1 /*
2 * Copyright (c) 2002, 2011, 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.BufferedReader;
32 import java.io.FileReader;
33 import java.io.IOException;
34
35 /*
36 * An implementation of ResolverConfiguration for Solaris
37 * and Linux.
38 */
39
40 public class ResolverConfigurationImpl
41 extends ResolverConfiguration
42 {
43 // Lock helds whilst loading configuration or checking
44 private static Object lock = new Object();
45
46 // Time of last refresh.
47 private static long lastRefresh = -1;
48
49 // Cache timeout (300 seconds) - should be converted into property
50 // or configured as preference in the future.
51 private static final int TIMEOUT = 300000;
52
53 // Resolver options
54 private final Options opts;
55
56 // Parse /etc/resolv.conf to get the values for a particular
57 // keyword.
58 //
59 private LinkedList<String> resolvconf(String keyword,
60 int maxperkeyword,
61 int maxkeywords)
62 {
63 LinkedList<String> ll = new LinkedList<String>();
64
65 try {
66 BufferedReader in =
67 new BufferedReader(new FileReader("/etc/resolv.conf"));
68 String line;
69 while ((line = in.readLine()) != null) {
70 int maxvalues = maxperkeyword;
71 if (line.length() == 0)
72 continue;
73 if (line.charAt(0) == '#' || line.charAt(0) == ';')
74 continue;
75 if (!line.startsWith(keyword))
76 continue;
77 String value = line.substring(keyword.length());
78 if (value.length() == 0)
79 continue;
80 if (value.charAt(0) != ' ' && value.charAt(0) != '\t')
81 continue;
82 StringTokenizer st = new StringTokenizer(value, " \t");
83 while (st.hasMoreTokens()) {
84 String val = st.nextToken();
85 if (val.charAt(0) == '#' || val.charAt(0) == ';') {
86 break;
87 }
88 ll.add(val);
89 if (--maxvalues == 0) {
90 break;
91 }
92 }
93 if (--maxkeywords == 0) {
94 break;
95 }
96 }
97 in.close();
98 } catch (IOException ioe) {
99 // problem reading value
100 }
101
102 return ll;
103 }
104
105 private LinkedList<String> searchlist;
106 private LinkedList<String> nameservers;
107
108
109 // Load DNS configuration from OS
110
111 private void loadConfig() {
112 assert Thread.holdsLock(lock);
113
114 // check if cached settings have expired.
115 if (lastRefresh >= 0) {
116 long currTime = System.currentTimeMillis();
117 if ((currTime - lastRefresh) < TIMEOUT) {
118 return;
119 }
120 }
121
122 // get the name servers from /etc/resolv.conf
123 nameservers =
124 java.security.AccessController.doPrivileged(
125 new java.security.PrivilegedAction<LinkedList<String>>() {
126 public LinkedList<String> run() {
127 // typically MAXNS is 3 but we've picked 5 here
128 // to allow for additional servers if required.
129 return resolvconf("nameserver", 1, 5);
130 } /* run */
131 });
132
133 // get the search list (or domain)
134 searchlist = getSearchList();
135
136 // update the timestamp on the configuration
137 lastRefresh = System.currentTimeMillis();
138 }
139
140
141 // obtain search list or local domain
142
143 private LinkedList<String> getSearchList() {
144
145 LinkedList<String> sl;
146
147 // first try the search keyword in /etc/resolv.conf
148
149 sl = java.security.AccessController.doPrivileged(
150 new java.security.PrivilegedAction<LinkedList<String>>() {
151 public LinkedList<String> run() {
152 LinkedList<String> ll;
153
154 // first try search keyword (max 6 domains)
155 ll = resolvconf("search", 6, 1);
156 if (ll.size() > 0) {
157 return ll;
158 }
159
160 return null;
161
162 } /* run */
163
164 });
165 if (sl != null) {
166 return sl;
167 }
168
169 // No search keyword so use local domain
170
171
172 // LOCALDOMAIN has absolute priority on Solaris
173
174 String localDomain = localDomain0();
175 if (localDomain != null && localDomain.length() > 0) {
176 sl = new LinkedList<String>();
177 sl.add(localDomain);
178 return sl;
179 }
180
181 // try domain keyword in /etc/resolv.conf
182
183 sl = java.security.AccessController.doPrivileged(
184 new java.security.PrivilegedAction<LinkedList<String>>() {
185 public LinkedList<String> run() {
186 LinkedList<String> ll;
187
188 ll = resolvconf("domain", 1, 1);
189 if (ll.size() > 0) {
190 return ll;
191 }
192 return null;
193
194 } /* run */
195 });
196 if (sl != null) {
197 return sl;
198 }
199
200 // no local domain so try fallback (RPC) domain or
201 // hostName
202
203 sl = new LinkedList<String>();
204 String domain = fallbackDomain0();
205 if (domain != null && domain.length() > 0) {
206 sl.add(domain);
207 }
208
209 return sl;
210 }
211
212
213 // ----
214
215 ResolverConfigurationImpl() {
216 opts = new OptionsImpl();
217 }
218
219 @SuppressWarnings("unchecked")
220 public List<String> searchlist() {
221 synchronized (lock) {
222 loadConfig();
223
224 // List is mutable so return a shallow copy
225 return (List<String>)searchlist.clone();
226 }
227 }
228
229 @SuppressWarnings("unchecked")
230 public List<String> nameservers() {
231 synchronized (lock) {
232 loadConfig();
233
234 // List is mutable so return a shallow copy
235
236 return (List<String>)nameservers.clone();
237
238 }
239 }
240
241 public Options options() {
242 return opts;
243 }
244
245
246 // --- Native methods --
247
248 static native String localDomain0();
249
250 static native String fallbackDomain0();
251
252 static {
253 java.security.AccessController.doPrivileged(
254 new sun.security.action.LoadLibraryAction("net"));
255 }
256
257 }
258
259 /**
260 * Implementation of {@link ResolverConfiguration.Options}
261 */
262 class OptionsImpl extends ResolverConfiguration.Options {
263 }