|  | // 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 ( | 
|  | "os" | 
|  | "runtime" | 
|  | "syscall" | 
|  | "unsafe" | 
|  | ) | 
|  |  | 
|  | func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error { | 
|  | ip, err := interfaceToIPv4Addr(ifi) | 
|  | if err != nil { | 
|  | return os.NewSyscallError("setsockopt", err) | 
|  | } | 
|  | var a [4]byte | 
|  | copy(a[:], ip.To4()) | 
|  | err = fd.pfd.Setsockopt(syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, (*byte)(unsafe.Pointer(&a[0])), 4) | 
|  | runtime.KeepAlive(fd) | 
|  | return wrapSyscallError("setsockopt", err) | 
|  | } | 
|  |  | 
|  | func setIPv4MulticastLoopback(fd *netFD, v bool) error { | 
|  | err := fd.pfd.SetsockoptInt(syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, boolint(v)) | 
|  | runtime.KeepAlive(fd) | 
|  | return wrapSyscallError("setsockopt", err) | 
|  | } |