154 lines
3.4 KiB
Go
154 lines
3.4 KiB
Go
package nettest
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import (
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"bytes"
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"encoding/binary"
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"log"
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"net"
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"strconv"
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"time"
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)
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// ICMP ICMP 报文头
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type ICMP struct {
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Type uint8
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Code uint8
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Checksum uint16
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Identifier uint16
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SequenceNum uint16
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}
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// Ping 单次探测器：port 为 0 时走 ICMP，否则走 TCP 端口探测
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type Ping struct {
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addr string
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port int
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timeout int64
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icmp ICMP
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size int
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}
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// NewPing 创建探测器，timeout 为超时毫秒数
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func NewPing(addr string, port int, timeout int64) *Ping {
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p := new(Ping)
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p.addr = addr
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p.port = port
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p.timeout = timeout
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p.size = 32
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// icmp
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p.icmp.Type = 8
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p.icmp.Code = 0
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p.icmp.Checksum = 0
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p.icmp.Identifier = 1
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p.icmp.SequenceNum = 0
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return p
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}
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// Set 修改探测目标与超时
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func (p *Ping) Set(addr string, port int, timeout int64) {
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p.addr = addr
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p.port = port
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p.timeout = timeout
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}
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// Test 执行一次探测，返回耗时毫秒数；失败返回 -1
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func (p *Ping) Test() int {
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et := 0
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if p.port == 0 {
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et = p.icmpEcho()
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} else {
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et = p.portCheck()
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}
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return et
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}
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// icmpEcho 发送 ICMP Echo 并等待回包，返回耗时毫秒数（需管理员权限）
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func (p *Ping) icmpEcho() int {
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conn, err := net.DialTimeout("ip:icmp", p.addr, time.Duration(p.timeout)*time.Millisecond)
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if err != nil {
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log.Println(err)
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return -1
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}
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defer conn.Close()
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var buffer bytes.Buffer
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binary.Write(&buffer, binary.BigEndian, p.icmp) // 以大端模式写入
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data := make([]byte, p.size) //
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buffer.Write(data)
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data = buffer.Bytes()
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p.icmp.SequenceNum++
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// 检验和设为0
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data[2] = byte(0)
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data[3] = byte(0)
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data[6] = byte(p.icmp.SequenceNum >> 8)
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data[7] = byte(p.icmp.SequenceNum)
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p.icmp.Checksum = CheckSum(data)
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data[2] = byte(p.icmp.Checksum >> 8)
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data[3] = byte(p.icmp.Checksum)
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// 开始时间
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t1 := time.Now()
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err = conn.SetDeadline(t1.Add(time.Duration(time.Duration(p.timeout) * time.Millisecond)))
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if err != nil {
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//log.Println(err)
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return -1
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}
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_, err = conn.Write(data)
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if err != nil {
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//log.Println(err)
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return -1
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}
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buf := make([]byte, 65535)
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_, err = conn.Read(buf)
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if err != nil {
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//fmt.Println("请求超时。")
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return -1
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}
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et := int(time.Since(t1) / 1000000)
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return et
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}
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// CheckSum 计算 ICMP 校验和
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func CheckSum(data []byte) uint16 {
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var sum uint32
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var length = len(data)
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var index int
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for length > 1 { // 溢出部分直接去除
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sum += uint32(data[index])<<8 + uint32(data[index+1])
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index += 2
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length -= 2
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}
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if length == 1 {
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sum += uint32(data[index])
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}
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// CheckSum的值是16位，计算是将高16位加低16位，得到的结果进行重复以该方式进行计算，直到高16位为0
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/*
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sum的最大情况是：ffffffff
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第一次高16位+低16位：ffff + ffff = 1fffe
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第二次高16位+低16位：0001 + fffe = ffff
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即推出一个结论，只要第一次高16位+低16位的结果，再进行之前的计算结果用到高16位+低16位，即可处理溢出情况
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*/
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sum = uint32(sum>>16) + uint32(sum)
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sum = uint32(sum>>16) + uint32(sum)
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return uint16(^sum)
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}
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// portCheck TCP 端口探测，返回连接耗时毫秒数；失败返回 -1
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func (p *Ping) portCheck() int {
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// 开始时间
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t1 := time.Now()
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conn, err := net.DialTimeout("tcp", p.addr+":"+strconv.Itoa(p.port), time.Duration(p.timeout)*time.Millisecond)
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et := int(time.Since(t1) / 1000000)
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if err != nil {
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//log.Println(err)
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//fmt.Println("请求超时。")
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return -1
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}
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defer conn.Close()
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return et
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}
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