// Copyright 2012 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.packageipv4import("net""golang.org/x/net/internal/socket")// BUG(mikio): On Windows, the ControlMessage for ReadFrom and WriteTo// methods of PacketConn is not implemented.// A payloadHandler represents the IPv4 datagram payload handler.typepayloadHandlerstruct{net.PacketConn*socket.ConnrawOpt}func(c*payloadHandler)ok()bool{returnc!=nil&&c.PacketConn!=nil&&c.Conn!=nil}