// Copyright 2012 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package ipv4_test import ( "fmt" "log" "net" "os" "runtime" "time" "golang.org/x/net/icmp" "golang.org/x/net/internal/iana" "golang.org/x/net/ipv4" ) func ExampleConn_markingTCP() { ln, err := net.Listen("tcp4", "0.0.0.0:1024") if err != nil { log.Fatal(err) } defer ln.Close() for { c, err := ln.Accept() if err != nil { log.Fatal(err) } go func(c net.Conn) { defer c.Close() p := ipv4.NewConn(c) if err := p.SetTOS(iana.DiffServAF11); err != nil { log.Fatal(err) } if err := p.SetTTL(128); err != nil { log.Fatal(err) } if _, err := c.Write([]byte("HELLO-R-U-THERE-ACK")); err != nil { log.Fatal(err) } }(c) } } func ExamplePacketConn_servingOneShotMulticastDNS() { c, err := net.ListenPacket("udp4", "0.0.0.0:5353") // mDNS over UDP if err != nil { log.Fatal(err) } defer c.Close() p := ipv4.NewPacketConn(c) en0, err := net.InterfaceByName("en0") if err != nil { log.Fatal(err) } mDNSLinkLocal := net.UDPAddr{IP: net.IPv4(224, 0, 0, 251)} if err := p.JoinGroup(en0, &mDNSLinkLocal); err != nil { log.Fatal(err) } defer p.LeaveGroup(en0, &mDNSLinkLocal) if err := p.SetControlMessage(ipv4.FlagDst, true); err != nil { log.Fatal(err) } b := make([]byte, 1500) for { _, cm, peer, err := p.ReadFrom(b) if err != nil { log.Fatal(err) } if !cm.Dst.IsMulticast() || !cm.Dst.Equal(mDNSLinkLocal.IP) { continue } answers := []byte("FAKE-MDNS-ANSWERS") // fake mDNS answers, you need to implement this if _, err := p.WriteTo(answers, nil, peer); err != nil { log.Fatal(err) } } } func ExamplePacketConn_tracingIPPacketRoute() { // Tracing an IP packet route to www.google.com. const host = "www.google.com" ips, err := net.LookupIP(host) if err != nil { log.Fatal(err) } var dst net.IPAddr for _, ip := range ips { if ip.To4() != nil { dst.IP = ip fmt.Printf("using %v for tracing an IP packet route to %s\n", dst.IP, host) break } } if dst.IP == nil { log.Fatal("no A record found") } c, err := net.ListenPacket(fmt.Sprintf("ip4:%d", iana.ProtocolICMP), "0.0.0.0") // ICMP for IPv4 if err != nil { log.Fatal(err) } defer c.Close() p := ipv4.NewPacketConn(c) if err := p.SetControlMessage(ipv4.FlagTTL|ipv4.FlagSrc|ipv4.FlagDst|ipv4.FlagInterface, true); err != nil { log.Fatal(err) } wm := icmp.Message{ Type: ipv4.ICMPTypeEcho, Code: 0, Body: &icmp.Echo{ ID: os.Getpid() & 0xffff, Data: []byte("HELLO-R-U-THERE"), }, } rb := make([]byte, 1500) for i := 1; i <= 64; i++ { // up to 64 hops wm.Body.(*icmp.Echo).Seq = i wb, err := wm.Marshal(nil) if err != nil { log.Fatal(err) } if err := p.SetTTL(i); err != nil { log.Fatal(err) } // In the real world usually there are several // multiple traffic-engineered paths for each hop. // You may need to probe a few times to each hop. begin := time.Now() if _, err := p.WriteTo(wb, nil, &dst); err != nil { log.Fatal(err) } if err := p.SetReadDeadline(time.Now().Add(3 * time.Second)); err != nil { log.Fatal(err) } n, cm, peer, err := p.ReadFrom(rb) if err != nil { if err, ok := err.(net.Error); ok && err.Timeout() { fmt.Printf("%v\t*\n", i) continue } log.Fatal(err) } rm, err := icmp.ParseMessage(iana.ProtocolICMP, rb[:n]) if err != nil { log.Fatal(err) } rtt := time.Since(begin) // In the real world you need to determine whether the // received message is yours using ControlMessage.Src, // ControlMessage.Dst, icmp.Echo.ID and icmp.Echo.Seq. switch rm.Type { case ipv4.ICMPTypeTimeExceeded: names, _ := net.LookupAddr(peer.String()) fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm) case ipv4.ICMPTypeEchoReply: names, _ := net.LookupAddr(peer.String()) fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm) return default: log.Printf("unknown ICMP message: %+v\n", rm) } } } func ExampleRawConn_advertisingOSPFHello() { c, err := net.ListenPacket(fmt.Sprintf("ip4:%d", iana.ProtocolOSPFIGP), "0.0.0.0") // OSPF for IPv4 if err != nil { log.Fatal(err) } defer c.Close() r, err := ipv4.NewRawConn(c) if err != nil { log.Fatal(err) } en0, err := net.InterfaceByName("en0") if err != nil { log.Fatal(err) } allSPFRouters := net.IPAddr{IP: net.IPv4(224, 0, 0, 5)} if err := r.JoinGroup(en0, &allSPFRouters); err != nil { log.Fatal(err) } defer r.LeaveGroup(en0, &allSPFRouters) hello := make([]byte, 24) // fake hello data, you need to implement this ospf := make([]byte, 24) // fake ospf header, you need to implement this ospf[0] = 2 // version 2 ospf[1] = 1 // hello packet ospf = append(ospf, hello...) iph := &ipv4.Header{ Version: ipv4.Version, Len: ipv4.HeaderLen, TOS: iana.DiffServCS6, TotalLen: ipv4.HeaderLen + len(ospf), TTL: 1, Protocol: iana.ProtocolOSPFIGP, Dst: allSPFRouters.IP.To4(), } var cm *ipv4.ControlMessage switch runtime.GOOS { case "darwin", "linux": cm = &ipv4.ControlMessage{IfIndex: en0.Index} default: if err := r.SetMulticastInterface(en0); err != nil { log.Fatal(err) } } if err := r.WriteTo(iph, ospf, cm); err != nil { log.Fatal(err) } }