// 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.
//go:build (unix && !linux) || windows
package net
import (
"internal/bytealg"
"runtime"
"syscall"
)
func joinIPv4Group(fd *netFD, ifi *Interface, ip IP) error {
mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
if err := setIPv4MreqToInterface(mreq, ifi); err != nil {
return err
}
err := fd.pfd.SetsockoptIPMreq(syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)
runtime.KeepAlive(fd)
return wrapSyscallError("setsockopt", err)
}
func setIPv4MreqToInterface(mreq *syscall.IPMreq, ifi *Interface) error {
if ifi == nil {
return nil
}
ifat, err := ifi.Addrs()
if err != nil {
return err
}
for _, ifa := range ifat {
switch v := ifa.(type) {
case *IPAddr:
if a := v.IP.To4(); a != nil {
copy(mreq.Interface[:], a)
goto done
}
case *IPNet:
if a := v.IP.To4(); a != nil {
copy(mreq.Interface[:], a)
goto done
}
}
}
done:
if bytealg.Equal(mreq.Interface[:], IPv4zero.To4()) {
return errNoSuchMulticastInterface
}
return nil
}
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