net: add IPv4 multicast to UDPConn
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
diff --git a/src/pkg/net/multicast_test.go b/src/pkg/net/multicast_test.go
new file mode 100644
index 0000000..0c9a035
--- /dev/null
+++ b/src/pkg/net/multicast_test.go
@@ -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)
+}
diff --git a/src/pkg/net/udpsock.go b/src/pkg/net/udpsock.go
index 0270954..f927449 100644
--- a/src/pkg/net/udpsock.go
+++ b/src/pkg/net/udpsock.go
@@ -279,3 +279,44 @@
// 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
+}
