func (self *HikarianIcmp) Run() {
	if self.mode == "decrypt" {
		clientConn, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
		if err != nil {
			log.Fatal(err)
		}
		defer clientConn.Close()
		for {
			buf := make([]byte, 1024)
			nr, caddr, err := clientConn.ReadFrom(buf)
			request, err := icmp.ParseMessage(ProtocolICMP, buf)
			if err != nil {
				log.Println("parse icmp request error: ", err.Error())
				return
			}
			if request.Code == 0 {
				return
			}

			body, err := request.Body.Marshal(ProtocolICMP)
			if err != nil {
				log.Println("marshal body error: ", err.Error())
				continue
			}
			hash := binary.BigEndian.Uint16(body[0:2]) + binary.BigEndian.Uint16(body[2:4])
			dataChannel := self.DataChannelPool.Get(hash)
			if dataChannel == nil {
				dataChannel = make(chan []byte)
				self.DataChannelPool.Set(hash, dataChannel)
				go self.transportServer(clientConn, caddr, dataChannel)
			}
			if request.Code == MagicCode {
				log.Println("receive magic")
				dataChannel <- body[:nr-4]
			}
		}
	} else if self.mode == "encrypt" {
		client, err := net.ResolveTCPAddr("tcp", self.client)
		if err != nil {
			log.Fatalln("resolve client address error: ", err.Error())
		}
		l, err := net.ListenTCP("tcp", client)
		if err != nil {
			log.Fatal(err)
		}
		defer l.Close()
		for {
			clientConn, err := l.AcceptTCP()
			if err != nil {
				log.Println("accept error: ", err.Error())
				continue
			}
			defer clientConn.Close()
			go self.transportClient(clientConn)
		}
	}
}

// Monitor clients going in/out of sleep mode via ICMP unreachable packets.
func sleepMonitor() {
	c, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
	if err != nil {
		log.Printf("error listening for udp - sending data to all ports for all connected clients. err: %s", err)
		return
	}
	go icmpEchoSender(c)
	defer c.Close()
	for {
		buf := make([]byte, 1500)
		n, peer, err := c.ReadFrom(buf)
		if err != nil {
			log.Printf("%s\n", err.Error())
			continue
		}
		msg, err := icmp.ParseMessage(1, buf[:n])
		if err != nil {
			continue
		}

		ip := peer.String()

		// Look for echo replies, mark it as received.
		if msg.Type == ipv4.ICMPTypeEchoReply {
			pingResponse[ip] = stratuxClock.Time
			continue // No further processing needed.
		}

		// Only deal with ICMP Unreachable packets (since that's what iOS and Android seem to be sending whenever the apps are not available).
		if msg.Type != ipv4.ICMPTypeDestinationUnreachable {
			continue
		}
		// Packet parsing.
		mb, err := msg.Body.Marshal(1)
		if err != nil {
			continue
		}
		if len(mb) < 28 {
			continue
		}

		// The unreachable port.
		port := (uint16(mb[26]) << 8) | uint16(mb[27])
		ipAndPort := ip + ":" + strconv.Itoa(int(port))

		netMutex.Lock()
		p, ok := outSockets[ipAndPort]
		if !ok {
			// Can't do anything, the client isn't even technically connected.
			netMutex.Unlock()
			continue
		}
		p.LastUnreachable = stratuxClock.Time
		outSockets[ipAndPort] = p
		netMutex.Unlock()
	}
}

func (p *Pinger) processPacket(recv *packet) error {
	var bytes []byte
	var proto int
	if p.ipv4 {
		if p.network == "ip" {
			bytes = ipv4Payload(recv.bytes)
		} else {
			bytes = recv.bytes
		}
		proto = protocolICMP
	} else {
		bytes = recv.bytes
		proto = protocolIPv6ICMP
	}

	var m *icmp.Message
	var err error
	if m, err = icmp.ParseMessage(proto, bytes[:recv.nbytes]); err != nil {
		return fmt.Errorf("Error parsing icmp message")
	}

	if m.Type != ipv4.ICMPTypeEchoReply && m.Type != ipv6.ICMPTypeEchoReply {
		// Not an echo reply, ignore it
		return nil
	}

	outPkt := &Packet{
		Nbytes: recv.nbytes,
		IPAddr: p.ipaddr,
	}

	switch pkt := m.Body.(type) {
	case *icmp.Echo:
		outPkt.Rtt = time.Since(bytesToTime(pkt.Data[:timeSliceLength]))
		outPkt.Seq = pkt.Seq
		p.PacketsRecv += 1
	default:
		// Very bad, not sure how this can happen
		return fmt.Errorf("Error, invalid ICMP echo reply. Body type: %T, %s",
			pkt, pkt)
	}

	p.rtts = append(p.rtts, outPkt.Rtt)
	handler := p.OnRecv
	if handler != nil {
		handler(outPkt)
	}

	return nil
}

func main() {
	timeout := 5
	t1 := time.Now()
	c, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
	if err != nil {
		checkError(err, "listen err, ")
	}
	c.SetDeadline(t1.Add(time.Second * time.Duration(timeout)))
	defer c.Close()

	wm := icmp.Message{
		Type: ipv4.ICMPTypeEcho, Code: 0,
		Body: &icmp.Echo{
			ID: os.Getpid() & 0xffff, Seq: 1,
			Data: []byte("HELLO-R-U-THERE"),
		},
	}
	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Fatal(err)
	}
	// Send ICMP echo and start timer
	starttime := time.Now()
	if _, err := c.WriteTo(wb, &net.IPAddr{IP: net.ParseIP(targetIP)}); err != nil {
		log.Fatalf("WriteTo err, %s", err)
	}

	rb := make([]byte, 1500)
	// Look for ICMP response and stop time
	n, peer, err := c.ReadFrom(rb)
	stoptime := time.Now()
	if err != nil {
		log.Fatal(err)
	}
	//rm, err := icmp.ParseMessage(iana.ProtocolICMP, rb[:n])
	rm, err := icmp.ParseMessage(1, rb[:n])
	if err != nil {
		log.Fatal(err)
	}
	switch rm.Type {
	case ipv4.ICMPTypeEchoReply:
		log.Printf("got reflection from %v", peer)
		log.Printf("ICMP echo request sent on ", starttime)
		log.Printf("ICMP echo response received on ", stoptime)
	default:
		log.Printf("got %+v; want echo reply", rm)
	}
}

func ping(listener *icmp.PacketConn, message icmp.Message, raddr net.Addr, timeout time.Duration) (Pong, error) {
	data, err := message.Marshal(nil)
	if err != nil {
		return Pong{}, err
	}
	_, err = listener.WriteTo(data, raddr)
	if err != nil {
		return Pong{}, err
	}
	now := time.Now()
	done := make(chan Pong)
	go func() {
		for {
			buf := make([]byte, 10000)
			// bufio
			n, peer, err := listener.ReadFrom(buf)
			if err != nil {
				return
			}
			since := time.Since(now)
			input, err := icmp.ParseMessage(protocolICMP, buf[:n])
			if err != nil {
				return
			}
			if input.Type != ipv4.ICMPTypeEchoReply {
				continue
			}
			echo := input.Body.(*icmp.Echo)
			pong := Pong{
				Peer: peer,
				ID:   echo.ID,
				Seq:  echo.Seq,
				Data: echo.Data,
				Size: n,
				RTT:  since,
			}
			done <- pong
			return
		}
	}()
	select {
	case pong := <-done:
		return pong, nil
	case <-time.After(timeout):
		return Pong{}, errors.New("Timeout")
	}
}

func ExamplePacketConn_nonPrivilegedPing() {
	switch runtime.GOOS {
	case "darwin":
	case "linux":
		log.Println("you may need to adjust the net.ipv4.ping_group_range kernel state")
	default:
		log.Println("not supported on", runtime.GOOS)
		return
	}

	c, err := icmp.ListenPacket("udp6", "fe80::1%en0")
	if err != nil {
		log.Fatal(err)
	}
	defer c.Close()

	wm := icmp.Message{
		Type: ipv6.ICMPTypeEchoRequest, Code: 0,
		Body: &icmp.Echo{
			ID: os.Getpid() & 0xffff, Seq: 1,
			Data: []byte("HELLO-R-U-THERE"),
		},
	}
	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Fatal(err)
	}
	if _, err := c.WriteTo(wb, &net.UDPAddr{IP: net.ParseIP("ff02::1"), Zone: "en0"}); err != nil {
		log.Fatal(err)
	}

	rb := make([]byte, 1500)
	n, peer, err := c.ReadFrom(rb)
	if err != nil {
		log.Fatal(err)
	}
	rm, err := icmp.ParseMessage(58, rb[:n])
	if err != nil {
		log.Fatal(err)
	}
	switch rm.Type {
	case ipv6.ICMPTypeEchoReply:
		log.Printf("got reflection from %v", peer)
	default:
		log.Printf("got %+v; want echo reply", rm)
	}
}

// This checks if we can convert an URL to an IP
func testDNS(pr *pingResponse, pi pingInfo, conn *icmp.PacketConn) {
	start := time.Now()
	msg := createMessage()

	msg_bytes, err := msg.Marshal(nil)
	if err != nil {
		emsg := "Could not marshal the message to []byte."
		logger.WriteString(emsg)
		pr.err = errors.New(emsg)
		return
	}

	ip, _ := net.LookupHost(pi.externalurl)

	if _, err := conn.WriteTo(msg_bytes, &net.UDPAddr{IP: net.ParseIP(ip[0]), Zone: "en0"}); err != nil {
		emsg := "Could not write to the internal ip address: " + ip[0]
		logger.WriteString(emsg)
		pr.external_url = false
		pr.err = errors.New(emsg)
		return
	}

	pr.external_url = true

	response := make([]byte, 1500)
	count, peer, err := conn.ReadFrom(response)
	if err != nil {
		emsg := "Could not read the response."
		logger.WriteString(emsg)
		pr.external_url = false
		pr.err = errors.New(emsg)
		return
	}

	_, err = icmp.ParseMessage(protocolICMP, response[:count])
	if err != nil {
		emsg := "Could not parse the message received."
		logger.WriteString(emsg)
		pr.external_url = false
		pr.err = errors.New(emsg)
		return
	}

	logger.WriteString("Response " + strconv.Itoa(sequence) + " received from " + peer.String() +
		" after " + time.Now().Sub(start).String())
}

func TestMarshalAndParseMessageForIPv4(t *testing.T) {
	for i, tt := range marshalAndParseMessageForIPv4Tests {
		b, err := tt.Marshal(nil)
		if err != nil {
			t.Fatal(err)
		}
		m, err := icmp.ParseMessage(iana.ProtocolICMP, b)
		if err != nil {
			t.Fatal(err)
		}
		if m.Type != tt.Type || m.Code != tt.Code {
			t.Errorf("#%v: got %v; want %v", i, m, &tt)
		}
		if !reflect.DeepEqual(m.Body, tt.Body) {
			t.Errorf("#%v: got %v; want %v", i, m.Body, tt.Body)
		}
	}
}

func TestMarshalAndParseMultipartMessageForIPv4(t *testing.T) {
	for i, tt := range marshalAndParseMultipartMessageForIPv4Tests {
		b, err := tt.Marshal(nil)
		if err != nil {
			t.Fatal(err)
		}
		if b[5] != 32 {
			t.Errorf("#%v: got %v; want 32", i, b[5])
		}
		m, err := icmp.ParseMessage(iana.ProtocolICMP, b)
		if err != nil {
			t.Fatal(err)
		}
		if m.Type != tt.Type || m.Code != tt.Code {
			t.Errorf("#%v: got %v; want %v", i, m, &tt)
		}
		switch m.Type {
		case ipv4.ICMPTypeDestinationUnreachable:
			got, want := m.Body.(*icmp.DstUnreach), tt.Body.(*icmp.DstUnreach)
			if !reflect.DeepEqual(got.Extensions, want.Extensions) {
				t.Error(dumpExtensions(i, got.Extensions, want.Extensions))
			}
			if len(got.Data) != 128 {
				t.Errorf("#%v: got %v; want 128", i, len(got.Data))
			}
		case ipv4.ICMPTypeTimeExceeded:
			got, want := m.Body.(*icmp.TimeExceeded), tt.Body.(*icmp.TimeExceeded)
			if !reflect.DeepEqual(got.Extensions, want.Extensions) {
				t.Error(dumpExtensions(i, got.Extensions, want.Extensions))
			}
			if len(got.Data) != 128 {
				t.Errorf("#%v: got %v; want 128", i, len(got.Data))
			}
		case ipv4.ICMPTypeParameterProblem:
			got, want := m.Body.(*icmp.ParamProb), tt.Body.(*icmp.ParamProb)
			if !reflect.DeepEqual(got.Extensions, want.Extensions) {
				t.Error(dumpExtensions(i, got.Extensions, want.Extensions))
			}
			if len(got.Data) != 128 {
				t.Errorf("#%v: got %v; want 128", i, len(got.Data))
			}
		}
	}
}

func (i *ICMP) Read() ([]byte, error) {
	buf := make([]byte, 10000)
	n, _, err := i.listener.ReadFrom(buf)
	if err != nil {
		return nil, err
	}
	input, err := icmp.ParseMessage(_PROTOCOL_ICMP, buf[:n])
	if err != nil {
		return nil, err
	}
	if input.Type != ipv4.ICMPTypeEchoReply {
		return nil, nil
	}
	echo, ok := input.Body.(*icmp.Echo)
	if !ok {
		return nil, nil
	}
	return echo.Data, nil
}

func TestMarshalAndParseMessageForIPv6(t *testing.T) {
	pshicmp := icmp.IPv6PseudoHeader(net.ParseIP("fe80::1"), net.ParseIP("ff02::1"))
	for i, tt := range marshalAndParseMessageForIPv6Tests {
		for _, psh := range [][]byte{pshicmp, nil} {
			b, err := tt.Marshal(psh)
			if err != nil {
				t.Fatal(err)
			}
			m, err := icmp.ParseMessage(iana.ProtocolIPv6ICMP, b)
			if err != nil {
				t.Fatal(err)
			}
			if m.Type != tt.Type || m.Code != tt.Code {
				t.Errorf("#%v: got %v; want %v", i, m, &tt)
			}
			if !reflect.DeepEqual(m.Body, tt.Body) {
				t.Errorf("#%v: got %v; want %v", i, m.Body, tt.Body)
			}
		}
	}
}

func TestMarshalAndParseMultipartMessageForIPv6(t *testing.T) {
	pshicmp := icmp.IPv6PseudoHeader(net.ParseIP("fe80::1"), net.ParseIP("ff02::1"))
	for i, tt := range marshalAndParseMultipartMessageForIPv6Tests {
		for _, psh := range [][]byte{pshicmp, nil} {
			b, err := tt.Marshal(psh)
			if err != nil {
				t.Fatal(err)
			}
			if b[4] != 16 {
				t.Errorf("#%v: got %v; want 16", i, b[4])
			}
			m, err := icmp.ParseMessage(iana.ProtocolIPv6ICMP, b)
			if err != nil {
				t.Fatal(err)
			}
			if m.Type != tt.Type || m.Code != tt.Code {
				t.Errorf("#%v: got %v; want %v", i, m, &tt)
			}
			switch m.Type {
			case ipv6.ICMPTypeDestinationUnreachable:
				got, want := m.Body.(*icmp.DstUnreach), tt.Body.(*icmp.DstUnreach)
				if !reflect.DeepEqual(got.Extensions, want.Extensions) {
					t.Error(dumpExtensions(i, got.Extensions, want.Extensions))
				}
				if len(got.Data) != 128 {
					t.Errorf("#%v: got %v; want 128", i, len(got.Data))
				}
			case ipv6.ICMPTypeTimeExceeded:
				got, want := m.Body.(*icmp.TimeExceeded), tt.Body.(*icmp.TimeExceeded)
				if !reflect.DeepEqual(got.Extensions, want.Extensions) {
					t.Error(dumpExtensions(i, got.Extensions, want.Extensions))
				}
				if len(got.Data) != 128 {
					t.Errorf("#%v: got %v; want 128", i, len(got.Data))
				}
			}
		}
	}
}

func ExamplePacketConn_nonPrivilegedPing() {
	c, err := icmp.ListenPacket("udp6", "fe80::1%en0")
	if err != nil {
		log.Fatal(err)
	}
	defer c.Close()

	wm := icmp.Message{
		Type: ipv6.ICMPTypeEchoRequest, Code: 0,
		Body: &icmp.Echo{
			ID: os.Getpid() & 0xffff, Seq: 1,
			Data: []byte("HELLO-R-U-THERE"),
		},
	}
	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Fatal(err)
	}
	if _, err := c.WriteTo(wb, &net.UDPAddr{IP: net.ParseIP("ff02::1"), Zone: "en0"}); err != nil {
		log.Fatal(err)
	}

	rb := make([]byte, 1500)
	n, peer, err := c.ReadFrom(rb)
	if err != nil {
		log.Fatal(err)
	}
	rm, err := icmp.ParseMessage(iana.ProtocolIPv6ICMP, rb[:n])
	if err != nil {
		log.Fatal(err)
	}
	switch rm.Type {
	case ipv6.ICMPTypeEchoReply:
		log.Printf("got reflection from %v", peer)
	default:
		log.Printf("got %+v; want echo reply", rm)
	}
}

func (p *Ping) parseMessage(r Reply, ssmap map[int]int64) bool {

	stop := time.Now().UnixNano()

	rep, err := icmp.ParseMessage(iana.ProtocolICMP, r.bytes)
	if err != nil {
		fmt.Printf("* Reply error from %s: icmp_seq=%d -> %s\n", r.addr, p.sends, r.bytes)
		return false
	}

	var seq int
	switch pkt := rep.Body.(type) {
	case *icmp.Echo:
		if !(pkt.ID == p.id && pkt.Seq <= p.sends && bytes.Equal(pkt.Data, p.data)) {
			fmt.Printf("* Wrong data %d bytes from %s (ID=[%d,%d], Seq=[%d,%d]): icmp_seq=%d\n",
				r.size, r.addr, pkt.ID, p.id, pkt.Seq, p.sends, p.sends)
			return false
		}
		seq = pkt.Seq
	default:
		fmt.Printf("* Not echo received from %s: icmp_seq=%d\n", r.size, r.addr, p.sends)
		return false
	}

	if v, ok := ssmap[seq]; !ok {
		fmt.Printf("* Duplicated packet received from %s: icmp_seq=%d\n", r.addr, p.sends)
		return false
	} else {
		rtt := stop - v
		delete(ssmap, seq)
		fmt.Printf("%d bytes from %s: icmp_seq=%d time=%.2f ms\n",
			r.size, r.addr, p.sends, float64(rtt)/float64(time.Millisecond))
	}

	return true
}

func (p *Pinger) procRecv(bytes []byte, ra net.Addr, ctx *context) {
	var ipaddr *net.IPAddr
	switch adr := ra.(type) {
	case *net.IPAddr:
		ipaddr = adr
	case *net.UDPAddr:
		ipaddr = &net.IPAddr{IP: adr.IP, Zone: adr.Zone}
	default:
		return
	}

	addr := ipaddr.String()
	p.mu.Lock()
	_, ok := p.addrs[addr]
	p.mu.Unlock()

	if !ok {
		return
	}

	var proto int
	if isIPv4(ipaddr.IP) {
		if p.network == "ip" {
			bytes = ipv4Payload(bytes)
		}
		proto = ProtocolICMP
	} else if isIPv6(ipaddr.IP) {
		proto = ProtocolIPv6ICMP
	} else {
		return
	}

	var m *icmp.Message
	var err error
	if m, err = icmp.ParseMessage(proto, bytes); err != nil {
		return
	}

	if m.Type != ipv4.ICMPTypeEchoReply && m.Type != ipv6.ICMPTypeEchoReply {
		return
	}

	var rtt time.Duration
	switch pkt := m.Body.(type) {
	case *icmp.Echo:
		if pkt.ID == p.id && pkt.Seq == p.seq {
			rtt = time.Since(bytesToTime(pkt.Data[:TimeSliceLength]))
		}
	default:
		return
	}

	if 0 == rtt {
		return
	}

	p.mu.Lock()
	delete(p.sent, addr)
	if len(p.sent) == 0 && !p.done {
		p.done = true
		close(ctx.done)
	}
	p.mu.Unlock()

	if p.OnRecv != nil {
		p.OnRecv(ipaddr, rtt)
	}
}

// pingIcmp performs a ping to a destination. It select between ipv4 or ipv6 ping based
// on the format of the destination ip.
func (r Runner) pingIcmp() (err error) {
	var (
		icmpType icmp.Type
		network  string
	)

	if strings.Contains(r.Parameters.Destination, ":") {
		network = "ip6:ipv6-icmp"
		icmpType = ipv6.ICMPTypeEchoRequest
	} else {
		network = "ip4:icmp"
		icmpType = ipv4.ICMPTypeEcho
	}

	c, err := net.Dial(network, r.Parameters.Destination)
	if err != nil {
		return fmt.Errorf("Dial failed: %v", err)
	}
	c.SetDeadline(time.Now().Add(time.Duration(r.Parameters.Timeout) * time.Second))
	defer c.Close()

	// xid is the process ID.
	// Get process ID and make sure it fits in 16bits.
	xid := os.Getpid() & 0xffff
	// Sequence number of the packet.
	xseq := 0
	packet := icmp.Message{
		Type: icmpType, // Type of icmp message
		Code: 0,        // icmp query messages use code 0
		Body: &icmp.Echo{
			ID:   xid,  // Packet id
			Seq:  xseq, // Sequence number of the packet
			Data: bytes.Repeat([]byte("Ping!Ping!Ping!"), 3),
		},
	}

	wb, err := packet.Marshal(nil)

	if err != nil {
		return fmt.Errorf("Connection failed: %v", err)
	}

	if _, err := c.Write(wb); err != nil {
		return fmt.Errorf("Conn.Write Error: %v", err)
	}

	rb := make([]byte, 1500)

	if _, err := c.Read(rb); err != nil {
		// If connection timed out, we return E_Timeout
		if e := err.(*net.OpError).Timeout(); e {
			return fmt.Errorf(E_Timeout)
		}
		if strings.Contains(err.Error(), "connection refused") {
			return fmt.Errorf(E_ConnRefused)
		}
		return fmt.Errorf("Conn.Read failed: %v", err)
	}

	_, err = icmp.ParseMessage(icmpType.Protocol(), rb)
	if err != nil {
		return fmt.Errorf("ParseICMPMessage failed: %v", err)
	}

	return
}

func TestPacketConnReadWriteUnicastICMP(t *testing.T) {
	switch runtime.GOOS {
	case "nacl", "plan9", "windows":
		t.Skipf("not supported on %s", runtime.GOOS)
	}
	if m, ok := nettest.SupportsRawIPSocket(); !ok {
		t.Skip(m)
	}
	ifi := nettest.RoutedInterface("ip4", net.FlagUp|net.FlagLoopback)
	if ifi == nil {
		t.Skipf("not available on %s", runtime.GOOS)
	}

	c, err := net.ListenPacket("ip4:icmp", "0.0.0.0")
	if err != nil {
		t.Fatal(err)
	}
	defer c.Close()

	dst, err := net.ResolveIPAddr("ip4", "127.0.0.1")
	if err != nil {
		t.Fatal(err)
	}
	p := ipv4.NewPacketConn(c)
	defer p.Close()
	cf := ipv4.FlagDst | ipv4.FlagInterface
	if runtime.GOOS != "solaris" {
		// Solaris never allows to modify ICMP properties.
		cf |= ipv4.FlagTTL
	}

	for i, toggle := range []bool{true, false, true} {
		wb, err := (&icmp.Message{
			Type: ipv4.ICMPTypeEcho, Code: 0,
			Body: &icmp.Echo{
				ID: os.Getpid() & 0xffff, Seq: i + 1,
				Data: []byte("HELLO-R-U-THERE"),
			},
		}).Marshal(nil)
		if err != nil {
			t.Fatal(err)
		}
		if err := p.SetControlMessage(cf, toggle); err != nil {
			if nettest.ProtocolNotSupported(err) {
				t.Logf("not supported on %s", runtime.GOOS)
				continue
			}
			t.Fatal(err)
		}
		p.SetTTL(i + 1)
		if err := p.SetWriteDeadline(time.Now().Add(100 * time.Millisecond)); err != nil {
			t.Fatal(err)
		}
		if n, err := p.WriteTo(wb, nil, dst); err != nil {
			t.Fatal(err)
		} else if n != len(wb) {
			t.Fatalf("got %v; want %v", n, len(wb))
		}
		rb := make([]byte, 128)
	loop:
		if err := p.SetReadDeadline(time.Now().Add(100 * time.Millisecond)); err != nil {
			t.Fatal(err)
		}
		if n, _, _, err := p.ReadFrom(rb); err != nil {
			switch runtime.GOOS {
			case "darwin": // older darwin kernels have some limitation on receiving icmp packet through raw socket
				t.Logf("not supported on %s", runtime.GOOS)
				continue
			}
			t.Fatal(err)
		} else {
			m, err := icmp.ParseMessage(iana.ProtocolICMP, rb[:n])
			if err != nil {
				t.Fatal(err)
			}
			if runtime.GOOS == "linux" && m.Type == ipv4.ICMPTypeEcho {
				// On Linux we must handle own sent packets.
				goto loop
			}
			if m.Type != ipv4.ICMPTypeEchoReply || m.Code != 0 {
				t.Fatalf("got type=%v, code=%v; want type=%v, code=%v", m.Type, m.Code, ipv4.ICMPTypeEchoReply, 0)
			}
		}
	}
}

func TestRawConnReadWriteUnicastICMP(t *testing.T) {
	switch runtime.GOOS {
	case "nacl", "plan9", "windows":
		t.Skipf("not supported on %s", runtime.GOOS)
	}
	if m, ok := nettest.SupportsRawIPSocket(); !ok {
		t.Skip(m)
	}
	ifi := nettest.RoutedInterface("ip4", net.FlagUp|net.FlagLoopback)
	if ifi == nil {
		t.Skipf("not available on %s", runtime.GOOS)
	}

	c, err := net.ListenPacket("ip4:icmp", "0.0.0.0")
	if err != nil {
		t.Fatal(err)
	}
	defer c.Close()

	dst, err := net.ResolveIPAddr("ip4", "127.0.0.1")
	if err != nil {
		t.Fatal(err)
	}
	r, err := ipv4.NewRawConn(c)
	if err != nil {
		t.Fatal(err)
	}
	defer r.Close()
	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface

	for i, toggle := range []bool{true, false, true} {
		wb, err := (&icmp.Message{
			Type: ipv4.ICMPTypeEcho, Code: 0,
			Body: &icmp.Echo{
				ID: os.Getpid() & 0xffff, Seq: i + 1,
				Data: []byte("HELLO-R-U-THERE"),
			},
		}).Marshal(nil)
		if err != nil {
			t.Fatal(err)
		}
		wh := &ipv4.Header{
			Version:  ipv4.Version,
			Len:      ipv4.HeaderLen,
			TOS:      i + 1,
			TotalLen: ipv4.HeaderLen + len(wb),
			TTL:      i + 1,
			Protocol: 1,
			Dst:      dst.IP,
		}
		if err := r.SetControlMessage(cf, toggle); err != nil {
			if nettest.ProtocolNotSupported(err) {
				t.Logf("not supported on %s", runtime.GOOS)
				continue
			}
			t.Fatal(err)
		}
		if err := r.SetWriteDeadline(time.Now().Add(100 * time.Millisecond)); err != nil {
			t.Fatal(err)
		}
		if err := r.WriteTo(wh, wb, nil); err != nil {
			t.Fatal(err)
		}
		rb := make([]byte, ipv4.HeaderLen+128)
	loop:
		if err := r.SetReadDeadline(time.Now().Add(100 * time.Millisecond)); err != nil {
			t.Fatal(err)
		}
		if _, b, _, err := r.ReadFrom(rb); err != nil {
			switch runtime.GOOS {
			case "darwin": // older darwin kernels have some limitation on receiving icmp packet through raw socket
				t.Logf("not supported on %s", runtime.GOOS)
				continue
			}
			t.Fatal(err)
		} else {
			m, err := icmp.ParseMessage(iana.ProtocolICMP, b)
			if err != nil {
				t.Fatal(err)
			}
			if runtime.GOOS == "linux" && m.Type == ipv4.ICMPTypeEcho {
				// On Linux we must handle own sent packets.
				goto loop
			}
			if m.Type != ipv4.ICMPTypeEchoReply || m.Code != 0 {
				t.Fatalf("got type=%v, code=%v; want type=%v, code=%v", m.Type, m.Code, ipv4.ICMPTypeEchoReply, 0)
			}
		}
	}
}

func ExamplePacketConn_tracingIPPacketRoute() {
	// Tracing an IP packet route to www.google.com.

	const host = "www.google.com"
	ips, err := net.LookupIP(host)
	if err != nil {
		log.Fatal(err)
	}
	var dst net.IPAddr
	for _, ip := range ips {
		if ip.To4() != nil {
			dst.IP = ip
			fmt.Printf("using %v for tracing an IP packet route to %s\n", dst.IP, host)
			break
		}
	}
	if dst.IP == nil {
		log.Fatal("no A record found")
	}

	c, err := net.ListenPacket(fmt.Sprintf("ip4:%d", iana.ProtocolICMP), "0.0.0.0") // ICMP for IPv4
	if err != nil {
		log.Fatal(err)
	}
	defer c.Close()
	p := ipv4.NewPacketConn(c)

	if err := p.SetControlMessage(ipv4.FlagTTL|ipv4.FlagSrc|ipv4.FlagDst|ipv4.FlagInterface, true); err != nil {
		log.Fatal(err)
	}
	wm := icmp.Message{
		Type: ipv4.ICMPTypeEcho, Code: 0,
		Body: &icmp.Echo{
			ID:   os.Getpid() & 0xffff,
			Data: []byte("HELLO-R-U-THERE"),
		},
	}

	rb := make([]byte, 1500)
	for i := 1; i <= 64; i++ { // up to 64 hops
		wm.Body.(*icmp.Echo).Seq = i
		wb, err := wm.Marshal(nil)
		if err != nil {
			log.Fatal(err)
		}
		if err := p.SetTTL(i); err != nil {
			log.Fatal(err)
		}

		// In the real world usually there are several
		// multiple traffic-engineered paths for each hop.
		// You may need to probe a few times to each hop.
		begin := time.Now()
		if _, err := p.WriteTo(wb, nil, &dst); err != nil {
			log.Fatal(err)
		}
		if err := p.SetReadDeadline(time.Now().Add(3 * time.Second)); err != nil {
			log.Fatal(err)
		}
		n, cm, peer, err := p.ReadFrom(rb)
		if err != nil {
			if err, ok := err.(net.Error); ok && err.Timeout() {
				fmt.Printf("%v\t*\n", i)
				continue
			}
			log.Fatal(err)
		}
		rm, err := icmp.ParseMessage(iana.ProtocolICMP, rb[:n])
		if err != nil {
			log.Fatal(err)
		}
		rtt := time.Since(begin)

		// In the real world you need to determine whether the
		// received message is yours using ControlMessage.Src,
		// ControlMessage.Dst, icmp.Echo.ID and icmp.Echo.Seq.
		switch rm.Type {
		case ipv4.ICMPTypeTimeExceeded:
			names, _ := net.LookupAddr(peer.String())
			fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm)
		case ipv4.ICMPTypeEchoReply:
			names, _ := net.LookupAddr(peer.String())
			fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm)
			return
		default:
			log.Printf("unknown ICMP message: %+v\n", rm)
		}
	}
}

func (p *Pinger) procRecv(recv *packet, queue map[string]*net.IPAddr) {
	var ipaddr *net.IPAddr
	switch adr := recv.addr.(type) {
	case *net.IPAddr:
		ipaddr = adr
	case *net.UDPAddr:
		ipaddr = &net.IPAddr{IP: adr.IP, Zone: adr.Zone}
	default:
		return
	}

	addr := ipaddr.String()
	p.mu.Lock()
	if _, ok := p.addrs[addr]; !ok {
		p.mu.Unlock()
		return
	}
	p.mu.Unlock()

	var bytes []byte
	var proto int
	if isIPv4(ipaddr.IP) {
		if p.network == "ip" {
			bytes = ipv4Payload(recv.bytes)
		} else {
			bytes = recv.bytes
		}
		proto = ProtocolICMP
	} else if isIPv6(ipaddr.IP) {
		bytes = recv.bytes
		proto = ProtocolIPv6ICMP
	} else {
		return
	}

	var m *icmp.Message
	var err error
	if m, err = icmp.ParseMessage(proto, bytes); err != nil {
		return
	}

	if m.Type != ipv4.ICMPTypeEchoReply && m.Type != ipv6.ICMPTypeEchoReply {
		return
	}

	var rtt time.Duration
	switch pkt := m.Body.(type) {
	case *icmp.Echo:
		p.mu.Lock()
		if pkt.ID == p.id && pkt.Seq == p.seq {
			rtt = time.Since(bytesToTime(pkt.Data[:TimeSliceLength]))
		}
		p.mu.Unlock()
	default:
		return
	}

	if _, ok := queue[addr]; ok {
		delete(queue, addr)
		p.mu.Lock()
		handler := p.OnRecv
		p.mu.Unlock()
		if handler != nil {
			handler(ipaddr, rtt)
		}
	}
}