| 1 | /* |
| 2 | * Update: The Berkeley copyright was changed, and the change |
| 3 | * is retroactive to all "true" BSD software (ie everything |
| 4 | * from UCB as opposed to other peoples code that just carried |
| 5 | * the same license). The new copyright doesn't clash with the |
| 6 | * GPL, so the module-only restriction has been removed.. |
| 7 | */ |
| 8 | |
| 9 | /* Because this code is derived from the 4.3BSD compress source: |
| 10 | * |
| 11 | * Copyright (c) 1985, 1986 The Regents of the University of California. |
| 12 | * All rights reserved. |
| 13 | * |
| 14 | * This code is derived from software contributed to Berkeley by |
| 15 | * James A. Woods, derived from original work by Spencer Thomas |
| 16 | * and Joseph Orost. |
| 17 | * |
| 18 | * Redistribution and use in source and binary forms, with or without |
| 19 | * modification, are permitted provided that the following conditions |
| 20 | * are met: |
| 21 | * 1. Redistributions of source code must retain the above copyright |
| 22 | * notice, this list of conditions and the following disclaimer. |
| 23 | * 2. Redistributions in binary form must reproduce the above copyright |
| 24 | * notice, this list of conditions and the following disclaimer in the |
| 25 | * documentation and/or other materials provided with the distribution. |
| 26 | * 3. All advertising materials mentioning features or use of this software |
| 27 | * must display the following acknowledgement: |
| 28 | * This product includes software developed by the University of |
| 29 | * California, Berkeley and its contributors. |
| 30 | * 4. Neither the name of the University nor the names of its contributors |
| 31 | * may be used to endorse or promote products derived from this software |
| 32 | * without specific prior written permission. |
| 33 | * |
| 34 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 35 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 36 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 37 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 38 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 39 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 40 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 41 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 42 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 43 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 44 | * SUCH DAMAGE. |
| 45 | */ |
| 46 | |
| 47 | /* |
| 48 | * This version is for use with contiguous buffers on Linux-derived systems. |
| 49 | * |
| 50 | * ==FILEVERSION 20000226== |
| 51 | * |
| 52 | * NOTE TO MAINTAINERS: |
| 53 | * If you modify this file at all, please set the number above to the |
| 54 | * date of the modification as YYMMDD (year month day). |
| 55 | * bsd_comp.c is shipped with a PPP distribution as well as with |
| 56 | * the kernel; if everyone increases the FILEVERSION number above, |
| 57 | * then scripts can do the right thing when deciding whether to |
| 58 | * install a new bsd_comp.c file. Don't change the format of that |
| 59 | * line otherwise, so the installation script can recognize it. |
| 60 | * |
| 61 | * From: bsd_comp.c,v 1.3 1994/12/08 01:59:58 paulus Exp |
| 62 | */ |
| 63 | |
| 64 | #include <linux/module.h> |
| 65 | #include <linux/init.h> |
| 66 | #include <linux/slab.h> |
| 67 | #include <linux/vmalloc.h> |
| 68 | #include <linux/string.h> |
| 69 | |
| 70 | #include <linux/ppp_defs.h> |
| 71 | |
| 72 | #undef PACKETPTR |
| 73 | #define PACKETPTR 1 |
| 74 | #include <linux/ppp-comp.h> |
| 75 | #undef PACKETPTR |
| 76 | |
| 77 | #include <asm/byteorder.h> |
| 78 | |
| 79 | /* |
| 80 | * PPP "BSD compress" compression |
| 81 | * The differences between this compression and the classic BSD LZW |
| 82 | * source are obvious from the requirement that the classic code worked |
| 83 | * with files while this handles arbitrarily long streams that |
| 84 | * are broken into packets. They are: |
| 85 | * |
| 86 | * When the code size expands, a block of junk is not emitted by |
| 87 | * the compressor and not expected by the decompressor. |
| 88 | * |
| 89 | * New codes are not necessarily assigned every time an old |
| 90 | * code is output by the compressor. This is because a packet |
| 91 | * end forces a code to be emitted, but does not imply that a |
| 92 | * new sequence has been seen. |
| 93 | * |
| 94 | * The compression ratio is checked at the first end of a packet |
| 95 | * after the appropriate gap. Besides simplifying and speeding |
| 96 | * things up, this makes it more likely that the transmitter |
| 97 | * and receiver will agree when the dictionary is cleared when |
| 98 | * compression is not going well. |
| 99 | */ |
| 100 | |
| 101 | /* |
| 102 | * Macros to extract protocol version and number of bits |
| 103 | * from the third byte of the BSD Compress CCP configuration option. |
| 104 | */ |
| 105 | |
| 106 | #define BSD_VERSION(x) ((x) >> 5) |
| 107 | #define BSD_NBITS(x) ((x) & 0x1F) |
| 108 | |
| 109 | #define BSD_CURRENT_VERSION 1 |
| 110 | |
| 111 | /* |
| 112 | * A dictionary for doing BSD compress. |
| 113 | */ |
| 114 | |
| 115 | struct bsd_dict { |
| 116 | union { /* hash value */ |
| 117 | unsigned long fcode; |
| 118 | struct { |
| 119 | #if defined(__LITTLE_ENDIAN) /* Little endian order */ |
| 120 | unsigned short prefix; /* preceding code */ |
| 121 | unsigned char suffix; /* last character of new code */ |
| 122 | unsigned char pad; |
| 123 | #elif defined(__BIG_ENDIAN) /* Big endian order */ |
| 124 | unsigned char pad; |
| 125 | unsigned char suffix; /* last character of new code */ |
| 126 | unsigned short prefix; /* preceding code */ |
| 127 | #else |
| 128 | #error Endianness not defined... |
| 129 | #endif |
| 130 | } hs; |
| 131 | } f; |
| 132 | unsigned short codem1; /* output of hash table -1 */ |
| 133 | unsigned short cptr; /* map code to hash table entry */ |
| 134 | }; |
| 135 | |
| 136 | struct bsd_db { |
| 137 | int totlen; /* length of this structure */ |
| 138 | unsigned int hsize; /* size of the hash table */ |
| 139 | unsigned char hshift; /* used in hash function */ |
| 140 | unsigned char n_bits; /* current bits/code */ |
| 141 | unsigned char maxbits; /* maximum bits/code */ |
| 142 | unsigned char debug; /* non-zero if debug desired */ |
| 143 | unsigned char unit; /* ppp unit number */ |
| 144 | unsigned short seqno; /* sequence # of next packet */ |
| 145 | unsigned int mru; /* size of receive (decompress) bufr */ |
| 146 | unsigned int maxmaxcode; /* largest valid code */ |
| 147 | unsigned int max_ent; /* largest code in use */ |
| 148 | unsigned int in_count; /* uncompressed bytes, aged */ |
| 149 | unsigned int bytes_out; /* compressed bytes, aged */ |
| 150 | unsigned int ratio; /* recent compression ratio */ |
| 151 | unsigned int checkpoint; /* when to next check the ratio */ |
| 152 | unsigned int clear_count; /* times dictionary cleared */ |
| 153 | unsigned int incomp_count; /* incompressible packets */ |
| 154 | unsigned int incomp_bytes; /* incompressible bytes */ |
| 155 | unsigned int uncomp_count; /* uncompressed packets */ |
| 156 | unsigned int uncomp_bytes; /* uncompressed bytes */ |
| 157 | unsigned int comp_count; /* compressed packets */ |
| 158 | unsigned int comp_bytes; /* compressed bytes */ |
| 159 | unsigned short *lens; /* array of lengths of codes */ |
| 160 | struct bsd_dict *dict; /* dictionary */ |
| 161 | }; |
| 162 | |
| 163 | #define BSD_OVHD 2 /* BSD compress overhead/packet */ |
| 164 | #define MIN_BSD_BITS 9 |
| 165 | #define BSD_INIT_BITS MIN_BSD_BITS |
| 166 | #define MAX_BSD_BITS 15 |
| 167 | |
| 168 | static void bsd_free (void *state); |
| 169 | static void *bsd_alloc(unsigned char *options, int opt_len, int decomp); |
| 170 | static void *bsd_comp_alloc (unsigned char *options, int opt_len); |
| 171 | static void *bsd_decomp_alloc (unsigned char *options, int opt_len); |
| 172 | |
| 173 | static int bsd_init (void *db, unsigned char *options, |
| 174 | int opt_len, int unit, int debug, int decomp); |
| 175 | static int bsd_comp_init (void *state, unsigned char *options, |
| 176 | int opt_len, int unit, int opthdr, int debug); |
| 177 | static int bsd_decomp_init (void *state, unsigned char *options, |
| 178 | int opt_len, int unit, int opthdr, int mru, |
| 179 | int debug); |
| 180 | |
| 181 | static void bsd_reset (void *state); |
| 182 | static void bsd_comp_stats (void *state, struct compstat *stats); |
| 183 | |
| 184 | static int bsd_compress (void *state, unsigned char *rptr, |
| 185 | unsigned char *obuf, int isize, int osize); |
| 186 | static void bsd_incomp (void *state, unsigned char *ibuf, int icnt); |
| 187 | |
| 188 | static int bsd_decompress (void *state, unsigned char *ibuf, int isize, |
| 189 | unsigned char *obuf, int osize); |
| 190 | |
| 191 | /* These are in ppp_generic.c */ |
| 192 | extern int ppp_register_compressor (struct compressor *cp); |
| 193 | extern void ppp_unregister_compressor (struct compressor *cp); |
| 194 | |
| 195 | /* |
| 196 | * the next two codes should not be changed lightly, as they must not |
| 197 | * lie within the contiguous general code space. |
| 198 | */ |
| 199 | #define CLEAR 256 /* table clear output code */ |
| 200 | #define FIRST 257 /* first free entry */ |
| 201 | #define LAST 255 |
| 202 | |
| 203 | #define MAXCODE(b) ((1 << (b)) - 1) |
| 204 | #define BADCODEM1 MAXCODE(MAX_BSD_BITS); |
| 205 | |
| 206 | #define BSD_HASH(prefix,suffix,hshift) ((((unsigned long)(suffix))<<(hshift)) \ |
| 207 | ^ (unsigned long)(prefix)) |
| 208 | #define BSD_KEY(prefix,suffix) ((((unsigned long)(suffix)) << 16) \ |
| 209 | + (unsigned long)(prefix)) |
| 210 | |
| 211 | #define CHECK_GAP 10000 /* Ratio check interval */ |
| 212 | |
| 213 | #define RATIO_SCALE_LOG 8 |
| 214 | #define RATIO_SCALE (1<<RATIO_SCALE_LOG) |
| 215 | #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) |
| 216 | |
| 217 | /* |
| 218 | * clear the dictionary |
| 219 | */ |
| 220 | |
| 221 | static void |
| 222 | bsd_clear(struct bsd_db *db) |
| 223 | { |
| 224 | db->clear_count++; |
| 225 | db->max_ent = FIRST-1; |
| 226 | db->n_bits = BSD_INIT_BITS; |
| 227 | db->bytes_out = 0; |
| 228 | db->in_count = 0; |
| 229 | db->ratio = 0; |
| 230 | db->checkpoint = CHECK_GAP; |
| 231 | } |
| 232 | |
| 233 | /* |
| 234 | * If the dictionary is full, then see if it is time to reset it. |
| 235 | * |
| 236 | * Compute the compression ratio using fixed-point arithmetic |
| 237 | * with 8 fractional bits. |
| 238 | * |
| 239 | * Since we have an infinite stream instead of a single file, |
| 240 | * watch only the local compression ratio. |
| 241 | * |
| 242 | * Since both peers must reset the dictionary at the same time even in |
| 243 | * the absence of CLEAR codes (while packets are incompressible), they |
| 244 | * must compute the same ratio. |
| 245 | */ |
| 246 | |
| 247 | static int bsd_check (struct bsd_db *db) /* 1=output CLEAR */ |
| 248 | { |
| 249 | unsigned int new_ratio; |
| 250 | |
| 251 | if (db->in_count >= db->checkpoint) |
| 252 | { |
| 253 | /* age the ratio by limiting the size of the counts */ |
| 254 | if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX) |
| 255 | { |
| 256 | db->in_count -= (db->in_count >> 2); |
| 257 | db->bytes_out -= (db->bytes_out >> 2); |
| 258 | } |
| 259 | |
| 260 | db->checkpoint = db->in_count + CHECK_GAP; |
| 261 | |
| 262 | if (db->max_ent >= db->maxmaxcode) |
| 263 | { |
| 264 | /* Reset the dictionary only if the ratio is worse, |
| 265 | * or if it looks as if it has been poisoned |
| 266 | * by incompressible data. |
| 267 | * |
| 268 | * This does not overflow, because |
| 269 | * db->in_count <= RATIO_MAX. |
| 270 | */ |
| 271 | |
| 272 | new_ratio = db->in_count << RATIO_SCALE_LOG; |
| 273 | if (db->bytes_out != 0) |
| 274 | { |
| 275 | new_ratio /= db->bytes_out; |
| 276 | } |
| 277 | |
| 278 | if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) |
| 279 | { |
| 280 | bsd_clear (db); |
| 281 | return 1; |
| 282 | } |
| 283 | db->ratio = new_ratio; |
| 284 | } |
| 285 | } |
| 286 | return 0; |
| 287 | } |
| 288 | |
| 289 | /* |
| 290 | * Return statistics. |
| 291 | */ |
| 292 | |
| 293 | static void bsd_comp_stats (void *state, struct compstat *stats) |
| 294 | { |
| 295 | struct bsd_db *db = (struct bsd_db *) state; |
| 296 | |
| 297 | stats->unc_bytes = db->uncomp_bytes; |
| 298 | stats->unc_packets = db->uncomp_count; |
| 299 | stats->comp_bytes = db->comp_bytes; |
| 300 | stats->comp_packets = db->comp_count; |
| 301 | stats->inc_bytes = db->incomp_bytes; |
| 302 | stats->inc_packets = db->incomp_count; |
| 303 | stats->in_count = db->in_count; |
| 304 | stats->bytes_out = db->bytes_out; |
| 305 | } |
| 306 | |
| 307 | /* |
| 308 | * Reset state, as on a CCP ResetReq. |
| 309 | */ |
| 310 | |
| 311 | static void bsd_reset (void *state) |
| 312 | { |
| 313 | struct bsd_db *db = (struct bsd_db *) state; |
| 314 | |
| 315 | bsd_clear(db); |
| 316 | |
| 317 | db->seqno = 0; |
| 318 | db->clear_count = 0; |
| 319 | } |
| 320 | |
| 321 | /* |
| 322 | * Release the compression structure |
| 323 | */ |
| 324 | |
| 325 | static void bsd_free (void *state) |
| 326 | { |
| 327 | struct bsd_db *db = state; |
| 328 | |
| 329 | if (!db) |
| 330 | return; |
| 331 | |
| 332 | /* |
| 333 | * Release the dictionary |
| 334 | */ |
| 335 | vfree(db->dict); |
| 336 | db->dict = NULL; |
| 337 | /* |
| 338 | * Release the string buffer |
| 339 | */ |
| 340 | vfree(db->lens); |
| 341 | db->lens = NULL; |
| 342 | /* |
| 343 | * Finally release the structure itself. |
| 344 | */ |
| 345 | kfree(db); |
| 346 | } |
| 347 | |
| 348 | /* |
| 349 | * Allocate space for a (de) compressor. |
| 350 | */ |
| 351 | |
| 352 | static void *bsd_alloc (unsigned char *options, int opt_len, int decomp) |
| 353 | { |
| 354 | int bits; |
| 355 | unsigned int hsize, hshift, maxmaxcode; |
| 356 | struct bsd_db *db; |
| 357 | |
| 358 | if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3 |
| 359 | || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) |
| 360 | { |
| 361 | return NULL; |
| 362 | } |
| 363 | |
| 364 | bits = BSD_NBITS(options[2]); |
| 365 | |
| 366 | switch (bits) |
| 367 | { |
| 368 | case 9: /* needs 82152 for both directions */ |
| 369 | case 10: /* needs 84144 */ |
| 370 | case 11: /* needs 88240 */ |
| 371 | case 12: /* needs 96432 */ |
| 372 | hsize = 5003; |
| 373 | hshift = 4; |
| 374 | break; |
| 375 | case 13: /* needs 176784 */ |
| 376 | hsize = 9001; |
| 377 | hshift = 5; |
| 378 | break; |
| 379 | case 14: /* needs 353744 */ |
| 380 | hsize = 18013; |
| 381 | hshift = 6; |
| 382 | break; |
| 383 | case 15: /* needs 691440 */ |
| 384 | hsize = 35023; |
| 385 | hshift = 7; |
| 386 | break; |
| 387 | case 16: /* needs 1366160--far too much, */ |
| 388 | /* hsize = 69001; */ /* and 69001 is too big for cptr */ |
| 389 | /* hshift = 8; */ /* in struct bsd_db */ |
| 390 | /* break; */ |
| 391 | default: |
| 392 | return NULL; |
| 393 | } |
| 394 | /* |
| 395 | * Allocate the main control structure for this instance. |
| 396 | */ |
| 397 | maxmaxcode = MAXCODE(bits); |
| 398 | db = kzalloc(sizeof (struct bsd_db), |
| 399 | GFP_KERNEL); |
| 400 | if (!db) |
| 401 | { |
| 402 | return NULL; |
| 403 | } |
| 404 | |
| 405 | /* |
| 406 | * Allocate space for the dictionary. This may be more than one page in |
| 407 | * length. |
| 408 | */ |
| 409 | db->dict = vmalloc(hsize * sizeof(struct bsd_dict)); |
| 410 | if (!db->dict) |
| 411 | { |
| 412 | bsd_free (db); |
| 413 | return NULL; |
| 414 | } |
| 415 | |
| 416 | /* |
| 417 | * If this is the compression buffer then there is no length data. |
| 418 | */ |
| 419 | if (!decomp) |
| 420 | { |
| 421 | db->lens = NULL; |
| 422 | } |
| 423 | /* |
| 424 | * For decompression, the length information is needed as well. |
| 425 | */ |
| 426 | else |
| 427 | { |
| 428 | db->lens = vmalloc((maxmaxcode + 1) * sizeof(db->lens[0])); |
| 429 | if (!db->lens) |
| 430 | { |
| 431 | bsd_free (db); |
| 432 | return (NULL); |
| 433 | } |
| 434 | } |
| 435 | /* |
| 436 | * Initialize the data information for the compression code |
| 437 | */ |
| 438 | db->totlen = sizeof (struct bsd_db) + |
| 439 | (sizeof (struct bsd_dict) * hsize); |
| 440 | |
| 441 | db->hsize = hsize; |
| 442 | db->hshift = hshift; |
| 443 | db->maxmaxcode = maxmaxcode; |
| 444 | db->maxbits = bits; |
| 445 | |
| 446 | return (void *) db; |
| 447 | } |
| 448 | |
| 449 | static void *bsd_comp_alloc (unsigned char *options, int opt_len) |
| 450 | { |
| 451 | return bsd_alloc (options, opt_len, 0); |
| 452 | } |
| 453 | |
| 454 | static void *bsd_decomp_alloc (unsigned char *options, int opt_len) |
| 455 | { |
| 456 | return bsd_alloc (options, opt_len, 1); |
| 457 | } |
| 458 | |
| 459 | /* |
| 460 | * Initialize the database. |
| 461 | */ |
| 462 | |
| 463 | static int bsd_init (void *state, unsigned char *options, |
| 464 | int opt_len, int unit, int debug, int decomp) |
| 465 | { |
| 466 | struct bsd_db *db = state; |
| 467 | int indx; |
| 468 | |
| 469 | if ((opt_len != 3) || (options[0] != CI_BSD_COMPRESS) || (options[1] != 3) |
| 470 | || (BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) |
| 471 | || (BSD_NBITS(options[2]) != db->maxbits) |
| 472 | || (decomp && db->lens == NULL)) |
| 473 | { |
| 474 | return 0; |
| 475 | } |
| 476 | |
| 477 | if (decomp) |
| 478 | { |
| 479 | indx = LAST; |
| 480 | do |
| 481 | { |
| 482 | db->lens[indx] = 1; |
| 483 | } |
| 484 | while (indx-- > 0); |
| 485 | } |
| 486 | |
| 487 | indx = db->hsize; |
| 488 | while (indx-- != 0) |
| 489 | { |
| 490 | db->dict[indx].codem1 = BADCODEM1; |
| 491 | db->dict[indx].cptr = 0; |
| 492 | } |
| 493 | |
| 494 | db->unit = unit; |
| 495 | db->mru = 0; |
| 496 | #ifndef DEBUG |
| 497 | if (debug) |
| 498 | #endif |
| 499 | db->debug = 1; |
| 500 | |
| 501 | bsd_reset(db); |
| 502 | |
| 503 | return 1; |
| 504 | } |
| 505 | |
| 506 | static int bsd_comp_init (void *state, unsigned char *options, |
| 507 | int opt_len, int unit, int opthdr, int debug) |
| 508 | { |
| 509 | return bsd_init (state, options, opt_len, unit, debug, 0); |
| 510 | } |
| 511 | |
| 512 | static int bsd_decomp_init (void *state, unsigned char *options, |
| 513 | int opt_len, int unit, int opthdr, int mru, |
| 514 | int debug) |
| 515 | { |
| 516 | return bsd_init (state, options, opt_len, unit, debug, 1); |
| 517 | } |
| 518 | |
| 519 | /* |
| 520 | * Obtain pointers to the various structures in the compression tables |
| 521 | */ |
| 522 | |
| 523 | #define dict_ptrx(p,idx) &(p->dict[idx]) |
| 524 | #define lens_ptrx(p,idx) &(p->lens[idx]) |
| 525 | |
| 526 | #ifdef DEBUG |
| 527 | static unsigned short *lens_ptr(struct bsd_db *db, int idx) |
| 528 | { |
| 529 | if ((unsigned int) idx > (unsigned int) db->maxmaxcode) |
| 530 | { |
| 531 | printk ("<9>ppp: lens_ptr(%d) > max\n", idx); |
| 532 | idx = 0; |
| 533 | } |
| 534 | return lens_ptrx (db, idx); |
| 535 | } |
| 536 | |
| 537 | static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx) |
| 538 | { |
| 539 | if ((unsigned int) idx >= (unsigned int) db->hsize) |
| 540 | { |
| 541 | printk ("<9>ppp: dict_ptr(%d) > max\n", idx); |
| 542 | idx = 0; |
| 543 | } |
| 544 | return dict_ptrx (db, idx); |
| 545 | } |
| 546 | |
| 547 | #else |
| 548 | #define lens_ptr(db,idx) lens_ptrx(db,idx) |
| 549 | #define dict_ptr(db,idx) dict_ptrx(db,idx) |
| 550 | #endif |
| 551 | |
| 552 | /* |
| 553 | * compress a packet |
| 554 | * |
| 555 | * The result of this function is the size of the compressed |
| 556 | * packet. A zero is returned if the packet was not compressed |
| 557 | * for some reason, such as the size being larger than uncompressed. |
| 558 | * |
| 559 | * One change from the BSD compress command is that when the |
| 560 | * code size expands, we do not output a bunch of padding. |
| 561 | */ |
| 562 | |
| 563 | static int bsd_compress (void *state, unsigned char *rptr, unsigned char *obuf, |
| 564 | int isize, int osize) |
| 565 | { |
| 566 | struct bsd_db *db; |
| 567 | int hshift; |
| 568 | unsigned int max_ent; |
| 569 | unsigned int n_bits; |
| 570 | unsigned int bitno; |
| 571 | unsigned long accm; |
| 572 | int ent; |
| 573 | unsigned long fcode; |
| 574 | struct bsd_dict *dictp; |
| 575 | unsigned char c; |
| 576 | int hval; |
| 577 | int disp; |
| 578 | int ilen; |
| 579 | int mxcode; |
| 580 | unsigned char *wptr; |
| 581 | int olen; |
| 582 | |
| 583 | #define PUTBYTE(v) \ |
| 584 | { \ |
| 585 | ++olen; \ |
| 586 | if (wptr) \ |
| 587 | { \ |
| 588 | *wptr++ = (unsigned char) (v); \ |
| 589 | if (olen >= osize) \ |
| 590 | { \ |
| 591 | wptr = NULL; \ |
| 592 | } \ |
| 593 | } \ |
| 594 | } |
| 595 | |
| 596 | #define OUTPUT(ent) \ |
| 597 | { \ |
| 598 | bitno -= n_bits; \ |
| 599 | accm |= ((ent) << bitno); \ |
| 600 | do \ |
| 601 | { \ |
| 602 | PUTBYTE(accm >> 24); \ |
| 603 | accm <<= 8; \ |
| 604 | bitno += 8; \ |
| 605 | } \ |
| 606 | while (bitno <= 24); \ |
| 607 | } |
| 608 | |
| 609 | /* |
| 610 | * If the protocol is not in the range we're interested in, |
| 611 | * just return without compressing the packet. If it is, |
| 612 | * the protocol becomes the first byte to compress. |
| 613 | */ |
| 614 | |
| 615 | ent = PPP_PROTOCOL(rptr); |
| 616 | if (ent < 0x21 || ent > 0xf9) |
| 617 | { |
| 618 | return 0; |
| 619 | } |
| 620 | |
| 621 | db = (struct bsd_db *) state; |
| 622 | hshift = db->hshift; |
| 623 | max_ent = db->max_ent; |
| 624 | n_bits = db->n_bits; |
| 625 | bitno = 32; |
| 626 | accm = 0; |
| 627 | mxcode = MAXCODE (n_bits); |
| 628 | |
| 629 | /* Initialize the output pointers */ |
| 630 | wptr = obuf; |
| 631 | olen = PPP_HDRLEN + BSD_OVHD; |
| 632 | |
| 633 | if (osize > isize) |
| 634 | { |
| 635 | osize = isize; |
| 636 | } |
| 637 | |
| 638 | /* This is the PPP header information */ |
| 639 | if (wptr) |
| 640 | { |
| 641 | *wptr++ = PPP_ADDRESS(rptr); |
| 642 | *wptr++ = PPP_CONTROL(rptr); |
| 643 | *wptr++ = 0; |
| 644 | *wptr++ = PPP_COMP; |
| 645 | *wptr++ = db->seqno >> 8; |
| 646 | *wptr++ = db->seqno; |
| 647 | } |
| 648 | |
| 649 | /* Skip the input header */ |
| 650 | rptr += PPP_HDRLEN; |
| 651 | isize -= PPP_HDRLEN; |
| 652 | ilen = ++isize; /* Low byte of protocol is counted as input */ |
| 653 | |
| 654 | while (--ilen > 0) |
| 655 | { |
| 656 | c = *rptr++; |
| 657 | fcode = BSD_KEY (ent, c); |
| 658 | hval = BSD_HASH (ent, c, hshift); |
| 659 | dictp = dict_ptr (db, hval); |
| 660 | |
| 661 | /* Validate and then check the entry. */ |
| 662 | if (dictp->codem1 >= max_ent) |
| 663 | { |
| 664 | goto nomatch; |
| 665 | } |
| 666 | |
| 667 | if (dictp->f.fcode == fcode) |
| 668 | { |
| 669 | ent = dictp->codem1 + 1; |
| 670 | continue; /* found (prefix,suffix) */ |
| 671 | } |
| 672 | |
| 673 | /* continue probing until a match or invalid entry */ |
| 674 | disp = (hval == 0) ? 1 : hval; |
| 675 | |
| 676 | do |
| 677 | { |
| 678 | hval += disp; |
| 679 | if (hval >= db->hsize) |
| 680 | { |
| 681 | hval -= db->hsize; |
| 682 | } |
| 683 | dictp = dict_ptr (db, hval); |
| 684 | if (dictp->codem1 >= max_ent) |
| 685 | { |
| 686 | goto nomatch; |
| 687 | } |
| 688 | } |
| 689 | while (dictp->f.fcode != fcode); |
| 690 | |
| 691 | ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ |
| 692 | continue; |
| 693 | |
| 694 | nomatch: |
| 695 | OUTPUT(ent); /* output the prefix */ |
| 696 | |
| 697 | /* code -> hashtable */ |
| 698 | if (max_ent < db->maxmaxcode) |
| 699 | { |
| 700 | struct bsd_dict *dictp2; |
| 701 | struct bsd_dict *dictp3; |
| 702 | int indx; |
| 703 | |
| 704 | /* expand code size if needed */ |
| 705 | if (max_ent >= mxcode) |
| 706 | { |
| 707 | db->n_bits = ++n_bits; |
| 708 | mxcode = MAXCODE (n_bits); |
| 709 | } |
| 710 | |
| 711 | /* Invalidate old hash table entry using |
| 712 | * this code, and then take it over. |
| 713 | */ |
| 714 | |
| 715 | dictp2 = dict_ptr (db, max_ent + 1); |
| 716 | indx = dictp2->cptr; |
| 717 | dictp3 = dict_ptr (db, indx); |
| 718 | |
| 719 | if (dictp3->codem1 == max_ent) |
| 720 | { |
| 721 | dictp3->codem1 = BADCODEM1; |
| 722 | } |
| 723 | |
| 724 | dictp2->cptr = hval; |
| 725 | dictp->codem1 = max_ent; |
| 726 | dictp->f.fcode = fcode; |
| 727 | db->max_ent = ++max_ent; |
| 728 | |
| 729 | if (db->lens) |
| 730 | { |
| 731 | unsigned short *len1 = lens_ptr (db, max_ent); |
| 732 | unsigned short *len2 = lens_ptr (db, ent); |
| 733 | *len1 = *len2 + 1; |
| 734 | } |
| 735 | } |
| 736 | ent = c; |
| 737 | } |
| 738 | |
| 739 | OUTPUT(ent); /* output the last code */ |
| 740 | |
| 741 | db->bytes_out += olen - PPP_HDRLEN - BSD_OVHD; |
| 742 | db->uncomp_bytes += isize; |
| 743 | db->in_count += isize; |
| 744 | ++db->uncomp_count; |
| 745 | ++db->seqno; |
| 746 | |
| 747 | if (bitno < 32) |
| 748 | { |
| 749 | ++db->bytes_out; /* must be set before calling bsd_check */ |
| 750 | } |
| 751 | |
| 752 | /* |
| 753 | * Generate the clear command if needed |
| 754 | */ |
| 755 | |
| 756 | if (bsd_check(db)) |
| 757 | { |
| 758 | OUTPUT (CLEAR); |
| 759 | } |
| 760 | |
| 761 | /* |
| 762 | * Pad dribble bits of last code with ones. |
| 763 | * Do not emit a completely useless byte of ones. |
| 764 | */ |
| 765 | |
| 766 | if (bitno != 32) |
| 767 | { |
| 768 | PUTBYTE((accm | (0xff << (bitno-8))) >> 24); |
| 769 | } |
| 770 | |
| 771 | /* |
| 772 | * Increase code size if we would have without the packet |
| 773 | * boundary because the decompressor will do so. |
| 774 | */ |
| 775 | |
| 776 | if (max_ent >= mxcode && max_ent < db->maxmaxcode) |
| 777 | { |
| 778 | db->n_bits++; |
| 779 | } |
| 780 | |
| 781 | /* If output length is too large then this is an incomplete frame. */ |
| 782 | if (wptr == NULL) |
| 783 | { |
| 784 | ++db->incomp_count; |
| 785 | db->incomp_bytes += isize; |
| 786 | olen = 0; |
| 787 | } |
| 788 | else /* Count the number of compressed frames */ |
| 789 | { |
| 790 | ++db->comp_count; |
| 791 | db->comp_bytes += olen; |
| 792 | } |
| 793 | |
| 794 | /* Return the resulting output length */ |
| 795 | return olen; |
| 796 | #undef OUTPUT |
| 797 | #undef PUTBYTE |
| 798 | } |
| 799 | |
| 800 | /* |
| 801 | * Update the "BSD Compress" dictionary on the receiver for |
| 802 | * incompressible data by pretending to compress the incoming data. |
| 803 | */ |
| 804 | |
| 805 | static void bsd_incomp (void *state, unsigned char *ibuf, int icnt) |
| 806 | { |
| 807 | (void) bsd_compress (state, ibuf, (char *) 0, icnt, 0); |
| 808 | } |
| 809 | |
| 810 | /* |
| 811 | * Decompress "BSD Compress". |
| 812 | * |
| 813 | * Because of patent problems, we return DECOMP_ERROR for errors |
| 814 | * found by inspecting the input data and for system problems, but |
| 815 | * DECOMP_FATALERROR for any errors which could possibly be said to |
| 816 | * be being detected "after" decompression. For DECOMP_ERROR, |
| 817 | * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be |
| 818 | * infringing a patent of Motorola's if we do, so we take CCP down |
| 819 | * instead. |
| 820 | * |
| 821 | * Given that the frame has the correct sequence number and a good FCS, |
| 822 | * errors such as invalid codes in the input most likely indicate a |
| 823 | * bug, so we return DECOMP_FATALERROR for them in order to turn off |
| 824 | * compression, even though they are detected by inspecting the input. |
| 825 | */ |
| 826 | |
| 827 | static int bsd_decompress (void *state, unsigned char *ibuf, int isize, |
| 828 | unsigned char *obuf, int osize) |
| 829 | { |
| 830 | struct bsd_db *db; |
| 831 | unsigned int max_ent; |
| 832 | unsigned long accm; |
| 833 | unsigned int bitno; /* 1st valid bit in accm */ |
| 834 | unsigned int n_bits; |
| 835 | unsigned int tgtbitno; /* bitno when we have a code */ |
| 836 | struct bsd_dict *dictp; |
| 837 | int explen; |
| 838 | int seq; |
| 839 | unsigned int incode; |
| 840 | unsigned int oldcode; |
| 841 | unsigned int finchar; |
| 842 | unsigned char *p; |
| 843 | unsigned char *wptr; |
| 844 | int adrs; |
| 845 | int ctrl; |
| 846 | int ilen; |
| 847 | int codelen; |
| 848 | int extra; |
| 849 | |
| 850 | db = (struct bsd_db *) state; |
| 851 | max_ent = db->max_ent; |
| 852 | accm = 0; |
| 853 | bitno = 32; /* 1st valid bit in accm */ |
| 854 | n_bits = db->n_bits; |
| 855 | tgtbitno = 32 - n_bits; /* bitno when we have a code */ |
| 856 | |
| 857 | /* |
| 858 | * Save the address/control from the PPP header |
| 859 | * and then get the sequence number. |
| 860 | */ |
| 861 | |
| 862 | adrs = PPP_ADDRESS (ibuf); |
| 863 | ctrl = PPP_CONTROL (ibuf); |
| 864 | |
| 865 | seq = (ibuf[4] << 8) + ibuf[5]; |
| 866 | |
| 867 | ibuf += (PPP_HDRLEN + 2); |
| 868 | ilen = isize - (PPP_HDRLEN + 2); |
| 869 | |
| 870 | /* |
| 871 | * Check the sequence number and give up if it differs from |
| 872 | * the value we're expecting. |
| 873 | */ |
| 874 | |
| 875 | if (seq != db->seqno) |
| 876 | { |
| 877 | if (db->debug) |
| 878 | { |
| 879 | printk("bsd_decomp%d: bad sequence # %d, expected %d\n", |
| 880 | db->unit, seq, db->seqno - 1); |
| 881 | } |
| 882 | return DECOMP_ERROR; |
| 883 | } |
| 884 | |
| 885 | ++db->seqno; |
| 886 | db->bytes_out += ilen; |
| 887 | |
| 888 | /* |
| 889 | * Fill in the ppp header, but not the last byte of the protocol |
| 890 | * (that comes from the decompressed data). |
| 891 | */ |
| 892 | |
| 893 | wptr = obuf; |
| 894 | *wptr++ = adrs; |
| 895 | *wptr++ = ctrl; |
| 896 | *wptr++ = 0; |
| 897 | |
| 898 | oldcode = CLEAR; |
| 899 | explen = 3; |
| 900 | |
| 901 | /* |
| 902 | * Keep the checkpoint correctly so that incompressible packets |
| 903 | * clear the dictionary at the proper times. |
| 904 | */ |
| 905 | |
| 906 | for (;;) |
| 907 | { |
| 908 | if (ilen-- <= 0) |
| 909 | { |
| 910 | db->in_count += (explen - 3); /* don't count the header */ |
| 911 | break; |
| 912 | } |
| 913 | |
| 914 | /* |
| 915 | * Accumulate bytes until we have a complete code. |
| 916 | * Then get the next code, relying on the 32-bit, |
| 917 | * unsigned accm to mask the result. |
| 918 | */ |
| 919 | |
| 920 | bitno -= 8; |
| 921 | accm |= *ibuf++ << bitno; |
| 922 | if (tgtbitno < bitno) |
| 923 | { |
| 924 | continue; |
| 925 | } |
| 926 | |
| 927 | incode = accm >> tgtbitno; |
| 928 | accm <<= n_bits; |
| 929 | bitno += n_bits; |
| 930 | |
| 931 | /* |
| 932 | * The dictionary must only be cleared at the end of a packet. |
| 933 | */ |
| 934 | |
| 935 | if (incode == CLEAR) |
| 936 | { |
| 937 | if (ilen > 0) |
| 938 | { |
| 939 | if (db->debug) |
| 940 | { |
| 941 | printk("bsd_decomp%d: bad CLEAR\n", db->unit); |
| 942 | } |
| 943 | return DECOMP_FATALERROR; /* probably a bug */ |
| 944 | } |
| 945 | |
| 946 | bsd_clear(db); |
| 947 | break; |
| 948 | } |
| 949 | |
| 950 | if ((incode > max_ent + 2) || (incode > db->maxmaxcode) |
| 951 | || (incode > max_ent && oldcode == CLEAR)) |
| 952 | { |
| 953 | if (db->debug) |
| 954 | { |
| 955 | printk("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", |
| 956 | db->unit, incode, oldcode); |
| 957 | printk("max_ent=0x%x explen=%d seqno=%d\n", |
| 958 | max_ent, explen, db->seqno); |
| 959 | } |
| 960 | return DECOMP_FATALERROR; /* probably a bug */ |
| 961 | } |
| 962 | |
| 963 | /* Special case for KwKwK string. */ |
| 964 | if (incode > max_ent) |
| 965 | { |
| 966 | finchar = oldcode; |
| 967 | extra = 1; |
| 968 | } |
| 969 | else |
| 970 | { |
| 971 | finchar = incode; |
| 972 | extra = 0; |
| 973 | } |
| 974 | |
| 975 | codelen = *(lens_ptr (db, finchar)); |
| 976 | explen += codelen + extra; |
| 977 | if (explen > osize) |
| 978 | { |
| 979 | if (db->debug) |
| 980 | { |
| 981 | printk("bsd_decomp%d: ran out of mru\n", db->unit); |
| 982 | #ifdef DEBUG |
| 983 | printk(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", |
| 984 | ilen, finchar, codelen, explen); |
| 985 | #endif |
| 986 | } |
| 987 | return DECOMP_FATALERROR; |
| 988 | } |
| 989 | |
| 990 | /* |
| 991 | * Decode this code and install it in the decompressed buffer. |
| 992 | */ |
| 993 | |
| 994 | wptr += codelen; |
| 995 | p = wptr; |
| 996 | while (finchar > LAST) |
| 997 | { |
| 998 | struct bsd_dict *dictp2 = dict_ptr (db, finchar); |
| 999 | |
| 1000 | dictp = dict_ptr (db, dictp2->cptr); |
| 1001 | #ifdef DEBUG |
| 1002 | if (--codelen <= 0 || dictp->codem1 != finchar-1) |
| 1003 | { |
| 1004 | if (codelen <= 0) |
| 1005 | { |
| 1006 | printk("bsd_decomp%d: fell off end of chain ", db->unit); |
| 1007 | printk("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", |
| 1008 | incode, finchar, dictp2->cptr, max_ent); |
| 1009 | } |
| 1010 | else |
| 1011 | { |
| 1012 | if (dictp->codem1 != finchar-1) |
| 1013 | { |
| 1014 | printk("bsd_decomp%d: bad code chain 0x%x " |
| 1015 | "finchar=0x%x ", |
| 1016 | db->unit, incode, finchar); |
| 1017 | |
| 1018 | printk("oldcode=0x%x cptr=0x%x codem1=0x%x\n", |
| 1019 | oldcode, dictp2->cptr, dictp->codem1); |
| 1020 | } |
| 1021 | } |
| 1022 | return DECOMP_FATALERROR; |
| 1023 | } |
| 1024 | #endif |
| 1025 | *--p = dictp->f.hs.suffix; |
| 1026 | finchar = dictp->f.hs.prefix; |
| 1027 | } |
| 1028 | *--p = finchar; |
| 1029 | |
| 1030 | #ifdef DEBUG |
| 1031 | if (--codelen != 0) |
| 1032 | { |
| 1033 | printk("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", |
| 1034 | db->unit, codelen, incode, max_ent); |
| 1035 | } |
| 1036 | #endif |
| 1037 | |
| 1038 | if (extra) /* the KwKwK case again */ |
| 1039 | { |
| 1040 | *wptr++ = finchar; |
| 1041 | } |
| 1042 | |
| 1043 | /* |
| 1044 | * If not first code in a packet, and |
| 1045 | * if not out of code space, then allocate a new code. |
| 1046 | * |
| 1047 | * Keep the hash table correct so it can be used |
| 1048 | * with uncompressed packets. |
| 1049 | */ |
| 1050 | |
| 1051 | if (oldcode != CLEAR && max_ent < db->maxmaxcode) |
| 1052 | { |
| 1053 | struct bsd_dict *dictp2, *dictp3; |
| 1054 | unsigned short *lens1, *lens2; |
| 1055 | unsigned long fcode; |
| 1056 | int hval, disp, indx; |
| 1057 | |
| 1058 | fcode = BSD_KEY(oldcode,finchar); |
| 1059 | hval = BSD_HASH(oldcode,finchar,db->hshift); |
| 1060 | dictp = dict_ptr (db, hval); |
| 1061 | |
| 1062 | /* look for a free hash table entry */ |
| 1063 | if (dictp->codem1 < max_ent) |
| 1064 | { |
| 1065 | disp = (hval == 0) ? 1 : hval; |
| 1066 | do |
| 1067 | { |
| 1068 | hval += disp; |
| 1069 | if (hval >= db->hsize) |
| 1070 | { |
| 1071 | hval -= db->hsize; |
| 1072 | } |
| 1073 | dictp = dict_ptr (db, hval); |
| 1074 | } |
| 1075 | while (dictp->codem1 < max_ent); |
| 1076 | } |
| 1077 | |
| 1078 | /* |
| 1079 | * Invalidate previous hash table entry |
| 1080 | * assigned this code, and then take it over |
| 1081 | */ |
| 1082 | |
| 1083 | dictp2 = dict_ptr (db, max_ent + 1); |
| 1084 | indx = dictp2->cptr; |
| 1085 | dictp3 = dict_ptr (db, indx); |
| 1086 | |
| 1087 | if (dictp3->codem1 == max_ent) |
| 1088 | { |
| 1089 | dictp3->codem1 = BADCODEM1; |
| 1090 | } |
| 1091 | |
| 1092 | dictp2->cptr = hval; |
| 1093 | dictp->codem1 = max_ent; |
| 1094 | dictp->f.fcode = fcode; |
| 1095 | db->max_ent = ++max_ent; |
| 1096 | |
| 1097 | /* Update the length of this string. */ |
| 1098 | lens1 = lens_ptr (db, max_ent); |
| 1099 | lens2 = lens_ptr (db, oldcode); |
| 1100 | *lens1 = *lens2 + 1; |
| 1101 | |
| 1102 | /* Expand code size if needed. */ |
| 1103 | if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) |
| 1104 | { |
| 1105 | db->n_bits = ++n_bits; |
| 1106 | tgtbitno = 32-n_bits; |
| 1107 | } |
| 1108 | } |
| 1109 | oldcode = incode; |
| 1110 | } |
| 1111 | |
| 1112 | ++db->comp_count; |
| 1113 | ++db->uncomp_count; |
| 1114 | db->comp_bytes += isize - BSD_OVHD - PPP_HDRLEN; |
| 1115 | db->uncomp_bytes += explen; |
| 1116 | |
| 1117 | if (bsd_check(db)) |
| 1118 | { |
| 1119 | if (db->debug) |
| 1120 | { |
| 1121 | printk("bsd_decomp%d: peer should have cleared dictionary on %d\n", |
| 1122 | db->unit, db->seqno - 1); |
| 1123 | } |
| 1124 | } |
| 1125 | return explen; |
| 1126 | } |
| 1127 | |
| 1128 | /************************************************************* |
| 1129 | * Table of addresses for the BSD compression module |
| 1130 | *************************************************************/ |
| 1131 | |
| 1132 | static struct compressor ppp_bsd_compress = { |
| 1133 | .compress_proto = CI_BSD_COMPRESS, |
| 1134 | .comp_alloc = bsd_comp_alloc, |
| 1135 | .comp_free = bsd_free, |
| 1136 | .comp_init = bsd_comp_init, |
| 1137 | .comp_reset = bsd_reset, |
| 1138 | .compress = bsd_compress, |
| 1139 | .comp_stat = bsd_comp_stats, |
| 1140 | .decomp_alloc = bsd_decomp_alloc, |
| 1141 | .decomp_free = bsd_free, |
| 1142 | .decomp_init = bsd_decomp_init, |
| 1143 | .decomp_reset = bsd_reset, |
| 1144 | .decompress = bsd_decompress, |
| 1145 | .incomp = bsd_incomp, |
| 1146 | .decomp_stat = bsd_comp_stats, |
| 1147 | .owner = THIS_MODULE |
| 1148 | }; |
| 1149 | |
| 1150 | /************************************************************* |
| 1151 | * Module support routines |
| 1152 | *************************************************************/ |
| 1153 | |
| 1154 | static int __init bsdcomp_init(void) |
| 1155 | { |
| 1156 | int answer = ppp_register_compressor(&ppp_bsd_compress); |
| 1157 | if (answer == 0) |
| 1158 | printk(KERN_INFO "PPP BSD Compression module registered\n"); |
| 1159 | return answer; |
| 1160 | } |
| 1161 | |
| 1162 | static void __exit bsdcomp_cleanup(void) |
| 1163 | { |
| 1164 | ppp_unregister_compressor(&ppp_bsd_compress); |
| 1165 | } |
| 1166 | |
| 1167 | module_init(bsdcomp_init); |
| 1168 | module_exit(bsdcomp_cleanup); |
| 1169 | MODULE_LICENSE("Dual BSD/GPL"); |
| 1170 | MODULE_ALIAS("ppp-compress-" __stringify(CI_BSD_COMPRESS)); |