构建ICMP Ping库：超时与延迟回复的处理策略

Request timeout for icmp_seq 2
Request timeout for icmp_seq 3
64 bytes from 80.67.169.18: icmp_seq=2 ttl=58 time=2216.104 ms
64 bytes from 80.67.169.18: icmp_seq=3 ttl=58 time=1216.559 ms

// makePingRequest 构造ICMP Echo Request数据包
func makePingRequest(id, seq, pktlen int, filler []byte) []byte {
    // ... 省略具体实现，主要负责设置ICMP类型、代码、校验和、ID和序列号 ...
    p[0] = ICMP_ECHO_REQUEST // type
    p[4] = uint8(id >> 8)    // id
    p[5] = uint8(id & 0xff)  // id
    p[6] = uint8(seq >> 8)   // sequence
    p[7] = uint8(seq & 0xff) // sequence
    // ...
    return p
}

// parsePingReply 解析ICMP Echo Reply数据包
func parsePingReply(p []byte) (id, seq, code int) {
    id = int(p[24])<<8 | int(p[25])
    seq = int(p[26])<<8 | int(p[27])
    code = int(p[21])
    return
}

// Pinguntil 持续发送ICMP Echo数据包并接收回复
func Pinguntil(destination string, count int, response chan Response, delay time.Duration) {
    // ... 省略初始化和错误处理 ...

    sendid := os.Getpid() & 0xffff // 使用进程ID作为Ping ID
    seq := 0

    for ; seq < count || count == 0; seq++ {
        // ... 省略序列号循环处理 ...

        sendpkt := makePingRequest(sendid, seq, pingpktlen, []byte("Go Ping"))
        start := time.Now()

        // 发送数据包
        writesize, err := ipconn.Write(sendpkt)
        if err != nil || writesize != pingpktlen {
            // ... 错误处理，报告发送失败 ...
            time.Sleep(delay)
            continue
        }

        // 设置读取截止时间，实现超时机制
        ipconn.SetReadDeadline(time.Now().Add(time.Second * 1)) // 1秒超时

        resp := make([]byte, 1024)
        for { // 循环读取回复
            readsize, err := ipconn.Read(resp)
            elapsed := time.Now().Sub(start)
            rid, rseq, rcode := parsePingReply(resp)

            if err != nil { // 读取错误或超时
                response <- Response{Delay: 0, Error: err, Destination: raddr.IP.String(), Seq: seq, Writesize: writesize, Readsize: readsize}
                break // 跳出内部循环，处理下一个序列号
            } else if rcode != ICMP_ECHO_REPLY || rseq != seq || rid != sendid {
                // 如果不是Echo Reply，或序列号/ID不匹配，则继续读取下一个数据包
                continue
            } else { // 成功收到匹配的回复
                response <- Response{Delay: elapsed, Error: err, Destination: raddr.IP.String(), Seq: seq, Writesize: writesize, Readsize: readsize}
                break // 跳出内部循环
            }
        }
        time.Sleep(delay - elapsed) // 控制发送间隔
    }
    close(response)
}