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.net.UnknownHostException;
027 import java.nio.ByteBuffer;
028 import java.util.Arrays;
029
030 import org.apache.directory.server.dhcp.DhcpException;
031 import org.apache.directory.server.dhcp.messages.DhcpMessage;
032 import org.apache.directory.server.dhcp.messages.HardwareAddress;
033 import org.apache.directory.server.dhcp.options.DhcpOption;
034 import org.apache.directory.server.dhcp.options.OptionsField;
035 import org.apache.directory.server.dhcp.options.dhcp.DhcpMessageType;
036 import org.apache.directory.server.dhcp.options.dhcp.UnrecognizedOption;
037 import org.apache.directory.server.i18n.I18n;
038
039
040 /**
041 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
042 * @version $Rev: 902331 $, $Date: 2010-01-23 03:41:35 +0200 (Sat, 23 Jan 2010) $
043 */
044 public class DhcpMessageDecoder
045 {
046
047 /**
048 * Convert a byte buffer into a DhcpMessage.
049 *
050 * @return a DhcpMessage.
051 * @param buffer ByteBuffer to convert to a DhcpMessage object
052 * @throws DhcpException
053 */
054 public DhcpMessage decode( ByteBuffer buffer ) throws DhcpException
055 {
056 byte op = buffer.get();
057
058 short htype = ( short ) ( buffer.get() & 0xff );
059 short hlen = ( short ) ( buffer.get() & 0xff );
060 short hops = ( short ) ( buffer.get() & 0xff );
061 int xid = buffer.getInt();
062 int secs = buffer.getShort() & 0xffff;
063 short flags = buffer.getShort();
064
065 InetAddress ciaddr = decodeAddress( buffer );
066 InetAddress yiaddr = decodeAddress( buffer );
067 InetAddress siaddr = decodeAddress( buffer );
068 InetAddress giaddr = decodeAddress( buffer );
069
070 byte[] chaddr = decodeBytes( buffer, 16 );
071
072 String sname = decodeString( buffer, 64 );
073 String file = decodeString( buffer, 128 );
074
075 OptionsField options = decodeOptions( buffer );
076
077 // message type option: may be null if option isn't set (BOOTP)
078 DhcpMessageType mto = ( DhcpMessageType ) options.get( DhcpMessageType.class );
079
080 return new DhcpMessage( null != mto ? mto.getType() : null, op, new HardwareAddress( htype, hlen, chaddr ),
081 hops, xid, secs, flags, ciaddr, yiaddr, siaddr, giaddr, sname, file, options );
082 }
083
084
085 /**
086 * @param buffer
087 * @param len
088 * @return
089 */
090 private static byte[] decodeBytes( ByteBuffer buffer, int len )
091 {
092 byte[] bytes = new byte[len];
093 buffer.get( bytes );
094 return bytes;
095 }
096
097
098 /**
099 * @param buffer
100 * @return
101 */
102 private static String decodeString( ByteBuffer buffer, int len )
103 {
104 byte[] bytes = new byte[len];
105 buffer.get( bytes );
106
107 // find zero-terminator
108 int slen = 0;
109 while ( bytes[slen] != 0 )
110 slen++;
111
112 try
113 {
114 return new String( bytes, 0, slen, "ASCII" );
115 }
116 catch ( UnsupportedEncodingException e )
117 {
118 throw new RuntimeException( I18n.err( I18n.ERR_635 ), e );
119 }
120 }
121
122
123 /**
124 * Read a 4-byte inet address from the buffer.
125 *
126 * @param buffer
127 * @return
128 * @throws UnknownHostException
129 */
130 private static InetAddress decodeAddress( ByteBuffer buffer )
131 {
132 byte[] addr = new byte[4];
133 buffer.get( addr );
134 try
135 {
136 return InetAddress.getByAddress( addr );
137 }
138 catch ( UnknownHostException e )
139 {
140 // should not happen
141 return null;
142 }
143 }
144
145 private static final byte[] VENDOR_MAGIC_COOKIE =
146 { ( byte ) 99, ( byte ) 130, ( byte ) 83, ( byte ) 99 };
147
148
149 public OptionsField decodeOptions( ByteBuffer message ) throws DhcpException
150 {
151 byte[] magicCookie = new byte[4];
152 message.get( magicCookie );
153
154 if ( !Arrays.equals( VENDOR_MAGIC_COOKIE, magicCookie ) )
155 {
156 throw new DhcpException( "Parse exception." );
157 }
158
159 byte code;
160 byte length;
161 byte value[];
162
163 OptionsField options = new OptionsField();
164
165 while ( true )
166 {
167 code = message.get();
168 if ( code == 0 ) // pad option
169 continue;
170
171 if ( code == -1 ) // end option
172 break;
173
174 length = message.get();
175 value = new byte[length];
176 message.get( value );
177
178 options.add( getOptionInstance( code, value ) );
179 }
180
181 return options;
182 }
183
184
185 private DhcpOption getOptionInstance( int tag, byte[] value ) throws DhcpException
186 {
187 try
188 {
189 Class c = DhcpOption.getClassByTag( tag );
190
191 DhcpOption o = null != c ? ( DhcpOption ) c.newInstance() : new UnrecognizedOption( ( byte ) tag );
192 o.setData( value );
193
194 return o;
195 }
196 catch ( Exception e )
197 {
198 throw new DhcpException( I18n.err( I18n.ERR_636, e.toString() ) );
199 }
200 }
201 }