243 lines
7.7 KiB
Go
243 lines
7.7 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 implements IP-level socket options for the Internet
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// Protocol version 4.
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//
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// The package provides IP-level socket options that allow
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// manipulation of IPv4 facilities.
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//
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// The IPv4 protocol and basic host requirements for IPv4 are defined
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// in RFC 791 and RFC 1122.
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// Host extensions for multicasting and socket interface extensions
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// for multicast source filters are defined in RFC 1112 and RFC 3678.
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// IGMPv1, IGMPv2 and IGMPv3 are defined in RFC 1112, RFC 2236 and RFC
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// 3376.
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// Source-specific multicast is defined in RFC 4607.
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//
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//
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// Unicasting
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//
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// The options for unicasting are available for net.TCPConn,
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// net.UDPConn and net.IPConn which are created as network connections
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// that use the IPv4 transport. When a single TCP connection carrying
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// a data flow of multiple packets needs to indicate the flow is
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// important, ipv4.Conn is used to set the type-of-service field on
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// the IPv4 header for each packet.
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//
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// ln, err := net.Listen("tcp4", "0.0.0.0:1024")
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// if err != nil {
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// // error handling
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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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// // error handling
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// }
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// go func(c net.Conn) {
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// defer c.Close()
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//
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// The outgoing packets will be labeled DiffServ assured forwarding
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// class 1 low drop precedence, known as AF11 packets.
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//
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// if err := ipv4.NewConn(c).SetTOS(0x28); err != nil {
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// // error handling
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// }
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// if _, err := c.Write(data); err != nil {
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// // error handling
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// }
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// }(c)
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// }
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//
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//
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// Multicasting
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//
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// The options for multicasting are available for net.UDPConn and
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// net.IPconn which are created as network connections that use the
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// IPv4 transport. A few network facilities must be prepared before
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// you begin multicasting, at a minimum joining network interfaces and
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// multicast groups.
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//
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// en0, err := net.InterfaceByName("en0")
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// if err != nil {
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// // error handling
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// }
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// en1, err := net.InterfaceByIndex(911)
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// if err != nil {
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// // error handling
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// }
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// group := net.IPv4(224, 0, 0, 250)
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//
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// First, an application listens to an appropriate address with an
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// appropriate service port.
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//
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// c, err := net.ListenPacket("udp4", "0.0.0.0:1024")
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// if err != nil {
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// // error handling
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// }
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// defer c.Close()
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//
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// Second, the application joins multicast groups, starts listening to
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// the groups on the specified network interfaces. Note that the
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// service port for transport layer protocol does not matter with this
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// operation as joining groups affects only network and link layer
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// protocols, such as IPv4 and Ethernet.
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//
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// p := ipv4.NewPacketConn(c)
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// if err := p.JoinGroup(en0, &net.UDPAddr{IP: group}); err != nil {
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// // error handling
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// }
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// if err := p.JoinGroup(en1, &net.UDPAddr{IP: group}); err != nil {
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// // error handling
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// }
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//
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// The application might set per packet control message transmissions
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// between the protocol stack within the kernel. When the application
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// needs a destination address on an incoming packet,
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// SetControlMessage of ipv4.PacketConn is used to enable control
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// message transmissons.
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//
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// if err := p.SetControlMessage(ipv4.FlagDst, true); err != nil {
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// // error handling
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// }
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//
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// The application could identify whether the received packets are
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// of interest by using the control message that contains the
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// destination address of the received packet.
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//
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// b := make([]byte, 1500)
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// for {
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// n, cm, src, err := p.ReadFrom(b)
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// if err != nil {
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// // error handling
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// }
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// if cm.Dst.IsMulticast() {
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// if cm.Dst.Equal(group) {
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// // joined group, do something
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// } else {
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// // unknown group, discard
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// continue
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// }
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// }
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//
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// The application can also send both unicast and multicast packets.
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//
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// p.SetTOS(0x0)
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// p.SetTTL(16)
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// if _, err := p.WriteTo(data, nil, src); err != nil {
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// // error handling
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// }
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// dst := &net.UDPAddr{IP: group, Port: 1024}
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// for _, ifi := range []*net.Interface{en0, en1} {
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// if err := p.SetMulticastInterface(ifi); err != nil {
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// // error handling
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// }
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// p.SetMulticastTTL(2)
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// if _, err := p.WriteTo(data, nil, dst); err != nil {
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// // error handling
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// }
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// }
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// }
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//
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//
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// More multicasting
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//
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// An application that uses PacketConn or RawConn may join multiple
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// multicast groups. For example, a UDP listener with port 1024 might
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// join two different groups across over two different network
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// interfaces by using:
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//
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// c, err := net.ListenPacket("udp4", "0.0.0.0:1024")
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// if err != nil {
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// // error handling
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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.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
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// // error handling
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// }
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// if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 249)}); err != nil {
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// // error handling
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// }
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// if err := p.JoinGroup(en1, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 249)}); err != nil {
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// // error handling
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// }
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//
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// It is possible for multiple UDP listeners that listen on the same
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// UDP port to join the same multicast group. The net package will
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// provide a socket that listens to a wildcard address with reusable
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// UDP port when an appropriate multicast address prefix is passed to
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// the net.ListenPacket or net.ListenUDP.
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//
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// c1, err := net.ListenPacket("udp4", "224.0.0.0:1024")
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// if err != nil {
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// // error handling
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// }
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// defer c1.Close()
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// c2, err := net.ListenPacket("udp4", "224.0.0.0:1024")
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// if err != nil {
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// // error handling
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// }
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// defer c2.Close()
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// p1 := ipv4.NewPacketConn(c1)
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// if err := p1.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
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// // error handling
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// }
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// p2 := ipv4.NewPacketConn(c2)
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// if err := p2.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
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// // error handling
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// }
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//
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// Also it is possible for the application to leave or rejoin a
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// multicast group on the network interface.
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//
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// if err := p.LeaveGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
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// // error handling
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// }
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// if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 250)}); err != nil {
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// // error handling
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// }
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//
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//
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// Source-specific multicasting
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//
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// An application that uses PacketConn or RawConn on IGMPv3 supported
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// platform is able to join source-specific multicast groups.
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// The application may use JoinSourceSpecificGroup and
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// LeaveSourceSpecificGroup for the operation known as "include" mode,
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//
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// ssmgroup := net.UDPAddr{IP: net.IPv4(232, 7, 8, 9)}
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// ssmsource := net.UDPAddr{IP: net.IPv4(192, 168, 0, 1)})
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// if err := p.JoinSourceSpecificGroup(en0, &ssmgroup, &ssmsource); err != nil {
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// // error handling
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// }
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// if err := p.LeaveSourceSpecificGroup(en0, &ssmgroup, &ssmsource); err != nil {
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// // error handling
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// }
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//
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// or JoinGroup, ExcludeSourceSpecificGroup,
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// IncludeSourceSpecificGroup and LeaveGroup for the operation known
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// as "exclude" mode.
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//
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// exclsource := net.UDPAddr{IP: net.IPv4(192, 168, 0, 254)}
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// if err := p.JoinGroup(en0, &ssmgroup); err != nil {
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// // error handling
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// }
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// if err := p.ExcludeSourceSpecificGroup(en0, &ssmgroup, &exclsource); err != nil {
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// // error handling
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// }
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// if err := p.LeaveGroup(en0, &ssmgroup); err != nil {
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// // error handling
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// }
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//
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// Note that it depends on each platform implementation what happens
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// when an application which runs on IGMPv3 unsupported platform uses
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// JoinSourceSpecificGroup and LeaveSourceSpecificGroup.
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// In general the platform tries to fall back to conversations using
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// IGMPv1 or IGMPv2 and starts to listen to multicast traffic.
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// In the fallback case, ExcludeSourceSpecificGroup and
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// IncludeSourceSpecificGroup may return an error.
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package ipv4 // import "golang.org/x/net/ipv4"
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