path: root/whisper/whisperv5/peer.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package whisperv5

import (
    "fmt"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/rlp"
    set "gopkg.in/fatih/set.v0"
)

// peer represents a whisper protocol peer connection.
type Peer struct {
    host    *Whisper
    peer    *p2p.Peer
    ws      p2p.MsgReadWriter
    trusted bool

    known *set.Set // Messages already known by the peer to avoid wasting bandwidth

    quit chan struct{}
}

// newPeer creates a new whisper peer object, but does not run the handshake itself.
func newPeer(host *Whisper, remote *p2p.Peer, rw p2p.MsgReadWriter) *Peer {
    return &Peer{
        host:    host,
        peer:    remote,
        ws:      rw,
        trusted: false,
        known:   set.New(),
        quit:    make(chan struct{}),
    }
}

// start initiates the peer updater, periodically broadcasting the whisper packets
// into the network.
func (p *Peer) start() {
    go p.update()
    glog.V(logger.Debug).Infof("%v: whisper started", p.peer)
}

// stop terminates the peer updater, stopping message forwarding to it.
func (p *Peer) stop() {
    close(p.quit)
    glog.V(logger.Debug).Infof("%v: whisper stopped", p.peer)
}

// handshake sends the protocol initiation status message to the remote peer and
// verifies the remote status too.
func (p *Peer) handshake() error {
    // Send the handshake status message asynchronously
    errc := make(chan error, 1)
    go func() {
        errc <- p2p.Send(p.ws, statusCode, ProtocolVersion)
    }()
    // Fetch the remote status packet and verify protocol match
    packet, err := p.ws.ReadMsg()
    if err != nil {
        return err
    }
    if packet.Code != statusCode {
        return fmt.Errorf("peer sent %x before status packet", packet.Code)
    }
    s := rlp.NewStream(packet.Payload, uint64(packet.Size))
    peerVersion, err := s.Uint()
    if err != nil {
        return fmt.Errorf("bad status message: %v", err)
    }
    if peerVersion != ProtocolVersion {
        return fmt.Errorf("protocol version mismatch %d != %d", peerVersion, ProtocolVersion)
    }
    // Wait until out own status is consumed too
    if err := <-errc; err != nil {
        return fmt.Errorf("failed to send status packet: %v", err)
    }
    return nil
}

// update executes periodic operations on the peer, including message transmission
// and expiration.
func (p *Peer) update() {
    // Start the tickers for the updates
    expire := time.NewTicker(expirationCycle)
    transmit := time.NewTicker(transmissionCycle)

    // Loop and transmit until termination is requested
    for {
        select {
        case <-expire.C:
            p.expire()

        case <-transmit.C:
            if err := p.broadcast(); err != nil {
                glog.V(logger.Info).Infof("%v: broadcast failed: %v", p.peer, err)
                return
            }

        case <-p.quit:
            return
        }
    }
}

// mark marks an envelope known to the peer so that it won't be sent back.
func (peer *Peer) mark(envelope *Envelope) {
    peer.known.Add(envelope.Hash())
}

// marked checks if an envelope is already known to the remote peer.
func (peer *Peer) marked(envelope *Envelope) bool {
    return peer.known.Has(envelope.Hash())
}

// expire iterates over all the known envelopes in the host and removes all
// expired (unknown) ones from the known list.
func (peer *Peer) expire() {
    // Assemble the list of available envelopes
    available := set.NewNonTS()
    for _, envelope := range peer.host.Envelopes() {
        available.Add(envelope.Hash())
    }
    // Cross reference availability with known status
    unmark := make(map[common.Hash]struct{})
    peer.known.Each(func(v interface{}) bool {
        if !available.Has(v.(common.Hash)) {
            unmark[v.(common.Hash)] = struct{}{}
        }
        return true
    })
    // Dump all known but unavailable
    for hash, _ := range unmark {
        peer.known.Remove(hash)
    }
}

// broadcast iterates over the collection of envelopes and transmits yet unknown
// ones over the network.
func (p *Peer) broadcast() error {
    // Fetch the envelopes and collect the unknown ones
    envelopes := p.host.Envelopes()
    transmit := make([]*Envelope, 0, len(envelopes))
    for _, envelope := range envelopes {
        if !p.marked(envelope) {
            transmit = append(transmit, envelope)
            p.mark(envelope)
        }
    }
    if len(transmit) == 0 {
        return nil
    }
    // Transmit the unknown batch (potentially empty)
    if err := p2p.Send(p.ws, messagesCode, transmit); err != nil {
        return err
    }
    glog.V(logger.Detail).Infoln(p.peer, "broadcasted", len(transmit), "message(s)")
    return nil
}