import (
	"bytes"
	"fmt"
	"golang.org/x/net/icmp"
	"golang.org/x/net/ipv4"
	"golang.org/x/net/ipv6"
	"net"
	"strings"
	"time"
)

func SendIPv4ICMP1(ttl int) error {
	conn, err := icmp.ListenPacket("udp4", "")
	if err != nil {
		return err
	}
	ipaddr, err := net.ResolveIPAddr("ip4", "8.8.8.8")
	if err != nil {
		return err
	}
	addr := &net.UDPAddr{
		IP:   ipaddr.IP,
		Zone: ipaddr.Zone,
	}
	data := make([]byte, packageSize)
	data = append(data, bytes.Repeat([]byte{1}, packageSize)...)
	body := &icmp.Echo{
		ID:   1,
		Seq:  1,
		Data: data,
	}
	msg := &icmp.Message{
		Type: ipv4.ICMPTypeEcho,
		Code: 0,
		Body: body,
	}
	msgBytes, err := msg.Marshal(nil)
	if err != nil {
		return err
	}
	err = conn.IPv4PacketConn().SetControlMessage(ipv4.FlagTTL, true)
	if err != nil {
		return fmt.Errorf("SetControlMessage()，%s", err)
	}
	fmt.Println(fmt.Sprintf("TTL：%d", ttl))
	if err = conn.IPv4PacketConn().SetTTL(ttl); err != nil {
		return fmt.Errorf("conn.IPv4PacketConn().SetTTL()失败，%s", err)
	}
	_, err = conn.WriteTo(msgBytes, addr)
	if err != nil {
		return fmt.Errorf("conn.WriteTo()失败，%s", err)
	}

	for {
		// 包+头
		buf := make([]byte, 1500)
		if err := conn.SetReadDeadline(time.Now().Add(time.Millisecond * 1500)); err != nil {
			return err
		}
		n, src, err := conn.ReadFrom(buf)
		if n > 0 {
			fmt.Println(n)
			fmt.Println(src.String())
		}
		if err != nil {
			if neterr, ok := err.(*net.OpError); ok {
				if neterr.Timeout() {
					fmt.Println("read超时了")
					continue
				}
			}
			return err
		}
		// 结果如8.8.8.8:0
		respAddr := src.String()
		splitSrc := strings.Split(respAddr, ":")
		if len(splitSrc) == 2 {
			respAddr = splitSrc[0]
		}
		x, err := icmp.ParseMessage(protocolICMP, buf)
		if err != nil {
			return fmt.Errorf("error parsing icmp message: %w", err)
		}
		// 超时
		if x.Type == ipv4.ICMPTypeTimeExceeded || x.Type == ipv6.ICMPTypeTimeExceeded {
			switch pkt := x.Body.(type) {
			case *icmp.TimeExceeded:
				// 设置ttl后，一定会返回这个超时内容，头部长度是20，因此从20之后开始解析
				m, err := icmp.ParseMessage(protocolICMP, pkt.Data[20:])
				if err != nil {
					return err
				}
				switch p := m.Body.(type) {
				case *icmp.Echo:
                                          fmt.Println(p.ID)
                                          fmt.Println(respAddr)
				default:
					return fmt.Errorf("invalid ICMP time exceeded and echo reply; type: '%T', '%v'", pkt, pkt)
				}
			default:
				return fmt.Errorf("invalid ICMP time exceeded; type: '%T', '%v'", pkt, pkt)
			}

		}
		// 收到echo reply，证明到达目的ip
		if x.Type == ipv4.ICMPTypeEchoReply || x.Type == ipv6.ICMPTypeEchoReply {
			// echo reply的时候，返回的包不可能比发的包小
			if n < packageSize {
				continue
			}
			switch pkt := x.Body.(type) {
			// 只有到达目的ip，是echo
			case *icmp.Echo:
                                  fmt.Println(respAddr)
			
			default:
				return fmt.Errorf("invalid ICMP echo reply; type: '%T', '%v'", pkt, pkt)
			}
		}
	}
	return nil
}