1 /* $NetBSD: bsd-comp.c,v 1.1 1995/07/04 06:28:17 paulus Exp $ */ 2 3 /* Because this code is derived from the 4.3BSD compress source: 4 * 5 * 6 * Copyright (c) 1985, 1986 The Regents of the University of California. 7 * All rights reserved. 8 * 9 * This code is derived from software contributed to Berkeley by 10 * James A. Woods, derived from original work by Spencer Thomas 11 * and Joseph Orost. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 */ 41 42 /* 43 * This version is for use with mbufs on BSD-derived systems. 44 * 45 * $Id: bsd-comp.c,v 1.1 1995/07/04 06:28:17 paulus Exp $ 46 */ 47 48 #include <sys/param.h> 49 #include <sys/types.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 /* 192 * clear the dictionary 193 */ 194 static void 195 bsd_clear(db) 196 struct bsd_db *db; 197 { 198 db->clear_count++; 199 db->max_ent = FIRST-1; 200 db->n_bits = BSD_INIT_BITS; 201 db->ratio = 0; 202 db->bytes_out = 0; 203 db->in_count = 0; 204 db->incomp_count = 0; 205 db->checkpoint = CHECK_GAP; 206 } 207 208 /* 209 * If the dictionary is full, then see if it is time to reset it. 210 * 211 * Compute the compression ratio using fixed-point arithmetic 212 * with 8 fractional bits. 213 * 214 * Since we have an infinite stream instead of a single file, 215 * watch only the local compression ratio. 216 * 217 * Since both peers must reset the dictionary at the same time even in 218 * the absence of CLEAR codes (while packets are incompressible), they 219 * must compute the same ratio. 220 */ 221 static int /* 1=output CLEAR */ 222 bsd_check(db) 223 struct bsd_db *db; 224 { 225 u_int new_ratio; 226 227 if (db->in_count >= db->checkpoint) { 228 /* age the ratio by limiting the size of the counts */ 229 if (db->in_count >= RATIO_MAX 230 || db->bytes_out >= RATIO_MAX) { 231 db->in_count -= db->in_count/4; 232 db->bytes_out -= db->bytes_out/4; 233 } 234 235 db->checkpoint = db->in_count + CHECK_GAP; 236 237 if (db->max_ent >= db->maxmaxcode) { 238 /* Reset the dictionary only if the ratio is worse, 239 * or if it looks as if it has been poisoned 240 * by incompressible data. 241 * 242 * This does not overflow, because 243 * db->in_count <= RATIO_MAX. 244 */ 245 new_ratio = db->in_count << RATIO_SCALE_LOG; 246 if (db->bytes_out != 0) 247 new_ratio /= db->bytes_out; 248 249 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 250 bsd_clear(db); 251 return 1; 252 } 253 db->ratio = new_ratio; 254 } 255 } 256 return 0; 257 } 258 259 /* 260 * Return statistics. 261 */ 262 static void 263 bsd_comp_stats(state, stats) 264 void *state; 265 struct compstat *stats; 266 { 267 struct bsd_db *db = (struct bsd_db *) state; 268 u_int out; 269 270 stats->unc_bytes = db->uncomp_bytes; 271 stats->unc_packets = db->uncomp_count; 272 stats->comp_bytes = db->comp_bytes; 273 stats->comp_packets = db->comp_count; 274 stats->inc_bytes = db->incomp_bytes; 275 stats->inc_packets = db->incomp_count; 276 stats->ratio = db->in_count; 277 out = db->bytes_out; 278 if (stats->ratio <= 0x7fffff) 279 stats->ratio <<= 8; 280 else 281 out >>= 8; 282 if (out != 0) 283 stats->ratio /= out; 284 } 285 286 /* 287 * Reset state, as on a CCP ResetReq. 288 */ 289 static void 290 bsd_reset(state) 291 void *state; 292 { 293 struct bsd_db *db = (struct bsd_db *) state; 294 295 db->seqno = 0; 296 bsd_clear(db); 297 db->clear_count = 0; 298 } 299 300 /* 301 * Allocate space for a (de) compressor. 302 */ 303 static void * 304 bsd_alloc(options, opt_len, decomp) 305 u_char *options; 306 int opt_len, decomp; 307 { 308 int bits; 309 u_int newlen, hsize, hshift, maxmaxcode; 310 struct bsd_db *db; 311 312 if (opt_len != CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 313 || options[1] != CILEN_BSD_COMPRESS 314 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 315 return NULL; 316 bits = BSD_NBITS(options[2]); 317 switch (bits) { 318 case 9: /* needs 82152 for both directions */ 319 case 10: /* needs 84144 */ 320 case 11: /* needs 88240 */ 321 case 12: /* needs 96432 */ 322 hsize = 5003; 323 hshift = 4; 324 break; 325 case 13: /* needs 176784 */ 326 hsize = 9001; 327 hshift = 5; 328 break; 329 case 14: /* needs 353744 */ 330 hsize = 18013; 331 hshift = 6; 332 break; 333 case 15: /* needs 691440 */ 334 hsize = 35023; 335 hshift = 7; 336 break; 337 case 16: /* needs 1366160--far too much, */ 338 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 339 /* hshift = 8; */ /* in struct bsd_db */ 340 /* break; */ 341 default: 342 return NULL; 343 } 344 345 maxmaxcode = MAXCODE(bits); 346 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 347 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT); 348 if (!db) 349 return NULL; 350 bzero(db, sizeof(*db) - sizeof(db->dict)); 351 352 if (!decomp) { 353 db->lens = NULL; 354 } else { 355 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]), 356 M_DEVBUF, M_NOWAIT); 357 if (!db->lens) { 358 FREE(db, M_DEVBUF); 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); 380 FREE(db, M_DEVBUF); 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 struct mbuf *np; 485 u_char *rptr, *wptr; 486 u_char *cp_end; 487 int olen; 488 struct mbuf *m, **mnp; 489 490 #define PUTBYTE(v) { \ 491 ++olen; \ 492 if (wptr) { \ 493 *wptr++ = (v); \ 494 if (wptr >= cp_end) { \ 495 m->m_len = wptr - mtod(m, u_char *); \ 496 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 497 m = m->m_next; \ 498 if (m) { \ 499 m->m_len = 0; \ 500 if (maxolen - olen > MLEN) \ 501 MCLGET(m, M_DONTWAIT); \ 502 wptr = mtod(m, u_char *); \ 503 cp_end = wptr + M_TRAILINGSPACE(m); \ 504 } else \ 505 wptr = NULL; \ 506 } \ 507 } \ 508 } 509 510 #define OUTPUT(ent) { \ 511 bitno -= n_bits; \ 512 accm |= ((ent) << bitno); \ 513 do { \ 514 PUTBYTE(accm >> 24); \ 515 accm <<= 8; \ 516 bitno += 8; \ 517 } while (bitno <= 24); \ 518 } 519 520 /* 521 * If the protocol is not in the range we're interested in, 522 * just return without compressing the packet. If it is, 523 * the protocol becomes the first byte to compress. 524 */ 525 rptr = mtod(mp, u_char *); 526 ent = PPP_PROTOCOL(rptr); 527 if (ent < 0x21 || ent > 0xf9) { 528 *mret = NULL; 529 return slen; 530 } 531 532 /* Don't generate compressed packets which are larger than 533 the uncompressed packet. */ 534 if (maxolen > slen) 535 maxolen = slen; 536 537 /* Allocate one mbuf to start with. */ 538 MGET(m, M_DONTWAIT, MT_DATA); 539 *mret = m; 540 if (m != NULL) { 541 m->m_len = 0; 542 if (maxolen + db->hdrlen > MLEN) 543 MCLGET(m, M_DONTWAIT); 544 m->m_data += db->hdrlen; 545 wptr = mtod(m, u_char *); 546 cp_end = wptr + M_TRAILINGSPACE(m); 547 } else 548 wptr = cp_end = NULL; 549 550 /* 551 * Copy the PPP header over, changing the protocol, 552 * and install the 2-byte packet sequence number. 553 */ 554 if (wptr) { 555 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 556 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 557 *wptr++ = 0; /* change the protocol */ 558 *wptr++ = PPP_COMP; 559 *wptr++ = db->seqno >> 8; 560 *wptr++ = db->seqno; 561 } 562 ++db->seqno; 563 564 olen = 0; 565 rptr += PPP_HDRLEN; 566 slen = mp->m_len - PPP_HDRLEN; 567 ilen = slen + 1; 568 for (;;) { 569 if (slen <= 0) { 570 mp = mp->m_next; 571 if (!mp) 572 break; 573 rptr = mtod(mp, u_char *); 574 slen = mp->m_len; 575 if (!slen) 576 continue; /* handle 0-length buffers */ 577 ilen += slen; 578 } 579 580 slen--; 581 c = *rptr++; 582 fcode = BSD_KEY(ent, c); 583 hval = BSD_HASH(ent, c, hshift); 584 dictp = &db->dict[hval]; 585 586 /* Validate and then check the entry. */ 587 if (dictp->codem1 >= max_ent) 588 goto nomatch; 589 if (dictp->f.fcode == fcode) { 590 ent = dictp->codem1+1; 591 continue; /* found (prefix,suffix) */ 592 } 593 594 /* continue probing until a match or invalid entry */ 595 disp = (hval == 0) ? 1 : hval; 596 do { 597 hval += disp; 598 if (hval >= db->hsize) 599 hval -= db->hsize; 600 dictp = &db->dict[hval]; 601 if (dictp->codem1 >= max_ent) 602 goto nomatch; 603 } while (dictp->f.fcode != fcode); 604 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 605 continue; 606 607 nomatch: 608 OUTPUT(ent); /* output the prefix */ 609 610 /* code -> hashtable */ 611 if (max_ent < db->maxmaxcode) { 612 struct bsd_dict *dictp2; 613 /* expand code size if needed */ 614 if (max_ent >= MAXCODE(n_bits)) 615 db->n_bits = ++n_bits; 616 617 /* Invalidate old hash table entry using 618 * this code, and then take it over. 619 */ 620 dictp2 = &db->dict[max_ent+1]; 621 if (db->dict[dictp2->cptr].codem1 == max_ent) 622 db->dict[dictp2->cptr].codem1 = BADCODEM1; 623 dictp2->cptr = hval; 624 dictp->codem1 = max_ent; 625 dictp->f.fcode = fcode; 626 627 db->max_ent = ++max_ent; 628 } 629 ent = c; 630 } 631 632 OUTPUT(ent); /* output the last code */ 633 db->bytes_out += olen; 634 db->in_count += ilen; 635 if (bitno < 32) 636 ++db->bytes_out; /* count complete bytes */ 637 638 if (bsd_check(db)) 639 OUTPUT(CLEAR); /* do not count the CLEAR */ 640 641 /* 642 * Pad dribble bits of last code with ones. 643 * Do not emit a completely useless byte of ones. 644 */ 645 if (bitno != 32) 646 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 647 648 if (m != NULL) { 649 m->m_len = wptr - mtod(m, u_char *); 650 m->m_next = NULL; 651 } 652 653 /* 654 * Increase code size if we would have without the packet 655 * boundary and as the decompressor will. 656 */ 657 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 658 db->n_bits++; 659 660 db->uncomp_bytes += ilen; 661 ++db->uncomp_count; 662 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 663 /* throw away the compressed stuff if it is longer than uncompressed */ 664 if (*mret != NULL) { 665 m_freem(*mret); 666 *mret = NULL; 667 } 668 ++db->incomp_count; 669 db->incomp_bytes += ilen; 670 } else { 671 ++db->comp_count; 672 db->comp_bytes += olen + BSD_OVHD; 673 } 674 675 return olen + PPP_HDRLEN + BSD_OVHD; 676 #undef OUTPUT 677 #undef PUTBYTE 678 } 679 680 681 /* 682 * Update the "BSD Compress" dictionary on the receiver for 683 * incompressible data by pretending to compress the incoming data. 684 */ 685 static void 686 bsd_incomp(state, dmsg) 687 void *state; 688 struct mbuf *dmsg; 689 { 690 struct bsd_db *db = (struct bsd_db *) state; 691 u_int hshift = db->hshift; 692 u_int max_ent = db->max_ent; 693 u_int n_bits = db->n_bits; 694 struct bsd_dict *dictp; 695 u_int32_t fcode; 696 u_char c; 697 u_int32_t hval, disp; 698 int slen, ilen; 699 u_int bitno = 7; 700 u_char *rptr; 701 u_int ent; 702 703 /* 704 * If the protocol is not in the range we're interested in, 705 * just return without looking at the packet. If it is, 706 * the protocol becomes the first byte to "compress". 707 */ 708 rptr = mtod(dmsg, u_char *); 709 ent = PPP_PROTOCOL(rptr); 710 if (ent < 0x21 || ent > 0xf9) 711 return; 712 713 db->incomp_count++; 714 db->seqno++; 715 ilen = 1; /* count the protocol as 1 byte */ 716 rptr += PPP_HDRLEN; 717 slen = dmsg->m_len - PPP_HDRLEN; 718 for (;;) { 719 if (slen <= 0) { 720 dmsg = dmsg->m_next; 721 if (!dmsg) 722 break; 723 rptr = mtod(dmsg, u_char *); 724 slen = dmsg->m_len; 725 continue; 726 } 727 ilen += slen; 728 729 do { 730 c = *rptr++; 731 fcode = BSD_KEY(ent, c); 732 hval = BSD_HASH(ent, c, hshift); 733 dictp = &db->dict[hval]; 734 735 /* validate and then check the entry */ 736 if (dictp->codem1 >= max_ent) 737 goto nomatch; 738 if (dictp->f.fcode == fcode) { 739 ent = dictp->codem1+1; 740 continue; /* found (prefix,suffix) */ 741 } 742 743 /* continue probing until a match or invalid entry */ 744 disp = (hval == 0) ? 1 : hval; 745 do { 746 hval += disp; 747 if (hval >= db->hsize) 748 hval -= db->hsize; 749 dictp = &db->dict[hval]; 750 if (dictp->codem1 >= max_ent) 751 goto nomatch; 752 } while (dictp->f.fcode != fcode); 753 ent = dictp->codem1+1; 754 continue; /* finally found (prefix,suffix) */ 755 756 nomatch: /* output (count) the prefix */ 757 bitno += n_bits; 758 759 /* code -> hashtable */ 760 if (max_ent < db->maxmaxcode) { 761 struct bsd_dict *dictp2; 762 /* expand code size if needed */ 763 if (max_ent >= MAXCODE(n_bits)) 764 db->n_bits = ++n_bits; 765 766 /* Invalidate previous hash table entry 767 * assigned this code, and then take it over. 768 */ 769 dictp2 = &db->dict[max_ent+1]; 770 if (db->dict[dictp2->cptr].codem1 == max_ent) 771 db->dict[dictp2->cptr].codem1 = BADCODEM1; 772 dictp2->cptr = hval; 773 dictp->codem1 = max_ent; 774 dictp->f.fcode = fcode; 775 776 db->max_ent = ++max_ent; 777 db->lens[max_ent] = db->lens[ent]+1; 778 } 779 ent = c; 780 } while (--slen != 0); 781 } 782 bitno += n_bits; /* output (count) the last code */ 783 db->bytes_out += bitno/8; 784 db->in_count += ilen; 785 (void)bsd_check(db); 786 787 ++db->incomp_count; 788 db->incomp_bytes += ilen; 789 ++db->uncomp_count; 790 db->uncomp_bytes += ilen; 791 792 /* Increase code size if we would have without the packet 793 * boundary and as the decompressor will. 794 */ 795 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 796 db->n_bits++; 797 } 798 799 800 /* 801 * Decompress "BSD Compress". 802 * 803 * Because of patent problems, we return DECOMP_ERROR for errors 804 * found by inspecting the input data and for system problems, but 805 * DECOMP_FATALERROR for any errors which could possibly be said to 806 * be being detected "after" decompression. For DECOMP_ERROR, 807 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 808 * infringing a patent of Motorola's if we do, so we take CCP down 809 * instead. 810 * 811 * Given that the frame has the correct sequence number and a good FCS, 812 * errors such as invalid codes in the input most likely indicate a 813 * bug, so we return DECOMP_FATALERROR for them in order to turn off 814 * compression, even though they are detected by inspecting the input. 815 */ 816 int 817 bsd_decompress(state, cmp, dmpp) 818 void *state; 819 struct mbuf *cmp, **dmpp; 820 { 821 struct bsd_db *db = (struct bsd_db *) state; 822 u_int max_ent = db->max_ent; 823 u_int32_t accm = 0; 824 u_int bitno = 32; /* 1st valid bit in accm */ 825 u_int n_bits = db->n_bits; 826 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 827 struct bsd_dict *dictp; 828 int explen, i, seq, len; 829 u_int incode, oldcode, finchar; 830 u_char *p, *rptr, *wptr; 831 struct mbuf *m, *dmp, *mret; 832 int adrs, ctrl, ilen; 833 int space, codelen, extra; 834 struct mbuf *last; 835 836 /* 837 * Save the address/control from the PPP header 838 * and then get the sequence number. 839 */ 840 *dmpp = NULL; 841 rptr = mtod(cmp, u_char *); 842 adrs = PPP_ADDRESS(rptr); 843 ctrl = PPP_CONTROL(rptr); 844 rptr += PPP_HDRLEN; 845 len = cmp->m_len - PPP_HDRLEN; 846 seq = 0; 847 for (i = 0; i < 2; ++i) { 848 while (len <= 0) { 849 cmp = cmp->m_next; 850 if (cmp == NULL) 851 return DECOMP_ERROR; 852 rptr = mtod(cmp, u_char *); 853 len = cmp->m_len; 854 } 855 seq = (seq << 8) + *rptr++; 856 --len; 857 } 858 859 /* 860 * Check the sequence number and give up if it differs from 861 * the value we're expecting. 862 */ 863 if (seq != db->seqno) { 864 if (db->debug) 865 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 866 db->unit, seq, db->seqno - 1); 867 return DECOMP_ERROR; 868 } 869 ++db->seqno; 870 871 /* 872 * Allocate one mbuf to start with. 873 */ 874 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 875 if (dmp == NULL) 876 return DECOMP_ERROR; 877 mret = dmp; 878 dmp->m_len = 0; 879 dmp->m_next = NULL; 880 MCLGET(dmp, M_DONTWAIT); 881 dmp->m_data += db->hdrlen; 882 wptr = mtod(dmp, u_char *); 883 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 884 885 /* 886 * Fill in the ppp header, but not the last byte of the protocol 887 * (that comes from the decompressed data). 888 */ 889 wptr[0] = adrs; 890 wptr[1] = ctrl; 891 wptr[2] = 0; 892 wptr += PPP_HDRLEN - 1; 893 894 ilen = len; 895 oldcode = CLEAR; 896 explen = 0; 897 for (;;) { 898 if (len == 0) { 899 cmp = cmp->m_next; 900 if (!cmp) /* quit at end of message */ 901 break; 902 rptr = mtod(cmp, u_char *); 903 len = cmp->m_len; 904 ilen += len; 905 continue; /* handle 0-length buffers */ 906 } 907 908 /* 909 * Accumulate bytes until we have a complete code. 910 * Then get the next code, relying on the 32-bit, 911 * unsigned accm to mask the result. 912 */ 913 bitno -= 8; 914 accm |= *rptr++ << bitno; 915 --len; 916 if (tgtbitno < bitno) 917 continue; 918 incode = accm >> tgtbitno; 919 accm <<= n_bits; 920 bitno += n_bits; 921 922 if (incode == CLEAR) { 923 /* 924 * The dictionary must only be cleared at 925 * the end of a packet. But there could be an 926 * empty mbuf at the end. 927 */ 928 if (len > 0 || cmp->m_next != NULL) { 929 while ((cmp = cmp->m_next) != NULL) 930 len += cmp->m_len; 931 if (len > 0) { 932 m_freem(mret); 933 if (db->debug) 934 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 935 return DECOMP_FATALERROR; /* probably a bug */ 936 } 937 } 938 bsd_clear(db); 939 explen = ilen = 0; 940 break; 941 } 942 943 if (incode > max_ent + 2 || incode > db->maxmaxcode 944 || incode > max_ent && oldcode == CLEAR) { 945 m_freem(mret); 946 if (db->debug) { 947 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 948 db->unit, incode, oldcode); 949 printf("max_ent=0x%x explen=%d seqno=%d\n", 950 max_ent, explen, db->seqno); 951 } 952 return DECOMP_FATALERROR; /* probably a bug */ 953 } 954 955 /* Special case for KwKwK string. */ 956 if (incode > max_ent) { 957 finchar = oldcode; 958 extra = 1; 959 } else { 960 finchar = incode; 961 extra = 0; 962 } 963 964 codelen = db->lens[finchar]; 965 explen += codelen + extra; 966 if (explen > db->mru + 1) { 967 m_freem(mret); 968 if (db->debug) { 969 printf("bsd_decomp%d: ran out of mru\n", db->unit); 970 #ifdef DEBUG 971 while ((cmp = cmp->m_next) != NULL) 972 len += cmp->m_len; 973 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 974 len, finchar, codelen, explen); 975 #endif 976 } 977 return DECOMP_FATALERROR; 978 } 979 980 /* 981 * For simplicity, the decoded characters go in a single mbuf, 982 * so we allocate a single extra cluster mbuf if necessary. 983 */ 984 if ((space -= codelen + extra) < 0) { 985 dmp->m_len = wptr - mtod(dmp, u_char *); 986 MGET(m, M_DONTWAIT, MT_DATA); 987 if (m == NULL) { 988 m_freem(mret); 989 return DECOMP_ERROR; 990 } 991 m->m_len = 0; 992 m->m_next = NULL; 993 dmp->m_next = m; 994 MCLGET(m, M_DONTWAIT); 995 space = M_TRAILINGSPACE(m) - (codelen + extra); 996 if (space < 0) { 997 /* now that's what I call *compression*. */ 998 m_freem(mret); 999 return DECOMP_ERROR; 1000 } 1001 dmp = m; 1002 wptr = mtod(dmp, u_char *); 1003 } 1004 1005 /* 1006 * Decode this code and install it in the decompressed buffer. 1007 */ 1008 p = (wptr += codelen); 1009 while (finchar > LAST) { 1010 dictp = &db->dict[db->dict[finchar].cptr]; 1011 #ifdef DEBUG 1012 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1013 goto bad; 1014 #endif 1015 *--p = dictp->f.hs.suffix; 1016 finchar = dictp->f.hs.prefix; 1017 } 1018 *--p = finchar; 1019 1020 #ifdef DEBUG 1021 if (--codelen != 0) 1022 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1023 db->unit, codelen, incode, max_ent); 1024 #endif 1025 1026 if (extra) /* the KwKwK case again */ 1027 *wptr++ = finchar; 1028 1029 /* 1030 * If not first code in a packet, and 1031 * if not out of code space, then allocate a new code. 1032 * 1033 * Keep the hash table correct so it can be used 1034 * with uncompressed packets. 1035 */ 1036 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1037 struct bsd_dict *dictp2; 1038 u_int32_t fcode; 1039 u_int32_t hval, disp; 1040 1041 fcode = BSD_KEY(oldcode,finchar); 1042 hval = BSD_HASH(oldcode,finchar,db->hshift); 1043 dictp = &db->dict[hval]; 1044 1045 /* look for a free hash table entry */ 1046 if (dictp->codem1 < max_ent) { 1047 disp = (hval == 0) ? 1 : hval; 1048 do { 1049 hval += disp; 1050 if (hval >= db->hsize) 1051 hval -= db->hsize; 1052 dictp = &db->dict[hval]; 1053 } while (dictp->codem1 < max_ent); 1054 } 1055 1056 /* 1057 * Invalidate previous hash table entry 1058 * assigned this code, and then take it over 1059 */ 1060 dictp2 = &db->dict[max_ent+1]; 1061 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1062 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1063 } 1064 dictp2->cptr = hval; 1065 dictp->codem1 = max_ent; 1066 dictp->f.fcode = fcode; 1067 1068 db->max_ent = ++max_ent; 1069 db->lens[max_ent] = db->lens[oldcode]+1; 1070 1071 /* Expand code size if needed. */ 1072 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1073 db->n_bits = ++n_bits; 1074 tgtbitno = 32-n_bits; 1075 } 1076 } 1077 oldcode = incode; 1078 } 1079 dmp->m_len = wptr - mtod(dmp, u_char *); 1080 1081 /* 1082 * Keep the checkpoint right so that incompressible packets 1083 * clear the dictionary at the right times. 1084 */ 1085 db->bytes_out += ilen; 1086 db->in_count += explen; 1087 if (bsd_check(db) && db->debug) { 1088 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1089 db->unit); 1090 } 1091 1092 ++db->comp_count; 1093 db->comp_bytes += ilen + BSD_OVHD; 1094 ++db->uncomp_count; 1095 db->uncomp_bytes += explen; 1096 1097 *dmpp = mret; 1098 return DECOMP_OK; 1099 1100 #ifdef DEBUG 1101 bad: 1102 if (codelen <= 0) { 1103 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1104 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1105 incode, finchar, db->dict[finchar].cptr, max_ent); 1106 } else if (dictp->codem1 != finchar-1) { 1107 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1108 db->unit, incode, finchar); 1109 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1110 db->dict[finchar].cptr, dictp->codem1); 1111 } 1112 m_freem(mret); 1113 return DECOMP_FATALERROR; 1114 #endif /* DEBUG */ 1115 } 1116 #endif /* DO_BSD_COMPRESS */ 1117