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 java.lang.ref.SoftReference;
30import java.util.Date;
31import java.util.Vector;
32
33
34/**
35 * ZoneNode extends NameNode to represent a tree of the zones in the
36 * DNS namespace, along with any intermediate nodes between zones.
37 * A ZoneNode that represents a zone may be "populated" with a
38 * NameNode tree containing the zone's contents.
39 *
40 * <p> A populated zone's contents will be flagged as having expired after
41 * the time specified by the minimum TTL value in the zone's SOA record.
42 *
43 * <p> Since zone cuts aren't directly modeled by a tree of ZoneNodes,
44 * ZoneNode.isZoneCut() always returns false.
45 *
46 * <p> The synchronization strategy is documented in DnsContext.java.
47 *
48 * <p> The zone's contents are accessed via a soft reference, so its
49 * heap space may be reclaimed when necessary.  The zone may be
50 * repopulated later.
51 *
52 * @author Scott Seligman
53 */
54
55
56class ZoneNode extends NameNode {
57
58    private SoftReference<NameNode> contentsRef = null;   // the zone's namespace
59    private long serialNumber = -1;     // the zone data's serial number
60    private Date expiration = null;     // time when the zone's data expires
61
62    ZoneNode(String label) {
63        super(label);
64    }
65
66    protected NameNode newNameNode(String label) {
67        return new ZoneNode(label);
68    }
69
70    /*
71     * Clears the contents of this node.  If the node was flagged as
72     * expired, it remains so.
73     */
74    synchronized void depopulate() {
75        contentsRef = null;
76        serialNumber = -1;
77    }
78
79    /*
80     * Is this node currently populated?
81     */
82    synchronized boolean isPopulated() {
83        return (getContents() != null);
84    }
85
86    /*
87     * Returns the zone's contents, or null if the zone is not populated.
88     */
89    synchronized NameNode getContents() {
90        return (contentsRef != null)
91                ? contentsRef.get()
92                : null;
93    }
94
95    /*
96     * Has this zone's data expired?
97     */
98    synchronized boolean isExpired() {
99        return ((expiration != null) && expiration.before(new Date()));
100    }
101
102    /*
103     * Returns the deepest populated zone on the path specified by a
104     * fully-qualified domain name, or null if there is no populated
105     * zone on that path.  Note that a node may be depopulated after
106     * being returned.
107     */
108    ZoneNode getDeepestPopulated(DnsName fqdn) {
109        ZoneNode znode = this;
110        ZoneNode popNode = isPopulated() ? this : null;
111        for (int i = 1; i < fqdn.size(); i++) { //     "i=1" to skip root label
112            znode = (ZoneNode) znode.get(fqdn.getKey(i));
113            if (znode == null) {
114                break;
115            } else if (znode.isPopulated()) {
116                popNode = znode;
117            }
118        }
119        return popNode;
120    }
121
122    /*
123     * Populates (or repopulates) a zone given its own fully-qualified
124     * name and its resource records.  Returns the zone's new contents.
125     */
126    NameNode populate(DnsName zone, ResourceRecords rrs) {
127        // assert zone.get(0).equals("");               // zone has root label
128        // assert (zone.size() == (depth() + 1));       // +1 due to root label
129
130        NameNode newContents = new NameNode(null);
131
132        for (int i = 0; i < rrs.answer.size(); i++) {
133            ResourceRecord rr = rrs.answer.elementAt(i);
134            DnsName n = rr.getName();
135
136            // Ignore resource records whose names aren't within the zone's
137            // domain.  Also skip records of the zone's top node, since
138            // the zone's root NameNode is already in place.
139            if ((n.size() > zone.size()) && n.startsWith(zone)) {
140                NameNode nnode = newContents.add(n, zone.size());
141                if (rr.getType() == ResourceRecord.TYPE_NS) {
142                    nnode.setZoneCut(true);
143                }
144            }
145        }
146        // The zone's SOA record is the first record in the answer section.
147        ResourceRecord soa = rrs.answer.firstElement();
148        synchronized (this) {
149            contentsRef = new SoftReference<NameNode>(newContents);
150            serialNumber = getSerialNumber(soa);
151            setExpiration(getMinimumTtl(soa));
152            return newContents;
153        }
154    }
155
156    /*
157     * Set this zone's data to expire in {@code secsToExpiration} seconds.
158     */
159    private void setExpiration(long secsToExpiration) {
160        expiration = new Date(System.currentTimeMillis() +
161                              1000 * secsToExpiration);
162    }
163
164    /*
165     * Returns an SOA record's minimum TTL field.
166     */
167    private static long getMinimumTtl(ResourceRecord soa) {
168        String rdata = (String) soa.getRdata();
169        int pos = rdata.lastIndexOf(' ') + 1;
170        return Long.parseLong(rdata.substring(pos));
171    }
172
173    /*
174     * Compares this zone's serial number with that of an SOA record.
175     * Zone must be populated.
176     * Returns a negative, zero, or positive integer as this zone's
177     * serial number is less than, equal to, or greater than the SOA
178     * record's.
179     * See ResourceRecord.compareSerialNumbers() for a description of
180     * serial number arithmetic.
181     */
182    int compareSerialNumberTo(ResourceRecord soa) {
183        // assert isPopulated();
184        return ResourceRecord.compareSerialNumbers(serialNumber,
185                                                   getSerialNumber(soa));
186    }
187
188    /*
189     * Returns an SOA record's serial number.
190     */
191    private static long getSerialNumber(ResourceRecord soa) {
192        String rdata = (String) soa.getRdata();
193
194        // An SOA record ends with:  serial refresh retry expire minimum.
195        // Set "beg" to the space before serial, and "end" to the space after.
196        // We go "backward" to avoid dealing with escaped spaces in names.
197        int beg = rdata.length();
198        int end = -1;
199        for (int i = 0; i < 5; i++) {
200            end = beg;
201            beg = rdata.lastIndexOf(' ', end - 1);
202        }
203        return Long.parseLong(rdata.substring(beg + 1, end));
204    }
205}
206