path: root/p2p/peer.go

package p2p

import (
    "errors"
    "fmt"
    "io"
    "io/ioutil"
    "net"
    "sort"
    "sync"
    "time"

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

const (
    baseProtocolVersion    = 3
    baseProtocolLength     = uint64(16)
    baseProtocolMaxMsgSize = 10 * 1024 * 1024

    pingInterval          = 15 * time.Second
    disconnectGracePeriod = 2 * time.Second
)

const (
    // devp2p message codes
    handshakeMsg = 0x00
    discMsg      = 0x01
    pingMsg      = 0x02
    pongMsg      = 0x03
    getPeersMsg  = 0x04
    peersMsg     = 0x05
)

// Peer represents a connected remote node.
type Peer struct {
    // Peers have all the log methods.
    // Use them to display messages related to the peer.
    *logger.Logger

    conn    net.Conn
    rw      *conn
    running map[string]*protoRW

    wg       sync.WaitGroup
    protoErr chan error
    closed   chan struct{}
    disc     chan DiscReason
}

// NewPeer returns a peer for testing purposes.
func NewPeer(id discover.NodeID, name string, caps []Cap) *Peer {
    pipe, _ := net.Pipe()
    msgpipe, _ := MsgPipe()
    conn := &conn{msgpipe, &protoHandshake{ID: id, Name: name, Caps: caps}}
    peer := newPeer(pipe, conn, nil)
    close(peer.closed) // ensures Disconnect doesn't block
    return peer
}

// ID returns the node's public key.
func (p *Peer) ID() discover.NodeID {
    return p.rw.ID
}

// Name returns the node name that the remote node advertised.
func (p *Peer) Name() string {
    return p.rw.Name
}

// Caps returns the capabilities (supported subprotocols) of the remote peer.
func (p *Peer) Caps() []Cap {
    // TODO: maybe return copy
    return p.rw.Caps
}

// RemoteAddr returns the remote address of the network connection.
func (p *Peer) RemoteAddr() net.Addr {
    return p.conn.RemoteAddr()
}

// LocalAddr returns the local address of the network connection.
func (p *Peer) LocalAddr() net.Addr {
    return p.conn.LocalAddr()
}

// Disconnect terminates the peer connection with the given reason.
// It returns immediately and does not wait until the connection is closed.
func (p *Peer) Disconnect(reason DiscReason) {
    select {
    case p.disc <- reason:
    case <-p.closed:
    }
}

// String implements fmt.Stringer.
func (p *Peer) String() string {
    return fmt.Sprintf("Peer %.8x %v", p.rw.ID[:], p.RemoteAddr())
}

func newPeer(fd net.Conn, conn *conn, protocols []Protocol) *Peer {
    logtag := fmt.Sprintf("Peer %.8x %v", conn.ID[:], fd.RemoteAddr())
    protomap := matchProtocols(protocols, conn.Caps, conn)
    p := &Peer{
        Logger:   logger.NewLogger(logtag),
        conn:     fd,
        rw:       conn,
        running:  protomap,
        disc:     make(chan DiscReason),
        protoErr: make(chan error, len(protomap)+1), // protocols + pingLoop
        closed:   make(chan struct{}),
    }
    return p
}

func (p *Peer) run() DiscReason {
    readErr := make(chan error, 1)
    p.wg.Add(2)
    go p.readLoop(readErr)
    go p.pingLoop()

    p.startProtocols()

    // Wait for an error or disconnect.
    var reason DiscReason
    select {
    case err := <-readErr:
        if r, ok := err.(DiscReason); ok {
            reason = r
            break
        }
        // Note: We rely on protocols to abort if there is a write
        // error. It might be more robust to handle them here as well.
        p.DebugDetailf("Read error: %v\n", err)
        p.conn.Close()
        reason = DiscNetworkError
    case err := <-p.protoErr:
        reason = discReasonForError(err)
    case reason = <-p.disc:
    }

    close(p.closed)
    p.wg.Wait()
    if reason != DiscNetworkError {
        p.politeDisconnect(reason)
    }
    p.Debugf("Disconnected: %v\n", reason)
    return reason
}

func (p *Peer) politeDisconnect(reason DiscReason) {
    done := make(chan struct{})
    go func() {
        SendItems(p.rw, discMsg, uint(reason))
        // Wait for the other side to close the connection.
        // Discard any data that they send until then.
        io.Copy(ioutil.Discard, p.conn)
        close(done)
    }()
    select {
    case <-done:
    case <-time.After(disconnectGracePeriod):
    }
    p.conn.Close()
}

func (p *Peer) pingLoop() {
    ping := time.NewTicker(pingInterval)
    defer p.wg.Done()
    defer ping.Stop()
    for {
        select {
        case <-ping.C:
            if err := SendItems(p.rw, pingMsg); err != nil {
                p.protoErr <- err
                return
            }
        case <-p.closed:
            return
        }
    }
}

func (p *Peer) readLoop(errc chan<- error) {
    defer p.wg.Done()
    for {
        msg, err := p.rw.ReadMsg()
        if err != nil {
            errc <- err
            return
        }
        if err = p.handle(msg); err != nil {
            errc <- err
            return
        }
    }
}

func (p *Peer) handle(msg Msg) error {
    switch {
    case msg.Code == pingMsg:
        msg.Discard()
        go SendItems(p.rw, pongMsg)
    case msg.Code == discMsg:
        var reason [1]DiscReason
        // This is the last message. We don't need to discard or
        // check errors because, the connection will be closed after it.
        rlp.Decode(msg.Payload, &reason)
        p.Debugf("Disconnect requested: %v\n", reason[0])
        return DiscRequested
    case msg.Code < baseProtocolLength:
        // ignore other base protocol messages
        return msg.Discard()
    default:
        // it's a subprotocol message
        proto, err := p.getProto(msg.Code)
        if err != nil {
            return fmt.Errorf("msg code out of range: %v", msg.Code)
        }
        select {
        case proto.in <- msg:
            return nil
        case <-p.closed:
            return io.EOF
        }
    }
    return nil
}

// matchProtocols creates structures for matching named subprotocols.
func matchProtocols(protocols []Protocol, caps []Cap, rw MsgReadWriter) map[string]*protoRW {
    sort.Sort(capsByName(caps))
    offset := baseProtocolLength
    result := make(map[string]*protoRW)
outer:
    for _, cap := range caps {
        for _, proto := range protocols {
            if proto.Name == cap.Name && proto.Version == cap.Version && result[cap.Name] == nil {
                result[cap.Name] = &protoRW{Protocol: proto, offset: offset, in: make(chan Msg), w: rw}
                offset += proto.Length
                continue outer
            }
        }
    }
    return result
}

func (p *Peer) startProtocols() {
    p.wg.Add(len(p.running))
    for _, proto := range p.running {
        proto := proto
        proto.closed = p.closed
        p.DebugDetailf("Starting protocol %s/%d\n", proto.Name, proto.Version)
        go func() {
            err := proto.Run(p, proto)
            if err == nil {
                p.DebugDetailf("Protocol %s/%d returned\n", proto.Name, proto.Version)
                err = errors.New("protocol returned")
            } else {
                p.DebugDetailf("Protocol %s/%d error: %v\n", proto.Name, proto.Version, err)
            }
            p.protoErr <- err
            p.wg.Done()
        }()
    }
}

// getProto finds the protocol responsible for handling
// the given message code.
func (p *Peer) getProto(code uint64) (*protoRW, error) {
    for _, proto := range p.running {
        if code >= proto.offset && code < proto.offset+proto.Length {
            return proto, nil
        }
    }
    return nil, newPeerError(errInvalidMsgCode, "%d", code)
}

// writeProtoMsg sends the given message on behalf of the given named protocol.
// this exists because of Server.Broadcast.
func (p *Peer) writeProtoMsg(protoName string, msg Msg) error {
    proto, ok := p.running[protoName]
    if !ok {
        return fmt.Errorf("protocol %s not handled by peer", protoName)
    }
    if msg.Code >= proto.Length {
        return newPeerError(errInvalidMsgCode, "code %x is out of range for protocol %q", msg.Code, protoName)
    }
    msg.Code += proto.offset
    return p.rw.WriteMsg(msg)
}

type protoRW struct {
    Protocol
    in     chan Msg
    closed <-chan struct{}
    offset uint64
    w      MsgWriter
}

func (rw *protoRW) WriteMsg(msg Msg) error {
    if msg.Code >= rw.Length {
        return newPeerError(errInvalidMsgCode, "not handled")
    }
    msg.Code += rw.offset
    return rw.w.WriteMsg(msg)
}

func (rw *protoRW) ReadMsg() (Msg, error) {
    select {
    case msg := <-rw.in:
        msg.Code -= rw.offset
        return msg, nil
    case <-rw.closed:
        return Msg{}, io.EOF
    }
}