1 /*
   2  * Copyright (c) 2000, 2001, 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.util.Vector;
  30 import javax.naming.*;
  31 
  32 
  33 /**
  34  * The ResourceRecords class represents the resource records in the
  35  * four sections of a DNS message.
  36  *
  37  * The additional records section is currently ignored.
  38  *
  39  * @author Scott Seligman
  40  */
  41 
  42 
  43 class ResourceRecords {
  44 
  45     // Four sections:  question, answer, authority, additional.
  46     // The question section is treated as being made up of (shortened)
  47     // resource records, although this isn't technically how it's defined.
  48     Vector<ResourceRecord> question = new Vector<>();
  49     Vector<ResourceRecord> answer = new Vector<>();
  50     Vector<ResourceRecord> authority = new Vector<>();
  51     Vector<ResourceRecord> additional = new Vector<>();
  52 
  53     /*
  54      * True if these resource records are from a zone transfer.  In
  55      * that case only answer records are read (as per
  56      * draft-ietf-dnsext-axfr-clarify-02.txt).  Also, the rdata of
  57      * those answer records is not decoded (for efficiency) except
  58      * for SOA records.
  59      */
  60     boolean zoneXfer;
  61 
  62     /*
  63      * Returns a representation of the resource records in a DNS message.
  64      * Does not modify or store a reference to the msg array.
  65      */
  66     ResourceRecords(byte[] msg, int msgLen, Header hdr, boolean zoneXfer)
  67             throws NamingException {
  68         if (zoneXfer) {
  69             answer.ensureCapacity(8192);        // an arbitrary "large" number
  70         }
  71         this.zoneXfer = zoneXfer;
  72         add(msg, msgLen, hdr);
  73     }
  74 
  75     /*
  76      * Returns the type field of the first answer record, or -1 if
  77      * there are no answer records.
  78      */
  79     int getFirstAnsType() {
  80         if (answer.size() == 0) {
  81             return -1;
  82         }
  83         return answer.firstElement().getType();
  84     }
  85 
  86     /*
  87      * Returns the type field of the last answer record, or -1 if
  88      * there are no answer records.
  89      */
  90     int getLastAnsType() {
  91         if (answer.size() == 0) {
  92             return -1;
  93         }
  94         return answer.lastElement().getType();
  95     }
  96 
  97     /*
  98      * Decodes the resource records in a DNS message and adds
  99      * them to this object.
 100      * Does not modify or store a reference to the msg array.
 101      */
 102     void add(byte[] msg, int msgLen, Header hdr) throws NamingException {
 103 
 104         ResourceRecord rr;
 105         int pos = Header.HEADER_SIZE;   // current offset into msg
 106 
 107         try {
 108             for (int i = 0; i < hdr.numQuestions; i++) {
 109                 rr = new ResourceRecord(msg, msgLen, pos, true, false);
 110                 if (!zoneXfer) {
 111                     question.addElement(rr);
 112                 }
 113                 pos += rr.size();
 114             }
 115 
 116             for (int i = 0; i < hdr.numAnswers; i++) {
 117                 rr = new ResourceRecord(
 118                         msg, msgLen, pos, false, !zoneXfer);
 119                 answer.addElement(rr);
 120                 pos += rr.size();
 121             }
 122 
 123             if (zoneXfer) {
 124                 return;
 125             }
 126 
 127             for (int i = 0; i < hdr.numAuthorities; i++) {
 128                 rr = new ResourceRecord(msg, msgLen, pos, false, true);
 129                 authority.addElement(rr);
 130                 pos += rr.size();
 131             }
 132 
 133             // The additional records section is currently ignored.
 134 
 135         } catch (IndexOutOfBoundsException e) {
 136             throw new CommunicationException(
 137                     "DNS error: corrupted message");
 138         }
 139     }
 140 }