1 /*
2 * Copyright (c) 2002, 2019, 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
32 /*
33 * An implementation of sun.net.ResolverConfiguration for Windows.
34 */
35
36 public class ResolverConfigurationImpl
37 extends ResolverConfiguration
38 {
39 // Lock held whilst loading configuration or checking
40 private static Object lock = new Object();
41
42 // Resolver options
43 private final Options opts;
44
45 // Addresses have changed
46 private static boolean changed = false;
47
48 // Time of last refresh.
49 private static long lastRefresh = -1;
50
51 // Cache timeout (120 seconds) - should be converted into property
52 // or configured as preference in the future.
53 private static final int TIMEOUT = 120000;
54
55 // DNS suffix list and name servers populated by native method
56 private static String os_searchlist;
57 private static String os_nameservers;
58
59 // Cached lists
60 private static LinkedList<String> searchlist;
61 private static LinkedList<String> nameservers;
62
63 // Parse string that consists of token delimited by space or commas
64 // and return LinkedHashMap
65 private LinkedList<String> stringToList(String str) {
66 LinkedList<String> ll = new LinkedList<>();
67
68 // comma and space are valid delimiters
69 StringTokenizer st = new StringTokenizer(str, ", ");
70 while (st.hasMoreTokens()) {
71 String s = st.nextToken();
72 if (!ll.contains(s)) {
73 ll.add(s);
74 }
75 }
76 return ll;
77 }
78
79 // Load DNS configuration from OS
80
81 private void loadConfig() {
82 assert Thread.holdsLock(lock);
83
84 // if address have changed then DNS probably changed as well;
85 // otherwise check if cached settings have expired.
86 //
87 if (changed) {
88 changed = false;
89 } else {
90 if (lastRefresh >= 0) {
91 long currTime = System.currentTimeMillis();
92 if ((currTime - lastRefresh) < TIMEOUT) {
93 return;
94 }
95 }
96 }
97
98 // load DNS configuration, update timestamp, create
99 // new HashMaps from the loaded configuration
100 //
101 loadDNSconfig0();
102
103 lastRefresh = System.currentTimeMillis();
104 searchlist = stringToList(os_searchlist);
105 nameservers = stringToList(os_nameservers);
106 os_searchlist = null; // can be GC'ed
107 os_nameservers = null;
108 }
109
110 ResolverConfigurationImpl() {
111 opts = new OptionsImpl();
112 }
113
114 @SuppressWarnings("unchecked") // clone()
115 public List<String> searchlist() {
116 synchronized (lock) {
117 loadConfig();
118
119 // List is mutable so return a shallow copy
120 return (List<String>)searchlist.clone();
121 }
122 }
123
124 @SuppressWarnings("unchecked") // clone()
125 public List<String> nameservers() {
126 synchronized (lock) {
127 loadConfig();
128
129 // List is mutable so return a shallow copy
130 return (List<String>)nameservers.clone();
131 }
132 }
133
134 public Options options() {
135 return opts;
136 }
137
138 // --- Address Change Listener
139
140 static class AddressChangeListener extends Thread {
141 public void run() {
142 for (;;) {
143 // wait for configuration to change
144 if (notifyAddrChange0() != 0)
145 return;
146 synchronized (lock) {
147 changed = true;
148 }
149 }
150 }
151 }
152
153
154 // --- Native methods --
155
156 static native void init0();
157
158 static native void loadDNSconfig0();
159
160 static native int notifyAddrChange0();
161
162 static {
163 jdk.internal.loader.BootLoader.loadLibrary("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 }