1 /* $OpenBSD: bsd-comp.c,v 1.14 2017/06/19 17:58:49 bluhm 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/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 db = malloc(newlen, M_DEVBUF, M_NOWAIT|M_ZERO); 350 if (!db) 351 return NULL; 352 353 if (!decomp) { 354 db->lens = NULL; 355 } else { 356 db->lens = mallocarray(maxmaxcode + 1, sizeof(db->lens[0]), M_DEVBUF, 357 M_NOWAIT); 358 if (!db->lens) { 359 free(db, M_DEVBUF, newlen); 360 return NULL; 361 } 362 } 363 364 db->totlen = newlen; 365 db->hsize = hsize; 366 db->hshift = hshift; 367 db->maxmaxcode = maxmaxcode; 368 db->maxbits = bits; 369 370 return (void *) db; 371 } 372 373 static void 374 bsd_free(state) 375 void *state; 376 { 377 struct bsd_db *db = (struct bsd_db *) state; 378 379 if (db->lens) 380 free(db->lens, M_DEVBUF, (db->maxmaxcode + 1) * sizeof(db->lens[0])); 381 free(db, M_DEVBUF, db->totlen); 382 } 383 384 static void * 385 bsd_comp_alloc(options, opt_len) 386 u_char *options; 387 int opt_len; 388 { 389 return bsd_alloc(options, opt_len, 0); 390 } 391 392 static void * 393 bsd_decomp_alloc(options, opt_len) 394 u_char *options; 395 int opt_len; 396 { 397 return bsd_alloc(options, opt_len, 1); 398 } 399 400 /* 401 * Initialize the database. 402 */ 403 static int 404 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 405 struct bsd_db *db; 406 u_char *options; 407 int opt_len, unit, hdrlen, mru, debug, decomp; 408 { 409 int i; 410 411 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 412 || options[1] != CILEN_BSD_COMPRESS 413 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 414 || BSD_NBITS(options[2]) != db->maxbits 415 || (decomp && db->lens == NULL)) 416 return 0; 417 418 if (decomp) { 419 i = LAST+1; 420 while (i != 0) 421 db->lens[--i] = 1; 422 } 423 i = db->hsize; 424 while (i != 0) { 425 db->dict[--i].codem1 = BADCODEM1; 426 db->dict[i].cptr = 0; 427 } 428 429 db->unit = unit; 430 db->hdrlen = hdrlen; 431 db->mru = mru; 432 #ifndef DEBUG 433 if (debug) 434 #endif 435 db->debug = 1; 436 437 bsd_reset(db); 438 439 return 1; 440 } 441 442 static int 443 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 444 void *state; 445 u_char *options; 446 int opt_len, unit, hdrlen, debug; 447 { 448 return bsd_init((struct bsd_db *) state, options, opt_len, 449 unit, hdrlen, 0, debug, 0); 450 } 451 452 static int 453 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 454 void *state; 455 u_char *options; 456 int opt_len, unit, hdrlen, mru, debug; 457 { 458 return bsd_init((struct bsd_db *) state, options, opt_len, 459 unit, hdrlen, mru, debug, 1); 460 } 461 462 463 /* 464 * compress a packet 465 * One change from the BSD compress command is that when the 466 * code size expands, we do not output a bunch of padding. 467 */ 468 int /* new slen */ 469 bsd_compress(state, mret, mp, slen, maxolen) 470 void *state; 471 struct mbuf **mret; /* return compressed mbuf chain here */ 472 struct mbuf *mp; /* from here */ 473 int slen; /* uncompressed length */ 474 int maxolen; /* max compressed length */ 475 { 476 struct bsd_db *db = (struct bsd_db *) state; 477 int hshift = db->hshift; 478 u_int max_ent = db->max_ent; 479 u_int n_bits = db->n_bits; 480 u_int bitno = 32; 481 u_int32_t accm = 0, fcode; 482 struct bsd_dict *dictp; 483 u_char c; 484 int hval, disp, ent, ilen; 485 u_char *rptr, *wptr; 486 u_char *cp_end; 487 int olen; 488 struct mbuf *m; 489 490 #define PUTBYTE(v) { \ 491 ++olen; \ 492 if (wptr) { \ 493 *wptr++ = (v); \ 494 if (wptr >= cp_end) { \ 495 m->m_len = wptr - mtod(m, u_char *); \ 496 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 497 m = m->m_next; \ 498 if (m) { \ 499 m->m_len = 0; \ 500 if (maxolen - olen > MLEN) \ 501 MCLGET(m, M_DONTWAIT); \ 502 wptr = mtod(m, u_char *); \ 503 cp_end = wptr + M_TRAILINGSPACE(m); \ 504 } else \ 505 wptr = NULL; \ 506 } \ 507 } \ 508 } 509 510 #define OUTPUT(ent) { \ 511 bitno -= n_bits; \ 512 accm |= ((ent) << bitno); \ 513 do { \ 514 PUTBYTE(accm >> 24); \ 515 accm <<= 8; \ 516 bitno += 8; \ 517 } while (bitno <= 24); \ 518 } 519 520 /* 521 * If the protocol is not in the range we're interested in, 522 * just return without compressing the packet. If it is, 523 * the protocol becomes the first byte to compress. 524 */ 525 rptr = mtod(mp, u_char *); 526 ent = PPP_PROTOCOL(rptr); 527 if (ent < 0x21 || ent > 0xf9) { 528 *mret = NULL; 529 return slen; 530 } 531 532 /* Don't generate compressed packets which are larger than 533 the uncompressed packet. */ 534 if (maxolen > slen) 535 maxolen = slen; 536 537 /* Allocate one mbuf to start with. */ 538 MGET(m, M_DONTWAIT, MT_DATA); 539 *mret = m; 540 if (m != NULL) { 541 m->m_len = 0; 542 if (maxolen + db->hdrlen > MLEN) 543 MCLGET(m, M_DONTWAIT); 544 m->m_data += db->hdrlen; 545 wptr = mtod(m, u_char *); 546 cp_end = wptr + M_TRAILINGSPACE(m); 547 } else 548 wptr = cp_end = NULL; 549 550 /* 551 * Copy the PPP header over, changing the protocol, 552 * and install the 2-byte packet sequence number. 553 */ 554 if (wptr) { 555 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 556 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 557 *wptr++ = 0; /* change the protocol */ 558 *wptr++ = PPP_COMP; 559 *wptr++ = db->seqno >> 8; 560 *wptr++ = db->seqno; 561 } 562 ++db->seqno; 563 564 olen = 0; 565 rptr += PPP_HDRLEN; 566 slen = mp->m_len - PPP_HDRLEN; 567 ilen = slen + 1; 568 for (;;) { 569 if (slen <= 0) { 570 mp = mp->m_next; 571 if (!mp) 572 break; 573 rptr = mtod(mp, u_char *); 574 slen = mp->m_len; 575 if (!slen) 576 continue; /* handle 0-length buffers */ 577 ilen += slen; 578 } 579 580 slen--; 581 c = *rptr++; 582 fcode = BSD_KEY(ent, c); 583 hval = BSD_HASH(ent, c, hshift); 584 dictp = &db->dict[hval]; 585 586 /* Validate and then check the entry. */ 587 if (dictp->codem1 >= max_ent) 588 goto nomatch; 589 if (dictp->f.fcode == fcode) { 590 ent = dictp->codem1+1; 591 continue; /* found (prefix,suffix) */ 592 } 593 594 /* continue probing until a match or invalid entry */ 595 disp = (hval == 0) ? 1 : hval; 596 do { 597 hval += disp; 598 if (hval >= db->hsize) 599 hval -= db->hsize; 600 dictp = &db->dict[hval]; 601 if (dictp->codem1 >= max_ent) 602 goto nomatch; 603 } while (dictp->f.fcode != fcode); 604 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 605 continue; 606 607 nomatch: 608 OUTPUT(ent); /* output the prefix */ 609 610 /* code -> hashtable */ 611 if (max_ent < db->maxmaxcode) { 612 struct bsd_dict *dictp2; 613 /* expand code size if needed */ 614 if (max_ent >= MAXCODE(n_bits)) 615 db->n_bits = ++n_bits; 616 617 /* Invalidate old hash table entry using 618 * this code, and then take it over. 619 */ 620 dictp2 = &db->dict[max_ent+1]; 621 if (db->dict[dictp2->cptr].codem1 == max_ent) 622 db->dict[dictp2->cptr].codem1 = BADCODEM1; 623 dictp2->cptr = hval; 624 dictp->codem1 = max_ent; 625 dictp->f.fcode = fcode; 626 627 db->max_ent = ++max_ent; 628 } 629 ent = c; 630 } 631 632 OUTPUT(ent); /* output the last code */ 633 db->bytes_out += olen; 634 db->in_count += ilen; 635 if (bitno < 32) 636 ++db->bytes_out; /* count complete bytes */ 637 638 if (bsd_check(db)) 639 OUTPUT(CLEAR); /* do not count the CLEAR */ 640 641 /* 642 * Pad dribble bits of last code with ones. 643 * Do not emit a completely useless byte of ones. 644 */ 645 if (bitno != 32) 646 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 647 648 if (m != NULL) { 649 m->m_len = wptr - mtod(m, u_char *); 650 m->m_next = NULL; 651 } 652 653 /* 654 * Increase code size if we would have without the packet 655 * boundary and as the decompressor will. 656 */ 657 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 658 db->n_bits++; 659 660 db->uncomp_bytes += ilen; 661 ++db->uncomp_count; 662 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 663 /* throw away the compressed stuff if it is longer than uncompressed */ 664 m_freemp(mret); 665 666 ++db->incomp_count; 667 db->incomp_bytes += ilen; 668 } else { 669 ++db->comp_count; 670 db->comp_bytes += olen + BSD_OVHD; 671 } 672 673 return olen + PPP_HDRLEN + BSD_OVHD; 674 #undef OUTPUT 675 #undef PUTBYTE 676 } 677 678 679 /* 680 * Update the "BSD Compress" dictionary on the receiver for 681 * incompressible data by pretending to compress the incoming data. 682 */ 683 static void 684 bsd_incomp(state, dmsg) 685 void *state; 686 struct mbuf *dmsg; 687 { 688 struct bsd_db *db = (struct bsd_db *) state; 689 u_int hshift = db->hshift; 690 u_int max_ent = db->max_ent; 691 u_int n_bits = db->n_bits; 692 struct bsd_dict *dictp; 693 u_int32_t fcode; 694 u_char c; 695 u_int32_t hval, disp; 696 int slen, ilen; 697 u_int bitno = 7; 698 u_char *rptr; 699 u_int ent; 700 701 /* 702 * If the protocol is not in the range we're interested in, 703 * just return without looking at the packet. If it is, 704 * the protocol becomes the first byte to "compress". 705 */ 706 rptr = mtod(dmsg, u_char *); 707 ent = PPP_PROTOCOL(rptr); 708 if (ent < 0x21 || ent > 0xf9) 709 return; 710 711 db->incomp_count++; 712 db->seqno++; 713 ilen = 1; /* count the protocol as 1 byte */ 714 rptr += PPP_HDRLEN; 715 slen = dmsg->m_len - PPP_HDRLEN; 716 for (;;) { 717 if (slen <= 0) { 718 dmsg = dmsg->m_next; 719 if (!dmsg) 720 break; 721 rptr = mtod(dmsg, u_char *); 722 slen = dmsg->m_len; 723 continue; 724 } 725 ilen += slen; 726 727 do { 728 c = *rptr++; 729 fcode = BSD_KEY(ent, c); 730 hval = BSD_HASH(ent, c, hshift); 731 dictp = &db->dict[hval]; 732 733 /* validate and then check the entry */ 734 if (dictp->codem1 >= max_ent) 735 goto nomatch; 736 if (dictp->f.fcode == fcode) { 737 ent = dictp->codem1+1; 738 continue; /* found (prefix,suffix) */ 739 } 740 741 /* continue probing until a match or invalid entry */ 742 disp = (hval == 0) ? 1 : hval; 743 do { 744 hval += disp; 745 if (hval >= db->hsize) 746 hval -= db->hsize; 747 dictp = &db->dict[hval]; 748 if (dictp->codem1 >= max_ent) 749 goto nomatch; 750 } while (dictp->f.fcode != fcode); 751 ent = dictp->codem1+1; 752 continue; /* finally found (prefix,suffix) */ 753 754 nomatch: /* output (count) the prefix */ 755 bitno += n_bits; 756 757 /* code -> hashtable */ 758 if (max_ent < db->maxmaxcode) { 759 struct bsd_dict *dictp2; 760 /* expand code size if needed */ 761 if (max_ent >= MAXCODE(n_bits)) 762 db->n_bits = ++n_bits; 763 764 /* Invalidate previous hash table entry 765 * assigned this code, and then take it over. 766 */ 767 dictp2 = &db->dict[max_ent+1]; 768 if (db->dict[dictp2->cptr].codem1 == max_ent) 769 db->dict[dictp2->cptr].codem1 = BADCODEM1; 770 dictp2->cptr = hval; 771 dictp->codem1 = max_ent; 772 dictp->f.fcode = fcode; 773 774 db->max_ent = ++max_ent; 775 db->lens[max_ent] = db->lens[ent]+1; 776 } 777 ent = c; 778 } while (--slen != 0); 779 } 780 bitno += n_bits; /* output (count) the last code */ 781 db->bytes_out += bitno/8; 782 db->in_count += ilen; 783 (void)bsd_check(db); 784 785 ++db->incomp_count; 786 db->incomp_bytes += ilen; 787 ++db->uncomp_count; 788 db->uncomp_bytes += ilen; 789 790 /* Increase code size if we would have without the packet 791 * boundary and as the decompressor will. 792 */ 793 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 794 db->n_bits++; 795 } 796 797 798 /* 799 * Decompress "BSD Compress". 800 * 801 * Because of patent problems, we return DECOMP_ERROR for errors 802 * found by inspecting the input data and for system problems, but 803 * DECOMP_FATALERROR for any errors which could possibly be said to 804 * be being detected "after" decompression. For DECOMP_ERROR, 805 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 806 * infringing a patent of Motorola's if we do, so we take CCP down 807 * instead. 808 * 809 * Given that the frame has the correct sequence number and a good FCS, 810 * errors such as invalid codes in the input most likely indicate a 811 * bug, so we return DECOMP_FATALERROR for them in order to turn off 812 * compression, even though they are detected by inspecting the input. 813 */ 814 int 815 bsd_decompress(state, cmp, dmpp) 816 void *state; 817 struct mbuf *cmp, **dmpp; 818 { 819 struct bsd_db *db = (struct bsd_db *) state; 820 u_int max_ent = db->max_ent; 821 u_int32_t accm = 0; 822 u_int bitno = 32; /* 1st valid bit in accm */ 823 u_int n_bits = db->n_bits; 824 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 825 struct bsd_dict *dictp; 826 int explen, i, seq, len; 827 u_int incode, oldcode, finchar; 828 u_char *p, *rptr, *wptr; 829 struct mbuf *m, *dmp, *mret; 830 int adrs, ctrl, ilen; 831 int space, codelen, extra; 832 833 /* 834 * Save the address/control from the PPP header 835 * and then get the sequence number. 836 */ 837 *dmpp = NULL; 838 rptr = mtod(cmp, u_char *); 839 adrs = PPP_ADDRESS(rptr); 840 ctrl = PPP_CONTROL(rptr); 841 rptr += PPP_HDRLEN; 842 len = cmp->m_len - PPP_HDRLEN; 843 seq = 0; 844 for (i = 0; i < 2; ++i) { 845 while (len <= 0) { 846 cmp = cmp->m_next; 847 if (cmp == NULL) 848 return DECOMP_ERROR; 849 rptr = mtod(cmp, u_char *); 850 len = cmp->m_len; 851 } 852 seq = (seq << 8) + *rptr++; 853 --len; 854 } 855 856 /* 857 * Check the sequence number and give up if it differs from 858 * the value we're expecting. 859 */ 860 if (seq != db->seqno) { 861 if (db->debug) 862 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 863 db->unit, seq, db->seqno - 1); 864 return DECOMP_ERROR; 865 } 866 ++db->seqno; 867 868 /* 869 * Allocate one mbuf to start with. 870 */ 871 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 872 if (dmp == NULL) 873 return DECOMP_ERROR; 874 mret = dmp; 875 dmp->m_len = 0; 876 dmp->m_next = NULL; 877 MCLGET(dmp, M_DONTWAIT); 878 dmp->m_data += db->hdrlen; 879 wptr = mtod(dmp, u_char *); 880 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 881 882 /* 883 * Fill in the ppp header, but not the last byte of the protocol 884 * (that comes from the decompressed data). 885 */ 886 wptr[0] = adrs; 887 wptr[1] = ctrl; 888 wptr[2] = 0; 889 wptr += PPP_HDRLEN - 1; 890 891 ilen = len; 892 oldcode = CLEAR; 893 explen = 0; 894 for (;;) { 895 if (len == 0) { 896 cmp = cmp->m_next; 897 if (!cmp) /* quit at end of message */ 898 break; 899 rptr = mtod(cmp, u_char *); 900 len = cmp->m_len; 901 ilen += len; 902 continue; /* handle 0-length buffers */ 903 } 904 905 /* 906 * Accumulate bytes until we have a complete code. 907 * Then get the next code, relying on the 32-bit, 908 * unsigned accm to mask the result. 909 */ 910 bitno -= 8; 911 accm |= *rptr++ << bitno; 912 --len; 913 if (tgtbitno < bitno) 914 continue; 915 incode = accm >> tgtbitno; 916 accm <<= n_bits; 917 bitno += n_bits; 918 919 if (incode == CLEAR) { 920 /* 921 * The dictionary must only be cleared at 922 * the end of a packet. But there could be an 923 * empty mbuf at the end. 924 */ 925 if (len > 0 || cmp->m_next != NULL) { 926 while ((cmp = cmp->m_next) != NULL) 927 len += cmp->m_len; 928 if (len > 0) { 929 m_freem(mret); 930 if (db->debug) 931 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 932 return DECOMP_FATALERROR; /* probably a bug */ 933 } 934 } 935 bsd_clear(db); 936 explen = ilen = 0; 937 break; 938 } 939 940 if (incode > max_ent + 2 || incode > db->maxmaxcode 941 || (incode > max_ent && oldcode == CLEAR)) { 942 m_freem(mret); 943 if (db->debug) { 944 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 945 db->unit, incode, oldcode); 946 printf("max_ent=0x%x explen=%d seqno=%d\n", 947 max_ent, explen, db->seqno); 948 } 949 return DECOMP_FATALERROR; /* probably a bug */ 950 } 951 952 /* Special case for KwKwK string. */ 953 if (incode > max_ent) { 954 finchar = oldcode; 955 extra = 1; 956 } else { 957 finchar = incode; 958 extra = 0; 959 } 960 961 codelen = db->lens[finchar]; 962 explen += codelen + extra; 963 if (explen > db->mru + 1) { 964 m_freem(mret); 965 if (db->debug) { 966 printf("bsd_decomp%d: ran out of mru\n", db->unit); 967 #ifdef DEBUG 968 while ((cmp = cmp->m_next) != NULL) 969 len += cmp->m_len; 970 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 971 len, finchar, codelen, explen); 972 #endif 973 } 974 return DECOMP_FATALERROR; 975 } 976 977 /* 978 * For simplicity, the decoded characters go in a single mbuf, 979 * so we allocate a single extra cluster mbuf if necessary. 980 */ 981 if ((space -= codelen + extra) < 0) { 982 dmp->m_len = wptr - mtod(dmp, u_char *); 983 MGET(m, M_DONTWAIT, MT_DATA); 984 if (m == NULL) { 985 m_freem(mret); 986 return DECOMP_ERROR; 987 } 988 m->m_len = 0; 989 m->m_next = NULL; 990 dmp->m_next = m; 991 MCLGET(m, M_DONTWAIT); 992 space = M_TRAILINGSPACE(m) - (codelen + extra); 993 if (space < 0) { 994 /* now that's what I call *compression*. */ 995 m_freem(mret); 996 return DECOMP_ERROR; 997 } 998 dmp = m; 999 wptr = mtod(dmp, u_char *); 1000 } 1001 1002 /* 1003 * Decode this code and install it in the decompressed buffer. 1004 */ 1005 p = (wptr += codelen); 1006 while (finchar > LAST) { 1007 dictp = &db->dict[db->dict[finchar].cptr]; 1008 #ifdef DEBUG 1009 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1010 goto bad; 1011 #endif 1012 *--p = dictp->f.hs.suffix; 1013 finchar = dictp->f.hs.prefix; 1014 } 1015 *--p = finchar; 1016 1017 #ifdef DEBUG 1018 if (--codelen != 0) 1019 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1020 db->unit, codelen, incode, max_ent); 1021 #endif 1022 1023 if (extra) /* the KwKwK case again */ 1024 *wptr++ = finchar; 1025 1026 /* 1027 * If not first code in a packet, and 1028 * if not out of code space, then allocate a new code. 1029 * 1030 * Keep the hash table correct so it can be used 1031 * with uncompressed packets. 1032 */ 1033 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1034 struct bsd_dict *dictp2; 1035 u_int32_t fcode; 1036 u_int32_t hval, disp; 1037 1038 fcode = BSD_KEY(oldcode,finchar); 1039 hval = BSD_HASH(oldcode,finchar,db->hshift); 1040 dictp = &db->dict[hval]; 1041 1042 /* look for a free hash table entry */ 1043 if (dictp->codem1 < max_ent) { 1044 disp = (hval == 0) ? 1 : hval; 1045 do { 1046 hval += disp; 1047 if (hval >= db->hsize) 1048 hval -= db->hsize; 1049 dictp = &db->dict[hval]; 1050 } while (dictp->codem1 < max_ent); 1051 } 1052 1053 /* 1054 * Invalidate previous hash table entry 1055 * assigned this code, and then take it over 1056 */ 1057 dictp2 = &db->dict[max_ent+1]; 1058 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1059 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1060 } 1061 dictp2->cptr = hval; 1062 dictp->codem1 = max_ent; 1063 dictp->f.fcode = fcode; 1064 1065 db->max_ent = ++max_ent; 1066 db->lens[max_ent] = db->lens[oldcode]+1; 1067 1068 /* Expand code size if needed. */ 1069 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1070 db->n_bits = ++n_bits; 1071 tgtbitno = 32-n_bits; 1072 } 1073 } 1074 oldcode = incode; 1075 } 1076 dmp->m_len = wptr - mtod(dmp, u_char *); 1077 1078 /* 1079 * Keep the checkpoint right so that incompressible packets 1080 * clear the dictionary at the right times. 1081 */ 1082 db->bytes_out += ilen; 1083 db->in_count += explen; 1084 if (bsd_check(db) && db->debug) { 1085 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1086 db->unit); 1087 } 1088 1089 ++db->comp_count; 1090 db->comp_bytes += ilen + BSD_OVHD; 1091 ++db->uncomp_count; 1092 db->uncomp_bytes += explen; 1093 1094 *dmpp = mret; 1095 return DECOMP_OK; 1096 1097 #ifdef DEBUG 1098 bad: 1099 if (codelen <= 0) { 1100 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1101 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1102 incode, finchar, db->dict[finchar].cptr, max_ent); 1103 } else if (dictp->codem1 != finchar-1) { 1104 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1105 db->unit, incode, finchar); 1106 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1107 db->dict[finchar].cptr, dictp->codem1); 1108 } 1109 m_freem(mret); 1110 return DECOMP_FATALERROR; 1111 #endif /* DEBUG */ 1112 } 1113 #endif /* DO_BSD_COMPRESS */ 1114