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