1 /* $NetBSD: bsd-comp.c,v 1.7 1997/03/12 20:26:46 christos Exp $ */ 2 /* Id: bsd-comp.c,v 1.6 1996/08/28 06:31:58 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 47 #include <sys/param.h> 48 #include <sys/types.h> 49 #include <sys/systm.h> 50 #include <sys/mbuf.h> 51 #include <sys/socket.h> 52 #include <net/if.h> 53 #include <net/if_types.h> 54 #include <net/ppp_defs.h> 55 #include <net/if_ppp.h> 56 57 #define PACKETPTR struct mbuf * 58 #include <net/ppp-comp.h> 59 60 #if DO_BSD_COMPRESS 61 /* 62 * PPP "BSD compress" compression 63 * The differences between this compression and the classic BSD LZW 64 * source are obvious from the requirement that the classic code worked 65 * with files while this handles arbitrarily long streams that 66 * are broken into packets. They are: 67 * 68 * When the code size expands, a block of junk is not emitted by 69 * the compressor and not expected by the decompressor. 70 * 71 * New codes are not necessarily assigned every time an old 72 * code is output by the compressor. This is because a packet 73 * end forces a code to be emitted, but does not imply that a 74 * new sequence has been seen. 75 * 76 * The compression ratio is checked at the first end of a packet 77 * after the appropriate gap. Besides simplifying and speeding 78 * things up, this makes it more likely that the transmitter 79 * and receiver will agree when the dictionary is cleared when 80 * compression is not going well. 81 */ 82 83 /* 84 * A dictionary for doing BSD compress. 85 */ 86 struct bsd_db { 87 int totlen; /* length of this structure */ 88 u_int hsize; /* size of the hash table */ 89 u_char hshift; /* used in hash function */ 90 u_char n_bits; /* current bits/code */ 91 u_char maxbits; 92 u_char debug; 93 u_char unit; 94 u_int16_t seqno; /* sequence # of next packet */ 95 u_int hdrlen; /* header length to preallocate */ 96 u_int mru; 97 u_int maxmaxcode; /* largest valid code */ 98 u_int max_ent; /* largest code in use */ 99 u_int in_count; /* uncompressed bytes, aged */ 100 u_int bytes_out; /* compressed bytes, aged */ 101 u_int ratio; /* recent compression ratio */ 102 u_int checkpoint; /* when to next check the ratio */ 103 u_int clear_count; /* times dictionary cleared */ 104 u_int incomp_count; /* incompressible packets */ 105 u_int incomp_bytes; /* incompressible bytes */ 106 u_int uncomp_count; /* uncompressed packets */ 107 u_int uncomp_bytes; /* uncompressed bytes */ 108 u_int comp_count; /* compressed packets */ 109 u_int comp_bytes; /* compressed bytes */ 110 u_int16_t *lens; /* array of lengths of codes */ 111 struct bsd_dict { 112 union { /* hash value */ 113 u_int32_t fcode; 114 struct { 115 #if BYTE_ORDER == LITTLE_ENDIAN 116 u_int16_t prefix; /* preceding code */ 117 u_char suffix; /* last character of new code */ 118 u_char pad; 119 #else 120 u_char pad; 121 u_char suffix; /* last character of new code */ 122 u_int16_t prefix; /* preceding code */ 123 #endif 124 } hs; 125 } f; 126 u_int16_t codem1; /* output of hash table -1 */ 127 u_int16_t cptr; /* map code to hash table entry */ 128 } dict[1]; 129 }; 130 131 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 132 #define BSD_INIT_BITS BSD_MIN_BITS 133 134 static void *bsd_comp_alloc __P((u_char *options, int opt_len)); 135 static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); 136 static void bsd_free __P((void *state)); 137 static int bsd_comp_init __P((void *state, u_char *options, int opt_len, 138 int unit, int hdrlen, int debug)); 139 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, 140 int unit, int hdrlen, int mru, int debug)); 141 static int bsd_compress __P((void *state, struct mbuf **mret, 142 struct mbuf *mp, int slen, int maxolen)); 143 static void bsd_incomp __P((void *state, struct mbuf *dmsg)); 144 static int bsd_decompress __P((void *state, struct mbuf *cmp, 145 struct mbuf **dmpp)); 146 static void bsd_reset __P((void *state)); 147 static void bsd_comp_stats __P((void *state, struct compstat *stats)); 148 149 /* 150 * Procedures exported to if_ppp.c. 151 */ 152 struct compressor ppp_bsd_compress = { 153 CI_BSD_COMPRESS, /* compress_proto */ 154 bsd_comp_alloc, /* comp_alloc */ 155 bsd_free, /* comp_free */ 156 bsd_comp_init, /* comp_init */ 157 bsd_reset, /* comp_reset */ 158 bsd_compress, /* compress */ 159 bsd_comp_stats, /* comp_stat */ 160 bsd_decomp_alloc, /* decomp_alloc */ 161 bsd_free, /* decomp_free */ 162 bsd_decomp_init, /* decomp_init */ 163 bsd_reset, /* decomp_reset */ 164 bsd_decompress, /* decompress */ 165 bsd_incomp, /* incomp */ 166 bsd_comp_stats, /* decomp_stat */ 167 }; 168 169 /* 170 * the next two codes should not be changed lightly, as they must not 171 * lie within the contiguous general code space. 172 */ 173 #define CLEAR 256 /* table clear output code */ 174 #define FIRST 257 /* first free entry */ 175 #define LAST 255 176 177 #define MAXCODE(b) ((1 << (b)) - 1) 178 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 179 180 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 181 ^ (u_int32_t)(prefix)) 182 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 183 + (u_int32_t)(prefix)) 184 185 #define CHECK_GAP 10000 /* Ratio check interval */ 186 187 #define RATIO_SCALE_LOG 8 188 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 189 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 190 191 static void bsd_clear __P((struct bsd_db *)); 192 static int bsd_check __P((struct bsd_db *)); 193 static void *bsd_alloc __P((u_char *, int, int)); 194 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int, 195 int, int)); 196 197 /* 198 * clear the dictionary 199 */ 200 static void 201 bsd_clear(db) 202 struct bsd_db *db; 203 { 204 db->clear_count++; 205 db->max_ent = FIRST-1; 206 db->n_bits = BSD_INIT_BITS; 207 db->ratio = 0; 208 db->bytes_out = 0; 209 db->in_count = 0; 210 db->checkpoint = CHECK_GAP; 211 } 212 213 /* 214 * If the dictionary is full, then see if it is time to reset it. 215 * 216 * Compute the compression ratio using fixed-point arithmetic 217 * with 8 fractional bits. 218 * 219 * Since we have an infinite stream instead of a single file, 220 * watch only the local compression ratio. 221 * 222 * Since both peers must reset the dictionary at the same time even in 223 * the absence of CLEAR codes (while packets are incompressible), they 224 * must compute the same ratio. 225 */ 226 static int /* 1=output CLEAR */ 227 bsd_check(db) 228 struct bsd_db *db; 229 { 230 u_int new_ratio; 231 232 if (db->in_count >= db->checkpoint) { 233 /* age the ratio by limiting the size of the counts */ 234 if (db->in_count >= RATIO_MAX 235 || db->bytes_out >= RATIO_MAX) { 236 db->in_count -= db->in_count/4; 237 db->bytes_out -= db->bytes_out/4; 238 } 239 240 db->checkpoint = db->in_count + CHECK_GAP; 241 242 if (db->max_ent >= db->maxmaxcode) { 243 /* Reset the dictionary only if the ratio is worse, 244 * or if it looks as if it has been poisoned 245 * by incompressible data. 246 * 247 * This does not overflow, because 248 * db->in_count <= RATIO_MAX. 249 */ 250 new_ratio = db->in_count << RATIO_SCALE_LOG; 251 if (db->bytes_out != 0) 252 new_ratio /= db->bytes_out; 253 254 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 255 bsd_clear(db); 256 return 1; 257 } 258 db->ratio = new_ratio; 259 } 260 } 261 return 0; 262 } 263 264 /* 265 * Return statistics. 266 */ 267 static void 268 bsd_comp_stats(state, stats) 269 void *state; 270 struct compstat *stats; 271 { 272 struct bsd_db *db = (struct bsd_db *) state; 273 u_int out; 274 275 stats->unc_bytes = db->uncomp_bytes; 276 stats->unc_packets = db->uncomp_count; 277 stats->comp_bytes = db->comp_bytes; 278 stats->comp_packets = db->comp_count; 279 stats->inc_bytes = db->incomp_bytes; 280 stats->inc_packets = db->incomp_count; 281 stats->ratio = db->in_count; 282 out = db->bytes_out; 283 if (stats->ratio <= 0x7fffff) 284 stats->ratio <<= 8; 285 else 286 out >>= 8; 287 if (out != 0) 288 stats->ratio /= out; 289 } 290 291 /* 292 * Reset state, as on a CCP ResetReq. 293 */ 294 static void 295 bsd_reset(state) 296 void *state; 297 { 298 struct bsd_db *db = (struct bsd_db *) state; 299 300 db->seqno = 0; 301 bsd_clear(db); 302 db->clear_count = 0; 303 } 304 305 /* 306 * Allocate space for a (de) compressor. 307 */ 308 static void * 309 bsd_alloc(options, opt_len, decomp) 310 u_char *options; 311 int opt_len, decomp; 312 { 313 int bits; 314 u_int newlen, hsize, hshift, maxmaxcode; 315 struct bsd_db *db; 316 317 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 318 || options[1] != CILEN_BSD_COMPRESS 319 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 320 return NULL; 321 bits = BSD_NBITS(options[2]); 322 switch (bits) { 323 case 9: /* needs 82152 for both directions */ 324 case 10: /* needs 84144 */ 325 case 11: /* needs 88240 */ 326 case 12: /* needs 96432 */ 327 hsize = 5003; 328 hshift = 4; 329 break; 330 case 13: /* needs 176784 */ 331 hsize = 9001; 332 hshift = 5; 333 break; 334 case 14: /* needs 353744 */ 335 hsize = 18013; 336 hshift = 6; 337 break; 338 case 15: /* needs 691440 */ 339 hsize = 35023; 340 hshift = 7; 341 break; 342 case 16: /* needs 1366160--far too much, */ 343 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 344 /* hshift = 8; */ /* in struct bsd_db */ 345 /* break; */ 346 default: 347 return NULL; 348 } 349 350 maxmaxcode = MAXCODE(bits); 351 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 352 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT); 353 if (!db) 354 return NULL; 355 bzero(db, sizeof(*db) - sizeof(db->dict)); 356 357 if (!decomp) { 358 db->lens = NULL; 359 } else { 360 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]), 361 M_DEVBUF, M_NOWAIT); 362 if (!db->lens) { 363 FREE(db, M_DEVBUF); 364 return NULL; 365 } 366 } 367 368 db->totlen = newlen; 369 db->hsize = hsize; 370 db->hshift = hshift; 371 db->maxmaxcode = maxmaxcode; 372 db->maxbits = bits; 373 374 return (void *) db; 375 } 376 377 static void 378 bsd_free(state) 379 void *state; 380 { 381 struct bsd_db *db = (struct bsd_db *) state; 382 383 if (db->lens) 384 FREE(db->lens, M_DEVBUF); 385 FREE(db, M_DEVBUF); 386 } 387 388 static void * 389 bsd_comp_alloc(options, opt_len) 390 u_char *options; 391 int opt_len; 392 { 393 return bsd_alloc(options, opt_len, 0); 394 } 395 396 static void * 397 bsd_decomp_alloc(options, opt_len) 398 u_char *options; 399 int opt_len; 400 { 401 return bsd_alloc(options, opt_len, 1); 402 } 403 404 /* 405 * Initialize the database. 406 */ 407 static int 408 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 409 struct bsd_db *db; 410 u_char *options; 411 int opt_len, unit, hdrlen, mru, debug, decomp; 412 { 413 int i; 414 415 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 416 || options[1] != CILEN_BSD_COMPRESS 417 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 418 || BSD_NBITS(options[2]) != db->maxbits 419 || (decomp && db->lens == NULL)) 420 return 0; 421 422 if (decomp) { 423 i = LAST+1; 424 while (i != 0) 425 db->lens[--i] = 1; 426 } 427 i = db->hsize; 428 while (i != 0) { 429 db->dict[--i].codem1 = BADCODEM1; 430 db->dict[i].cptr = 0; 431 } 432 433 db->unit = unit; 434 db->hdrlen = hdrlen; 435 db->mru = mru; 436 #ifndef DEBUG 437 if (debug) 438 #endif 439 db->debug = 1; 440 441 bsd_reset(db); 442 443 return 1; 444 } 445 446 static int 447 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 448 void *state; 449 u_char *options; 450 int opt_len, unit, hdrlen, debug; 451 { 452 return bsd_init((struct bsd_db *) state, options, opt_len, 453 unit, hdrlen, 0, debug, 0); 454 } 455 456 static int 457 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 458 void *state; 459 u_char *options; 460 int opt_len, unit, hdrlen, mru, debug; 461 { 462 return bsd_init((struct bsd_db *) state, options, opt_len, 463 unit, hdrlen, mru, debug, 1); 464 } 465 466 467 /* 468 * compress a packet 469 * One change from the BSD compress command is that when the 470 * code size expands, we do not output a bunch of padding. 471 */ 472 int /* new slen */ 473 bsd_compress(state, mret, mp, slen, maxolen) 474 void *state; 475 struct mbuf **mret; /* return compressed mbuf chain here */ 476 struct mbuf *mp; /* from here */ 477 int slen; /* uncompressed length */ 478 int maxolen; /* max compressed length */ 479 { 480 struct bsd_db *db = (struct bsd_db *) state; 481 int hshift = db->hshift; 482 u_int max_ent = db->max_ent; 483 u_int n_bits = db->n_bits; 484 u_int bitno = 32; 485 u_int32_t accm = 0, fcode; 486 struct bsd_dict *dictp; 487 u_char c; 488 int hval, disp, ent, ilen; 489 u_char *rptr, *wptr; 490 u_char *cp_end; 491 int olen; 492 struct mbuf *m; 493 494 #define PUTBYTE(v) { \ 495 ++olen; \ 496 if (wptr) { \ 497 *wptr++ = (v); \ 498 if (wptr >= cp_end) { \ 499 m->m_len = wptr - mtod(m, u_char *); \ 500 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 501 m = m->m_next; \ 502 if (m) { \ 503 m->m_len = 0; \ 504 if (maxolen - olen > MLEN) \ 505 MCLGET(m, M_DONTWAIT); \ 506 wptr = mtod(m, u_char *); \ 507 cp_end = wptr + M_TRAILINGSPACE(m); \ 508 } else \ 509 wptr = NULL; \ 510 } \ 511 } \ 512 } 513 514 #define OUTPUT(ent) { \ 515 bitno -= n_bits; \ 516 accm |= ((ent) << bitno); \ 517 do { \ 518 PUTBYTE(accm >> 24); \ 519 accm <<= 8; \ 520 bitno += 8; \ 521 } while (bitno <= 24); \ 522 } 523 524 /* 525 * If the protocol is not in the range we're interested in, 526 * just return without compressing the packet. If it is, 527 * the protocol becomes the first byte to compress. 528 */ 529 rptr = mtod(mp, u_char *); 530 ent = PPP_PROTOCOL(rptr); 531 if (ent < 0x21 || ent > 0xf9) { 532 *mret = NULL; 533 return slen; 534 } 535 536 /* Don't generate compressed packets which are larger than 537 the uncompressed packet. */ 538 if (maxolen > slen) 539 maxolen = slen; 540 541 /* Allocate one mbuf to start with. */ 542 MGET(m, M_DONTWAIT, MT_DATA); 543 *mret = m; 544 if (m != NULL) { 545 m->m_len = 0; 546 if (maxolen + db->hdrlen > MLEN) 547 MCLGET(m, M_DONTWAIT); 548 m->m_data += db->hdrlen; 549 wptr = mtod(m, u_char *); 550 cp_end = wptr + M_TRAILINGSPACE(m); 551 } else 552 wptr = cp_end = NULL; 553 554 /* 555 * Copy the PPP header over, changing the protocol, 556 * and install the 2-byte packet sequence number. 557 */ 558 if (wptr) { 559 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 560 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 561 *wptr++ = 0; /* change the protocol */ 562 *wptr++ = PPP_COMP; 563 *wptr++ = db->seqno >> 8; 564 *wptr++ = db->seqno; 565 } 566 ++db->seqno; 567 568 olen = 0; 569 rptr += PPP_HDRLEN; 570 slen = mp->m_len - PPP_HDRLEN; 571 ilen = slen + 1; 572 for (;;) { 573 if (slen <= 0) { 574 mp = mp->m_next; 575 if (!mp) 576 break; 577 rptr = mtod(mp, u_char *); 578 slen = mp->m_len; 579 if (!slen) 580 continue; /* handle 0-length buffers */ 581 ilen += slen; 582 } 583 584 slen--; 585 c = *rptr++; 586 fcode = BSD_KEY(ent, c); 587 hval = BSD_HASH(ent, c, hshift); 588 dictp = &db->dict[hval]; 589 590 /* Validate and then check the entry. */ 591 if (dictp->codem1 >= max_ent) 592 goto nomatch; 593 if (dictp->f.fcode == fcode) { 594 ent = dictp->codem1+1; 595 continue; /* found (prefix,suffix) */ 596 } 597 598 /* continue probing until a match or invalid entry */ 599 disp = (hval == 0) ? 1 : hval; 600 do { 601 hval += disp; 602 if (hval >= db->hsize) 603 hval -= db->hsize; 604 dictp = &db->dict[hval]; 605 if (dictp->codem1 >= max_ent) 606 goto nomatch; 607 } while (dictp->f.fcode != fcode); 608 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 609 continue; 610 611 nomatch: 612 OUTPUT(ent); /* output the prefix */ 613 614 /* code -> hashtable */ 615 if (max_ent < db->maxmaxcode) { 616 struct bsd_dict *dictp2; 617 /* expand code size if needed */ 618 if (max_ent >= MAXCODE(n_bits)) 619 db->n_bits = ++n_bits; 620 621 /* Invalidate old hash table entry using 622 * this code, and then take it over. 623 */ 624 dictp2 = &db->dict[max_ent+1]; 625 if (db->dict[dictp2->cptr].codem1 == max_ent) 626 db->dict[dictp2->cptr].codem1 = BADCODEM1; 627 dictp2->cptr = hval; 628 dictp->codem1 = max_ent; 629 dictp->f.fcode = fcode; 630 631 db->max_ent = ++max_ent; 632 } 633 ent = c; 634 } 635 636 OUTPUT(ent); /* output the last code */ 637 db->bytes_out += olen; 638 db->in_count += ilen; 639 if (bitno < 32) 640 ++db->bytes_out; /* count complete bytes */ 641 642 if (bsd_check(db)) 643 OUTPUT(CLEAR); /* do not count the CLEAR */ 644 645 /* 646 * Pad dribble bits of last code with ones. 647 * Do not emit a completely useless byte of ones. 648 */ 649 if (bitno != 32) 650 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 651 652 if (m != NULL) { 653 m->m_len = wptr - mtod(m, u_char *); 654 m->m_next = NULL; 655 } 656 657 /* 658 * Increase code size if we would have without the packet 659 * boundary and as the decompressor will. 660 */ 661 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 662 db->n_bits++; 663 664 db->uncomp_bytes += ilen; 665 ++db->uncomp_count; 666 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 667 /* throw away the compressed stuff if it is longer than uncompressed */ 668 if (*mret != NULL) { 669 m_freem(*mret); 670 *mret = NULL; 671 } 672 ++db->incomp_count; 673 db->incomp_bytes += ilen; 674 } else { 675 ++db->comp_count; 676 db->comp_bytes += olen + BSD_OVHD; 677 } 678 679 return olen + PPP_HDRLEN + BSD_OVHD; 680 #undef OUTPUT 681 #undef PUTBYTE 682 } 683 684 685 /* 686 * Update the "BSD Compress" dictionary on the receiver for 687 * incompressible data by pretending to compress the incoming data. 688 */ 689 static void 690 bsd_incomp(state, dmsg) 691 void *state; 692 struct mbuf *dmsg; 693 { 694 struct bsd_db *db = (struct bsd_db *) state; 695 u_int hshift = db->hshift; 696 u_int max_ent = db->max_ent; 697 u_int n_bits = db->n_bits; 698 struct bsd_dict *dictp; 699 u_int32_t fcode; 700 u_char c; 701 u_int32_t hval, disp; 702 int slen, ilen; 703 u_int bitno = 7; 704 u_char *rptr; 705 u_int ent; 706 707 /* 708 * If the protocol is not in the range we're interested in, 709 * just return without looking at the packet. If it is, 710 * the protocol becomes the first byte to "compress". 711 */ 712 rptr = mtod(dmsg, u_char *); 713 ent = PPP_PROTOCOL(rptr); 714 if (ent < 0x21 || ent > 0xf9) 715 return; 716 717 db->seqno++; 718 ilen = 1; /* count the protocol as 1 byte */ 719 rptr += PPP_HDRLEN; 720 slen = dmsg->m_len - PPP_HDRLEN; 721 for (;;) { 722 if (slen <= 0) { 723 dmsg = dmsg->m_next; 724 if (!dmsg) 725 break; 726 rptr = mtod(dmsg, u_char *); 727 slen = dmsg->m_len; 728 continue; 729 } 730 ilen += slen; 731 732 do { 733 c = *rptr++; 734 fcode = BSD_KEY(ent, c); 735 hval = BSD_HASH(ent, c, hshift); 736 dictp = &db->dict[hval]; 737 738 /* validate and then check the entry */ 739 if (dictp->codem1 >= max_ent) 740 goto nomatch; 741 if (dictp->f.fcode == fcode) { 742 ent = dictp->codem1+1; 743 continue; /* found (prefix,suffix) */ 744 } 745 746 /* continue probing until a match or invalid entry */ 747 disp = (hval == 0) ? 1 : hval; 748 do { 749 hval += disp; 750 if (hval >= db->hsize) 751 hval -= db->hsize; 752 dictp = &db->dict[hval]; 753 if (dictp->codem1 >= max_ent) 754 goto nomatch; 755 } while (dictp->f.fcode != fcode); 756 ent = dictp->codem1+1; 757 continue; /* finally found (prefix,suffix) */ 758 759 nomatch: /* output (count) the prefix */ 760 bitno += n_bits; 761 762 /* code -> hashtable */ 763 if (max_ent < db->maxmaxcode) { 764 struct bsd_dict *dictp2; 765 /* expand code size if needed */ 766 if (max_ent >= MAXCODE(n_bits)) 767 db->n_bits = ++n_bits; 768 769 /* Invalidate previous hash table entry 770 * assigned this code, and then take it over. 771 */ 772 dictp2 = &db->dict[max_ent+1]; 773 if (db->dict[dictp2->cptr].codem1 == max_ent) 774 db->dict[dictp2->cptr].codem1 = BADCODEM1; 775 dictp2->cptr = hval; 776 dictp->codem1 = max_ent; 777 dictp->f.fcode = fcode; 778 779 db->max_ent = ++max_ent; 780 db->lens[max_ent] = db->lens[ent]+1; 781 } 782 ent = c; 783 } while (--slen != 0); 784 } 785 bitno += n_bits; /* output (count) the last code */ 786 db->bytes_out += bitno/8; 787 db->in_count += ilen; 788 (void)bsd_check(db); 789 790 ++db->incomp_count; 791 db->incomp_bytes += ilen; 792 ++db->uncomp_count; 793 db->uncomp_bytes += ilen; 794 795 /* Increase code size if we would have without the packet 796 * boundary and as the decompressor will. 797 */ 798 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 799 db->n_bits++; 800 } 801 802 803 /* 804 * Decompress "BSD Compress". 805 * 806 * Because of patent problems, we return DECOMP_ERROR for errors 807 * found by inspecting the input data and for system problems, but 808 * DECOMP_FATALERROR for any errors which could possibly be said to 809 * be being detected "after" decompression. For DECOMP_ERROR, 810 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 811 * infringing a patent of Motorola's if we do, so we take CCP down 812 * instead. 813 * 814 * Given that the frame has the correct sequence number and a good FCS, 815 * errors such as invalid codes in the input most likely indicate a 816 * bug, so we return DECOMP_FATALERROR for them in order to turn off 817 * compression, even though they are detected by inspecting the input. 818 */ 819 int 820 bsd_decompress(state, cmp, dmpp) 821 void *state; 822 struct mbuf *cmp, **dmpp; 823 { 824 struct bsd_db *db = (struct bsd_db *) state; 825 u_int max_ent = db->max_ent; 826 u_int32_t accm = 0; 827 u_int bitno = 32; /* 1st valid bit in accm */ 828 u_int n_bits = db->n_bits; 829 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 830 struct bsd_dict *dictp; 831 int explen, i, seq, len; 832 u_int incode, oldcode, finchar; 833 u_char *p, *rptr, *wptr; 834 struct mbuf *m, *dmp, *mret; 835 int adrs, ctrl, ilen; 836 int space, codelen, extra; 837 838 /* 839 * Save the address/control from the PPP header 840 * and then get the sequence number. 841 */ 842 *dmpp = NULL; 843 rptr = mtod(cmp, u_char *); 844 adrs = PPP_ADDRESS(rptr); 845 ctrl = PPP_CONTROL(rptr); 846 rptr += PPP_HDRLEN; 847 len = cmp->m_len - PPP_HDRLEN; 848 seq = 0; 849 for (i = 0; i < 2; ++i) { 850 while (len <= 0) { 851 cmp = cmp->m_next; 852 if (cmp == NULL) 853 return DECOMP_ERROR; 854 rptr = mtod(cmp, u_char *); 855 len = cmp->m_len; 856 } 857 seq = (seq << 8) + *rptr++; 858 --len; 859 } 860 861 /* 862 * Check the sequence number and give up if it differs from 863 * the value we're expecting. 864 */ 865 if (seq != db->seqno) { 866 if (db->debug) 867 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 868 db->unit, seq, db->seqno - 1); 869 return DECOMP_ERROR; 870 } 871 ++db->seqno; 872 873 /* 874 * Allocate one mbuf to start with. 875 */ 876 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 877 if (dmp == NULL) 878 return DECOMP_ERROR; 879 mret = dmp; 880 dmp->m_len = 0; 881 dmp->m_next = NULL; 882 MCLGET(dmp, M_DONTWAIT); 883 dmp->m_data += db->hdrlen; 884 wptr = mtod(dmp, u_char *); 885 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 886 887 /* 888 * Fill in the ppp header, but not the last byte of the protocol 889 * (that comes from the decompressed data). 890 */ 891 wptr[0] = adrs; 892 wptr[1] = ctrl; 893 wptr[2] = 0; 894 wptr += PPP_HDRLEN - 1; 895 896 ilen = len; 897 oldcode = CLEAR; 898 explen = 0; 899 for (;;) { 900 if (len == 0) { 901 cmp = cmp->m_next; 902 if (!cmp) /* quit at end of message */ 903 break; 904 rptr = mtod(cmp, u_char *); 905 len = cmp->m_len; 906 ilen += len; 907 continue; /* handle 0-length buffers */ 908 } 909 910 /* 911 * Accumulate bytes until we have a complete code. 912 * Then get the next code, relying on the 32-bit, 913 * unsigned accm to mask the result. 914 */ 915 bitno -= 8; 916 accm |= *rptr++ << bitno; 917 --len; 918 if (tgtbitno < bitno) 919 continue; 920 incode = accm >> tgtbitno; 921 accm <<= n_bits; 922 bitno += n_bits; 923 924 if (incode == CLEAR) { 925 /* 926 * The dictionary must only be cleared at 927 * the end of a packet. But there could be an 928 * empty mbuf at the end. 929 */ 930 if (len > 0 || cmp->m_next != NULL) { 931 while ((cmp = cmp->m_next) != NULL) 932 len += cmp->m_len; 933 if (len > 0) { 934 m_freem(mret); 935 if (db->debug) 936 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 937 return DECOMP_FATALERROR; /* probably a bug */ 938 } 939 } 940 bsd_clear(db); 941 explen = ilen = 0; 942 break; 943 } 944 945 if (incode > max_ent + 2 || incode > db->maxmaxcode 946 || (incode > max_ent && oldcode == CLEAR)) { 947 m_freem(mret); 948 if (db->debug) { 949 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 950 db->unit, incode, oldcode); 951 printf("max_ent=0x%x explen=%d seqno=%d\n", 952 max_ent, explen, db->seqno); 953 } 954 return DECOMP_FATALERROR; /* probably a bug */ 955 } 956 957 /* Special case for KwKwK string. */ 958 if (incode > max_ent) { 959 finchar = oldcode; 960 extra = 1; 961 } else { 962 finchar = incode; 963 extra = 0; 964 } 965 966 codelen = db->lens[finchar]; 967 explen += codelen + extra; 968 if (explen > db->mru + 1) { 969 m_freem(mret); 970 if (db->debug) { 971 printf("bsd_decomp%d: ran out of mru\n", db->unit); 972 #ifdef DEBUG 973 while ((cmp = cmp->m_next) != NULL) 974 len += cmp->m_len; 975 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 976 len, finchar, codelen, explen); 977 #endif 978 } 979 return DECOMP_FATALERROR; 980 } 981 982 /* 983 * For simplicity, the decoded characters go in a single mbuf, 984 * so we allocate a single extra cluster mbuf if necessary. 985 */ 986 if ((space -= codelen + extra) < 0) { 987 dmp->m_len = wptr - mtod(dmp, u_char *); 988 MGET(m, M_DONTWAIT, MT_DATA); 989 if (m == NULL) { 990 m_freem(mret); 991 return DECOMP_ERROR; 992 } 993 m->m_len = 0; 994 m->m_next = NULL; 995 dmp->m_next = m; 996 MCLGET(m, M_DONTWAIT); 997 space = M_TRAILINGSPACE(m) - (codelen + extra); 998 if (space < 0) { 999 /* now that's what I call *compression*. */ 1000 m_freem(mret); 1001 return DECOMP_ERROR; 1002 } 1003 dmp = m; 1004 wptr = mtod(dmp, u_char *); 1005 } 1006 1007 /* 1008 * Decode this code and install it in the decompressed buffer. 1009 */ 1010 p = (wptr += codelen); 1011 while (finchar > LAST) { 1012 dictp = &db->dict[db->dict[finchar].cptr]; 1013 #ifdef DEBUG 1014 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1015 goto bad; 1016 #endif 1017 *--p = dictp->f.hs.suffix; 1018 finchar = dictp->f.hs.prefix; 1019 } 1020 *--p = finchar; 1021 1022 #ifdef DEBUG 1023 if (--codelen != 0) 1024 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1025 db->unit, codelen, incode, max_ent); 1026 #endif 1027 1028 if (extra) /* the KwKwK case again */ 1029 *wptr++ = finchar; 1030 1031 /* 1032 * If not first code in a packet, and 1033 * if not out of code space, then allocate a new code. 1034 * 1035 * Keep the hash table correct so it can be used 1036 * with uncompressed packets. 1037 */ 1038 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1039 struct bsd_dict *dictp2; 1040 u_int32_t fcode; 1041 u_int32_t hval, disp; 1042 1043 fcode = BSD_KEY(oldcode,finchar); 1044 hval = BSD_HASH(oldcode,finchar,db->hshift); 1045 dictp = &db->dict[hval]; 1046 1047 /* look for a free hash table entry */ 1048 if (dictp->codem1 < max_ent) { 1049 disp = (hval == 0) ? 1 : hval; 1050 do { 1051 hval += disp; 1052 if (hval >= db->hsize) 1053 hval -= db->hsize; 1054 dictp = &db->dict[hval]; 1055 } while (dictp->codem1 < max_ent); 1056 } 1057 1058 /* 1059 * Invalidate previous hash table entry 1060 * assigned this code, and then take it over 1061 */ 1062 dictp2 = &db->dict[max_ent+1]; 1063 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1064 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1065 } 1066 dictp2->cptr = hval; 1067 dictp->codem1 = max_ent; 1068 dictp->f.fcode = fcode; 1069 1070 db->max_ent = ++max_ent; 1071 db->lens[max_ent] = db->lens[oldcode]+1; 1072 1073 /* Expand code size if needed. */ 1074 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1075 db->n_bits = ++n_bits; 1076 tgtbitno = 32-n_bits; 1077 } 1078 } 1079 oldcode = incode; 1080 } 1081 dmp->m_len = wptr - mtod(dmp, u_char *); 1082 1083 /* 1084 * Keep the checkpoint right so that incompressible packets 1085 * clear the dictionary at the right times. 1086 */ 1087 db->bytes_out += ilen; 1088 db->in_count += explen; 1089 if (bsd_check(db) && db->debug) { 1090 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1091 db->unit); 1092 } 1093 1094 ++db->comp_count; 1095 db->comp_bytes += ilen + BSD_OVHD; 1096 ++db->uncomp_count; 1097 db->uncomp_bytes += explen; 1098 1099 *dmpp = mret; 1100 return DECOMP_OK; 1101 1102 #ifdef DEBUG 1103 bad: 1104 if (codelen <= 0) { 1105 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1106 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1107 incode, finchar, db->dict[finchar].cptr, max_ent); 1108 } else if (dictp->codem1 != finchar-1) { 1109 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1110 db->unit, incode, finchar); 1111 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1112 db->dict[finchar].cptr, dictp->codem1); 1113 } 1114 m_freem(mret); 1115 return DECOMP_FATALERROR; 1116 #endif /* DEBUG */ 1117 } 1118 #endif /* DO_BSD_COMPRESS */ 1119