1 /* $OpenBSD: bsd-comp.c,v 1.16 2018/11/09 14:14:31 claudio 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/systm.h> 45 #include <sys/mbuf.h> 46 #include <sys/socket.h> 47 #include <net/if.h> 48 #include <net/if_var.h> 49 #include <net/ppp_defs.h> 50 #include <net/if_ppp.h> 51 52 #define PACKETPTR struct mbuf * 53 #include <net/ppp-comp.h> 54 55 #if DO_BSD_COMPRESS 56 /* 57 * PPP "BSD compress" compression 58 * The differences between this compression and the classic BSD LZW 59 * source are obvious from the requirement that the classic code worked 60 * with files while this handles arbitrarily long streams that 61 * are broken into packets. They are: 62 * 63 * When the code size expands, a block of junk is not emitted by 64 * the compressor and not expected by the decompressor. 65 * 66 * New codes are not necessarily assigned every time an old 67 * code is output by the compressor. This is because a packet 68 * end forces a code to be emitted, but does not imply that a 69 * new sequence has been seen. 70 * 71 * The compression ratio is checked at the first end of a packet 72 * after the appropriate gap. Besides simplifying and speeding 73 * things up, this makes it more likely that the transmitter 74 * and receiver will agree when the dictionary is cleared when 75 * compression is not going well. 76 */ 77 78 /* 79 * A dictionary for doing BSD compress. 80 */ 81 struct bsd_db { 82 int totlen; /* length of this structure */ 83 u_int hsize; /* size of the hash table */ 84 u_char hshift; /* used in hash function */ 85 u_char n_bits; /* current bits/code */ 86 u_char maxbits; 87 u_char debug; 88 u_char unit; 89 u_int16_t seqno; /* sequence # of next packet */ 90 u_int hdrlen; /* header length to preallocate */ 91 u_int mru; 92 u_int maxmaxcode; /* largest valid code */ 93 u_int max_ent; /* largest code in use */ 94 u_int in_count; /* uncompressed bytes, aged */ 95 u_int bytes_out; /* compressed bytes, aged */ 96 u_int ratio; /* recent compression ratio */ 97 u_int checkpoint; /* when to next check the ratio */ 98 u_int clear_count; /* times dictionary cleared */ 99 u_int incomp_count; /* incompressible packets */ 100 u_int incomp_bytes; /* incompressible bytes */ 101 u_int uncomp_count; /* uncompressed packets */ 102 u_int uncomp_bytes; /* uncompressed bytes */ 103 u_int comp_count; /* compressed packets */ 104 u_int comp_bytes; /* compressed bytes */ 105 u_int16_t *lens; /* array of lengths of codes */ 106 struct bsd_dict { 107 union { /* hash value */ 108 u_int32_t fcode; 109 struct { 110 #if BYTE_ORDER == LITTLE_ENDIAN 111 u_int16_t prefix; /* preceding code */ 112 u_char suffix; /* last character of new code */ 113 u_char pad; 114 #else 115 u_char pad; 116 u_char suffix; /* last character of new code */ 117 u_int16_t prefix; /* preceding code */ 118 #endif 119 } hs; 120 } f; 121 u_int16_t codem1; /* output of hash table -1 */ 122 u_int16_t cptr; /* map code to hash table entry */ 123 } dict[1]; 124 }; 125 126 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 127 #define BSD_INIT_BITS BSD_MIN_BITS 128 129 static void *bsd_comp_alloc(u_char *options, int opt_len); 130 static void *bsd_decomp_alloc(u_char *options, int opt_len); 131 static void bsd_free(void *state); 132 static int bsd_comp_init(void *state, u_char *options, int opt_len, 133 int unit, int hdrlen, int debug); 134 static int bsd_decomp_init(void *state, u_char *options, int opt_len, 135 int unit, int hdrlen, int mru, int debug); 136 static int bsd_compress(void *state, struct mbuf **mret, 137 struct mbuf *mp, int slen, int maxolen); 138 static void bsd_incomp(void *state, struct mbuf *dmsg); 139 static int bsd_decompress(void *state, struct mbuf *cmp, 140 struct mbuf **dmpp); 141 static void bsd_reset(void *state); 142 static void bsd_comp_stats(void *state, struct compstat *stats); 143 144 /* 145 * Procedures exported to if_ppp.c. 146 */ 147 struct compressor ppp_bsd_compress = { 148 CI_BSD_COMPRESS, /* compress_proto */ 149 bsd_comp_alloc, /* comp_alloc */ 150 bsd_free, /* comp_free */ 151 bsd_comp_init, /* comp_init */ 152 bsd_reset, /* comp_reset */ 153 bsd_compress, /* compress */ 154 bsd_comp_stats, /* comp_stat */ 155 bsd_decomp_alloc, /* decomp_alloc */ 156 bsd_free, /* decomp_free */ 157 bsd_decomp_init, /* decomp_init */ 158 bsd_reset, /* decomp_reset */ 159 bsd_decompress, /* decompress */ 160 bsd_incomp, /* incomp */ 161 bsd_comp_stats, /* decomp_stat */ 162 }; 163 164 /* 165 * the next two codes should not be changed lightly, as they must not 166 * lie within the contiguous general code space. 167 */ 168 #define CLEAR 256 /* table clear output code */ 169 #define FIRST 257 /* first free entry */ 170 #define LAST 255 171 172 #define MAXCODE(b) ((1 << (b)) - 1) 173 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 174 175 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 176 ^ (u_int32_t)(prefix)) 177 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 178 + (u_int32_t)(prefix)) 179 180 #define CHECK_GAP 10000 /* Ratio check interval */ 181 182 #define RATIO_SCALE_LOG 8 183 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 184 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 185 186 static void bsd_clear(struct bsd_db *); 187 static int bsd_check(struct bsd_db *); 188 static void *bsd_alloc(u_char *, int, int); 189 static int bsd_init(struct bsd_db *, u_char *, int, int, int, int, 190 int, int); 191 192 /* 193 * clear the dictionary 194 */ 195 static void 196 bsd_clear(db) 197 struct bsd_db *db; 198 { 199 db->clear_count++; 200 db->max_ent = FIRST-1; 201 db->n_bits = BSD_INIT_BITS; 202 db->ratio = 0; 203 db->bytes_out = 0; 204 db->in_count = 0; 205 db->incomp_count = 0; 206 db->checkpoint = CHECK_GAP; 207 } 208 209 /* 210 * If the dictionary is full, then see if it is time to reset it. 211 * 212 * Compute the compression ratio using fixed-point arithmetic 213 * with 8 fractional bits. 214 * 215 * Since we have an infinite stream instead of a single file, 216 * watch only the local compression ratio. 217 * 218 * Since both peers must reset the dictionary at the same time even in 219 * the absence of CLEAR codes (while packets are incompressible), they 220 * must compute the same ratio. 221 */ 222 static int /* 1=output CLEAR */ 223 bsd_check(db) 224 struct bsd_db *db; 225 { 226 u_int new_ratio; 227 228 if (db->in_count >= db->checkpoint) { 229 /* age the ratio by limiting the size of the counts */ 230 if (db->in_count >= RATIO_MAX 231 || db->bytes_out >= RATIO_MAX) { 232 db->in_count -= db->in_count/4; 233 db->bytes_out -= db->bytes_out/4; 234 } 235 236 db->checkpoint = db->in_count + CHECK_GAP; 237 238 if (db->max_ent >= db->maxmaxcode) { 239 /* Reset the dictionary only if the ratio is worse, 240 * or if it looks as if it has been poisoned 241 * by incompressible data. 242 * 243 * This does not overflow, because 244 * db->in_count <= RATIO_MAX. 245 */ 246 new_ratio = db->in_count << RATIO_SCALE_LOG; 247 if (db->bytes_out != 0) 248 new_ratio /= db->bytes_out; 249 250 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 251 bsd_clear(db); 252 return 1; 253 } 254 db->ratio = new_ratio; 255 } 256 } 257 return 0; 258 } 259 260 /* 261 * Return statistics. 262 */ 263 static void 264 bsd_comp_stats(state, stats) 265 void *state; 266 struct compstat *stats; 267 { 268 struct bsd_db *db = (struct bsd_db *) state; 269 u_int out; 270 271 stats->unc_bytes = db->uncomp_bytes; 272 stats->unc_packets = db->uncomp_count; 273 stats->comp_bytes = db->comp_bytes; 274 stats->comp_packets = db->comp_count; 275 stats->inc_bytes = db->incomp_bytes; 276 stats->inc_packets = db->incomp_count; 277 stats->ratio = db->in_count; 278 out = db->bytes_out; 279 if (stats->ratio <= 0x7fffff) 280 stats->ratio <<= 8; 281 else 282 out >>= 8; 283 if (out != 0) 284 stats->ratio /= out; 285 } 286 287 /* 288 * Reset state, as on a CCP ResetReq. 289 */ 290 static void 291 bsd_reset(state) 292 void *state; 293 { 294 struct bsd_db *db = (struct bsd_db *) state; 295 296 db->seqno = 0; 297 bsd_clear(db); 298 db->clear_count = 0; 299 } 300 301 /* 302 * Allocate space for a (de) compressor. 303 */ 304 static void * 305 bsd_alloc(options, opt_len, decomp) 306 u_char *options; 307 int opt_len, decomp; 308 { 309 int bits; 310 u_int newlen, hsize, hshift, maxmaxcode; 311 struct bsd_db *db; 312 313 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 314 || options[1] != CILEN_BSD_COMPRESS 315 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 316 return NULL; 317 bits = BSD_NBITS(options[2]); 318 switch (bits) { 319 case 9: /* needs 82152 for both directions */ 320 case 10: /* needs 84144 */ 321 case 11: /* needs 88240 */ 322 case 12: /* needs 96432 */ 323 hsize = 5003; 324 hshift = 4; 325 break; 326 case 13: /* needs 176784 */ 327 hsize = 9001; 328 hshift = 5; 329 break; 330 case 14: /* needs 353744 */ 331 hsize = 18013; 332 hshift = 6; 333 break; 334 case 15: /* needs 691440 */ 335 hsize = 35023; 336 hshift = 7; 337 break; 338 case 16: /* needs 1366160--far too much, */ 339 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 340 /* hshift = 8; */ /* in struct bsd_db */ 341 /* break; */ 342 default: 343 return NULL; 344 } 345 346 maxmaxcode = MAXCODE(bits); 347 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 348 db = malloc(newlen, M_DEVBUF, M_NOWAIT|M_ZERO); 349 if (!db) 350 return NULL; 351 352 if (!decomp) { 353 db->lens = NULL; 354 } else { 355 db->lens = mallocarray(maxmaxcode + 1, sizeof(db->lens[0]), M_DEVBUF, 356 M_NOWAIT); 357 if (!db->lens) { 358 free(db, M_DEVBUF, newlen); 359 return NULL; 360 } 361 } 362 363 db->totlen = newlen; 364 db->hsize = hsize; 365 db->hshift = hshift; 366 db->maxmaxcode = maxmaxcode; 367 db->maxbits = bits; 368 369 return (void *) db; 370 } 371 372 static void 373 bsd_free(state) 374 void *state; 375 { 376 struct bsd_db *db = (struct bsd_db *) state; 377 378 if (db->lens) 379 free(db->lens, M_DEVBUF, (db->maxmaxcode + 1) * sizeof(db->lens[0])); 380 free(db, M_DEVBUF, db->totlen); 381 } 382 383 static void * 384 bsd_comp_alloc(options, opt_len) 385 u_char *options; 386 int opt_len; 387 { 388 return bsd_alloc(options, opt_len, 0); 389 } 390 391 static void * 392 bsd_decomp_alloc(options, opt_len) 393 u_char *options; 394 int opt_len; 395 { 396 return bsd_alloc(options, opt_len, 1); 397 } 398 399 /* 400 * Initialize the database. 401 */ 402 static int 403 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 404 struct bsd_db *db; 405 u_char *options; 406 int opt_len, unit, hdrlen, mru, debug, decomp; 407 { 408 int i; 409 410 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 411 || options[1] != CILEN_BSD_COMPRESS 412 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 413 || BSD_NBITS(options[2]) != db->maxbits 414 || (decomp && db->lens == NULL)) 415 return 0; 416 417 if (decomp) { 418 i = LAST+1; 419 while (i != 0) 420 db->lens[--i] = 1; 421 } 422 i = db->hsize; 423 while (i != 0) { 424 db->dict[--i].codem1 = BADCODEM1; 425 db->dict[i].cptr = 0; 426 } 427 428 db->unit = unit; 429 db->hdrlen = hdrlen; 430 db->mru = mru; 431 #ifndef DEBUG 432 if (debug) 433 #endif 434 db->debug = 1; 435 436 bsd_reset(db); 437 438 return 1; 439 } 440 441 static int 442 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 443 void *state; 444 u_char *options; 445 int opt_len, unit, hdrlen, debug; 446 { 447 return bsd_init((struct bsd_db *) state, options, opt_len, 448 unit, hdrlen, 0, debug, 0); 449 } 450 451 static int 452 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 453 void *state; 454 u_char *options; 455 int opt_len, unit, hdrlen, mru, debug; 456 { 457 return bsd_init((struct bsd_db *) state, options, opt_len, 458 unit, hdrlen, mru, debug, 1); 459 } 460 461 462 /* 463 * compress a packet 464 * One change from the BSD compress command is that when the 465 * code size expands, we do not output a bunch of padding. 466 */ 467 int /* new slen */ 468 bsd_compress(state, mret, mp, slen, maxolen) 469 void *state; 470 struct mbuf **mret; /* return compressed mbuf chain here */ 471 struct mbuf *mp; /* from here */ 472 int slen; /* uncompressed length */ 473 int maxolen; /* max compressed length */ 474 { 475 struct bsd_db *db = (struct bsd_db *) state; 476 int hshift = db->hshift; 477 u_int max_ent = db->max_ent; 478 u_int n_bits = db->n_bits; 479 u_int bitno = 32; 480 u_int32_t accm = 0, fcode; 481 struct bsd_dict *dictp; 482 u_char c; 483 int hval, disp, ent, ilen; 484 u_char *rptr, *wptr; 485 u_char *cp_end; 486 int olen; 487 struct mbuf *m; 488 489 #define PUTBYTE(v) { \ 490 ++olen; \ 491 if (wptr) { \ 492 *wptr++ = (v); \ 493 if (wptr >= cp_end) { \ 494 m->m_len = wptr - mtod(m, u_char *); \ 495 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 496 m = m->m_next; \ 497 if (m) { \ 498 m->m_len = 0; \ 499 if (maxolen - olen > MLEN) \ 500 MCLGET(m, M_DONTWAIT); \ 501 wptr = mtod(m, u_char *); \ 502 cp_end = wptr + m_trailingspace(m); \ 503 } else \ 504 wptr = NULL; \ 505 } \ 506 } \ 507 } 508 509 #define OUTPUT(ent) { \ 510 bitno -= n_bits; \ 511 accm |= ((ent) << bitno); \ 512 do { \ 513 PUTBYTE(accm >> 24); \ 514 accm <<= 8; \ 515 bitno += 8; \ 516 } while (bitno <= 24); \ 517 } 518 519 /* 520 * If the protocol is not in the range we're interested in, 521 * just return without compressing the packet. If it is, 522 * the protocol becomes the first byte to compress. 523 */ 524 rptr = mtod(mp, u_char *); 525 ent = PPP_PROTOCOL(rptr); 526 if (ent < 0x21 || ent > 0xf9) { 527 *mret = NULL; 528 return slen; 529 } 530 531 /* Don't generate compressed packets which are larger than 532 the uncompressed packet. */ 533 if (maxolen > slen) 534 maxolen = slen; 535 536 /* Allocate one mbuf to start with. */ 537 MGET(m, M_DONTWAIT, MT_DATA); 538 *mret = m; 539 if (m != NULL) { 540 m->m_len = 0; 541 if (maxolen + db->hdrlen > MLEN) 542 MCLGET(m, M_DONTWAIT); 543 m->m_data += db->hdrlen; 544 wptr = mtod(m, u_char *); 545 cp_end = wptr + m_trailingspace(m); 546 } else 547 wptr = cp_end = NULL; 548 549 /* 550 * Copy the PPP header over, changing the protocol, 551 * and install the 2-byte packet sequence number. 552 */ 553 if (wptr) { 554 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 555 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 556 *wptr++ = 0; /* change the protocol */ 557 *wptr++ = PPP_COMP; 558 *wptr++ = db->seqno >> 8; 559 *wptr++ = db->seqno; 560 } 561 ++db->seqno; 562 563 olen = 0; 564 rptr += PPP_HDRLEN; 565 slen = mp->m_len - PPP_HDRLEN; 566 ilen = slen + 1; 567 for (;;) { 568 if (slen <= 0) { 569 mp = mp->m_next; 570 if (!mp) 571 break; 572 rptr = mtod(mp, u_char *); 573 slen = mp->m_len; 574 if (!slen) 575 continue; /* handle 0-length buffers */ 576 ilen += slen; 577 } 578 579 slen--; 580 c = *rptr++; 581 fcode = BSD_KEY(ent, c); 582 hval = BSD_HASH(ent, c, hshift); 583 dictp = &db->dict[hval]; 584 585 /* Validate and then check the entry. */ 586 if (dictp->codem1 >= max_ent) 587 goto nomatch; 588 if (dictp->f.fcode == fcode) { 589 ent = dictp->codem1+1; 590 continue; /* found (prefix,suffix) */ 591 } 592 593 /* continue probing until a match or invalid entry */ 594 disp = (hval == 0) ? 1 : hval; 595 do { 596 hval += disp; 597 if (hval >= db->hsize) 598 hval -= db->hsize; 599 dictp = &db->dict[hval]; 600 if (dictp->codem1 >= max_ent) 601 goto nomatch; 602 } while (dictp->f.fcode != fcode); 603 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 604 continue; 605 606 nomatch: 607 OUTPUT(ent); /* output the prefix */ 608 609 /* code -> hashtable */ 610 if (max_ent < db->maxmaxcode) { 611 struct bsd_dict *dictp2; 612 /* expand code size if needed */ 613 if (max_ent >= MAXCODE(n_bits)) 614 db->n_bits = ++n_bits; 615 616 /* Invalidate old hash table entry using 617 * this code, and then take it over. 618 */ 619 dictp2 = &db->dict[max_ent+1]; 620 if (db->dict[dictp2->cptr].codem1 == max_ent) 621 db->dict[dictp2->cptr].codem1 = BADCODEM1; 622 dictp2->cptr = hval; 623 dictp->codem1 = max_ent; 624 dictp->f.fcode = fcode; 625 626 db->max_ent = ++max_ent; 627 } 628 ent = c; 629 } 630 631 OUTPUT(ent); /* output the last code */ 632 db->bytes_out += olen; 633 db->in_count += ilen; 634 if (bitno < 32) 635 ++db->bytes_out; /* count complete bytes */ 636 637 if (bsd_check(db)) 638 OUTPUT(CLEAR); /* do not count the CLEAR */ 639 640 /* 641 * Pad dribble bits of last code with ones. 642 * Do not emit a completely useless byte of ones. 643 */ 644 if (bitno != 32) 645 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 646 647 if (m != NULL) { 648 m->m_len = wptr - mtod(m, u_char *); 649 m->m_next = NULL; 650 } 651 652 /* 653 * Increase code size if we would have without the packet 654 * boundary and as the decompressor will. 655 */ 656 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 657 db->n_bits++; 658 659 db->uncomp_bytes += ilen; 660 ++db->uncomp_count; 661 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 662 /* throw away the compressed stuff if it is longer than uncompressed */ 663 m_freemp(mret); 664 665 ++db->incomp_count; 666 db->incomp_bytes += ilen; 667 } else { 668 ++db->comp_count; 669 db->comp_bytes += olen + BSD_OVHD; 670 } 671 672 return olen + PPP_HDRLEN + BSD_OVHD; 673 #undef OUTPUT 674 #undef PUTBYTE 675 } 676 677 678 /* 679 * Update the "BSD Compress" dictionary on the receiver for 680 * incompressible data by pretending to compress the incoming data. 681 */ 682 static void 683 bsd_incomp(state, dmsg) 684 void *state; 685 struct mbuf *dmsg; 686 { 687 struct bsd_db *db = (struct bsd_db *) state; 688 u_int hshift = db->hshift; 689 u_int max_ent = db->max_ent; 690 u_int n_bits = db->n_bits; 691 struct bsd_dict *dictp; 692 u_int32_t fcode; 693 u_char c; 694 u_int32_t hval, disp; 695 int slen, ilen; 696 u_int bitno = 7; 697 u_char *rptr; 698 u_int ent; 699 700 /* 701 * If the protocol is not in the range we're interested in, 702 * just return without looking at the packet. If it is, 703 * the protocol becomes the first byte to "compress". 704 */ 705 rptr = mtod(dmsg, u_char *); 706 ent = PPP_PROTOCOL(rptr); 707 if (ent < 0x21 || ent > 0xf9) 708 return; 709 710 db->incomp_count++; 711 db->seqno++; 712 ilen = 1; /* count the protocol as 1 byte */ 713 rptr += PPP_HDRLEN; 714 slen = dmsg->m_len - PPP_HDRLEN; 715 for (;;) { 716 if (slen <= 0) { 717 dmsg = dmsg->m_next; 718 if (!dmsg) 719 break; 720 rptr = mtod(dmsg, u_char *); 721 slen = dmsg->m_len; 722 continue; 723 } 724 ilen += slen; 725 726 do { 727 c = *rptr++; 728 fcode = BSD_KEY(ent, c); 729 hval = BSD_HASH(ent, c, hshift); 730 dictp = &db->dict[hval]; 731 732 /* validate and then check the entry */ 733 if (dictp->codem1 >= max_ent) 734 goto nomatch; 735 if (dictp->f.fcode == fcode) { 736 ent = dictp->codem1+1; 737 continue; /* found (prefix,suffix) */ 738 } 739 740 /* continue probing until a match or invalid entry */ 741 disp = (hval == 0) ? 1 : hval; 742 do { 743 hval += disp; 744 if (hval >= db->hsize) 745 hval -= db->hsize; 746 dictp = &db->dict[hval]; 747 if (dictp->codem1 >= max_ent) 748 goto nomatch; 749 } while (dictp->f.fcode != fcode); 750 ent = dictp->codem1+1; 751 continue; /* finally found (prefix,suffix) */ 752 753 nomatch: /* output (count) the prefix */ 754 bitno += n_bits; 755 756 /* code -> hashtable */ 757 if (max_ent < db->maxmaxcode) { 758 struct bsd_dict *dictp2; 759 /* expand code size if needed */ 760 if (max_ent >= MAXCODE(n_bits)) 761 db->n_bits = ++n_bits; 762 763 /* Invalidate previous hash table entry 764 * assigned this code, and then take it over. 765 */ 766 dictp2 = &db->dict[max_ent+1]; 767 if (db->dict[dictp2->cptr].codem1 == max_ent) 768 db->dict[dictp2->cptr].codem1 = BADCODEM1; 769 dictp2->cptr = hval; 770 dictp->codem1 = max_ent; 771 dictp->f.fcode = fcode; 772 773 db->max_ent = ++max_ent; 774 db->lens[max_ent] = db->lens[ent]+1; 775 } 776 ent = c; 777 } while (--slen != 0); 778 } 779 bitno += n_bits; /* output (count) the last code */ 780 db->bytes_out += bitno/8; 781 db->in_count += ilen; 782 (void)bsd_check(db); 783 784 ++db->incomp_count; 785 db->incomp_bytes += ilen; 786 ++db->uncomp_count; 787 db->uncomp_bytes += ilen; 788 789 /* Increase code size if we would have without the packet 790 * boundary and as the decompressor will. 791 */ 792 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 793 db->n_bits++; 794 } 795 796 797 /* 798 * Decompress "BSD Compress". 799 * 800 * Because of patent problems, we return DECOMP_ERROR for errors 801 * found by inspecting the input data and for system problems, but 802 * DECOMP_FATALERROR for any errors which could possibly be said to 803 * be being detected "after" decompression. For DECOMP_ERROR, 804 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 805 * infringing a patent of Motorola's if we do, so we take CCP down 806 * instead. 807 * 808 * Given that the frame has the correct sequence number and a good FCS, 809 * errors such as invalid codes in the input most likely indicate a 810 * bug, so we return DECOMP_FATALERROR for them in order to turn off 811 * compression, even though they are detected by inspecting the input. 812 */ 813 int 814 bsd_decompress(state, cmp, dmpp) 815 void *state; 816 struct mbuf *cmp, **dmpp; 817 { 818 struct bsd_db *db = (struct bsd_db *) state; 819 u_int max_ent = db->max_ent; 820 u_int32_t accm = 0; 821 u_int bitno = 32; /* 1st valid bit in accm */ 822 u_int n_bits = db->n_bits; 823 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 824 struct bsd_dict *dictp; 825 int explen, i, seq, len; 826 u_int incode, oldcode, finchar; 827 u_char *p, *rptr, *wptr; 828 struct mbuf *m, *dmp, *mret; 829 int adrs, ctrl, ilen; 830 int space, codelen, extra; 831 832 /* 833 * Save the address/control from the PPP header 834 * and then get the sequence number. 835 */ 836 *dmpp = NULL; 837 rptr = mtod(cmp, u_char *); 838 adrs = PPP_ADDRESS(rptr); 839 ctrl = PPP_CONTROL(rptr); 840 rptr += PPP_HDRLEN; 841 len = cmp->m_len - PPP_HDRLEN; 842 seq = 0; 843 for (i = 0; i < 2; ++i) { 844 while (len <= 0) { 845 cmp = cmp->m_next; 846 if (cmp == NULL) 847 return DECOMP_ERROR; 848 rptr = mtod(cmp, u_char *); 849 len = cmp->m_len; 850 } 851 seq = (seq << 8) + *rptr++; 852 --len; 853 } 854 855 /* 856 * Check the sequence number and give up if it differs from 857 * the value we're expecting. 858 */ 859 if (seq != db->seqno) { 860 if (db->debug) 861 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 862 db->unit, seq, db->seqno - 1); 863 return DECOMP_ERROR; 864 } 865 ++db->seqno; 866 867 /* 868 * Allocate one mbuf to start with. 869 */ 870 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 871 if (dmp == NULL) 872 return DECOMP_ERROR; 873 mret = dmp; 874 dmp->m_len = 0; 875 dmp->m_next = NULL; 876 MCLGET(dmp, M_DONTWAIT); 877 dmp->m_data += db->hdrlen; 878 wptr = mtod(dmp, u_char *); 879 space = m_trailingspace(dmp) - PPP_HDRLEN + 1; 880 881 /* 882 * Fill in the ppp header, but not the last byte of the protocol 883 * (that comes from the decompressed data). 884 */ 885 wptr[0] = adrs; 886 wptr[1] = ctrl; 887 wptr[2] = 0; 888 wptr += PPP_HDRLEN - 1; 889 890 ilen = len; 891 oldcode = CLEAR; 892 explen = 0; 893 for (;;) { 894 if (len == 0) { 895 cmp = cmp->m_next; 896 if (!cmp) /* quit at end of message */ 897 break; 898 rptr = mtod(cmp, u_char *); 899 len = cmp->m_len; 900 ilen += len; 901 continue; /* handle 0-length buffers */ 902 } 903 904 /* 905 * Accumulate bytes until we have a complete code. 906 * Then get the next code, relying on the 32-bit, 907 * unsigned accm to mask the result. 908 */ 909 bitno -= 8; 910 accm |= *rptr++ << bitno; 911 --len; 912 if (tgtbitno < bitno) 913 continue; 914 incode = accm >> tgtbitno; 915 accm <<= n_bits; 916 bitno += n_bits; 917 918 if (incode == CLEAR) { 919 /* 920 * The dictionary must only be cleared at 921 * the end of a packet. But there could be an 922 * empty mbuf at the end. 923 */ 924 if (len > 0 || cmp->m_next != NULL) { 925 while ((cmp = cmp->m_next) != NULL) 926 len += cmp->m_len; 927 if (len > 0) { 928 m_freem(mret); 929 if (db->debug) 930 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 931 return DECOMP_FATALERROR; /* probably a bug */ 932 } 933 } 934 bsd_clear(db); 935 explen = ilen = 0; 936 break; 937 } 938 939 if (incode > max_ent + 2 || incode > db->maxmaxcode 940 || (incode > max_ent && oldcode == CLEAR)) { 941 m_freem(mret); 942 if (db->debug) { 943 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 944 db->unit, incode, oldcode); 945 printf("max_ent=0x%x explen=%d seqno=%d\n", 946 max_ent, explen, db->seqno); 947 } 948 return DECOMP_FATALERROR; /* probably a bug */ 949 } 950 951 /* Special case for KwKwK string. */ 952 if (incode > max_ent) { 953 finchar = oldcode; 954 extra = 1; 955 } else { 956 finchar = incode; 957 extra = 0; 958 } 959 960 codelen = db->lens[finchar]; 961 explen += codelen + extra; 962 if (explen > db->mru + 1) { 963 m_freem(mret); 964 if (db->debug) { 965 printf("bsd_decomp%d: ran out of mru\n", db->unit); 966 #ifdef DEBUG 967 while ((cmp = cmp->m_next) != NULL) 968 len += cmp->m_len; 969 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 970 len, finchar, codelen, explen); 971 #endif 972 } 973 return DECOMP_FATALERROR; 974 } 975 976 /* 977 * For simplicity, the decoded characters go in a single mbuf, 978 * so we allocate a single extra cluster mbuf if necessary. 979 */ 980 if ((space -= codelen + extra) < 0) { 981 dmp->m_len = wptr - mtod(dmp, u_char *); 982 MGET(m, M_DONTWAIT, MT_DATA); 983 if (m == NULL) { 984 m_freem(mret); 985 return DECOMP_ERROR; 986 } 987 m->m_len = 0; 988 m->m_next = NULL; 989 dmp->m_next = m; 990 MCLGET(m, M_DONTWAIT); 991 space = m_trailingspace(m) - (codelen + extra); 992 if (space < 0) { 993 /* now that's what I call *compression*. */ 994 m_freem(mret); 995 return DECOMP_ERROR; 996 } 997 dmp = m; 998 wptr = mtod(dmp, u_char *); 999 } 1000 1001 /* 1002 * Decode this code and install it in the decompressed buffer. 1003 */ 1004 p = (wptr += codelen); 1005 while (finchar > LAST) { 1006 dictp = &db->dict[db->dict[finchar].cptr]; 1007 #ifdef DEBUG 1008 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1009 goto bad; 1010 #endif 1011 *--p = dictp->f.hs.suffix; 1012 finchar = dictp->f.hs.prefix; 1013 } 1014 *--p = finchar; 1015 1016 #ifdef DEBUG 1017 if (--codelen != 0) 1018 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1019 db->unit, codelen, incode, max_ent); 1020 #endif 1021 1022 if (extra) /* the KwKwK case again */ 1023 *wptr++ = finchar; 1024 1025 /* 1026 * If not first code in a packet, and 1027 * if not out of code space, then allocate a new code. 1028 * 1029 * Keep the hash table correct so it can be used 1030 * with uncompressed packets. 1031 */ 1032 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1033 struct bsd_dict *dictp2; 1034 u_int32_t fcode; 1035 u_int32_t hval, disp; 1036 1037 fcode = BSD_KEY(oldcode,finchar); 1038 hval = BSD_HASH(oldcode,finchar,db->hshift); 1039 dictp = &db->dict[hval]; 1040 1041 /* look for a free hash table entry */ 1042 if (dictp->codem1 < max_ent) { 1043 disp = (hval == 0) ? 1 : hval; 1044 do { 1045 hval += disp; 1046 if (hval >= db->hsize) 1047 hval -= db->hsize; 1048 dictp = &db->dict[hval]; 1049 } while (dictp->codem1 < max_ent); 1050 } 1051 1052 /* 1053 * Invalidate previous hash table entry 1054 * assigned this code, and then take it over 1055 */ 1056 dictp2 = &db->dict[max_ent+1]; 1057 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1058 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1059 } 1060 dictp2->cptr = hval; 1061 dictp->codem1 = max_ent; 1062 dictp->f.fcode = fcode; 1063 1064 db->max_ent = ++max_ent; 1065 db->lens[max_ent] = db->lens[oldcode]+1; 1066 1067 /* Expand code size if needed. */ 1068 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1069 db->n_bits = ++n_bits; 1070 tgtbitno = 32-n_bits; 1071 } 1072 } 1073 oldcode = incode; 1074 } 1075 dmp->m_len = wptr - mtod(dmp, u_char *); 1076 1077 /* 1078 * Keep the checkpoint right so that incompressible packets 1079 * clear the dictionary at the right times. 1080 */ 1081 db->bytes_out += ilen; 1082 db->in_count += explen; 1083 if (bsd_check(db) && db->debug) { 1084 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1085 db->unit); 1086 } 1087 1088 ++db->comp_count; 1089 db->comp_bytes += ilen + BSD_OVHD; 1090 ++db->uncomp_count; 1091 db->uncomp_bytes += explen; 1092 1093 *dmpp = mret; 1094 return DECOMP_OK; 1095 1096 #ifdef DEBUG 1097 bad: 1098 if (codelen <= 0) { 1099 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1100 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1101 incode, finchar, db->dict[finchar].cptr, max_ent); 1102 } else if (dictp->codem1 != finchar-1) { 1103 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1104 db->unit, incode, finchar); 1105 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1106 db->dict[finchar].cptr, dictp->codem1); 1107 } 1108 m_freem(mret); 1109 return DECOMP_FATALERROR; 1110 #endif /* DEBUG */ 1111 } 1112 #endif /* DO_BSD_COMPRESS */ 1113