path: root/whisper/peer.go

package whisper

import (
    "fmt"
    "time"

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

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

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

    quit chan struct{}
}

// newPeer creates and initializes a new whisper peer connection, returning either
// the newly constructed link or a failure reason.
func newPeer(host *Whisper, remote *p2p.Peer, rw p2p.MsgReadWriter) (*peer, error) {
    p := &peer{
        host:  host,
        peer:  remote,
        ws:    rw,
        known: set.New(),
        quit:  make(chan struct{}),
    }
    if err := p.handshake(); err != nil {
        return nil, err
    }
    return p, nil
}

// start initiates the peer updater, periodically broadcasting the whisper packets
// into the network.
func (self *peer) start() {
    go self.update()
    self.peer.Debugln("whisper started")
}

// stop terminates the peer updater, stopping message forwarding to it.
func (self *peer) stop() {
    close(self.quit)
    self.peer.Debugln("whisper stopped")
}

// handshake sends the protocol initiation status message to the remote peer and
// verifies the remote status too.
func (self *peer) handshake() error {
    // Send the handshake status message asynchronously
    errc := make(chan error, 1)
    go func() {
        errc <- p2p.SendItems(self.ws, statusCode, protocolVersion)
    }()
    // Fetch the remote status packet and verify protocol match
    packet, err := self.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)
    if _, err := s.List(); err != nil {
        return fmt.Errorf("bad status message: %v", err)
    }
    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 (self *peer) update() {
    // Start the tickers for the updates
    expire := time.NewTicker(expirationTicks)
    transmit := time.NewTicker(transmissionTicks)

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

        case <-transmit.C:
            if err := self.broadcast(); err != nil {
                self.peer.Infoln("broadcast failed:", err)
                return
            }

        case <-self.quit:
            return
        }
    }
}

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

// marked checks if an envelope is already known to the remote peer.
func (self *peer) marked(envelope *Envelope) bool {
    return self.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 (self *peer) expire() {
    // Assemble the list of available envelopes
    available := set.NewNonTS()
    for _, envelope := range self.host.envelopes() {
        available.Add(envelope.Hash())
    }
    // Cross reference availability with known status
    unmark := make(map[common.Hash]struct{})
    self.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 {
        self.known.Remove(hash)
    }
}

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

    return nil
}