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225 lines
5.2 KiB
Go
225 lines
5.2 KiB
Go
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// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ipv4_test
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import (
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"fmt"
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"log"
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"net"
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"os"
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"runtime"
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"time"
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"golang.org/x/net/icmp"
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"golang.org/x/net/ipv4"
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)
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func ExampleConn_markingTCP() {
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ln, err := net.Listen("tcp", "0.0.0.0:1024")
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if err != nil {
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log.Fatal(err)
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}
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defer ln.Close()
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for {
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c, err := ln.Accept()
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if err != nil {
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log.Fatal(err)
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}
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go func(c net.Conn) {
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defer c.Close()
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if c.RemoteAddr().(*net.TCPAddr).IP.To4() != nil {
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p := ipv4.NewConn(c)
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if err := p.SetTOS(0x28); err != nil { // DSCP AF11
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log.Fatal(err)
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}
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if err := p.SetTTL(128); err != nil {
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log.Fatal(err)
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}
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}
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if _, err := c.Write([]byte("HELLO-R-U-THERE-ACK")); err != nil {
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log.Fatal(err)
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}
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}(c)
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}
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}
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func ExamplePacketConn_servingOneShotMulticastDNS() {
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c, err := net.ListenPacket("udp4", "0.0.0.0:5353") // mDNS over UDP
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if err != nil {
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log.Fatal(err)
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}
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defer c.Close()
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p := ipv4.NewPacketConn(c)
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en0, err := net.InterfaceByName("en0")
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if err != nil {
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log.Fatal(err)
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}
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mDNSLinkLocal := net.UDPAddr{IP: net.IPv4(224, 0, 0, 251)}
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if err := p.JoinGroup(en0, &mDNSLinkLocal); err != nil {
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log.Fatal(err)
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}
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defer p.LeaveGroup(en0, &mDNSLinkLocal)
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if err := p.SetControlMessage(ipv4.FlagDst, true); err != nil {
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log.Fatal(err)
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}
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b := make([]byte, 1500)
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for {
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_, cm, peer, err := p.ReadFrom(b)
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if err != nil {
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log.Fatal(err)
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}
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if !cm.Dst.IsMulticast() || !cm.Dst.Equal(mDNSLinkLocal.IP) {
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continue
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}
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answers := []byte("FAKE-MDNS-ANSWERS") // fake mDNS answers, you need to implement this
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if _, err := p.WriteTo(answers, nil, peer); err != nil {
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log.Fatal(err)
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}
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}
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}
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func ExamplePacketConn_tracingIPPacketRoute() {
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// Tracing an IP packet route to www.google.com.
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const host = "www.google.com"
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ips, err := net.LookupIP(host)
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if err != nil {
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log.Fatal(err)
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}
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var dst net.IPAddr
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for _, ip := range ips {
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if ip.To4() != nil {
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dst.IP = ip
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fmt.Printf("using %v for tracing an IP packet route to %s\n", dst.IP, host)
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break
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}
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}
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if dst.IP == nil {
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log.Fatal("no A record found")
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}
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c, err := net.ListenPacket("ip4:1", "0.0.0.0") // ICMP for IPv4
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if err != nil {
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log.Fatal(err)
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}
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defer c.Close()
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p := ipv4.NewPacketConn(c)
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if err := p.SetControlMessage(ipv4.FlagTTL|ipv4.FlagSrc|ipv4.FlagDst|ipv4.FlagInterface, true); err != nil {
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log.Fatal(err)
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}
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wm := icmp.Message{
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Type: ipv4.ICMPTypeEcho, Code: 0,
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Body: &icmp.Echo{
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ID: os.Getpid() & 0xffff,
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Data: []byte("HELLO-R-U-THERE"),
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},
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}
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rb := make([]byte, 1500)
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for i := 1; i <= 64; i++ { // up to 64 hops
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wm.Body.(*icmp.Echo).Seq = i
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wb, err := wm.Marshal(nil)
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if err != nil {
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log.Fatal(err)
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}
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if err := p.SetTTL(i); err != nil {
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log.Fatal(err)
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}
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// In the real world usually there are several
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// multiple traffic-engineered paths for each hop.
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// You may need to probe a few times to each hop.
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begin := time.Now()
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if _, err := p.WriteTo(wb, nil, &dst); err != nil {
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log.Fatal(err)
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}
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if err := p.SetReadDeadline(time.Now().Add(3 * time.Second)); err != nil {
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log.Fatal(err)
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}
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n, cm, peer, err := p.ReadFrom(rb)
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if err != nil {
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if err, ok := err.(net.Error); ok && err.Timeout() {
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fmt.Printf("%v\t*\n", i)
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continue
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}
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log.Fatal(err)
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}
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rm, err := icmp.ParseMessage(1, rb[:n])
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if err != nil {
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log.Fatal(err)
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}
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rtt := time.Since(begin)
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// In the real world you need to determine whether the
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// received message is yours using ControlMessage.Src,
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// ControlMessage.Dst, icmp.Echo.ID and icmp.Echo.Seq.
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switch rm.Type {
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case ipv4.ICMPTypeTimeExceeded:
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names, _ := net.LookupAddr(peer.String())
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fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm)
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case ipv4.ICMPTypeEchoReply:
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names, _ := net.LookupAddr(peer.String())
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fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm)
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return
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default:
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log.Printf("unknown ICMP message: %+v\n", rm)
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}
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}
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}
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func ExampleRawConn_advertisingOSPFHello() {
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c, err := net.ListenPacket("ip4:89", "0.0.0.0") // OSPF for IPv4
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if err != nil {
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log.Fatal(err)
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}
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defer c.Close()
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r, err := ipv4.NewRawConn(c)
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if err != nil {
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log.Fatal(err)
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}
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en0, err := net.InterfaceByName("en0")
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if err != nil {
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log.Fatal(err)
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}
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allSPFRouters := net.IPAddr{IP: net.IPv4(224, 0, 0, 5)}
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if err := r.JoinGroup(en0, &allSPFRouters); err != nil {
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log.Fatal(err)
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}
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defer r.LeaveGroup(en0, &allSPFRouters)
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hello := make([]byte, 24) // fake hello data, you need to implement this
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ospf := make([]byte, 24) // fake ospf header, you need to implement this
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ospf[0] = 2 // version 2
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ospf[1] = 1 // hello packet
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ospf = append(ospf, hello...)
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iph := &ipv4.Header{
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Version: ipv4.Version,
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Len: ipv4.HeaderLen,
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TOS: 0xc0, // DSCP CS6
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TotalLen: ipv4.HeaderLen + len(ospf),
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TTL: 1,
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Protocol: 89,
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Dst: allSPFRouters.IP.To4(),
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}
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var cm *ipv4.ControlMessage
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switch runtime.GOOS {
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case "darwin", "linux":
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cm = &ipv4.ControlMessage{IfIndex: en0.Index}
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default:
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if err := r.SetMulticastInterface(en0); err != nil {
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log.Fatal(err)
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}
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}
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if err := r.WriteTo(iph, ospf, cm); err != nil {
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log.Fatal(err)
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}
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}
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