1 /*
2 * Copyright (c) 2002, 2020, 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.ArrayList;
29 import java.util.List;
30 import java.util.concurrent.TimeUnit;
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. We default to true to make sure we
46 // resolve the first time it is requested.
47 private static boolean changed = true;
48
49 // Time of last refresh.
50 private static long lastRefresh;
51
52 // Cache timeout (120 seconds) - should be converted into property
53 // or configured as preference in the future.
54 private static final long TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(120);
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 ArrayList<String> searchlist;
62 private static ArrayList<String> nameservers;
63
64 // Parse string that consists of token delimited by comma
65 // and return ArrayList. Refer to ResolverConfigurationImpl.c and
66 // strappend to see how the string is created.
67 private ArrayList<String> stringToList(String str) {
68 // String is delimited by comma.
69 String[] tokens = str.split(",");
70 ArrayList<String> l = new ArrayList<>(tokens.length);
71 for (String s : tokens) {
72 if (!s.isEmpty() && !l.contains(s)) {
73 l.add(s);
74 }
75 }
76 l.trimToSize();
77 return l;
78 }
79
80 // Parse string that consists of token delimited by comma
81 // and return ArrayList. Refer to ResolverConfigurationImpl.c and
82 // strappend to see how the string is created.
83 // In addition to splitting the string, converts IPv6 addresses to
84 // BSD-style.
85 private ArrayList<String> addressesToList(String str) {
86 // String is delimited by comma
87 String[] tokens = str.split(",");
88 ArrayList<String> l = new ArrayList<>(tokens.length);
89
90 for (String s : tokens) {
91 if (!s.isEmpty()) {
92 if (s.indexOf(':') >= 0 && s.charAt(0) != '[') {
93 // Not BSD style
94 s = '[' + s + ']';
95 }
96 if (!s.isEmpty() && !l.contains(s)) {
97 l.add(s);
98 }
99 }
100 }
101 l.trimToSize();
102 return l;
103 }
104
105 // Load DNS configuration from OS
106
107 private void loadConfig() {
108 assert Thread.holdsLock(lock);
109
110 // A change in the network address of the machine usually indicates
111 // a change in DNS configuration too so we always refresh the config
112 // after such a change.
113 if (changed) {
114 changed = false;
115 } else {
116 // Otherwise we refresh if TIMEOUT_NANOS has passed since last
117 // load.
118 long currTime = System.nanoTime();
119 // lastRefresh will always have been set once because we start with
120 // changed = true.
121 if ((currTime - lastRefresh) < TIMEOUT_NANOS) {
122 return;
123 }
124 }
125
126 // Native code that uses Windows API to find out the DNS server
127 // addresses and search suffixes. It builds a comma-delimited string
128 // of nameservers and domain suffixes and sets them to the static
129 // os_nameservers and os_searchlist. We then split these into Java
130 // Lists here.
131 loadDNSconfig0();
132
133 // Record the time of update and refresh the lists of addresses /
134 // domain suffixes.
135 lastRefresh = System.nanoTime();
136 searchlist = stringToList(os_searchlist);
137 nameservers = addressesToList(os_nameservers);
138 os_searchlist = null; // can be GC'ed
139 os_nameservers = null;
140 }
141
142 ResolverConfigurationImpl() {
143 opts = new OptionsImpl();
144 }
145
146 @SuppressWarnings("unchecked") // clone()
147 public List<String> searchlist() {
148 synchronized (lock) {
149 loadConfig();
150
151 // List is mutable so return a shallow copy
152 return (List<String>)searchlist.clone();
153 }
154 }
155
156 @SuppressWarnings("unchecked") // clone()
157 public List<String> nameservers() {
158 synchronized (lock) {
159 loadConfig();
160
161 // List is mutable so return a shallow copy
162 return (List<String>)nameservers.clone();
163 }
164 }
165
166 public Options options() {
167 return opts;
168 }
169
170 // --- Address Change Listener
171
172 static class AddressChangeListener extends Thread {
173 public void run() {
174 for (;;) {
175 // wait for configuration to change
176 if (notifyAddrChange0() != 0)
177 return;
178 synchronized (lock) {
179 changed = true;
180 }
181 }
182 }
183 }
184
185
186 // --- Native methods --
187
188 static native void init0();
189
190 static native void loadDNSconfig0();
191
192 static native int notifyAddrChange0();
193
194 static {
195 jdk.internal.loader.BootLoader.loadLibrary("net");
196 init0();
197
198 // start the address listener thread
199 AddressChangeListener thr = new AddressChangeListener();
200 thr.setDaemon(true);
201 thr.start();
202 }
203 }
204
205 /**
206 * Implementation of {@link ResolverConfiguration.Options}
207 */
208 class OptionsImpl extends ResolverConfiguration.Options {
209 }