手写的 Go ping 实现

package main

import (
	"fmt"
	"net"
	"os"
	"time"
	"golang.org/x/net/icmp"
	"golang.org/x/net/ipv4"
)

const (
	icmpTypeEchoRequest = 8
	icmpTypeEchoReply   = 0
)

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Usage: go run ping.go <host>")
		return
	}
	host := os.Args[1]

	address, err := net.ResolveIPAddr("ip", host)
	if err != nil {
		fmt.Println("ResolveIPAddr failed:", err)
		return
	}

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

	for i := 0; i < 4; i++ {
		start := time.Now()
		err = sendICMP(conn, address)
		if err != nil {
			fmt.Println("Send failed:", err)
			return
		}

		err = receiveICMP(conn)
		if err != nil {
			fmt.Println("Receive failed:", err)
			return
		}

		rtt := time.Since(start)
		fmt.Printf("Reply from %s: bytes=32 time=%v\n", host, rtt)
		time.Sleep(1 * time.Second)
	}
}

func sendICMP(conn *net.IPConn, address *net.IPAddr) error {
	msg := icmp.Message{
		Type: ipv4.ICMPTypeEcho, Code: 0,
		Body: &icmp.Echo{Seq: 1, ID: 1, Data: []byte("HELLO")},
	}

	data, err := msg.Marshal(nil)
	if err != nil {
		return err
	}

	_, err = conn.WriteTo(data, address)
	return err
}

func receiveICMP(conn *net.IPConn) error {
	buf := make([]byte, 1500)
	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	_, _, err := conn.ReadFrom(buf)
	return err
}