1 /* $OpenBSD: bsd-comp.c,v 1.11 2015/07/15 22:16:41 deraadt 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_var.h> 50 #include <net/if_types.h> 51 #include <net/ppp_defs.h> 52 #include <net/if_ppp.h> 53 54 #define PACKETPTR struct mbuf * 55 #include <net/ppp-comp.h> 56 57 #if DO_BSD_COMPRESS 58 /* 59 * PPP "BSD compress" compression 60 * The differences between this compression and the classic BSD LZW 61 * source are obvious from the requirement that the classic code worked 62 * with files while this handles arbitrarily long streams that 63 * are broken into packets. They are: 64 * 65 * When the code size expands, a block of junk is not emitted by 66 * the compressor and not expected by the decompressor. 67 * 68 * New codes are not necessarily assigned every time an old 69 * code is output by the compressor. This is because a packet 70 * end forces a code to be emitted, but does not imply that a 71 * new sequence has been seen. 72 * 73 * The compression ratio is checked at the first end of a packet 74 * after the appropriate gap. Besides simplifying and speeding 75 * things up, this makes it more likely that the transmitter 76 * and receiver will agree when the dictionary is cleared when 77 * compression is not going well. 78 */ 79 80 /* 81 * A dictionary for doing BSD compress. 82 */ 83 struct bsd_db { 84 int totlen; /* length of this structure */ 85 u_int hsize; /* size of the hash table */ 86 u_char hshift; /* used in hash function */ 87 u_char n_bits; /* current bits/code */ 88 u_char maxbits; 89 u_char debug; 90 u_char unit; 91 u_int16_t seqno; /* sequence # of next packet */ 92 u_int hdrlen; /* header length to preallocate */ 93 u_int mru; 94 u_int maxmaxcode; /* largest valid code */ 95 u_int max_ent; /* largest code in use */ 96 u_int in_count; /* uncompressed bytes, aged */ 97 u_int bytes_out; /* compressed bytes, aged */ 98 u_int ratio; /* recent compression ratio */ 99 u_int checkpoint; /* when to next check the ratio */ 100 u_int clear_count; /* times dictionary cleared */ 101 u_int incomp_count; /* incompressible packets */ 102 u_int incomp_bytes; /* incompressible bytes */ 103 u_int uncomp_count; /* uncompressed packets */ 104 u_int uncomp_bytes; /* uncompressed bytes */ 105 u_int comp_count; /* compressed packets */ 106 u_int comp_bytes; /* compressed bytes */ 107 u_int16_t *lens; /* array of lengths of codes */ 108 struct bsd_dict { 109 union { /* hash value */ 110 u_int32_t fcode; 111 struct { 112 #if BYTE_ORDER == LITTLE_ENDIAN 113 u_int16_t prefix; /* preceding code */ 114 u_char suffix; /* last character of new code */ 115 u_char pad; 116 #else 117 u_char pad; 118 u_char suffix; /* last character of new code */ 119 u_int16_t prefix; /* preceding code */ 120 #endif 121 } hs; 122 } f; 123 u_int16_t codem1; /* output of hash table -1 */ 124 u_int16_t cptr; /* map code to hash table entry */ 125 } dict[1]; 126 }; 127 128 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 129 #define BSD_INIT_BITS BSD_MIN_BITS 130 131 static void *bsd_comp_alloc(u_char *options, int opt_len); 132 static void *bsd_decomp_alloc(u_char *options, int opt_len); 133 static void bsd_free(void *state); 134 static int bsd_comp_init(void *state, u_char *options, int opt_len, 135 int unit, int hdrlen, int debug); 136 static int bsd_decomp_init(void *state, u_char *options, int opt_len, 137 int unit, int hdrlen, int mru, int debug); 138 static int bsd_compress(void *state, struct mbuf **mret, 139 struct mbuf *mp, int slen, int maxolen); 140 static void bsd_incomp(void *state, struct mbuf *dmsg); 141 static int bsd_decompress(void *state, struct mbuf *cmp, 142 struct mbuf **dmpp); 143 static void bsd_reset(void *state); 144 static void bsd_comp_stats(void *state, struct compstat *stats); 145 146 /* 147 * Procedures exported to if_ppp.c. 148 */ 149 struct compressor ppp_bsd_compress = { 150 CI_BSD_COMPRESS, /* compress_proto */ 151 bsd_comp_alloc, /* comp_alloc */ 152 bsd_free, /* comp_free */ 153 bsd_comp_init, /* comp_init */ 154 bsd_reset, /* comp_reset */ 155 bsd_compress, /* compress */ 156 bsd_comp_stats, /* comp_stat */ 157 bsd_decomp_alloc, /* decomp_alloc */ 158 bsd_free, /* decomp_free */ 159 bsd_decomp_init, /* decomp_init */ 160 bsd_reset, /* decomp_reset */ 161 bsd_decompress, /* decompress */ 162 bsd_incomp, /* incomp */ 163 bsd_comp_stats, /* decomp_stat */ 164 }; 165 166 /* 167 * the next two codes should not be changed lightly, as they must not 168 * lie within the contiguous general code space. 169 */ 170 #define CLEAR 256 /* table clear output code */ 171 #define FIRST 257 /* first free entry */ 172 #define LAST 255 173 174 #define MAXCODE(b) ((1 << (b)) - 1) 175 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 176 177 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 178 ^ (u_int32_t)(prefix)) 179 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 180 + (u_int32_t)(prefix)) 181 182 #define CHECK_GAP 10000 /* Ratio check interval */ 183 184 #define RATIO_SCALE_LOG 8 185 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 186 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 187 188 static void bsd_clear(struct bsd_db *); 189 static int bsd_check(struct bsd_db *); 190 static void *bsd_alloc(u_char *, int, int); 191 static int bsd_init(struct bsd_db *, u_char *, int, int, int, int, 192 int, int); 193 194 /* 195 * clear the dictionary 196 */ 197 static void 198 bsd_clear(db) 199 struct bsd_db *db; 200 { 201 db->clear_count++; 202 db->max_ent = FIRST-1; 203 db->n_bits = BSD_INIT_BITS; 204 db->ratio = 0; 205 db->bytes_out = 0; 206 db->in_count = 0; 207 db->incomp_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 */ 224 static int /* 1=output CLEAR */ 225 bsd_check(db) 226 struct bsd_db *db; 227 { 228 u_int new_ratio; 229 230 if (db->in_count >= db->checkpoint) { 231 /* age the ratio by limiting the size of the counts */ 232 if (db->in_count >= RATIO_MAX 233 || db->bytes_out >= RATIO_MAX) { 234 db->in_count -= db->in_count/4; 235 db->bytes_out -= db->bytes_out/4; 236 } 237 238 db->checkpoint = db->in_count + CHECK_GAP; 239 240 if (db->max_ent >= db->maxmaxcode) { 241 /* Reset the dictionary only if the ratio is worse, 242 * or if it looks as if it has been poisoned 243 * by incompressible data. 244 * 245 * This does not overflow, because 246 * db->in_count <= RATIO_MAX. 247 */ 248 new_ratio = db->in_count << RATIO_SCALE_LOG; 249 if (db->bytes_out != 0) 250 new_ratio /= db->bytes_out; 251 252 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 253 bsd_clear(db); 254 return 1; 255 } 256 db->ratio = new_ratio; 257 } 258 } 259 return 0; 260 } 261 262 /* 263 * Return statistics. 264 */ 265 static void 266 bsd_comp_stats(state, stats) 267 void *state; 268 struct compstat *stats; 269 { 270 struct bsd_db *db = (struct bsd_db *) state; 271 u_int out; 272 273 stats->unc_bytes = db->uncomp_bytes; 274 stats->unc_packets = db->uncomp_count; 275 stats->comp_bytes = db->comp_bytes; 276 stats->comp_packets = db->comp_count; 277 stats->inc_bytes = db->incomp_bytes; 278 stats->inc_packets = db->incomp_count; 279 stats->ratio = db->in_count; 280 out = db->bytes_out; 281 if (stats->ratio <= 0x7fffff) 282 stats->ratio <<= 8; 283 else 284 out >>= 8; 285 if (out != 0) 286 stats->ratio /= out; 287 } 288 289 /* 290 * Reset state, as on a CCP ResetReq. 291 */ 292 static void 293 bsd_reset(state) 294 void *state; 295 { 296 struct bsd_db *db = (struct bsd_db *) state; 297 298 db->seqno = 0; 299 bsd_clear(db); 300 db->clear_count = 0; 301 } 302 303 /* 304 * Allocate space for a (de) compressor. 305 */ 306 static void * 307 bsd_alloc(options, opt_len, decomp) 308 u_char *options; 309 int opt_len, decomp; 310 { 311 int bits; 312 u_int newlen, hsize, hshift, maxmaxcode; 313 struct bsd_db *db; 314 315 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 316 || options[1] != CILEN_BSD_COMPRESS 317 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 318 return NULL; 319 bits = BSD_NBITS(options[2]); 320 switch (bits) { 321 case 9: /* needs 82152 for both directions */ 322 case 10: /* needs 84144 */ 323 case 11: /* needs 88240 */ 324 case 12: /* needs 96432 */ 325 hsize = 5003; 326 hshift = 4; 327 break; 328 case 13: /* needs 176784 */ 329 hsize = 9001; 330 hshift = 5; 331 break; 332 case 14: /* needs 353744 */ 333 hsize = 18013; 334 hshift = 6; 335 break; 336 case 15: /* needs 691440 */ 337 hsize = 35023; 338 hshift = 7; 339 break; 340 case 16: /* needs 1366160--far too much, */ 341 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 342 /* hshift = 8; */ /* in struct bsd_db */ 343 /* break; */ 344 default: 345 return NULL; 346 } 347 348 maxmaxcode = MAXCODE(bits); 349 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 350 db = malloc(newlen, M_DEVBUF, M_NOWAIT|M_ZERO); 351 if (!db) 352 return NULL; 353 354 if (!decomp) { 355 db->lens = NULL; 356 } else { 357 db->lens = mallocarray(maxmaxcode + 1, sizeof(db->lens[0]), M_DEVBUF, 358 M_NOWAIT); 359 if (!db->lens) { 360 free(db, M_DEVBUF, 0); 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, 0); 382 free(db, M_DEVBUF, 0); 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 m_freem(*mret); 666 *mret = NULL; 667 668 ++db->incomp_count; 669 db->incomp_bytes += ilen; 670 } else { 671 ++db->comp_count; 672 db->comp_bytes += olen + BSD_OVHD; 673 } 674 675 return olen + PPP_HDRLEN + BSD_OVHD; 676 #undef OUTPUT 677 #undef PUTBYTE 678 } 679 680 681 /* 682 * Update the "BSD Compress" dictionary on the receiver for 683 * incompressible data by pretending to compress the incoming data. 684 */ 685 static void 686 bsd_incomp(state, dmsg) 687 void *state; 688 struct mbuf *dmsg; 689 { 690 struct bsd_db *db = (struct bsd_db *) state; 691 u_int hshift = db->hshift; 692 u_int max_ent = db->max_ent; 693 u_int n_bits = db->n_bits; 694 struct bsd_dict *dictp; 695 u_int32_t fcode; 696 u_char c; 697 u_int32_t hval, disp; 698 int slen, ilen; 699 u_int bitno = 7; 700 u_char *rptr; 701 u_int ent; 702 703 /* 704 * If the protocol is not in the range we're interested in, 705 * just return without looking at the packet. If it is, 706 * the protocol becomes the first byte to "compress". 707 */ 708 rptr = mtod(dmsg, u_char *); 709 ent = PPP_PROTOCOL(rptr); 710 if (ent < 0x21 || ent > 0xf9) 711 return; 712 713 db->incomp_count++; 714 db->seqno++; 715 ilen = 1; /* count the protocol as 1 byte */ 716 rptr += PPP_HDRLEN; 717 slen = dmsg->m_len - PPP_HDRLEN; 718 for (;;) { 719 if (slen <= 0) { 720 dmsg = dmsg->m_next; 721 if (!dmsg) 722 break; 723 rptr = mtod(dmsg, u_char *); 724 slen = dmsg->m_len; 725 continue; 726 } 727 ilen += slen; 728 729 do { 730 c = *rptr++; 731 fcode = BSD_KEY(ent, c); 732 hval = BSD_HASH(ent, c, hshift); 733 dictp = &db->dict[hval]; 734 735 /* validate and then check the entry */ 736 if (dictp->codem1 >= max_ent) 737 goto nomatch; 738 if (dictp->f.fcode == fcode) { 739 ent = dictp->codem1+1; 740 continue; /* found (prefix,suffix) */ 741 } 742 743 /* continue probing until a match or invalid entry */ 744 disp = (hval == 0) ? 1 : hval; 745 do { 746 hval += disp; 747 if (hval >= db->hsize) 748 hval -= db->hsize; 749 dictp = &db->dict[hval]; 750 if (dictp->codem1 >= max_ent) 751 goto nomatch; 752 } while (dictp->f.fcode != fcode); 753 ent = dictp->codem1+1; 754 continue; /* finally found (prefix,suffix) */ 755 756 nomatch: /* output (count) the prefix */ 757 bitno += n_bits; 758 759 /* code -> hashtable */ 760 if (max_ent < db->maxmaxcode) { 761 struct bsd_dict *dictp2; 762 /* expand code size if needed */ 763 if (max_ent >= MAXCODE(n_bits)) 764 db->n_bits = ++n_bits; 765 766 /* Invalidate previous hash table entry 767 * assigned this code, and then take it over. 768 */ 769 dictp2 = &db->dict[max_ent+1]; 770 if (db->dict[dictp2->cptr].codem1 == max_ent) 771 db->dict[dictp2->cptr].codem1 = BADCODEM1; 772 dictp2->cptr = hval; 773 dictp->codem1 = max_ent; 774 dictp->f.fcode = fcode; 775 776 db->max_ent = ++max_ent; 777 db->lens[max_ent] = db->lens[ent]+1; 778 } 779 ent = c; 780 } while (--slen != 0); 781 } 782 bitno += n_bits; /* output (count) the last code */ 783 db->bytes_out += bitno/8; 784 db->in_count += ilen; 785 (void)bsd_check(db); 786 787 ++db->incomp_count; 788 db->incomp_bytes += ilen; 789 ++db->uncomp_count; 790 db->uncomp_bytes += ilen; 791 792 /* Increase code size if we would have without the packet 793 * boundary and as the decompressor will. 794 */ 795 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 796 db->n_bits++; 797 } 798 799 800 /* 801 * Decompress "BSD Compress". 802 * 803 * Because of patent problems, we return DECOMP_ERROR for errors 804 * found by inspecting the input data and for system problems, but 805 * DECOMP_FATALERROR for any errors which could possibly be said to 806 * be being detected "after" decompression. For DECOMP_ERROR, 807 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 808 * infringing a patent of Motorola's if we do, so we take CCP down 809 * instead. 810 * 811 * Given that the frame has the correct sequence number and a good FCS, 812 * errors such as invalid codes in the input most likely indicate a 813 * bug, so we return DECOMP_FATALERROR for them in order to turn off 814 * compression, even though they are detected by inspecting the input. 815 */ 816 int 817 bsd_decompress(state, cmp, dmpp) 818 void *state; 819 struct mbuf *cmp, **dmpp; 820 { 821 struct bsd_db *db = (struct bsd_db *) state; 822 u_int max_ent = db->max_ent; 823 u_int32_t accm = 0; 824 u_int bitno = 32; /* 1st valid bit in accm */ 825 u_int n_bits = db->n_bits; 826 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 827 struct bsd_dict *dictp; 828 int explen, i, seq, len; 829 u_int incode, oldcode, finchar; 830 u_char *p, *rptr, *wptr; 831 struct mbuf *m, *dmp, *mret; 832 int adrs, ctrl, ilen; 833 int space, codelen, extra; 834 835 /* 836 * Save the address/control from the PPP header 837 * and then get the sequence number. 838 */ 839 *dmpp = NULL; 840 rptr = mtod(cmp, u_char *); 841 adrs = PPP_ADDRESS(rptr); 842 ctrl = PPP_CONTROL(rptr); 843 rptr += PPP_HDRLEN; 844 len = cmp->m_len - PPP_HDRLEN; 845 seq = 0; 846 for (i = 0; i < 2; ++i) { 847 while (len <= 0) { 848 cmp = cmp->m_next; 849 if (cmp == NULL) 850 return DECOMP_ERROR; 851 rptr = mtod(cmp, u_char *); 852 len = cmp->m_len; 853 } 854 seq = (seq << 8) + *rptr++; 855 --len; 856 } 857 858 /* 859 * Check the sequence number and give up if it differs from 860 * the value we're expecting. 861 */ 862 if (seq != db->seqno) { 863 if (db->debug) 864 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 865 db->unit, seq, db->seqno - 1); 866 return DECOMP_ERROR; 867 } 868 ++db->seqno; 869 870 /* 871 * Allocate one mbuf to start with. 872 */ 873 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 874 if (dmp == NULL) 875 return DECOMP_ERROR; 876 mret = dmp; 877 dmp->m_len = 0; 878 dmp->m_next = NULL; 879 MCLGET(dmp, M_DONTWAIT); 880 dmp->m_data += db->hdrlen; 881 wptr = mtod(dmp, u_char *); 882 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 883 884 /* 885 * Fill in the ppp header, but not the last byte of the protocol 886 * (that comes from the decompressed data). 887 */ 888 wptr[0] = adrs; 889 wptr[1] = ctrl; 890 wptr[2] = 0; 891 wptr += PPP_HDRLEN - 1; 892 893 ilen = len; 894 oldcode = CLEAR; 895 explen = 0; 896 for (;;) { 897 if (len == 0) { 898 cmp = cmp->m_next; 899 if (!cmp) /* quit at end of message */ 900 break; 901 rptr = mtod(cmp, u_char *); 902 len = cmp->m_len; 903 ilen += len; 904 continue; /* handle 0-length buffers */ 905 } 906 907 /* 908 * Accumulate bytes until we have a complete code. 909 * Then get the next code, relying on the 32-bit, 910 * unsigned accm to mask the result. 911 */ 912 bitno -= 8; 913 accm |= *rptr++ << bitno; 914 --len; 915 if (tgtbitno < bitno) 916 continue; 917 incode = accm >> tgtbitno; 918 accm <<= n_bits; 919 bitno += n_bits; 920 921 if (incode == CLEAR) { 922 /* 923 * The dictionary must only be cleared at 924 * the end of a packet. But there could be an 925 * empty mbuf at the end. 926 */ 927 if (len > 0 || cmp->m_next != NULL) { 928 while ((cmp = cmp->m_next) != NULL) 929 len += cmp->m_len; 930 if (len > 0) { 931 m_freem(mret); 932 if (db->debug) 933 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 934 return DECOMP_FATALERROR; /* probably a bug */ 935 } 936 } 937 bsd_clear(db); 938 explen = ilen = 0; 939 break; 940 } 941 942 if (incode > max_ent + 2 || incode > db->maxmaxcode 943 || (incode > max_ent && oldcode == CLEAR)) { 944 m_freem(mret); 945 if (db->debug) { 946 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 947 db->unit, incode, oldcode); 948 printf("max_ent=0x%x explen=%d seqno=%d\n", 949 max_ent, explen, db->seqno); 950 } 951 return DECOMP_FATALERROR; /* probably a bug */ 952 } 953 954 /* Special case for KwKwK string. */ 955 if (incode > max_ent) { 956 finchar = oldcode; 957 extra = 1; 958 } else { 959 finchar = incode; 960 extra = 0; 961 } 962 963 codelen = db->lens[finchar]; 964 explen += codelen + extra; 965 if (explen > db->mru + 1) { 966 m_freem(mret); 967 if (db->debug) { 968 printf("bsd_decomp%d: ran out of mru\n", db->unit); 969 #ifdef DEBUG 970 while ((cmp = cmp->m_next) != NULL) 971 len += cmp->m_len; 972 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 973 len, finchar, codelen, explen); 974 #endif 975 } 976 return DECOMP_FATALERROR; 977 } 978 979 /* 980 * For simplicity, the decoded characters go in a single mbuf, 981 * so we allocate a single extra cluster mbuf if necessary. 982 */ 983 if ((space -= codelen + extra) < 0) { 984 dmp->m_len = wptr - mtod(dmp, u_char *); 985 MGET(m, M_DONTWAIT, MT_DATA); 986 if (m == NULL) { 987 m_freem(mret); 988 return DECOMP_ERROR; 989 } 990 m->m_len = 0; 991 m->m_next = NULL; 992 dmp->m_next = m; 993 MCLGET(m, M_DONTWAIT); 994 space = M_TRAILINGSPACE(m) - (codelen + extra); 995 if (space < 0) { 996 /* now that's what I call *compression*. */ 997 m_freem(mret); 998 return DECOMP_ERROR; 999 } 1000 dmp = m; 1001 wptr = mtod(dmp, u_char *); 1002 } 1003 1004 /* 1005 * Decode this code and install it in the decompressed buffer. 1006 */ 1007 p = (wptr += codelen); 1008 while (finchar > LAST) { 1009 dictp = &db->dict[db->dict[finchar].cptr]; 1010 #ifdef DEBUG 1011 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1012 goto bad; 1013 #endif 1014 *--p = dictp->f.hs.suffix; 1015 finchar = dictp->f.hs.prefix; 1016 } 1017 *--p = finchar; 1018 1019 #ifdef DEBUG 1020 if (--codelen != 0) 1021 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1022 db->unit, codelen, incode, max_ent); 1023 #endif 1024 1025 if (extra) /* the KwKwK case again */ 1026 *wptr++ = finchar; 1027 1028 /* 1029 * If not first code in a packet, and 1030 * if not out of code space, then allocate a new code. 1031 * 1032 * Keep the hash table correct so it can be used 1033 * with uncompressed packets. 1034 */ 1035 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1036 struct bsd_dict *dictp2; 1037 u_int32_t fcode; 1038 u_int32_t hval, disp; 1039 1040 fcode = BSD_KEY(oldcode,finchar); 1041 hval = BSD_HASH(oldcode,finchar,db->hshift); 1042 dictp = &db->dict[hval]; 1043 1044 /* look for a free hash table entry */ 1045 if (dictp->codem1 < max_ent) { 1046 disp = (hval == 0) ? 1 : hval; 1047 do { 1048 hval += disp; 1049 if (hval >= db->hsize) 1050 hval -= db->hsize; 1051 dictp = &db->dict[hval]; 1052 } while (dictp->codem1 < max_ent); 1053 } 1054 1055 /* 1056 * Invalidate previous hash table entry 1057 * assigned this code, and then take it over 1058 */ 1059 dictp2 = &db->dict[max_ent+1]; 1060 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1061 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1062 } 1063 dictp2->cptr = hval; 1064 dictp->codem1 = max_ent; 1065 dictp->f.fcode = fcode; 1066 1067 db->max_ent = ++max_ent; 1068 db->lens[max_ent] = db->lens[oldcode]+1; 1069 1070 /* Expand code size if needed. */ 1071 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1072 db->n_bits = ++n_bits; 1073 tgtbitno = 32-n_bits; 1074 } 1075 } 1076 oldcode = incode; 1077 } 1078 dmp->m_len = wptr - mtod(dmp, u_char *); 1079 1080 /* 1081 * Keep the checkpoint right so that incompressible packets 1082 * clear the dictionary at the right times. 1083 */ 1084 db->bytes_out += ilen; 1085 db->in_count += explen; 1086 if (bsd_check(db) && db->debug) { 1087 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1088 db->unit); 1089 } 1090 1091 ++db->comp_count; 1092 db->comp_bytes += ilen + BSD_OVHD; 1093 ++db->uncomp_count; 1094 db->uncomp_bytes += explen; 1095 1096 *dmpp = mret; 1097 return DECOMP_OK; 1098 1099 #ifdef DEBUG 1100 bad: 1101 if (codelen <= 0) { 1102 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1103 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1104 incode, finchar, db->dict[finchar].cptr, max_ent); 1105 } else if (dictp->codem1 != finchar-1) { 1106 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1107 db->unit, incode, finchar); 1108 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1109 db->dict[finchar].cptr, dictp->codem1); 1110 } 1111 m_freem(mret); 1112 return DECOMP_FATALERROR; 1113 #endif /* DEBUG */ 1114 } 1115 #endif /* DO_BSD_COMPRESS */ 1116