1 /* $NetBSD: bsd-comp.c,v 1.11 2001/11/15 09:48:25 lukem Exp $ */ 2 /* Id: bsd-comp.c,v 1.6 1996/08/28 06:31:58 paulus Exp */ 3 4 /* Because this code is derived from the 4.3BSD compress source: 5 * 6 * 7 * Copyright (c) 1985, 1986 The Regents of the University of California. 8 * All rights reserved. 9 * 10 * This code is derived from software contributed to Berkeley by 11 * James A. Woods, derived from original work by Spencer Thomas 12 * and Joseph Orost. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. All advertising materials mentioning features or use of this software 23 * must display the following acknowledgement: 24 * This product includes software developed by the University of 25 * California, Berkeley and its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 */ 42 43 /* 44 * This version is for use with mbufs on BSD-derived systems. 45 */ 46 47 #include <sys/cdefs.h> 48 __KERNEL_RCSID(0, "$NetBSD: bsd-comp.c,v 1.11 2001/11/15 09:48:25 lukem Exp $"); 49 50 #include <sys/param.h> 51 #include <sys/systm.h> 52 #include <sys/mbuf.h> 53 #include <sys/socket.h> 54 #include <net/if.h> 55 #include <net/if_types.h> 56 #include <net/ppp_defs.h> 57 #include <net/if_ppp.h> 58 59 #define PACKETPTR struct mbuf * 60 #include <net/ppp-comp.h> 61 62 #if DO_BSD_COMPRESS 63 /* 64 * PPP "BSD compress" compression 65 * The differences between this compression and the classic BSD LZW 66 * source are obvious from the requirement that the classic code worked 67 * with files while this handles arbitrarily long streams that 68 * are broken into packets. They are: 69 * 70 * When the code size expands, a block of junk is not emitted by 71 * the compressor and not expected by the decompressor. 72 * 73 * New codes are not necessarily assigned every time an old 74 * code is output by the compressor. This is because a packet 75 * end forces a code to be emitted, but does not imply that a 76 * new sequence has been seen. 77 * 78 * The compression ratio is checked at the first end of a packet 79 * after the appropriate gap. Besides simplifying and speeding 80 * things up, this makes it more likely that the transmitter 81 * and receiver will agree when the dictionary is cleared when 82 * compression is not going well. 83 */ 84 85 /* 86 * A dictionary for doing BSD compress. 87 */ 88 struct bsd_db { 89 int totlen; /* length of this structure */ 90 u_int hsize; /* size of the hash table */ 91 u_char hshift; /* used in hash function */ 92 u_char n_bits; /* current bits/code */ 93 u_char maxbits; 94 u_char debug; 95 u_char unit; 96 u_int16_t seqno; /* sequence # of next packet */ 97 u_int hdrlen; /* header length to preallocate */ 98 u_int mru; 99 u_int maxmaxcode; /* largest valid code */ 100 u_int max_ent; /* largest code in use */ 101 u_int in_count; /* uncompressed bytes, aged */ 102 u_int bytes_out; /* compressed bytes, aged */ 103 u_int ratio; /* recent compression ratio */ 104 u_int checkpoint; /* when to next check the ratio */ 105 u_int clear_count; /* times dictionary cleared */ 106 u_int incomp_count; /* incompressible packets */ 107 u_int incomp_bytes; /* incompressible bytes */ 108 u_int uncomp_count; /* uncompressed packets */ 109 u_int uncomp_bytes; /* uncompressed bytes */ 110 u_int comp_count; /* compressed packets */ 111 u_int comp_bytes; /* compressed bytes */ 112 u_int16_t *lens; /* array of lengths of codes */ 113 struct bsd_dict { 114 union { /* hash value */ 115 u_int32_t fcode; 116 struct { 117 #if BYTE_ORDER == LITTLE_ENDIAN 118 u_int16_t prefix; /* preceding code */ 119 u_char suffix; /* last character of new code */ 120 u_char pad; 121 #else 122 u_char pad; 123 u_char suffix; /* last character of new code */ 124 u_int16_t prefix; /* preceding code */ 125 #endif 126 } hs; 127 } f; 128 u_int16_t codem1; /* output of hash table -1 */ 129 u_int16_t cptr; /* map code to hash table entry */ 130 } dict[1]; 131 }; 132 133 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 134 #define BSD_INIT_BITS BSD_MIN_BITS 135 136 static void *bsd_comp_alloc __P((u_char *options, int opt_len)); 137 static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); 138 static void bsd_free __P((void *state)); 139 static int bsd_comp_init __P((void *state, u_char *options, int opt_len, 140 int unit, int hdrlen, int debug)); 141 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, 142 int unit, int hdrlen, int mru, int debug)); 143 static int bsd_compress __P((void *state, struct mbuf **mret, 144 struct mbuf *mp, int slen, int maxolen)); 145 static void bsd_incomp __P((void *state, struct mbuf *dmsg)); 146 static int bsd_decompress __P((void *state, struct mbuf *cmp, 147 struct mbuf **dmpp)); 148 static void bsd_reset __P((void *state)); 149 static void bsd_comp_stats __P((void *state, struct compstat *stats)); 150 151 /* 152 * Procedures exported to if_ppp.c. 153 */ 154 struct compressor ppp_bsd_compress = { 155 CI_BSD_COMPRESS, /* compress_proto */ 156 bsd_comp_alloc, /* comp_alloc */ 157 bsd_free, /* comp_free */ 158 bsd_comp_init, /* comp_init */ 159 bsd_reset, /* comp_reset */ 160 bsd_compress, /* compress */ 161 bsd_comp_stats, /* comp_stat */ 162 bsd_decomp_alloc, /* decomp_alloc */ 163 bsd_free, /* decomp_free */ 164 bsd_decomp_init, /* decomp_init */ 165 bsd_reset, /* decomp_reset */ 166 bsd_decompress, /* decompress */ 167 bsd_incomp, /* incomp */ 168 bsd_comp_stats, /* decomp_stat */ 169 }; 170 171 /* 172 * the next two codes should not be changed lightly, as they must not 173 * lie within the contiguous general code space. 174 */ 175 #define CLEAR 256 /* table clear output code */ 176 #define FIRST 257 /* first free entry */ 177 #define LAST 255 178 179 #define MAXCODE(b) ((1 << (b)) - 1) 180 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 181 182 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 183 ^ (u_int32_t)(prefix)) 184 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 185 + (u_int32_t)(prefix)) 186 187 #define CHECK_GAP 10000 /* Ratio check interval */ 188 189 #define RATIO_SCALE_LOG 8 190 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 191 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 192 193 static void bsd_clear __P((struct bsd_db *)); 194 static int bsd_check __P((struct bsd_db *)); 195 static void *bsd_alloc __P((u_char *, int, int)); 196 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int, 197 int, int)); 198 199 /* 200 * clear the dictionary 201 */ 202 static void 203 bsd_clear(db) 204 struct bsd_db *db; 205 { 206 db->clear_count++; 207 db->max_ent = FIRST-1; 208 db->n_bits = BSD_INIT_BITS; 209 db->ratio = 0; 210 db->bytes_out = 0; 211 db->in_count = 0; 212 db->checkpoint = CHECK_GAP; 213 } 214 215 /* 216 * If the dictionary is full, then see if it is time to reset it. 217 * 218 * Compute the compression ratio using fixed-point arithmetic 219 * with 8 fractional bits. 220 * 221 * Since we have an infinite stream instead of a single file, 222 * watch only the local compression ratio. 223 * 224 * Since both peers must reset the dictionary at the same time even in 225 * the absence of CLEAR codes (while packets are incompressible), they 226 * must compute the same ratio. 227 */ 228 static int /* 1=output CLEAR */ 229 bsd_check(db) 230 struct bsd_db *db; 231 { 232 u_int new_ratio; 233 234 if (db->in_count >= db->checkpoint) { 235 /* age the ratio by limiting the size of the counts */ 236 if (db->in_count >= RATIO_MAX 237 || db->bytes_out >= RATIO_MAX) { 238 db->in_count -= db->in_count/4; 239 db->bytes_out -= db->bytes_out/4; 240 } 241 242 db->checkpoint = db->in_count + CHECK_GAP; 243 244 if (db->max_ent >= db->maxmaxcode) { 245 /* Reset the dictionary only if the ratio is worse, 246 * or if it looks as if it has been poisoned 247 * by incompressible data. 248 * 249 * This does not overflow, because 250 * db->in_count <= RATIO_MAX. 251 */ 252 new_ratio = db->in_count << RATIO_SCALE_LOG; 253 if (db->bytes_out != 0) 254 new_ratio /= db->bytes_out; 255 256 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 257 bsd_clear(db); 258 return 1; 259 } 260 db->ratio = new_ratio; 261 } 262 } 263 return 0; 264 } 265 266 /* 267 * Return statistics. 268 */ 269 static void 270 bsd_comp_stats(state, stats) 271 void *state; 272 struct compstat *stats; 273 { 274 struct bsd_db *db = (struct bsd_db *) state; 275 u_int out; 276 277 stats->unc_bytes = db->uncomp_bytes; 278 stats->unc_packets = db->uncomp_count; 279 stats->comp_bytes = db->comp_bytes; 280 stats->comp_packets = db->comp_count; 281 stats->inc_bytes = db->incomp_bytes; 282 stats->inc_packets = db->incomp_count; 283 stats->ratio = db->in_count; 284 out = db->bytes_out; 285 if (stats->ratio <= 0x7fffff) 286 stats->ratio <<= 8; 287 else 288 out >>= 8; 289 if (out != 0) 290 stats->ratio /= out; 291 } 292 293 /* 294 * Reset state, as on a CCP ResetReq. 295 */ 296 static void 297 bsd_reset(state) 298 void *state; 299 { 300 struct bsd_db *db = (struct bsd_db *) state; 301 302 db->seqno = 0; 303 bsd_clear(db); 304 db->clear_count = 0; 305 } 306 307 /* 308 * Allocate space for a (de) compressor. 309 */ 310 static void * 311 bsd_alloc(options, opt_len, decomp) 312 u_char *options; 313 int opt_len, decomp; 314 { 315 int bits; 316 u_int newlen, hsize, hshift, maxmaxcode; 317 struct bsd_db *db; 318 319 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 320 || options[1] != CILEN_BSD_COMPRESS 321 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 322 return NULL; 323 bits = BSD_NBITS(options[2]); 324 switch (bits) { 325 case 9: /* needs 82152 for both directions */ 326 case 10: /* needs 84144 */ 327 case 11: /* needs 88240 */ 328 case 12: /* needs 96432 */ 329 hsize = 5003; 330 hshift = 4; 331 break; 332 case 13: /* needs 176784 */ 333 hsize = 9001; 334 hshift = 5; 335 break; 336 case 14: /* needs 353744 */ 337 hsize = 18013; 338 hshift = 6; 339 break; 340 case 15: /* needs 691440 */ 341 hsize = 35023; 342 hshift = 7; 343 break; 344 case 16: /* needs 1366160--far too much, */ 345 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 346 /* hshift = 8; */ /* in struct bsd_db */ 347 /* break; */ 348 default: 349 return NULL; 350 } 351 352 maxmaxcode = MAXCODE(bits); 353 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 354 db = malloc(newlen, M_DEVBUF, M_NOWAIT); 355 if (!db) 356 return NULL; 357 memset(db, 0, sizeof(*db) - sizeof(db->dict)); 358 359 if (!decomp) { 360 db->lens = NULL; 361 } else { 362 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]), 363 M_DEVBUF, M_NOWAIT); 364 if (!db->lens) { 365 free(db, M_DEVBUF); 366 return NULL; 367 } 368 } 369 370 db->totlen = newlen; 371 db->hsize = hsize; 372 db->hshift = hshift; 373 db->maxmaxcode = maxmaxcode; 374 db->maxbits = bits; 375 376 return (void *) db; 377 } 378 379 static void 380 bsd_free(state) 381 void *state; 382 { 383 struct bsd_db *db = (struct bsd_db *) state; 384 385 if (db->lens) 386 free(db->lens, M_DEVBUF); 387 free(db, M_DEVBUF); 388 } 389 390 static void * 391 bsd_comp_alloc(options, opt_len) 392 u_char *options; 393 int opt_len; 394 { 395 return bsd_alloc(options, opt_len, 0); 396 } 397 398 static void * 399 bsd_decomp_alloc(options, opt_len) 400 u_char *options; 401 int opt_len; 402 { 403 return bsd_alloc(options, opt_len, 1); 404 } 405 406 /* 407 * Initialize the database. 408 */ 409 static int 410 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 411 struct bsd_db *db; 412 u_char *options; 413 int opt_len, unit, hdrlen, mru, debug, decomp; 414 { 415 int i; 416 417 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 418 || options[1] != CILEN_BSD_COMPRESS 419 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 420 || BSD_NBITS(options[2]) != db->maxbits 421 || (decomp && db->lens == NULL)) 422 return 0; 423 424 if (decomp) { 425 i = LAST+1; 426 while (i != 0) 427 db->lens[--i] = 1; 428 } 429 i = db->hsize; 430 while (i != 0) { 431 db->dict[--i].codem1 = BADCODEM1; 432 db->dict[i].cptr = 0; 433 } 434 435 db->unit = unit; 436 db->hdrlen = hdrlen; 437 db->mru = mru; 438 #ifndef DEBUG 439 if (debug) 440 #endif 441 db->debug = 1; 442 443 bsd_reset(db); 444 445 return 1; 446 } 447 448 static int 449 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 450 void *state; 451 u_char *options; 452 int opt_len, unit, hdrlen, debug; 453 { 454 return bsd_init((struct bsd_db *) state, options, opt_len, 455 unit, hdrlen, 0, debug, 0); 456 } 457 458 static int 459 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 460 void *state; 461 u_char *options; 462 int opt_len, unit, hdrlen, mru, debug; 463 { 464 return bsd_init((struct bsd_db *) state, options, opt_len, 465 unit, hdrlen, mru, debug, 1); 466 } 467 468 469 /* 470 * compress a packet 471 * One change from the BSD compress command is that when the 472 * code size expands, we do not output a bunch of padding. 473 */ 474 int /* new slen */ 475 bsd_compress(state, mret, mp, slen, maxolen) 476 void *state; 477 struct mbuf **mret; /* return compressed mbuf chain here */ 478 struct mbuf *mp; /* from here */ 479 int slen; /* uncompressed length */ 480 int maxolen; /* max compressed length */ 481 { 482 struct bsd_db *db = (struct bsd_db *) state; 483 int hshift = db->hshift; 484 u_int max_ent = db->max_ent; 485 u_int n_bits = db->n_bits; 486 u_int bitno = 32; 487 u_int32_t accm = 0, fcode; 488 struct bsd_dict *dictp; 489 u_char c; 490 int hval, disp, ent, ilen; 491 u_char *rptr, *wptr; 492 u_char *cp_end; 493 int olen; 494 struct mbuf *m; 495 496 #define PUTBYTE(v) { \ 497 ++olen; \ 498 if (wptr) { \ 499 *wptr++ = (v); \ 500 if (wptr >= cp_end) { \ 501 m->m_len = wptr - mtod(m, u_char *); \ 502 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 503 m = m->m_next; \ 504 if (m) { \ 505 m->m_len = 0; \ 506 if (maxolen - olen > MLEN) \ 507 MCLGET(m, M_DONTWAIT); \ 508 wptr = mtod(m, u_char *); \ 509 cp_end = wptr + M_TRAILINGSPACE(m); \ 510 } else \ 511 wptr = NULL; \ 512 } \ 513 } \ 514 } 515 516 #define OUTPUT(ent) { \ 517 bitno -= n_bits; \ 518 accm |= ((ent) << bitno); \ 519 do { \ 520 PUTBYTE(accm >> 24); \ 521 accm <<= 8; \ 522 bitno += 8; \ 523 } while (bitno <= 24); \ 524 } 525 526 /* 527 * If the protocol is not in the range we're interested in, 528 * just return without compressing the packet. If it is, 529 * the protocol becomes the first byte to compress. 530 */ 531 rptr = mtod(mp, u_char *); 532 ent = PPP_PROTOCOL(rptr); 533 if (ent < 0x21 || ent > 0xf9) { 534 *mret = NULL; 535 return slen; 536 } 537 538 /* Don't generate compressed packets which are larger than 539 the uncompressed packet. */ 540 if (maxolen > slen) 541 maxolen = slen; 542 543 /* Allocate one mbuf to start with. */ 544 MGET(m, M_DONTWAIT, MT_DATA); 545 *mret = m; 546 if (m != NULL) { 547 m->m_len = 0; 548 if (maxolen + db->hdrlen > MLEN) 549 MCLGET(m, M_DONTWAIT); 550 m->m_data += db->hdrlen; 551 wptr = mtod(m, u_char *); 552 cp_end = wptr + M_TRAILINGSPACE(m); 553 } else 554 wptr = cp_end = NULL; 555 556 /* 557 * Copy the PPP header over, changing the protocol, 558 * and install the 2-byte packet sequence number. 559 */ 560 if (wptr) { 561 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 562 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 563 *wptr++ = 0; /* change the protocol */ 564 *wptr++ = PPP_COMP; 565 *wptr++ = db->seqno >> 8; 566 *wptr++ = db->seqno; 567 } 568 ++db->seqno; 569 570 olen = 0; 571 rptr += PPP_HDRLEN; 572 slen = mp->m_len - PPP_HDRLEN; 573 ilen = slen + 1; 574 for (;;) { 575 if (slen <= 0) { 576 mp = mp->m_next; 577 if (!mp) 578 break; 579 rptr = mtod(mp, u_char *); 580 slen = mp->m_len; 581 if (!slen) 582 continue; /* handle 0-length buffers */ 583 ilen += slen; 584 } 585 586 slen--; 587 c = *rptr++; 588 fcode = BSD_KEY(ent, c); 589 hval = BSD_HASH(ent, c, hshift); 590 dictp = &db->dict[hval]; 591 592 /* Validate and then check the entry. */ 593 if (dictp->codem1 >= max_ent) 594 goto nomatch; 595 if (dictp->f.fcode == fcode) { 596 ent = dictp->codem1+1; 597 continue; /* found (prefix,suffix) */ 598 } 599 600 /* continue probing until a match or invalid entry */ 601 disp = (hval == 0) ? 1 : hval; 602 do { 603 hval += disp; 604 if (hval >= db->hsize) 605 hval -= db->hsize; 606 dictp = &db->dict[hval]; 607 if (dictp->codem1 >= max_ent) 608 goto nomatch; 609 } while (dictp->f.fcode != fcode); 610 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 611 continue; 612 613 nomatch: 614 OUTPUT(ent); /* output the prefix */ 615 616 /* code -> hashtable */ 617 if (max_ent < db->maxmaxcode) { 618 struct bsd_dict *dictp2; 619 /* expand code size if needed */ 620 if (max_ent >= MAXCODE(n_bits)) 621 db->n_bits = ++n_bits; 622 623 /* Invalidate old hash table entry using 624 * this code, and then take it over. 625 */ 626 dictp2 = &db->dict[max_ent+1]; 627 if (db->dict[dictp2->cptr].codem1 == max_ent) 628 db->dict[dictp2->cptr].codem1 = BADCODEM1; 629 dictp2->cptr = hval; 630 dictp->codem1 = max_ent; 631 dictp->f.fcode = fcode; 632 633 db->max_ent = ++max_ent; 634 } 635 ent = c; 636 } 637 638 OUTPUT(ent); /* output the last code */ 639 db->bytes_out += olen; 640 db->in_count += ilen; 641 if (bitno < 32) 642 ++db->bytes_out; /* count complete bytes */ 643 644 if (bsd_check(db)) 645 OUTPUT(CLEAR); /* do not count the CLEAR */ 646 647 /* 648 * Pad dribble bits of last code with ones. 649 * Do not emit a completely useless byte of ones. 650 */ 651 if (bitno != 32) 652 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 653 654 if (m != NULL) { 655 m->m_len = wptr - mtod(m, u_char *); 656 m->m_next = NULL; 657 } 658 659 /* 660 * Increase code size if we would have without the packet 661 * boundary and as the decompressor will. 662 */ 663 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 664 db->n_bits++; 665 666 db->uncomp_bytes += ilen; 667 ++db->uncomp_count; 668 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 669 /* throw away the compressed stuff if it is longer than uncompressed */ 670 if (*mret != NULL) { 671 m_freem(*mret); 672 *mret = NULL; 673 } 674 ++db->incomp_count; 675 db->incomp_bytes += ilen; 676 } else { 677 ++db->comp_count; 678 db->comp_bytes += olen + BSD_OVHD; 679 } 680 681 return olen + PPP_HDRLEN + BSD_OVHD; 682 #undef OUTPUT 683 #undef PUTBYTE 684 } 685 686 687 /* 688 * Update the "BSD Compress" dictionary on the receiver for 689 * incompressible data by pretending to compress the incoming data. 690 */ 691 static void 692 bsd_incomp(state, dmsg) 693 void *state; 694 struct mbuf *dmsg; 695 { 696 struct bsd_db *db = (struct bsd_db *) state; 697 u_int hshift = db->hshift; 698 u_int max_ent = db->max_ent; 699 u_int n_bits = db->n_bits; 700 struct bsd_dict *dictp; 701 u_int32_t fcode; 702 u_char c; 703 u_int32_t hval, disp; 704 int slen, ilen; 705 u_int bitno = 7; 706 u_char *rptr; 707 u_int ent; 708 709 /* 710 * If the protocol is not in the range we're interested in, 711 * just return without looking at the packet. If it is, 712 * the protocol becomes the first byte to "compress". 713 */ 714 rptr = mtod(dmsg, u_char *); 715 ent = PPP_PROTOCOL(rptr); 716 if (ent < 0x21 || ent > 0xf9) 717 return; 718 719 db->seqno++; 720 ilen = 1; /* count the protocol as 1 byte */ 721 rptr += PPP_HDRLEN; 722 slen = dmsg->m_len - PPP_HDRLEN; 723 for (;;) { 724 if (slen <= 0) { 725 dmsg = dmsg->m_next; 726 if (!dmsg) 727 break; 728 rptr = mtod(dmsg, u_char *); 729 slen = dmsg->m_len; 730 continue; 731 } 732 ilen += slen; 733 734 do { 735 c = *rptr++; 736 fcode = BSD_KEY(ent, c); 737 hval = BSD_HASH(ent, c, hshift); 738 dictp = &db->dict[hval]; 739 740 /* validate and then check the entry */ 741 if (dictp->codem1 >= max_ent) 742 goto nomatch; 743 if (dictp->f.fcode == fcode) { 744 ent = dictp->codem1+1; 745 continue; /* found (prefix,suffix) */ 746 } 747 748 /* continue probing until a match or invalid entry */ 749 disp = (hval == 0) ? 1 : hval; 750 do { 751 hval += disp; 752 if (hval >= db->hsize) 753 hval -= db->hsize; 754 dictp = &db->dict[hval]; 755 if (dictp->codem1 >= max_ent) 756 goto nomatch; 757 } while (dictp->f.fcode != fcode); 758 ent = dictp->codem1+1; 759 continue; /* finally found (prefix,suffix) */ 760 761 nomatch: /* output (count) the prefix */ 762 bitno += n_bits; 763 764 /* code -> hashtable */ 765 if (max_ent < db->maxmaxcode) { 766 struct bsd_dict *dictp2; 767 /* expand code size if needed */ 768 if (max_ent >= MAXCODE(n_bits)) 769 db->n_bits = ++n_bits; 770 771 /* Invalidate previous hash table entry 772 * assigned this code, and then take it over. 773 */ 774 dictp2 = &db->dict[max_ent+1]; 775 if (db->dict[dictp2->cptr].codem1 == max_ent) 776 db->dict[dictp2->cptr].codem1 = BADCODEM1; 777 dictp2->cptr = hval; 778 dictp->codem1 = max_ent; 779 dictp->f.fcode = fcode; 780 781 db->max_ent = ++max_ent; 782 db->lens[max_ent] = db->lens[ent]+1; 783 } 784 ent = c; 785 } while (--slen != 0); 786 } 787 bitno += n_bits; /* output (count) the last code */ 788 db->bytes_out += bitno/8; 789 db->in_count += ilen; 790 (void)bsd_check(db); 791 792 ++db->incomp_count; 793 db->incomp_bytes += ilen; 794 ++db->uncomp_count; 795 db->uncomp_bytes += ilen; 796 797 /* Increase code size if we would have without the packet 798 * boundary and as the decompressor will. 799 */ 800 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 801 db->n_bits++; 802 } 803 804 805 /* 806 * Decompress "BSD Compress". 807 * 808 * Because of patent problems, we return DECOMP_ERROR for errors 809 * found by inspecting the input data and for system problems, but 810 * DECOMP_FATALERROR for any errors which could possibly be said to 811 * be being detected "after" decompression. For DECOMP_ERROR, 812 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 813 * infringing a patent of Motorola's if we do, so we take CCP down 814 * instead. 815 * 816 * Given that the frame has the correct sequence number and a good FCS, 817 * errors such as invalid codes in the input most likely indicate a 818 * bug, so we return DECOMP_FATALERROR for them in order to turn off 819 * compression, even though they are detected by inspecting the input. 820 */ 821 int 822 bsd_decompress(state, cmp, dmpp) 823 void *state; 824 struct mbuf *cmp, **dmpp; 825 { 826 struct bsd_db *db = (struct bsd_db *) state; 827 u_int max_ent = db->max_ent; 828 u_int32_t accm = 0; 829 u_int bitno = 32; /* 1st valid bit in accm */ 830 u_int n_bits = db->n_bits; 831 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 832 struct bsd_dict *dictp; 833 int explen, i, seq, len; 834 u_int incode, oldcode, finchar; 835 u_char *p, *rptr, *wptr; 836 struct mbuf *m, *dmp, *mret; 837 int adrs, ctrl, ilen; 838 int space, codelen, extra; 839 840 /* 841 * Save the address/control from the PPP header 842 * and then get the sequence number. 843 */ 844 *dmpp = NULL; 845 rptr = mtod(cmp, u_char *); 846 adrs = PPP_ADDRESS(rptr); 847 ctrl = PPP_CONTROL(rptr); 848 rptr += PPP_HDRLEN; 849 len = cmp->m_len - PPP_HDRLEN; 850 seq = 0; 851 for (i = 0; i < 2; ++i) { 852 while (len <= 0) { 853 cmp = cmp->m_next; 854 if (cmp == NULL) 855 return DECOMP_ERROR; 856 rptr = mtod(cmp, u_char *); 857 len = cmp->m_len; 858 } 859 seq = (seq << 8) + *rptr++; 860 --len; 861 } 862 863 /* 864 * Check the sequence number and give up if it differs from 865 * the value we're expecting. 866 */ 867 if (seq != db->seqno) { 868 if (db->debug) 869 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 870 db->unit, seq, db->seqno - 1); 871 return DECOMP_ERROR; 872 } 873 ++db->seqno; 874 875 /* 876 * Allocate one mbuf to start with. 877 */ 878 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 879 if (dmp == NULL) 880 return DECOMP_ERROR; 881 mret = dmp; 882 dmp->m_len = 0; 883 dmp->m_next = NULL; 884 MCLGET(dmp, M_DONTWAIT); 885 dmp->m_data += db->hdrlen; 886 wptr = mtod(dmp, u_char *); 887 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 888 889 /* 890 * Fill in the ppp header, but not the last byte of the protocol 891 * (that comes from the decompressed data). 892 */ 893 wptr[0] = adrs; 894 wptr[1] = ctrl; 895 wptr[2] = 0; 896 wptr += PPP_HDRLEN - 1; 897 898 ilen = len; 899 oldcode = CLEAR; 900 explen = 0; 901 for (;;) { 902 if (len == 0) { 903 cmp = cmp->m_next; 904 if (!cmp) /* quit at end of message */ 905 break; 906 rptr = mtod(cmp, u_char *); 907 len = cmp->m_len; 908 ilen += len; 909 continue; /* handle 0-length buffers */ 910 } 911 912 /* 913 * Accumulate bytes until we have a complete code. 914 * Then get the next code, relying on the 32-bit, 915 * unsigned accm to mask the result. 916 */ 917 bitno -= 8; 918 accm |= *rptr++ << bitno; 919 --len; 920 if (tgtbitno < bitno) 921 continue; 922 incode = accm >> tgtbitno; 923 accm <<= n_bits; 924 bitno += n_bits; 925 926 if (incode == CLEAR) { 927 /* 928 * The dictionary must only be cleared at 929 * the end of a packet. But there could be an 930 * empty mbuf at the end. 931 */ 932 if (len > 0 || cmp->m_next != NULL) { 933 while ((cmp = cmp->m_next) != NULL) 934 len += cmp->m_len; 935 if (len > 0) { 936 m_freem(mret); 937 if (db->debug) 938 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 939 return DECOMP_FATALERROR; /* probably a bug */ 940 } 941 } 942 bsd_clear(db); 943 explen = ilen = 0; 944 break; 945 } 946 947 if (incode > max_ent + 2 || incode > db->maxmaxcode 948 || (incode > max_ent && oldcode == CLEAR)) { 949 m_freem(mret); 950 if (db->debug) { 951 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 952 db->unit, incode, oldcode); 953 printf("max_ent=0x%x explen=%d seqno=%d\n", 954 max_ent, explen, db->seqno); 955 } 956 return DECOMP_FATALERROR; /* probably a bug */ 957 } 958 959 /* Special case for KwKwK string. */ 960 if (incode > max_ent) { 961 finchar = oldcode; 962 extra = 1; 963 } else { 964 finchar = incode; 965 extra = 0; 966 } 967 968 codelen = db->lens[finchar]; 969 explen += codelen + extra; 970 if (explen > db->mru + 1) { 971 m_freem(mret); 972 if (db->debug) { 973 printf("bsd_decomp%d: ran out of mru\n", db->unit); 974 #ifdef DEBUG 975 while ((cmp = cmp->m_next) != NULL) 976 len += cmp->m_len; 977 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 978 len, finchar, codelen, explen); 979 #endif 980 } 981 return DECOMP_FATALERROR; 982 } 983 984 /* 985 * For simplicity, the decoded characters go in a single mbuf, 986 * so we allocate a single extra cluster mbuf if necessary. 987 */ 988 if ((space -= codelen + extra) < 0) { 989 dmp->m_len = wptr - mtod(dmp, u_char *); 990 MGET(m, M_DONTWAIT, MT_DATA); 991 if (m == NULL) { 992 m_freem(mret); 993 return DECOMP_ERROR; 994 } 995 m->m_len = 0; 996 m->m_next = NULL; 997 dmp->m_next = m; 998 MCLGET(m, M_DONTWAIT); 999 space = M_TRAILINGSPACE(m) - (codelen + extra); 1000 if (space < 0) { 1001 /* now that's what I call *compression*. */ 1002 m_freem(mret); 1003 return DECOMP_ERROR; 1004 } 1005 dmp = m; 1006 wptr = mtod(dmp, u_char *); 1007 } 1008 1009 /* 1010 * Decode this code and install it in the decompressed buffer. 1011 */ 1012 p = (wptr += codelen); 1013 while (finchar > LAST) { 1014 dictp = &db->dict[db->dict[finchar].cptr]; 1015 #ifdef DEBUG 1016 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1017 goto bad; 1018 #endif 1019 *--p = dictp->f.hs.suffix; 1020 finchar = dictp->f.hs.prefix; 1021 } 1022 *--p = finchar; 1023 1024 #ifdef DEBUG 1025 if (--codelen != 0) 1026 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1027 db->unit, codelen, incode, max_ent); 1028 #endif 1029 1030 if (extra) /* the KwKwK case again */ 1031 *wptr++ = finchar; 1032 1033 /* 1034 * If not first code in a packet, and 1035 * if not out of code space, then allocate a new code. 1036 * 1037 * Keep the hash table correct so it can be used 1038 * with uncompressed packets. 1039 */ 1040 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1041 struct bsd_dict *dictp2; 1042 u_int32_t fcode; 1043 u_int32_t hval, disp; 1044 1045 fcode = BSD_KEY(oldcode,finchar); 1046 hval = BSD_HASH(oldcode,finchar,db->hshift); 1047 dictp = &db->dict[hval]; 1048 1049 /* look for a free hash table entry */ 1050 if (dictp->codem1 < max_ent) { 1051 disp = (hval == 0) ? 1 : hval; 1052 do { 1053 hval += disp; 1054 if (hval >= db->hsize) 1055 hval -= db->hsize; 1056 dictp = &db->dict[hval]; 1057 } while (dictp->codem1 < max_ent); 1058 } 1059 1060 /* 1061 * Invalidate previous hash table entry 1062 * assigned this code, and then take it over 1063 */ 1064 dictp2 = &db->dict[max_ent+1]; 1065 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1066 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1067 } 1068 dictp2->cptr = hval; 1069 dictp->codem1 = max_ent; 1070 dictp->f.fcode = fcode; 1071 1072 db->max_ent = ++max_ent; 1073 db->lens[max_ent] = db->lens[oldcode]+1; 1074 1075 /* Expand code size if needed. */ 1076 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1077 db->n_bits = ++n_bits; 1078 tgtbitno = 32-n_bits; 1079 } 1080 } 1081 oldcode = incode; 1082 } 1083 dmp->m_len = wptr - mtod(dmp, u_char *); 1084 1085 /* 1086 * Keep the checkpoint right so that incompressible packets 1087 * clear the dictionary at the right times. 1088 */ 1089 db->bytes_out += ilen; 1090 db->in_count += explen; 1091 if (bsd_check(db) && db->debug) { 1092 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1093 db->unit); 1094 } 1095 1096 ++db->comp_count; 1097 db->comp_bytes += ilen + BSD_OVHD; 1098 ++db->uncomp_count; 1099 db->uncomp_bytes += explen; 1100 1101 *dmpp = mret; 1102 return DECOMP_OK; 1103 1104 #ifdef DEBUG 1105 bad: 1106 if (codelen <= 0) { 1107 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1108 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1109 incode, finchar, db->dict[finchar].cptr, max_ent); 1110 } else if (dictp->codem1 != finchar-1) { 1111 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1112 db->unit, incode, finchar); 1113 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1114 db->dict[finchar].cptr, dictp->codem1); 1115 } 1116 m_freem(mret); 1117 return DECOMP_FATALERROR; 1118 #endif /* DEBUG */ 1119 } 1120 #endif /* DO_BSD_COMPRESS */ 1121