1 /*

     2  * Copyright (c) 2019, 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 jdk.dns.client.internal;

    27 

    28 import jdk.dns.client.ex.DnsResolverException;

    29 

    30 import java.util.Vector;

    31 

    32 

    33 /**

    34  * The ResourceRecords class represents the resource records in the

    35  * four sections of a DNS message.

    36  * <p>

    37  * The additional records section is currently ignored.

    38  *

    39  * @author Scott Seligman

    40  */

    41 

    42 

    43 public 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     public Vector<ResourceRecord> answer = new Vector<>();

    50     Vector<ResourceRecord> authority = new Vector<>();

    51     // TODO: Try to reuse additional section to avoid additional CNAME lookups

    52     public Vector<ResourceRecord> additional = new Vector<>();

    53 

    54 

    55     public boolean hasAddressOrAlias() {

    56         return answer.stream().anyMatch(

    57                 rr -> rr.rrtype == ResourceRecord.TYPE_A

    58                         || rr.rrtype == ResourceRecord.TYPE_AAAA

    59                         || rr.rrtype == ResourceRecord.TYPE_CNAME);

    60     }

    61 

    62     /*

    63      * True if these resource records are from a zone transfer.  In

    64      * that case only answer records are read (as per

    65      * draft-ietf-dnsext-axfr-clarify-02.txt).  Also, the rdata of

    66      * those answer records is not decoded (for efficiency) except

    67      * for SOA records.

    68      */

    69     boolean zoneXfer;

    70 

    71     /*

    72      * Returns a representation of the resource records in a DNS message.

    73      * Does not modify or store a reference to the msg array.

    74      */

    75     ResourceRecords(byte[] msg, int msgLen, Header hdr, boolean zoneXfer)

    76             throws DnsResolverException {

    77         if (zoneXfer) {

    78             answer.ensureCapacity(8192);        // an arbitrary "large" number

    79         }

    80         this.zoneXfer = zoneXfer;

    81         add(msg, msgLen, hdr);

    82     }

    83 

    84     /*

    85      * Returns the type field of the first answer record, or -1 if

    86      * there are no answer records.

    87      */

    88     int getFirstAnsType() {

    89         if (answer.size() == 0) {

    90             return -1;

    91         }

    92         return answer.firstElement().getType();

    93     }

    94 

    95     /*

    96      * Returns the type field of the last answer record, or -1 if

    97      * there are no answer records.

    98      */

    99     int getLastAnsType() {

   100         if (answer.size() == 0) {

   101             return -1;

   102         }

   103         return answer.lastElement().getType();

   104     }

   105 

   106     /*

   107      * Decodes the resource records in a DNS message and adds

   108      * them to this object.

   109      * Does not modify or store a reference to the msg array.

   110      */

   111     void add(byte[] msg, int msgLen, Header hdr) throws DnsResolverException {

   112 

   113         ResourceRecord rr;

   114         int pos = Header.HEADER_SIZE;   // current offset into msg

   115 

   116         try {

   117             for (int i = 0; i < hdr.numQuestions; i++) {

   118                 rr = new ResourceRecord(msg, msgLen, pos, true, false);

   119                 if (!zoneXfer) {

   120                     question.addElement(rr);

   121                 }

   122                 pos += rr.size();

   123             }

   124 

   125             for (int i = 0; i < hdr.numAnswers; i++) {

   126                 rr = new ResourceRecord(

   127                         msg, msgLen, pos, false, !zoneXfer);

   128                 answer.addElement(rr);

   129                 pos += rr.size();

   130             }

   131 

   132             if (zoneXfer) {

   133                 return;

   134             }

   135 

   136             for (int i = 0; i < hdr.numAuthorities; i++) {

   137                 rr = new ResourceRecord(msg, msgLen, pos, false, true);

   138                 authority.addElement(rr);

   139                 pos += rr.size();

   140             }

   141 

   142             // TODO: Might be useful

   143             // The additional records section is currently ignored.

   144 //            for (int i = 0; i < hdr.numAdditionals; i++) {

   145 //                rr = new ResourceRecord(msg, msgLen, pos, false, true);

   146 //                additional.addElement(rr);

   147 //                pos += rr.size();

   148 //            }

   149 

   150         } catch (IndexOutOfBoundsException e) {

   151             throw new DnsResolverException(

   152                     "DNS error: corrupted message");

   153         }

   154     }

   155 }