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
26 package com.sun.jndi.dns;
27
28
29 import java.lang.ref.SoftReference;
30 import java.util.Date;
31 import 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
56 class 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).isEmpty(); // 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 }