1 /* $OpenBSD: bsd-comp.c,v 1.6 2003/06/02 23:28:11 millert Exp $ */ 2 /* $NetBSD: bsd-comp.c,v 1.6 1996/10/13 02:10:58 christos 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/param.h> 44 #include <sys/types.h> 45 #include <sys/systm.h> 46 #include <sys/mbuf.h> 47 #include <sys/socket.h> 48 #include <net/if.h> 49 #include <net/if_types.h> 50 #include <net/ppp_defs.h> 51 #include <net/if_ppp.h> 52 53 #define PACKETPTR struct mbuf * 54 #include <net/ppp-comp.h> 55 56 #if DO_BSD_COMPRESS 57 /* 58 * PPP "BSD compress" compression 59 * The differences between this compression and the classic BSD LZW 60 * source are obvious from the requirement that the classic code worked 61 * with files while this handles arbitrarily long streams that 62 * are broken into packets. They are: 63 * 64 * When the code size expands, a block of junk is not emitted by 65 * the compressor and not expected by the decompressor. 66 * 67 * New codes are not necessarily assigned every time an old 68 * code is output by the compressor. This is because a packet 69 * end forces a code to be emitted, but does not imply that a 70 * new sequence has been seen. 71 * 72 * The compression ratio is checked at the first end of a packet 73 * after the appropriate gap. Besides simplifying and speeding 74 * things up, this makes it more likely that the transmitter 75 * and receiver will agree when the dictionary is cleared when 76 * compression is not going well. 77 */ 78 79 /* 80 * A dictionary for doing BSD compress. 81 */ 82 struct bsd_db { 83 int totlen; /* length of this structure */ 84 u_int hsize; /* size of the hash table */ 85 u_char hshift; /* used in hash function */ 86 u_char n_bits; /* current bits/code */ 87 u_char maxbits; 88 u_char debug; 89 u_char unit; 90 u_int16_t seqno; /* sequence # of next packet */ 91 u_int hdrlen; /* header length to preallocate */ 92 u_int mru; 93 u_int maxmaxcode; /* largest valid code */ 94 u_int max_ent; /* largest code in use */ 95 u_int in_count; /* uncompressed bytes, aged */ 96 u_int bytes_out; /* compressed bytes, aged */ 97 u_int ratio; /* recent compression ratio */ 98 u_int checkpoint; /* when to next check the ratio */ 99 u_int clear_count; /* times dictionary cleared */ 100 u_int incomp_count; /* incompressible packets */ 101 u_int incomp_bytes; /* incompressible bytes */ 102 u_int uncomp_count; /* uncompressed packets */ 103 u_int uncomp_bytes; /* uncompressed bytes */ 104 u_int comp_count; /* compressed packets */ 105 u_int comp_bytes; /* compressed bytes */ 106 u_int16_t *lens; /* array of lengths of codes */ 107 struct bsd_dict { 108 union { /* hash value */ 109 u_int32_t fcode; 110 struct { 111 #if BYTE_ORDER == LITTLE_ENDIAN 112 u_int16_t prefix; /* preceding code */ 113 u_char suffix; /* last character of new code */ 114 u_char pad; 115 #else 116 u_char pad; 117 u_char suffix; /* last character of new code */ 118 u_int16_t prefix; /* preceding code */ 119 #endif 120 } hs; 121 } f; 122 u_int16_t codem1; /* output of hash table -1 */ 123 u_int16_t cptr; /* map code to hash table entry */ 124 } dict[1]; 125 }; 126 127 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 128 #define BSD_INIT_BITS BSD_MIN_BITS 129 130 static void *bsd_comp_alloc(u_char *options, int opt_len); 131 static void *bsd_decomp_alloc(u_char *options, int opt_len); 132 static void bsd_free(void *state); 133 static int bsd_comp_init(void *state, u_char *options, int opt_len, 134 int unit, int hdrlen, int debug); 135 static int bsd_decomp_init(void *state, u_char *options, int opt_len, 136 int unit, int hdrlen, int mru, int debug); 137 static int bsd_compress(void *state, struct mbuf **mret, 138 struct mbuf *mp, int slen, int maxolen); 139 static void bsd_incomp(void *state, struct mbuf *dmsg); 140 static int bsd_decompress(void *state, struct mbuf *cmp, 141 struct mbuf **dmpp); 142 static void bsd_reset(void *state); 143 static void bsd_comp_stats(void *state, struct compstat *stats); 144 145 /* 146 * Procedures exported to if_ppp.c. 147 */ 148 struct compressor ppp_bsd_compress = { 149 CI_BSD_COMPRESS, /* compress_proto */ 150 bsd_comp_alloc, /* comp_alloc */ 151 bsd_free, /* comp_free */ 152 bsd_comp_init, /* comp_init */ 153 bsd_reset, /* comp_reset */ 154 bsd_compress, /* compress */ 155 bsd_comp_stats, /* comp_stat */ 156 bsd_decomp_alloc, /* decomp_alloc */ 157 bsd_free, /* decomp_free */ 158 bsd_decomp_init, /* decomp_init */ 159 bsd_reset, /* decomp_reset */ 160 bsd_decompress, /* decompress */ 161 bsd_incomp, /* incomp */ 162 bsd_comp_stats, /* decomp_stat */ 163 }; 164 165 /* 166 * the next two codes should not be changed lightly, as they must not 167 * lie within the contiguous general code space. 168 */ 169 #define CLEAR 256 /* table clear output code */ 170 #define FIRST 257 /* first free entry */ 171 #define LAST 255 172 173 #define MAXCODE(b) ((1 << (b)) - 1) 174 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 175 176 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 177 ^ (u_int32_t)(prefix)) 178 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 179 + (u_int32_t)(prefix)) 180 181 #define CHECK_GAP 10000 /* Ratio check interval */ 182 183 #define RATIO_SCALE_LOG 8 184 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 185 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 186 187 static void bsd_clear(struct bsd_db *); 188 static int bsd_check(struct bsd_db *); 189 static void *bsd_alloc(u_char *, int, int); 190 static int bsd_init(struct bsd_db *, u_char *, int, int, int, int, 191 int, int); 192 193 /* 194 * clear the dictionary 195 */ 196 static void 197 bsd_clear(db) 198 struct bsd_db *db; 199 { 200 db->clear_count++; 201 db->max_ent = FIRST-1; 202 db->n_bits = BSD_INIT_BITS; 203 db->ratio = 0; 204 db->bytes_out = 0; 205 db->in_count = 0; 206 db->incomp_count = 0; 207 db->checkpoint = CHECK_GAP; 208 } 209 210 /* 211 * If the dictionary is full, then see if it is time to reset it. 212 * 213 * Compute the compression ratio using fixed-point arithmetic 214 * with 8 fractional bits. 215 * 216 * Since we have an infinite stream instead of a single file, 217 * watch only the local compression ratio. 218 * 219 * Since both peers must reset the dictionary at the same time even in 220 * the absence of CLEAR codes (while packets are incompressible), they 221 * must compute the same ratio. 222 */ 223 static int /* 1=output CLEAR */ 224 bsd_check(db) 225 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 */ 264 static void 265 bsd_comp_stats(state, stats) 266 void *state; 267 struct compstat *stats; 268 { 269 struct bsd_db *db = (struct bsd_db *) state; 270 u_int out; 271 272 stats->unc_bytes = db->uncomp_bytes; 273 stats->unc_packets = db->uncomp_count; 274 stats->comp_bytes = db->comp_bytes; 275 stats->comp_packets = db->comp_count; 276 stats->inc_bytes = db->incomp_bytes; 277 stats->inc_packets = db->incomp_count; 278 stats->ratio = db->in_count; 279 out = db->bytes_out; 280 if (stats->ratio <= 0x7fffff) 281 stats->ratio <<= 8; 282 else 283 out >>= 8; 284 if (out != 0) 285 stats->ratio /= out; 286 } 287 288 /* 289 * Reset state, as on a CCP ResetReq. 290 */ 291 static void 292 bsd_reset(state) 293 void *state; 294 { 295 struct bsd_db *db = (struct bsd_db *) state; 296 297 db->seqno = 0; 298 bsd_clear(db); 299 db->clear_count = 0; 300 } 301 302 /* 303 * Allocate space for a (de) compressor. 304 */ 305 static void * 306 bsd_alloc(options, opt_len, decomp) 307 u_char *options; 308 int opt_len, decomp; 309 { 310 int bits; 311 u_int newlen, hsize, hshift, maxmaxcode; 312 struct bsd_db *db; 313 314 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 315 || options[1] != CILEN_BSD_COMPRESS 316 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 317 return NULL; 318 bits = BSD_NBITS(options[2]); 319 switch (bits) { 320 case 9: /* needs 82152 for both directions */ 321 case 10: /* needs 84144 */ 322 case 11: /* needs 88240 */ 323 case 12: /* needs 96432 */ 324 hsize = 5003; 325 hshift = 4; 326 break; 327 case 13: /* needs 176784 */ 328 hsize = 9001; 329 hshift = 5; 330 break; 331 case 14: /* needs 353744 */ 332 hsize = 18013; 333 hshift = 6; 334 break; 335 case 15: /* needs 691440 */ 336 hsize = 35023; 337 hshift = 7; 338 break; 339 case 16: /* needs 1366160--far too much, */ 340 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 341 /* hshift = 8; */ /* in struct bsd_db */ 342 /* break; */ 343 default: 344 return NULL; 345 } 346 347 maxmaxcode = MAXCODE(bits); 348 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 349 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT); 350 if (!db) 351 return NULL; 352 bzero(db, sizeof(*db) - sizeof(db->dict)); 353 354 if (!decomp) { 355 db->lens = NULL; 356 } else { 357 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]), 358 M_DEVBUF, M_NOWAIT); 359 if (!db->lens) { 360 FREE(db, M_DEVBUF); 361 return NULL; 362 } 363 } 364 365 db->totlen = newlen; 366 db->hsize = hsize; 367 db->hshift = hshift; 368 db->maxmaxcode = maxmaxcode; 369 db->maxbits = bits; 370 371 return (void *) db; 372 } 373 374 static void 375 bsd_free(state) 376 void *state; 377 { 378 struct bsd_db *db = (struct bsd_db *) state; 379 380 if (db->lens) 381 FREE(db->lens, M_DEVBUF); 382 FREE(db, M_DEVBUF); 383 } 384 385 static void * 386 bsd_comp_alloc(options, opt_len) 387 u_char *options; 388 int opt_len; 389 { 390 return bsd_alloc(options, opt_len, 0); 391 } 392 393 static void * 394 bsd_decomp_alloc(options, opt_len) 395 u_char *options; 396 int opt_len; 397 { 398 return bsd_alloc(options, opt_len, 1); 399 } 400 401 /* 402 * Initialize the database. 403 */ 404 static int 405 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 406 struct bsd_db *db; 407 u_char *options; 408 int opt_len, unit, hdrlen, mru, debug, decomp; 409 { 410 int i; 411 412 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 413 || options[1] != CILEN_BSD_COMPRESS 414 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 415 || BSD_NBITS(options[2]) != db->maxbits 416 || (decomp && db->lens == NULL)) 417 return 0; 418 419 if (decomp) { 420 i = LAST+1; 421 while (i != 0) 422 db->lens[--i] = 1; 423 } 424 i = db->hsize; 425 while (i != 0) { 426 db->dict[--i].codem1 = BADCODEM1; 427 db->dict[i].cptr = 0; 428 } 429 430 db->unit = unit; 431 db->hdrlen = hdrlen; 432 db->mru = mru; 433 #ifndef DEBUG 434 if (debug) 435 #endif 436 db->debug = 1; 437 438 bsd_reset(db); 439 440 return 1; 441 } 442 443 static int 444 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 445 void *state; 446 u_char *options; 447 int opt_len, unit, hdrlen, debug; 448 { 449 return bsd_init((struct bsd_db *) state, options, opt_len, 450 unit, hdrlen, 0, debug, 0); 451 } 452 453 static int 454 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 455 void *state; 456 u_char *options; 457 int opt_len, unit, hdrlen, mru, debug; 458 { 459 return bsd_init((struct bsd_db *) state, options, opt_len, 460 unit, hdrlen, mru, debug, 1); 461 } 462 463 464 /* 465 * compress a packet 466 * One change from the BSD compress command is that when the 467 * code size expands, we do not output a bunch of padding. 468 */ 469 int /* new slen */ 470 bsd_compress(state, mret, mp, slen, maxolen) 471 void *state; 472 struct mbuf **mret; /* return compressed mbuf chain here */ 473 struct mbuf *mp; /* from here */ 474 int slen; /* uncompressed length */ 475 int maxolen; /* max compressed length */ 476 { 477 struct bsd_db *db = (struct bsd_db *) state; 478 int hshift = db->hshift; 479 u_int max_ent = db->max_ent; 480 u_int n_bits = db->n_bits; 481 u_int bitno = 32; 482 u_int32_t accm = 0, fcode; 483 struct bsd_dict *dictp; 484 u_char c; 485 int hval, disp, ent, ilen; 486 u_char *rptr, *wptr; 487 u_char *cp_end; 488 int olen; 489 struct mbuf *m; 490 491 #define PUTBYTE(v) { \ 492 ++olen; \ 493 if (wptr) { \ 494 *wptr++ = (v); \ 495 if (wptr >= cp_end) { \ 496 m->m_len = wptr - mtod(m, u_char *); \ 497 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 498 m = m->m_next; \ 499 if (m) { \ 500 m->m_len = 0; \ 501 if (maxolen - olen > MLEN) \ 502 MCLGET(m, M_DONTWAIT); \ 503 wptr = mtod(m, u_char *); \ 504 cp_end = wptr + M_TRAILINGSPACE(m); \ 505 } else \ 506 wptr = NULL; \ 507 } \ 508 } \ 509 } 510 511 #define OUTPUT(ent) { \ 512 bitno -= n_bits; \ 513 accm |= ((ent) << bitno); \ 514 do { \ 515 PUTBYTE(accm >> 24); \ 516 accm <<= 8; \ 517 bitno += 8; \ 518 } while (bitno <= 24); \ 519 } 520 521 /* 522 * If the protocol is not in the range we're interested in, 523 * just return without compressing the packet. If it is, 524 * the protocol becomes the first byte to compress. 525 */ 526 rptr = mtod(mp, u_char *); 527 ent = PPP_PROTOCOL(rptr); 528 if (ent < 0x21 || ent > 0xf9) { 529 *mret = NULL; 530 return slen; 531 } 532 533 /* Don't generate compressed packets which are larger than 534 the uncompressed packet. */ 535 if (maxolen > slen) 536 maxolen = slen; 537 538 /* Allocate one mbuf to start with. */ 539 MGET(m, M_DONTWAIT, MT_DATA); 540 *mret = m; 541 if (m != NULL) { 542 m->m_len = 0; 543 if (maxolen + db->hdrlen > MLEN) 544 MCLGET(m, M_DONTWAIT); 545 m->m_data += db->hdrlen; 546 wptr = mtod(m, u_char *); 547 cp_end = wptr + M_TRAILINGSPACE(m); 548 } else 549 wptr = cp_end = NULL; 550 551 /* 552 * Copy the PPP header over, changing the protocol, 553 * and install the 2-byte packet sequence number. 554 */ 555 if (wptr) { 556 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 557 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 558 *wptr++ = 0; /* change the protocol */ 559 *wptr++ = PPP_COMP; 560 *wptr++ = db->seqno >> 8; 561 *wptr++ = db->seqno; 562 } 563 ++db->seqno; 564 565 olen = 0; 566 rptr += PPP_HDRLEN; 567 slen = mp->m_len - PPP_HDRLEN; 568 ilen = slen + 1; 569 for (;;) { 570 if (slen <= 0) { 571 mp = mp->m_next; 572 if (!mp) 573 break; 574 rptr = mtod(mp, u_char *); 575 slen = mp->m_len; 576 if (!slen) 577 continue; /* handle 0-length buffers */ 578 ilen += slen; 579 } 580 581 slen--; 582 c = *rptr++; 583 fcode = BSD_KEY(ent, c); 584 hval = BSD_HASH(ent, c, hshift); 585 dictp = &db->dict[hval]; 586 587 /* Validate and then check the entry. */ 588 if (dictp->codem1 >= max_ent) 589 goto nomatch; 590 if (dictp->f.fcode == fcode) { 591 ent = dictp->codem1+1; 592 continue; /* found (prefix,suffix) */ 593 } 594 595 /* continue probing until a match or invalid entry */ 596 disp = (hval == 0) ? 1 : hval; 597 do { 598 hval += disp; 599 if (hval >= db->hsize) 600 hval -= db->hsize; 601 dictp = &db->dict[hval]; 602 if (dictp->codem1 >= max_ent) 603 goto nomatch; 604 } while (dictp->f.fcode != fcode); 605 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 606 continue; 607 608 nomatch: 609 OUTPUT(ent); /* output the prefix */ 610 611 /* code -> hashtable */ 612 if (max_ent < db->maxmaxcode) { 613 struct bsd_dict *dictp2; 614 /* expand code size if needed */ 615 if (max_ent >= MAXCODE(n_bits)) 616 db->n_bits = ++n_bits; 617 618 /* Invalidate old hash table entry using 619 * this code, and then take it over. 620 */ 621 dictp2 = &db->dict[max_ent+1]; 622 if (db->dict[dictp2->cptr].codem1 == max_ent) 623 db->dict[dictp2->cptr].codem1 = BADCODEM1; 624 dictp2->cptr = hval; 625 dictp->codem1 = max_ent; 626 dictp->f.fcode = fcode; 627 628 db->max_ent = ++max_ent; 629 } 630 ent = c; 631 } 632 633 OUTPUT(ent); /* output the last code */ 634 db->bytes_out += olen; 635 db->in_count += ilen; 636 if (bitno < 32) 637 ++db->bytes_out; /* count complete bytes */ 638 639 if (bsd_check(db)) 640 OUTPUT(CLEAR); /* do not count the CLEAR */ 641 642 /* 643 * Pad dribble bits of last code with ones. 644 * Do not emit a completely useless byte of ones. 645 */ 646 if (bitno != 32) 647 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 648 649 if (m != NULL) { 650 m->m_len = wptr - mtod(m, u_char *); 651 m->m_next = NULL; 652 } 653 654 /* 655 * Increase code size if we would have without the packet 656 * boundary and as the decompressor will. 657 */ 658 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 659 db->n_bits++; 660 661 db->uncomp_bytes += ilen; 662 ++db->uncomp_count; 663 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 664 /* throw away the compressed stuff if it is longer than uncompressed */ 665 if (*mret != NULL) { 666 m_freem(*mret); 667 *mret = NULL; 668 } 669 ++db->incomp_count; 670 db->incomp_bytes += ilen; 671 } else { 672 ++db->comp_count; 673 db->comp_bytes += olen + BSD_OVHD; 674 } 675 676 return olen + PPP_HDRLEN + BSD_OVHD; 677 #undef OUTPUT 678 #undef PUTBYTE 679 } 680 681 682 /* 683 * Update the "BSD Compress" dictionary on the receiver for 684 * incompressible data by pretending to compress the incoming data. 685 */ 686 static void 687 bsd_incomp(state, dmsg) 688 void *state; 689 struct mbuf *dmsg; 690 { 691 struct bsd_db *db = (struct bsd_db *) state; 692 u_int hshift = db->hshift; 693 u_int max_ent = db->max_ent; 694 u_int n_bits = db->n_bits; 695 struct bsd_dict *dictp; 696 u_int32_t fcode; 697 u_char c; 698 u_int32_t hval, disp; 699 int slen, ilen; 700 u_int bitno = 7; 701 u_char *rptr; 702 u_int ent; 703 704 /* 705 * If the protocol is not in the range we're interested in, 706 * just return without looking at the packet. If it is, 707 * the protocol becomes the first byte to "compress". 708 */ 709 rptr = mtod(dmsg, u_char *); 710 ent = PPP_PROTOCOL(rptr); 711 if (ent < 0x21 || ent > 0xf9) 712 return; 713 714 db->incomp_count++; 715 db->seqno++; 716 ilen = 1; /* count the protocol as 1 byte */ 717 rptr += PPP_HDRLEN; 718 slen = dmsg->m_len - PPP_HDRLEN; 719 for (;;) { 720 if (slen <= 0) { 721 dmsg = dmsg->m_next; 722 if (!dmsg) 723 break; 724 rptr = mtod(dmsg, u_char *); 725 slen = dmsg->m_len; 726 continue; 727 } 728 ilen += slen; 729 730 do { 731 c = *rptr++; 732 fcode = BSD_KEY(ent, c); 733 hval = BSD_HASH(ent, c, hshift); 734 dictp = &db->dict[hval]; 735 736 /* validate and then check the entry */ 737 if (dictp->codem1 >= max_ent) 738 goto nomatch; 739 if (dictp->f.fcode == fcode) { 740 ent = dictp->codem1+1; 741 continue; /* found (prefix,suffix) */ 742 } 743 744 /* continue probing until a match or invalid entry */ 745 disp = (hval == 0) ? 1 : hval; 746 do { 747 hval += disp; 748 if (hval >= db->hsize) 749 hval -= db->hsize; 750 dictp = &db->dict[hval]; 751 if (dictp->codem1 >= max_ent) 752 goto nomatch; 753 } while (dictp->f.fcode != fcode); 754 ent = dictp->codem1+1; 755 continue; /* finally found (prefix,suffix) */ 756 757 nomatch: /* output (count) the prefix */ 758 bitno += n_bits; 759 760 /* code -> hashtable */ 761 if (max_ent < db->maxmaxcode) { 762 struct bsd_dict *dictp2; 763 /* expand code size if needed */ 764 if (max_ent >= MAXCODE(n_bits)) 765 db->n_bits = ++n_bits; 766 767 /* Invalidate previous hash table entry 768 * assigned this code, and then take it over. 769 */ 770 dictp2 = &db->dict[max_ent+1]; 771 if (db->dict[dictp2->cptr].codem1 == max_ent) 772 db->dict[dictp2->cptr].codem1 = BADCODEM1; 773 dictp2->cptr = hval; 774 dictp->codem1 = max_ent; 775 dictp->f.fcode = fcode; 776 777 db->max_ent = ++max_ent; 778 db->lens[max_ent] = db->lens[ent]+1; 779 } 780 ent = c; 781 } while (--slen != 0); 782 } 783 bitno += n_bits; /* output (count) the last code */ 784 db->bytes_out += bitno/8; 785 db->in_count += ilen; 786 (void)bsd_check(db); 787 788 ++db->incomp_count; 789 db->incomp_bytes += ilen; 790 ++db->uncomp_count; 791 db->uncomp_bytes += ilen; 792 793 /* Increase code size if we would have without the packet 794 * boundary and as the decompressor will. 795 */ 796 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 797 db->n_bits++; 798 } 799 800 801 /* 802 * Decompress "BSD Compress". 803 * 804 * Because of patent problems, we return DECOMP_ERROR for errors 805 * found by inspecting the input data and for system problems, but 806 * DECOMP_FATALERROR for any errors which could possibly be said to 807 * be being detected "after" decompression. For DECOMP_ERROR, 808 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 809 * infringing a patent of Motorola's if we do, so we take CCP down 810 * instead. 811 * 812 * Given that the frame has the correct sequence number and a good FCS, 813 * errors such as invalid codes in the input most likely indicate a 814 * bug, so we return DECOMP_FATALERROR for them in order to turn off 815 * compression, even though they are detected by inspecting the input. 816 */ 817 int 818 bsd_decompress(state, cmp, dmpp) 819 void *state; 820 struct mbuf *cmp, **dmpp; 821 { 822 struct bsd_db *db = (struct bsd_db *) state; 823 u_int max_ent = db->max_ent; 824 u_int32_t accm = 0; 825 u_int bitno = 32; /* 1st valid bit in accm */ 826 u_int n_bits = db->n_bits; 827 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 828 struct bsd_dict *dictp; 829 int explen, i, seq, len; 830 u_int incode, oldcode, finchar; 831 u_char *p, *rptr, *wptr; 832 struct mbuf *m, *dmp, *mret; 833 int adrs, ctrl, ilen; 834 int space, codelen, extra; 835 836 /* 837 * Save the address/control from the PPP header 838 * and then get the sequence number. 839 */ 840 *dmpp = NULL; 841 rptr = mtod(cmp, u_char *); 842 adrs = PPP_ADDRESS(rptr); 843 ctrl = PPP_CONTROL(rptr); 844 rptr += PPP_HDRLEN; 845 len = cmp->m_len - PPP_HDRLEN; 846 seq = 0; 847 for (i = 0; i < 2; ++i) { 848 while (len <= 0) { 849 cmp = cmp->m_next; 850 if (cmp == NULL) 851 return DECOMP_ERROR; 852 rptr = mtod(cmp, u_char *); 853 len = cmp->m_len; 854 } 855 seq = (seq << 8) + *rptr++; 856 --len; 857 } 858 859 /* 860 * Check the sequence number and give up if it differs from 861 * the value we're expecting. 862 */ 863 if (seq != db->seqno) { 864 if (db->debug) 865 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 866 db->unit, seq, db->seqno - 1); 867 return DECOMP_ERROR; 868 } 869 ++db->seqno; 870 871 /* 872 * Allocate one mbuf to start with. 873 */ 874 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 875 if (dmp == NULL) 876 return DECOMP_ERROR; 877 mret = dmp; 878 dmp->m_len = 0; 879 dmp->m_next = NULL; 880 MCLGET(dmp, M_DONTWAIT); 881 dmp->m_data += db->hdrlen; 882 wptr = mtod(dmp, u_char *); 883 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 884 885 /* 886 * Fill in the ppp header, but not the last byte of the protocol 887 * (that comes from the decompressed data). 888 */ 889 wptr[0] = adrs; 890 wptr[1] = ctrl; 891 wptr[2] = 0; 892 wptr += PPP_HDRLEN - 1; 893 894 ilen = len; 895 oldcode = CLEAR; 896 explen = 0; 897 for (;;) { 898 if (len == 0) { 899 cmp = cmp->m_next; 900 if (!cmp) /* quit at end of message */ 901 break; 902 rptr = mtod(cmp, u_char *); 903 len = cmp->m_len; 904 ilen += len; 905 continue; /* handle 0-length buffers */ 906 } 907 908 /* 909 * Accumulate bytes until we have a complete code. 910 * Then get the next code, relying on the 32-bit, 911 * unsigned accm to mask the result. 912 */ 913 bitno -= 8; 914 accm |= *rptr++ << bitno; 915 --len; 916 if (tgtbitno < bitno) 917 continue; 918 incode = accm >> tgtbitno; 919 accm <<= n_bits; 920 bitno += n_bits; 921 922 if (incode == CLEAR) { 923 /* 924 * The dictionary must only be cleared at 925 * the end of a packet. But there could be an 926 * empty mbuf at the end. 927 */ 928 if (len > 0 || cmp->m_next != NULL) { 929 while ((cmp = cmp->m_next) != NULL) 930 len += cmp->m_len; 931 if (len > 0) { 932 m_freem(mret); 933 if (db->debug) 934 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 935 return DECOMP_FATALERROR; /* probably a bug */ 936 } 937 } 938 bsd_clear(db); 939 explen = ilen = 0; 940 break; 941 } 942 943 if (incode > max_ent + 2 || incode > db->maxmaxcode 944 || (incode > max_ent && oldcode == CLEAR)) { 945 m_freem(mret); 946 if (db->debug) { 947 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 948 db->unit, incode, oldcode); 949 printf("max_ent=0x%x explen=%d seqno=%d\n", 950 max_ent, explen, db->seqno); 951 } 952 return DECOMP_FATALERROR; /* probably a bug */ 953 } 954 955 /* Special case for KwKwK string. */ 956 if (incode > max_ent) { 957 finchar = oldcode; 958 extra = 1; 959 } else { 960 finchar = incode; 961 extra = 0; 962 } 963 964 codelen = db->lens[finchar]; 965 explen += codelen + extra; 966 if (explen > db->mru + 1) { 967 m_freem(mret); 968 if (db->debug) { 969 printf("bsd_decomp%d: ran out of mru\n", db->unit); 970 #ifdef DEBUG 971 while ((cmp = cmp->m_next) != NULL) 972 len += cmp->m_len; 973 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 974 len, finchar, codelen, explen); 975 #endif 976 } 977 return DECOMP_FATALERROR; 978 } 979 980 /* 981 * For simplicity, the decoded characters go in a single mbuf, 982 * so we allocate a single extra cluster mbuf if necessary. 983 */ 984 if ((space -= codelen + extra) < 0) { 985 dmp->m_len = wptr - mtod(dmp, u_char *); 986 MGET(m, M_DONTWAIT, MT_DATA); 987 if (m == NULL) { 988 m_freem(mret); 989 return DECOMP_ERROR; 990 } 991 m->m_len = 0; 992 m->m_next = NULL; 993 dmp->m_next = m; 994 MCLGET(m, M_DONTWAIT); 995 space = M_TRAILINGSPACE(m) - (codelen + extra); 996 if (space < 0) { 997 /* now that's what I call *compression*. */ 998 m_freem(mret); 999 return DECOMP_ERROR; 1000 } 1001 dmp = m; 1002 wptr = mtod(dmp, u_char *); 1003 } 1004 1005 /* 1006 * Decode this code and install it in the decompressed buffer. 1007 */ 1008 p = (wptr += codelen); 1009 while (finchar > LAST) { 1010 dictp = &db->dict[db->dict[finchar].cptr]; 1011 #ifdef DEBUG 1012 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1013 goto bad; 1014 #endif 1015 *--p = dictp->f.hs.suffix; 1016 finchar = dictp->f.hs.prefix; 1017 } 1018 *--p = finchar; 1019 1020 #ifdef DEBUG 1021 if (--codelen != 0) 1022 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1023 db->unit, codelen, incode, max_ent); 1024 #endif 1025 1026 if (extra) /* the KwKwK case again */ 1027 *wptr++ = finchar; 1028 1029 /* 1030 * If not first code in a packet, and 1031 * if not out of code space, then allocate a new code. 1032 * 1033 * Keep the hash table correct so it can be used 1034 * with uncompressed packets. 1035 */ 1036 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1037 struct bsd_dict *dictp2; 1038 u_int32_t fcode; 1039 u_int32_t hval, disp; 1040 1041 fcode = BSD_KEY(oldcode,finchar); 1042 hval = BSD_HASH(oldcode,finchar,db->hshift); 1043 dictp = &db->dict[hval]; 1044 1045 /* look for a free hash table entry */ 1046 if (dictp->codem1 < max_ent) { 1047 disp = (hval == 0) ? 1 : hval; 1048 do { 1049 hval += disp; 1050 if (hval >= db->hsize) 1051 hval -= db->hsize; 1052 dictp = &db->dict[hval]; 1053 } while (dictp->codem1 < max_ent); 1054 } 1055 1056 /* 1057 * Invalidate previous hash table entry 1058 * assigned this code, and then take it over 1059 */ 1060 dictp2 = &db->dict[max_ent+1]; 1061 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1062 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1063 } 1064 dictp2->cptr = hval; 1065 dictp->codem1 = max_ent; 1066 dictp->f.fcode = fcode; 1067 1068 db->max_ent = ++max_ent; 1069 db->lens[max_ent] = db->lens[oldcode]+1; 1070 1071 /* Expand code size if needed. */ 1072 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1073 db->n_bits = ++n_bits; 1074 tgtbitno = 32-n_bits; 1075 } 1076 } 1077 oldcode = incode; 1078 } 1079 dmp->m_len = wptr - mtod(dmp, u_char *); 1080 1081 /* 1082 * Keep the checkpoint right so that incompressible packets 1083 * clear the dictionary at the right times. 1084 */ 1085 db->bytes_out += ilen; 1086 db->in_count += explen; 1087 if (bsd_check(db) && db->debug) { 1088 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1089 db->unit); 1090 } 1091 1092 ++db->comp_count; 1093 db->comp_bytes += ilen + BSD_OVHD; 1094 ++db->uncomp_count; 1095 db->uncomp_bytes += explen; 1096 1097 *dmpp = mret; 1098 return DECOMP_OK; 1099 1100 #ifdef DEBUG 1101 bad: 1102 if (codelen <= 0) { 1103 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1104 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1105 incode, finchar, db->dict[finchar].cptr, max_ent); 1106 } else if (dictp->codem1 != finchar-1) { 1107 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1108 db->unit, incode, finchar); 1109 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1110 db->dict[finchar].cptr, dictp->codem1); 1111 } 1112 m_freem(mret); 1113 return DECOMP_FATALERROR; 1114 #endif /* DEBUG */ 1115 } 1116 #endif /* DO_BSD_COMPRESS */ 1117