gcc/libgo/go/net/sockopt_windows.go

// 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"
	"syscall"
)

func setDefaultSockopts(s syscall.Handle, family, sotype int, ipv6only bool) error {
	if family == syscall.AF_INET6 && sotype != syscall.SOCK_RAW {
		// Allow both IP versions even if the OS default
		// is otherwise. Note that some operating systems
		// never admit this option.
		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, boolint(ipv6only))
	}
	if (sotype == syscall.SOCK_DGRAM || sotype == syscall.SOCK_RAW) && family != syscall.AF_UNIX && family != syscall.AF_INET6 {
		// Allow broadcast.
		return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1))
	}
	return nil
}

func setDefaultListenerSockopts(s syscall.Handle) error {
	// Windows will reuse recently-used addresses by default.
	// SO_REUSEADDR should not be used here, as it allows
	// a socket to forcibly bind to a port in use by another socket.
	// This could lead to a non-deterministic behavior, where
	// connection requests over the port cannot be guaranteed
	// to be handled by the correct socket.
	return nil
}

func setDefaultMulticastSockopts(s syscall.Handle) error {
	// Allow multicast UDP and raw IP datagram sockets to listen
	// concurrently across multiple listeners.
	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
}