001    /*
002     *  Licensed to the Apache Software Foundation (ASF) under one
003     *  or more contributor license agreements.  See the NOTICE file
004     *  distributed with this work for additional information
005     *  regarding copyright ownership.  The ASF licenses this file
006     *  to you under the Apache License, Version 2.0 (the
007     *  "License"); you may not use this file except in compliance
008     *  with the License.  You may obtain a copy of the License at
009     * 
010     * http://www.apache.org/licenses/LICENSE-2.0
011     * 
012     *  Unless required by applicable law or agreed to in writing,
013     *  software distributed under the License is distributed on an
014     *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     *  KIND, either express or implied.  See the License for the
016     *  specific language governing permissions and limitations
017     *  under the License. 
018     * 
019     */
020    
021    package org.apache.directory.server.dhcp.io;
022    
023    
024    import java.io.UnsupportedEncodingException;
025    import java.net.InetAddress;
026    import java.nio.ByteBuffer;
027    import java.util.Iterator;
028    
029    import org.apache.directory.server.dhcp.messages.DhcpMessage;
030    import org.apache.directory.server.dhcp.messages.HardwareAddress;
031    import org.apache.directory.server.dhcp.options.DhcpOption;
032    import org.apache.directory.server.dhcp.options.OptionsField;
033    import org.apache.directory.server.dhcp.options.dhcp.DhcpMessageType;
034    import org.apache.directory.server.i18n.I18n;
035    
036    
037    /**
038     * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
039     * @version $Rev: 902331 $, $Date: 2010-01-23 02:41:35 +0100 (Sat, 23 Jan 2010) $
040     */
041    public class DhcpMessageEncoder
042    {
043        /**
044         * Converts a DhcpMessage object into a byte buffer.
045         * 
046         * @param byteBuffer ByteBuffer to put DhcpMessage into
047         * @param message DhcpMessage to encode into ByteBuffer
048         */
049        public void encode( ByteBuffer byteBuffer, DhcpMessage message )
050        {
051            byteBuffer.put( message.getOp() );
052    
053            HardwareAddress hardwareAddress = message.getHardwareAddress();
054    
055            byteBuffer.put( ( byte ) ( null != hardwareAddress ? hardwareAddress.getType() : 0 ) );
056            byteBuffer.put( ( byte ) ( null != hardwareAddress ? hardwareAddress.getLength() : 0 ) );
057            byteBuffer.put( ( byte ) message.getHopCount() );
058            byteBuffer.putInt( message.getTransactionId() );
059            byteBuffer.putShort( ( short ) message.getSeconds() );
060            byteBuffer.putShort( message.getFlags() );
061    
062            writeAddress( byteBuffer, message.getCurrentClientAddress() );
063            writeAddress( byteBuffer, message.getAssignedClientAddress() );
064            writeAddress( byteBuffer, message.getNextServerAddress() );
065            writeAddress( byteBuffer, message.getRelayAgentAddress() );
066    
067            writeBytes( byteBuffer, ( null != hardwareAddress ? hardwareAddress.getAddress() : new byte[]
068                {} ), 16 );
069    
070            writeString( byteBuffer, message.getServerHostname(), 64 );
071            writeString( byteBuffer, message.getBootFileName(), 128 );
072    
073            OptionsField options = message.getOptions();
074    
075            // update message type option (if set)
076            if ( null != message.getMessageType() )
077                options.add( new DhcpMessageType( message.getMessageType() ) );
078    
079            encodeOptions( options, byteBuffer );
080        }
081    
082    
083        /**
084         * Write a zero-terminated string to a field of len bytes.
085         * 
086         * @param byteBuffer
087         * @param serverHostname
088         * @param i
089         */
090        private void writeString( ByteBuffer byteBuffer, String string, int len )
091        {
092            if ( null == string )
093                string = "";
094    
095            try
096            {
097                byte sbytes[] = string.getBytes( "ASCII" );
098    
099                // writeBytes will automatically zero-pad and thus terminate the
100                // string.
101                writeBytes( byteBuffer, sbytes, len );
102            }
103            catch ( UnsupportedEncodingException e )
104            {
105                // should not happen
106                throw new RuntimeException( I18n.err( I18n.ERR_635 ), e );
107            }
108        }
109    
110    
111        /**
112         * Write an InetAddress to the byte buffer.
113         * 
114         * @param byteBuffer
115         * @param currentClientAddress
116         */
117        private void writeAddress( ByteBuffer byteBuffer, InetAddress currentClientAddress )
118        {
119            if ( null == currentClientAddress )
120            {
121                byte emptyAddress[] =
122                    { 0, 0, 0, 0 };
123                byteBuffer.put( emptyAddress );
124            }
125            else
126            {
127                byte[] addressBytes = currentClientAddress.getAddress();
128                byteBuffer.put( addressBytes );
129            }
130        }
131    
132    
133        /**
134         * Write an array of bytes to the buffer. Write exactly len bytes,
135         * truncating if more than len, padding if less than len bytes are
136         * available.
137         * 
138         * @param byteBuffer
139         * @param currentClientAddress
140         */
141        private void writeBytes( ByteBuffer byteBuffer, byte bytes[], int len )
142        {
143            if ( null == bytes )
144                bytes = new byte[]
145                    {};
146    
147            byteBuffer.put( bytes, 0, Math.min(len, bytes.length) );
148    
149            // pad as necessary
150            int remain = len - bytes.length;
151            while ( remain-- > 0 )
152                byteBuffer.put( ( byte ) 0 );
153        }
154    
155        private static final byte[] VENDOR_MAGIC_COOKIE =
156            { ( byte ) 99, ( byte ) 130, ( byte ) 83, ( byte ) 99 };
157    
158    
159        public void encodeOptions( OptionsField options, ByteBuffer message )
160        {
161            message.put( VENDOR_MAGIC_COOKIE );
162    
163            for ( Iterator i = options.iterator(); i.hasNext(); )
164            {
165                DhcpOption option = ( DhcpOption ) i.next();
166                option.writeTo( message );
167            }
168    
169            // add end option
170            message.put( ( byte ) 0xff );
171        }
172    }