path: root/p2p/server.go

package p2p

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

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

const (
    defaultDialTimeout      = 15 * time.Second
    refreshPeersInterval    = 30 * time.Second
    staticPeerCheckInterval = 15 * time.Second

    // Maximum number of concurrently handshaking inbound connections.
    maxAcceptConns = 50

    // Maximum number of concurrently dialing outbound connections.
    maxDialingConns = 10

    // 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 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

    // MaxPendingPeers is the maximum number of peers that can be pending in the
    // handshake phase, counted separately for inbound and outbound connections.
    // Zero defaults to preset values.
    MaxPendingPeers 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

    // Static nodes are used as pre-configured connections which are always
    // maintained and re-connected on disconnects.
    StaticNodes []*discover.Node

    // Trusted nodes are used as pre-configured connections which are always
    // allowed to connect, even above the peer limit.
    TrustedNodes []*discover.Node

    // NodeDatabase is the path to the database containing the previously seen
    // live nodes in the network.
    NodeDatabase string

    // 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 // protects running, peers and the trust fields
    running      bool
    peers        map[discover.NodeID]*Peer
    staticNodes  map[discover.NodeID]*discover.Node // Map of currently maintained static remote nodes
    staticDial   chan *discover.Node                // Dial request channel reserved for the static nodes
    staticCycle  time.Duration                      // Overrides staticPeerCheckInterval, used for testing
    trustedNodes map[discover.NodeID]bool           // Set of currently trusted remote nodes

    ntab     *discover.Table
    listener net.Listener

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

type setupFunc func(net.Conn, *ecdsa.PrivateKey, *protoHandshake, *discover.Node, func(discover.NodeID) bool) (*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
}

// AddPeer connects to the given node and maintains the connection until the
// server is shut down. If the connection fails for any reason, the server will
// attempt to reconnect the peer.
func (srv *Server) AddPeer(node *discover.Node) {
    srv.lock.Lock()
    defer srv.lock.Unlock()

    srv.staticNodes[node.ID] = node
}

// 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")
    }
    glog.V(logger.Info).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)

    // Create the current trust maps, and the associated dialing channel
    srv.trustedNodes = make(map[discover.NodeID]bool)
    for _, node := range srv.TrustedNodes {
        srv.trustedNodes[node.ID] = true
    }
    srv.staticNodes = make(map[discover.NodeID]*discover.Node)
    for _, node := range srv.StaticNodes {
        srv.staticNodes[node.ID] = node
    }
    srv.staticDial = make(chan *discover.Node)

    if srv.setupFunc == nil {
        srv.setupFunc = setupConn
    }

    // node table
    ntab, err := discover.ListenUDP(srv.PrivateKey, srv.ListenAddr, srv.NAT, srv.NodeDatabase)
    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 == "" {
        glog.V(logger.Warn).Infoln("I will be kind-of useless, neither dialing nor listening.")
    }
    // maintain the static peers
    go srv.staticNodesLoop()

    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()

    glog.V(logger.Info).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.
    srv.lock.Lock()
    for _, peer := range srv.peers {
        peer.Disconnect(DiscQuitting)
    }
    srv.lock.Unlock()
    srv.peerWG.Wait()
}

// Self returns the local node's endpoint information.
func (srv *Server) Self() *discover.Node {
    srv.lock.RLock()
    defer srv.lock.RUnlock()
    if !srv.running {
        return &discover.Node{IP: net.ParseIP("0.0.0.0")}
    }
    return srv.ntab.Self()
}

// main loop for adding connections via listening
func (srv *Server) listenLoop() {
    defer srv.loopWG.Done()

    // This channel acts as a semaphore limiting
    // active inbound connections that are lingering pre-handshake.
    // If all slots are taken, no further connections are accepted.
    tokens := maxAcceptConns
    if srv.MaxPendingPeers > 0 {
        tokens = srv.MaxPendingPeers
    }
    slots := make(chan struct{}, tokens)
    for i := 0; i < tokens; i++ {
        slots <- struct{}{}
    }

    glog.V(logger.Info).Infoln("Listening on", srv.listener.Addr())
    for {
        <-slots
        conn, err := srv.listener.Accept()
        if err != nil {
            return
        }
        glog.V(logger.Debug).Infof("Accepted conn %v\n", conn.RemoteAddr())
        srv.peerWG.Add(1)
        go func() {
            srv.startPeer(conn, nil)
            slots <- struct{}{}
        }()
    }
}

// staticNodesLoop is responsible for periodically checking that static
// connections are actually live, and requests dialing if not.
func (srv *Server) staticNodesLoop() {
    // Create a default maintenance ticker, but override it requested
    cycle := staticPeerCheckInterval
    if srv.staticCycle != 0 {
        cycle = srv.staticCycle
    }
    tick := time.NewTicker(cycle)

    for {
        select {
        case <-srv.quit:
            return

        case <-tick.C:
            // Collect all the non-connected static nodes
            needed := []*discover.Node{}
            srv.lock.RLock()
            for id, node := range srv.staticNodes {
                if _, ok := srv.peers[id]; !ok {
                    needed = append(needed, node)
                }
            }
            srv.lock.RUnlock()

            // Try to dial each of them (don't hang if server terminates)
            for _, node := range needed {
                glog.V(logger.Debug).Infof("Dialing static peer %v", node)
                select {
                case srv.staticDial <- node:
                case <-srv.quit:
                    return
                }
            }
        }
    }
}

func (srv *Server) dialLoop() {
    var (
        dialed      = make(chan *discover.Node)
        dialing     = make(map[discover.NodeID]bool)
        findresults = make(chan []*discover.Node)
        refresh     = time.NewTimer(0)
    )
    defer srv.loopWG.Done()
    defer refresh.Stop()

    // Limit the number of concurrent dials
    tokens := maxDialingConns
    if srv.MaxPendingPeers > 0 {
        tokens = srv.MaxPendingPeers
    }
    slots := make(chan struct{}, tokens)
    for i := 0; i < tokens; i++ {
        slots <- struct{}{}
    }
    dial := func(dest *discover.Node) {
        // Don't dial nodes that would fail the checks in addPeer.
        // This is important because the connection handshake is a lot
        // of work and we'd rather avoid doing that work for peers
        // that can't be added.
        srv.lock.RLock()
        ok, _ := srv.checkPeer(dest.ID)
        srv.lock.RUnlock()
        if !ok || dialing[dest.ID] {
            return
        }
        // Request a dial slot to prevent CPU exhaustion
        <-slots

        dialing[dest.ID] = true
        srv.peerWG.Add(1)
        go func() {
            srv.dialNode(dest)
            slots <- struct{}{}
            dialed <- dest
        }()
    }

    srv.ntab.Bootstrap(srv.BootstrapNodes)
    for {
        select {
        case <-refresh.C:
            // Grab some nodes to connect to if we're not at capacity.
            srv.lock.RLock()
            needpeers := len(srv.peers) < srv.MaxPeers/2
            srv.lock.RUnlock()
            if needpeers {
                go func() {
                    var target discover.NodeID
                    rand.Read(target[:])
                    findresults <- srv.ntab.Lookup(target)
                }()
            } else {
                // Make sure we check again if the peer count falls
                // below MaxPeers.
                refresh.Reset(refreshPeersInterval)
            }
        case dest := <-srv.staticDial:
            dial(dest)
        case dests := <-findresults:
            for _, dest := range dests {
                dial(dest)
            }
            refresh.Reset(refreshPeersInterval)
        case dest := <-dialed:
            delete(dialing, dest.ID)
            if len(dialing) == 0 {
                // Check again immediately after dialing all current candidates.
                refresh.Reset(0)
            }
        case <-srv.quit:
            // TODO: maybe wait for active dials
            return
        }
    }
}

func (srv *Server) dialNode(dest *discover.Node) {
    addr := &net.TCPAddr{IP: dest.IP, Port: int(dest.TCP)}
    glog.V(logger.Debug).Infof("Dialing %v\n", dest)
    conn, err := srv.Dialer.Dial("tcp", addr.String())
    if err != nil {
        // dialLoop adds to the wait group counter when launching
        // dialNode, so we need to count it down again. startPeer also
        // does that when an error occurs.
        srv.peerWG.Done()
        glog.V(logger.Detail).Infof("dial error: %v", err)
        return
    }
    srv.startPeer(conn, dest)
}

func (srv *Server) startPeer(fd net.Conn, dest *discover.Node) {
    // TODO: handle/store session token

    // Run setupFunc, which should create an authenticated connection
    // and run the capability exchange. Note that any early error
    // returns during that exchange need to call peerWG.Done because
    // the callers of startPeer added the peer to the wait group already.
    fd.SetDeadline(time.Now().Add(handshakeTimeout))

    conn, err := srv.setupFunc(fd, srv.PrivateKey, srv.ourHandshake, dest, srv.keepconn)
    if err != nil {
        fd.Close()
        glog.V(logger.Debug).Infof("Handshake with %v failed: %v", fd.RemoteAddr(), err)
        srv.peerWG.Done()
        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, p); !ok {
        glog.V(logger.Detail).Infof("Not adding %v (%v)\n", p, reason)
        p.politeDisconnect(reason)
        srv.peerWG.Done()
        return
    }
    // The handshakes are done and it passed all checks.
    // Spawn the Peer loops.
    go srv.runPeer(p)
}

// preflight checks whether a connection should be kept. it runs
// after the encryption handshake, as soon as the remote identity is
// known.
func (srv *Server) keepconn(id discover.NodeID) bool {
    srv.lock.RLock()
    defer srv.lock.RUnlock()
    if _, ok := srv.staticNodes[id]; ok {
        return true // static nodes are always allowed
    }
    if _, ok := srv.trustedNodes[id]; ok {
        return true // trusted nodes are always allowed
    }
    return len(srv.peers) < srv.MaxPeers
}

func (srv *Server) runPeer(p *Peer) {
    glog.V(logger.Debug).Infof("Added %v\n", p)
    srvjslog.LogJson(&logger.P2PConnected{
        RemoteId:            p.ID().String(),
        RemoteAddress:       p.RemoteAddr().String(),
        RemoteVersionString: p.Name(),
        NumConnections:      srv.PeerCount(),
    })
    if srv.newPeerHook != nil {
        srv.newPeerHook(p)
    }
    discreason := p.run()
    srv.removePeer(p)
    glog.V(logger.Debug).Infof("Removed %v (%v)\n", p, discreason)
    srvjslog.LogJson(&logger.P2PDisconnected{
        RemoteId:       p.ID().String(),
        NumConnections: srv.PeerCount(),
    })
}

func (srv *Server) addPeer(conn *conn, p *Peer) (bool, DiscReason) {
    // drop connections with no matching protocols.
    if len(srv.Protocols) > 0 && countMatchingProtocols(srv.Protocols, conn.protoHandshake.Caps) == 0 {
        return false, DiscUselessPeer
    }
    // add the peer if it passes the other checks.
    srv.lock.Lock()
    defer srv.lock.Unlock()
    if ok, reason := srv.checkPeer(conn.ID); !ok {
        return false, reason
    }
    srv.peers[conn.ID] = p
    return true, 0
}

// checkPeer verifies whether a peer looks promising and should be allowed/kept
// in the pool, or if it's of no use.
func (srv *Server) checkPeer(id discover.NodeID) (bool, DiscReason) {
    // First up, figure out if the peer is static or trusted
    _, static := srv.staticNodes[id]
    trusted := srv.trustedNodes[id]

    // Make sure the peer passes all required checks
    switch {
    case !srv.running:
        return false, DiscQuitting
    case !static && !trusted && len(srv.peers) >= srv.MaxPeers:
        return false, DiscTooManyPeers
    case srv.peers[id] != nil:
        return false, DiscAlreadyConnected
    case id == srv.ntab.Self().ID:
        return false, DiscSelf
    default:
        return true, 0
    }
}

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