1 /* $NetBSD: bsd-comp.c,v 1.12 2003/08/07 16:32:48 agc 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. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 /* 40 * This version is for use with mbufs on BSD-derived systems. 41 */ 42 43 #include <sys/cdefs.h> 44 __KERNEL_RCSID(0, "$NetBSD: bsd-comp.c,v 1.12 2003/08/07 16:32:48 agc Exp $"); 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/mbuf.h> 49 #include <sys/socket.h> 50 #include <net/if.h> 51 #include <net/if_types.h> 52 #include <net/ppp_defs.h> 53 #include <net/if_ppp.h> 54 55 #define PACKETPTR struct mbuf * 56 #include <net/ppp-comp.h> 57 58 #if DO_BSD_COMPRESS 59 /* 60 * PPP "BSD compress" compression 61 * The differences between this compression and the classic BSD LZW 62 * source are obvious from the requirement that the classic code worked 63 * with files while this handles arbitrarily long streams that 64 * are broken into packets. They are: 65 * 66 * When the code size expands, a block of junk is not emitted by 67 * the compressor and not expected by the decompressor. 68 * 69 * New codes are not necessarily assigned every time an old 70 * code is output by the compressor. This is because a packet 71 * end forces a code to be emitted, but does not imply that a 72 * new sequence has been seen. 73 * 74 * The compression ratio is checked at the first end of a packet 75 * after the appropriate gap. Besides simplifying and speeding 76 * things up, this makes it more likely that the transmitter 77 * and receiver will agree when the dictionary is cleared when 78 * compression is not going well. 79 */ 80 81 /* 82 * A dictionary for doing BSD compress. 83 */ 84 struct bsd_db { 85 int totlen; /* length of this structure */ 86 u_int hsize; /* size of the hash table */ 87 u_char hshift; /* used in hash function */ 88 u_char n_bits; /* current bits/code */ 89 u_char maxbits; 90 u_char debug; 91 u_char unit; 92 u_int16_t seqno; /* sequence # of next packet */ 93 u_int hdrlen; /* header length to preallocate */ 94 u_int mru; 95 u_int maxmaxcode; /* largest valid code */ 96 u_int max_ent; /* largest code in use */ 97 u_int in_count; /* uncompressed bytes, aged */ 98 u_int bytes_out; /* compressed bytes, aged */ 99 u_int ratio; /* recent compression ratio */ 100 u_int checkpoint; /* when to next check the ratio */ 101 u_int clear_count; /* times dictionary cleared */ 102 u_int incomp_count; /* incompressible packets */ 103 u_int incomp_bytes; /* incompressible bytes */ 104 u_int uncomp_count; /* uncompressed packets */ 105 u_int uncomp_bytes; /* uncompressed bytes */ 106 u_int comp_count; /* compressed packets */ 107 u_int comp_bytes; /* compressed bytes */ 108 u_int16_t *lens; /* array of lengths of codes */ 109 struct bsd_dict { 110 union { /* hash value */ 111 u_int32_t fcode; 112 struct { 113 #if BYTE_ORDER == LITTLE_ENDIAN 114 u_int16_t prefix; /* preceding code */ 115 u_char suffix; /* last character of new code */ 116 u_char pad; 117 #else 118 u_char pad; 119 u_char suffix; /* last character of new code */ 120 u_int16_t prefix; /* preceding code */ 121 #endif 122 } hs; 123 } f; 124 u_int16_t codem1; /* output of hash table -1 */ 125 u_int16_t cptr; /* map code to hash table entry */ 126 } dict[1]; 127 }; 128 129 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 130 #define BSD_INIT_BITS BSD_MIN_BITS 131 132 static void *bsd_comp_alloc __P((u_char *options, int opt_len)); 133 static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); 134 static void bsd_free __P((void *state)); 135 static int bsd_comp_init __P((void *state, u_char *options, int opt_len, 136 int unit, int hdrlen, int debug)); 137 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, 138 int unit, int hdrlen, int mru, int debug)); 139 static int bsd_compress __P((void *state, struct mbuf **mret, 140 struct mbuf *mp, int slen, int maxolen)); 141 static void bsd_incomp __P((void *state, struct mbuf *dmsg)); 142 static int bsd_decompress __P((void *state, struct mbuf *cmp, 143 struct mbuf **dmpp)); 144 static void bsd_reset __P((void *state)); 145 static void bsd_comp_stats __P((void *state, struct compstat *stats)); 146 147 /* 148 * Procedures exported to if_ppp.c. 149 */ 150 struct compressor ppp_bsd_compress = { 151 CI_BSD_COMPRESS, /* compress_proto */ 152 bsd_comp_alloc, /* comp_alloc */ 153 bsd_free, /* comp_free */ 154 bsd_comp_init, /* comp_init */ 155 bsd_reset, /* comp_reset */ 156 bsd_compress, /* compress */ 157 bsd_comp_stats, /* comp_stat */ 158 bsd_decomp_alloc, /* decomp_alloc */ 159 bsd_free, /* decomp_free */ 160 bsd_decomp_init, /* decomp_init */ 161 bsd_reset, /* decomp_reset */ 162 bsd_decompress, /* decompress */ 163 bsd_incomp, /* incomp */ 164 bsd_comp_stats, /* decomp_stat */ 165 }; 166 167 /* 168 * the next two codes should not be changed lightly, as they must not 169 * lie within the contiguous general code space. 170 */ 171 #define CLEAR 256 /* table clear output code */ 172 #define FIRST 257 /* first free entry */ 173 #define LAST 255 174 175 #define MAXCODE(b) ((1 << (b)) - 1) 176 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 177 178 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 179 ^ (u_int32_t)(prefix)) 180 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 181 + (u_int32_t)(prefix)) 182 183 #define CHECK_GAP 10000 /* Ratio check interval */ 184 185 #define RATIO_SCALE_LOG 8 186 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 187 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 188 189 static void bsd_clear __P((struct bsd_db *)); 190 static int bsd_check __P((struct bsd_db *)); 191 static void *bsd_alloc __P((u_char *, int, int)); 192 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int, 193 int, int)); 194 195 /* 196 * clear the dictionary 197 */ 198 static void 199 bsd_clear(db) 200 struct bsd_db *db; 201 { 202 db->clear_count++; 203 db->max_ent = FIRST-1; 204 db->n_bits = BSD_INIT_BITS; 205 db->ratio = 0; 206 db->bytes_out = 0; 207 db->in_count = 0; 208 db->checkpoint = CHECK_GAP; 209 } 210 211 /* 212 * If the dictionary is full, then see if it is time to reset it. 213 * 214 * Compute the compression ratio using fixed-point arithmetic 215 * with 8 fractional bits. 216 * 217 * Since we have an infinite stream instead of a single file, 218 * watch only the local compression ratio. 219 * 220 * Since both peers must reset the dictionary at the same time even in 221 * the absence of CLEAR codes (while packets are incompressible), they 222 * must compute the same ratio. 223 */ 224 static int /* 1=output CLEAR */ 225 bsd_check(db) 226 struct bsd_db *db; 227 { 228 u_int new_ratio; 229 230 if (db->in_count >= db->checkpoint) { 231 /* age the ratio by limiting the size of the counts */ 232 if (db->in_count >= RATIO_MAX 233 || db->bytes_out >= RATIO_MAX) { 234 db->in_count -= db->in_count/4; 235 db->bytes_out -= db->bytes_out/4; 236 } 237 238 db->checkpoint = db->in_count + CHECK_GAP; 239 240 if (db->max_ent >= db->maxmaxcode) { 241 /* Reset the dictionary only if the ratio is worse, 242 * or if it looks as if it has been poisoned 243 * by incompressible data. 244 * 245 * This does not overflow, because 246 * db->in_count <= RATIO_MAX. 247 */ 248 new_ratio = db->in_count << RATIO_SCALE_LOG; 249 if (db->bytes_out != 0) 250 new_ratio /= db->bytes_out; 251 252 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 253 bsd_clear(db); 254 return 1; 255 } 256 db->ratio = new_ratio; 257 } 258 } 259 return 0; 260 } 261 262 /* 263 * Return statistics. 264 */ 265 static void 266 bsd_comp_stats(state, stats) 267 void *state; 268 struct compstat *stats; 269 { 270 struct bsd_db *db = (struct bsd_db *) state; 271 u_int out; 272 273 stats->unc_bytes = db->uncomp_bytes; 274 stats->unc_packets = db->uncomp_count; 275 stats->comp_bytes = db->comp_bytes; 276 stats->comp_packets = db->comp_count; 277 stats->inc_bytes = db->incomp_bytes; 278 stats->inc_packets = db->incomp_count; 279 stats->ratio = db->in_count; 280 out = db->bytes_out; 281 if (stats->ratio <= 0x7fffff) 282 stats->ratio <<= 8; 283 else 284 out >>= 8; 285 if (out != 0) 286 stats->ratio /= out; 287 } 288 289 /* 290 * Reset state, as on a CCP ResetReq. 291 */ 292 static void 293 bsd_reset(state) 294 void *state; 295 { 296 struct bsd_db *db = (struct bsd_db *) state; 297 298 db->seqno = 0; 299 bsd_clear(db); 300 db->clear_count = 0; 301 } 302 303 /* 304 * Allocate space for a (de) compressor. 305 */ 306 static void * 307 bsd_alloc(options, opt_len, decomp) 308 u_char *options; 309 int opt_len, decomp; 310 { 311 int bits; 312 u_int newlen, hsize, hshift, maxmaxcode; 313 struct bsd_db *db; 314 315 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 316 || options[1] != CILEN_BSD_COMPRESS 317 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 318 return NULL; 319 bits = BSD_NBITS(options[2]); 320 switch (bits) { 321 case 9: /* needs 82152 for both directions */ 322 case 10: /* needs 84144 */ 323 case 11: /* needs 88240 */ 324 case 12: /* needs 96432 */ 325 hsize = 5003; 326 hshift = 4; 327 break; 328 case 13: /* needs 176784 */ 329 hsize = 9001; 330 hshift = 5; 331 break; 332 case 14: /* needs 353744 */ 333 hsize = 18013; 334 hshift = 6; 335 break; 336 case 15: /* needs 691440 */ 337 hsize = 35023; 338 hshift = 7; 339 break; 340 case 16: /* needs 1366160--far too much, */ 341 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 342 /* hshift = 8; */ /* in struct bsd_db */ 343 /* break; */ 344 default: 345 return NULL; 346 } 347 348 maxmaxcode = MAXCODE(bits); 349 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 350 db = malloc(newlen, M_DEVBUF, M_NOWAIT); 351 if (!db) 352 return NULL; 353 memset(db, 0, sizeof(*db) - sizeof(db->dict)); 354 355 if (!decomp) { 356 db->lens = NULL; 357 } else { 358 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]), 359 M_DEVBUF, M_NOWAIT); 360 if (!db->lens) { 361 free(db, M_DEVBUF); 362 return NULL; 363 } 364 } 365 366 db->totlen = newlen; 367 db->hsize = hsize; 368 db->hshift = hshift; 369 db->maxmaxcode = maxmaxcode; 370 db->maxbits = bits; 371 372 return (void *) db; 373 } 374 375 static void 376 bsd_free(state) 377 void *state; 378 { 379 struct bsd_db *db = (struct bsd_db *) state; 380 381 if (db->lens) 382 free(db->lens, M_DEVBUF); 383 free(db, M_DEVBUF); 384 } 385 386 static void * 387 bsd_comp_alloc(options, opt_len) 388 u_char *options; 389 int opt_len; 390 { 391 return bsd_alloc(options, opt_len, 0); 392 } 393 394 static void * 395 bsd_decomp_alloc(options, opt_len) 396 u_char *options; 397 int opt_len; 398 { 399 return bsd_alloc(options, opt_len, 1); 400 } 401 402 /* 403 * Initialize the database. 404 */ 405 static int 406 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 407 struct bsd_db *db; 408 u_char *options; 409 int opt_len, unit, hdrlen, mru, debug, decomp; 410 { 411 int i; 412 413 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 414 || options[1] != CILEN_BSD_COMPRESS 415 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 416 || BSD_NBITS(options[2]) != db->maxbits 417 || (decomp && db->lens == NULL)) 418 return 0; 419 420 if (decomp) { 421 i = LAST+1; 422 while (i != 0) 423 db->lens[--i] = 1; 424 } 425 i = db->hsize; 426 while (i != 0) { 427 db->dict[--i].codem1 = BADCODEM1; 428 db->dict[i].cptr = 0; 429 } 430 431 db->unit = unit; 432 db->hdrlen = hdrlen; 433 db->mru = mru; 434 #ifndef DEBUG 435 if (debug) 436 #endif 437 db->debug = 1; 438 439 bsd_reset(db); 440 441 return 1; 442 } 443 444 static int 445 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 446 void *state; 447 u_char *options; 448 int opt_len, unit, hdrlen, debug; 449 { 450 return bsd_init((struct bsd_db *) state, options, opt_len, 451 unit, hdrlen, 0, debug, 0); 452 } 453 454 static int 455 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 456 void *state; 457 u_char *options; 458 int opt_len, unit, hdrlen, mru, debug; 459 { 460 return bsd_init((struct bsd_db *) state, options, opt_len, 461 unit, hdrlen, mru, debug, 1); 462 } 463 464 465 /* 466 * compress a packet 467 * One change from the BSD compress command is that when the 468 * code size expands, we do not output a bunch of padding. 469 */ 470 int /* new slen */ 471 bsd_compress(state, mret, mp, slen, maxolen) 472 void *state; 473 struct mbuf **mret; /* return compressed mbuf chain here */ 474 struct mbuf *mp; /* from here */ 475 int slen; /* uncompressed length */ 476 int maxolen; /* max compressed length */ 477 { 478 struct bsd_db *db = (struct bsd_db *) state; 479 int hshift = db->hshift; 480 u_int max_ent = db->max_ent; 481 u_int n_bits = db->n_bits; 482 u_int bitno = 32; 483 u_int32_t accm = 0, fcode; 484 struct bsd_dict *dictp; 485 u_char c; 486 int hval, disp, ent, ilen; 487 u_char *rptr, *wptr; 488 u_char *cp_end; 489 int olen; 490 struct mbuf *m; 491 492 #define PUTBYTE(v) { \ 493 ++olen; \ 494 if (wptr) { \ 495 *wptr++ = (v); \ 496 if (wptr >= cp_end) { \ 497 m->m_len = wptr - mtod(m, u_char *); \ 498 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 499 m = m->m_next; \ 500 if (m) { \ 501 m->m_len = 0; \ 502 if (maxolen - olen > MLEN) \ 503 MCLGET(m, M_DONTWAIT); \ 504 wptr = mtod(m, u_char *); \ 505 cp_end = wptr + M_TRAILINGSPACE(m); \ 506 } else \ 507 wptr = NULL; \ 508 } \ 509 } \ 510 } 511 512 #define OUTPUT(ent) { \ 513 bitno -= n_bits; \ 514 accm |= ((ent) << bitno); \ 515 do { \ 516 PUTBYTE(accm >> 24); \ 517 accm <<= 8; \ 518 bitno += 8; \ 519 } while (bitno <= 24); \ 520 } 521 522 /* 523 * If the protocol is not in the range we're interested in, 524 * just return without compressing the packet. If it is, 525 * the protocol becomes the first byte to compress. 526 */ 527 rptr = mtod(mp, u_char *); 528 ent = PPP_PROTOCOL(rptr); 529 if (ent < 0x21 || ent > 0xf9) { 530 *mret = NULL; 531 return slen; 532 } 533 534 /* Don't generate compressed packets which are larger than 535 the uncompressed packet. */ 536 if (maxolen > slen) 537 maxolen = slen; 538 539 /* Allocate one mbuf to start with. */ 540 MGET(m, M_DONTWAIT, MT_DATA); 541 *mret = m; 542 if (m != NULL) { 543 m->m_len = 0; 544 if (maxolen + db->hdrlen > MLEN) 545 MCLGET(m, M_DONTWAIT); 546 m->m_data += db->hdrlen; 547 wptr = mtod(m, u_char *); 548 cp_end = wptr + M_TRAILINGSPACE(m); 549 } else 550 wptr = cp_end = NULL; 551 552 /* 553 * Copy the PPP header over, changing the protocol, 554 * and install the 2-byte packet sequence number. 555 */ 556 if (wptr) { 557 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 558 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 559 *wptr++ = 0; /* change the protocol */ 560 *wptr++ = PPP_COMP; 561 *wptr++ = db->seqno >> 8; 562 *wptr++ = db->seqno; 563 } 564 ++db->seqno; 565 566 olen = 0; 567 rptr += PPP_HDRLEN; 568 slen = mp->m_len - PPP_HDRLEN; 569 ilen = slen + 1; 570 for (;;) { 571 if (slen <= 0) { 572 mp = mp->m_next; 573 if (!mp) 574 break; 575 rptr = mtod(mp, u_char *); 576 slen = mp->m_len; 577 if (!slen) 578 continue; /* handle 0-length buffers */ 579 ilen += slen; 580 } 581 582 slen--; 583 c = *rptr++; 584 fcode = BSD_KEY(ent, c); 585 hval = BSD_HASH(ent, c, hshift); 586 dictp = &db->dict[hval]; 587 588 /* Validate and then check the entry. */ 589 if (dictp->codem1 >= max_ent) 590 goto nomatch; 591 if (dictp->f.fcode == fcode) { 592 ent = dictp->codem1+1; 593 continue; /* found (prefix,suffix) */ 594 } 595 596 /* continue probing until a match or invalid entry */ 597 disp = (hval == 0) ? 1 : hval; 598 do { 599 hval += disp; 600 if (hval >= db->hsize) 601 hval -= db->hsize; 602 dictp = &db->dict[hval]; 603 if (dictp->codem1 >= max_ent) 604 goto nomatch; 605 } while (dictp->f.fcode != fcode); 606 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 607 continue; 608 609 nomatch: 610 OUTPUT(ent); /* output the prefix */ 611 612 /* code -> hashtable */ 613 if (max_ent < db->maxmaxcode) { 614 struct bsd_dict *dictp2; 615 /* expand code size if needed */ 616 if (max_ent >= MAXCODE(n_bits)) 617 db->n_bits = ++n_bits; 618 619 /* Invalidate old hash table entry using 620 * this code, and then take it over. 621 */ 622 dictp2 = &db->dict[max_ent+1]; 623 if (db->dict[dictp2->cptr].codem1 == max_ent) 624 db->dict[dictp2->cptr].codem1 = BADCODEM1; 625 dictp2->cptr = hval; 626 dictp->codem1 = max_ent; 627 dictp->f.fcode = fcode; 628 629 db->max_ent = ++max_ent; 630 } 631 ent = c; 632 } 633 634 OUTPUT(ent); /* output the last code */ 635 db->bytes_out += olen; 636 db->in_count += ilen; 637 if (bitno < 32) 638 ++db->bytes_out; /* count complete bytes */ 639 640 if (bsd_check(db)) 641 OUTPUT(CLEAR); /* do not count the CLEAR */ 642 643 /* 644 * Pad dribble bits of last code with ones. 645 * Do not emit a completely useless byte of ones. 646 */ 647 if (bitno != 32) 648 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 649 650 if (m != NULL) { 651 m->m_len = wptr - mtod(m, u_char *); 652 m->m_next = NULL; 653 } 654 655 /* 656 * Increase code size if we would have without the packet 657 * boundary and as the decompressor will. 658 */ 659 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 660 db->n_bits++; 661 662 db->uncomp_bytes += ilen; 663 ++db->uncomp_count; 664 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 665 /* throw away the compressed stuff if it is longer than uncompressed */ 666 if (*mret != NULL) { 667 m_freem(*mret); 668 *mret = NULL; 669 } 670 ++db->incomp_count; 671 db->incomp_bytes += ilen; 672 } else { 673 ++db->comp_count; 674 db->comp_bytes += olen + BSD_OVHD; 675 } 676 677 return olen + PPP_HDRLEN + BSD_OVHD; 678 #undef OUTPUT 679 #undef PUTBYTE 680 } 681 682 683 /* 684 * Update the "BSD Compress" dictionary on the receiver for 685 * incompressible data by pretending to compress the incoming data. 686 */ 687 static void 688 bsd_incomp(state, dmsg) 689 void *state; 690 struct mbuf *dmsg; 691 { 692 struct bsd_db *db = (struct bsd_db *) state; 693 u_int hshift = db->hshift; 694 u_int max_ent = db->max_ent; 695 u_int n_bits = db->n_bits; 696 struct bsd_dict *dictp; 697 u_int32_t fcode; 698 u_char c; 699 u_int32_t hval, disp; 700 int slen, ilen; 701 u_int bitno = 7; 702 u_char *rptr; 703 u_int ent; 704 705 /* 706 * If the protocol is not in the range we're interested in, 707 * just return without looking at the packet. If it is, 708 * the protocol becomes the first byte to "compress". 709 */ 710 rptr = mtod(dmsg, u_char *); 711 ent = PPP_PROTOCOL(rptr); 712 if (ent < 0x21 || ent > 0xf9) 713 return; 714 715 db->seqno++; 716 ilen = 1; /* count the protocol as 1 byte */ 717 rptr += PPP_HDRLEN; 718 slen = dmsg->m_len - PPP_HDRLEN; 719 for (;;) { 720 if (slen <= 0) { 721 dmsg = dmsg->m_next; 722 if (!dmsg) 723 break; 724 rptr = mtod(dmsg, u_char *); 725 slen = dmsg->m_len; 726 continue; 727 } 728 ilen += slen; 729 730 do { 731 c = *rptr++; 732 fcode = BSD_KEY(ent, c); 733 hval = BSD_HASH(ent, c, hshift); 734 dictp = &db->dict[hval]; 735 736 /* validate and then check the entry */ 737 if (dictp->codem1 >= max_ent) 738 goto nomatch; 739 if (dictp->f.fcode == fcode) { 740 ent = dictp->codem1+1; 741 continue; /* found (prefix,suffix) */ 742 } 743 744 /* continue probing until a match or invalid entry */ 745 disp = (hval == 0) ? 1 : hval; 746 do { 747 hval += disp; 748 if (hval >= db->hsize) 749 hval -= db->hsize; 750 dictp = &db->dict[hval]; 751 if (dictp->codem1 >= max_ent) 752 goto nomatch; 753 } while (dictp->f.fcode != fcode); 754 ent = dictp->codem1+1; 755 continue; /* finally found (prefix,suffix) */ 756 757 nomatch: /* output (count) the prefix */ 758 bitno += n_bits; 759 760 /* code -> hashtable */ 761 if (max_ent < db->maxmaxcode) { 762 struct bsd_dict *dictp2; 763 /* expand code size if needed */ 764 if (max_ent >= MAXCODE(n_bits)) 765 db->n_bits = ++n_bits; 766 767 /* Invalidate previous hash table entry 768 * assigned this code, and then take it over. 769 */ 770 dictp2 = &db->dict[max_ent+1]; 771 if (db->dict[dictp2->cptr].codem1 == max_ent) 772 db->dict[dictp2->cptr].codem1 = BADCODEM1; 773 dictp2->cptr = hval; 774 dictp->codem1 = max_ent; 775 dictp->f.fcode = fcode; 776 777 db->max_ent = ++max_ent; 778 db->lens[max_ent] = db->lens[ent]+1; 779 } 780 ent = c; 781 } while (--slen != 0); 782 } 783 bitno += n_bits; /* output (count) the last code */ 784 db->bytes_out += bitno/8; 785 db->in_count += ilen; 786 (void)bsd_check(db); 787 788 ++db->incomp_count; 789 db->incomp_bytes += ilen; 790 ++db->uncomp_count; 791 db->uncomp_bytes += ilen; 792 793 /* Increase code size if we would have without the packet 794 * boundary and as the decompressor will. 795 */ 796 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 797 db->n_bits++; 798 } 799 800 801 /* 802 * Decompress "BSD Compress". 803 * 804 * Because of patent problems, we return DECOMP_ERROR for errors 805 * found by inspecting the input data and for system problems, but 806 * DECOMP_FATALERROR for any errors which could possibly be said to 807 * be being detected "after" decompression. For DECOMP_ERROR, 808 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 809 * infringing a patent of Motorola's if we do, so we take CCP down 810 * instead. 811 * 812 * Given that the frame has the correct sequence number and a good FCS, 813 * errors such as invalid codes in the input most likely indicate a 814 * bug, so we return DECOMP_FATALERROR for them in order to turn off 815 * compression, even though they are detected by inspecting the input. 816 */ 817 int 818 bsd_decompress(state, cmp, dmpp) 819 void *state; 820 struct mbuf *cmp, **dmpp; 821 { 822 struct bsd_db *db = (struct bsd_db *) state; 823 u_int max_ent = db->max_ent; 824 u_int32_t accm = 0; 825 u_int bitno = 32; /* 1st valid bit in accm */ 826 u_int n_bits = db->n_bits; 827 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 828 struct bsd_dict *dictp; 829 int explen, i, seq, len; 830 u_int incode, oldcode, finchar; 831 u_char *p, *rptr, *wptr; 832 struct mbuf *m, *dmp, *mret; 833 int adrs, ctrl, ilen; 834 int space, codelen, extra; 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