1 /* $NetBSD: bsd-comp.c,v 1.6 1996/10/13 02:10:58 christos 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 46 #include <sys/param.h> 47 #include <sys/types.h> 48 #include <sys/systm.h> 49 #include <sys/mbuf.h> 50 #include <sys/socket.h> 51 #include <net/if.h> 52 #include <net/if_types.h> 53 #include <net/ppp_defs.h> 54 #include <net/if_ppp.h> 55 56 #define PACKETPTR struct mbuf * 57 #include <net/ppp-comp.h> 58 59 #if DO_BSD_COMPRESS 60 /* 61 * PPP "BSD compress" compression 62 * The differences between this compression and the classic BSD LZW 63 * source are obvious from the requirement that the classic code worked 64 * with files while this handles arbitrarily long streams that 65 * are broken into packets. They are: 66 * 67 * When the code size expands, a block of junk is not emitted by 68 * the compressor and not expected by the decompressor. 69 * 70 * New codes are not necessarily assigned every time an old 71 * code is output by the compressor. This is because a packet 72 * end forces a code to be emitted, but does not imply that a 73 * new sequence has been seen. 74 * 75 * The compression ratio is checked at the first end of a packet 76 * after the appropriate gap. Besides simplifying and speeding 77 * things up, this makes it more likely that the transmitter 78 * and receiver will agree when the dictionary is cleared when 79 * compression is not going well. 80 */ 81 82 /* 83 * A dictionary for doing BSD compress. 84 */ 85 struct bsd_db { 86 int totlen; /* length of this structure */ 87 u_int hsize; /* size of the hash table */ 88 u_char hshift; /* used in hash function */ 89 u_char n_bits; /* current bits/code */ 90 u_char maxbits; 91 u_char debug; 92 u_char unit; 93 u_int16_t seqno; /* sequence # of next packet */ 94 u_int hdrlen; /* header length to preallocate */ 95 u_int mru; 96 u_int maxmaxcode; /* largest valid code */ 97 u_int max_ent; /* largest code in use */ 98 u_int in_count; /* uncompressed bytes, aged */ 99 u_int bytes_out; /* compressed bytes, aged */ 100 u_int ratio; /* recent compression ratio */ 101 u_int checkpoint; /* when to next check the ratio */ 102 u_int clear_count; /* times dictionary cleared */ 103 u_int incomp_count; /* incompressible packets */ 104 u_int incomp_bytes; /* incompressible bytes */ 105 u_int uncomp_count; /* uncompressed packets */ 106 u_int uncomp_bytes; /* uncompressed bytes */ 107 u_int comp_count; /* compressed packets */ 108 u_int comp_bytes; /* compressed bytes */ 109 u_int16_t *lens; /* array of lengths of codes */ 110 struct bsd_dict { 111 union { /* hash value */ 112 u_int32_t fcode; 113 struct { 114 #if BYTE_ORDER == LITTLE_ENDIAN 115 u_int16_t prefix; /* preceding code */ 116 u_char suffix; /* last character of new code */ 117 u_char pad; 118 #else 119 u_char pad; 120 u_char suffix; /* last character of new code */ 121 u_int16_t prefix; /* preceding code */ 122 #endif 123 } hs; 124 } f; 125 u_int16_t codem1; /* output of hash table -1 */ 126 u_int16_t cptr; /* map code to hash table entry */ 127 } dict[1]; 128 }; 129 130 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 131 #define BSD_INIT_BITS BSD_MIN_BITS 132 133 static void *bsd_comp_alloc __P((u_char *options, int opt_len)); 134 static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); 135 static void bsd_free __P((void *state)); 136 static int bsd_comp_init __P((void *state, u_char *options, int opt_len, 137 int unit, int hdrlen, int debug)); 138 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, 139 int unit, int hdrlen, int mru, int debug)); 140 static int bsd_compress __P((void *state, struct mbuf **mret, 141 struct mbuf *mp, int slen, int maxolen)); 142 static void bsd_incomp __P((void *state, struct mbuf *dmsg)); 143 static int bsd_decompress __P((void *state, struct mbuf *cmp, 144 struct mbuf **dmpp)); 145 static void bsd_reset __P((void *state)); 146 static void bsd_comp_stats __P((void *state, struct compstat *stats)); 147 148 /* 149 * Procedures exported to if_ppp.c. 150 */ 151 struct compressor ppp_bsd_compress = { 152 CI_BSD_COMPRESS, /* compress_proto */ 153 bsd_comp_alloc, /* comp_alloc */ 154 bsd_free, /* comp_free */ 155 bsd_comp_init, /* comp_init */ 156 bsd_reset, /* comp_reset */ 157 bsd_compress, /* compress */ 158 bsd_comp_stats, /* comp_stat */ 159 bsd_decomp_alloc, /* decomp_alloc */ 160 bsd_free, /* decomp_free */ 161 bsd_decomp_init, /* decomp_init */ 162 bsd_reset, /* decomp_reset */ 163 bsd_decompress, /* decompress */ 164 bsd_incomp, /* incomp */ 165 bsd_comp_stats, /* decomp_stat */ 166 }; 167 168 /* 169 * the next two codes should not be changed lightly, as they must not 170 * lie within the contiguous general code space. 171 */ 172 #define CLEAR 256 /* table clear output code */ 173 #define FIRST 257 /* first free entry */ 174 #define LAST 255 175 176 #define MAXCODE(b) ((1 << (b)) - 1) 177 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 178 179 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 180 ^ (u_int32_t)(prefix)) 181 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 182 + (u_int32_t)(prefix)) 183 184 #define CHECK_GAP 10000 /* Ratio check interval */ 185 186 #define RATIO_SCALE_LOG 8 187 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 188 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 189 190 static void bsd_clear __P((struct bsd_db *)); 191 static int bsd_check __P((struct bsd_db *)); 192 static void *bsd_alloc __P((u_char *, int, int)); 193 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int, 194 int, int)); 195 196 /* 197 * clear the dictionary 198 */ 199 static void 200 bsd_clear(db) 201 struct bsd_db *db; 202 { 203 db->clear_count++; 204 db->max_ent = FIRST-1; 205 db->n_bits = BSD_INIT_BITS; 206 db->ratio = 0; 207 db->bytes_out = 0; 208 db->in_count = 0; 209 db->incomp_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->incomp_count++; 718 db->seqno++; 719 ilen = 1; /* count the protocol as 1 byte */ 720 rptr += PPP_HDRLEN; 721 slen = dmsg->m_len - PPP_HDRLEN; 722 for (;;) { 723 if (slen <= 0) { 724 dmsg = dmsg->m_next; 725 if (!dmsg) 726 break; 727 rptr = mtod(dmsg, u_char *); 728 slen = dmsg->m_len; 729 continue; 730 } 731 ilen += slen; 732 733 do { 734 c = *rptr++; 735 fcode = BSD_KEY(ent, c); 736 hval = BSD_HASH(ent, c, hshift); 737 dictp = &db->dict[hval]; 738 739 /* validate and then check the entry */ 740 if (dictp->codem1 >= max_ent) 741 goto nomatch; 742 if (dictp->f.fcode == fcode) { 743 ent = dictp->codem1+1; 744 continue; /* found (prefix,suffix) */ 745 } 746 747 /* continue probing until a match or invalid entry */ 748 disp = (hval == 0) ? 1 : hval; 749 do { 750 hval += disp; 751 if (hval >= db->hsize) 752 hval -= db->hsize; 753 dictp = &db->dict[hval]; 754 if (dictp->codem1 >= max_ent) 755 goto nomatch; 756 } while (dictp->f.fcode != fcode); 757 ent = dictp->codem1+1; 758 continue; /* finally found (prefix,suffix) */ 759 760 nomatch: /* output (count) the prefix */ 761 bitno += n_bits; 762 763 /* code -> hashtable */ 764 if (max_ent < db->maxmaxcode) { 765 struct bsd_dict *dictp2; 766 /* expand code size if needed */ 767 if (max_ent >= MAXCODE(n_bits)) 768 db->n_bits = ++n_bits; 769 770 /* Invalidate previous hash table entry 771 * assigned this code, and then take it over. 772 */ 773 dictp2 = &db->dict[max_ent+1]; 774 if (db->dict[dictp2->cptr].codem1 == max_ent) 775 db->dict[dictp2->cptr].codem1 = BADCODEM1; 776 dictp2->cptr = hval; 777 dictp->codem1 = max_ent; 778 dictp->f.fcode = fcode; 779 780 db->max_ent = ++max_ent; 781 db->lens[max_ent] = db->lens[ent]+1; 782 } 783 ent = c; 784 } while (--slen != 0); 785 } 786 bitno += n_bits; /* output (count) the last code */ 787 db->bytes_out += bitno/8; 788 db->in_count += ilen; 789 (void)bsd_check(db); 790 791 ++db->incomp_count; 792 db->incomp_bytes += ilen; 793 ++db->uncomp_count; 794 db->uncomp_bytes += ilen; 795 796 /* Increase code size if we would have without the packet 797 * boundary and as the decompressor will. 798 */ 799 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 800 db->n_bits++; 801 } 802 803 804 /* 805 * Decompress "BSD Compress". 806 * 807 * Because of patent problems, we return DECOMP_ERROR for errors 808 * found by inspecting the input data and for system problems, but 809 * DECOMP_FATALERROR for any errors which could possibly be said to 810 * be being detected "after" decompression. For DECOMP_ERROR, 811 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 812 * infringing a patent of Motorola's if we do, so we take CCP down 813 * instead. 814 * 815 * Given that the frame has the correct sequence number and a good FCS, 816 * errors such as invalid codes in the input most likely indicate a 817 * bug, so we return DECOMP_FATALERROR for them in order to turn off 818 * compression, even though they are detected by inspecting the input. 819 */ 820 int 821 bsd_decompress(state, cmp, dmpp) 822 void *state; 823 struct mbuf *cmp, **dmpp; 824 { 825 struct bsd_db *db = (struct bsd_db *) state; 826 u_int max_ent = db->max_ent; 827 u_int32_t accm = 0; 828 u_int bitno = 32; /* 1st valid bit in accm */ 829 u_int n_bits = db->n_bits; 830 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 831 struct bsd_dict *dictp; 832 int explen, i, seq, len; 833 u_int incode, oldcode, finchar; 834 u_char *p, *rptr, *wptr; 835 struct mbuf *m, *dmp, *mret; 836 int adrs, ctrl, ilen; 837 int space, codelen, extra; 838 839 /* 840 * Save the address/control from the PPP header 841 * and then get the sequence number. 842 */ 843 *dmpp = NULL; 844 rptr = mtod(cmp, u_char *); 845 adrs = PPP_ADDRESS(rptr); 846 ctrl = PPP_CONTROL(rptr); 847 rptr += PPP_HDRLEN; 848 len = cmp->m_len - PPP_HDRLEN; 849 seq = 0; 850 for (i = 0; i < 2; ++i) { 851 while (len <= 0) { 852 cmp = cmp->m_next; 853 if (cmp == NULL) 854 return DECOMP_ERROR; 855 rptr = mtod(cmp, u_char *); 856 len = cmp->m_len; 857 } 858 seq = (seq << 8) + *rptr++; 859 --len; 860 } 861 862 /* 863 * Check the sequence number and give up if it differs from 864 * the value we're expecting. 865 */ 866 if (seq != db->seqno) { 867 if (db->debug) 868 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 869 db->unit, seq, db->seqno - 1); 870 return DECOMP_ERROR; 871 } 872 ++db->seqno; 873 874 /* 875 * Allocate one mbuf to start with. 876 */ 877 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 878 if (dmp == NULL) 879 return DECOMP_ERROR; 880 mret = dmp; 881 dmp->m_len = 0; 882 dmp->m_next = NULL; 883 MCLGET(dmp, M_DONTWAIT); 884 dmp->m_data += db->hdrlen; 885 wptr = mtod(dmp, u_char *); 886 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 887 888 /* 889 * Fill in the ppp header, but not the last byte of the protocol 890 * (that comes from the decompressed data). 891 */ 892 wptr[0] = adrs; 893 wptr[1] = ctrl; 894 wptr[2] = 0; 895 wptr += PPP_HDRLEN - 1; 896 897 ilen = len; 898 oldcode = CLEAR; 899 explen = 0; 900 for (;;) { 901 if (len == 0) { 902 cmp = cmp->m_next; 903 if (!cmp) /* quit at end of message */ 904 break; 905 rptr = mtod(cmp, u_char *); 906 len = cmp->m_len; 907 ilen += len; 908 continue; /* handle 0-length buffers */ 909 } 910 911 /* 912 * Accumulate bytes until we have a complete code. 913 * Then get the next code, relying on the 32-bit, 914 * unsigned accm to mask the result. 915 */ 916 bitno -= 8; 917 accm |= *rptr++ << bitno; 918 --len; 919 if (tgtbitno < bitno) 920 continue; 921 incode = accm >> tgtbitno; 922 accm <<= n_bits; 923 bitno += n_bits; 924 925 if (incode == CLEAR) { 926 /* 927 * The dictionary must only be cleared at 928 * the end of a packet. But there could be an 929 * empty mbuf at the end. 930 */ 931 if (len > 0 || cmp->m_next != NULL) { 932 while ((cmp = cmp->m_next) != NULL) 933 len += cmp->m_len; 934 if (len > 0) { 935 m_freem(mret); 936 if (db->debug) 937 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 938 return DECOMP_FATALERROR; /* probably a bug */ 939 } 940 } 941 bsd_clear(db); 942 explen = ilen = 0; 943 break; 944 } 945 946 if (incode > max_ent + 2 || incode > db->maxmaxcode 947 || (incode > max_ent && oldcode == CLEAR)) { 948 m_freem(mret); 949 if (db->debug) { 950 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 951 db->unit, incode, oldcode); 952 printf("max_ent=0x%x explen=%d seqno=%d\n", 953 max_ent, explen, db->seqno); 954 } 955 return DECOMP_FATALERROR; /* probably a bug */ 956 } 957 958 /* Special case for KwKwK string. */ 959 if (incode > max_ent) { 960 finchar = oldcode; 961 extra = 1; 962 } else { 963 finchar = incode; 964 extra = 0; 965 } 966 967 codelen = db->lens[finchar]; 968 explen += codelen + extra; 969 if (explen > db->mru + 1) { 970 m_freem(mret); 971 if (db->debug) { 972 printf("bsd_decomp%d: ran out of mru\n", db->unit); 973 #ifdef DEBUG 974 while ((cmp = cmp->m_next) != NULL) 975 len += cmp->m_len; 976 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 977 len, finchar, codelen, explen); 978 #endif 979 } 980 return DECOMP_FATALERROR; 981 } 982 983 /* 984 * For simplicity, the decoded characters go in a single mbuf, 985 * so we allocate a single extra cluster mbuf if necessary. 986 */ 987 if ((space -= codelen + extra) < 0) { 988 dmp->m_len = wptr - mtod(dmp, u_char *); 989 MGET(m, M_DONTWAIT, MT_DATA); 990 if (m == NULL) { 991 m_freem(mret); 992 return DECOMP_ERROR; 993 } 994 m->m_len = 0; 995 m->m_next = NULL; 996 dmp->m_next = m; 997 MCLGET(m, M_DONTWAIT); 998 space = M_TRAILINGSPACE(m) - (codelen + extra); 999 if (space < 0) { 1000 /* now that's what I call *compression*. */ 1001 m_freem(mret); 1002 return DECOMP_ERROR; 1003 } 1004 dmp = m; 1005 wptr = mtod(dmp, u_char *); 1006 } 1007 1008 /* 1009 * Decode this code and install it in the decompressed buffer. 1010 */ 1011 p = (wptr += codelen); 1012 while (finchar > LAST) { 1013 dictp = &db->dict[db->dict[finchar].cptr]; 1014 #ifdef DEBUG 1015 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1016 goto bad; 1017 #endif 1018 *--p = dictp->f.hs.suffix; 1019 finchar = dictp->f.hs.prefix; 1020 } 1021 *--p = finchar; 1022 1023 #ifdef DEBUG 1024 if (--codelen != 0) 1025 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1026 db->unit, codelen, incode, max_ent); 1027 #endif 1028 1029 if (extra) /* the KwKwK case again */ 1030 *wptr++ = finchar; 1031 1032 /* 1033 * If not first code in a packet, and 1034 * if not out of code space, then allocate a new code. 1035 * 1036 * Keep the hash table correct so it can be used 1037 * with uncompressed packets. 1038 */ 1039 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1040 struct bsd_dict *dictp2; 1041 u_int32_t fcode; 1042 u_int32_t hval, disp; 1043 1044 fcode = BSD_KEY(oldcode,finchar); 1045 hval = BSD_HASH(oldcode,finchar,db->hshift); 1046 dictp = &db->dict[hval]; 1047 1048 /* look for a free hash table entry */ 1049 if (dictp->codem1 < max_ent) { 1050 disp = (hval == 0) ? 1 : hval; 1051 do { 1052 hval += disp; 1053 if (hval >= db->hsize) 1054 hval -= db->hsize; 1055 dictp = &db->dict[hval]; 1056 } while (dictp->codem1 < max_ent); 1057 } 1058 1059 /* 1060 * Invalidate previous hash table entry 1061 * assigned this code, and then take it over 1062 */ 1063 dictp2 = &db->dict[max_ent+1]; 1064 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1065 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1066 } 1067 dictp2->cptr = hval; 1068 dictp->codem1 = max_ent; 1069 dictp->f.fcode = fcode; 1070 1071 db->max_ent = ++max_ent; 1072 db->lens[max_ent] = db->lens[oldcode]+1; 1073 1074 /* Expand code size if needed. */ 1075 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1076 db->n_bits = ++n_bits; 1077 tgtbitno = 32-n_bits; 1078 } 1079 } 1080 oldcode = incode; 1081 } 1082 dmp->m_len = wptr - mtod(dmp, u_char *); 1083 1084 /* 1085 * Keep the checkpoint right so that incompressible packets 1086 * clear the dictionary at the right times. 1087 */ 1088 db->bytes_out += ilen; 1089 db->in_count += explen; 1090 if (bsd_check(db) && db->debug) { 1091 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1092 db->unit); 1093 } 1094 1095 ++db->comp_count; 1096 db->comp_bytes += ilen + BSD_OVHD; 1097 ++db->uncomp_count; 1098 db->uncomp_bytes += explen; 1099 1100 *dmpp = mret; 1101 return DECOMP_OK; 1102 1103 #ifdef DEBUG 1104 bad: 1105 if (codelen <= 0) { 1106 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1107 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1108 incode, finchar, db->dict[finchar].cptr, max_ent); 1109 } else if (dictp->codem1 != finchar-1) { 1110 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1111 db->unit, incode, finchar); 1112 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1113 db->dict[finchar].cptr, dictp->codem1); 1114 } 1115 m_freem(mret); 1116 return DECOMP_FATALERROR; 1117 #endif /* DEBUG */ 1118 } 1119 #endif /* DO_BSD_COMPRESS */ 1120