ping request

icmp.go

package main

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"net"
	"time"
)

type ICMP struct {
	Type        uint8
	Code        uint8
	Checksum    uint16
	Identifier  uint16
	SequenceNum uint16
}

func main() {
	raddr, _ := net.ResolveIPAddr("ip", "ss.lynn4.me")
	fmt.Println("Target IP:", raddr.String())

	conn, err := net.DialIP("ip4:icmp", nil, raddr)
	if err != nil {
		fmt.Println(err.Error())
		return
	}
	defer conn.Close()

	icmp := ICMP{8, 0, 0, 13, 37}

	var buffer bytes.Buffer
	binary.Write(&buffer, binary.BigEndian, icmp)
	icmp.Checksum = CheckSum(buffer.Bytes())
	buffer.Reset()
	binary.Write(&buffer, binary.BigEndian, icmp)

	if _, err := conn.Write(buffer.Bytes()); err != nil {
		fmt.Println("Write err:", err.Error())
		return
	}

	conn.SetReadDeadline((time.Now().Add(time.Second * 3)))

	response := make([]byte, 1024)
	if _, err := conn.Read(response); err != nil {
		fmt.Println("Read err:", err.Error())
		return
	}
	fmt.Println(response)
}

func CheckSum(data []byte) uint16 {
	var (
		sum    uint32
		length int = len(data)
		index  int
	)
	for length > 1 {
		sum += uint32(data[index])<<8 + uint32(data[index+1])
		index += 2
		length -= 2
	}
	if length > 0 {
		sum += uint32(data[index])
	}
	// sum = (sum >> 16) + (sum & 0xffff)
	sum += (sum >> 16)

	return uint16(^sum)
}