func icmpEchoSender(c *icmp.PacketConn) {
	timer := time.NewTicker(5 * time.Second)
	for {
		<-timer.C
		// Collect IPs.
		ips := make(map[string]bool)
		for k, _ := range outSockets {
			ipAndPort := strings.Split(k, ":")
			ips[ipAndPort[0]] = true
		}
		// Send to all IPs.
		for ip, _ := range ips {
			wm := icmp.Message{
				Type: ipv4.ICMPTypeEcho, Code: 0,
				Body: &icmp.Echo{
					ID: os.Getpid() & 0xffff, Seq: 1,
					Data: []byte("STRATUX"),
				},
			}
			wb, err := wm.Marshal(nil)
			if err != nil {
				log.Printf("couldn't send ICMP Echo: %s\n", err.Error())
				continue
			}
			if _, err := c.WriteTo(wb, &net.IPAddr{IP: net.ParseIP(ip)}); err != nil {
				log.Printf("couldn't send ICMP Echo: %s\n", err.Error())
				continue
			}
			totalNetworkMessagesSent++
		}
	}
}

func (e *EchoRequest) Send() {
	for i := 0; i < e.Count; i++ {
		pkt := icmp.Message{
			Type: ipv4.ICMPTypeEcho,
			Code: 0,
			Body: &icmp.Echo{
				ID:   e.Id,
				Seq:  i,
				Data: []byte("raintank/go-pinger"),
			},
		}
		wb, err := pkt.Marshal(nil)
		if err != nil {
			if e.pinger.Debug {
				log.Printf("failed to marshal ICMP Echo packet. %s", err)
			}
			continue
		}
		sentTime, err := e.pinger.WritePkt(wb, e.Peer)
		if err == nil {
			e.Stats.Sent++
			e.Stats.SentTime[i] = sentTime
			if e.pinger.Debug {
				log.Printf("go-pinger: sent pkt. Peer %s, Id: %d, Seq: %d, Sent: %s", e.Peer, e.Id, i, sentTime)
			}
		}
	}
	e.Listen()
}

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)
	}
}

func (i *ICMP) Write(b []byte) error {
	message := icmp.Message{
		Type: ipv4.ICMPTypeEcho,
		Code: 0,
		Body: &icmp.Echo{
			Data: b,
		},
	}
	outgoing, err := message.Marshal(nil)
	if err != nil {
		return err
	}
	_, err = i.listener.WriteTo(outgoing, i.raddr)
	if err != nil {
		return err
	}
	return nil
}

func Send_UDP_Ping(c *icmp.PacketConn, targetIP string, concurrent int, timeout int, ch_lock chan struct{}, rCache *ResultCache) {
	ch_lock <- struct{}{}
	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 {
		return
	}
	timeForSend := time.Now()
	c.SetReadDeadline(timeForSend.Add(time.Duration(timeout) * time.Second))
	rCache.New(targetIP)
	if _, err := c.WriteTo(wb, &net.UDPAddr{IP: net.ParseIP(targetIP)}); err != nil {
		return
	}
	time.Sleep(time.Second)
	<-ch_lock
}

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)
	}
}

// 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 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 probeICMP(target string, w http.ResponseWriter, module Module) (success bool) {
	deadline := time.Now().Add(module.Timeout)
	socket, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
	if err != nil {
		log.Errorf("Error listening to socket: %s", err)
		return
	}
	defer socket.Close()

	ip, err := net.ResolveIPAddr("ip4", target)
	if err != nil {
		log.Errorf("Error resolving address %s: %s", target, err)
		return
	}

	seq := getICMPSequence()
	pid := os.Getpid() & 0xffff

	wm := icmp.Message{
		Type: ipv4.ICMPTypeEcho, Code: 0,
		Body: &icmp.Echo{
			ID: pid, Seq: int(seq),
			Data: []byte("Prometheus Blackbox Exporter"),
		},
	}
	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", target, err)
		return
	}
	if _, err := socket.WriteTo(wb, ip); err != nil {
		log.Errorf("Error writing to socker for %s: %s", target, err)
		return
	}

	rb := make([]byte, 1500)
	if err := socket.SetReadDeadline(deadline); err != nil {
		log.Errorf("Error setting socket deadline for %s: %s", target, err)
		return
	}
	for {
		n, peer, err := socket.ReadFrom(rb)
		if err != nil {
			if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
				log.Infof("Timeout reading from socket for %s: %s", target, err)
				return
			}
			log.Errorf("Error reading from socket for %s: %s", target, err)
			continue
		}
		if peer.String() != ip.String() {
			continue
		}
		rm, err := icmp.ParseMessage(iana.ProtocolICMP, rb[:n])
		if err != nil {
			log.Warnf("Error parsing ICMP message for %s: %s", target, err)
			continue
		}
		if rm.Type == ipv4.ICMPTypeEchoReply {
			// The ICMP package does not support unmarshalling
			// messages, so assume this is the right sequence number.
			success = true
			return
		}
	}
	return
}

func probeICMP(target string, w http.ResponseWriter, module Module) (success bool) {
	var (
		socket           *icmp.PacketConn
		requestType      icmp.Type
		replyType        icmp.Type
		fallbackProtocol string
	)

	deadline := time.Now().Add(module.Timeout)

	// Defaults to IPv4 to be compatible with older versions
	if module.ICMP.Protocol == "" {
		module.ICMP.Protocol = "icmp"
	}

	// In case of ICMP prefer IPv6 by default
	if module.ICMP.Protocol == "icmp" && module.ICMP.PreferredIpProtocol == "" {
		module.ICMP.PreferredIpProtocol = "ip6"
	}

	if module.ICMP.Protocol == "icmp4" {
		module.ICMP.PreferredIpProtocol = "ip4"
		fallbackProtocol = ""
	} else if module.ICMP.Protocol == "icmp6" {
		module.ICMP.PreferredIpProtocol = "ip6"
		fallbackProtocol = ""
	} else if module.ICMP.PreferredIpProtocol == "ip6" {
		fallbackProtocol = "ip4"
	} else {
		fallbackProtocol = "ip6"
	}

	ip, err := net.ResolveIPAddr(module.ICMP.PreferredIpProtocol, target)
	if err != nil && fallbackProtocol != "" {
		ip, err = net.ResolveIPAddr(fallbackProtocol, target)
	}
	if err != nil {
		log.Errorf("Error resolving address %s: %s", target, err)
	}

	if ip.IP.To4() == nil {
		requestType = ipv6.ICMPTypeEchoRequest
		replyType = ipv6.ICMPTypeEchoReply
		socket, err = icmp.ListenPacket("ip6:ipv6-icmp", "::")
		fmt.Fprintf(w, "probe_ip_protocol 6\n")
	} else {
		requestType = ipv4.ICMPTypeEcho
		replyType = ipv4.ICMPTypeEchoReply
		socket, err = icmp.ListenPacket("ip4:icmp", "0.0.0.0")
		fmt.Fprintf(w, "probe_ip_protocol 4\n")
	}

	if err != nil {
		log.Errorf("Error listening to socket: %s", err)
		return
	}
	defer socket.Close()

	if err != nil {
		log.Errorf("Error resolving address %s: %s", target, err)
		return
	}

	seq := getICMPSequence()
	pid := os.Getpid() & 0xffff

	wm := icmp.Message{
		Type: requestType,
		Code: 0,
		Body: &icmp.Echo{
			ID: pid, Seq: int(seq),
			Data: []byte("Prometheus Blackbox Exporter"),
		},
	}

	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", target, err)
		return
	}
	if _, err := socket.WriteTo(wb, ip); err != nil {
		log.Errorf("Error writing to socker for %s: %s", target, err)
		return
	}

	// Reply should be the same except for the message type.
	wm.Type = replyType
	wb, err = wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", target, err)
		return
	}

	rb := make([]byte, 1500)
	if err := socket.SetReadDeadline(deadline); err != nil {
		log.Errorf("Error setting socket deadline for %s: %s", target, err)
		return
	}
	for {
		n, peer, err := socket.ReadFrom(rb)
//.........这里部分代码省略.........

// Sends a single ICMP echo to an IP and returns success and latency information.
// Borrowed from BrianBrazil's blackbox exporter
func Ping(ip net.IP, maxRTT time.Duration) (success bool, latency time.Duration) {
	deadline := time.Now().Add(maxRTT)

	var socket *icmp.PacketConn
	var err error
	if isIPv4(ip) {
		socket, err = icmp.ListenPacket("ip4:icmp", "0.0.0.0")
	} else if isIPv6(ip) {
		socket, err = icmp.ListenPacket("ip6:ipv6-icmp", "::")
	} else {
		log.Errorln("IP did not match any known types?")
		return
	}

	if err != nil {
		log.Errorf("Error listening to socket: %s", err)
		return
	}
	defer socket.Close()

	seq := getICMPSequence()
	pid := os.Getpid() & 0xffff

	// Build the packet
	var wm icmp.Message
	if isIPv4(ip) {
		wm = icmp.Message{
			Type: ipv4.ICMPTypeEcho, Code: 0,
			Body: &icmp.Echo{
				ID: pid, Seq: int(seq),
				Data: []byte("poller_exporter"),
			},
		}
	} else if isIPv6(ip) {
		wm = icmp.Message{
			Type: ipv6.ICMPTypeEchoRequest, Code: 0,
			Body: &icmp.Echo{
				ID: pid, Seq: int(seq),
				Data: []byte("poller_exporter"),
			},
		}
	} else {
		log.Errorln("IP did not match any known types?")
		return
	}

	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", ip.String(), err)
		return
	}

	sendTime := time.Now()

	var dst *net.IPAddr
	dst = &net.IPAddr{IP: ip}

	if _, err := socket.WriteTo(wb, dst); err != nil {
		log.Errorf("Error writing to socket for %s: %s", ip.String(), err)
		return
	}

	// Reply should be the same except for the message type.
	if isIPv4(ip) {
		wm.Type = ipv4.ICMPTypeEchoReply
	} else if isIPv6(ip) {
		wm.Type = ipv6.ICMPTypeEchoReply
	} else {
		log.Errorln("IP did not match any known types?")
		return
	}

	wb, err = wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", ip.String(), err)
		return
	}

	rb := make([]byte, 1500)
	if err := socket.SetReadDeadline(deadline); err != nil {
		log.Errorf("Error setting socket deadline for %s: %s", ip.String(), err)
		return
	}
	for {
		n, peer, err := socket.ReadFrom(rb)
		if err != nil {
			if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
				log.Infof("Timeout reading from socket for %s: %s", ip.String(), err)
				return
			}
			log.Errorf("Error reading from socket for %s: %s", ip.String(), err)
			continue
		}
		if peer.String() != ip.String() {
			continue
		}
		if bytes.Compare(rb[:n], wb) == 0 {
			success = true
//.........这里部分代码省略.........

func doPing(host string, tt *Ping, seq int) error {
	c, err := icmp.ListenPacket(tt.network, tt.address)
	if err != nil {
		return err
	}
	defer c.Close()

	dst, err := getAddr(host, c, tt.protocol)
	if err != nil {
		return err
	}

	now := time.Now()
	today := now.Truncate(24*time.Hour).UnixNano() / 1000000
	transmitTime := uint32(now.UnixNano()/1000000 - today)
	wm := icmp.Message{
		Type: tt.mtype,
		Code: 0,
		Body: &Timestamp{
			ID: os.Getpid() & 0xffff, Seq: 1 << uint(seq),
			OriginTimestamp: transmitTime,
		},
	}

	wb, err := wm.Marshal(nil)
	if err != nil {
		return err
	}
	if n, err := c.WriteTo(wb, dst); err != nil {
		return err
	} else if n != len(wb) {
		return fmt.Errorf("got %v; want %v", n, len(wb))
	}

	rb := make([]byte, 1500)
	if err := c.SetReadDeadline(time.Now().Add(3 * time.Second)); err != nil {
		return err
	}
	n, peer, err := c.ReadFrom(rb)
	if err != nil {
		return err
	}
	receivedTime := time.Now().UnixNano()/1000000 - today
	rm, err := icmp.ParseMessage(tt.protocol, rb[:n])
	if err != nil {
		return err
	}
	switch rm.Type {
	case ipv4.ICMPTypeTimestampReply:
		b, _ := rm.Body.Marshal(iana.ProtocolICMP)
		ts, err := ParseTimestamp(b)
		if err != nil {
			fmt.Errorf("ParseTimestamp error: %s", err)
		}
		remoteReceiveTime := int64(ts.ReceiveTimestamp)
		rtt := int64(math.Abs(float64(remoteReceiveTime - int64(transmitTime) + receivedTime - int64(ts.TransmitTimestamp))))
		delta := rtt/2 + int64(transmitTime) - remoteReceiveTime
		w := new(tabwriter.Writer)
		w.Init(os.Stdout, 0, 4, 0, '\t', 0)
		fmt.Fprintf(w, "ICMP timestamp:\tOriginate=%d Receive=%d Transmit=%d\n", ts.OriginTimestamp, ts.ReceiveTimestamp, ts.TransmitTimestamp)
		fmt.Fprintf(w, "ICMP timestamp RTT:\ttsrtt=%d\n", rtt)
		fmt.Fprintf(w, "Time difference:\tdelta=%d\n", delta)
		w.Flush()
		return nil
	default:
		return fmt.Errorf("got %+v from %v; want echo reply", rm, peer)
	}
}

// Pinger pings requested address.
// It returns nil when IcmpEchoReplay is recived, error otherwishe.
func Pinger(address string, timeout time.Duration) (err error) {
	addr, err := net.ResolveIPAddr("ip", address)
	if err != nil {
		return err
	}

	network := "ip4:icmp"
	if addr.IP.To4() == nil {
		network = "ip6:ipv6-icmp"
	}

	c, err := icmp.ListenPacket(network, address)
	if err != nil {
		return err
	}
	defer func() {
		if cerr := c.Close(); cerr != nil && err == nil {
			err = cerr
		}
	}()

	wm := icmp.Message{
		Type: ipv4.ICMPTypeEcho, Code: 0,
		Body: &icmp.Echo{
			ID: os.Getpid() & 0xffff, Seq: 1,
			Data: []byte("ping"),
		},
	}

	if addr.IP.To4() == nil {
		wm.Type = ipv6.ICMPTypeEchoRequest
	}

	wb, err := wm.Marshal(nil)
	if err != nil {
		return err
	}

	if err := c.SetDeadline(time.Now().Add(timeout)); err != nil {
		return err
	}

	if _, err = c.WriteTo(wb, addr); err != nil {
		return err
	}

	rb := make([]byte, 1500)
	n, _, err := c.ReadFrom(rb)
	if err != nil {
		return err
	}

	rm, err := icmp.ParseMessage(ProtocolICMP, rb[:n])
	if err != nil {
		return err
	}

	if addr.IP.To4() == nil {
		if rm.Type == ipv6.ICMPTypeEchoReply {
			return ErrNoImcpReplay
		}
		return nil
	}

	if rm.Type == ipv4.ICMPTypeEchoReply {
		return ErrNoImcpReplay
	}
	return nil
}

func probeICMP(target string, w http.ResponseWriter, module Module) (success bool) {
	deadline := time.Now().Add(module.Timeout)
	socket, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
	if err != nil {
		log.Errorf("Error listening to socket: %s", err)
		return
	}
	defer socket.Close()

	ip, err := net.ResolveIPAddr("ip4", target)
	if err != nil {
		log.Errorf("Error resolving address %s: %s", target, err)
		return
	}

	seq := getICMPSequence()
	pid := os.Getpid() & 0xffff

	wm := icmp.Message{
		Type: ipv4.ICMPTypeEcho, Code: 0,
		Body: &icmp.Echo{
			ID: pid, Seq: int(seq),
			Data: []byte("Prometheus Blackbox Exporter"),
		},
	}
	wb, err := wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", target, err)
		return
	}
	if _, err := socket.WriteTo(wb, ip); err != nil {
		log.Errorf("Error writing to socker for %s: %s", target, err)
		return
	}

	// Reply should be the same except for the message type.
	wm.Type = ipv4.ICMPTypeEchoReply
	wb, err = wm.Marshal(nil)
	if err != nil {
		log.Errorf("Error marshalling packet for %s: %s", target, err)
		return
	}

	rb := make([]byte, 1500)
	if err := socket.SetReadDeadline(deadline); err != nil {
		log.Errorf("Error setting socket deadline for %s: %s", target, err)
		return
	}
	for {
		n, peer, err := socket.ReadFrom(rb)
		if err != nil {
			if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
				log.Infof("Timeout reading from socket for %s: %s", target, err)
				return
			}
			log.Errorf("Error reading from socket for %s: %s", target, err)
			continue
		}
		if peer.String() != ip.String() {
			continue
		}
		if bytes.Compare(rb[:n], wb) == 0 {
			success = true
			return
		}
	}
	return
}

func TestPingGoogle(t *testing.T) {
	if testing.Short() {
		t.Skip("to avoid external network")
	}
	switch runtime.GOOS {
	case "darwin":
	case "linux":
		t.Log("you may need to adjust the net.ipv4.ping_group_range kernel state")
	default:
		t.Skipf("not supported on %q", runtime.GOOS)
	}

	for i, tt := range pingGoogleTests {
		if tt.network[:2] == "ip" && os.Getuid() != 0 {
			continue
		}
		c, err := icmp.ListenPacket(tt.network, tt.address)
		if err != nil {
			t.Error(err)
			continue
		}
		defer c.Close()

		dst, err := googleAddr(c, tt.protocol)
		if err != nil {
			t.Error(err)
			continue
		}

		wm := icmp.Message{
			Type: tt.mtype, Code: 0,
			Body: &icmp.Echo{
				ID: os.Getpid() & 0xffff, Seq: 1 << uint(i),
				Data: []byte("HELLO-R-U-THERE"),
			},
		}
		wb, err := wm.Marshal(nil)
		if err != nil {
			t.Error(err)
			continue
		}
		if n, err := c.WriteTo(wb, dst); err != nil {
			t.Error(err, dst)
			continue
		} else if n != len(wb) {
			t.Errorf("got %v; want %v", n, len(wb))
			continue
		}

		rb := make([]byte, 1500)
		n, peer, err := c.ReadFrom(rb)
		if err != nil {
			t.Error(err)
			continue
		}
		rm, err := icmp.ParseMessage(tt.protocol, rb[:n])
		if err != nil {
			t.Error(err)
			continue
		}
		switch rm.Type {
		case ipv4.ICMPTypeEchoReply, ipv6.ICMPTypeEchoReply:
			t.Logf("got reflection from %v", peer)
		default:
			t.Errorf("got %+v; want echo reply", rm)
		}
	}
}

func doPing(tt pingTest, seq int) error {
	c, err := icmp.ListenPacket(tt.network, tt.address)
	if err != nil {
		return err
	}
	defer c.Close()

	dst, err := googleAddr(c, tt.protocol)
	if err != nil {
		return err
	}

	if tt.protocol == iana.ProtocolIPv6ICMP {
		var f ipv6.ICMPFilter
		f.SetAll(true)
		f.Accept(ipv6.ICMPTypeDestinationUnreachable)
		f.Accept(ipv6.ICMPTypePacketTooBig)
		f.Accept(ipv6.ICMPTypeTimeExceeded)
		f.Accept(ipv6.ICMPTypeParameterProblem)
		f.Accept(ipv6.ICMPTypeEchoReply)
		if err := c.IPv6PacketConn().SetICMPFilter(&f); err != nil {
			return err
		}
	}

	wm := icmp.Message{
		Type: tt.mtype, Code: 0,
		Body: &icmp.Echo{
			ID: os.Getpid() & 0xffff, Seq: 1 << uint(seq),
			Data: []byte("HELLO-R-U-THERE"),
		},
	}
	wb, err := wm.Marshal(nil)
	if err != nil {
		return err
	}
	if n, err := c.WriteTo(wb, dst); err != nil {
		return err
	} else if n != len(wb) {
		return fmt.Errorf("got %v; want %v", n, len(wb))
	}

	rb := make([]byte, 1500)
	if err := c.SetReadDeadline(time.Now().Add(3 * time.Second)); err != nil {
		return err
	}
	n, peer, err := c.ReadFrom(rb)
	if err != nil {
		return err
	}
	rm, err := icmp.ParseMessage(tt.protocol, rb[:n])
	if err != nil {
		return err
	}
	switch rm.Type {
	case ipv4.ICMPTypeEchoReply, ipv6.ICMPTypeEchoReply:
		return nil
	default:
		return fmt.Errorf("got %+v from %v; want echo reply", rm, peer)
	}
}