path: root/peer.go

package eth

import (
    "bytes"
    "container/list"
    "fmt"
    "math"
    "math/big"
    "net"
    "strconv"
    "strings"
    "sync/atomic"
    "time"

    "github.com/ethereum/eth-go/ethchain"
    "github.com/ethereum/eth-go/ethlog"
    "github.com/ethereum/eth-go/ethutil"
    "github.com/ethereum/eth-go/ethwire"
)

var peerlogger = ethlog.NewLogger("PEER")

const (
    // The size of the output buffer for writing messages
    outputBufferSize = 50
    // Current protocol version
    ProtocolVersion = 34
    // Current P2P version
    P2PVersion = 0
    // Ethereum network version
    NetVersion = 0
    // Interval for ping/pong message
    pingPongTimer = 2 * time.Second
)

type DiscReason byte

const (
    // Values are given explicitly instead of by iota because these values are
    // defined by the wire protocol spec; it is easier for humans to ensure
    // correctness when values are explicit.
    DiscRequested DiscReason = iota
    DiscReTcpSysErr
    DiscBadProto
    DiscBadPeer
    DiscTooManyPeers
    DiscConnDup
    DiscGenesisErr
    DiscProtoErr
    DiscQuitting
)

var discReasonToString = []string{
    "requested",
    "TCP sys error",
    "bad protocol",
    "useless peer",
    "too many peers",
    "already connected",
    "wrong genesis block",
    "incompatible network",
    "quitting",
}

func (d DiscReason) String() string {
    if len(discReasonToString) < int(d) {
        return "Unknown"
    }

    return discReasonToString[d]
}

// Peer capabilities
type Caps byte

const (
    CapPeerDiscTy Caps = 1 << iota
    CapTxTy
    CapChainTy

    CapDefault = CapChainTy | CapTxTy | CapPeerDiscTy
)

var capsToString = map[Caps]string{
    CapPeerDiscTy: "Peer discovery",
    CapTxTy:       "Transaction relaying",
    CapChainTy:    "Block chain relaying",
}

func (c Caps) IsCap(cap Caps) bool {
    return c&cap > 0
}

func (c Caps) String() string {
    var caps []string
    if c.IsCap(CapPeerDiscTy) {
        caps = append(caps, capsToString[CapPeerDiscTy])
    }
    if c.IsCap(CapChainTy) {
        caps = append(caps, capsToString[CapChainTy])
    }
    if c.IsCap(CapTxTy) {
        caps = append(caps, capsToString[CapTxTy])
    }

    return strings.Join(caps, " | ")
}

type Peer struct {
    // Ethereum interface
    ethereum *Ethereum
    // Net connection
    conn net.Conn
    // Output queue which is used to communicate and handle messages
    outputQueue chan *ethwire.Msg
    // Quit channel
    quit chan bool
    // Determines whether it's an inbound or outbound peer
    inbound bool
    // Flag for checking the peer's connectivity state
    connected  int32
    disconnect int32
    // Last known message send
    lastSend time.Time
    // Indicated whether a verack has been send or not
    // This flag is used by writeMessage to check if messages are allowed
    // to be send or not. If no version is known all messages are ignored.
    versionKnown bool
    statusKnown  bool

    // Last received pong message
    lastPong           int64
    lastBlockReceived  time.Time
    doneFetchingHashes bool

    host             []byte
    port             uint16
    caps             Caps
    td               *big.Int
    bestHash         []byte
    lastReceivedHash []byte
    requestedHashes  [][]byte

    // This peer's public key
    pubkey []byte

    // Indicated whether the node is catching up or not
    catchingUp      bool
    diverted        bool
    blocksRequested int

    version string

    // We use this to give some kind of pingtime to a node, not very accurate, could be improved.
    pingTime      time.Duration
    pingStartTime time.Time

    lastRequestedBlock *ethchain.Block

    protocolCaps *ethutil.Value
}

func NewPeer(conn net.Conn, ethereum *Ethereum, inbound bool) *Peer {
    pubkey := ethereum.KeyManager().PublicKey()[1:]

    return &Peer{
        outputQueue:        make(chan *ethwire.Msg, outputBufferSize),
        quit:               make(chan bool),
        ethereum:           ethereum,
        conn:               conn,
        inbound:            inbound,
        disconnect:         0,
        connected:          1,
        port:               30303,
        pubkey:             pubkey,
        blocksRequested:    10,
        caps:               ethereum.ServerCaps(),
        version:            ethereum.ClientIdentity().String(),
        protocolCaps:       ethutil.NewValue(nil),
        td:                 big.NewInt(0),
        doneFetchingHashes: true,
    }
}

func NewOutboundPeer(addr string, ethereum *Ethereum, caps Caps) *Peer {
    p := &Peer{
        outputQueue:        make(chan *ethwire.Msg, outputBufferSize),
        quit:               make(chan bool),
        ethereum:           ethereum,
        inbound:            false,
        connected:          0,
        disconnect:         0,
        port:               30303,
        caps:               caps,
        version:            ethereum.ClientIdentity().String(),
        protocolCaps:       ethutil.NewValue(nil),
        td:                 big.NewInt(0),
        doneFetchingHashes: true,
    }

    // Set up the connection in another goroutine so we don't block the main thread
    go func() {
        conn, err := p.Connect(addr)
        if err != nil {
            //peerlogger.Debugln("Connection to peer failed. Giving up.", err)
            p.Stop()
            return
        }
        p.conn = conn

        // Atomically set the connection state
        atomic.StoreInt32(&p.connected, 1)
        atomic.StoreInt32(&p.disconnect, 0)

        p.Start()
    }()

    return p
}

func (self *Peer) Connect(addr string) (conn net.Conn, err error) {
    const maxTries = 3
    for attempts := 0; attempts < maxTries; attempts++ {
        conn, err = net.DialTimeout("tcp", addr, 10*time.Second)
        if err != nil {
            time.Sleep(time.Duration(attempts*20) * time.Second)
            continue
        }

        // Success
        return
    }

    return
}

// Getters
func (p *Peer) PingTime() string {
    return p.pingTime.String()
}
func (p *Peer) Inbound() bool {
    return p.inbound
}
func (p *Peer) LastSend() time.Time {
    return p.lastSend
}
func (p *Peer) LastPong() int64 {
    return p.lastPong
}
func (p *Peer) Host() []byte {
    return p.host
}
func (p *Peer) Port() uint16 {
    return p.port
}
func (p *Peer) Version() string {
    return p.version
}
func (p *Peer) Connected() *int32 {
    return &p.connected
}

// Setters
func (p *Peer) SetVersion(version string) {
    p.version = version
}

// Outputs any RLP encoded data to the peer
func (p *Peer) QueueMessage(msg *ethwire.Msg) {
    if atomic.LoadInt32(&p.connected) != 1 {
        return
    }
    p.outputQueue <- msg
}

func (p *Peer) writeMessage(msg *ethwire.Msg) {
    // Ignore the write if we're not connected
    if atomic.LoadInt32(&p.connected) != 1 {
        return
    }

    if !p.versionKnown {
        switch msg.Type {
        case ethwire.MsgHandshakeTy: // Ok
        default: // Anything but ack is allowed
            return
        }
    } else {
        /*
            if !p.statusKnown {
                switch msg.Type {
                case ethwire.MsgStatusTy: // Ok
                default: // Anything but ack is allowed
                    return
                }
            }
        */
    }

    peerlogger.DebugDetailf("(%v) <= %v\n", p.conn.RemoteAddr(), formatMessage(msg))

    err := ethwire.WriteMessage(p.conn, msg)
    if err != nil {
        peerlogger.Debugln(" Can't send message:", err)
        // Stop the client if there was an error writing to it
        p.Stop()
        return
    }
}

// Outbound message handler. Outbound messages are handled here
func (p *Peer) HandleOutbound() {
    // The ping timer. Makes sure that every 2 minutes a ping is send to the peer
    pingTimer := time.NewTicker(pingPongTimer)
    serviceTimer := time.NewTicker(10 * time.Second)

out:
    for {
    skip:
        select {
        // Main message queue. All outbound messages are processed through here
        case msg := <-p.outputQueue:
            if !p.statusKnown {
                switch msg.Type {
                case ethwire.MsgGetTxsTy, ethwire.MsgTxTy, ethwire.MsgGetBlockHashesTy, ethwire.MsgBlockHashesTy, ethwire.MsgGetBlocksTy, ethwire.MsgBlockTy:
                    break skip
                }
            }

            p.writeMessage(msg)
            p.lastSend = time.Now()

        // Ping timer
        case <-pingTimer.C:
            /*
                timeSince := time.Since(time.Unix(p.lastPong, 0))
                if !p.pingStartTime.IsZero() && p.lastPong != 0 && timeSince > (pingPongTimer+30*time.Second) {
                    peerlogger.Infof("Peer did not respond to latest pong fast enough, it took %s, disconnecting.\n", timeSince)
                    p.Stop()
                    return
                }
            */
            p.writeMessage(ethwire.NewMessage(ethwire.MsgPingTy, ""))
            p.pingStartTime = time.Now()

        // Service timer takes care of peer broadcasting, transaction
        // posting or block posting
        case <-serviceTimer.C:
            p.QueueMessage(ethwire.NewMessage(ethwire.MsgGetPeersTy, ""))

        case <-p.quit:
            // Break out of the for loop if a quit message is posted
            break out
        }
    }

clean:
    // This loop is for draining the output queue and anybody waiting for us
    for {
        select {
        case <-p.outputQueue:
            // TODO
        default:
            break clean
        }
    }
}

func formatMessage(msg *ethwire.Msg) (ret string) {
    ret = fmt.Sprintf("%v %v", msg.Type, msg.Data)

    /*
        XXX Commented out because I need the log level here to determine
        if i should or shouldn't generate this message
    */
    /*
        switch msg.Type {
        case ethwire.MsgPeersTy:
            ret += fmt.Sprintf("(%d entries)", msg.Data.Len())
        case ethwire.MsgBlockTy:
            b1, b2 := ethchain.NewBlockFromRlpValue(msg.Data.Get(0)), ethchain.NewBlockFromRlpValue(msg.Data.Get(msg.Data.Len()-1))
            ret += fmt.Sprintf("(%d entries) %x - %x", msg.Data.Len(), b1.Hash()[0:4], b2.Hash()[0:4])
        case ethwire.MsgBlockHashesTy:
            h1, h2 := msg.Data.Get(0).Bytes(), msg.Data.Get(msg.Data.Len()-1).Bytes()
            ret += fmt.Sprintf("(%d entries) %x - %x", msg.Data.Len(), h1, h2)
        }
    */

    return
}

// Inbound handler. Inbound messages are received here and passed to the appropriate methods
func (p *Peer) HandleInbound() {
    for atomic.LoadInt32(&p.disconnect) == 0 {

        // HMM?
        time.Sleep(50 * time.Millisecond)
        // Wait for a message from the peer
        msgs, err := ethwire.ReadMessages(p.conn)
        if err != nil {
            peerlogger.Debugln(err)
        }
        for _, msg := range msgs {
            peerlogger.DebugDetailf("(%v) => %v\n", p.conn.RemoteAddr(), formatMessage(msg))

            switch msg.Type {
            case ethwire.MsgHandshakeTy:
                // Version message
                p.handleHandshake(msg)

                //if p.caps.IsCap(CapPeerDiscTy) {
                p.QueueMessage(ethwire.NewMessage(ethwire.MsgGetPeersTy, ""))
                //}

            case ethwire.MsgDiscTy:
                p.Stop()
                peerlogger.Infoln("Disconnect peer: ", DiscReason(msg.Data.Get(0).Uint()))
            case ethwire.MsgPingTy:
                // Respond back with pong
                p.QueueMessage(ethwire.NewMessage(ethwire.MsgPongTy, ""))
            case ethwire.MsgPongTy:
                // If we received a pong back from a peer we set the
                // last pong so the peer handler knows this peer is still
                // active.
                p.lastPong = time.Now().Unix()
                p.pingTime = time.Since(p.pingStartTime)
            case ethwire.MsgTxTy:
                // If the message was a transaction queue the transaction
                // in the TxPool where it will undergo validation and
                // processing when a new block is found
                for i := 0; i < msg.Data.Len(); i++ {
                    tx := ethchain.NewTransactionFromValue(msg.Data.Get(i))
                    p.ethereum.TxPool().QueueTransaction(tx)
                }
            case ethwire.MsgGetPeersTy:
                // Peer asked for list of connected peers
                p.pushPeers()
            case ethwire.MsgPeersTy:
                // Received a list of peers (probably because MsgGetPeersTy was send)
                data := msg.Data
                // Create new list of possible peers for the ethereum to process
                peers := make([]string, data.Len())
                // Parse each possible peer
                for i := 0; i < data.Len(); i++ {
                    value := data.Get(i)
                    peers[i] = unpackAddr(value.Get(0), value.Get(1).Uint())
                }

                // Connect to the list of peers
                p.ethereum.ProcessPeerList(peers)

            case ethwire.MsgStatusTy:
                // Handle peer's status msg
                p.handleStatus(msg)
            }

            // TMP
            if p.statusKnown {
                switch msg.Type {
                case ethwire.MsgGetTxsTy:
                    // Get the current transactions of the pool
                    txs := p.ethereum.TxPool().CurrentTransactions()
                    // Get the RlpData values from the txs
                    txsInterface := make([]interface{}, len(txs))
                    for i, tx := range txs {
                        txsInterface[i] = tx.RlpData()
                    }
                    // Broadcast it back to the peer
                    p.QueueMessage(ethwire.NewMessage(ethwire.MsgTxTy, txsInterface))

                case ethwire.MsgGetBlockHashesTy:
                    if msg.Data.Len() < 2 {
                        peerlogger.Debugln("err: argument length invalid ", msg.Data.Len())
                    }

                    hash := msg.Data.Get(0).Bytes()
                    amount := msg.Data.Get(1).Uint()

                    hashes := p.ethereum.BlockChain().GetChainHashesFromHash(hash, amount)

                    p.QueueMessage(ethwire.NewMessage(ethwire.MsgBlockHashesTy, ethutil.ByteSliceToInterface(hashes)))

                case ethwire.MsgGetBlocksTy:
                    // Limit to max 300 blocks
                    max := int(math.Min(float64(msg.Data.Len()), 300.0))
                    var blocks []interface{}

                    for i := 0; i < max; i++ {
                        hash := msg.Data.Get(i).Bytes()
                        block := p.ethereum.BlockChain().GetBlock(hash)
                        if block != nil {
                            blocks = append(blocks, block.Value().Raw())
                        }
                    }

                    p.QueueMessage(ethwire.NewMessage(ethwire.MsgBlockTy, blocks))

                case ethwire.MsgBlockHashesTy:
                    p.catchingUp = true

                    blockPool := p.ethereum.blockPool

                    foundCommonHash := false

                    it := msg.Data.NewIterator()
                    for it.Next() {
                        hash := it.Value().Bytes()
                        p.lastReceivedHash = hash

                        if blockPool.HasCommonHash(hash) {
                            foundCommonHash = true

                            break
                        }

                        blockPool.AddHash(hash, p)
                    }

                    if !foundCommonHash {
                        //if !p.FetchHashes() {
                        //  p.doneFetchingHashes = true
                        //}
                        p.FetchHashes()
                    } else {
                        peerlogger.Infof("Found common hash (%x...)\n", p.lastReceivedHash[0:4])
                        p.doneFetchingHashes = true
                    }

                case ethwire.MsgBlockTy:
                    p.catchingUp = true

                    blockPool := p.ethereum.blockPool

                    it := msg.Data.NewIterator()
                    for it.Next() {
                        block := ethchain.NewBlockFromRlpValue(it.Value())
                        blockPool.Add(block, p)

                        p.lastBlockReceived = time.Now()
                    }
                case ethwire.MsgNewBlockTy:
                    var (
                        blockPool = p.ethereum.blockPool
                        block     = ethchain.NewBlockFromRlpValue(msg.Data.Get(0))
                        td        = msg.Data.Get(1).BigInt()
                    )

                    if td.Cmp(blockPool.td) > 0 {
                        p.ethereum.blockPool.AddNew(block, p)
                    }
                }

            }
        }
    }

    p.Stop()
}

func (self *Peer) FetchBlocks(hashes [][]byte) {
    if len(hashes) > 0 {
        peerlogger.Debugf("Fetching blocks (%d)\n", len(hashes))

        self.QueueMessage(ethwire.NewMessage(ethwire.MsgGetBlocksTy, ethutil.ByteSliceToInterface(hashes)))
    }
}

func (self *Peer) FetchHashes() bool {
    blockPool := self.ethereum.blockPool

    return blockPool.FetchHashes(self)
}

func (self *Peer) FetchingHashes() bool {
    return !self.doneFetchingHashes
}

// General update method
func (self *Peer) update() {
    serviceTimer := time.NewTicker(100 * time.Millisecond)

out:
    for {
        select {
        case <-serviceTimer.C:
            if self.IsCap("eth") {
                var (
                    sinceBlock = time.Since(self.lastBlockReceived)
                )

                if sinceBlock > 5*time.Second {
                    self.catchingUp = false
                }
            }
        case <-self.quit:
            break out
        }
    }

    serviceTimer.Stop()
}

func (p *Peer) Start() {
    peerHost, peerPort, _ := net.SplitHostPort(p.conn.LocalAddr().String())
    servHost, servPort, _ := net.SplitHostPort(p.conn.RemoteAddr().String())

    if p.inbound {
        p.host, p.port = packAddr(peerHost, peerPort)
    } else {
        p.host, p.port = packAddr(servHost, servPort)
    }

    err := p.pushHandshake()
    if err != nil {
        peerlogger.Debugln("Peer can't send outbound version ack", err)

        p.Stop()

        return
    }

    go p.HandleOutbound()
    // Run the inbound handler in a new goroutine
    go p.HandleInbound()
    // Run the general update handler
    go p.update()

    // Wait a few seconds for startup and then ask for an initial ping
    time.Sleep(2 * time.Second)
    p.writeMessage(ethwire.NewMessage(ethwire.MsgPingTy, ""))
    p.pingStartTime = time.Now()

}

func (p *Peer) Stop() {
    p.StopWithReason(DiscRequested)
}

func (p *Peer) StopWithReason(reason DiscReason) {
    if atomic.AddInt32(&p.disconnect, 1) != 1 {
        return
    }

    // Pre-emptively remove the peer; don't wait for reaping. We already know it's dead if we are here
    p.ethereum.RemovePeer(p)

    close(p.quit)
    if atomic.LoadInt32(&p.connected) != 0 {
        p.writeMessage(ethwire.NewMessage(ethwire.MsgDiscTy, reason))
        p.conn.Close()
    }
}

func (p *Peer) peersMessage() *ethwire.Msg {
    outPeers := make([]interface{}, len(p.ethereum.InOutPeers()))
    // Serialise each peer
    for i, peer := range p.ethereum.InOutPeers() {
        // Don't return localhost as valid peer
        if !net.ParseIP(peer.conn.RemoteAddr().String()).IsLoopback() {
            outPeers[i] = peer.RlpData()
        }
    }

    // Return the message to the peer with the known list of connected clients
    return ethwire.NewMessage(ethwire.MsgPeersTy, outPeers)
}

// Pushes the list of outbound peers to the client when requested
func (p *Peer) pushPeers() {
    p.QueueMessage(p.peersMessage())
}

func (self *Peer) pushStatus() {
    msg := ethwire.NewMessage(ethwire.MsgStatusTy, []interface{}{
        uint32(ProtocolVersion),
        uint32(NetVersion),
        self.ethereum.BlockChain().TD,
        self.ethereum.BlockChain().CurrentBlock.Hash(),
        self.ethereum.BlockChain().Genesis().Hash(),
    })

    self.QueueMessage(msg)
}

func (self *Peer) handleStatus(msg *ethwire.Msg) {
    c := msg.Data

    var (
        protoVersion = c.Get(0).Uint()
        netVersion   = c.Get(1).Uint()
        td           = c.Get(2).BigInt()
        bestHash     = c.Get(3).Bytes()
        genesis      = c.Get(4).Bytes()
    )

    if bytes.Compare(self.ethereum.BlockChain().Genesis().Hash(), genesis) != 0 {
        ethlogger.Warnf("Invalid genisis hash %x. Disabling [eth]\n", genesis)
        return
    }

    if netVersion != NetVersion {
        ethlogger.Warnf("Invalid network version %d. Disabling [eth]\n", netVersion)
        return
    }

    if protoVersion != ProtocolVersion {
        ethlogger.Warnf("Invalid protocol version %d. Disabling [eth]\n", protoVersion)
        return
    }

    // Get the td and last hash
    self.td = td
    self.bestHash = bestHash
    self.lastReceivedHash = bestHash

    self.statusKnown = true

    // Compare the total TD with the blockchain TD. If remote is higher
    // fetch hashes from highest TD node.
    self.FetchHashes()

    ethlogger.Infof("Peer is [eth] capable. (TD = %v ~ %x) %d / %d", self.td, self.bestHash, protoVersion, netVersion)

}

func (p *Peer) pushHandshake() error {
    pubkey := p.ethereum.KeyManager().PublicKey()
    msg := ethwire.NewMessage(ethwire.MsgHandshakeTy, []interface{}{
        P2PVersion, []byte(p.version), []interface{}{"eth"}, p.port, pubkey[1:],
    })

    p.QueueMessage(msg)

    return nil
}

func (p *Peer) handleHandshake(msg *ethwire.Msg) {
    c := msg.Data

    var (
        p2pVersion = c.Get(0).Uint()
        clientId   = c.Get(1).Str()
        caps       = c.Get(2)
        port       = c.Get(3).Uint()
        pub        = c.Get(4).Bytes()
    )

    // Check correctness of p2p protocol version
    if p2pVersion != P2PVersion {
        peerlogger.Debugf("Invalid P2P version. Require protocol %d, received %d\n", P2PVersion, p2pVersion)
        p.Stop()
        return
    }

    // Handle the pub key (validation, uniqueness)
    if len(pub) == 0 {
        peerlogger.Warnln("Pubkey required, not supplied in handshake.")
        p.Stop()
        return
    }

    // Self connect detection
    pubkey := p.ethereum.KeyManager().PublicKey()
    if bytes.Compare(pubkey[1:], pub) == 0 {
        p.Stop()

        return
    }

    // Check for blacklisting
    for _, pk := range p.ethereum.blacklist {
        if bytes.Compare(pk, pub) == 0 {
            peerlogger.Debugf("Blacklisted peer tried to connect (%x...)\n", pubkey[0:4])
            p.StopWithReason(DiscBadPeer)

            return
        }
    }

    usedPub := 0
    // This peer is already added to the peerlist so we expect to find a double pubkey at least once
    eachPeer(p.ethereum.Peers(), func(peer *Peer, e *list.Element) {
        if bytes.Compare(pub, peer.pubkey) == 0 {
            usedPub++
        }
    })

    if usedPub > 0 {
        peerlogger.Debugf("Pubkey %x found more then once. Already connected to client.", p.pubkey)
        p.Stop()
        return
    }
    p.pubkey = pub

    // If this is an inbound connection send an ack back
    if p.inbound {
        p.port = uint16(port)
    }

    p.SetVersion(clientId)

    p.versionKnown = true

    p.ethereum.PushPeer(p)
    p.ethereum.eventMux.Post(PeerListEvent{p.ethereum.Peers()})

    p.protocolCaps = caps
    capsIt := caps.NewIterator()
    var capsStrs []string
    for capsIt.Next() {
        cap := capsIt.Value().Str()
        switch cap {
        case "eth":
            p.pushStatus()
        }

        capsStrs = append(capsStrs, cap)
    }

    ethlogger.Infof("Added peer (%s) %d / %d (%v)\n", p.conn.RemoteAddr(), p.ethereum.Peers().Len(), p.ethereum.MaxPeers, capsStrs)

    peerlogger.Debugln(p)
}

func (self *Peer) IsCap(cap string) bool {
    capsIt := self.protocolCaps.NewIterator()
    for capsIt.Next() {
        if capsIt.Value().Str() == cap {
            return true
        }
    }

    return false
}

func (self *Peer) Caps() *ethutil.Value {
    return self.protocolCaps
}

func (p *Peer) String() string {
    var strBoundType string
    if p.inbound {
        strBoundType = "inbound"
    } else {
        strBoundType = "outbound"
    }
    var strConnectType string
    if atomic.LoadInt32(&p.disconnect) == 0 {
        strConnectType = "connected"
    } else {
        strConnectType = "disconnected"
    }

    return fmt.Sprintf("[%s] (%s) %v %s [%s]", strConnectType, strBoundType, p.conn.RemoteAddr(), p.version, p.caps)

}

func (p *Peer) RlpData() []interface{} {
    return []interface{}{p.host, p.port, p.pubkey}
}

func packAddr(address, _port string) (host []byte, port uint16) {
    p, _ := strconv.Atoi(_port)
    port = uint16(p)

    h := net.ParseIP(address)
    if ip := h.To4(); ip != nil {
        host = []byte(ip)
    } else {
        host = []byte(h)
    }

    return
}

func unpackAddr(value *ethutil.Value, p uint64) string {
    host, _ := net.IP(value.Bytes()).MarshalText()
    prt := strconv.Itoa(int(p))

    return net.JoinHostPort(string(host), prt)
}