1 // Copyright 2012 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
15 "golang.org/x/net/icmp"
16 "golang.org/x/net/ipv4"
19 func ExampleConn_markingTCP() {
20 ln, err := net.Listen("tcp", "0.0.0.0:1024")
33 if c.RemoteAddr().(*net.TCPAddr).IP.To4() != nil {
35 if err := p.SetTOS(0x28); err != nil { // DSCP AF11
38 if err := p.SetTTL(128); err != nil {
42 if _, err := c.Write([]byte("HELLO-R-U-THERE-ACK")); err != nil {
49 func ExamplePacketConn_servingOneShotMulticastDNS() {
50 c, err := net.ListenPacket("udp4", "0.0.0.0:5353") // mDNS over UDP
55 p := ipv4.NewPacketConn(c)
57 en0, err := net.InterfaceByName("en0")
61 mDNSLinkLocal := net.UDPAddr{IP: net.IPv4(224, 0, 0, 251)}
62 if err := p.JoinGroup(en0, &mDNSLinkLocal); err != nil {
65 defer p.LeaveGroup(en0, &mDNSLinkLocal)
66 if err := p.SetControlMessage(ipv4.FlagDst, true); err != nil {
70 b := make([]byte, 1500)
72 _, cm, peer, err := p.ReadFrom(b)
76 if !cm.Dst.IsMulticast() || !cm.Dst.Equal(mDNSLinkLocal.IP) {
79 answers := []byte("FAKE-MDNS-ANSWERS") // fake mDNS answers, you need to implement this
80 if _, err := p.WriteTo(answers, nil, peer); err != nil {
86 func ExamplePacketConn_tracingIPPacketRoute() {
87 // Tracing an IP packet route to www.google.com.
89 const host = "www.google.com"
90 ips, err := net.LookupIP(host)
95 for _, ip := range ips {
98 fmt.Printf("using %v for tracing an IP packet route to %s\n", dst.IP, host)
103 log.Fatal("no A record found")
106 c, err := net.ListenPacket("ip4:1", "0.0.0.0") // ICMP for IPv4
111 p := ipv4.NewPacketConn(c)
113 if err := p.SetControlMessage(ipv4.FlagTTL|ipv4.FlagSrc|ipv4.FlagDst|ipv4.FlagInterface, true); err != nil {
117 Type: ipv4.ICMPTypeEcho, Code: 0,
119 ID: os.Getpid() & 0xffff,
120 Data: []byte("HELLO-R-U-THERE"),
124 rb := make([]byte, 1500)
125 for i := 1; i <= 64; i++ { // up to 64 hops
126 wm.Body.(*icmp.Echo).Seq = i
127 wb, err := wm.Marshal(nil)
131 if err := p.SetTTL(i); err != nil {
135 // In the real world usually there are several
136 // multiple traffic-engineered paths for each hop.
137 // You may need to probe a few times to each hop.
139 if _, err := p.WriteTo(wb, nil, &dst); err != nil {
142 if err := p.SetReadDeadline(time.Now().Add(3 * time.Second)); err != nil {
145 n, cm, peer, err := p.ReadFrom(rb)
147 if err, ok := err.(net.Error); ok && err.Timeout() {
148 fmt.Printf("%v\t*\n", i)
153 rm, err := icmp.ParseMessage(1, rb[:n])
157 rtt := time.Since(begin)
159 // In the real world you need to determine whether the
160 // received message is yours using ControlMessage.Src,
161 // ControlMessage.Dst, icmp.Echo.ID and icmp.Echo.Seq.
163 case ipv4.ICMPTypeTimeExceeded:
164 names, _ := net.LookupAddr(peer.String())
165 fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm)
166 case ipv4.ICMPTypeEchoReply:
167 names, _ := net.LookupAddr(peer.String())
168 fmt.Printf("%d\t%v %+v %v\n\t%+v\n", i, peer, names, rtt, cm)
171 log.Printf("unknown ICMP message: %+v\n", rm)
176 func ExampleRawConn_advertisingOSPFHello() {
177 c, err := net.ListenPacket("ip4:89", "0.0.0.0") // OSPF for IPv4
182 r, err := ipv4.NewRawConn(c)
187 en0, err := net.InterfaceByName("en0")
191 allSPFRouters := net.IPAddr{IP: net.IPv4(224, 0, 0, 5)}
192 if err := r.JoinGroup(en0, &allSPFRouters); err != nil {
195 defer r.LeaveGroup(en0, &allSPFRouters)
197 hello := make([]byte, 24) // fake hello data, you need to implement this
198 ospf := make([]byte, 24) // fake ospf header, you need to implement this
199 ospf[0] = 2 // version 2
200 ospf[1] = 1 // hello packet
201 ospf = append(ospf, hello...)
203 Version: ipv4.Version,
205 TOS: 0xc0, // DSCP CS6
206 TotalLen: ipv4.HeaderLen + len(ospf),
209 Dst: allSPFRouters.IP.To4(),
212 var cm *ipv4.ControlMessage
213 switch runtime.GOOS {
214 case "darwin", "linux":
215 cm = &ipv4.ControlMessage{IfIndex: en0.Index}
217 if err := r.SetMulticastInterface(en0); err != nil {
221 if err := r.WriteTo(iph, ospf, cm); err != nil {