path: root/p2p/server.go

package p2p

import (
    "bytes"
    "crypto/ecdsa"
    "errors"
    "fmt"
    "net"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/p2p/discover"
    "github.com/ethereum/go-ethereum/p2p/nat"
    "github.com/ethereum/go-ethereum/rlp"
)

const (
    defaultDialTimeout   = 10 * time.Second
    refreshPeersInterval = 30 * time.Second

    // total timeout for encryption handshake and protocol
    // handshake in both directions.
    handshakeTimeout = 5 * time.Second
    // maximum time allowed for reading a complete message.
    // this is effectively the amount of time a connection can be idle.
    frameReadTimeout = 1 * time.Minute
    // maximum amount of time allowed for writing a complete message.
    frameWriteTimeout = 5 * time.Second
)

var srvlog = logger.NewLogger("P2P Server")
var srvjslog = logger.NewJsonLogger()

// Server manages all peer connections.
//
// The fields of Server are used as configuration parameters.
// You should set them before starting the Server. Fields may not be
// modified while the server is running.
type Server struct {
    // This field must be set to a valid secp256k1 private key.
    PrivateKey *ecdsa.PrivateKey

    // MaxPeers is the maximum number of peers that can be
    // connected. It must be greater than zero.
    MaxPeers int

    // Name sets the node name of this server.
    // Use common.MakeName to create a name that follows existing conventions.
    Name string

    // Bootstrap nodes are used to establish connectivity
    // with the rest of the network.
    BootstrapNodes []*discover.Node

    // Protocols should contain the protocols supported
    // by the server. Matching protocols are launched for
    // each peer.
    Protocols []Protocol

    // If ListenAddr is set to a non-nil address, the server
    // will listen for incoming connections.
    //
    // If the port is zero, the operating system will pick a port. The
    // ListenAddr field will be updated with the actual address when
    // the server is started.
    ListenAddr string

    // If set to a non-nil value, the given NAT port mapper
    // is used to make the listening port available to the
    // Internet.
    NAT nat.Interface

    // If Dialer is set to a non-nil value, the given Dialer
    // is used to dial outbound peer connections.
    Dialer *net.Dialer

    // If NoDial is true, the server will not dial any peers.
    NoDial bool

    // Hooks for testing. These are useful because we can inhibit
    // the whole protocol stack.
    setupFunc
    newPeerHook

    ourHandshake *protoHandshake

    lock     sync.RWMutex
    running  bool
    listener net.Listener
    peers    map[discover.NodeID]*Peer

    ntab *discover.Table

    quit        chan struct{}
    loopWG      sync.WaitGroup // {dial,listen,nat}Loop
    peerWG      sync.WaitGroup // active peer goroutines
    peerConnect chan *discover.Node
}

type setupFunc func(net.Conn, *ecdsa.PrivateKey, *protoHandshake, *discover.Node) (*conn, error)
type newPeerHook func(*Peer)

// Peers returns all connected peers.
func (srv *Server) Peers() (peers []*Peer) {
    srv.lock.RLock()
    defer srv.lock.RUnlock()
    for _, peer := range srv.peers {
        if peer != nil {
            peers = append(peers, peer)
        }
    }
    return
}

// PeerCount returns the number of connected peers.
func (srv *Server) PeerCount() int {
    srv.lock.RLock()
    n := len(srv.peers)
    srv.lock.RUnlock()
    return n
}

// SuggestPeer creates a connection to the given Node if it
// is not already connected.
func (srv *Server) SuggestPeer(n *discover.Node) {
    srv.peerConnect <- n
}

// Broadcast sends an RLP-encoded message to all connected peers.
// This method is deprecated and will be removed later.
func (srv *Server) Broadcast(protocol string, code uint64, data interface{}) error {
    var payload []byte
    if data != nil {
        var err error
        payload, err = rlp.EncodeToBytes(data)
        if err != nil {
            return err
        }
    }
    srv.lock.RLock()
    defer srv.lock.RUnlock()
    for _, peer := range srv.peers {
        if peer != nil {
            var msg = Msg{Code: code}
            if data != nil {
                msg.Payload = bytes.NewReader(payload)
                msg.Size = uint32(len(payload))
            }
            peer.writeProtoMsg(protocol, msg)
        }
    }
    return nil
}

// Start starts running the server.
// Servers can be re-used and started again after stopping.
func (srv *Server) Start() (err error) {
    srv.lock.Lock()
    defer srv.lock.Unlock()
    if srv.running {
        return errors.New("server already running")
    }
    srvlog.Infoln("Starting Server")

    // static fields
    if srv.PrivateKey == nil {
        return fmt.Errorf("Server.PrivateKey must be set to a non-nil key")
    }
    if srv.MaxPeers <= 0 {
        return fmt.Errorf("Server.MaxPeers must be > 0")
    }
    srv.quit = make(chan struct{})
    srv.peers = make(map[discover.NodeID]*Peer)
    srv.peerConnect = make(chan *discover.Node)
    if srv.setupFunc == nil {
        srv.setupFunc = setupConn
    }

    // node table
    ntab, err := discover.ListenUDP(srv.PrivateKey, srv.ListenAddr, srv.NAT)
    if err != nil {
        return err
    }
    srv.ntab = ntab

    // handshake
    srv.ourHandshake = &protoHandshake{Version: baseProtocolVersion, Name: srv.Name, ID: ntab.Self().ID}
    for _, p := range srv.Protocols {
        srv.ourHandshake.Caps = append(srv.ourHandshake.Caps, p.cap())
    }

    // listen/dial
    if srv.ListenAddr != "" {
        if err := srv.startListening(); err != nil {
            return err
        }
    }
    if srv.Dialer == nil {
        srv.Dialer = &net.Dialer{Timeout: defaultDialTimeout}
    }
    if !srv.NoDial {
        srv.loopWG.Add(1)
        go srv.dialLoop()
    }
    if srv.NoDial && srv.ListenAddr == "" {
        srvlog.Warnln("I will be kind-of useless, neither dialing nor listening.")
    }

    srv.running = true
    return nil
}

func (srv *Server) startListening() error {
    listener, err := net.Listen("tcp", srv.ListenAddr)
    if err != nil {
        return err
    }
    laddr := listener.Addr().(*net.TCPAddr)
    srv.ListenAddr = laddr.String()
    srv.listener = listener
    srv.loopWG.Add(1)
    go srv.listenLoop()
    if !laddr.IP.IsLoopback() && srv.NAT != nil {
        srv.loopWG.Add(1)
        go func() {
            nat.Map(srv.NAT, srv.quit, "tcp", laddr.Port, laddr.Port, "ethereum p2p")
            srv.loopWG.Done()
        }()
    }
    return nil
}

// Stop terminates the server and all active peer connections.
// It blocks until all active connections have been closed.
func (srv *Server) Stop() {
    srv.lock.Lock()
    if !srv.running {
        srv.lock.Unlock()
        return
    }
    srv.running = false
    srv.lock.Unlock()

    srvlog.Infoln("Stopping Server")
    srv.ntab.Close()
    if srv.listener != nil {
        // this unblocks listener Accept
        srv.listener.Close()
    }
    close(srv.quit)
    srv.loopWG.Wait()

    // No new peers can be added at this point because dialLoop and
    // listenLoop are down. It is safe to call peerWG.Wait because
    // peerWG.Add is not called outside of those loops.
    for _, peer := range srv.peers {
        peer.Disconnect(DiscQuitting)
    }
    srv.peerWG.Wait()
}

// main loop for adding connections via listening
func (srv *Server) listenLoop() {
    defer srv.loopWG.Done()
    srvlog.Infoln("Listening on", srv.listener.Addr())
    for {
        conn, err := srv.listener.Accept()
        if err != nil {
            return
        }
        srvlog.Debugf("Accepted conn %v\n", conn.RemoteAddr())
        srv.peerWG.Add(1)
        go srv.startPeer(conn, nil)
    }
}

func (srv *Server) dialLoop() {
    defer srv.loopWG.Done()
    refresh := time.NewTicker(refreshPeersInterval)
    defer refresh.Stop()

    srv.ntab.Bootstrap(srv.BootstrapNodes)
    go srv.findPeers()

    dialed := make(chan *discover.Node)
    dialing := make(map[discover.NodeID]bool)

    // TODO: limit number of active dials
    // TODO: ensure only one findPeers goroutine is running
    // TODO: pause findPeers when we're at capacity

    for {
        select {
        case <-refresh.C:

            go srv.findPeers()

        case dest := <-srv.peerConnect:
            // avoid dialing nodes that are already connected.
            // there is another check for this in addPeer,
            // which runs after the handshake.
            srv.lock.Lock()
            _, isconnected := srv.peers[dest.ID]
            srv.lock.Unlock()
            if isconnected || dialing[dest.ID] || dest.ID == srv.Self().ID {
                continue
            }

            dialing[dest.ID] = true
            srv.peerWG.Add(1)
            go func() {
                srv.dialNode(dest)
                // at this point, the peer has been added
                // or discarded. either way, we're not dialing it anymore.
                dialed <- dest
            }()

        case dest := <-dialed:
            delete(dialing, dest.ID)

        case <-srv.quit:
            // TODO: maybe wait for active dials
            return
        }
    }
}

func (srv *Server) dialNode(dest *discover.Node) {
    addr := &net.TCPAddr{IP: dest.IP, Port: dest.TCPPort}
    srvlog.Debugf("Dialing %v\n", dest)
    conn, err := srv.Dialer.Dial("tcp", addr.String())
    if err != nil {
        srvlog.DebugDetailf("dial error: %v", err)
        return
    }
    srv.startPeer(conn, dest)
}

func (srv *Server) Self() *discover.Node {
    return srv.ntab.Self()
}

func (srv *Server) findPeers() {
    far := srv.Self().ID
    for i := range far {
        far[i] = ^far[i]
    }
    closeToSelf := srv.ntab.Lookup(srv.Self().ID)
    farFromSelf := srv.ntab.Lookup(far)

    for i := 0; i < len(closeToSelf) || i < len(farFromSelf); i++ {
        if i < len(closeToSelf) {
            srv.peerConnect <- closeToSelf[i]
        }
        if i < len(farFromSelf) {
            srv.peerConnect <- farFromSelf[i]
        }
    }
}

func (srv *Server) startPeer(fd net.Conn, dest *discover.Node) {
    // TODO: handle/store session token
    fd.SetDeadline(time.Now().Add(handshakeTimeout))
    conn, err := srv.setupFunc(fd, srv.PrivateKey, srv.ourHandshake, dest)
    if err != nil {
        fd.Close()
        srvlog.Debugf("Handshake with %v failed: %v", fd.RemoteAddr(), err)
        return
    }

    conn.MsgReadWriter = &netWrapper{
        wrapped: conn.MsgReadWriter,
        conn:    fd, rtimeout: frameReadTimeout, wtimeout: frameWriteTimeout,
    }
    p := newPeer(fd, conn, srv.Protocols)
    if ok, reason := srv.addPeer(conn.ID, p); !ok {
        srvlog.DebugDetailf("Not adding %v (%v)\n", p, reason)
        p.politeDisconnect(reason)
        return
    }

    srvlog.Debugf("Added %v\n", p)
    srvjslog.LogJson(&logger.P2PConnected{
        RemoteId:            fmt.Sprintf("%x", conn.ID[:]),
        RemoteAddress:       fd.RemoteAddr().String(),
        RemoteVersionString: conn.Name,
        NumConnections:      srv.PeerCount(),
    })

    if srv.newPeerHook != nil {
        srv.newPeerHook(p)
    }
    discreason := p.run()
    srv.removePeer(p)

    srvlog.Debugf("Removed %v (%v)\n", p, discreason)
    srvjslog.LogJson(&logger.P2PDisconnected{
        RemoteId:       fmt.Sprintf("%x", conn.ID[:]),
        NumConnections: srv.PeerCount(),
    })
}

func (srv *Server) addPeer(id discover.NodeID, p *Peer) (bool, DiscReason) {
    srv.lock.Lock()
    defer srv.lock.Unlock()
    switch {
    case !srv.running:
        return false, DiscQuitting
    case len(srv.peers) >= srv.MaxPeers:
        return false, DiscTooManyPeers
    case srv.peers[id] != nil:
        return false, DiscAlreadyConnected
    case id == srv.Self().ID:
        return false, DiscSelf
    }
    srv.peers[id] = p
    return true, 0
}

func (srv *Server) removePeer(p *Peer) {
    srv.lock.Lock()
    delete(srv.peers, p.ID())
    srv.lock.Unlock()
    srv.peerWG.Done()
}