1/* $NetBSD: bsd-comp.c,v 1.19 2008/11/25 02:40:36 cube Exp $ */ 2/* Id: bsd-comp.c,v 1.6 1996/08/28 06:31:58 paulus Exp */ 3 4/* Because this code is derived from the 4.3BSD compress source: 5 * 6 * 7 * Copyright (c) 1985, 1986 The Regents of the University of California. 8 * All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * James A. Woods, derived from original work by Spencer Thomas 12 * and Joseph Orost. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39/* 40 * This version is for use with mbufs on BSD-derived systems. 41 */ 42 43#include <sys/cdefs.h> 44__KERNEL_RCSID(0, "$NetBSD: bsd-comp.c,v 1.19 2008/11/25 02:40:36 cube Exp $"); 45 46#include <sys/param.h> 47#include <sys/systm.h> 48#include <sys/mbuf.h> 49#include <sys/socket.h> 50#include <sys/module.h> 51#include <net/if.h> 52#include <net/if_types.h> 53#include <net/ppp_defs.h> 54#include <net/if_ppp.h> 55 56#define PACKETPTR struct mbuf * 57#include <net/ppp-comp.h> 58 59#if DO_BSD_COMPRESS 60/* 61 * PPP "BSD compress" compression 62 * The differences between this compression and the classic BSD LZW 63 * source are obvious from the requirement that the classic code worked 64 * with files while this handles arbitrarily long streams that 65 * are broken into packets. They are: 66 * 67 * When the code size expands, a block of junk is not emitted by 68 * the compressor and not expected by the decompressor. 69 * 70 * New codes are not necessarily assigned every time an old 71 * code is output by the compressor. This is because a packet 72 * end forces a code to be emitted, but does not imply that a 73 * new sequence has been seen. 74 * 75 * The compression ratio is checked at the first end of a packet 76 * after the appropriate gap. Besides simplifying and speeding 77 * things up, this makes it more likely that the transmitter 78 * and receiver will agree when the dictionary is cleared when 79 * compression is not going well. 80 */ 81 82/* 83 * A dictionary for doing BSD compress. 84 */ 85struct bsd_db { 86 int totlen; /* length of this structure */ 87 u_int hsize; /* size of the hash table */ 88 u_char hshift; /* used in hash function */ 89 u_char n_bits; /* current bits/code */ 90 u_char maxbits; 91 u_char debug; 92 u_char unit; 93 uint16_t seqno; /* sequence # of next packet */ 94 u_int hdrlen; /* header length to preallocate */ 95 u_int mru; 96 u_int maxmaxcode; /* largest valid code */ 97 u_int max_ent; /* largest code in use */ 98 u_int in_count; /* uncompressed bytes, aged */ 99 u_int bytes_out; /* compressed bytes, aged */ 100 u_int ratio; /* recent compression ratio */ 101 u_int checkpoint; /* when to next check the ratio */ 102 u_int clear_count; /* times dictionary cleared */ 103 u_int incomp_count; /* incompressible packets */ 104 u_int incomp_bytes; /* incompressible bytes */ 105 u_int uncomp_count; /* uncompressed packets */ 106 u_int uncomp_bytes; /* uncompressed bytes */ 107 u_int comp_count; /* compressed packets */ 108 u_int comp_bytes; /* compressed bytes */ 109 uint16_t *lens; /* array of lengths of codes */ 110 struct bsd_dict { 111 union { /* hash value */ 112 uint32_t fcode; 113 struct { 114#if BYTE_ORDER == LITTLE_ENDIAN 115 uint16_t prefix; /* preceding code */ 116 u_char suffix; /* last character of new code */ 117 u_char pad; 118#else 119 u_char pad; 120 u_char suffix; /* last character of new code */ 121 uint16_t prefix; /* preceding code */ 122#endif 123 } hs; 124 } f; 125 uint16_t codem1; /* output of hash table -1 */ 126 uint16_t cptr; /* map code to hash table entry */ 127 } dict[1]; 128}; 129 130#define BSD_OVHD 2 /* BSD compress overhead/packet */ 131#define BSD_INIT_BITS BSD_MIN_BITS 132 133static void *bsd_comp_alloc(u_char *options, int opt_len); 134static void *bsd_decomp_alloc(u_char *options, int opt_len); 135static void bsd_free(void *state); 136static int bsd_comp_init(void *state, u_char *options, int opt_len, 137 int unit, int hdrlen, int debug); 138static int bsd_decomp_init(void *state, u_char *options, int opt_len, 139 int unit, int hdrlen, int mru, int debug); 140static int bsd_compress(void *state, struct mbuf **mret, 141 struct mbuf *mp, int slen, int maxolen); 142static void bsd_incomp(void *state, struct mbuf *dmsg); 143static int bsd_decompress(void *state, struct mbuf *cmp, 144 struct mbuf **dmpp); 145static void bsd_reset(void *state); 146static void bsd_comp_stats(void *state, struct compstat *stats); 147 148/* 149 * Procedures exported to if_ppp.c. 150 */ 151static struct compressor ppp_bsd_compress = { 152 .compress_proto = CI_BSD_COMPRESS, 153 .comp_alloc = bsd_comp_alloc, 154 .comp_free = bsd_free, 155 .comp_init = bsd_comp_init, 156 .comp_reset = bsd_reset, 157 .compress = bsd_compress, 158 .comp_stat = bsd_comp_stats, 159 .decomp_alloc = bsd_decomp_alloc, 160 .decomp_free = bsd_free, 161 .decomp_init = bsd_decomp_init, 162 .decomp_reset = bsd_reset, 163 .decompress = bsd_decompress, 164 .incomp = bsd_incomp, 165 .decomp_stat = bsd_comp_stats, 166}; 167 168/* 169 * the next two codes should not be changed lightly, as they must not 170 * lie within the contiguous general code space. 171 */ 172#define CLEAR 256 /* table clear output code */ 173#define FIRST 257 /* first free entry */ 174#define LAST 255 175 176#define MAXCODE(b) ((1 << (b)) - 1) 177#define BADCODEM1 MAXCODE(BSD_MAX_BITS) 178 179#define BSD_HASH(prefix,suffix,hshift) ((((uint32_t)(suffix)) << (hshift)) \ 180 ^ (uint32_t)(prefix)) 181#define BSD_KEY(prefix,suffix) ((((uint32_t)(suffix)) << 16) \ 182 + (uint32_t)(prefix)) 183 184#define CHECK_GAP 10000 /* Ratio check interval */ 185 186#define RATIO_SCALE_LOG 8 187#define RATIO_SCALE (1<<RATIO_SCALE_LOG) 188#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 189 190static void bsd_clear(struct bsd_db *); 191static int bsd_check(struct bsd_db *); 192static void *bsd_alloc(u_char *, int, int); 193static int bsd_init(struct bsd_db *, u_char *, int, int, int, int, 194 int, int); 195 196/* 197 * clear the dictionary 198 */ 199static void 200bsd_clear(struct bsd_db *db) 201{ 202 db->clear_count++; 203 db->max_ent = FIRST-1; 204 db->n_bits = BSD_INIT_BITS; 205 db->ratio = 0; 206 db->bytes_out = 0; 207 db->in_count = 0; 208 db->checkpoint = CHECK_GAP; 209} 210 211/* 212 * If the dictionary is full, then see if it is time to reset it. 213 * 214 * Compute the compression ratio using fixed-point arithmetic 215 * with 8 fractional bits. 216 * 217 * Since we have an infinite stream instead of a single file, 218 * watch only the local compression ratio. 219 * 220 * Since both peers must reset the dictionary at the same time even in 221 * the absence of CLEAR codes (while packets are incompressible), they 222 * must compute the same ratio. 223 */ 224static int /* 1=output CLEAR */ 225bsd_check(struct bsd_db *db) 226{ 227 u_int new_ratio; 228 229 if (db->in_count >= db->checkpoint) { 230 /* age the ratio by limiting the size of the counts */ 231 if (db->in_count >= RATIO_MAX 232 || db->bytes_out >= RATIO_MAX) { 233 db->in_count -= db->in_count/4; 234 db->bytes_out -= db->bytes_out/4; 235 } 236 237 db->checkpoint = db->in_count + CHECK_GAP; 238 239 if (db->max_ent >= db->maxmaxcode) { 240 /* Reset the dictionary only if the ratio is worse, 241 * or if it looks as if it has been poisoned 242 * by incompressible data. 243 * 244 * This does not overflow, because 245 * db->in_count <= RATIO_MAX. 246 */ 247 new_ratio = db->in_count << RATIO_SCALE_LOG; 248 if (db->bytes_out != 0) 249 new_ratio /= db->bytes_out; 250 251 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 252 bsd_clear(db); 253 return 1; 254 } 255 db->ratio = new_ratio; 256 } 257 } 258 return 0; 259} 260 261/* 262 * Return statistics. 263 */ 264static void 265bsd_comp_stats(void *state, struct compstat *stats) 266{ 267 struct bsd_db *db = (struct bsd_db *) state; 268 u_int out; 269 270 stats->unc_bytes = db->uncomp_bytes; 271 stats->unc_packets = db->uncomp_count; 272 stats->comp_bytes = db->comp_bytes; 273 stats->comp_packets = db->comp_count; 274 stats->inc_bytes = db->incomp_bytes; 275 stats->inc_packets = db->incomp_count; 276 stats->ratio = db->in_count; 277 out = db->bytes_out; 278 if (stats->ratio <= 0x7fffff) 279 stats->ratio <<= 8; 280 else 281 out >>= 8; 282 if (out != 0) 283 stats->ratio /= out; 284} 285 286/* 287 * Reset state, as on a CCP ResetReq. 288 */ 289static void 290bsd_reset(void *state) 291{ 292 struct bsd_db *db = (struct bsd_db *) state; 293 294 db->seqno = 0; 295 bsd_clear(db); 296 db->clear_count = 0; 297} 298 299/* 300 * Allocate space for a (de) compressor. 301 */ 302static void * 303bsd_alloc(u_char *options, int opt_len, int decomp) 304{ 305 int bits; 306 u_int newlen, hsize, hshift, maxmaxcode; 307 struct bsd_db *db; 308 309 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 310 || options[1] != CILEN_BSD_COMPRESS 311 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 312 return NULL; 313 bits = BSD_NBITS(options[2]); 314 switch (bits) { 315 case 9: /* needs 82152 for both directions */ 316 case 10: /* needs 84144 */ 317 case 11: /* needs 88240 */ 318 case 12: /* needs 96432 */ 319 hsize = 5003; 320 hshift = 4; 321 break; 322 case 13: /* needs 176784 */ 323 hsize = 9001; 324 hshift = 5; 325 break; 326 case 14: /* needs 353744 */ 327 hsize = 18013; 328 hshift = 6; 329 break; 330 case 15: /* needs 691440 */ 331 hsize = 35023; 332 hshift = 7; 333 break; 334 case 16: /* needs 1366160--far too much, */ 335 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 336 /* hshift = 8; */ /* in struct bsd_db */ 337 /* break; */ 338 default: 339 return NULL; 340 } 341 342 maxmaxcode = MAXCODE(bits); 343 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 344 db = malloc(newlen, M_DEVBUF, M_NOWAIT|M_ZERO); 345 if (!db) 346 return NULL; 347 348 if (!decomp) { 349 db->lens = NULL; 350 } else { 351 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]), 352 M_DEVBUF, M_NOWAIT); 353 if (!db->lens) { 354 free(db, M_DEVBUF); 355 return NULL; 356 } 357 } 358 359 db->totlen = newlen; 360 db->hsize = hsize; 361 db->hshift = hshift; 362 db->maxmaxcode = maxmaxcode; 363 db->maxbits = bits; 364 365 return (void *) db; 366} 367 368static void 369bsd_free(void *state) 370{ 371 struct bsd_db *db = (struct bsd_db *) state; 372 373 if (db->lens) 374 free(db->lens, M_DEVBUF); 375 free(db, M_DEVBUF); 376} 377 378static void * 379bsd_comp_alloc(u_char *options, int opt_len) 380{ 381 return bsd_alloc(options, opt_len, 0); 382} 383 384static void * 385bsd_decomp_alloc(u_char *options, int opt_len) 386{ 387 return bsd_alloc(options, opt_len, 1); 388} 389 390/* 391 * Initialize the database. 392 */ 393static int 394bsd_init(struct bsd_db *db, u_char *options, int opt_len, int unit, int hdrlen, 395 int mru, int debug, int decomp) 396{ 397 int i; 398 399 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 400 || options[1] != CILEN_BSD_COMPRESS 401 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 402 || BSD_NBITS(options[2]) != db->maxbits 403 || (decomp && db->lens == NULL)) 404 return 0; 405 406 if (decomp) { 407 i = LAST+1; 408 while (i != 0) 409 db->lens[--i] = 1; 410 } 411 i = db->hsize; 412 while (i != 0) { 413 db->dict[--i].codem1 = BADCODEM1; 414 db->dict[i].cptr = 0; 415 } 416 417 db->unit = unit; 418 db->hdrlen = hdrlen; 419 db->mru = mru; 420#ifndef DEBUG 421 if (debug) 422#endif 423 db->debug = 1; 424 425 bsd_reset(db); 426 427 return 1; 428} 429 430static int 431bsd_comp_init(void *state, u_char *options, int opt_len, int unit, int hdrlen, 432 int debug) 433{ 434 return bsd_init((struct bsd_db *) state, options, opt_len, 435 unit, hdrlen, 0, debug, 0); 436} 437 438static int 439bsd_decomp_init(void *state, u_char *options, int opt_len, int unit, int hdrlen, 440 int mru, int debug) 441{ 442 return bsd_init((struct bsd_db *) state, options, opt_len, 443 unit, hdrlen, mru, debug, 1); 444} 445 446 447/* 448 * compress a packet 449 * One change from the BSD compress command is that when the 450 * code size expands, we do not output a bunch of padding. 451 */ 452int /* new slen */ 453bsd_compress(void *state, 454 struct mbuf **mret /* return compressed mbuf chain here */, 455 struct mbuf *mp /* from here */, 456 int slen, int maxolen) 457{ 458 struct bsd_db *db = (struct bsd_db *) state; 459 int hshift = db->hshift; 460 u_int max_ent = db->max_ent; 461 u_int n_bits = db->n_bits; 462 u_int bitno = 32; 463 uint32_t accm = 0, fcode; 464 struct bsd_dict *dictp; 465 u_char c; 466 int hval, disp, ent, ilen; 467 u_char *rptr, *wptr; 468 u_char *cp_end; 469 int olen; 470 struct mbuf *m; 471 472#define PUTBYTE(v) { \ 473 ++olen; \ 474 if (wptr) { \ 475 *wptr++ = (v); \ 476 if (wptr >= cp_end) { \ 477 m->m_len = wptr - mtod(m, u_char *); \ 478 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 479 m = m->m_next; \ 480 if (m) { \ 481 m->m_len = 0; \ 482 if (maxolen - olen > MLEN) \ 483 MCLGET(m, M_DONTWAIT); \ 484 wptr = mtod(m, u_char *); \ 485 cp_end = wptr + M_TRAILINGSPACE(m); \ 486 } else \ 487 wptr = NULL; \ 488 } \ 489 } \ 490} 491 492#define OUTPUT(ent) { \ 493 bitno -= n_bits; \ 494 accm |= ((ent) << bitno); \ 495 do { \ 496 PUTBYTE(accm >> 24); \ 497 accm <<= 8; \ 498 bitno += 8; \ 499 } while (bitno <= 24); \ 500} 501 502 /* 503 * If the protocol is not in the range we're interested in, 504 * just return without compressing the packet. If it is, 505 * the protocol becomes the first byte to compress. 506 */ 507 rptr = mtod(mp, u_char *); 508 ent = PPP_PROTOCOL(rptr); 509 if (ent < 0x21 || ent > 0xf9) { 510 *mret = NULL; 511 return slen; 512 } 513 514 /* Don't generate compressed packets which are larger than 515 the uncompressed packet. */ 516 if (maxolen > slen) 517 maxolen = slen; 518 519 /* Allocate one mbuf to start with. */ 520 MGET(m, M_DONTWAIT, MT_DATA); 521 *mret = m; 522 if (m != NULL) { 523 m->m_len = 0; 524 if (maxolen + db->hdrlen > MLEN) 525 MCLGET(m, M_DONTWAIT); 526 m->m_data += db->hdrlen; 527 wptr = mtod(m, u_char *); 528 cp_end = wptr + M_TRAILINGSPACE(m); 529 } else 530 wptr = cp_end = NULL; 531 532 /* 533 * Copy the PPP header over, changing the protocol, 534 * and install the 2-byte packet sequence number. 535 */ 536 if (wptr) { 537 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 538 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 539 *wptr++ = 0; /* change the protocol */ 540 *wptr++ = PPP_COMP; 541 *wptr++ = db->seqno >> 8; 542 *wptr++ = db->seqno; 543 } 544 ++db->seqno; 545 546 olen = 0; 547 rptr += PPP_HDRLEN; 548 slen = mp->m_len - PPP_HDRLEN; 549 ilen = slen + 1; 550 for (;;) { 551 if (slen <= 0) { 552 mp = mp->m_next; 553 if (!mp) 554 break; 555 rptr = mtod(mp, u_char *); 556 slen = mp->m_len; 557 if (!slen) 558 continue; /* handle 0-length buffers */ 559 ilen += slen; 560 } 561 562 slen--; 563 c = *rptr++; 564 fcode = BSD_KEY(ent, c); 565 hval = BSD_HASH(ent, c, hshift); 566 dictp = &db->dict[hval]; 567 568 /* Validate and then check the entry. */ 569 if (dictp->codem1 >= max_ent) 570 goto nomatch; 571 if (dictp->f.fcode == fcode) { 572 ent = dictp->codem1+1; 573 continue; /* found (prefix,suffix) */ 574 } 575 576 /* continue probing until a match or invalid entry */ 577 disp = (hval == 0) ? 1 : hval; 578 do { 579 hval += disp; 580 if (hval >= db->hsize) 581 hval -= db->hsize; 582 dictp = &db->dict[hval]; 583 if (dictp->codem1 >= max_ent) 584 goto nomatch; 585 } while (dictp->f.fcode != fcode); 586 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 587 continue; 588 589 nomatch: 590 OUTPUT(ent); /* output the prefix */ 591 592 /* code -> hashtable */ 593 if (max_ent < db->maxmaxcode) { 594 struct bsd_dict *dictp2; 595 /* expand code size if needed */ 596 if (max_ent >= MAXCODE(n_bits)) 597 db->n_bits = ++n_bits; 598 599 /* Invalidate old hash table entry using 600 * this code, and then take it over. 601 */ 602 dictp2 = &db->dict[max_ent+1]; 603 if (db->dict[dictp2->cptr].codem1 == max_ent) 604 db->dict[dictp2->cptr].codem1 = BADCODEM1; 605 dictp2->cptr = hval; 606 dictp->codem1 = max_ent; 607 dictp->f.fcode = fcode; 608 609 db->max_ent = ++max_ent; 610 } 611 ent = c; 612 } 613 614 OUTPUT(ent); /* output the last code */ 615 db->bytes_out += olen; 616 db->in_count += ilen; 617 if (bitno < 32) 618 ++db->bytes_out; /* count complete bytes */ 619 620 if (bsd_check(db)) 621 OUTPUT(CLEAR); /* do not count the CLEAR */ 622 623 /* 624 * Pad dribble bits of last code with ones. 625 * Do not emit a completely useless byte of ones. 626 */ 627 if (bitno != 32) 628 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 629 630 if (m != NULL) { 631 m->m_len = wptr - mtod(m, u_char *); 632 m->m_next = NULL; 633 } 634 635 /* 636 * Increase code size if we would have without the packet 637 * boundary and as the decompressor will. 638 */ 639 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 640 db->n_bits++; 641 642 db->uncomp_bytes += ilen; 643 ++db->uncomp_count; 644 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 645 /* throw away the compressed stuff if it is longer than uncompressed */ 646 if (*mret != NULL) { 647 m_freem(*mret); 648 *mret = NULL; 649 } 650 ++db->incomp_count; 651 db->incomp_bytes += ilen; 652 } else { 653 ++db->comp_count; 654 db->comp_bytes += olen + BSD_OVHD; 655 } 656 657 return olen + PPP_HDRLEN + BSD_OVHD; 658#undef OUTPUT 659#undef PUTBYTE 660} 661 662 663/* 664 * Update the "BSD Compress" dictionary on the receiver for 665 * incompressible data by pretending to compress the incoming data. 666 */ 667static void 668bsd_incomp(void *state, struct mbuf *dmsg) 669{ 670 struct bsd_db *db = (struct bsd_db *) state; 671 u_int hshift = db->hshift; 672 u_int max_ent = db->max_ent; 673 u_int n_bits = db->n_bits; 674 struct bsd_dict *dictp; 675 uint32_t fcode; 676 u_char c; 677 uint32_t hval, disp; 678 int slen, ilen; 679 u_int bitno = 7; 680 u_char *rptr; 681 u_int ent; 682 683 /* 684 * If the protocol is not in the range we're interested in, 685 * just return without looking at the packet. If it is, 686 * the protocol becomes the first byte to "compress". 687 */ 688 rptr = mtod(dmsg, u_char *); 689 ent = PPP_PROTOCOL(rptr); 690 if (ent < 0x21 || ent > 0xf9) 691 return; 692 693 db->seqno++; 694 ilen = 1; /* count the protocol as 1 byte */ 695 rptr += PPP_HDRLEN; 696 slen = dmsg->m_len - PPP_HDRLEN; 697 for (;;) { 698 if (slen <= 0) { 699 dmsg = dmsg->m_next; 700 if (!dmsg) 701 break; 702 rptr = mtod(dmsg, u_char *); 703 slen = dmsg->m_len; 704 continue; 705 } 706 ilen += slen; 707 708 do { 709 c = *rptr++; 710 fcode = BSD_KEY(ent, c); 711 hval = BSD_HASH(ent, c, hshift); 712 dictp = &db->dict[hval]; 713 714 /* validate and then check the entry */ 715 if (dictp->codem1 >= max_ent) 716 goto nomatch; 717 if (dictp->f.fcode == fcode) { 718 ent = dictp->codem1+1; 719 continue; /* found (prefix,suffix) */ 720 } 721 722 /* continue probing until a match or invalid entry */ 723 disp = (hval == 0) ? 1 : hval; 724 do { 725 hval += disp; 726 if (hval >= db->hsize) 727 hval -= db->hsize; 728 dictp = &db->dict[hval]; 729 if (dictp->codem1 >= max_ent) 730 goto nomatch; 731 } while (dictp->f.fcode != fcode); 732 ent = dictp->codem1+1; 733 continue; /* finally found (prefix,suffix) */ 734 735 nomatch: /* output (count) the prefix */ 736 bitno += n_bits; 737 738 /* code -> hashtable */ 739 if (max_ent < db->maxmaxcode) { 740 struct bsd_dict *dictp2; 741 /* expand code size if needed */ 742 if (max_ent >= MAXCODE(n_bits)) 743 db->n_bits = ++n_bits; 744 745 /* Invalidate previous hash table entry 746 * assigned this code, and then take it over. 747 */ 748 dictp2 = &db->dict[max_ent+1]; 749 if (db->dict[dictp2->cptr].codem1 == max_ent) 750 db->dict[dictp2->cptr].codem1 = BADCODEM1; 751 dictp2->cptr = hval; 752 dictp->codem1 = max_ent; 753 dictp->f.fcode = fcode; 754 755 db->max_ent = ++max_ent; 756 db->lens[max_ent] = db->lens[ent]+1; 757 } 758 ent = c; 759 } while (--slen != 0); 760 } 761 bitno += n_bits; /* output (count) the last code */ 762 db->bytes_out += bitno/8; 763 db->in_count += ilen; 764 (void)bsd_check(db); 765 766 ++db->incomp_count; 767 db->incomp_bytes += ilen; 768 ++db->uncomp_count; 769 db->uncomp_bytes += ilen; 770 771 /* Increase code size if we would have without the packet 772 * boundary and as the decompressor will. 773 */ 774 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 775 db->n_bits++; 776} 777 778 779/* 780 * Decompress "BSD Compress". 781 * 782 * Because of patent problems, we return DECOMP_ERROR for errors 783 * found by inspecting the input data and for system problems, but 784 * DECOMP_FATALERROR for any errors which could possibly be said to 785 * be being detected "after" decompression. For DECOMP_ERROR, 786 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 787 * infringing a patent of Motorola's if we do, so we take CCP down 788 * instead. 789 * 790 * Given that the frame has the correct sequence number and a good FCS, 791 * errors such as invalid codes in the input most likely indicate a 792 * bug, so we return DECOMP_FATALERROR for them in order to turn off 793 * compression, even though they are detected by inspecting the input. 794 */ 795int 796bsd_decompress(void *state, struct mbuf *cmp, struct mbuf **dmpp) 797{ 798 struct bsd_db *db = (struct bsd_db *) state; 799 u_int max_ent = db->max_ent; 800 uint32_t accm = 0; 801 u_int bitno = 32; /* 1st valid bit in accm */ 802 u_int n_bits = db->n_bits; 803 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 804 struct bsd_dict *dictp; 805 int explen, i, seq, len; 806 u_int incode, oldcode, finchar; 807 u_char *p, *rptr, *wptr; 808 struct mbuf *m, *dmp, *mret; 809 int adrs, ctrl, ilen; 810 int space, codelen, extra; 811 812 /* 813 * Save the address/control from the PPP header 814 * and then get the sequence number. 815 */ 816 *dmpp = NULL; 817 rptr = mtod(cmp, u_char *); 818 adrs = PPP_ADDRESS(rptr); 819 ctrl = PPP_CONTROL(rptr); 820 rptr += PPP_HDRLEN; 821 len = cmp->m_len - PPP_HDRLEN; 822 seq = 0; 823 for (i = 0; i < 2; ++i) { 824 while (len <= 0) { 825 cmp = cmp->m_next; 826 if (cmp == NULL) 827 return DECOMP_ERROR; 828 rptr = mtod(cmp, u_char *); 829 len = cmp->m_len; 830 } 831 seq = (seq << 8) + *rptr++; 832 --len; 833 } 834 835 /* 836 * Check the sequence number and give up if it differs from 837 * the value we're expecting. 838 */ 839 if (seq != db->seqno) { 840 if (db->debug) 841 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 842 db->unit, seq, db->seqno - 1); 843 return DECOMP_ERROR; 844 } 845 ++db->seqno; 846 847 /* 848 * Allocate one mbuf to start with. 849 */ 850 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 851 if (dmp == NULL) 852 return DECOMP_ERROR; 853 mret = dmp; 854 dmp->m_len = 0; 855 dmp->m_next = NULL; 856 MCLGET(dmp, M_DONTWAIT); 857 dmp->m_data += db->hdrlen; 858 wptr = mtod(dmp, u_char *); 859 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 860 861 /* 862 * Fill in the ppp header, but not the last byte of the protocol 863 * (that comes from the decompressed data). 864 */ 865 wptr[0] = adrs; 866 wptr[1] = ctrl; 867 wptr[2] = 0; 868 wptr += PPP_HDRLEN - 1; 869 870 ilen = len; 871 oldcode = CLEAR; 872 explen = 0; 873 for (;;) { 874 if (len == 0) { 875 cmp = cmp->m_next; 876 if (!cmp) /* quit at end of message */ 877 break; 878 rptr = mtod(cmp, u_char *); 879 len = cmp->m_len; 880 ilen += len; 881 continue; /* handle 0-length buffers */ 882 } 883 884 /* 885 * Accumulate bytes until we have a complete code. 886 * Then get the next code, relying on the 32-bit, 887 * unsigned accm to mask the result. 888 */ 889 bitno -= 8; 890 accm |= *rptr++ << bitno; 891 --len; 892 if (tgtbitno < bitno) 893 continue; 894 incode = accm >> tgtbitno; 895 accm <<= n_bits; 896 bitno += n_bits; 897 898 if (incode == CLEAR) { 899 /* 900 * The dictionary must only be cleared at 901 * the end of a packet. But there could be an 902 * empty mbuf at the end. 903 */ 904 if (len > 0 || cmp->m_next != NULL) { 905 while ((cmp = cmp->m_next) != NULL) 906 len += cmp->m_len; 907 if (len > 0) { 908 m_freem(mret); 909 if (db->debug) 910 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 911 return DECOMP_FATALERROR; /* probably a bug */ 912 } 913 } 914 bsd_clear(db); 915 explen = ilen = 0; 916 break; 917 } 918 919 if (incode > max_ent + 2 || incode > db->maxmaxcode 920 || (incode > max_ent && oldcode == CLEAR)) { 921 m_freem(mret); 922 if (db->debug) { 923 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 924 db->unit, incode, oldcode); 925 printf("max_ent=0x%x explen=%d seqno=%d\n", 926 max_ent, explen, db->seqno); 927 } 928 return DECOMP_FATALERROR; /* probably a bug */ 929 } 930 931 /* Special case for KwKwK string. */ 932 if (incode > max_ent) { 933 finchar = oldcode; 934 extra = 1; 935 } else { 936 finchar = incode; 937 extra = 0; 938 } 939 940 codelen = db->lens[finchar]; 941 explen += codelen + extra; 942 if (explen > db->mru + 1) { 943 m_freem(mret); 944 if (db->debug) { 945 printf("bsd_decomp%d: ran out of mru\n", db->unit); 946#ifdef DEBUG 947 while ((cmp = cmp->m_next) != NULL) 948 len += cmp->m_len; 949 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 950 len, finchar, codelen, explen); 951#endif 952 } 953 return DECOMP_FATALERROR; 954 } 955 956 /* 957 * For simplicity, the decoded characters go in a single mbuf, 958 * so we allocate a single extra cluster mbuf if necessary. 959 */ 960 if ((space -= codelen + extra) < 0) { 961 dmp->m_len = wptr - mtod(dmp, u_char *); 962 MGET(m, M_DONTWAIT, MT_DATA); 963 if (m == NULL) { 964 m_freem(mret); 965 return DECOMP_ERROR; 966 } 967 m->m_len = 0; 968 m->m_next = NULL; 969 dmp->m_next = m; 970 MCLGET(m, M_DONTWAIT); 971 space = M_TRAILINGSPACE(m) - (codelen + extra); 972 if (space < 0) { 973 /* now that's what I call *compression*. */ 974 m_freem(mret); 975 return DECOMP_ERROR; 976 } 977 dmp = m; 978 wptr = mtod(dmp, u_char *); 979 } 980 981 /* 982 * Decode this code and install it in the decompressed buffer. 983 */ 984 p = (wptr += codelen); 985 while (finchar > LAST) { 986 dictp = &db->dict[db->dict[finchar].cptr]; 987#ifdef DEBUG 988 if (--codelen <= 0 || dictp->codem1 != finchar-1) 989 goto bad; 990#endif 991 *--p = dictp->f.hs.suffix; 992 finchar = dictp->f.hs.prefix; 993 } 994 *--p = finchar; 995 996#ifdef DEBUG 997 if (--codelen != 0) 998 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 999 db->unit, codelen, incode, max_ent); 1000#endif 1001 1002 if (extra) /* the KwKwK case again */ 1003 *wptr++ = finchar; 1004 1005 /* 1006 * If not first code in a packet, and 1007 * if not out of code space, then allocate a new code. 1008 * 1009 * Keep the hash table correct so it can be used 1010 * with uncompressed packets. 1011 */ 1012 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1013 struct bsd_dict *dictp2; 1014 uint32_t fcode; 1015 uint32_t hval, disp; 1016 1017 fcode = BSD_KEY(oldcode,finchar); 1018 hval = BSD_HASH(oldcode,finchar,db->hshift); 1019 dictp = &db->dict[hval]; 1020 1021 /* look for a free hash table entry */ 1022 if (dictp->codem1 < max_ent) { 1023 disp = (hval == 0) ? 1 : hval; 1024 do { 1025 hval += disp; 1026 if (hval >= db->hsize) 1027 hval -= db->hsize; 1028 dictp = &db->dict[hval]; 1029 } while (dictp->codem1 < max_ent); 1030 } 1031 1032 /* 1033 * Invalidate previous hash table entry 1034 * assigned this code, and then take it over 1035 */ 1036 dictp2 = &db->dict[max_ent+1]; 1037 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1038 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1039 } 1040 dictp2->cptr = hval; 1041 dictp->codem1 = max_ent; 1042 dictp->f.fcode = fcode; 1043 1044 db->max_ent = ++max_ent; 1045 db->lens[max_ent] = db->lens[oldcode]+1; 1046 1047 /* Expand code size if needed. */ 1048 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1049 db->n_bits = ++n_bits; 1050 tgtbitno = 32-n_bits; 1051 } 1052 } 1053 oldcode = incode; 1054 } 1055 dmp->m_len = wptr - mtod(dmp, u_char *); 1056 1057 /* 1058 * Keep the checkpoint right so that incompressible packets 1059 * clear the dictionary at the right times. 1060 */ 1061 db->bytes_out += ilen; 1062 db->in_count += explen; 1063 if (bsd_check(db) && db->debug) { 1064 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1065 db->unit); 1066 } 1067 1068 ++db->comp_count; 1069 db->comp_bytes += ilen + BSD_OVHD; 1070 ++db->uncomp_count; 1071 db->uncomp_bytes += explen; 1072 1073 *dmpp = mret; 1074 return DECOMP_OK; 1075 1076#ifdef DEBUG 1077 bad: 1078 if (codelen <= 0) { 1079 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1080 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1081 incode, finchar, db->dict[finchar].cptr, max_ent); 1082 } else if (dictp->codem1 != finchar-1) { 1083 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1084 db->unit, incode, finchar); 1085 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1086 db->dict[finchar].cptr, dictp->codem1); 1087 } 1088 m_freem(mret); 1089 return DECOMP_FATALERROR; 1090#endif /* DEBUG */ 1091} 1092 1093MODULE(MODULE_CLASS_MISC, ppp_bsdcomp, NULL); 1094 1095static int 1096ppp_bsdcomp_modcmd(modcmd_t cmd, void *arg) 1097{ 1098 1099 switch (cmd) { 1100 case MODULE_CMD_INIT: 1101 return ppp_register_compressor(&ppp_bsd_compress, 1); 1102 case MODULE_CMD_FINI: 1103 return ppp_unregister_compressor(&ppp_bsd_compress, 1); 1104 case MODULE_CMD_STAT: 1105 return 0; 1106 default: 1107 return ENOTTY; 1108 } 1109 1110 return ENOTTY; 1111} 1112#endif /* DO_BSD_COMPRESS */ 1113