1/*
2 * Copyright (c) 2000, 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
26package com.sun.jndi.dns;
27
28
29import 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
42class 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.  {@code zone} 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}
191