1 /*
2 * Copyright (c) 2002, 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
26 package sun.net.dns;
27
28 import java.util.List;
29 import java.util.LinkedList;
30 import java.util.StringTokenizer;
31 import java.io.IOException;
32
33 /*
34 * An implementation of sun.net.ResolverConfiguration for Windows.
35 */
36
37 public class ResolverConfigurationImpl
38 extends ResolverConfiguration
39 {
40 // Lock helds whilst loading configuration or checking
41 private static Object lock = new Object();
42
43 // Resolver options
44 private final Options opts;
45
46 // Addreses have changed
47 private static boolean changed = false;
48
49 // Time of last refresh.
50 private static long lastRefresh = -1;
51
52 // Cache timeout (120 seconds) - should be converted into property
53 // or configured as preference in the future.
54 private static final int TIMEOUT = 120000;
55
56 // DNS suffix list and name servers populated by native method
57 private static String os_searchlist;
58 private static String os_nameservers;
59
60 // Cached lists
61 private static LinkedList searchlist;
62 private static LinkedList nameservers;
63
64 // Parse string that consists of token delimited by space or commas
65 // and return LinkedHashMap
66 private LinkedList stringToList(String str) {
67 LinkedList ll = new LinkedList();
68
69 // comma and space are valid delimites
70 StringTokenizer st = new StringTokenizer(str, ", ");
71 while (st.hasMoreTokens()) {
72 String s = st.nextToken();
73 if (!ll.contains(s)) {
74 ll.add(s);
75 }
76 }
77 return ll;
78 }
79
80 // Load DNS configuration from OS
81
82 private void loadConfig() {
83 assert Thread.holdsLock(lock);
84
85 // if address have changed then DNS probably changed aswell;
86 // otherwise check if cached settings have expired.
87 //
88 if (changed) {
89 changed = false;
90 } else {
91 if (lastRefresh >= 0) {
92 long currTime = System.currentTimeMillis();
93 if ((currTime - lastRefresh) < TIMEOUT) {
94 return;
95 }
96 }
97 }
98
99 // load DNS configuration, update timestamp, create
100 // new HashMaps from the loaded configuration
101 //
102 loadDNSconfig0();
103
104 lastRefresh = System.currentTimeMillis();
105 searchlist = stringToList(os_searchlist);
106 nameservers = stringToList(os_nameservers);
107 os_searchlist = null; // can be GC'ed
108 os_nameservers = null;
109 }
110
111 ResolverConfigurationImpl() {
112 opts = new OptionsImpl();
113 }
114
115 public List searchlist() {
116 synchronized (lock) {
117 loadConfig();
118
119 // List is mutable so return a shallow copy
120 return (List)searchlist.clone();
121 }
122 }
123
124 public List nameservers() {
125 synchronized (lock) {
126 loadConfig();
127
128 // List is mutable so return a shallow copy
129 return (List)nameservers.clone();
130 }
131 }
132
133 public Options options() {
134 return opts;
135 }
136
137 // --- Address Change Listener
138
139 static class AddressChangeListener extends Thread {
140 public void run() {
141 for (;;) {
142 // wait for configuration to change
143 if (notifyAddrChange0() != 0)
144 return;
145 synchronized (lock) {
146 changed = true;
147 }
148 }
149 }
150 }
151
152
153 // --- Native methods --
154
155 static native void init0();
156
157 static native void loadDNSconfig0();
158
159 static native int notifyAddrChange0();
160
161 static {
162 java.security.AccessController.doPrivileged(
163 new sun.security.action.LoadLibraryAction("net"));
164 init0();
165
166 // start the address listener thread
167 AddressChangeListener thr = new AddressChangeListener();
168 thr.setDaemon(true);
169 thr.start();
170 }
171 }
172
173 /**
174 * Implementation of {@link ResolverConfiguration.Options}
175 */
176 class OptionsImpl extends ResolverConfiguration.Options {
177 }