View Javadoc

1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  
21  package org.apache.directory.server.dns.protocol;
22  
23  
24  import org.apache.directory.server.dns.io.decoder.DnsMessageDecoder;
25  import org.apache.mina.common.BufferDataException;
26  import org.apache.mina.common.ByteBuffer;
27  import org.apache.mina.common.IoSession;
28  import org.apache.mina.filter.codec.CumulativeProtocolDecoder;
29  import org.apache.mina.filter.codec.ProtocolDecoderOutput;
30  
31  
32  /**
33   * A {@link CumulativeProtocolDecoder} which supports DNS operation over TCP,
34   * by reassembling split packets prior to decoding.
35   * 
36   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
37   * @version $Rev: 545041 $, $Date: 2007-06-06 20:31:34 -0700 (Wed, 06 Jun 2007) $
38   */
39  public class DnsTcpDecoder extends CumulativeProtocolDecoder
40  {
41      private DnsMessageDecoder decoder = new DnsMessageDecoder();
42  
43      private int maxObjectSize = 16384; // 16KB
44  
45  
46      /**
47       * Returns the allowed maximum size of the object to be decoded.
48       * If the size of the object to be decoded exceeds this value, this
49       * decoder will throw a {@link BufferDataException}.  The default
50       * value is <tt>16384</tt> (16KB).
51       * 
52       * @return The max object size.
53       */
54      public int getMaxObjectSize()
55      {
56          return maxObjectSize;
57      }
58  
59  
60      /**
61       * Sets the allowed maximum size of the object to be decoded.
62       * If the size of the object to be decoded exceeds this value, this
63       * decoder will throw a {@link BufferDataException}.  The default
64       * value is <tt>16384</tt> (16KB).
65       * 
66       * @param maxObjectSize 
67       */
68      public void setMaxObjectSize( int maxObjectSize )
69      {
70          if ( maxObjectSize <= 0 )
71          {
72              throw new IllegalArgumentException( "maxObjectSize: " + maxObjectSize );
73          }
74  
75          this.maxObjectSize = maxObjectSize;
76      }
77  
78  
79      @Override
80      protected boolean doDecode( IoSession session, ByteBuffer in, ProtocolDecoderOutput out ) throws Exception
81      {
82          if ( !in.prefixedDataAvailable( 2, maxObjectSize ) )
83          {
84              return false;
85          }
86  
87          in.getShort();
88  
89          out.write( decoder.decode( in ) );
90  
91          return true;
92      }
93  }