import (
 "bytes"
 "container/list"
 "encoding/binary"
 "fmt"
 "net"
 "os"
 "time"
)

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

arg_num := len(os.Args)
 if arg_num < 2 {
 fmt.Print(
  "Please runAs [super user] in [terminal].\n",
  "Usage:\n",
  "\tgoping url\n",
  "\texample: goping www.baidu.com",
 )
 time.Sleep(5e9)
 return
 }

var (
 icmp   ICMP
 laddr  = net.IPAddr{IP: net.ParseIP("0.0.0.0")}
 raddr, _ = net.ResolveIPAddr("ip", os.Args[1])
 )
 conn, err := net.DialIP("ip4:icmp", &laddr, raddr)
 if err != nil {
 fmt.Println(err.Error())
 return
 }
 defer conn.Close()

icmp.Type = 8
 icmp.Code = 0
 icmp.Checksum = 0
 icmp.Identifier = 0
 icmp.SequenceNum = 0
 var buffer bytes.Buffer
 binary.Write(&buffer, binary.BigEndian, icmp)
 icmp.Checksum = CheckSum(buffer.Bytes())
 buffer.Reset()
 binary.Write(&buffer, binary.BigEndian, icmp)

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)
 return uint16(^sum)
}

fmt.Printf("\n正在 Ping %s 具有 0 字节的数据:\n", raddr.String())
 recv := make([]byte, 1024)
 statistic := list.New()
 sended_packets := 0
 for i := 4; i > 0; i-- {
 if _, err := conn.Write(buffer.Bytes()); err != nil {
  fmt.Println(err.Error())
  return
 }
 sended_packets++
 t_start := time.Now()
 conn.SetReadDeadline((time.Now().Add(time.Second * 5)))
 _, err := conn.Read(recv)
 if err != nil {
  fmt.Println("请求超时")
  continue
 }
 t_end := time.Now()
 dur := t_end.Sub(t_start).Nanoseconds() / 1e6
 fmt.Printf("来自 %s 的回复: 时间 = %dms\n", raddr.String(), dur)
 statistic.PushBack(dur)
 //for i := 0; i < recvsize; i++ {
 // if i == 0 {
 // fmt.Println("")
 // }
 // fmt.Printf("%.2x ", recv[i])
 //}
 //fmt.Println("")
 }

defer func() {
 fmt.Println("")
 //信息统计
 var min, max, sum int64
 if statistic.Len() == 0 {
  min, max, sum = 0, 0, 0
 } else {
  min, max, sum = statistic.Front().Value.(int64), statistic.Front().Value.(int64), int64(0)
 }
 for v := statistic.Front(); v != nil; v = v.Next() {
  val := v.Value.(int64)
  switch {
  case val < min:
  min = val
  case val > max:
  max = val
  }
  sum = sum + val
 }
 recved, losted := statistic.Len(), sended_packets-statistic.Len()
 fmt.Printf("%s 的 Ping 统计信息：\n 数据包：已发送 = %d，已接收 = %d，丢失 = %d (%.1f%% 丢失)，\n往返行程的估计时间(以毫秒为单位)：\n 最短 = %dms，最长 = %dms，平均 = %.0fms\n",
  raddr.String(),
  sended_packets, recved, losted, float32(losted)/float32(sended_packets)*100,
  min, max, float32(sum)/float32(recved),
 )
 }()