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net: add IPv4 multicast to UDPConn

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notes:
Darwin is very particular about joining a multicast group if the
listneing socket is not created in "udp4" mode, the other supported
OS's are more flexible.

A simple example sets up a socket to listen on the mdns/bonjour
group 224.0.0.251:5353

// ensure the sock is udp4, and the IP is a 4 byte IPv4
socket, err := net.ListenUDP("udp4", &net.UDPAddr {
        IP: net.IPv4zero,
        // currently darwin will not allow you to bind to
        // a port if it is already bound to another process
        Port: 5353,
})
if err != nil {
        log.Exitf("listen %s", err)
}
defer socket.Close()
err = socket.JoinGroup(net.IPv4(224, 0, 0, 251))
if err != nil {
        log.Exitf("join group %s", err)
}

R=adg, rsc
CC=golang-dev
https://golang.org/cl/4066044
This commit is contained in:
Dave Cheney 2011-02-16 15:07:13 -05:00 committed by Russ Cox
parent 9b66129fe3
commit 0856731daa
2 changed files with 97 additions and 0 deletions
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56
src/pkg/net/multicast_test.go Normal file
View File

@ -0,0 +1,56 @@
// Copyright 2011 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 net
import (
"testing"
)
func TestMulticastJoinAndLeave(t *testing.T) {
addr := &UDPAddr{
IP: IPv4zero,
Port: 0,
}
// open a UDPConn
conn, err := ListenUDP("udp4", addr)
if err != nil {
t.Fatal(err)
}
defer conn.Close()
// try to join group
mcast := IPv4(224, 0, 0, 251)
err = conn.JoinGroup(mcast)
if err != nil {
t.Fatal(err)
}
// try to leave group
err = conn.LeaveGroup(mcast)
if err != nil {
t.Fatal(err)
}
}
func TestJoinFailureWithIPv6Address(t *testing.T) {
addr := &UDPAddr{
IP: IPv4zero,
Port: 0,
}
// open a UDPConn
conn, err := ListenUDP("udp4", addr)
if err != nil {
t.Fatal(err)
}
defer conn.Close()
// try to join group
mcast := ParseIP("ff02::1")
err = conn.JoinGroup(mcast)
if err == nil {
t.Fatal("JoinGroup succeeded, should fail")
}
t.Logf("%s", err)
}

41
src/pkg/net/udpsock.go
View File

@ -279,3 +279,44 @@ func (c *UDPConn) BindToDevice(device string) os.Error {
// It is the caller's responsibility to close f when finished.
// Closing c does not affect f, and closing f does not affect c.
func (c *UDPConn) File() (f *os.File, err os.Error) { return c.fd.dup() }
var errInvalidMulticast = os.ErrorString("invalid IPv4 multicast address")
// JoinGroup joins the IPv4 multicast group named by addr.
// The UDPConn must use the "udp4" network.
func (c *UDPConn) JoinGroup(addr IP) os.Error {
if !c.ok() {
return os.EINVAL
}
ip := addr.To4()
if ip == nil {
return &OpError{"joingroup", "udp", &IPAddr{ip}, errInvalidMulticast}
}
mreq := &syscall.IpMreq{
Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]},
}
err := os.NewSyscallError("setsockopt", syscall.SetsockoptIpMreq(c.fd.sysfd, syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq))
if err != nil {
return &OpError{"joingroup", "udp", &IPAddr{ip}, err}
}
return nil
}
// LeaveGroup exits the IPv4 multicast group named by addr.
func (c *UDPConn) LeaveGroup(addr IP) os.Error {
if !c.ok() {
return os.EINVAL
}
ip := addr.To4()
if ip == nil {
return &OpError{"leavegroup", "udp", &IPAddr{ip}, errInvalidMulticast}
}
mreq := &syscall.IpMreq{
Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]},
}
err := os.NewSyscallError("setsockopt", syscall.SetsockoptIpMreq(c.fd.sysfd, syscall.IPPROTO_IP, syscall.IP_DROP_MEMBERSHIP, mreq))
if err != nil {
return &OpError{"leavegroup", "udp", &IPAddr{ip}, err}
}
return nil
}