1 /*
   2  * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package java.net;
  26 
  27 import java.security.AccessController;
  28 import java.security.PrivilegedAction;
  29 import sun.security.action.GetPropertyAction;
  30 
  31 /**
  32  * This class defines a factory for creating DatagramSocketImpls. It defaults
  33  * to creating plain DatagramSocketImpls, but may create other DatagramSocketImpls
  34  * by setting the impl.prefix system property.
  35  *
  36  * For Windows versions lower than Windows Vista a TwoStacksPlainDatagramSocketImpl
  37  * is always created. This impl supports IPv6 on these platform where available.
  38  *
  39  * On Windows platforms greater than Vista that support a dual layer TCP/IP stack
  40  * a DualStackPlainDatagramSocketImpl is created for DatagramSockets. For MulticastSockets
  41  * a TwoStacksPlainDatagramSocketImpl is always created. This is to overcome the lack
  42  * of behavior defined for multicasting over a dual layer socket by the RFC.
  43  *
  44  * @author Chris Hegarty
  45  */
  46 
  47 class DefaultDatagramSocketImplFactory
  48 {
  49     private static final Class<?> prefixImplClass;
  50 
  51     /* java.net.preferIPv4Stack */
  52     private static final boolean preferIPv4Stack;
  53 
  54     /* True if exclusive binding is on for Windows */
  55     private static final boolean exclusiveBind;
  56 
  57     static {
  58         Class<?> prefixImplClassLocal = null;
  59 
  60         preferIPv4Stack = Boolean.parseBoolean(
  61                 AccessController.doPrivileged(
  62                         new GetPropertyAction("java.net.preferIPv4Stack")));
  63 
  64         String exclBindProp = AccessController.doPrivileged(
  65                 new GetPropertyAction("sun.net.useExclusiveBind", ""));
  66         exclusiveBind = (exclBindProp.isEmpty())
  67                 ? true
  68                 : Boolean.parseBoolean(exclBindProp);
  69 
  70         // impl.prefix
  71         String prefix = null;
  72         try {
  73             prefix = AccessController.doPrivileged(
  74                 new GetPropertyAction("impl.prefix", null));
  75             if (prefix != null)
  76                 prefixImplClassLocal = Class.forName("java.net."+prefix+"DatagramSocketImpl");
  77         } catch (Exception e) {
  78             System.err.println("Can't find class: java.net." +
  79                                 prefix +
  80                                 "DatagramSocketImpl: check impl.prefix property");
  81         }
  82 
  83         prefixImplClass = prefixImplClassLocal;
  84     }
  85 
  86     /**
  87      * Creates a new <code>DatagramSocketImpl</code> instance.
  88      *
  89      * @param   isMulticast true if this impl is to be used for a MutlicastSocket
  90      * @return  a new instance of <code>PlainDatagramSocketImpl</code>.
  91      */
  92     static DatagramSocketImpl createDatagramSocketImpl(boolean isMulticast)
  93         throws SocketException {
  94         if (prefixImplClass != null) {
  95             try {
  96                 return (DatagramSocketImpl) prefixImplClass.newInstance();
  97             } catch (Exception e) {
  98                 throw new SocketException("can't instantiate DatagramSocketImpl");
  99             }
 100         } else {
 101             if (!preferIPv4Stack && !isMulticast)
 102                 return new DualStackPlainDatagramSocketImpl(exclusiveBind);
 103             else
 104                 return new TwoStacksPlainDatagramSocketImpl(exclusiveBind && !isMulticast);
 105         }
 106     }
 107 }