/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.directory.server.dns.io.decoder;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.directory.server.dns.messages.DnsMessage;
import org.apache.directory.server.dns.messages.DnsMessageModifier;
import org.apache.directory.server.dns.messages.MessageType;
import org.apache.directory.server.dns.messages.OpCode;
import org.apache.directory.server.dns.messages.QuestionRecord;
import org.apache.directory.server.dns.messages.RecordClass;
import org.apache.directory.server.dns.messages.RecordType;
import org.apache.directory.server.dns.messages.ResourceRecord;
import org.apache.directory.server.dns.messages.ResourceRecordImpl;
import org.apache.directory.server.dns.messages.ResponseCode;
import org.apache.directory.server.i18n.I18n;
import org.apache.mina.core.buffer.IoBuffer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A decoder for DNS messages. The primary usage of the DnsMessageDecoder is by
* calling the <code>decode(ByteBuffer)</code> method which will read the
* message from the incoming ByteBuffer and build a <code>DnsMessage</code>
* from it according to the DnsMessage encoding in RFC-1035.
*
* @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
* @version $Rev$, $Date$
*/
public class DnsMessageDecoder
{
private final Logger logger = LoggerFactory.getLogger( DnsMessageDecoder.class );
/**
* A Hashed Adapter mapping record types to their encoders.
*/
private static final Map<RecordType, RecordDecoder> DEFAULT_DECODERS;
static
{
Map<RecordType, RecordDecoder> map = new HashMap<RecordType, RecordDecoder>();
map.put( RecordType.A, new AddressRecordDecoder() );
map.put( RecordType.NS, new NameServerRecordDecoder() );
map.put( RecordType.MX, new MailExchangeRecordDecoder() );
map.put( RecordType.AAAA, new IPv6RecordDecoder() );
DEFAULT_DECODERS = Collections.unmodifiableMap( map );
}
/**
* Decode the {@link ByteBuffer} into a {@link DnsMessage}.
*
* @param in
* @return The {@link DnsMessage}.
* @throws IOException
*/
public DnsMessage decode( IoBuffer in ) throws IOException
{
DnsMessageModifier modifier = new DnsMessageModifier();
modifier.setTransactionId( in.getUnsignedShort() );
byte header = in.get();
modifier.setMessageType( decodeMessageType( header ) );
modifier.setOpCode( decodeOpCode( header ) );
modifier.setAuthoritativeAnswer( decodeAuthoritativeAnswer( header ) );
modifier.setTruncated( decodeTruncated( header ) );
modifier.setRecursionDesired( decodeRecursionDesired( header ) );
header = in.get();
modifier.setRecursionAvailable( decodeRecursionAvailable( header ) );
modifier.setResponseCode( decodeResponseCode( header ) );
short questionCount = in.getShort();
short answerCount = in.getShort();
short authorityCount = in.getShort();
short additionalCount = in.getShort();
logger.debug( "decoding {} question records", questionCount );
modifier.setQuestionRecords( getQuestions( in, questionCount ) );
logger.debug( "decoding {} answer records", answerCount );
modifier.setAnswerRecords( getRecords( in, answerCount ) );
logger.debug( "decoding {} authority records", authorityCount );
modifier.setAuthorityRecords( getRecords( in, authorityCount ) );
logger.debug( "decoding {} additional records", additionalCount );
modifier.setAdditionalRecords( getRecords( in, additionalCount ) );
return modifier.getDnsMessage();
}
private List<ResourceRecord> getRecords( IoBuffer byteBuffer, short recordCount ) throws IOException
{
List<ResourceRecord> records = new ArrayList<ResourceRecord>( recordCount );
for ( int ii = 0; ii < recordCount; ii++ )
{
String domainName = getDomainName( byteBuffer );
RecordType recordType = RecordType.convert( byteBuffer.getShort() );
RecordClass recordClass = RecordClass.convert( byteBuffer.getShort() );
int timeToLive = byteBuffer.getInt();
short dataLength = byteBuffer.getShort();
Map<String, Object> attributes = decode( byteBuffer, recordType, dataLength );
records.add( new ResourceRecordImpl( domainName, recordType, recordClass, timeToLive, attributes ) );
}
return records;
}
private Map<String, Object> decode( IoBuffer byteBuffer, RecordType type, short length ) throws IOException
{
RecordDecoder recordDecoder = DEFAULT_DECODERS.get( type );
if ( recordDecoder == null )
{
throw new IllegalArgumentException( I18n.err(I18n.ERR_600, type ) );
}
return recordDecoder.decode( byteBuffer, length );
}
private List<QuestionRecord> getQuestions( IoBuffer byteBuffer, short questionCount )
{
List<QuestionRecord> questions = new ArrayList<QuestionRecord>( questionCount );
for ( int ii = 0; ii < questionCount; ii++ )
{
String domainName = getDomainName( byteBuffer );
RecordType recordType = RecordType.convert( byteBuffer.getShort() );
RecordClass recordClass = RecordClass.convert( byteBuffer.getShort() );
questions.add( new QuestionRecord( domainName, recordType, recordClass ) );
}
return questions;
}
static String getDomainName( IoBuffer byteBuffer )
{
StringBuffer domainName = new StringBuffer();
recurseDomainName( byteBuffer, domainName );
return domainName.toString();
}
static void recurseDomainName( IoBuffer byteBuffer, StringBuffer domainName )
{
int length = byteBuffer.getUnsigned();
if ( isOffset( length ) )
{
int position = byteBuffer.getUnsigned();
int offset = length & ~( 0xc0 ) << 8;
int originalPosition = byteBuffer.position();
byteBuffer.position( position + offset );
recurseDomainName( byteBuffer, domainName );
byteBuffer.position( originalPosition );
}
else if ( isLabel( length ) )
{
int labelLength = length;
getLabel( byteBuffer, domainName, labelLength );
recurseDomainName( byteBuffer, domainName );
}
}
static boolean isOffset( int length )
{
return ( ( length & 0xc0 ) == 0xc0 );
}
static boolean isLabel( int length )
{
return ( length != 0 && ( length & 0xc0 ) == 0 );
}
static void getLabel( IoBuffer byteBuffer, StringBuffer domainName, int labelLength )
{
for ( int jj = 0; jj < labelLength; jj++ )
{
char character = ( char ) byteBuffer.get();
domainName.append( character );
}
if ( byteBuffer.get( byteBuffer.position() ) != 0 )
{
domainName.append( "." );
}
}
private MessageType decodeMessageType( byte header )
{
return MessageType.convert( ( byte ) ( ( header & 0x80 ) >>> 7 ) );
}
private OpCode decodeOpCode( byte header )
{
return OpCode.convert( ( byte ) ( ( header & 0x78 ) >>> 3 ) );
}
private boolean decodeAuthoritativeAnswer( byte header )
{
return ( ( header & 0x04 ) >>> 2 ) == 1;
}
private boolean decodeTruncated( byte header )
{
return ( ( header & 0x02 ) >>> 1 ) == 1;
}
private boolean decodeRecursionDesired( byte header )
{
return ( ( header & 0x01 ) ) == 1;
}
private boolean decodeRecursionAvailable( byte header )
{
return ( ( header & 0x80 ) >>> 7 ) == 1;
}
private ResponseCode decodeResponseCode( byte header )
{
return ResponseCode.convert( ( byte ) ( header & 0x0F ) );
}
}