1 /*
2 * Copyright (c) 2000, 2007, 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 com.sun.jndi.dns;
27
28
29 import javax.naming.*;
30
31
32 /**
33 * The Resolver class performs DNS client operations in support of DnsContext.
34 *
35 * <p> Every DnsName instance passed to or returned from a method of
36 * this class should be fully-qualified and contain a root label (an
37 * empty component at position 0).
38 *
39 * @author Scott Seligman
40 */
41
42 class Resolver {
43
44 private DnsClient dnsClient;
45 private int timeout; // initial timeout on UDP queries in ms
46 private int retries; // number of UDP retries
47
48
49 /*
50 * Constructs a new Resolver given its servers and timeout parameters.
51 * Each server is of the form "server[:port]".
52 * IPv6 literal host names include delimiting brackets.
53 * There must be at least one server.
54 * "timeout" is the initial timeout interval (in ms) for UDP queries,
55 * and "retries" gives the number of retries per server.
56 */
57 Resolver(String[] servers, int timeout, int retries)
58 throws NamingException {
59 this.timeout = timeout;
60 this.retries = retries;
61 dnsClient = new DnsClient(servers, timeout, retries);
62 }
63
64 public void close() {
65 dnsClient.close();
66 dnsClient = null;
67 }
68
69
70 /*
71 * Queries resource records of a particular class and type for a
72 * given domain name.
73 * Useful values of rrclass are ResourceRecord.[Q]CLASS_xxx.
74 * Useful values of rrtype are ResourceRecord.[Q]TYPE_xxx.
75 * If recursion is true, recursion is requested on the query.
76 * If auth is true, only authoritative responses are accepted.
77 */
78 ResourceRecords query(DnsName fqdn, int rrclass, int rrtype,
79 boolean recursion, boolean auth)
80 throws NamingException {
81 return dnsClient.query(fqdn, rrclass, rrtype, recursion, auth);
82 }
83
84 /*
85 * Queries all resource records of a zone given its domain name and class.
86 * If recursion is true, recursion is requested on the query to find
87 * the name server (and also on the zone transfer, but it won't matter).
88 */
89 ResourceRecords queryZone(DnsName zone, int rrclass, boolean recursion)
90 throws NamingException {
91
92 DnsClient cl =
93 new DnsClient(findNameServers(zone, recursion), timeout, retries);
94 try {
95 return cl.queryZone(zone, rrclass, recursion);
96 } finally {
97 cl.close();
98 }
99 }
100
101 /*
102 * Finds the zone of a given domain name. The method is to look
103 * for the first SOA record on the path from the given domain to
104 * the root. This search may be partially bypassed if the zone's
105 * SOA record is received in the authority section of a response.
106 * If recursion is true, recursion is requested on any queries.
107 */
108 DnsName findZoneName(DnsName fqdn, int rrclass, boolean recursion)
109 throws NamingException {
110
111 fqdn = (DnsName) fqdn.clone();
112 while (fqdn.size() > 1) { // while below root
113 ResourceRecords rrs = null;
114 try {
115 rrs = query(fqdn, rrclass, ResourceRecord.TYPE_SOA,
116 recursion, false);
117 } catch (NameNotFoundException e) {
118 throw e;
119 } catch (NamingException e) {
120 // Ignore error and keep searching up the tree.
121 }
122 if (rrs != null) {
123 if (rrs.answer.size() > 0) { // found zone's SOA
124 return fqdn;
125 }
126 // Look for an SOA record giving the zone's top node.
127 for (int i = 0; i < rrs.authority.size(); i++) {
128 ResourceRecord rr = rrs.authority.elementAt(i);
129 if (rr.getType() == ResourceRecord.TYPE_SOA) {
130 DnsName zone = rr.getName();
131 if (fqdn.endsWith(zone)) {
132 return zone;
133 }
134 }
135 }
136 }
137 fqdn.remove(fqdn.size() - 1); // one step rootward
138 }
139 return fqdn; // no SOA found below root, so
140 // return root
141 }
142
143 /*
144 * Finds a zone's SOA record. Returns null if no SOA is found (in
145 * which case "zone" is not actually a zone).
146 * If recursion is true, recursion is requested on the query.
147 */
148 ResourceRecord findSoa(DnsName zone, int rrclass, boolean recursion)
149 throws NamingException {
150
151 ResourceRecords rrs = query(zone, rrclass, ResourceRecord.TYPE_SOA,
152 recursion, false);
153 for (int i = 0; i < rrs.answer.size(); i++) {
154 ResourceRecord rr = rrs.answer.elementAt(i);
155 if (rr.getType() == ResourceRecord.TYPE_SOA) {
156 return rr;
157 }
158 }
159 return null;
160 }
161
162 /*
163 * Finds the name servers of a zone. <tt>zone</tt> is a fully-qualified
164 * domain name at the top of a zone.
165 * If recursion is true, recursion is requested on the query.
166 */
167 private String[] findNameServers(DnsName zone, boolean recursion)
168 throws NamingException {
169
170 // %%% As an optimization, could look in authority section of
171 // findZoneName() response first.
172 ResourceRecords rrs =
173 query(zone, ResourceRecord.CLASS_INTERNET, ResourceRecord.TYPE_NS,
174 recursion, false);
175 String[] ns = new String[rrs.answer.size()];
176 for (int i = 0; i < ns.length; i++) {
177 ResourceRecord rr = rrs.answer.elementAt(i);
178 if (rr.getType() != ResourceRecord.TYPE_NS) {
179 throw new CommunicationException("Corrupted DNS message");
180 }
181 ns[i] = (String) rr.getRdata();
182
183 // Server name will be passed to InetAddress.getByName(), which
184 // may not be able to handle a trailing dot.
185 // assert ns[i].endsWith(".");
186 ns[i] = ns[i].substring(0, ns[i].length() - 1);
187 }
188 return ns;
189 }
190 }