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(array_size(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(array_size(sizeof(db->lens[0]), (maxmaxcode + 1))); 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_DESCRIPTION("PPP BSD-Compress compression module"); 1170 MODULE_LICENSE("Dual BSD/GPL"); 1171 MODULE_ALIAS("ppp-compress-" __stringify(CI_BSD_COMPRESS)); 1172