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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 std::net::{SocketAddr, SocketAddrV4, Ipv4Addr};
    use std::collections::{HashMap, HashSet};
    use std::str::FromStr;
    use std::sync::Arc;
    use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
    use std::ops::*;
    use std::cmp::min;
    use std::path::{Path, PathBuf};
    use std::io::{Read, Write, ErrorKind};
    use std::fs;
    use ethkey::{KeyPair, Secret, Random, Generator};
    use mio::*;
    use mio::deprecated::{EventLoop};
    use mio::tcp::*;
    use util::hash::*;
    use util::Hashable;
    use util::version;
    use rlp::*;
    use session::{Session, SessionInfo, SessionData};
    use error::*;
    use io::*;
    use {NetworkProtocolHandler, NonReservedPeerMode, AllowIP, PROTOCOL_VERSION};
    use node_table::*;
    use stats::NetworkStats;
    use discovery::{Discovery, TableUpdates, NodeEntry};
    use ip_utils::{map_external_address, select_public_address};
    use util::path::restrict_permissions_owner;
    use parking_lot::{Mutex, RwLock};

    type Slab<T> = ::slab::Slab<T, usize>;

    const MAX_SESSIONS: usize = 1024 + MAX_HANDSHAKES;
    const MAX_HANDSHAKES: usize = 1024;

    const DEFAULT_PORT: u16 = 30303;

    // Tokens
    const TCP_ACCEPT: usize = SYS_TIMER + 1;
    const IDLE: usize = SYS_TIMER + 2;
    const DISCOVERY: usize = SYS_TIMER + 3;
    const DISCOVERY_REFRESH: usize = SYS_TIMER + 4;
    const DISCOVERY_ROUND: usize = SYS_TIMER + 5;
    const NODE_TABLE: usize = SYS_TIMER + 6;
    const FIRST_SESSION: usize = 0;
    const LAST_SESSION: usize = FIRST_SESSION + MAX_SESSIONS - 1;
    const USER_TIMER: usize = LAST_SESSION + 256;
    const SYS_TIMER: usize = LAST_SESSION + 1;

    // Timeouts
    const MAINTENANCE_TIMEOUT: u64 = 1000;
    const DISCOVERY_REFRESH_TIMEOUT: u64 = 60_000;
    const DISCOVERY_ROUND_TIMEOUT: u64 = 300;
    const NODE_TABLE_TIMEOUT: u64 = 300_000;

    #[derive(Debug, PartialEq, Clone)]
    /// Network service configuration
    pub struct NetworkConfiguration {
    	/// Directory path to store general network configuration. None means nothing will be saved
    	pub config_path: Option<String>,
    	/// Directory path to store network-specific configuration. None means nothing will be saved
    	pub net_config_path: Option<String>,
    	/// IP address to listen for incoming connections. Listen to all connections by default
    	pub listen_address: Option<SocketAddr>,
    	/// IP address to advertise. Detected automatically if none.
    	pub public_address: Option<SocketAddr>,
    	/// Port for UDP connections, same as TCP by default
    	pub udp_port: Option<u16>,
    	/// Enable NAT configuration
    	pub nat_enabled: bool,
    	/// Enable discovery
    	pub discovery_enabled: bool,
    	/// List of initial node addresses
    	pub boot_nodes: Vec<String>,
    	/// Use provided node key instead of default
    	pub use_secret: Option<Secret>,
    	/// Minimum number of connected peers to maintain
    	pub min_peers: u32,
    	/// Maximum allowed number of peers
    	pub max_peers: u32,
    	/// Maximum handshakes
    	pub max_handshakes: u32,
    	/// Reserved protocols. Peers with <key> protocol get additional <value> connection slots.
    	pub reserved_protocols: HashMap<ProtocolId, u32>,
    	/// List of reserved node addresses.
    	pub reserved_nodes: Vec<String>,
    	/// The non-reserved peer mode.
    	pub non_reserved_mode: NonReservedPeerMode,
    	/// IP filter
    	pub allow_ips: AllowIP,
    }

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

    impl NetworkConfiguration {
    	/// Create a new instance of default settings.
    	pub fn new() -> Self {
    		NetworkConfiguration {
    			config_path: None,
    			net_config_path: None,
    			listen_address: None,
    			public_address: None,
    			udp_port: None,
    			nat_enabled: true,
    			discovery_enabled: true,
    			boot_nodes: Vec::new(),
    			use_secret: None,
    			min_peers: 25,
    			max_peers: 50,
    			max_handshakes: 64,
    			reserved_protocols: HashMap::new(),
    			allow_ips: AllowIP::All,
    			reserved_nodes: Vec::new(),
    			non_reserved_mode: NonReservedPeerMode::Accept,
    		}
    	}

    	/// Create new default configuration with sepcified listen port.
    	pub fn new_with_port(port: u16) -> NetworkConfiguration {
    		let mut config = NetworkConfiguration::new();
    		config.listen_address = Some(SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), port)));
    		config
    	}

    	/// Create new default configuration for localhost-only connection with random port (usefull for testing)
    	pub fn new_local() -> NetworkConfiguration {
    		let mut config = NetworkConfiguration::new();
    		config.listen_address = Some(SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 0)));
    		config.nat_enabled = false;
    		config
    	}
    }

    /// Protocol handler level packet id
    pub type PacketId = u8;
    /// Protocol / handler id
    pub type ProtocolId = [u8; 3];

    /// Messages used to communitate with the event loop from other threads.
    #[derive(Clone)]
    pub enum NetworkIoMessage {
    	/// Register a new protocol handler.
    	AddHandler {
    		/// Handler shared instance.
    		handler: Arc<NetworkProtocolHandler + Sync>,
    		/// Protocol Id.
    		protocol: ProtocolId,
    		/// Supported protocol versions.
    		versions: Vec<u8>,
    		/// Number of packet IDs reserved by the protocol.
    		packet_count: u8,
    	},
    	/// Register a new protocol timer
    	AddTimer {
    		/// Protocol Id.
    		protocol: ProtocolId,
    		/// Timer token.
    		token: TimerToken,
    		/// Timer delay in milliseconds.
    		delay: u64,
    	},
    	/// Initliaze public interface.
    	InitPublicInterface,
    	/// Disconnect a peer.
    	Disconnect(PeerId),
    	/// Disconnect and temporary disable peer.
    	DisablePeer(PeerId),
    	/// Network has been started with the host as the given enode.
    	NetworkStarted(String),
    }

    /// Local (temporary) peer session ID.
    pub type PeerId = usize;

    #[derive(Debug, PartialEq, Eq)]
    /// Protocol info
    pub struct CapabilityInfo {
    	pub protocol: ProtocolId,
    	pub version: u8,
    	/// Total number of packet IDs this protocol support.
    	pub packet_count: u8,
    }

    impl Encodable for CapabilityInfo {
    	fn rlp_append(&self, s: &mut RlpStream) {
    		s.begin_list(2);
    		s.append(&&self.protocol[..]);
    		s.append(&self.version);
    	}
    }

    /// IO access point. This is passed to all IO handlers and provides an interface to the IO subsystem.
    pub struct NetworkContext<'s> {
    	io: &'s IoContext<NetworkIoMessage>,
    	protocol: ProtocolId,
    	sessions: Arc<RwLock<Slab<SharedSession>>>,
    	session: Option<SharedSession>,
    	session_id: Option<StreamToken>,
    	_reserved_peers: &'s HashSet<NodeId>,
    }

    impl<'s> NetworkContext<'s> {
    	/// Create a new network IO access point. Takes references to all the data that can be updated within the IO handler.
    	fn new(io: &'s IoContext<NetworkIoMessage>,
    		protocol: ProtocolId,
    		session: Option<SharedSession>, sessions: Arc<RwLock<Slab<SharedSession>>>,
    		reserved_peers: &'s HashSet<NodeId>) -> NetworkContext<'s> {
    		let id = session.as_ref().map(|s| s.lock().token());
    		NetworkContext {
    			io: io,
    			protocol: protocol,
    			session_id: id,
    			session: session,
    			sessions: sessions,
    			_reserved_peers: reserved_peers,
    		}
    	}

    	fn resolve_session(&self, peer: PeerId) -> Option<SharedSession> {
    		match self.session_id {
    			Some(id) if id == peer => self.session.clone(),
    			_ => self.sessions.read().get(peer).cloned(),
    		}
    	}

    	/// Send a packet over the network to another peer.
    	pub fn send(&self, peer: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError> {
    		self.send_protocol(self.protocol, peer, packet_id, data)
    	}

    	/// Send a packet over the network to another peer using specified protocol.
    	pub fn send_protocol(&self, protocol: ProtocolId, peer: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError> {
    		let session = self.resolve_session(peer);
    		if let Some(session) = session {
    			session.lock().send_packet(self.io, protocol, packet_id as u8, &data)?;
    		} else  {
    			trace!(target: "network", "Send: Peer no longer exist")
    		}
    		Ok(())
    	}

    	/// Respond to a current network message. Panics if no there is no packet in the context. If the session is expired returns nothing.
    	pub fn respond(&self, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError> {
    		assert!(self.session.is_some(), "Respond called without network context");
    		self.session_id.map_or_else(|| Err(NetworkError::Expired), |id| self.send(id, packet_id, data))
    	}

    	/// Get an IoChannel.
    	pub fn io_channel(&self) -> IoChannel<NetworkIoMessage> {
    		self.io.channel()
    	}

    	/// Disconnect a peer and prevent it from connecting again.
    	pub fn disable_peer(&self, peer: PeerId) {
    		self.io.message(NetworkIoMessage::DisablePeer(peer))
    			.unwrap_or_else(|e| warn!("Error sending network IO message: {:?}", e));
    	}

    	/// Disconnect peer. Reconnect can be attempted later.
    	pub fn disconnect_peer(&self, peer: PeerId) {
    		self.io.message(NetworkIoMessage::Disconnect(peer))
    			.unwrap_or_else(|e| warn!("Error sending network IO message: {:?}", e));
    	}

    	/// Check if the session is still active.
    	pub fn is_expired(&self) -> bool {
    		self.session.as_ref().map_or(false, |s| s.lock().expired())
    	}

    	/// Register a new IO timer. 'IoHandler::timeout' will be called with the token.
    	pub fn register_timer(&self, token: TimerToken, ms: u64) -> Result<(), NetworkError> {
    		self.io.message(NetworkIoMessage::AddTimer {
    			token: token,
    			delay: ms,
    			protocol: self.protocol,
    		}).unwrap_or_else(|e| warn!("Error sending network IO message: {:?}", e));
    		Ok(())
    	}

    	/// Returns peer identification string
    	pub fn peer_client_version(&self, peer: PeerId) -> String {
    		self.resolve_session(peer).map_or("unknown".to_owned(), |s| s.lock().info.client_version.clone())
    	}

    	/// Returns information on p2p session
    	pub fn session_info(&self, peer: PeerId) -> Option<SessionInfo> {
    		self.resolve_session(peer).map(|s| s.lock().info.clone())
    	}

    	/// Returns max version for a given protocol.
    	pub fn protocol_version(&self, protocol: ProtocolId, peer: PeerId) -> Option<u8> {
    		let session = self.resolve_session(peer);
    		session.and_then(|s| s.lock().capability_version(protocol))
    	}

    	/// Returns this object's subprotocol name.
    	pub fn subprotocol_name(&self) -> ProtocolId { self.protocol }
    }

    /// Shared host information
    pub struct HostInfo {
    	/// Our private and public keys.
    	keys: KeyPair,
    	/// Current network configuration
    	config: NetworkConfiguration,
    	/// Connection nonce.
    	nonce: H256,
    	/// RLPx protocol version
    	pub protocol_version: u32,
    	/// Client identifier
    	pub client_version: String,
    	/// Registered capabilities (handlers)
    	pub capabilities: Vec<CapabilityInfo>,
    	/// Local address + discovery port
    	pub local_endpoint: NodeEndpoint,
    	/// Public address + discovery port
    	pub public_endpoint: Option<NodeEndpoint>,
    }

    impl HostInfo {
    	/// Returns public key
    	pub fn id(&self) -> &NodeId {
    		self.keys.public()
    	}

    	/// Returns secret key
    	pub fn secret(&self) -> &Secret {
    		self.keys.secret()
    	}

    	/// Increments and returns connection nonce.
    	pub fn next_nonce(&mut self) -> H256 {
    		self.nonce = self.nonce.sha3();
    		self.nonce.clone()
    	}
    }

    type SharedSession = Arc<Mutex<Session>>;

    #[derive(Copy, Clone)]
    struct ProtocolTimer {
    	pub protocol: ProtocolId,
    	pub token: TimerToken, // Handler level token
    }

    /// Root IO handler. Manages protocol handlers, IO timers and network connections.
    pub struct Host {
    	pub info: RwLock<HostInfo>,
    	tcp_listener: Mutex<TcpListener>,
    	sessions: Arc<RwLock<Slab<SharedSession>>>,
    	discovery: Mutex<Option<Discovery>>,
    	nodes: RwLock<NodeTable>,
    	handlers: RwLock<HashMap<ProtocolId, Arc<NetworkProtocolHandler>>>,
    	timers: RwLock<HashMap<TimerToken, ProtocolTimer>>,
    	timer_counter: RwLock<usize>,
    	stats: Arc<NetworkStats>,
    	reserved_nodes: RwLock<HashSet<NodeId>>,
    	num_sessions: AtomicUsize,
    	stopping: AtomicBool,
    }

    impl Host {
    	/// Create a new instance
    	pub fn new(mut config: NetworkConfiguration, stats: Arc<NetworkStats>) -> Result<Host, NetworkError> {
    		let mut listen_address = match config.listen_address {
    			None => SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), DEFAULT_PORT)),
    			Some(addr) => addr,
    		};

    		let keys = if let Some(ref secret) = config.use_secret {
    			KeyPair::from_secret(secret.clone())?
    		} else {
    			config.config_path.clone().and_then(|ref p| load_key(Path::new(&p)))
    				.map_or_else(|| {
    				let key = Random.generate().expect("Error generating random key pair");
    				if let Some(path) = config.config_path.clone() {
    					save_key(Path::new(&path), key.secret());
    				}
    				key
    			},
    			|s| KeyPair::from_secret(s).expect("Error creating node secret key"))
    		};
    		let path = config.net_config_path.clone();
    		// Setup the server socket
    		let tcp_listener = TcpListener::bind(&listen_address)?;
    		listen_address = SocketAddr::new(listen_address.ip(), tcp_listener.local_addr()?.port());
    		debug!(target: "network", "Listening at {:?}", listen_address);
    		let udp_port = config.udp_port.unwrap_or(listen_address.port());
    		let local_endpoint = NodeEndpoint { address: listen_address, udp_port: udp_port };

    		let boot_nodes = config.boot_nodes.clone();
    		let reserved_nodes = config.reserved_nodes.clone();
    		config.max_handshakes = min(config.max_handshakes, MAX_HANDSHAKES as u32);

    		let mut host = Host {
    			info: RwLock::new(HostInfo {
    				keys: keys,
    				config: config,
    				nonce: H256::random(),
    				protocol_version: PROTOCOL_VERSION,
    				client_version: version(),
    				capabilities: Vec::new(),
    				public_endpoint: None,
    				local_endpoint: local_endpoint,
    			}),
    			discovery: Mutex::new(None),
    			tcp_listener: Mutex::new(tcp_listener),
    			sessions: Arc::new(RwLock::new(Slab::new_starting_at(FIRST_SESSION, MAX_SESSIONS))),
    			nodes: RwLock::new(NodeTable::new(path)),
    			handlers: RwLock::new(HashMap::new()),
    			timers: RwLock::new(HashMap::new()),
    			timer_counter: RwLock::new(USER_TIMER),
    			stats: stats,
    			reserved_nodes: RwLock::new(HashSet::new()),
    			num_sessions: AtomicUsize::new(0),
    			stopping: AtomicBool::new(false),
    		};

    		for n in boot_nodes {
    			host.add_node(&n);
    		}

    		for n in reserved_nodes {
    			if let Err(e) = host.add_reserved_node(&n) {
    				debug!(target: "network", "Error parsing node id: {}: {:?}", n, e);
    			}
    		}
    		Ok(host)
    	}

    	pub fn add_node(&mut self, id: &str) {
    		match Node::from_str(id) {
    			Err(e) => { debug!(target: "network", "Could not add node {}: {:?}", id, e); },
    			Ok(n) => {
    				let entry = NodeEntry { endpoint: n.endpoint.clone(), id: n.id.clone() };

    				self.nodes.write().add_node(n);
    				if let Some(ref mut discovery) = *self.discovery.lock() {
    					discovery.add_node(entry);
    				}
    			}
    		}
    	}

    	pub fn add_reserved_node(&self, id: &str) -> Result<(), NetworkError> {
    		let n = Node::from_str(id)?;

    		let entry = NodeEntry { endpoint: n.endpoint.clone(), id: n.id.clone() };
    		self.reserved_nodes.write().insert(n.id.clone());
    		self.nodes.write().add_node(Node::new(entry.id.clone(), entry.endpoint.clone()));

    		if let Some(ref mut discovery) = *self.discovery.lock() {
    			discovery.add_node(entry);
    		}

    		Ok(())
    	}

    	pub fn set_non_reserved_mode(&self, mode: NonReservedPeerMode, io: &IoContext<NetworkIoMessage>) {
    		let mut info = self.info.write();

    		if info.config.non_reserved_mode != mode {
    			info.config.non_reserved_mode = mode.clone();
    			drop(info);
    			if let NonReservedPeerMode::Deny = mode {
    				// disconnect all non-reserved peers here.
    				let reserved: HashSet<NodeId> = self.reserved_nodes.read().clone();
    				let mut to_kill = Vec::new();
    				for e in self.sessions.write().iter_mut() {
    					let mut s = e.lock();
    					{
    						let id = s.id();
    						if id.map_or(false, |id| reserved.contains(id)) {
    							continue;
    						}
    					}

    					s.disconnect(io, DisconnectReason::ClientQuit);
    					to_kill.push(s.token());
    				}
    				for p in to_kill {
    					trace!(target: "network", "Disconnecting on reserved-only mode: {}", p);
    					self.kill_connection(p, io, false);
    				}
    			}
    		}
    	}

    	pub fn remove_reserved_node(&self, id: &str) -> Result<(), NetworkError> {
    		let n = Node::from_str(id)?;
    		self.reserved_nodes.write().remove(&n.id);

    		Ok(())
    	}

    	pub fn client_version() -> String {
    		version()
    	}

    	pub fn external_url(&self) -> Option<String> {
    		let info = self.info.read();
    		info.public_endpoint.as_ref().map(|e| format!("{}", Node::new(info.id().clone(), e.clone())))
    	}

    	pub fn local_url(&self) -> String {
    		let info = self.info.read();
    		format!("{}", Node::new(info.id().clone(), info.local_endpoint.clone()))
    	}

    	pub fn stop(&self, io: &IoContext<NetworkIoMessage>) -> Result<(), NetworkError> {
    		self.stopping.store(true, AtomicOrdering::Release);
    		let mut to_kill = Vec::new();
    		for e in self.sessions.write().iter_mut() {
    			let mut s = e.lock();
    			s.disconnect(io, DisconnectReason::ClientQuit);
    			to_kill.push(s.token());
    		}
    		for p in to_kill {
    			trace!(target: "network", "Disconnecting on shutdown: {}", p);
    			self.kill_connection(p, io, true);
    		}
    		io.unregister_handler()?;
    		Ok(())
    	}

    	/// Get all connected peers.
    	pub fn connected_peers(&self) -> Vec<PeerId> {
    		let sessions = self.sessions.read();
    		let sessions = &*sessions;

    		let mut peers = Vec::with_capacity(sessions.count());
    		for i in (0..MAX_SESSIONS).map(|x| x + FIRST_SESSION) {
    			if sessions.get(i).is_some() {
    				peers.push(i);
    			}
    		}
    		peers
    	}

    	fn init_public_interface(&self, io: &IoContext<NetworkIoMessage>) -> Result<(), NetworkError> {
    		if self.info.read().public_endpoint.is_some() {
    			return Ok(());
    		}
    		let local_endpoint = self.info.read().local_endpoint.clone();
    		let public_address = self.info.read().config.public_address.clone();
    		let allow_ips = self.info.read().config.allow_ips;
    		let public_endpoint = match public_address {
    			None => {
    				let public_address = select_public_address(local_endpoint.address.port());
    				let public_endpoint = NodeEndpoint { address: public_address, udp_port: local_endpoint.udp_port };
    				if self.info.read().config.nat_enabled {
    					match map_external_address(&local_endpoint) {
    						Some(endpoint) => {
    							info!("NAT mapped to external address {}", endpoint.address);
    							endpoint
    						},
    						None => public_endpoint
    					}
    				} else {
    					public_endpoint
    				}
    			}
    			Some(addr) => NodeEndpoint { address: addr, udp_port: local_endpoint.udp_port }
    		};

    		self.info.write().public_endpoint = Some(public_endpoint.clone());

    		if let Some(url) = self.external_url() {
    			io.message(NetworkIoMessage::NetworkStarted(url)).unwrap_or_else(|e| warn!("Error sending IO notification: {:?}", e));
    		}

    		// Initialize discovery.
    		let discovery = {
    			let info = self.info.read();
    			if info.config.discovery_enabled && info.config.non_reserved_mode == NonReservedPeerMode::Accept {
    				let mut udp_addr = local_endpoint.address.clone();
    				udp_addr.set_port(local_endpoint.udp_port);
    				Some(Discovery::new(&info.keys, udp_addr, public_endpoint, DISCOVERY, allow_ips))
    			} else { None }
    		};

    		if let Some(mut discovery) = discovery {
    			discovery.init_node_list(self.nodes.read().unordered_entries());
    			discovery.add_node_list(self.nodes.read().unordered_entries());
    			*self.discovery.lock() = Some(discovery);
    			io.register_stream(DISCOVERY)?;
    			io.register_timer(DISCOVERY_REFRESH, DISCOVERY_REFRESH_TIMEOUT)?;
    			io.register_timer(DISCOVERY_ROUND, DISCOVERY_ROUND_TIMEOUT)?;
    		}
    		io.register_timer(NODE_TABLE, NODE_TABLE_TIMEOUT)?;
    		io.register_stream(TCP_ACCEPT)?;
    		Ok(())
    	}

    	fn maintain_network(&self, io: &IoContext<NetworkIoMessage>) {
    		self.keep_alive(io);
    		self.connect_peers(io);
    	}

    	fn have_session(&self, id: &NodeId) -> bool {
    		self.sessions.read().iter().any(|e| e.lock().info.id == Some(id.clone()))
    	}

    	fn session_count(&self) -> usize {
    		self.num_sessions.load(AtomicOrdering::Relaxed)
    	}

    	fn connecting_to(&self, id: &NodeId) -> bool {
    		self.sessions.read().iter().any(|e| e.lock().id() == Some(id))
    	}

    	fn handshake_count(&self) -> usize {
    		// session_count < total_count is possible because of the data race.
    		self.sessions.read().count().saturating_sub(self.session_count())
    	}

    	fn keep_alive(&self, io: &IoContext<NetworkIoMessage>) {
    		let mut to_kill = Vec::new();
    		for e in self.sessions.write().iter_mut() {
    			let mut s = e.lock();
    			if !s.keep_alive(io) {
    				s.disconnect(io, DisconnectReason::PingTimeout);
    				to_kill.push(s.token());
    			}
    		}
    		for p in to_kill {
    			trace!(target: "network", "Ping timeout: {}", p);
    			self.kill_connection(p, io, true);
    		}
    	}

    	fn connect_peers(&self, io: &IoContext<NetworkIoMessage>) {
    		let (min_peers, mut pin, max_handshakes, allow_ips, self_id) = {
    			let info = self.info.read();
    			if info.capabilities.is_empty() {
    				return;
    			}
    			let config = &info.config;

    			(config.min_peers, config.non_reserved_mode == NonReservedPeerMode::Deny, config.max_handshakes as usize, config.allow_ips, info.id().clone())
    		};

    		let session_count = self.session_count();
    		let reserved_nodes = self.reserved_nodes.read();
    		if session_count >= min_peers as usize + reserved_nodes.len() {
    			// check if all pinned nodes are connected.
    			if reserved_nodes.iter().all(|n| self.have_session(n) && self.connecting_to(n)) {
    				return;
    			}

    			// if not, only attempt connect to reserved peers
    			pin = true;
    		}

    		let handshake_count = self.handshake_count();
    		// allow 16 slots for incoming connections
    		if handshake_count >= max_handshakes {
    			return;
    		}

    		// iterate over all nodes, reserved ones coming first.
    		// if we are pinned to only reserved nodes, ignore all others.
    		let nodes = reserved_nodes.iter().cloned().chain(if !pin {
    			self.nodes.read().nodes(allow_ips)
    		} else {
    			Vec::new()
    		});

    		let max_handshakes_per_round = max_handshakes / 2;
    		let mut started: usize = 0;
    		for id in nodes.filter(|id| !self.have_session(id) && !self.connecting_to(id) && *id != self_id)
    			.take(min(max_handshakes_per_round, max_handshakes - handshake_count)) {
    			self.connect_peer(&id, io);
    			started += 1;
    		}
    		debug!(target: "network", "Connecting peers: {} sessions, {} pending, {} started", self.session_count(), self.handshake_count(), started);
    	}

    	#[cfg_attr(feature="dev", allow(single_match))]
    	fn connect_peer(&self, id: &NodeId, io: &IoContext<NetworkIoMessage>) {
    		if self.have_session(id) {
    			trace!(target: "network", "Aborted connect. Node already connected.");
    			return;
    		}
    		if self.connecting_to(id) {
    			trace!(target: "network", "Aborted connect. Node already connecting.");
    			return;
    		}

    		let socket = {
    			let address = {
    				let mut nodes = self.nodes.write();
    				if let Some(node) = nodes.get_mut(id) {
    					node.last_attempted = Some(::time::now());
    					node.endpoint.address
    				}
    				else {
    					debug!(target: "network", "Connection to expired node aborted");
    					return;
    				}
    			};
    			match TcpStream::connect(&address) {
    				Ok(socket) => {
    					trace!(target: "network", "Connecting to {:?}", address);
    					socket
    				},
    				Err(e) => {
    					debug!(target: "network", "Can't connect to address {:?}: {:?}", address, e);
    					return;
    				}
    			}
    		};
    		if let Err(e) = self.create_connection(socket, Some(id), io) {
    			debug!(target: "network", "Can't create connection: {:?}", e);
    		}
    	}

    	#[cfg_attr(feature="dev", allow(block_in_if_condition_stmt))]
    	fn create_connection(&self, socket: TcpStream, id: Option<&NodeId>, io: &IoContext<NetworkIoMessage>) -> Result<(), NetworkError> {
    		let nonce = self.info.write().next_nonce();
    		let mut sessions = self.sessions.write();

    		let token = sessions.insert_with_opt(|token| {
    			match Session::new(io, socket, token, id, &nonce, self.stats.clone(), &self.info.read()) {
    				Ok(s) => Some(Arc::new(Mutex::new(s))),
    				Err(e) => {
    					debug!(target: "network", "Session create error: {:?}", e);
    					None
    				}
    			}
    		});

    		match token {
    			Some(t) => io.register_stream(t).map(|_| ()).map_err(Into::into),
    			None => {
    				debug!(target: "network", "Max sessions reached");
    				Ok(())
    			}
    		}
    	}

    	fn accept(&self, io: &IoContext<NetworkIoMessage>) {
    		trace!(target: "network", "Accepting incoming connection");
    		loop {
    			let socket = match self.tcp_listener.lock().accept() {
    				Ok((sock, _addr)) => sock,
    				Err(e) => {
    					if e.kind() != ErrorKind::WouldBlock {
    						debug!(target: "network", "Error accepting connection: {:?}", e);
    					}
    					break
    				},
    			};
    			if let Err(e) = self.create_connection(socket, None, io) {
    				debug!(target: "network", "Can't accept connection: {:?}", e);
    			}
    		}
    	}

    	fn session_writable(&self, token: StreamToken, io: &IoContext<NetworkIoMessage>) {
    		let session = { self.sessions.read().get(token).cloned() };

    		if let Some(session) = session {
    			let mut s = session.lock();
    			if let Err(e) = s.writable(io, &self.info.read()) {
    				trace!(target: "network", "Session write error: {}: {:?}", token, e);
    			}
    			if s.done() {
    				io.deregister_stream(token).unwrap_or_else(|e| debug!("Error deregistering stream: {:?}", e));
    			}
    		}
    	}

    	fn connection_closed(&self, token: TimerToken, io: &IoContext<NetworkIoMessage>) {
    		trace!(target: "network", "Connection closed: {}", token);
    		self.kill_connection(token, io, true);
    	}

    	#[cfg_attr(feature="dev", allow(collapsible_if))]
    	fn session_readable(&self, token: StreamToken, io: &IoContext<NetworkIoMessage>) {
    		let mut ready_data: Vec<ProtocolId> = Vec::new();
    		let mut packet_data: Vec<(ProtocolId, PacketId, Vec<u8>)> = Vec::new();
    		let mut kill = false;
    		let session = { self.sessions.read().get(token).cloned() };
    		let mut ready_id = None;
    		if let Some(session) = session.clone() {
    			{
    				let mut s = session.lock();
    				loop {
    					let session_result = s.readable(io, &self.info.read());
    					match session_result {
    						Err(e) => {
    							trace!(target: "network", "Session read error: {}:{:?} ({:?}) {:?}", token, s.id(), s.remote_addr(), e);
    							if let NetworkError::Disconnect(DisconnectReason::IncompatibleProtocol) = e {
    								if let Some(id) = s.id() {
    									if !self.reserved_nodes.read().contains(id) {
    										self.nodes.write().mark_as_useless(id);
    									}
    								}
    							}
    							kill = true;
    							break;
    						},
    						Ok(SessionData::Ready) => {
    							self.num_sessions.fetch_add(1, AtomicOrdering::SeqCst);
    							let session_count = self.session_count();
    							let (min_peers, max_peers, reserved_only) = {
    								let info = self.info.read();
    								let mut max_peers = info.config.max_peers;
    								for cap in s.info.capabilities.iter() {
    									if let Some(num) = info.config.reserved_protocols.get(&cap.protocol) {
    										max_peers += *num;
    										break;
    									}
    								}
    								(info.config.min_peers as usize, max_peers as usize, info.config.non_reserved_mode == NonReservedPeerMode::Deny)
    							};

    							let id = s.id().expect("Ready session always has id").clone();

    							// Check for the session limit. session_counts accounts for the new session.
    							if reserved_only ||
    								(s.info.originated && session_count > min_peers) ||
    								(!s.info.originated && session_count > max_peers) {
    								// only proceed if the connecting peer is reserved.
    								if !self.reserved_nodes.read().contains(&id) {
    									s.disconnect(io, DisconnectReason::TooManyPeers);
    									return;
    								}
    							}
    							ready_id = Some(id);

    							// Add it to the node table
    							if !s.info.originated {
    								if let Ok(address) = s.remote_addr() {
    									let entry = NodeEntry { id: id, endpoint: NodeEndpoint { address: address, udp_port: address.port() } };
    									self.nodes.write().add_node(Node::new(entry.id.clone(), entry.endpoint.clone()));
    									let mut discovery = self.discovery.lock();
    									if let Some(ref mut discovery) = *discovery {
    										discovery.add_node(entry);
    									}
    								}
    							}
    							for (p, _) in self.handlers.read().iter() {
    								if s.have_capability(*p) {
    									ready_data.push(*p);
    								}
    							}
    						},
    						Ok(SessionData::Packet {
    							data,
    							protocol,
    							packet_id,
    						}) => {
    							match self.handlers.read().get(&protocol) {
    								None => { warn!(target: "network", "No handler found for protocol: {:?}", protocol) },
    								Some(_) => packet_data.push((protocol, packet_id, data)),
    							}
    						},
    						Ok(SessionData::Continue) => (),
    						Ok(SessionData::None) => break,
    					}
    				}
    			}

    			if kill {
    				self.kill_connection(token, io, true);
    			}

    			let handlers = self.handlers.read();
    			if !ready_data.is_empty() {
    				let duplicate = self.sessions.read().iter().any(|e| {
    					let session = e.lock();
    					session.token() != token && session.info.id == ready_id
    				});
    				if duplicate {
    					trace!(target: "network", "Rejected duplicate connection: {}", token);
    					session.lock().disconnect(io, DisconnectReason::DuplicatePeer);
    					return;
    				}
    				for p in ready_data {
    					self.stats.inc_sessions();
    					let reserved = self.reserved_nodes.read();
    					if let Some(h) = handlers.get(&p).clone() {
    						h.connected(&NetworkContext::new(io, p, Some(session.clone()), self.sessions.clone(), &reserved), &token);
    						// accumulate pending packets.
    						let mut session = session.lock();
    						packet_data.extend(session.mark_connected(p));
    					}
    				}
    			}

    			for (p, packet_id, data) in packet_data {
    				let reserved = self.reserved_nodes.read();
    				if let Some(h) = handlers.get(&p).clone() {
    					h.read(&NetworkContext::new(io, p, Some(session.clone()), self.sessions.clone(), &reserved), &token, packet_id, &data[1..]);
    				}
    			}
    		}
    	}

    	fn connection_timeout(&self, token: StreamToken, io: &IoContext<NetworkIoMessage>) {
    		trace!(target: "network", "Connection timeout: {}", token);
    		self.kill_connection(token, io, true)
    	}

    	fn kill_connection(&self, token: StreamToken, io: &IoContext<NetworkIoMessage>, remote: bool) {
    		let mut to_disconnect: Vec<ProtocolId> = Vec::new();
    		let mut failure_id = None;
    		let mut deregister = false;
    		let mut expired_session = None;
    		if let FIRST_SESSION ... LAST_SESSION = token {
    			let sessions = self.sessions.write();
    			if let Some(session) = sessions.get(token).cloned() {
    				expired_session = Some(session.clone());
    				let mut s = session.lock();
    				if !s.expired() {
    					if s.is_ready() {
    						self.num_sessions.fetch_sub(1, AtomicOrdering::SeqCst);
    						for (p, _) in self.handlers.read().iter() {
    							if s.have_capability(*p)  {
    								to_disconnect.push(*p);
    							}
    						}
    					}
    					s.set_expired();
    					failure_id = s.id().cloned();
    				}
    				deregister = remote || s.done();
    			}
    		}
    		if let Some(id) = failure_id {
    			if remote {
    				self.nodes.write().note_failure(&id);
    			}
    		}
    		for p in to_disconnect {
    			let reserved = self.reserved_nodes.read();
    			if let Some(h) = self.handlers.read().get(&p).clone() {
    				h.disconnected(&NetworkContext::new(io, p, expired_session.clone(), self.sessions.clone(), &reserved), &token);
    			}
    		}
    		if deregister {
    			io.deregister_stream(token).unwrap_or_else(|e| debug!("Error deregistering stream: {:?}", e));
    		}
    	}

    	fn update_nodes(&self, _io: &IoContext<NetworkIoMessage>, node_changes: TableUpdates) {
    		let mut to_remove: Vec<PeerId> = Vec::new();
    		{
    			let sessions = self.sessions.write();
    			for c in sessions.iter() {
    				let s = c.lock();
    				if let Some(id) = s.id() {
    					if node_changes.removed.contains(id) {
    						to_remove.push(s.token());
    					}
    				}
    			}
    		}
    		for i in to_remove {
    			trace!(target: "network", "Removed from node table: {}", i);
    		}
    		self.nodes.write().update(node_changes, &*self.reserved_nodes.read());
    	}

    	pub fn with_context<F>(&self, protocol: ProtocolId, io: &IoContext<NetworkIoMessage>, action: F) where F: Fn(&NetworkContext) {
    		let reserved = { self.reserved_nodes.read() };

    		let context = NetworkContext::new(io, protocol, None, self.sessions.clone(), &reserved);
    		action(&context);
    	}

    	pub fn with_context_eval<F, T>(&self, protocol: ProtocolId, io: &IoContext<NetworkIoMessage>, action: F) -> T where F: Fn(&NetworkContext) -> T {
    		let reserved = { self.reserved_nodes.read() };

    		let context = NetworkContext::new(io, protocol, None, self.sessions.clone(), &reserved);
    		action(&context)
    	}
    }

    impl IoHandler<NetworkIoMessage> for Host {
    	/// Initialize networking
    	fn initialize(&self, io: &IoContext<NetworkIoMessage>) {
    		io.register_timer(IDLE, MAINTENANCE_TIMEOUT).expect("Error registering Network idle timer");
    		io.message(NetworkIoMessage::InitPublicInterface).unwrap_or_else(|e| warn!("Error sending IO notification: {:?}", e));
    		self.maintain_network(io)
    	}

    	fn stream_hup(&self, io: &IoContext<NetworkIoMessage>, stream: StreamToken) {
    		trace!(target: "network", "Hup: {}", stream);
    		match stream {
    			FIRST_SESSION ... LAST_SESSION => self.connection_closed(stream, io),
    			_ => warn!(target: "network", "Unexpected hup"),
    		};
    	}

    	fn stream_readable(&self, io: &IoContext<NetworkIoMessage>, stream: StreamToken) {
    		if self.stopping.load(AtomicOrdering::Acquire) {
    			return;
    		}
    		match stream {
    			FIRST_SESSION ... LAST_SESSION => self.session_readable(stream, io),
    			DISCOVERY => {
    				let node_changes = { self.discovery.lock().as_mut().map_or(None, |d| d.readable(io)) };
    				if let Some(node_changes) = node_changes {
    					self.update_nodes(io, node_changes);
    				}
    			},
    			TCP_ACCEPT => self.accept(io),
    			_ => panic!("Received unknown readable token"),
    		}
    	}

    	fn stream_writable(&self, io: &IoContext<NetworkIoMessage>, stream: StreamToken) {
    		if self.stopping.load(AtomicOrdering::Acquire) {
    			return;
    		}
    		match stream {
    			FIRST_SESSION ... LAST_SESSION => self.session_writable(stream, io),
    			DISCOVERY => {
    				self.discovery.lock().as_mut().map(|d| d.writable(io));
    			}
    			_ => panic!("Received unknown writable token"),
    		}
    	}

    	fn timeout(&self, io: &IoContext<NetworkIoMessage>, token: TimerToken) {
    		if self.stopping.load(AtomicOrdering::Acquire) {
    			return;
    		}
    		match token {
    			IDLE => self.maintain_network(io),
    			FIRST_SESSION ... LAST_SESSION => self.connection_timeout(token, io),
    			DISCOVERY_REFRESH => {
    				self.discovery.lock().as_mut().map(|d| d.refresh());
    				io.update_registration(DISCOVERY).unwrap_or_else(|e| debug!("Error updating discovery registration: {:?}", e));
    			},
    			DISCOVERY_ROUND => {
    				let node_changes = { self.discovery.lock().as_mut().map_or(None, |d| d.round()) };
    				if let Some(node_changes) = node_changes {
    					self.update_nodes(io, node_changes);
    				}
    				io.update_registration(DISCOVERY).unwrap_or_else(|e| debug!("Error updating discovery registration: {:?}", e));
    			},
    			NODE_TABLE => {
    				trace!(target: "network", "Refreshing node table");
    				self.nodes.write().clear_useless();
    				self.nodes.write().save();
    			},
    			_ => match self.timers.read().get(&token).cloned() {
    				Some(timer) => match self.handlers.read().get(&timer.protocol).cloned() {
    					None => { warn!(target: "network", "No handler found for protocol: {:?}", timer.protocol) },
    					Some(h) => {
    						let reserved = self.reserved_nodes.read();
    						h.timeout(&NetworkContext::new(io, timer.protocol, None, self.sessions.clone(), &reserved), timer.token);
    					}
    				},
    				None => { warn!("Unknown timer token: {}", token); } // timer is not registerd through us
    			}
    		}
    	}

    	fn message(&self, io: &IoContext<NetworkIoMessage>, message: &NetworkIoMessage) {
    		if self.stopping.load(AtomicOrdering::Acquire) {
    			return;
    		}
    		match *message {
    			NetworkIoMessage::AddHandler {
    				ref handler,
    				ref protocol,
    				ref versions,
    				ref packet_count,
    			} => {
    				let h = handler.clone();
    				let reserved = self.reserved_nodes.read();
    				h.initialize(&NetworkContext::new(io, *protocol, None, self.sessions.clone(), &reserved));
    				self.handlers.write().insert(*protocol, h);
    				let mut info = self.info.write();
    				for v in versions {
    					info.capabilities.push(CapabilityInfo { protocol: *protocol, version: *v, packet_count: *packet_count });
    				}
    			},
    			NetworkIoMessage::AddTimer {
    				ref protocol,
    				ref delay,
    				ref token,
    			} => {
    				let handler_token = {
    					let mut timer_counter = self.timer_counter.write();
    					let counter = &mut *timer_counter;
    					let handler_token = *counter;
    					*counter += 1;
    					handler_token
    				};
    				self.timers.write().insert(handler_token, ProtocolTimer { protocol: *protocol, token: *token });
    				io.register_timer(handler_token, *delay).unwrap_or_else(|e| debug!("Error registering timer {}: {:?}", token, e));
    			},
    			NetworkIoMessage::Disconnect(ref peer) => {
    				let session = { self.sessions.read().get(*peer).cloned() };
    				if let Some(session) = session {
    					session.lock().disconnect(io, DisconnectReason::DisconnectRequested);
    				}
    				trace!(target: "network", "Disconnect requested {}", peer);
    				self.kill_connection(*peer, io, false);
    			},
    			NetworkIoMessage::DisablePeer(ref peer) => {
    				let session = { self.sessions.read().get(*peer).cloned() };
    				if let Some(session) = session {
    					session.lock().disconnect(io, DisconnectReason::DisconnectRequested);
    					if let Some(id) = session.lock().id() {
    						self.nodes.write().mark_as_useless(id)
    					}
    				}
    				trace!(target: "network", "Disabling peer {}", peer);
    				self.kill_connection(*peer, io, false);
    			},
    			NetworkIoMessage::InitPublicInterface =>
    				self.init_public_interface(io).unwrap_or_else(|e| warn!("Error initializing public interface: {:?}", e)),
    			_ => {}	// ignore others.
    		}
    	}

    	fn register_stream(&self, stream: StreamToken, reg: Token, event_loop: &mut EventLoop<IoManager<NetworkIoMessage>>) {
    		match stream {
    			FIRST_SESSION ... LAST_SESSION => {
    				let session = { self.sessions.read().get(stream).cloned() };
    				if let Some(session) = session {
    					session.lock().register_socket(reg, event_loop).expect("Error registering socket");
    				}
    			}
    			DISCOVERY => self.discovery.lock().as_ref().and_then(|d| d.register_socket(event_loop).ok()).expect("Error registering discovery socket"),
    			TCP_ACCEPT => event_loop.register(&*self.tcp_listener.lock(), Token(TCP_ACCEPT), Ready::all(), PollOpt::edge()).expect("Error registering stream"),
    			_ => warn!("Unexpected stream registration")
    		}
    	}

    	fn deregister_stream(&self, stream: StreamToken, event_loop: &mut EventLoop<IoManager<NetworkIoMessage>>) {
    		match stream {
    			FIRST_SESSION ... LAST_SESSION => {
    				let mut connections = self.sessions.write();
    				if let Some(connection) = connections.get(stream).cloned() {
    					connection.lock().deregister_socket(event_loop).expect("Error deregistering socket");
    					connections.remove(stream);
    				}
    			}
    			DISCOVERY => (),
    			_ => warn!("Unexpected stream deregistration")
    		}
    	}

    	fn update_stream(&self, stream: StreamToken, reg: Token, event_loop: &mut EventLoop<IoManager<NetworkIoMessage>>) {
    		match stream {
    			FIRST_SESSION ... LAST_SESSION => {
    				let connection = { self.sessions.read().get(stream).cloned() };
    				if let Some(connection) = connection {
    					connection.lock().update_socket(reg, event_loop).expect("Error updating socket");
    				}
    			}
    			DISCOVERY => self.discovery.lock().as_ref().and_then(|d| d.update_registration(event_loop).ok()).expect("Error reregistering discovery socket"),
    			TCP_ACCEPT => event_loop.reregister(&*self.tcp_listener.lock(), Token(TCP_ACCEPT), Ready::all(), PollOpt::edge()).expect("Error reregistering stream"),
    			_ => warn!("Unexpected stream update")
    		}
    	}
    }

    fn save_key(path: &Path, key: &Secret) {
    	let mut path_buf = PathBuf::from(path);
    	if let Err(e) = fs::create_dir_all(path_buf.as_path()) {
    		warn!("Error creating key directory: {:?}", e);
    		return;
    	};
    	path_buf.push("key");
    	let path = path_buf.as_path();
    	let mut file = match fs::File::create(&path) {
    		Ok(file) => file,
    		Err(e) => {
    			warn!("Error creating key file: {:?}", e);
    			return;
    		}
    	};
    	if let Err(e) = restrict_permissions_owner(path, true, false) {
    		warn!(target: "network", "Failed to modify permissions of the file ({})", e);
    	}
    	if let Err(e) = file.write(&key.hex().into_bytes()) {
    		warn!("Error writing key file: {:?}", e);
    	}
    }

    fn load_key(path: &Path) -> Option<Secret> {
    	let mut path_buf = PathBuf::from(path);
    	path_buf.push("key");
    	let mut file = match fs::File::open(path_buf.as_path()) {
    		Ok(file) => file,
    		Err(e) => {
    			debug!("Error opening key file: {:?}", e);
    			return None;
    		}
    	};
    	let mut buf = String::new();
    	match file.read_to_string(&mut buf) {
    		Ok(_) => {},
    		Err(e) => {
    			warn!("Error reading key file: {:?}", e);
    			return None;
    		}
    	}
    	match Secret::from_str(&buf) {
    		Ok(key) => Some(key),
    		Err(e) => {
    			warn!("Error parsing key file: {:?}", e);
    			None
    		}
    	}
    }

    #[test]
    fn key_save_load() {
    	use ::devtools::RandomTempPath;
    	let temp_path = RandomTempPath::create_dir();
    	let key = Secret::from_slice(&H256::random()).unwrap();
    	save_key(temp_path.as_path(), &key);
    	let r = load_key(temp_path.as_path());
    	assert_eq!(key, r.unwrap());
    }

    #[test]
    fn host_client_url() {
    	let mut config = NetworkConfiguration::new_local();
    	let key = "6f7b0d801bc7b5ce7bbd930b84fd0369b3eb25d09be58d64ba811091046f3aa2".parse().unwrap();
    	config.use_secret = Some(key);
    	let host: Host = Host::new(config, Arc::new(NetworkStats::new())).unwrap();
    	assert!(host.local_url().starts_with("enode://101b3ef5a4ea7a1c7928e24c4c75fd053c235d7b80c22ae5c03d145d0ac7396e2a4ffff9adee3133a7b05044a5cee08115fd65145e5165d646bde371010d803c@"));
    }

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