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 */
25package java.net;
26
27import java.util.Properties;
28import sun.security.action.GetPropertyAction;
29
30/**
31 * This class defines a factory for creating DatagramSocketImpls. It defaults
32 * to creating plain DatagramSocketImpls, but may create other DatagramSocketImpls
33 * by setting the impl.prefix system property.
34 *
35 * For Windows versions lower than Windows Vista a TwoStacksPlainDatagramSocketImpl
36 * is always created. This impl supports IPv6 on these platform where available.
37 *
38 * On Windows platforms greater than Vista that support a dual layer TCP/IP stack
39 * a DualStackPlainDatagramSocketImpl is created for DatagramSockets. For MulticastSockets
40 * a TwoStacksPlainDatagramSocketImpl is always created. This is to overcome the lack
41 * of behavior defined for multicasting over a dual layer socket by the RFC.
42 *
43 * @author Chris Hegarty
44 */
45
46class DefaultDatagramSocketImplFactory
47{
48    private static final Class<?> prefixImplClass;
49
50    /* java.net.preferIPv4Stack */
51    private static final boolean preferIPv4Stack;
52
53    /* True if exclusive binding is on for Windows */
54    private static final boolean exclusiveBind;
55
56    static {
57        Class<?> prefixImplClassLocal = null;
58
59        Properties props = GetPropertyAction.privilegedGetProperties();
60        preferIPv4Stack = Boolean.parseBoolean(
61                props.getProperty("java.net.preferIPv4Stack"));
62
63        String exclBindProp = props.getProperty("sun.net.useExclusiveBind", "");
64        exclusiveBind = (exclBindProp.isEmpty())
65                ? true
66                : Boolean.parseBoolean(exclBindProp);
67
68        // impl.prefix
69        String prefix = null;
70        try {
71            prefix = props.getProperty("impl.prefix");
72            if (prefix != null)
73                prefixImplClassLocal = Class.forName("java.net."+prefix+"DatagramSocketImpl");
74        } catch (Exception e) {
75            System.err.println("Can't find class: java.net." +
76                                prefix +
77                                "DatagramSocketImpl: check impl.prefix property");
78        }
79
80        prefixImplClass = prefixImplClassLocal;
81    }
82
83    /**
84     * Creates a new <code>DatagramSocketImpl</code> instance.
85     *
86     * @param   isMulticast true if this impl is to be used for a MutlicastSocket
87     * @return  a new instance of <code>PlainDatagramSocketImpl</code>.
88     */
89    static DatagramSocketImpl createDatagramSocketImpl(boolean isMulticast)
90        throws SocketException {
91        if (prefixImplClass != null) {
92            try {
93                @SuppressWarnings("deprecation")
94                Object result = prefixImplClass.newInstance();
95                return (DatagramSocketImpl) result;
96            } catch (Exception e) {
97                throw new SocketException("can't instantiate DatagramSocketImpl");
98            }
99        } else {
100            if (!preferIPv4Stack && !isMulticast)
101                return new DualStackPlainDatagramSocketImpl(exclusiveBind);
102            else
103                return new TwoStacksPlainDatagramSocketImpl(exclusiveBind && !isMulticast);
104        }
105    }
106}
107