blob: 226e57766deec0c5569986d05e32bd8423c2085d [file] [log] [blame]
// 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/ipv4"
)
func ExampleConn_markingTCP() {
ln, err := net.Listen("tcp", "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()
if c.RemoteAddr().(*net.TCPAddr).IP.To4() != nil {
p := ipv4.NewConn(c)
if err := p.SetTOS(0x28); err != nil { // DSCP AF11
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("ip4:1", "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(1, 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("ip4:89", "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: 0xc0, // DSCP CS6
TotalLen: ipv4.HeaderLen + len(ospf),
TTL: 1,
Protocol: 89,
Dst: allSPFRouters.IP.To4(),
}
var cm *ipv4.ControlMessage
switch runtime.GOOS {
case "darwin", "ios", "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)
}
}