1 /* $OpenBSD: bsd-comp.c,v 1.3 1996/04/21 22:28:28 deraadt Exp $ */ 2 /* $NetBSD: bsd-comp.c,v 1.4 1996/03/15 02:28:00 paulus Exp $ */ 3 4 /* Because this code is derived from the 4.3BSD compress source: 5 * 6 * 7 * Copyright (c) 1985, 1986 The Regents of the University of California. 8 * All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * James A. Woods, derived from original work by Spencer Thomas 12 * and Joseph Orost. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. All advertising materials mentioning features or use of this software 23 * must display the following acknowledgement: 24 * This product includes software developed by the University of 25 * California, Berkeley and its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 */ 42 43 /* 44 * This version is for use with mbufs on BSD-derived systems. 45 * 46 * $Id: bsd-comp.c,v 1.3 1996/04/21 22:28:28 deraadt Exp $ 47 */ 48 49 #include <sys/param.h> 50 #include <sys/types.h> 51 #include <sys/systm.h> 52 #include <sys/mbuf.h> 53 #include <sys/socket.h> 54 #include <net/if.h> 55 #include <net/if_types.h> 56 #include <net/ppp_defs.h> 57 #include <net/if_ppp.h> 58 59 #define PACKETPTR struct mbuf * 60 #include <net/ppp-comp.h> 61 62 #if DO_BSD_COMPRESS 63 /* 64 * PPP "BSD compress" compression 65 * The differences between this compression and the classic BSD LZW 66 * source are obvious from the requirement that the classic code worked 67 * with files while this handles arbitrarily long streams that 68 * are broken into packets. They are: 69 * 70 * When the code size expands, a block of junk is not emitted by 71 * the compressor and not expected by the decompressor. 72 * 73 * New codes are not necessarily assigned every time an old 74 * code is output by the compressor. This is because a packet 75 * end forces a code to be emitted, but does not imply that a 76 * new sequence has been seen. 77 * 78 * The compression ratio is checked at the first end of a packet 79 * after the appropriate gap. Besides simplifying and speeding 80 * things up, this makes it more likely that the transmitter 81 * and receiver will agree when the dictionary is cleared when 82 * compression is not going well. 83 */ 84 85 /* 86 * A dictionary for doing BSD compress. 87 */ 88 struct bsd_db { 89 int totlen; /* length of this structure */ 90 u_int hsize; /* size of the hash table */ 91 u_char hshift; /* used in hash function */ 92 u_char n_bits; /* current bits/code */ 93 u_char maxbits; 94 u_char debug; 95 u_char unit; 96 u_int16_t seqno; /* sequence # of next packet */ 97 u_int hdrlen; /* header length to preallocate */ 98 u_int mru; 99 u_int maxmaxcode; /* largest valid code */ 100 u_int max_ent; /* largest code in use */ 101 u_int in_count; /* uncompressed bytes, aged */ 102 u_int bytes_out; /* compressed bytes, aged */ 103 u_int ratio; /* recent compression ratio */ 104 u_int checkpoint; /* when to next check the ratio */ 105 u_int clear_count; /* times dictionary cleared */ 106 u_int incomp_count; /* incompressible packets */ 107 u_int incomp_bytes; /* incompressible bytes */ 108 u_int uncomp_count; /* uncompressed packets */ 109 u_int uncomp_bytes; /* uncompressed bytes */ 110 u_int comp_count; /* compressed packets */ 111 u_int comp_bytes; /* compressed bytes */ 112 u_int16_t *lens; /* array of lengths of codes */ 113 struct bsd_dict { 114 union { /* hash value */ 115 u_int32_t fcode; 116 struct { 117 #if BYTE_ORDER == LITTLE_ENDIAN 118 u_int16_t prefix; /* preceding code */ 119 u_char suffix; /* last character of new code */ 120 u_char pad; 121 #else 122 u_char pad; 123 u_char suffix; /* last character of new code */ 124 u_int16_t prefix; /* preceding code */ 125 #endif 126 } hs; 127 } f; 128 u_int16_t codem1; /* output of hash table -1 */ 129 u_int16_t cptr; /* map code to hash table entry */ 130 } dict[1]; 131 }; 132 133 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 134 #define BSD_INIT_BITS BSD_MIN_BITS 135 136 static void *bsd_comp_alloc __P((u_char *options, int opt_len)); 137 static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); 138 static void bsd_free __P((void *state)); 139 static int bsd_comp_init __P((void *state, u_char *options, int opt_len, 140 int unit, int hdrlen, int debug)); 141 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, 142 int unit, int hdrlen, int mru, int debug)); 143 static int bsd_compress __P((void *state, struct mbuf **mret, 144 struct mbuf *mp, int slen, int maxolen)); 145 static void bsd_incomp __P((void *state, struct mbuf *dmsg)); 146 static int bsd_decompress __P((void *state, struct mbuf *cmp, 147 struct mbuf **dmpp)); 148 static void bsd_reset __P((void *state)); 149 static void bsd_comp_stats __P((void *state, struct compstat *stats)); 150 151 /* 152 * Procedures exported to if_ppp.c. 153 */ 154 struct compressor ppp_bsd_compress = { 155 CI_BSD_COMPRESS, /* compress_proto */ 156 bsd_comp_alloc, /* comp_alloc */ 157 bsd_free, /* comp_free */ 158 bsd_comp_init, /* comp_init */ 159 bsd_reset, /* comp_reset */ 160 bsd_compress, /* compress */ 161 bsd_comp_stats, /* comp_stat */ 162 bsd_decomp_alloc, /* decomp_alloc */ 163 bsd_free, /* decomp_free */ 164 bsd_decomp_init, /* decomp_init */ 165 bsd_reset, /* decomp_reset */ 166 bsd_decompress, /* decompress */ 167 bsd_incomp, /* incomp */ 168 bsd_comp_stats, /* decomp_stat */ 169 }; 170 171 /* 172 * the next two codes should not be changed lightly, as they must not 173 * lie within the contiguous general code space. 174 */ 175 #define CLEAR 256 /* table clear output code */ 176 #define FIRST 257 /* first free entry */ 177 #define LAST 255 178 179 #define MAXCODE(b) ((1 << (b)) - 1) 180 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 181 182 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 183 ^ (u_int32_t)(prefix)) 184 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 185 + (u_int32_t)(prefix)) 186 187 #define CHECK_GAP 10000 /* Ratio check interval */ 188 189 #define RATIO_SCALE_LOG 8 190 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 191 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 192 193 static void bsd_clear __P((struct bsd_db *)); 194 static int bsd_check __P((struct bsd_db *)); 195 static void *bsd_alloc __P((u_char *, int, int)); 196 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int, 197 int, int)); 198 199 /* 200 * clear the dictionary 201 */ 202 static void 203 bsd_clear(db) 204 struct bsd_db *db; 205 { 206 db->clear_count++; 207 db->max_ent = FIRST-1; 208 db->n_bits = BSD_INIT_BITS; 209 db->ratio = 0; 210 db->bytes_out = 0; 211 db->in_count = 0; 212 db->incomp_count = 0; 213 db->checkpoint = CHECK_GAP; 214 } 215 216 /* 217 * If the dictionary is full, then see if it is time to reset it. 218 * 219 * Compute the compression ratio using fixed-point arithmetic 220 * with 8 fractional bits. 221 * 222 * Since we have an infinite stream instead of a single file, 223 * watch only the local compression ratio. 224 * 225 * Since both peers must reset the dictionary at the same time even in 226 * the absence of CLEAR codes (while packets are incompressible), they 227 * must compute the same ratio. 228 */ 229 static int /* 1=output CLEAR */ 230 bsd_check(db) 231 struct bsd_db *db; 232 { 233 u_int new_ratio; 234 235 if (db->in_count >= db->checkpoint) { 236 /* age the ratio by limiting the size of the counts */ 237 if (db->in_count >= RATIO_MAX 238 || db->bytes_out >= RATIO_MAX) { 239 db->in_count -= db->in_count/4; 240 db->bytes_out -= db->bytes_out/4; 241 } 242 243 db->checkpoint = db->in_count + CHECK_GAP; 244 245 if (db->max_ent >= db->maxmaxcode) { 246 /* Reset the dictionary only if the ratio is worse, 247 * or if it looks as if it has been poisoned 248 * by incompressible data. 249 * 250 * This does not overflow, because 251 * db->in_count <= RATIO_MAX. 252 */ 253 new_ratio = db->in_count << RATIO_SCALE_LOG; 254 if (db->bytes_out != 0) 255 new_ratio /= db->bytes_out; 256 257 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 258 bsd_clear(db); 259 return 1; 260 } 261 db->ratio = new_ratio; 262 } 263 } 264 return 0; 265 } 266 267 /* 268 * Return statistics. 269 */ 270 static void 271 bsd_comp_stats(state, stats) 272 void *state; 273 struct compstat *stats; 274 { 275 struct bsd_db *db = (struct bsd_db *) state; 276 u_int out; 277 278 stats->unc_bytes = db->uncomp_bytes; 279 stats->unc_packets = db->uncomp_count; 280 stats->comp_bytes = db->comp_bytes; 281 stats->comp_packets = db->comp_count; 282 stats->inc_bytes = db->incomp_bytes; 283 stats->inc_packets = db->incomp_count; 284 stats->ratio = db->in_count; 285 out = db->bytes_out; 286 if (stats->ratio <= 0x7fffff) 287 stats->ratio <<= 8; 288 else 289 out >>= 8; 290 if (out != 0) 291 stats->ratio /= out; 292 } 293 294 /* 295 * Reset state, as on a CCP ResetReq. 296 */ 297 static void 298 bsd_reset(state) 299 void *state; 300 { 301 struct bsd_db *db = (struct bsd_db *) state; 302 303 db->seqno = 0; 304 bsd_clear(db); 305 db->clear_count = 0; 306 } 307 308 /* 309 * Allocate space for a (de) compressor. 310 */ 311 static void * 312 bsd_alloc(options, opt_len, decomp) 313 u_char *options; 314 int opt_len, decomp; 315 { 316 int bits; 317 u_int newlen, hsize, hshift, maxmaxcode; 318 struct bsd_db *db; 319 320 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 321 || options[1] != CILEN_BSD_COMPRESS 322 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 323 return NULL; 324 bits = BSD_NBITS(options[2]); 325 switch (bits) { 326 case 9: /* needs 82152 for both directions */ 327 case 10: /* needs 84144 */ 328 case 11: /* needs 88240 */ 329 case 12: /* needs 96432 */ 330 hsize = 5003; 331 hshift = 4; 332 break; 333 case 13: /* needs 176784 */ 334 hsize = 9001; 335 hshift = 5; 336 break; 337 case 14: /* needs 353744 */ 338 hsize = 18013; 339 hshift = 6; 340 break; 341 case 15: /* needs 691440 */ 342 hsize = 35023; 343 hshift = 7; 344 break; 345 case 16: /* needs 1366160--far too much, */ 346 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 347 /* hshift = 8; */ /* in struct bsd_db */ 348 /* break; */ 349 default: 350 return NULL; 351 } 352 353 maxmaxcode = MAXCODE(bits); 354 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 355 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT); 356 if (!db) 357 return NULL; 358 bzero(db, sizeof(*db) - sizeof(db->dict)); 359 360 if (!decomp) { 361 db->lens = NULL; 362 } else { 363 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]), 364 M_DEVBUF, M_NOWAIT); 365 if (!db->lens) { 366 FREE(db, M_DEVBUF); 367 return NULL; 368 } 369 } 370 371 db->totlen = newlen; 372 db->hsize = hsize; 373 db->hshift = hshift; 374 db->maxmaxcode = maxmaxcode; 375 db->maxbits = bits; 376 377 return (void *) db; 378 } 379 380 static void 381 bsd_free(state) 382 void *state; 383 { 384 struct bsd_db *db = (struct bsd_db *) state; 385 386 if (db->lens) 387 FREE(db->lens, M_DEVBUF); 388 FREE(db, M_DEVBUF); 389 } 390 391 static void * 392 bsd_comp_alloc(options, opt_len) 393 u_char *options; 394 int opt_len; 395 { 396 return bsd_alloc(options, opt_len, 0); 397 } 398 399 static void * 400 bsd_decomp_alloc(options, opt_len) 401 u_char *options; 402 int opt_len; 403 { 404 return bsd_alloc(options, opt_len, 1); 405 } 406 407 /* 408 * Initialize the database. 409 */ 410 static int 411 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 412 struct bsd_db *db; 413 u_char *options; 414 int opt_len, unit, hdrlen, mru, debug, decomp; 415 { 416 int i; 417 418 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 419 || options[1] != CILEN_BSD_COMPRESS 420 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 421 || BSD_NBITS(options[2]) != db->maxbits 422 || (decomp && db->lens == NULL)) 423 return 0; 424 425 if (decomp) { 426 i = LAST+1; 427 while (i != 0) 428 db->lens[--i] = 1; 429 } 430 i = db->hsize; 431 while (i != 0) { 432 db->dict[--i].codem1 = BADCODEM1; 433 db->dict[i].cptr = 0; 434 } 435 436 db->unit = unit; 437 db->hdrlen = hdrlen; 438 db->mru = mru; 439 #ifndef DEBUG 440 if (debug) 441 #endif 442 db->debug = 1; 443 444 bsd_reset(db); 445 446 return 1; 447 } 448 449 static int 450 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 451 void *state; 452 u_char *options; 453 int opt_len, unit, hdrlen, debug; 454 { 455 return bsd_init((struct bsd_db *) state, options, opt_len, 456 unit, hdrlen, 0, debug, 0); 457 } 458 459 static int 460 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 461 void *state; 462 u_char *options; 463 int opt_len, unit, hdrlen, mru, debug; 464 { 465 return bsd_init((struct bsd_db *) state, options, opt_len, 466 unit, hdrlen, mru, debug, 1); 467 } 468 469 470 /* 471 * compress a packet 472 * One change from the BSD compress command is that when the 473 * code size expands, we do not output a bunch of padding. 474 */ 475 int /* new slen */ 476 bsd_compress(state, mret, mp, slen, maxolen) 477 void *state; 478 struct mbuf **mret; /* return compressed mbuf chain here */ 479 struct mbuf *mp; /* from here */ 480 int slen; /* uncompressed length */ 481 int maxolen; /* max compressed length */ 482 { 483 struct bsd_db *db = (struct bsd_db *) state; 484 int hshift = db->hshift; 485 u_int max_ent = db->max_ent; 486 u_int n_bits = db->n_bits; 487 u_int bitno = 32; 488 u_int32_t accm = 0, fcode; 489 struct bsd_dict *dictp; 490 u_char c; 491 int hval, disp, ent, ilen; 492 u_char *rptr, *wptr; 493 u_char *cp_end; 494 int olen; 495 struct mbuf *m; 496 497 #define PUTBYTE(v) { \ 498 ++olen; \ 499 if (wptr) { \ 500 *wptr++ = (v); \ 501 if (wptr >= cp_end) { \ 502 m->m_len = wptr - mtod(m, u_char *); \ 503 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 504 m = m->m_next; \ 505 if (m) { \ 506 m->m_len = 0; \ 507 if (maxolen - olen > MLEN) \ 508 MCLGET(m, M_DONTWAIT); \ 509 wptr = mtod(m, u_char *); \ 510 cp_end = wptr + M_TRAILINGSPACE(m); \ 511 } else \ 512 wptr = NULL; \ 513 } \ 514 } \ 515 } 516 517 #define OUTPUT(ent) { \ 518 bitno -= n_bits; \ 519 accm |= ((ent) << bitno); \ 520 do { \ 521 PUTBYTE(accm >> 24); \ 522 accm <<= 8; \ 523 bitno += 8; \ 524 } while (bitno <= 24); \ 525 } 526 527 /* 528 * If the protocol is not in the range we're interested in, 529 * just return without compressing the packet. If it is, 530 * the protocol becomes the first byte to compress. 531 */ 532 rptr = mtod(mp, u_char *); 533 ent = PPP_PROTOCOL(rptr); 534 if (ent < 0x21 || ent > 0xf9) { 535 *mret = NULL; 536 return slen; 537 } 538 539 /* Don't generate compressed packets which are larger than 540 the uncompressed packet. */ 541 if (maxolen > slen) 542 maxolen = slen; 543 544 /* Allocate one mbuf to start with. */ 545 MGET(m, M_DONTWAIT, MT_DATA); 546 *mret = m; 547 if (m != NULL) { 548 m->m_len = 0; 549 if (maxolen + db->hdrlen > MLEN) 550 MCLGET(m, M_DONTWAIT); 551 m->m_data += db->hdrlen; 552 wptr = mtod(m, u_char *); 553 cp_end = wptr + M_TRAILINGSPACE(m); 554 } else 555 wptr = cp_end = NULL; 556 557 /* 558 * Copy the PPP header over, changing the protocol, 559 * and install the 2-byte packet sequence number. 560 */ 561 if (wptr) { 562 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 563 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 564 *wptr++ = 0; /* change the protocol */ 565 *wptr++ = PPP_COMP; 566 *wptr++ = db->seqno >> 8; 567 *wptr++ = db->seqno; 568 } 569 ++db->seqno; 570 571 olen = 0; 572 rptr += PPP_HDRLEN; 573 slen = mp->m_len - PPP_HDRLEN; 574 ilen = slen + 1; 575 for (;;) { 576 if (slen <= 0) { 577 mp = mp->m_next; 578 if (!mp) 579 break; 580 rptr = mtod(mp, u_char *); 581 slen = mp->m_len; 582 if (!slen) 583 continue; /* handle 0-length buffers */ 584 ilen += slen; 585 } 586 587 slen--; 588 c = *rptr++; 589 fcode = BSD_KEY(ent, c); 590 hval = BSD_HASH(ent, c, hshift); 591 dictp = &db->dict[hval]; 592 593 /* Validate and then check the entry. */ 594 if (dictp->codem1 >= max_ent) 595 goto nomatch; 596 if (dictp->f.fcode == fcode) { 597 ent = dictp->codem1+1; 598 continue; /* found (prefix,suffix) */ 599 } 600 601 /* continue probing until a match or invalid entry */ 602 disp = (hval == 0) ? 1 : hval; 603 do { 604 hval += disp; 605 if (hval >= db->hsize) 606 hval -= db->hsize; 607 dictp = &db->dict[hval]; 608 if (dictp->codem1 >= max_ent) 609 goto nomatch; 610 } while (dictp->f.fcode != fcode); 611 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 612 continue; 613 614 nomatch: 615 OUTPUT(ent); /* output the prefix */ 616 617 /* code -> hashtable */ 618 if (max_ent < db->maxmaxcode) { 619 struct bsd_dict *dictp2; 620 /* expand code size if needed */ 621 if (max_ent >= MAXCODE(n_bits)) 622 db->n_bits = ++n_bits; 623 624 /* Invalidate old hash table entry using 625 * this code, and then take it over. 626 */ 627 dictp2 = &db->dict[max_ent+1]; 628 if (db->dict[dictp2->cptr].codem1 == max_ent) 629 db->dict[dictp2->cptr].codem1 = BADCODEM1; 630 dictp2->cptr = hval; 631 dictp->codem1 = max_ent; 632 dictp->f.fcode = fcode; 633 634 db->max_ent = ++max_ent; 635 } 636 ent = c; 637 } 638 639 OUTPUT(ent); /* output the last code */ 640 db->bytes_out += olen; 641 db->in_count += ilen; 642 if (bitno < 32) 643 ++db->bytes_out; /* count complete bytes */ 644 645 if (bsd_check(db)) 646 OUTPUT(CLEAR); /* do not count the CLEAR */ 647 648 /* 649 * Pad dribble bits of last code with ones. 650 * Do not emit a completely useless byte of ones. 651 */ 652 if (bitno != 32) 653 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 654 655 if (m != NULL) { 656 m->m_len = wptr - mtod(m, u_char *); 657 m->m_next = NULL; 658 } 659 660 /* 661 * Increase code size if we would have without the packet 662 * boundary and as the decompressor will. 663 */ 664 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 665 db->n_bits++; 666 667 db->uncomp_bytes += ilen; 668 ++db->uncomp_count; 669 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 670 /* throw away the compressed stuff if it is longer than uncompressed */ 671 if (*mret != NULL) { 672 m_freem(*mret); 673 *mret = NULL; 674 } 675 ++db->incomp_count; 676 db->incomp_bytes += ilen; 677 } else { 678 ++db->comp_count; 679 db->comp_bytes += olen + BSD_OVHD; 680 } 681 682 return olen + PPP_HDRLEN + BSD_OVHD; 683 #undef OUTPUT 684 #undef PUTBYTE 685 } 686 687 688 /* 689 * Update the "BSD Compress" dictionary on the receiver for 690 * incompressible data by pretending to compress the incoming data. 691 */ 692 static void 693 bsd_incomp(state, dmsg) 694 void *state; 695 struct mbuf *dmsg; 696 { 697 struct bsd_db *db = (struct bsd_db *) state; 698 u_int hshift = db->hshift; 699 u_int max_ent = db->max_ent; 700 u_int n_bits = db->n_bits; 701 struct bsd_dict *dictp; 702 u_int32_t fcode; 703 u_char c; 704 u_int32_t hval, disp; 705 int slen, ilen; 706 u_int bitno = 7; 707 u_char *rptr; 708 u_int ent; 709 710 /* 711 * If the protocol is not in the range we're interested in, 712 * just return without looking at the packet. If it is, 713 * the protocol becomes the first byte to "compress". 714 */ 715 rptr = mtod(dmsg, u_char *); 716 ent = PPP_PROTOCOL(rptr); 717 if (ent < 0x21 || ent > 0xf9) 718 return; 719 720 db->incomp_count++; 721 db->seqno++; 722 ilen = 1; /* count the protocol as 1 byte */ 723 rptr += PPP_HDRLEN; 724 slen = dmsg->m_len - PPP_HDRLEN; 725 for (;;) { 726 if (slen <= 0) { 727 dmsg = dmsg->m_next; 728 if (!dmsg) 729 break; 730 rptr = mtod(dmsg, u_char *); 731 slen = dmsg->m_len; 732 continue; 733 } 734 ilen += slen; 735 736 do { 737 c = *rptr++; 738 fcode = BSD_KEY(ent, c); 739 hval = BSD_HASH(ent, c, hshift); 740 dictp = &db->dict[hval]; 741 742 /* validate and then check the entry */ 743 if (dictp->codem1 >= max_ent) 744 goto nomatch; 745 if (dictp->f.fcode == fcode) { 746 ent = dictp->codem1+1; 747 continue; /* found (prefix,suffix) */ 748 } 749 750 /* continue probing until a match or invalid entry */ 751 disp = (hval == 0) ? 1 : hval; 752 do { 753 hval += disp; 754 if (hval >= db->hsize) 755 hval -= db->hsize; 756 dictp = &db->dict[hval]; 757 if (dictp->codem1 >= max_ent) 758 goto nomatch; 759 } while (dictp->f.fcode != fcode); 760 ent = dictp->codem1+1; 761 continue; /* finally found (prefix,suffix) */ 762 763 nomatch: /* output (count) the prefix */ 764 bitno += n_bits; 765 766 /* code -> hashtable */ 767 if (max_ent < db->maxmaxcode) { 768 struct bsd_dict *dictp2; 769 /* expand code size if needed */ 770 if (max_ent >= MAXCODE(n_bits)) 771 db->n_bits = ++n_bits; 772 773 /* Invalidate previous hash table entry 774 * assigned this code, and then take it over. 775 */ 776 dictp2 = &db->dict[max_ent+1]; 777 if (db->dict[dictp2->cptr].codem1 == max_ent) 778 db->dict[dictp2->cptr].codem1 = BADCODEM1; 779 dictp2->cptr = hval; 780 dictp->codem1 = max_ent; 781 dictp->f.fcode = fcode; 782 783 db->max_ent = ++max_ent; 784 db->lens[max_ent] = db->lens[ent]+1; 785 } 786 ent = c; 787 } while (--slen != 0); 788 } 789 bitno += n_bits; /* output (count) the last code */ 790 db->bytes_out += bitno/8; 791 db->in_count += ilen; 792 (void)bsd_check(db); 793 794 ++db->incomp_count; 795 db->incomp_bytes += ilen; 796 ++db->uncomp_count; 797 db->uncomp_bytes += ilen; 798 799 /* Increase code size if we would have without the packet 800 * boundary and as the decompressor will. 801 */ 802 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 803 db->n_bits++; 804 } 805 806 807 /* 808 * Decompress "BSD Compress". 809 * 810 * Because of patent problems, we return DECOMP_ERROR for errors 811 * found by inspecting the input data and for system problems, but 812 * DECOMP_FATALERROR for any errors which could possibly be said to 813 * be being detected "after" decompression. For DECOMP_ERROR, 814 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 815 * infringing a patent of Motorola's if we do, so we take CCP down 816 * instead. 817 * 818 * Given that the frame has the correct sequence number and a good FCS, 819 * errors such as invalid codes in the input most likely indicate a 820 * bug, so we return DECOMP_FATALERROR for them in order to turn off 821 * compression, even though they are detected by inspecting the input. 822 */ 823 int 824 bsd_decompress(state, cmp, dmpp) 825 void *state; 826 struct mbuf *cmp, **dmpp; 827 { 828 struct bsd_db *db = (struct bsd_db *) state; 829 u_int max_ent = db->max_ent; 830 u_int32_t accm = 0; 831 u_int bitno = 32; /* 1st valid bit in accm */ 832 u_int n_bits = db->n_bits; 833 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 834 struct bsd_dict *dictp; 835 int explen, i, seq, len; 836 u_int incode, oldcode, finchar; 837 u_char *p, *rptr, *wptr; 838 struct mbuf *m, *dmp, *mret; 839 int adrs, ctrl, ilen; 840 int space, codelen, extra; 841 842 /* 843 * Save the address/control from the PPP header 844 * and then get the sequence number. 845 */ 846 *dmpp = NULL; 847 rptr = mtod(cmp, u_char *); 848 adrs = PPP_ADDRESS(rptr); 849 ctrl = PPP_CONTROL(rptr); 850 rptr += PPP_HDRLEN; 851 len = cmp->m_len - PPP_HDRLEN; 852 seq = 0; 853 for (i = 0; i < 2; ++i) { 854 while (len <= 0) { 855 cmp = cmp->m_next; 856 if (cmp == NULL) 857 return DECOMP_ERROR; 858 rptr = mtod(cmp, u_char *); 859 len = cmp->m_len; 860 } 861 seq = (seq << 8) + *rptr++; 862 --len; 863 } 864 865 /* 866 * Check the sequence number and give up if it differs from 867 * the value we're expecting. 868 */ 869 if (seq != db->seqno) { 870 if (db->debug) 871 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 872 db->unit, seq, db->seqno - 1); 873 return DECOMP_ERROR; 874 } 875 ++db->seqno; 876 877 /* 878 * Allocate one mbuf to start with. 879 */ 880 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 881 if (dmp == NULL) 882 return DECOMP_ERROR; 883 mret = dmp; 884 dmp->m_len = 0; 885 dmp->m_next = NULL; 886 MCLGET(dmp, M_DONTWAIT); 887 dmp->m_data += db->hdrlen; 888 wptr = mtod(dmp, u_char *); 889 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 890 891 /* 892 * Fill in the ppp header, but not the last byte of the protocol 893 * (that comes from the decompressed data). 894 */ 895 wptr[0] = adrs; 896 wptr[1] = ctrl; 897 wptr[2] = 0; 898 wptr += PPP_HDRLEN - 1; 899 900 ilen = len; 901 oldcode = CLEAR; 902 explen = 0; 903 for (;;) { 904 if (len == 0) { 905 cmp = cmp->m_next; 906 if (!cmp) /* quit at end of message */ 907 break; 908 rptr = mtod(cmp, u_char *); 909 len = cmp->m_len; 910 ilen += len; 911 continue; /* handle 0-length buffers */ 912 } 913 914 /* 915 * Accumulate bytes until we have a complete code. 916 * Then get the next code, relying on the 32-bit, 917 * unsigned accm to mask the result. 918 */ 919 bitno -= 8; 920 accm |= *rptr++ << bitno; 921 --len; 922 if (tgtbitno < bitno) 923 continue; 924 incode = accm >> tgtbitno; 925 accm <<= n_bits; 926 bitno += n_bits; 927 928 if (incode == CLEAR) { 929 /* 930 * The dictionary must only be cleared at 931 * the end of a packet. But there could be an 932 * empty mbuf at the end. 933 */ 934 if (len > 0 || cmp->m_next != NULL) { 935 while ((cmp = cmp->m_next) != NULL) 936 len += cmp->m_len; 937 if (len > 0) { 938 m_freem(mret); 939 if (db->debug) 940 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 941 return DECOMP_FATALERROR; /* probably a bug */ 942 } 943 } 944 bsd_clear(db); 945 explen = ilen = 0; 946 break; 947 } 948 949 if (incode > max_ent + 2 || incode > db->maxmaxcode 950 || (incode > max_ent && oldcode == CLEAR)) { 951 m_freem(mret); 952 if (db->debug) { 953 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 954 db->unit, incode, oldcode); 955 printf("max_ent=0x%x explen=%d seqno=%d\n", 956 max_ent, explen, db->seqno); 957 } 958 return DECOMP_FATALERROR; /* probably a bug */ 959 } 960 961 /* Special case for KwKwK string. */ 962 if (incode > max_ent) { 963 finchar = oldcode; 964 extra = 1; 965 } else { 966 finchar = incode; 967 extra = 0; 968 } 969 970 codelen = db->lens[finchar]; 971 explen += codelen + extra; 972 if (explen > db->mru + 1) { 973 m_freem(mret); 974 if (db->debug) { 975 printf("bsd_decomp%d: ran out of mru\n", db->unit); 976 #ifdef DEBUG 977 while ((cmp = cmp->m_next) != NULL) 978 len += cmp->m_len; 979 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 980 len, finchar, codelen, explen); 981 #endif 982 } 983 return DECOMP_FATALERROR; 984 } 985 986 /* 987 * For simplicity, the decoded characters go in a single mbuf, 988 * so we allocate a single extra cluster mbuf if necessary. 989 */ 990 if ((space -= codelen + extra) < 0) { 991 dmp->m_len = wptr - mtod(dmp, u_char *); 992 MGET(m, M_DONTWAIT, MT_DATA); 993 if (m == NULL) { 994 m_freem(mret); 995 return DECOMP_ERROR; 996 } 997 m->m_len = 0; 998 m->m_next = NULL; 999 dmp->m_next = m; 1000 MCLGET(m, M_DONTWAIT); 1001 space = M_TRAILINGSPACE(m) - (codelen + extra); 1002 if (space < 0) { 1003 /* now that's what I call *compression*. */ 1004 m_freem(mret); 1005 return DECOMP_ERROR; 1006 } 1007 dmp = m; 1008 wptr = mtod(dmp, u_char *); 1009 } 1010 1011 /* 1012 * Decode this code and install it in the decompressed buffer. 1013 */ 1014 p = (wptr += codelen); 1015 while (finchar > LAST) { 1016 dictp = &db->dict[db->dict[finchar].cptr]; 1017 #ifdef DEBUG 1018 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1019 goto bad; 1020 #endif 1021 *--p = dictp->f.hs.suffix; 1022 finchar = dictp->f.hs.prefix; 1023 } 1024 *--p = finchar; 1025 1026 #ifdef DEBUG 1027 if (--codelen != 0) 1028 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1029 db->unit, codelen, incode, max_ent); 1030 #endif 1031 1032 if (extra) /* the KwKwK case again */ 1033 *wptr++ = finchar; 1034 1035 /* 1036 * If not first code in a packet, and 1037 * if not out of code space, then allocate a new code. 1038 * 1039 * Keep the hash table correct so it can be used 1040 * with uncompressed packets. 1041 */ 1042 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1043 struct bsd_dict *dictp2; 1044 u_int32_t fcode; 1045 u_int32_t hval, disp; 1046 1047 fcode = BSD_KEY(oldcode,finchar); 1048 hval = BSD_HASH(oldcode,finchar,db->hshift); 1049 dictp = &db->dict[hval]; 1050 1051 /* look for a free hash table entry */ 1052 if (dictp->codem1 < max_ent) { 1053 disp = (hval == 0) ? 1 : hval; 1054 do { 1055 hval += disp; 1056 if (hval >= db->hsize) 1057 hval -= db->hsize; 1058 dictp = &db->dict[hval]; 1059 } while (dictp->codem1 < max_ent); 1060 } 1061 1062 /* 1063 * Invalidate previous hash table entry 1064 * assigned this code, and then take it over 1065 */ 1066 dictp2 = &db->dict[max_ent+1]; 1067 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1068 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1069 } 1070 dictp2->cptr = hval; 1071 dictp->codem1 = max_ent; 1072 dictp->f.fcode = fcode; 1073 1074 db->max_ent = ++max_ent; 1075 db->lens[max_ent] = db->lens[oldcode]+1; 1076 1077 /* Expand code size if needed. */ 1078 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1079 db->n_bits = ++n_bits; 1080 tgtbitno = 32-n_bits; 1081 } 1082 } 1083 oldcode = incode; 1084 } 1085 dmp->m_len = wptr - mtod(dmp, u_char *); 1086 1087 /* 1088 * Keep the checkpoint right so that incompressible packets 1089 * clear the dictionary at the right times. 1090 */ 1091 db->bytes_out += ilen; 1092 db->in_count += explen; 1093 if (bsd_check(db) && db->debug) { 1094 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1095 db->unit); 1096 } 1097 1098 ++db->comp_count; 1099 db->comp_bytes += ilen + BSD_OVHD; 1100 ++db->uncomp_count; 1101 db->uncomp_bytes += explen; 1102 1103 *dmpp = mret; 1104 return DECOMP_OK; 1105 1106 #ifdef DEBUG 1107 bad: 1108 if (codelen <= 0) { 1109 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1110 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1111 incode, finchar, db->dict[finchar].cptr, max_ent); 1112 } else if (dictp->codem1 != finchar-1) { 1113 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1114 db->unit, incode, finchar); 1115 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1116 db->dict[finchar].cptr, dictp->codem1); 1117 } 1118 m_freem(mret); 1119 return DECOMP_FATALERROR; 1120 #endif /* DEBUG */ 1121 } 1122 #endif /* DO_BSD_COMPRESS */ 1123