Stan Chesnutt | 7da02ad | 2010-12-14 09:49:26 -0800 | [diff] [blame] | 1 | package android.net.dhcp; |
| 2 | |
| 3 | import android.util.Log; |
| 4 | |
| 5 | import java.io.UnsupportedEncodingException; |
| 6 | import java.net.InetAddress; |
| 7 | import java.net.UnknownHostException; |
| 8 | import java.nio.ByteBuffer; |
| 9 | import java.nio.ByteOrder; |
Elliott Hughes | d396a44 | 2013-06-28 16:24:48 -0700 | [diff] [blame] | 10 | import java.nio.charset.StandardCharsets; |
Stan Chesnutt | 7da02ad | 2010-12-14 09:49:26 -0800 | [diff] [blame] | 11 | import java.nio.ShortBuffer; |
| 12 | |
| 13 | import java.util.ArrayList; |
| 14 | import java.util.List; |
| 15 | |
| 16 | /** |
| 17 | * Defines basic data and operations needed to build and use packets for the |
| 18 | * DHCP protocol. Subclasses create the specific packets used at each |
| 19 | * stage of the negotiation. |
| 20 | */ |
| 21 | abstract class DhcpPacket { |
| 22 | protected static final String TAG = "DhcpPacket"; |
| 23 | |
| 24 | /** |
| 25 | * Packet encapsulations. |
| 26 | */ |
| 27 | public static final int ENCAP_L2 = 0; // EthernetII header included |
| 28 | public static final int ENCAP_L3 = 1; // IP/UDP header included |
| 29 | public static final int ENCAP_BOOTP = 2; // BOOTP contents only |
| 30 | |
| 31 | /** |
| 32 | * IP layer definitions. |
| 33 | */ |
| 34 | private static final byte IP_TYPE_UDP = (byte) 0x11; |
| 35 | |
| 36 | /** |
| 37 | * IP: Version 4, Header Length 20 bytes |
| 38 | */ |
| 39 | private static final byte IP_VERSION_HEADER_LEN = (byte) 0x45; |
| 40 | |
| 41 | /** |
| 42 | * IP: Flags 0, Fragment Offset 0, Don't Fragment |
| 43 | */ |
| 44 | private static final short IP_FLAGS_OFFSET = (short) 0x4000; |
| 45 | |
| 46 | /** |
| 47 | * IP: TOS |
| 48 | */ |
| 49 | private static final byte IP_TOS_LOWDELAY = (byte) 0x10; |
| 50 | |
| 51 | /** |
| 52 | * IP: TTL -- use default 64 from RFC1340 |
| 53 | */ |
| 54 | private static final byte IP_TTL = (byte) 0x40; |
| 55 | |
| 56 | /** |
| 57 | * The client DHCP port. |
| 58 | */ |
| 59 | static final short DHCP_CLIENT = (short) 68; |
| 60 | |
| 61 | /** |
| 62 | * The server DHCP port. |
| 63 | */ |
| 64 | static final short DHCP_SERVER = (short) 67; |
| 65 | |
| 66 | /** |
| 67 | * The message op code indicating a request from a client. |
| 68 | */ |
| 69 | protected static final byte DHCP_BOOTREQUEST = (byte) 1; |
| 70 | |
| 71 | /** |
| 72 | * The message op code indicating a response from the server. |
| 73 | */ |
| 74 | protected static final byte DHCP_BOOTREPLY = (byte) 2; |
| 75 | |
| 76 | /** |
| 77 | * The code type used to identify an Ethernet MAC address in the |
| 78 | * Client-ID field. |
| 79 | */ |
| 80 | protected static final byte CLIENT_ID_ETHER = (byte) 1; |
| 81 | |
| 82 | /** |
| 83 | * The maximum length of a packet that can be constructed. |
| 84 | */ |
| 85 | protected static final int MAX_LENGTH = 1500; |
| 86 | |
| 87 | /** |
| 88 | * DHCP Optional Type: DHCP Subnet Mask |
| 89 | */ |
| 90 | protected static final byte DHCP_SUBNET_MASK = 1; |
| 91 | protected InetAddress mSubnetMask; |
| 92 | |
| 93 | /** |
| 94 | * DHCP Optional Type: DHCP Router |
| 95 | */ |
| 96 | protected static final byte DHCP_ROUTER = 3; |
| 97 | protected InetAddress mGateway; |
| 98 | |
| 99 | /** |
| 100 | * DHCP Optional Type: DHCP DNS Server |
| 101 | */ |
| 102 | protected static final byte DHCP_DNS_SERVER = 6; |
| 103 | protected List<InetAddress> mDnsServers; |
| 104 | |
| 105 | /** |
| 106 | * DHCP Optional Type: DHCP Host Name |
| 107 | */ |
| 108 | protected static final byte DHCP_HOST_NAME = 12; |
| 109 | protected String mHostName; |
| 110 | |
| 111 | /** |
| 112 | * DHCP Optional Type: DHCP DOMAIN NAME |
| 113 | */ |
| 114 | protected static final byte DHCP_DOMAIN_NAME = 15; |
| 115 | protected String mDomainName; |
| 116 | |
| 117 | /** |
| 118 | * DHCP Optional Type: DHCP BROADCAST ADDRESS |
| 119 | */ |
| 120 | protected static final byte DHCP_BROADCAST_ADDRESS = 28; |
| 121 | protected InetAddress mBroadcastAddress; |
| 122 | |
| 123 | /** |
| 124 | * DHCP Optional Type: DHCP Requested IP Address |
| 125 | */ |
| 126 | protected static final byte DHCP_REQUESTED_IP = 50; |
| 127 | protected InetAddress mRequestedIp; |
| 128 | |
| 129 | /** |
| 130 | * DHCP Optional Type: DHCP Lease Time |
| 131 | */ |
| 132 | protected static final byte DHCP_LEASE_TIME = 51; |
| 133 | protected Integer mLeaseTime; |
| 134 | |
| 135 | /** |
| 136 | * DHCP Optional Type: DHCP Message Type |
| 137 | */ |
| 138 | protected static final byte DHCP_MESSAGE_TYPE = 53; |
| 139 | // the actual type values |
| 140 | protected static final byte DHCP_MESSAGE_TYPE_DISCOVER = 1; |
| 141 | protected static final byte DHCP_MESSAGE_TYPE_OFFER = 2; |
| 142 | protected static final byte DHCP_MESSAGE_TYPE_REQUEST = 3; |
| 143 | protected static final byte DHCP_MESSAGE_TYPE_DECLINE = 4; |
| 144 | protected static final byte DHCP_MESSAGE_TYPE_ACK = 5; |
| 145 | protected static final byte DHCP_MESSAGE_TYPE_NAK = 6; |
| 146 | protected static final byte DHCP_MESSAGE_TYPE_INFORM = 8; |
| 147 | |
| 148 | /** |
| 149 | * DHCP Optional Type: DHCP Server Identifier |
| 150 | */ |
| 151 | protected static final byte DHCP_SERVER_IDENTIFIER = 54; |
| 152 | protected InetAddress mServerIdentifier; |
| 153 | |
| 154 | /** |
| 155 | * DHCP Optional Type: DHCP Parameter List |
| 156 | */ |
| 157 | protected static final byte DHCP_PARAMETER_LIST = 55; |
| 158 | protected byte[] mRequestedParams; |
| 159 | |
| 160 | /** |
| 161 | * DHCP Optional Type: DHCP MESSAGE |
| 162 | */ |
| 163 | protected static final byte DHCP_MESSAGE = 56; |
| 164 | protected String mMessage; |
| 165 | |
| 166 | /** |
| 167 | * DHCP Optional Type: DHCP Renewal Time Value |
| 168 | */ |
| 169 | protected static final byte DHCP_RENEWAL_TIME = 58; |
| 170 | |
| 171 | /** |
| 172 | * DHCP Optional Type: Vendor Class Identifier |
| 173 | */ |
| 174 | protected static final byte DHCP_VENDOR_CLASS_ID = 60; |
| 175 | |
| 176 | /** |
| 177 | * DHCP Optional Type: DHCP Client Identifier |
| 178 | */ |
| 179 | protected static final byte DHCP_CLIENT_IDENTIFIER = 61; |
| 180 | |
| 181 | /** |
| 182 | * The transaction identifier used in this particular DHCP negotiation |
| 183 | */ |
| 184 | protected final int mTransId; |
| 185 | |
| 186 | /** |
| 187 | * The IP address of the client host. This address is typically |
| 188 | * proposed by the client (from an earlier DHCP negotiation) or |
| 189 | * supplied by the server. |
| 190 | */ |
| 191 | protected final InetAddress mClientIp; |
| 192 | protected final InetAddress mYourIp; |
| 193 | private final InetAddress mNextIp; |
| 194 | private final InetAddress mRelayIp; |
| 195 | |
| 196 | /** |
| 197 | * Does the client request a broadcast response? |
| 198 | */ |
| 199 | protected boolean mBroadcast; |
| 200 | |
| 201 | /** |
| 202 | * The six-octet MAC of the client. |
| 203 | */ |
| 204 | protected final byte[] mClientMac; |
| 205 | |
| 206 | /** |
| 207 | * Asks the packet object to signal the next operation in the DHCP |
| 208 | * protocol. The available actions are methods defined in the |
| 209 | * DhcpStateMachine interface. |
| 210 | */ |
| 211 | public abstract void doNextOp(DhcpStateMachine stateMachine); |
| 212 | |
| 213 | /** |
| 214 | * Asks the packet object to create a ByteBuffer serialization of |
| 215 | * the packet for transmission. |
| 216 | */ |
| 217 | public abstract ByteBuffer buildPacket(int encap, short destUdp, |
| 218 | short srcUdp); |
| 219 | |
| 220 | /** |
| 221 | * Allows the concrete class to fill in packet-type-specific details, |
| 222 | * typically optional parameters at the end of the packet. |
| 223 | */ |
| 224 | abstract void finishPacket(ByteBuffer buffer); |
| 225 | |
| 226 | protected DhcpPacket(int transId, InetAddress clientIp, InetAddress yourIp, |
| 227 | InetAddress nextIp, InetAddress relayIp, |
| 228 | byte[] clientMac, boolean broadcast) { |
| 229 | mTransId = transId; |
| 230 | mClientIp = clientIp; |
| 231 | mYourIp = yourIp; |
| 232 | mNextIp = nextIp; |
| 233 | mRelayIp = relayIp; |
| 234 | mClientMac = clientMac; |
| 235 | mBroadcast = broadcast; |
| 236 | } |
| 237 | |
| 238 | /** |
| 239 | * Returns the transaction ID. |
| 240 | */ |
| 241 | public int getTransactionId() { |
| 242 | return mTransId; |
| 243 | } |
| 244 | |
| 245 | /** |
| 246 | * Creates a new L3 packet (including IP header) containing the |
| 247 | * DHCP udp packet. This method relies upon the delegated method |
| 248 | * finishPacket() to insert the per-packet contents. |
| 249 | */ |
| 250 | protected void fillInPacket(int encap, InetAddress destIp, |
| 251 | InetAddress srcIp, short destUdp, short srcUdp, ByteBuffer buf, |
| 252 | byte requestCode, boolean broadcast) { |
| 253 | byte[] destIpArray = destIp.getAddress(); |
| 254 | byte[] srcIpArray = srcIp.getAddress(); |
| 255 | int ipLengthOffset = 0; |
| 256 | int ipChecksumOffset = 0; |
| 257 | int endIpHeader = 0; |
| 258 | int udpHeaderOffset = 0; |
| 259 | int udpLengthOffset = 0; |
| 260 | int udpChecksumOffset = 0; |
| 261 | |
| 262 | buf.clear(); |
| 263 | buf.order(ByteOrder.BIG_ENDIAN); |
| 264 | |
| 265 | // if a full IP packet needs to be generated, put the IP & UDP |
| 266 | // headers in place, and pre-populate with artificial values |
| 267 | // needed to seed the IP checksum. |
| 268 | if (encap == ENCAP_L3) { |
| 269 | // fake IP header, used in the IP-header checksum |
| 270 | buf.put(IP_VERSION_HEADER_LEN); |
| 271 | buf.put(IP_TOS_LOWDELAY); // tos: IPTOS_LOWDELAY |
| 272 | ipLengthOffset = buf.position(); |
| 273 | buf.putShort((short)0); // length |
| 274 | buf.putShort((short)0); // id |
| 275 | buf.putShort(IP_FLAGS_OFFSET); // ip offset: don't fragment |
| 276 | buf.put(IP_TTL); // TTL: use default 64 from RFC1340 |
| 277 | buf.put(IP_TYPE_UDP); |
| 278 | ipChecksumOffset = buf.position(); |
| 279 | buf.putShort((short) 0); // checksum |
| 280 | |
| 281 | buf.put(srcIpArray); |
| 282 | buf.put(destIpArray); |
| 283 | endIpHeader = buf.position(); |
| 284 | |
| 285 | // UDP header |
| 286 | udpHeaderOffset = buf.position(); |
| 287 | buf.putShort(srcUdp); |
| 288 | buf.putShort(destUdp); |
| 289 | udpLengthOffset = buf.position(); |
| 290 | buf.putShort((short) 0); // length |
| 291 | udpChecksumOffset = buf.position(); |
| 292 | buf.putShort((short) 0); // UDP checksum -- initially zero |
| 293 | } |
| 294 | |
| 295 | // DHCP payload |
| 296 | buf.put(requestCode); |
| 297 | buf.put((byte) 1); // Hardware Type: Ethernet |
| 298 | buf.put((byte) mClientMac.length); // Hardware Address Length |
| 299 | buf.put((byte) 0); // Hop Count |
| 300 | buf.putInt(mTransId); // Transaction ID |
| 301 | buf.putShort((short) 0); // Elapsed Seconds |
| 302 | |
| 303 | if (broadcast) { |
| 304 | buf.putShort((short) 0x8000); // Flags |
| 305 | } else { |
| 306 | buf.putShort((short) 0x0000); // Flags |
| 307 | } |
| 308 | |
| 309 | buf.put(mClientIp.getAddress()); |
| 310 | buf.put(mYourIp.getAddress()); |
| 311 | buf.put(mNextIp.getAddress()); |
| 312 | buf.put(mRelayIp.getAddress()); |
| 313 | buf.put(mClientMac); |
| 314 | buf.position(buf.position() + |
| 315 | (16 - mClientMac.length) // pad addr to 16 bytes |
| 316 | + 64 // empty server host name (64 bytes) |
| 317 | + 128); // empty boot file name (128 bytes) |
| 318 | buf.putInt(0x63825363); // magic number |
| 319 | finishPacket(buf); |
| 320 | |
| 321 | // round up to an even number of octets |
| 322 | if ((buf.position() & 1) == 1) { |
| 323 | buf.put((byte) 0); |
| 324 | } |
| 325 | |
| 326 | // If an IP packet is being built, the IP & UDP checksums must be |
| 327 | // computed. |
| 328 | if (encap == ENCAP_L3) { |
| 329 | // fix UDP header: insert length |
| 330 | short udpLen = (short)(buf.position() - udpHeaderOffset); |
| 331 | buf.putShort(udpLengthOffset, udpLen); |
| 332 | // fix UDP header: checksum |
| 333 | // checksum for UDP at udpChecksumOffset |
| 334 | int udpSeed = 0; |
| 335 | |
| 336 | // apply IPv4 pseudo-header. Read IP address src and destination |
| 337 | // values from the IP header and accumulate checksum. |
| 338 | udpSeed += intAbs(buf.getShort(ipChecksumOffset + 2)); |
| 339 | udpSeed += intAbs(buf.getShort(ipChecksumOffset + 4)); |
| 340 | udpSeed += intAbs(buf.getShort(ipChecksumOffset + 6)); |
| 341 | udpSeed += intAbs(buf.getShort(ipChecksumOffset + 8)); |
| 342 | |
| 343 | // accumulate extra data for the pseudo-header |
| 344 | udpSeed += IP_TYPE_UDP; |
| 345 | udpSeed += udpLen; |
| 346 | // and compute UDP checksum |
| 347 | buf.putShort(udpChecksumOffset, (short) checksum(buf, udpSeed, |
| 348 | udpHeaderOffset, |
| 349 | buf.position())); |
| 350 | // fix IP header: insert length |
| 351 | buf.putShort(ipLengthOffset, (short)buf.position()); |
| 352 | // fixup IP-header checksum |
| 353 | buf.putShort(ipChecksumOffset, |
| 354 | (short) checksum(buf, 0, 0, endIpHeader)); |
| 355 | } |
| 356 | } |
| 357 | |
| 358 | /** |
| 359 | * Converts a signed short value to an unsigned int value. Needed |
| 360 | * because Java does not have unsigned types. |
| 361 | */ |
| 362 | private int intAbs(short v) { |
| 363 | if (v < 0) { |
| 364 | int r = v + 65536; |
| 365 | return r; |
| 366 | } else { |
| 367 | return(v); |
| 368 | } |
| 369 | } |
| 370 | |
| 371 | /** |
| 372 | * Performs an IP checksum (used in IP header and across UDP |
| 373 | * payload) on the specified portion of a ByteBuffer. The seed |
| 374 | * allows the checksum to commence with a specified value. |
| 375 | */ |
| 376 | private int checksum(ByteBuffer buf, int seed, int start, int end) { |
| 377 | int sum = seed; |
| 378 | int bufPosition = buf.position(); |
| 379 | |
| 380 | // set position of original ByteBuffer, so that the ShortBuffer |
| 381 | // will be correctly initialized |
| 382 | buf.position(start); |
| 383 | ShortBuffer shortBuf = buf.asShortBuffer(); |
| 384 | |
| 385 | // re-set ByteBuffer position |
| 386 | buf.position(bufPosition); |
| 387 | |
| 388 | short[] shortArray = new short[(end - start) / 2]; |
| 389 | shortBuf.get(shortArray); |
| 390 | |
| 391 | for (short s : shortArray) { |
| 392 | sum += intAbs(s); |
| 393 | } |
| 394 | |
| 395 | start += shortArray.length * 2; |
| 396 | |
| 397 | // see if a singleton byte remains |
| 398 | if (end != start) { |
| 399 | short b = buf.get(start); |
| 400 | |
| 401 | // make it unsigned |
| 402 | if (b < 0) { |
| 403 | b += 256; |
| 404 | } |
| 405 | |
| 406 | sum += b * 256; |
| 407 | } |
| 408 | |
| 409 | sum = ((sum >> 16) & 0xFFFF) + (sum & 0xFFFF); |
| 410 | sum = ((sum + ((sum >> 16) & 0xFFFF)) & 0xFFFF); |
| 411 | int negated = ~sum; |
| 412 | return intAbs((short) negated); |
| 413 | } |
| 414 | |
| 415 | /** |
| 416 | * Adds an optional parameter containing a single byte value. |
| 417 | */ |
| 418 | protected void addTlv(ByteBuffer buf, byte type, byte value) { |
| 419 | buf.put(type); |
| 420 | buf.put((byte) 1); |
| 421 | buf.put(value); |
| 422 | } |
| 423 | |
| 424 | /** |
| 425 | * Adds an optional parameter containing an array of bytes. |
| 426 | */ |
| 427 | protected void addTlv(ByteBuffer buf, byte type, byte[] payload) { |
| 428 | if (payload != null) { |
| 429 | buf.put(type); |
| 430 | buf.put((byte) payload.length); |
| 431 | buf.put(payload); |
| 432 | } |
| 433 | } |
| 434 | |
| 435 | /** |
| 436 | * Adds an optional parameter containing an IP address. |
| 437 | */ |
| 438 | protected void addTlv(ByteBuffer buf, byte type, InetAddress addr) { |
| 439 | if (addr != null) { |
| 440 | addTlv(buf, type, addr.getAddress()); |
| 441 | } |
| 442 | } |
| 443 | |
| 444 | /** |
| 445 | * Adds an optional parameter containing a list of IP addresses. |
| 446 | */ |
| 447 | protected void addTlv(ByteBuffer buf, byte type, List<InetAddress> addrs) { |
| 448 | if (addrs != null && addrs.size() > 0) { |
| 449 | buf.put(type); |
| 450 | buf.put((byte)(4 * addrs.size())); |
| 451 | |
| 452 | for (InetAddress addr : addrs) { |
| 453 | buf.put(addr.getAddress()); |
| 454 | } |
| 455 | } |
| 456 | } |
| 457 | |
| 458 | /** |
| 459 | * Adds an optional parameter containing a simple integer |
| 460 | */ |
| 461 | protected void addTlv(ByteBuffer buf, byte type, Integer value) { |
| 462 | if (value != null) { |
| 463 | buf.put(type); |
| 464 | buf.put((byte) 4); |
| 465 | buf.putInt(value.intValue()); |
| 466 | } |
| 467 | } |
| 468 | |
| 469 | /** |
| 470 | * Adds an optional parameter containing and ASCII string. |
| 471 | */ |
| 472 | protected void addTlv(ByteBuffer buf, byte type, String str) { |
| 473 | if (str != null) { |
| 474 | buf.put(type); |
| 475 | buf.put((byte) str.length()); |
| 476 | |
| 477 | for (int i = 0; i < str.length(); i++) { |
| 478 | buf.put((byte) str.charAt(i)); |
| 479 | } |
| 480 | } |
| 481 | } |
| 482 | |
| 483 | /** |
| 484 | * Adds the special end-of-optional-parameters indicator. |
| 485 | */ |
| 486 | protected void addTlvEnd(ByteBuffer buf) { |
| 487 | buf.put((byte) 0xFF); |
| 488 | } |
| 489 | |
| 490 | /** |
| 491 | * Converts a MAC from an array of octets to an ASCII string. |
| 492 | */ |
| 493 | public static String macToString(byte[] mac) { |
| 494 | String macAddr = ""; |
| 495 | |
| 496 | for (int i = 0; i < mac.length; i++) { |
| 497 | String hexString = "0" + Integer.toHexString(mac[i]); |
| 498 | |
| 499 | // substring operation grabs the last 2 digits: this |
| 500 | // allows signed bytes to be converted correctly. |
| 501 | macAddr += hexString.substring(hexString.length() - 2); |
| 502 | |
| 503 | if (i != (mac.length - 1)) { |
| 504 | macAddr += ":"; |
| 505 | } |
| 506 | } |
| 507 | |
| 508 | return macAddr; |
| 509 | } |
| 510 | |
| 511 | public String toString() { |
| 512 | String macAddr = macToString(mClientMac); |
| 513 | |
| 514 | return macAddr; |
| 515 | } |
| 516 | |
| 517 | /** |
| 518 | * Reads a four-octet value from a ByteBuffer and construct |
| 519 | * an IPv4 address from that value. |
| 520 | */ |
| 521 | private static InetAddress readIpAddress(ByteBuffer packet) { |
| 522 | InetAddress result = null; |
| 523 | byte[] ipAddr = new byte[4]; |
| 524 | packet.get(ipAddr); |
| 525 | |
| 526 | try { |
| 527 | result = InetAddress.getByAddress(ipAddr); |
| 528 | } catch (UnknownHostException ex) { |
| 529 | // ipAddr is numeric, so this should not be |
| 530 | // triggered. However, if it is, just nullify |
| 531 | result = null; |
| 532 | } |
| 533 | |
| 534 | return result; |
| 535 | } |
| 536 | |
| 537 | /** |
| 538 | * Reads a string of specified length from the buffer. |
| 539 | */ |
| 540 | private static String readAsciiString(ByteBuffer buf, int byteCount) { |
| 541 | byte[] bytes = new byte[byteCount]; |
| 542 | buf.get(bytes); |
Elliott Hughes | d396a44 | 2013-06-28 16:24:48 -0700 | [diff] [blame] | 543 | return new String(bytes, 0, bytes.length, StandardCharsets.US_ASCII); |
Stan Chesnutt | 7da02ad | 2010-12-14 09:49:26 -0800 | [diff] [blame] | 544 | } |
| 545 | |
| 546 | /** |
| 547 | * Creates a concrete DhcpPacket from the supplied ByteBuffer. The |
| 548 | * buffer may have an L2 encapsulation (which is the full EthernetII |
| 549 | * format starting with the source-address MAC) or an L3 encapsulation |
| 550 | * (which starts with the IP header). |
| 551 | * <br> |
| 552 | * A subset of the optional parameters are parsed and are stored |
| 553 | * in object fields. |
| 554 | */ |
| 555 | public static DhcpPacket decodeFullPacket(ByteBuffer packet, int pktType) |
| 556 | { |
| 557 | // bootp parameters |
| 558 | int transactionId; |
| 559 | InetAddress clientIp; |
| 560 | InetAddress yourIp; |
| 561 | InetAddress nextIp; |
| 562 | InetAddress relayIp; |
| 563 | byte[] clientMac; |
Stan Chesnutt | 045b166 | 2011-02-02 12:10:21 -0800 | [diff] [blame] | 564 | List<InetAddress> dnsServers = new ArrayList<InetAddress>(); |
Stan Chesnutt | 7da02ad | 2010-12-14 09:49:26 -0800 | [diff] [blame] | 565 | InetAddress gateway = null; // aka router |
| 566 | Integer leaseTime = null; |
| 567 | InetAddress serverIdentifier = null; |
| 568 | InetAddress netMask = null; |
| 569 | String message = null; |
| 570 | String vendorId = null; |
| 571 | byte[] expectedParams = null; |
| 572 | String hostName = null; |
| 573 | String domainName = null; |
| 574 | InetAddress ipSrc = null; |
| 575 | InetAddress ipDst = null; |
| 576 | InetAddress bcAddr = null; |
| 577 | InetAddress requestedIp = null; |
| 578 | |
| 579 | // dhcp options |
| 580 | byte dhcpType = (byte) 0xFF; |
| 581 | |
| 582 | packet.order(ByteOrder.BIG_ENDIAN); |
| 583 | |
| 584 | // check to see if we need to parse L2, IP, and UDP encaps |
| 585 | if (pktType == ENCAP_L2) { |
| 586 | // System.out.println("buffer len " + packet.limit()); |
| 587 | byte[] l2dst = new byte[6]; |
| 588 | byte[] l2src = new byte[6]; |
| 589 | |
| 590 | packet.get(l2dst); |
| 591 | packet.get(l2src); |
| 592 | |
| 593 | short l2type = packet.getShort(); |
| 594 | |
| 595 | if (l2type != 0x0800) |
| 596 | return null; |
| 597 | } |
| 598 | |
| 599 | if ((pktType == ENCAP_L2) || (pktType == ENCAP_L3)) { |
| 600 | // assume l2type is 0x0800, i.e. IP |
| 601 | byte ipType = packet.get(); |
| 602 | // System.out.println("ipType is " + ipType); |
| 603 | byte ipDiffServicesField = packet.get(); |
| 604 | short ipTotalLength = packet.getShort(); |
| 605 | short ipIdentification = packet.getShort(); |
| 606 | byte ipFlags = packet.get(); |
| 607 | byte ipFragOffset = packet.get(); |
| 608 | byte ipTTL = packet.get(); |
| 609 | byte ipProto = packet.get(); |
| 610 | short ipChksm = packet.getShort(); |
| 611 | |
| 612 | ipSrc = readIpAddress(packet); |
| 613 | ipDst = readIpAddress(packet); |
| 614 | |
| 615 | if (ipProto != IP_TYPE_UDP) // UDP |
| 616 | return null; |
| 617 | |
| 618 | // assume UDP |
| 619 | short udpSrcPort = packet.getShort(); |
| 620 | short udpDstPort = packet.getShort(); |
| 621 | short udpLen = packet.getShort(); |
| 622 | short udpChkSum = packet.getShort(); |
| 623 | |
| 624 | if ((udpSrcPort != DHCP_SERVER) && (udpSrcPort != DHCP_CLIENT)) |
| 625 | return null; |
| 626 | } |
| 627 | |
| 628 | // assume bootp |
| 629 | byte type = packet.get(); |
| 630 | byte hwType = packet.get(); |
| 631 | byte addrLen = packet.get(); |
| 632 | byte hops = packet.get(); |
| 633 | transactionId = packet.getInt(); |
| 634 | short elapsed = packet.getShort(); |
| 635 | short bootpFlags = packet.getShort(); |
| 636 | boolean broadcast = (bootpFlags & 0x8000) != 0; |
| 637 | byte[] ipv4addr = new byte[4]; |
| 638 | |
| 639 | try { |
| 640 | packet.get(ipv4addr); |
| 641 | clientIp = InetAddress.getByAddress(ipv4addr); |
| 642 | packet.get(ipv4addr); |
| 643 | yourIp = InetAddress.getByAddress(ipv4addr); |
| 644 | packet.get(ipv4addr); |
| 645 | nextIp = InetAddress.getByAddress(ipv4addr); |
| 646 | packet.get(ipv4addr); |
| 647 | relayIp = InetAddress.getByAddress(ipv4addr); |
| 648 | } catch (UnknownHostException ex) { |
| 649 | return null; |
| 650 | } |
| 651 | |
| 652 | clientMac = new byte[addrLen]; |
| 653 | packet.get(clientMac); |
| 654 | |
| 655 | // skip over address padding (16 octets allocated) |
| 656 | packet.position(packet.position() + (16 - addrLen) |
| 657 | + 64 // skip server host name (64 chars) |
| 658 | + 128); // skip boot file name (128 chars) |
| 659 | |
| 660 | int dhcpMagicCookie = packet.getInt(); |
| 661 | |
| 662 | if (dhcpMagicCookie != 0x63825363) |
| 663 | return null; |
| 664 | |
| 665 | // parse options |
| 666 | boolean notFinishedOptions = true; |
| 667 | |
| 668 | while ((packet.position() < packet.limit()) && notFinishedOptions) { |
| 669 | byte optionType = packet.get(); |
| 670 | |
| 671 | if (optionType == (byte) 0xFF) { |
| 672 | notFinishedOptions = false; |
| 673 | } else { |
| 674 | byte optionLen = packet.get(); |
| 675 | int expectedLen = 0; |
| 676 | |
| 677 | switch(optionType) { |
| 678 | case DHCP_SUBNET_MASK: |
| 679 | netMask = readIpAddress(packet); |
| 680 | expectedLen = 4; |
| 681 | break; |
| 682 | case DHCP_ROUTER: |
| 683 | gateway = readIpAddress(packet); |
| 684 | expectedLen = 4; |
| 685 | break; |
| 686 | case DHCP_DNS_SERVER: |
Stan Chesnutt | 7da02ad | 2010-12-14 09:49:26 -0800 | [diff] [blame] | 687 | expectedLen = 0; |
| 688 | |
| 689 | for (expectedLen = 0; expectedLen < optionLen; |
| 690 | expectedLen += 4) { |
| 691 | dnsServers.add(readIpAddress(packet)); |
| 692 | } |
| 693 | break; |
| 694 | case DHCP_HOST_NAME: |
| 695 | expectedLen = optionLen; |
| 696 | hostName = readAsciiString(packet, optionLen); |
| 697 | break; |
| 698 | case DHCP_DOMAIN_NAME: |
| 699 | expectedLen = optionLen; |
| 700 | domainName = readAsciiString(packet, optionLen); |
| 701 | break; |
| 702 | case DHCP_BROADCAST_ADDRESS: |
| 703 | bcAddr = readIpAddress(packet); |
| 704 | expectedLen = 4; |
| 705 | break; |
| 706 | case DHCP_REQUESTED_IP: |
| 707 | requestedIp = readIpAddress(packet); |
| 708 | expectedLen = 4; |
| 709 | break; |
| 710 | case DHCP_LEASE_TIME: |
| 711 | leaseTime = Integer.valueOf(packet.getInt()); |
| 712 | expectedLen = 4; |
| 713 | break; |
| 714 | case DHCP_MESSAGE_TYPE: |
| 715 | dhcpType = packet.get(); |
| 716 | expectedLen = 1; |
| 717 | break; |
| 718 | case DHCP_SERVER_IDENTIFIER: |
| 719 | serverIdentifier = readIpAddress(packet); |
| 720 | expectedLen = 4; |
| 721 | break; |
| 722 | case DHCP_PARAMETER_LIST: |
| 723 | expectedParams = new byte[optionLen]; |
| 724 | packet.get(expectedParams); |
| 725 | expectedLen = optionLen; |
| 726 | break; |
| 727 | case DHCP_MESSAGE: |
| 728 | expectedLen = optionLen; |
| 729 | message = readAsciiString(packet, optionLen); |
| 730 | break; |
| 731 | case DHCP_VENDOR_CLASS_ID: |
| 732 | expectedLen = optionLen; |
| 733 | vendorId = readAsciiString(packet, optionLen); |
| 734 | break; |
| 735 | case DHCP_CLIENT_IDENTIFIER: { // Client identifier |
| 736 | byte[] id = new byte[optionLen]; |
| 737 | packet.get(id); |
| 738 | expectedLen = optionLen; |
| 739 | } break; |
| 740 | default: |
| 741 | // ignore any other parameters |
| 742 | for (int i = 0; i < optionLen; i++) { |
| 743 | expectedLen++; |
| 744 | byte throwaway = packet.get(); |
| 745 | } |
| 746 | } |
| 747 | |
| 748 | if (expectedLen != optionLen) { |
| 749 | return null; |
| 750 | } |
| 751 | } |
| 752 | } |
| 753 | |
| 754 | DhcpPacket newPacket; |
| 755 | |
| 756 | switch(dhcpType) { |
| 757 | case -1: return null; |
| 758 | case DHCP_MESSAGE_TYPE_DISCOVER: |
| 759 | newPacket = new DhcpDiscoverPacket( |
| 760 | transactionId, clientMac, broadcast); |
| 761 | break; |
| 762 | case DHCP_MESSAGE_TYPE_OFFER: |
| 763 | newPacket = new DhcpOfferPacket( |
| 764 | transactionId, broadcast, ipSrc, yourIp, clientMac); |
| 765 | break; |
| 766 | case DHCP_MESSAGE_TYPE_REQUEST: |
| 767 | newPacket = new DhcpRequestPacket( |
| 768 | transactionId, clientIp, clientMac, broadcast); |
| 769 | break; |
| 770 | case DHCP_MESSAGE_TYPE_DECLINE: |
| 771 | newPacket = new DhcpDeclinePacket( |
| 772 | transactionId, clientIp, yourIp, nextIp, relayIp, |
| 773 | clientMac); |
| 774 | break; |
| 775 | case DHCP_MESSAGE_TYPE_ACK: |
| 776 | newPacket = new DhcpAckPacket( |
| 777 | transactionId, broadcast, ipSrc, yourIp, clientMac); |
| 778 | break; |
| 779 | case DHCP_MESSAGE_TYPE_NAK: |
| 780 | newPacket = new DhcpNakPacket( |
| 781 | transactionId, clientIp, yourIp, nextIp, relayIp, |
| 782 | clientMac); |
| 783 | break; |
| 784 | case DHCP_MESSAGE_TYPE_INFORM: |
| 785 | newPacket = new DhcpInformPacket( |
| 786 | transactionId, clientIp, yourIp, nextIp, relayIp, |
| 787 | clientMac); |
| 788 | break; |
| 789 | default: |
| 790 | System.out.println("Unimplemented type: " + dhcpType); |
| 791 | return null; |
| 792 | } |
| 793 | |
| 794 | newPacket.mBroadcastAddress = bcAddr; |
| 795 | newPacket.mDnsServers = dnsServers; |
| 796 | newPacket.mDomainName = domainName; |
| 797 | newPacket.mGateway = gateway; |
| 798 | newPacket.mHostName = hostName; |
| 799 | newPacket.mLeaseTime = leaseTime; |
| 800 | newPacket.mMessage = message; |
| 801 | newPacket.mRequestedIp = requestedIp; |
| 802 | newPacket.mRequestedParams = expectedParams; |
| 803 | newPacket.mServerIdentifier = serverIdentifier; |
| 804 | newPacket.mSubnetMask = netMask; |
| 805 | return newPacket; |
| 806 | } |
| 807 | |
| 808 | /** |
| 809 | * Parse a packet from an array of bytes. |
| 810 | */ |
| 811 | public static DhcpPacket decodeFullPacket(byte[] packet, int pktType) |
| 812 | { |
| 813 | ByteBuffer buffer = ByteBuffer.wrap(packet).order(ByteOrder.BIG_ENDIAN); |
| 814 | return decodeFullPacket(buffer, pktType); |
| 815 | } |
| 816 | |
| 817 | /** |
| 818 | * Builds a DHCP-DISCOVER packet from the required specified |
| 819 | * parameters. |
| 820 | */ |
| 821 | public static ByteBuffer buildDiscoverPacket(int encap, int transactionId, |
| 822 | byte[] clientMac, boolean broadcast, byte[] expectedParams) { |
| 823 | DhcpPacket pkt = new DhcpDiscoverPacket( |
| 824 | transactionId, clientMac, broadcast); |
| 825 | pkt.mRequestedParams = expectedParams; |
| 826 | return pkt.buildPacket(encap, DHCP_SERVER, DHCP_CLIENT); |
| 827 | } |
| 828 | |
| 829 | /** |
| 830 | * Builds a DHCP-OFFER packet from the required specified |
| 831 | * parameters. |
| 832 | */ |
| 833 | public static ByteBuffer buildOfferPacket(int encap, int transactionId, |
| 834 | boolean broadcast, InetAddress serverIpAddr, InetAddress clientIpAddr, |
| 835 | byte[] mac, Integer timeout, InetAddress netMask, InetAddress bcAddr, |
| 836 | InetAddress gateway, List<InetAddress> dnsServers, |
| 837 | InetAddress dhcpServerIdentifier, String domainName) { |
| 838 | DhcpPacket pkt = new DhcpOfferPacket( |
| 839 | transactionId, broadcast, serverIpAddr, clientIpAddr, mac); |
| 840 | pkt.mGateway = gateway; |
| 841 | pkt.mDnsServers = dnsServers; |
| 842 | pkt.mLeaseTime = timeout; |
| 843 | pkt.mDomainName = domainName; |
| 844 | pkt.mServerIdentifier = dhcpServerIdentifier; |
| 845 | pkt.mSubnetMask = netMask; |
| 846 | pkt.mBroadcastAddress = bcAddr; |
| 847 | return pkt.buildPacket(encap, DHCP_CLIENT, DHCP_SERVER); |
| 848 | } |
| 849 | |
| 850 | /** |
| 851 | * Builds a DHCP-ACK packet from the required specified parameters. |
| 852 | */ |
| 853 | public static ByteBuffer buildAckPacket(int encap, int transactionId, |
| 854 | boolean broadcast, InetAddress serverIpAddr, InetAddress clientIpAddr, |
| 855 | byte[] mac, Integer timeout, InetAddress netMask, InetAddress bcAddr, |
| 856 | InetAddress gateway, List<InetAddress> dnsServers, |
| 857 | InetAddress dhcpServerIdentifier, String domainName) { |
| 858 | DhcpPacket pkt = new DhcpAckPacket( |
| 859 | transactionId, broadcast, serverIpAddr, clientIpAddr, mac); |
| 860 | pkt.mGateway = gateway; |
| 861 | pkt.mDnsServers = dnsServers; |
| 862 | pkt.mLeaseTime = timeout; |
| 863 | pkt.mDomainName = domainName; |
| 864 | pkt.mSubnetMask = netMask; |
| 865 | pkt.mServerIdentifier = dhcpServerIdentifier; |
| 866 | pkt.mBroadcastAddress = bcAddr; |
| 867 | return pkt.buildPacket(encap, DHCP_CLIENT, DHCP_SERVER); |
| 868 | } |
| 869 | |
| 870 | /** |
| 871 | * Builds a DHCP-NAK packet from the required specified parameters. |
| 872 | */ |
| 873 | public static ByteBuffer buildNakPacket(int encap, int transactionId, |
| 874 | InetAddress serverIpAddr, InetAddress clientIpAddr, byte[] mac) { |
| 875 | DhcpPacket pkt = new DhcpNakPacket(transactionId, clientIpAddr, |
| 876 | serverIpAddr, serverIpAddr, serverIpAddr, mac); |
| 877 | pkt.mMessage = "requested address not available"; |
| 878 | pkt.mRequestedIp = clientIpAddr; |
| 879 | return pkt.buildPacket(encap, DHCP_CLIENT, DHCP_SERVER); |
| 880 | } |
| 881 | |
| 882 | /** |
| 883 | * Builds a DHCP-REQUEST packet from the required specified parameters. |
| 884 | */ |
| 885 | public static ByteBuffer buildRequestPacket(int encap, |
| 886 | int transactionId, InetAddress clientIp, boolean broadcast, |
| 887 | byte[] clientMac, InetAddress requestedIpAddress, |
| 888 | InetAddress serverIdentifier, byte[] requestedParams, String hostName) { |
| 889 | DhcpPacket pkt = new DhcpRequestPacket(transactionId, clientIp, |
| 890 | clientMac, broadcast); |
| 891 | pkt.mRequestedIp = requestedIpAddress; |
| 892 | pkt.mServerIdentifier = serverIdentifier; |
| 893 | pkt.mHostName = hostName; |
| 894 | pkt.mRequestedParams = requestedParams; |
| 895 | ByteBuffer result = pkt.buildPacket(encap, DHCP_SERVER, DHCP_CLIENT); |
| 896 | return result; |
| 897 | } |
| 898 | } |