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 115struct 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 136struct 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 168static void bsd_free (void *state); 169static void *bsd_alloc(unsigned char *options, int opt_len, int decomp); 170static void *bsd_comp_alloc (unsigned char *options, int opt_len); 171static void *bsd_decomp_alloc (unsigned char *options, int opt_len); 172 173static int bsd_init (void *db, unsigned char *options, 174 int opt_len, int unit, int debug, int decomp); 175static int bsd_comp_init (void *state, unsigned char *options, 176 int opt_len, int unit, int opthdr, int debug); 177static int bsd_decomp_init (void *state, unsigned char *options, 178 int opt_len, int unit, int opthdr, int mru, 179 int debug); 180 181static void bsd_reset (void *state); 182static void bsd_comp_stats (void *state, struct compstat *stats); 183 184static int bsd_compress (void *state, unsigned char *rptr, 185 unsigned char *obuf, int isize, int osize); 186static void bsd_incomp (void *state, unsigned char *ibuf, int icnt); 187 188static int bsd_decompress (void *state, unsigned char *ibuf, int isize, 189 unsigned char *obuf, int osize); 190 191/* These are in ppp_generic.c */ 192extern int ppp_register_compressor (struct compressor *cp); 193extern 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 221static void 222bsd_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 247static 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 293static 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 311static 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 325static 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 352static 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 = kmalloc(sizeof (struct bsd_db), 399 GFP_KERNEL); 400 if (!db) 401 { 402 return NULL; 403 } 404 405 memset (db, 0, sizeof(struct bsd_db)); 406/* 407 * Allocate space for the dictionary. This may be more than one page in 408 * length. 409 */ 410 db->dict = (struct bsd_dict *) vmalloc (hsize * 411 sizeof (struct bsd_dict)); 412 if (!db->dict) 413 { 414 bsd_free (db); 415 return NULL; 416 } 417 418/* 419 * If this is the compression buffer then there is no length data. 420 */ 421 if (!decomp) 422 { 423 db->lens = NULL; 424 } 425/* 426 * For decompression, the length information is needed as well. 427 */ 428 else 429 { 430 db->lens = (unsigned short *) vmalloc ((maxmaxcode + 1) * 431 sizeof (db->lens[0])); 432 if (!db->lens) 433 { 434 bsd_free (db); 435 return (NULL); 436 } 437 } 438/* 439 * Initialize the data information for the compression code 440 */ 441 db->totlen = sizeof (struct bsd_db) + 442 (sizeof (struct bsd_dict) * hsize); 443 444 db->hsize = hsize; 445 db->hshift = hshift; 446 db->maxmaxcode = maxmaxcode; 447 db->maxbits = bits; 448 449 return (void *) db; 450 } 451 452static void *bsd_comp_alloc (unsigned char *options, int opt_len) 453 { 454 return bsd_alloc (options, opt_len, 0); 455 } 456 457static void *bsd_decomp_alloc (unsigned char *options, int opt_len) 458 { 459 return bsd_alloc (options, opt_len, 1); 460 } 461 462/* 463 * Initialize the database. 464 */ 465 466static int bsd_init (void *state, unsigned char *options, 467 int opt_len, int unit, int debug, int decomp) 468 { 469 struct bsd_db *db = state; 470 int indx; 471 472 if ((opt_len != 3) || (options[0] != CI_BSD_COMPRESS) || (options[1] != 3) 473 || (BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 474 || (BSD_NBITS(options[2]) != db->maxbits) 475 || (decomp && db->lens == NULL)) 476 { 477 return 0; 478 } 479 480 if (decomp) 481 { 482 indx = LAST; 483 do 484 { 485 db->lens[indx] = 1; 486 } 487 while (indx-- > 0); 488 } 489 490 indx = db->hsize; 491 while (indx-- != 0) 492 { 493 db->dict[indx].codem1 = BADCODEM1; 494 db->dict[indx].cptr = 0; 495 } 496 497 db->unit = unit; 498 db->mru = 0; 499#ifndef DEBUG 500 if (debug) 501#endif 502 db->debug = 1; 503 504 bsd_reset(db); 505 506 return 1; 507 } 508 509static int bsd_comp_init (void *state, unsigned char *options, 510 int opt_len, int unit, int opthdr, int debug) 511 { 512 return bsd_init (state, options, opt_len, unit, debug, 0); 513 } 514 515static int bsd_decomp_init (void *state, unsigned char *options, 516 int opt_len, int unit, int opthdr, int mru, 517 int debug) 518 { 519 return bsd_init (state, options, opt_len, unit, debug, 1); 520 } 521 522/* 523 * Obtain pointers to the various structures in the compression tables 524 */ 525 526#define dict_ptrx(p,idx) &(p->dict[idx]) 527#define lens_ptrx(p,idx) &(p->lens[idx]) 528 529#ifdef DEBUG 530static unsigned short *lens_ptr(struct bsd_db *db, int idx) 531 { 532 if ((unsigned int) idx > (unsigned int) db->maxmaxcode) 533 { 534 printk ("<9>ppp: lens_ptr(%d) > max\n", idx); 535 idx = 0; 536 } 537 return lens_ptrx (db, idx); 538 } 539 540static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx) 541 { 542 if ((unsigned int) idx >= (unsigned int) db->hsize) 543 { 544 printk ("<9>ppp: dict_ptr(%d) > max\n", idx); 545 idx = 0; 546 } 547 return dict_ptrx (db, idx); 548 } 549 550#else 551#define lens_ptr(db,idx) lens_ptrx(db,idx) 552#define dict_ptr(db,idx) dict_ptrx(db,idx) 553#endif 554 555/* 556 * compress a packet 557 * 558 * The result of this function is the size of the compressed 559 * packet. A zero is returned if the packet was not compressed 560 * for some reason, such as the size being larger than uncompressed. 561 * 562 * One change from the BSD compress command is that when the 563 * code size expands, we do not output a bunch of padding. 564 */ 565 566static int bsd_compress (void *state, unsigned char *rptr, unsigned char *obuf, 567 int isize, int osize) 568 { 569 struct bsd_db *db; 570 int hshift; 571 unsigned int max_ent; 572 unsigned int n_bits; 573 unsigned int bitno; 574 unsigned long accm; 575 int ent; 576 unsigned long fcode; 577 struct bsd_dict *dictp; 578 unsigned char c; 579 int hval; 580 int disp; 581 int ilen; 582 int mxcode; 583 unsigned char *wptr; 584 int olen; 585 586#define PUTBYTE(v) \ 587 { \ 588 ++olen; \ 589 if (wptr) \ 590 { \ 591 *wptr++ = (unsigned char) (v); \ 592 if (olen >= osize) \ 593 { \ 594 wptr = NULL; \ 595 } \ 596 } \ 597 } 598 599#define OUTPUT(ent) \ 600 { \ 601 bitno -= n_bits; \ 602 accm |= ((ent) << bitno); \ 603 do \ 604 { \ 605 PUTBYTE(accm >> 24); \ 606 accm <<= 8; \ 607 bitno += 8; \ 608 } \ 609 while (bitno <= 24); \ 610 } 611 612 /* 613 * If the protocol is not in the range we're interested in, 614 * just return without compressing the packet. If it is, 615 * the protocol becomes the first byte to compress. 616 */ 617 618 ent = PPP_PROTOCOL(rptr); 619 if (ent < 0x21 || ent > 0xf9) 620 { 621 return 0; 622 } 623 624 db = (struct bsd_db *) state; 625 hshift = db->hshift; 626 max_ent = db->max_ent; 627 n_bits = db->n_bits; 628 bitno = 32; 629 accm = 0; 630 mxcode = MAXCODE (n_bits); 631 632 /* Initialize the output pointers */ 633 wptr = obuf; 634 olen = PPP_HDRLEN + BSD_OVHD; 635 636 if (osize > isize) 637 { 638 osize = isize; 639 } 640 641 /* This is the PPP header information */ 642 if (wptr) 643 { 644 *wptr++ = PPP_ADDRESS(rptr); 645 *wptr++ = PPP_CONTROL(rptr); 646 *wptr++ = 0; 647 *wptr++ = PPP_COMP; 648 *wptr++ = db->seqno >> 8; 649 *wptr++ = db->seqno; 650 } 651 652 /* Skip the input header */ 653 rptr += PPP_HDRLEN; 654 isize -= PPP_HDRLEN; 655 ilen = ++isize; /* Low byte of protocol is counted as input */ 656 657 while (--ilen > 0) 658 { 659 c = *rptr++; 660 fcode = BSD_KEY (ent, c); 661 hval = BSD_HASH (ent, c, hshift); 662 dictp = dict_ptr (db, hval); 663 664 /* Validate and then check the entry. */ 665 if (dictp->codem1 >= max_ent) 666 { 667 goto nomatch; 668 } 669 670 if (dictp->f.fcode == fcode) 671 { 672 ent = dictp->codem1 + 1; 673 continue; /* found (prefix,suffix) */ 674 } 675 676 /* continue probing until a match or invalid entry */ 677 disp = (hval == 0) ? 1 : hval; 678 679 do 680 { 681 hval += disp; 682 if (hval >= db->hsize) 683 { 684 hval -= db->hsize; 685 } 686 dictp = dict_ptr (db, hval); 687 if (dictp->codem1 >= max_ent) 688 { 689 goto nomatch; 690 } 691 } 692 while (dictp->f.fcode != fcode); 693 694 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 695 continue; 696 697nomatch: 698 OUTPUT(ent); /* output the prefix */ 699 700 /* code -> hashtable */ 701 if (max_ent < db->maxmaxcode) 702 { 703 struct bsd_dict *dictp2; 704 struct bsd_dict *dictp3; 705 int indx; 706 707 /* expand code size if needed */ 708 if (max_ent >= mxcode) 709 { 710 db->n_bits = ++n_bits; 711 mxcode = MAXCODE (n_bits); 712 } 713 714 /* Invalidate old hash table entry using 715 * this code, and then take it over. 716 */ 717 718 dictp2 = dict_ptr (db, max_ent + 1); 719 indx = dictp2->cptr; 720 dictp3 = dict_ptr (db, indx); 721 722 if (dictp3->codem1 == max_ent) 723 { 724 dictp3->codem1 = BADCODEM1; 725 } 726 727 dictp2->cptr = hval; 728 dictp->codem1 = max_ent; 729 dictp->f.fcode = fcode; 730 db->max_ent = ++max_ent; 731 732 if (db->lens) 733 { 734 unsigned short *len1 = lens_ptr (db, max_ent); 735 unsigned short *len2 = lens_ptr (db, ent); 736 *len1 = *len2 + 1; 737 } 738 } 739 ent = c; 740 } 741 742 OUTPUT(ent); /* output the last code */ 743 744 db->bytes_out += olen - PPP_HDRLEN - BSD_OVHD; 745 db->uncomp_bytes += isize; 746 db->in_count += isize; 747 ++db->uncomp_count; 748 ++db->seqno; 749 750 if (bitno < 32) 751 { 752 ++db->bytes_out; /* must be set before calling bsd_check */ 753 } 754 755 /* 756 * Generate the clear command if needed 757 */ 758 759 if (bsd_check(db)) 760 { 761 OUTPUT (CLEAR); 762 } 763 764 /* 765 * Pad dribble bits of last code with ones. 766 * Do not emit a completely useless byte of ones. 767 */ 768 769 if (bitno != 32) 770 { 771 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 772 } 773 774 /* 775 * Increase code size if we would have without the packet 776 * boundary because the decompressor will do so. 777 */ 778 779 if (max_ent >= mxcode && max_ent < db->maxmaxcode) 780 { 781 db->n_bits++; 782 } 783 784 /* If output length is too large then this is an incomplete frame. */ 785 if (wptr == NULL) 786 { 787 ++db->incomp_count; 788 db->incomp_bytes += isize; 789 olen = 0; 790 } 791 else /* Count the number of compressed frames */ 792 { 793 ++db->comp_count; 794 db->comp_bytes += olen; 795 } 796 797 /* Return the resulting output length */ 798 return olen; 799#undef OUTPUT 800#undef PUTBYTE 801 } 802 803/* 804 * Update the "BSD Compress" dictionary on the receiver for 805 * incompressible data by pretending to compress the incoming data. 806 */ 807 808static void bsd_incomp (void *state, unsigned char *ibuf, int icnt) 809 { 810 (void) bsd_compress (state, ibuf, (char *) 0, icnt, 0); 811 } 812 813/* 814 * Decompress "BSD Compress". 815 * 816 * Because of patent problems, we return DECOMP_ERROR for errors 817 * found by inspecting the input data and for system problems, but 818 * DECOMP_FATALERROR for any errors which could possibly be said to 819 * be being detected "after" decompression. For DECOMP_ERROR, 820 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 821 * infringing a patent of Motorola's if we do, so we take CCP down 822 * instead. 823 * 824 * Given that the frame has the correct sequence number and a good FCS, 825 * errors such as invalid codes in the input most likely indicate a 826 * bug, so we return DECOMP_FATALERROR for them in order to turn off 827 * compression, even though they are detected by inspecting the input. 828 */ 829 830static int bsd_decompress (void *state, unsigned char *ibuf, int isize, 831 unsigned char *obuf, int osize) 832 { 833 struct bsd_db *db; 834 unsigned int max_ent; 835 unsigned long accm; 836 unsigned int bitno; /* 1st valid bit in accm */ 837 unsigned int n_bits; 838 unsigned int tgtbitno; /* bitno when we have a code */ 839 struct bsd_dict *dictp; 840 int explen; 841 int seq; 842 unsigned int incode; 843 unsigned int oldcode; 844 unsigned int finchar; 845 unsigned char *p; 846 unsigned char *wptr; 847 int adrs; 848 int ctrl; 849 int ilen; 850 int codelen; 851 int extra; 852 853 db = (struct bsd_db *) state; 854 max_ent = db->max_ent; 855 accm = 0; 856 bitno = 32; /* 1st valid bit in accm */ 857 n_bits = db->n_bits; 858 tgtbitno = 32 - n_bits; /* bitno when we have a code */ 859 860 /* 861 * Save the address/control from the PPP header 862 * and then get the sequence number. 863 */ 864 865 adrs = PPP_ADDRESS (ibuf); 866 ctrl = PPP_CONTROL (ibuf); 867 868 seq = (ibuf[4] << 8) + ibuf[5]; 869 870 ibuf += (PPP_HDRLEN + 2); 871 ilen = isize - (PPP_HDRLEN + 2); 872 873 /* 874 * Check the sequence number and give up if it differs from 875 * the value we're expecting. 876 */ 877 878 if (seq != db->seqno) 879 { 880 if (db->debug) 881 { 882 printk("bsd_decomp%d: bad sequence # %d, expected %d\n", 883 db->unit, seq, db->seqno - 1); 884 } 885 return DECOMP_ERROR; 886 } 887 888 ++db->seqno; 889 db->bytes_out += ilen; 890 891 /* 892 * Fill in the ppp header, but not the last byte of the protocol 893 * (that comes from the decompressed data). 894 */ 895 896 wptr = obuf; 897 *wptr++ = adrs; 898 *wptr++ = ctrl; 899 *wptr++ = 0; 900 901 oldcode = CLEAR; 902 explen = 3; 903 904 /* 905 * Keep the checkpoint correctly so that incompressible packets 906 * clear the dictionary at the proper times. 907 */ 908 909 for (;;) 910 { 911 if (ilen-- <= 0) 912 { 913 db->in_count += (explen - 3); /* don't count the header */ 914 break; 915 } 916 917 /* 918 * Accumulate bytes until we have a complete code. 919 * Then get the next code, relying on the 32-bit, 920 * unsigned accm to mask the result. 921 */ 922 923 bitno -= 8; 924 accm |= *ibuf++ << bitno; 925 if (tgtbitno < bitno) 926 { 927 continue; 928 } 929 930 incode = accm >> tgtbitno; 931 accm <<= n_bits; 932 bitno += n_bits; 933 934 /* 935 * The dictionary must only be cleared at the end of a packet. 936 */ 937 938 if (incode == CLEAR) 939 { 940 if (ilen > 0) 941 { 942 if (db->debug) 943 { 944 printk("bsd_decomp%d: bad CLEAR\n", db->unit); 945 } 946 return DECOMP_FATALERROR; /* probably a bug */ 947 } 948 949 bsd_clear(db); 950 break; 951 } 952 953 if ((incode > max_ent + 2) || (incode > db->maxmaxcode) 954 || (incode > max_ent && oldcode == CLEAR)) 955 { 956 if (db->debug) 957 { 958 printk("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 959 db->unit, incode, oldcode); 960 printk("max_ent=0x%x explen=%d seqno=%d\n", 961 max_ent, explen, db->seqno); 962 } 963 return DECOMP_FATALERROR; /* probably a bug */ 964 } 965 966 /* Special case for KwKwK string. */ 967 if (incode > max_ent) 968 { 969 finchar = oldcode; 970 extra = 1; 971 } 972 else 973 { 974 finchar = incode; 975 extra = 0; 976 } 977 978 codelen = *(lens_ptr (db, finchar)); 979 explen += codelen + extra; 980 if (explen > osize) 981 { 982 if (db->debug) 983 { 984 printk("bsd_decomp%d: ran out of mru\n", db->unit); 985#ifdef DEBUG 986 printk(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 987 ilen, finchar, codelen, explen); 988#endif 989 } 990 return DECOMP_FATALERROR; 991 } 992 993 /* 994 * Decode this code and install it in the decompressed buffer. 995 */ 996 997 wptr += codelen; 998 p = wptr; 999 while (finchar > LAST) 1000 { 1001 struct bsd_dict *dictp2 = dict_ptr (db, finchar); 1002 1003 dictp = dict_ptr (db, dictp2->cptr); 1004#ifdef DEBUG 1005 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1006 { 1007 if (codelen <= 0) 1008 { 1009 printk("bsd_decomp%d: fell off end of chain ", db->unit); 1010 printk("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1011 incode, finchar, dictp2->cptr, max_ent); 1012 } 1013 else 1014 { 1015 if (dictp->codem1 != finchar-1) 1016 { 1017 printk("bsd_decomp%d: bad code chain 0x%x " 1018 "finchar=0x%x ", 1019 db->unit, incode, finchar); 1020 1021 printk("oldcode=0x%x cptr=0x%x codem1=0x%x\n", 1022 oldcode, dictp2->cptr, dictp->codem1); 1023 } 1024 } 1025 return DECOMP_FATALERROR; 1026 } 1027#endif 1028 *--p = dictp->f.hs.suffix; 1029 finchar = dictp->f.hs.prefix; 1030 } 1031 *--p = finchar; 1032 1033#ifdef DEBUG 1034 if (--codelen != 0) 1035 { 1036 printk("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1037 db->unit, codelen, incode, max_ent); 1038 } 1039#endif 1040 1041 if (extra) /* the KwKwK case again */ 1042 { 1043 *wptr++ = finchar; 1044 } 1045 1046 /* 1047 * If not first code in a packet, and 1048 * if not out of code space, then allocate a new code. 1049 * 1050 * Keep the hash table correct so it can be used 1051 * with uncompressed packets. 1052 */ 1053 1054 if (oldcode != CLEAR && max_ent < db->maxmaxcode) 1055 { 1056 struct bsd_dict *dictp2, *dictp3; 1057 unsigned short *lens1, *lens2; 1058 unsigned long fcode; 1059 int hval, disp, indx; 1060 1061 fcode = BSD_KEY(oldcode,finchar); 1062 hval = BSD_HASH(oldcode,finchar,db->hshift); 1063 dictp = dict_ptr (db, hval); 1064 1065 /* look for a free hash table entry */ 1066 if (dictp->codem1 < max_ent) 1067 { 1068 disp = (hval == 0) ? 1 : hval; 1069 do 1070 { 1071 hval += disp; 1072 if (hval >= db->hsize) 1073 { 1074 hval -= db->hsize; 1075 } 1076 dictp = dict_ptr (db, hval); 1077 } 1078 while (dictp->codem1 < max_ent); 1079 } 1080 1081 /* 1082 * Invalidate previous hash table entry 1083 * assigned this code, and then take it over 1084 */ 1085 1086 dictp2 = dict_ptr (db, max_ent + 1); 1087 indx = dictp2->cptr; 1088 dictp3 = dict_ptr (db, indx); 1089 1090 if (dictp3->codem1 == max_ent) 1091 { 1092 dictp3->codem1 = BADCODEM1; 1093 } 1094 1095 dictp2->cptr = hval; 1096 dictp->codem1 = max_ent; 1097 dictp->f.fcode = fcode; 1098 db->max_ent = ++max_ent; 1099 1100 /* Update the length of this string. */ 1101 lens1 = lens_ptr (db, max_ent); 1102 lens2 = lens_ptr (db, oldcode); 1103 *lens1 = *lens2 + 1; 1104 1105 /* Expand code size if needed. */ 1106 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 1107 { 1108 db->n_bits = ++n_bits; 1109 tgtbitno = 32-n_bits; 1110 } 1111 } 1112 oldcode = incode; 1113 } 1114 1115 ++db->comp_count; 1116 ++db->uncomp_count; 1117 db->comp_bytes += isize - BSD_OVHD - PPP_HDRLEN; 1118 db->uncomp_bytes += explen; 1119 1120 if (bsd_check(db)) 1121 { 1122 if (db->debug) 1123 { 1124 printk("bsd_decomp%d: peer should have cleared dictionary on %d\n", 1125 db->unit, db->seqno - 1); 1126 } 1127 } 1128 return explen; 1129 } 1130 1131/************************************************************* 1132 * Table of addresses for the BSD compression module 1133 *************************************************************/ 1134 1135static struct compressor ppp_bsd_compress = { 1136 .compress_proto = CI_BSD_COMPRESS, 1137 .comp_alloc = bsd_comp_alloc, 1138 .comp_free = bsd_free, 1139 .comp_init = bsd_comp_init, 1140 .comp_reset = bsd_reset, 1141 .compress = bsd_compress, 1142 .comp_stat = bsd_comp_stats, 1143 .decomp_alloc = bsd_decomp_alloc, 1144 .decomp_free = bsd_free, 1145 .decomp_init = bsd_decomp_init, 1146 .decomp_reset = bsd_reset, 1147 .decompress = bsd_decompress, 1148 .incomp = bsd_incomp, 1149 .decomp_stat = bsd_comp_stats, 1150 .owner = THIS_MODULE 1151}; 1152 1153/************************************************************* 1154 * Module support routines 1155 *************************************************************/ 1156 1157static int __init bsdcomp_init(void) 1158{ 1159 int answer = ppp_register_compressor(&ppp_bsd_compress); 1160 if (answer == 0) 1161 printk(KERN_INFO "PPP BSD Compression module registered\n"); 1162 return answer; 1163} 1164 1165static void __exit bsdcomp_cleanup(void) 1166{ 1167 ppp_unregister_compressor(&ppp_bsd_compress); 1168} 1169 1170module_init(bsdcomp_init); 1171module_exit(bsdcomp_cleanup); 1172MODULE_LICENSE("Dual BSD/GPL"); 1173MODULE_ALIAS("ppp-compress-" __stringify(CI_BSD_COMPRESS)); 1174