, NetworkError> {
    		// validate packet
    		if packet.len() < 32 + 65 + 4 + 1 {
    			return Err(NetworkError::BadProtocol);
    		}

    		let hash_signed = (&packet[32..]).sha3();
    		if hash_signed[..] != packet[0..32] {
    			return Err(NetworkError::BadProtocol);
    		}

    		let signed = &packet[(32 + 65)..];
    		let signature = H520::from_slice(&packet[32..(32 + 65)]);
    		let node_id = recover(&signature.into(), &signed.sha3())?;

    		let packet_id = signed[0];
    		let rlp = UntrustedRlp::new(&signed[1..]);
    		match packet_id {
    			PACKET_PING => self.on_ping(&rlp, &node_id, &from),
    			PACKET_PONG => self.on_pong(&rlp, &node_id, &from),
    			PACKET_FIND_NODE => self.on_find_node(&rlp, &node_id, &from),
    			PACKET_NEIGHBOURS => self.on_neighbours(&rlp, &node_id, &from),
    			_ => {
    				debug!("Unknown UDP packet: {}", packet_id);
    				Ok(None)
    			}
    		}
    	}

    	fn check_timestamp(&self, timestamp: u64) -> Result<(), NetworkError> {
    		if self.check_timestamps && timestamp < time::get_time().sec as u64{
    			debug!(target: "discovery", "Expired packet");
    			return Err(NetworkError::Expired);
    		}
    		Ok(())
    	}

    	fn is_allowed(&self, entry: &NodeEntry) -> bool {
    		entry.endpoint.is_allowed(self.allow_ips) && entry.id != self.id
    	}

    	fn on_ping(&mut self, rlp: &UntrustedRlp, node: &NodeId, from: &SocketAddr) -> Result<Option<TableUpdates>, NetworkError> {
    		trace!(target: "discovery", "Got Ping from {:?}", &from);
    		let source = NodeEndpoint::from_rlp(&rlp.at(1)?)?;
    		let dest = NodeEndpoint::from_rlp(&rlp.at(2)?)?;
    		let timestamp: u64 = rlp.val_at(3)?;
    		self.check_timestamp(timestamp)?;
    		let mut added_map = HashMap::new();
    		let entry = NodeEntry { id: node.clone(), endpoint: source.clone() };
    		if !entry.endpoint.is_valid() {
    			debug!(target: "discovery", "Got bad address: {:?}", entry);
    		} else if !self.is_allowed(&entry) {
    			debug!(target: "discovery", "Address not allowed: {:?}", entry);
    		} else {
    			self.update_node(entry.clone());
    			added_map.insert(node.clone(), entry);
    		}
    		let hash = rlp.as_raw().sha3();
    		let mut response = RlpStream::new_list(2);
    		dest.to_rlp_list(&mut response);
    		response.append(&hash);
    		self.send_packet(PACKET_PONG, from, &response.drain());

    		Ok(Some(TableUpdates { added: added_map, removed: HashSet::new() }))
    	}

    	fn on_pong(&mut self, rlp: &UntrustedRlp, node: &NodeId, from: &SocketAddr) -> Result<Option<TableUpdates>, NetworkError> {
    		trace!(target: "discovery", "Got Pong from {:?}", &from);
    		// TODO: validate pong packet
    		let dest = NodeEndpoint::from_rlp(&rlp.at(0)?)?;
    		let timestamp: u64 = rlp.val_at(2)?;
    		self.check_timestamp(timestamp)?;
    		let mut entry = NodeEntry { id: node.clone(), endpoint: dest };
    		if !entry.endpoint.is_valid() {
    			debug!(target: "discovery", "Bad address: {:?}", entry);
    			entry.endpoint.address = from.clone();
    		}
    		self.clear_ping(node);
    		let mut added_map = HashMap::new();
    		added_map.insert(node.clone(), entry);
    		Ok(None)
    	}

    	fn on_find_node(&mut self, rlp: &UntrustedRlp, _node: &NodeId, from: &SocketAddr) -> Result<Option<TableUpdates>, NetworkError> {
    		trace!(target: "discovery", "Got FindNode from {:?}", &from);
    		let target: NodeId = rlp.val_at(0)?;
    		let timestamp: u64 = rlp.val_at(1)?;
    		self.check_timestamp(timestamp)?;
    		let nearest = Discovery::nearest_node_entries(&target, &self.node_buckets);
    		if nearest.is_empty() {
    			return Ok(None);
    		}
    		let mut packets = Discovery::prepare_neighbours_packets(&nearest);
    		for p in packets.drain(..) {
    			self.send_packet(PACKET_NEIGHBOURS, from, &p);
    		}
    		trace!(target: "discovery", "Sent {} Neighbours to {:?}", nearest.len(), &from);
    		Ok(None)
    	}

    	fn prepare_neighbours_packets(nearest: &[NodeEntry]) -> Vec<Bytes> {
    		let limit = (MAX_DATAGRAM_SIZE - 109) / 90;
    		let chunks = nearest.chunks(limit);
    		let packets = chunks.map(|c| {
    			let mut rlp = RlpStream::new_list(1);
    			rlp.begin_list(c.len());
    			for n in 0 .. c.len() {
    				rlp.begin_list(4);
    				c[n].endpoint.to_rlp(&mut rlp);
    				rlp.append(&c[n].id);
    			}
    			rlp.out()
    		});
    		packets.collect()
    	}

    	fn on_neighbours(&mut self, rlp: &UntrustedRlp, _node: &NodeId, from: &SocketAddr) -> Result<Option<TableUpdates>, NetworkError> {
    		// TODO: validate packet
    		let mut added = HashMap::new();
    		trace!(target: "discovery", "Got {} Neighbours from {:?}", rlp.at(0)?.item_count(), &from);
    		for r in rlp.at(0)?.iter() {
    			let endpoint = NodeEndpoint::from_rlp(&r)?;
    			if !endpoint.is_valid() {
    				debug!(target: "discovery", "Bad address: {:?}", endpoint);
    				continue;
    			}
    			let node_id: NodeId = r.val_at(3)?;
    			if node_id == self.id {
    				continue;
    			}
    			let entry = NodeEntry { id: node_id.clone(), endpoint: endpoint };
    			if !self.is_allowed(&entry) {
    				debug!(target: "discovery", "Address not allowed: {:?}", entry);
    				continue;
    			}
    			added.insert(node_id, entry.clone());
    			self.ping(&entry.endpoint);
    			self.update_node(entry);
    		}
    		Ok(Some(TableUpdates { added: added, removed: HashSet::new() }))
    	}

    	fn check_expired(&mut self, force: bool) -> HashSet<NodeId> {
    		let now = time::precise_time_ns();
    		let mut removed: HashSet<NodeId> = HashSet::new();
    		for bucket in &mut self.node_buckets {
    			bucket.nodes.retain(|node| {
    				if let Some(timeout) = node.timeout {
    					if !force && now - timeout < PING_TIMEOUT_MS * 1000_0000 {
    						true
    					}
    					else {
    						trace!(target: "discovery", "Removed expired node {:?}", &node.address);
    						removed.insert(node.address.id.clone());
    						false
    					}
    				} else { true }
    			});
    		}
    		removed
    	}

    	pub fn round(&mut self) -> Option<TableUpdates> {
    		let removed = self.check_expired(false);
    		self.discover();
    		if !removed.is_empty() {
    			Some(TableUpdates { added: HashMap::new(), removed: removed })
    		} else { None }
    	}

    	pub fn refresh(&mut self) {
    		self.start();
    	}

    	pub fn register_socket<Host:Handler>(&self, event_loop: &mut EventLoop<Host>) -> Result<(), NetworkError> {
    		event_loop.register(&self.udp_socket, Token(self.token), Ready::all(), PollOpt::edge()).expect("Error registering UDP socket");
    		Ok(())
    	}

    	pub fn update_registration<Host:Handler>(&self, event_loop: &mut EventLoop<Host>) -> Result<(), NetworkError> {
    		let registration = if !self.send_queue.is_empty() {
    			Ready::readable() | Ready::writable()
    		} else {
    			Ready::readable()
    		};
    		event_loop.reregister(&self.udp_socket, Token(self.token), registration, PollOpt::edge()).expect("Error reregistering UDP socket");
    		Ok(())
    	}
    }

    #[cfg(test)]
    mod tests {
    	use super::*;
    	use std::net::{SocketAddr};
    	use util::sha3::Hashable;
    	use util::FixedHash;
    	use node_table::{Node, NodeId, NodeEndpoint};

    	use std::str::FromStr;
    	use rustc_serialize::hex::FromHex;
    	use ethkey::{Random, Generator};
    	use AllowIP;

    	#[test]
    	fn find_node() {
    		let mut nearest = Vec::new();
    		let node = Node::from_str("enode://a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@127.0.0.1:7770").unwrap();
    		for _ in 0..1000 {
    			nearest.push( NodeEntry { id: node.id.clone(), endpoint: node.endpoint.clone() });
    		}

    		let packets = Discovery::prepare_neighbours_packets(&nearest);
    		assert_eq!(packets.len(), 77);
    		for p in &packets[0..76] {
    			assert!(p.len() > 1280/2);
    			assert!(p.len() <= 1280);
    		}
    		assert!(packets.last().unwrap().len() > 0);
    	}

    	#[test]
    	fn discovery() {
    		let key1 = Random.generate().unwrap();
    		let key2 = Random.generate().unwrap();
    		let ep1 = NodeEndpoint { address: SocketAddr::from_str("127.0.0.1:40444").unwrap(), udp_port: 40444 };
    		let ep2 = NodeEndpoint { address: SocketAddr::from_str("127.0.0.1:40445").unwrap(), udp_port: 40445 };
    		let mut discovery1 = Discovery::new(&key1, ep1.address.clone(), ep1.clone(), 0, AllowIP::All);
    		let mut discovery2 = Discovery::new(&key2, ep2.address.clone(), ep2.clone(), 0, AllowIP::All);

    		let node1 = Node::from_str("enode://a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@127.0.0.1:7770").unwrap();
    		let node2 = Node::from_str("enode://b979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@127.0.0.1:7771").unwrap();
    		discovery1.add_node(NodeEntry { id: node1.id.clone(), endpoint: node1.endpoint.clone() });
    		discovery1.add_node(NodeEntry { id: node2.id.clone(), endpoint: node2.endpoint.clone() });

    		discovery2.add_node(NodeEntry { id: key1.public().clone(), endpoint: ep1.clone() });
    		discovery2.refresh();

    		for _ in 0 .. 10 {
    			while !discovery1.send_queue.is_empty() {
    				let datagramm = discovery1.send_queue.pop_front().unwrap();
    				if datagramm.address == ep2.address {
    					discovery2.on_packet(&datagramm.payload, ep1.address.clone()).ok();
    				}
    			}
    			while !discovery2.send_queue.is_empty() {
    				let datagramm = discovery2.send_queue.pop_front().unwrap();
    				if datagramm.address == ep1.address {
    					discovery1.on_packet(&datagramm.payload, ep2.address.clone()).ok();
    				}
    			}
    			discovery2.round();
    		}
    		assert_eq!(Discovery::nearest_node_entries(&NodeId::new(), &discovery2.node_buckets).len(), 3)
    	}

    	#[test]
    	fn removes_expired() {
    		let key = Random.generate().unwrap();
    		let ep = NodeEndpoint { address: SocketAddr::from_str("127.0.0.1:40446").unwrap(), udp_port: 40447 };
    		let mut discovery = Discovery::new(&key, ep.address.clone(), ep.clone(), 0, AllowIP::All);
    		for _ in 0..1200 {
    			discovery.add_node(NodeEntry { id: NodeId::random(), endpoint: ep.clone() });
    		}
    		assert!(Discovery::nearest_node_entries(&NodeId::new(), &discovery.node_buckets).len() <= 16);
    		let removed = discovery.check_expired(true).len();
    		assert!(removed > 0);
    	}

    	#[test]
    	fn find_nearest_saturated() {
    		use super::*;
    		let mut buckets: Vec<_> = (0..256).map(|_| NodeBucket::new()).collect();
    		let ep = NodeEndpoint { address: SocketAddr::from_str("127.0.0.1:40447").unwrap(), udp_port: 40447 };
    		for _ in 0..(16 + 10) {
    			buckets[0].nodes.push_back(BucketEntry {
    				address: NodeEntry { id: NodeId::new(), endpoint: ep.clone() },
    				timeout: None,
    				id_hash: NodeId::new().sha3(),
    			});
    		}
    		let nearest = Discovery::nearest_node_entries(&NodeId::new(), &buckets);
    		assert_eq!(nearest.len(), 16)
    	}

    	#[test]
    	fn packets() {
    		let key = Random.generate().unwrap();
    		let ep = NodeEndpoint { address: SocketAddr::from_str("127.0.0.1:40447").unwrap(), udp_port: 40447 };
    		let mut discovery = Discovery::new(&key, ep.address.clone(), ep.clone(), 0, AllowIP::All);
    		discovery.check_timestamps = false;
    		let from = SocketAddr::from_str("99.99.99.99:40445").unwrap();

    		let packet = "\
    		e9614ccfd9fc3e74360018522d30e1419a143407ffcce748de3e22116b7e8dc92ff74788c0b6663a\
    		aa3d67d641936511c8f8d6ad8698b820a7cf9e1be7155e9a241f556658c55428ec0563514365799a\
    		4be2be5a685a80971ddcfa80cb422cdd0101ec04cb847f000001820cfa8215a8d790000000000000\
    		000000000000000000018208ae820d058443b9a3550102\
    		".from_hex().unwrap();
    		assert!(discovery.on_packet(&packet, from.clone()).is_ok());

    		let packet = "\
    		577be4349c4dd26768081f58de4c6f375a7a22f3f7adda654d1428637412c3d7fe917cadc56d4e5e\
    		7ffae1dbe3efffb9849feb71b262de37977e7c7a44e677295680e9e38ab26bee2fcbae207fba3ff3\
    		d74069a50b902a82c9903ed37cc993c50001f83e82022bd79020010db83c4d001500000000abcdef\
    		12820cfa8215a8d79020010db885a308d313198a2e037073488208ae82823a8443b9a355c5010203\
    		040531b9019afde696e582a78fa8d95ea13ce3297d4afb8ba6433e4154caa5ac6431af1b80ba7602\
    		3fa4090c408f6b4bc3701562c031041d4702971d102c9ab7fa5eed4cd6bab8f7af956f7d565ee191\
    		7084a95398b6a21eac920fe3dd1345ec0a7ef39367ee69ddf092cbfe5b93e5e568ebc491983c09c7\
    		6d922dc3\
    		".from_hex().unwrap();
    		assert!(discovery.on_packet(&packet, from.clone()).is_ok());

    		let packet = "\
    		09b2428d83348d27cdf7064ad9024f526cebc19e4958f0fdad87c15eb598dd61d08423e0bf66b206\
    		9869e1724125f820d851c136684082774f870e614d95a2855d000f05d1648b2d5945470bc187c2d2\
    		216fbe870f43ed0909009882e176a46b0102f846d79020010db885a308d313198a2e037073488208\
    		ae82823aa0fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c9548443b9\
    		a355c6010203c2040506a0c969a58f6f9095004c0177a6b47f451530cab38966a25cca5cb58f0555
    		42124e\
    		".from_hex().unwrap();
    		assert!(discovery.on_packet(&packet, from.clone()).is_ok());

    		let packet = "\
    		c7c44041b9f7c7e41934417ebac9a8e1a4c6298f74553f2fcfdcae6ed6fe53163eb3d2b52e39fe91\
    		831b8a927bf4fc222c3902202027e5e9eb812195f95d20061ef5cd31d502e47ecb61183f74a504fe\
    		04c51e73df81f25c4d506b26db4517490103f84eb840ca634cae0d49acb401d8a4c6b6fe8c55b70d\
    		115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be0081290476\
    		7bf5ccd1fc7f8443b9a35582999983999999280dc62cc8255c73471e0a61da0c89acdc0e035e260a\
    		dd7fc0c04ad9ebf3919644c91cb247affc82b69bd2ca235c71eab8e49737c937a2c396\
    		".from_hex().unwrap();
    		assert!(discovery.on_packet(&packet, from.clone()).is_ok());

    		let packet = "\
    		c679fc8fe0b8b12f06577f2e802d34f6fa257e6137a995f6f4cbfc9ee50ed3710faf6e66f932c4c8\
    		d81d64343f429651328758b47d3dbc02c4042f0fff6946a50f4a49037a72bb550f3a7872363a83e1\
    		b9ee6469856c24eb4ef80b7535bcf99c0004f9015bf90150f84d846321163782115c82115db84031\
    		55e1427f85f10a5c9a7755877748041af1bcd8d474ec065eb33df57a97babf54bfd2103575fa8291\
    		15d224c523596b401065a97f74010610fce76382c0bf32f84984010203040101b840312c55512422\
    		cf9b8a4097e9a6ad79402e87a15ae909a4bfefa22398f03d20951933beea1e4dfa6f968212385e82\
    		9f04c2d314fc2d4e255e0d3bc08792b069dbf8599020010db83c4d001500000000abcdef12820d05\
    		820d05b84038643200b172dcfef857492156971f0e6aa2c538d8b74010f8e140811d53b98c765dd2\
    		d96126051913f44582e8c199ad7c6d6819e9a56483f637feaac9448aacf8599020010db885a308d3\
    		13198a2e037073488203e78203e8b8408dcab8618c3253b558d459da53bd8fa68935a719aff8b811\
    		197101a4b2b47dd2d47295286fc00cc081bb542d760717d1bdd6bec2c37cd72eca367d6dd3b9df73\
    		8443b9a355010203b525a138aa34383fec3d2719a0\
    		".from_hex().unwrap();
    		assert!(discovery.on_packet(&packet, from.clone()).is_ok());
    	}

    }

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