1 /* $NetBSD: bsd-comp.c,v 1.10 2001/11/12 23:49:34 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 1.10 2001/11/12 23:49:34 lukem Exp $"); 49 50 #include <sys/param.h> 51 #include <sys/types.h> 52 #include <sys/systm.h> 53 #include <sys/mbuf.h> 54 #include <sys/socket.h> 55 #include <net/if.h> 56 #include <net/if_types.h> 57 #include <net/ppp_defs.h> 58 #include <net/if_ppp.h> 59 60 #define PACKETPTR struct mbuf * 61 #include <net/ppp-comp.h> 62 63 #if DO_BSD_COMPRESS 64 /* 65 * PPP "BSD compress" compression 66 * The differences between this compression and the classic BSD LZW 67 * source are obvious from the requirement that the classic code worked 68 * with files while this handles arbitrarily long streams that 69 * are broken into packets. They are: 70 * 71 * When the code size expands, a block of junk is not emitted by 72 * the compressor and not expected by the decompressor. 73 * 74 * New codes are not necessarily assigned every time an old 75 * code is output by the compressor. This is because a packet 76 * end forces a code to be emitted, but does not imply that a 77 * new sequence has been seen. 78 * 79 * The compression ratio is checked at the first end of a packet 80 * after the appropriate gap. Besides simplifying and speeding 81 * things up, this makes it more likely that the transmitter 82 * and receiver will agree when the dictionary is cleared when 83 * compression is not going well. 84 */ 85 86 /* 87 * A dictionary for doing BSD compress. 88 */ 89 struct bsd_db { 90 int totlen; /* length of this structure */ 91 u_int hsize; /* size of the hash table */ 92 u_char hshift; /* used in hash function */ 93 u_char n_bits; /* current bits/code */ 94 u_char maxbits; 95 u_char debug; 96 u_char unit; 97 u_int16_t seqno; /* sequence # of next packet */ 98 u_int hdrlen; /* header length to preallocate */ 99 u_int mru; 100 u_int maxmaxcode; /* largest valid code */ 101 u_int max_ent; /* largest code in use */ 102 u_int in_count; /* uncompressed bytes, aged */ 103 u_int bytes_out; /* compressed bytes, aged */ 104 u_int ratio; /* recent compression ratio */ 105 u_int checkpoint; /* when to next check the ratio */ 106 u_int clear_count; /* times dictionary cleared */ 107 u_int incomp_count; /* incompressible packets */ 108 u_int incomp_bytes; /* incompressible bytes */ 109 u_int uncomp_count; /* uncompressed packets */ 110 u_int uncomp_bytes; /* uncompressed bytes */ 111 u_int comp_count; /* compressed packets */ 112 u_int comp_bytes; /* compressed bytes */ 113 u_int16_t *lens; /* array of lengths of codes */ 114 struct bsd_dict { 115 union { /* hash value */ 116 u_int32_t fcode; 117 struct { 118 #if BYTE_ORDER == LITTLE_ENDIAN 119 u_int16_t prefix; /* preceding code */ 120 u_char suffix; /* last character of new code */ 121 u_char pad; 122 #else 123 u_char pad; 124 u_char suffix; /* last character of new code */ 125 u_int16_t prefix; /* preceding code */ 126 #endif 127 } hs; 128 } f; 129 u_int16_t codem1; /* output of hash table -1 */ 130 u_int16_t cptr; /* map code to hash table entry */ 131 } dict[1]; 132 }; 133 134 #define BSD_OVHD 2 /* BSD compress overhead/packet */ 135 #define BSD_INIT_BITS BSD_MIN_BITS 136 137 static void *bsd_comp_alloc __P((u_char *options, int opt_len)); 138 static void *bsd_decomp_alloc __P((u_char *options, int opt_len)); 139 static void bsd_free __P((void *state)); 140 static int bsd_comp_init __P((void *state, u_char *options, int opt_len, 141 int unit, int hdrlen, int debug)); 142 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len, 143 int unit, int hdrlen, int mru, int debug)); 144 static int bsd_compress __P((void *state, struct mbuf **mret, 145 struct mbuf *mp, int slen, int maxolen)); 146 static void bsd_incomp __P((void *state, struct mbuf *dmsg)); 147 static int bsd_decompress __P((void *state, struct mbuf *cmp, 148 struct mbuf **dmpp)); 149 static void bsd_reset __P((void *state)); 150 static void bsd_comp_stats __P((void *state, struct compstat *stats)); 151 152 /* 153 * Procedures exported to if_ppp.c. 154 */ 155 struct compressor ppp_bsd_compress = { 156 CI_BSD_COMPRESS, /* compress_proto */ 157 bsd_comp_alloc, /* comp_alloc */ 158 bsd_free, /* comp_free */ 159 bsd_comp_init, /* comp_init */ 160 bsd_reset, /* comp_reset */ 161 bsd_compress, /* compress */ 162 bsd_comp_stats, /* comp_stat */ 163 bsd_decomp_alloc, /* decomp_alloc */ 164 bsd_free, /* decomp_free */ 165 bsd_decomp_init, /* decomp_init */ 166 bsd_reset, /* decomp_reset */ 167 bsd_decompress, /* decompress */ 168 bsd_incomp, /* incomp */ 169 bsd_comp_stats, /* decomp_stat */ 170 }; 171 172 /* 173 * the next two codes should not be changed lightly, as they must not 174 * lie within the contiguous general code space. 175 */ 176 #define CLEAR 256 /* table clear output code */ 177 #define FIRST 257 /* first free entry */ 178 #define LAST 255 179 180 #define MAXCODE(b) ((1 << (b)) - 1) 181 #define BADCODEM1 MAXCODE(BSD_MAX_BITS) 182 183 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ 184 ^ (u_int32_t)(prefix)) 185 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ 186 + (u_int32_t)(prefix)) 187 188 #define CHECK_GAP 10000 /* Ratio check interval */ 189 190 #define RATIO_SCALE_LOG 8 191 #define RATIO_SCALE (1<<RATIO_SCALE_LOG) 192 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG) 193 194 static void bsd_clear __P((struct bsd_db *)); 195 static int bsd_check __P((struct bsd_db *)); 196 static void *bsd_alloc __P((u_char *, int, int)); 197 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int, 198 int, int)); 199 200 /* 201 * clear the dictionary 202 */ 203 static void 204 bsd_clear(db) 205 struct bsd_db *db; 206 { 207 db->clear_count++; 208 db->max_ent = FIRST-1; 209 db->n_bits = BSD_INIT_BITS; 210 db->ratio = 0; 211 db->bytes_out = 0; 212 db->in_count = 0; 213 db->checkpoint = CHECK_GAP; 214 } 215 216 /* 217 * If the dictionary is full, then see if it is time to reset it. 218 * 219 * Compute the compression ratio using fixed-point arithmetic 220 * with 8 fractional bits. 221 * 222 * Since we have an infinite stream instead of a single file, 223 * watch only the local compression ratio. 224 * 225 * Since both peers must reset the dictionary at the same time even in 226 * the absence of CLEAR codes (while packets are incompressible), they 227 * must compute the same ratio. 228 */ 229 static int /* 1=output CLEAR */ 230 bsd_check(db) 231 struct bsd_db *db; 232 { 233 u_int new_ratio; 234 235 if (db->in_count >= db->checkpoint) { 236 /* age the ratio by limiting the size of the counts */ 237 if (db->in_count >= RATIO_MAX 238 || db->bytes_out >= RATIO_MAX) { 239 db->in_count -= db->in_count/4; 240 db->bytes_out -= db->bytes_out/4; 241 } 242 243 db->checkpoint = db->in_count + CHECK_GAP; 244 245 if (db->max_ent >= db->maxmaxcode) { 246 /* Reset the dictionary only if the ratio is worse, 247 * or if it looks as if it has been poisoned 248 * by incompressible data. 249 * 250 * This does not overflow, because 251 * db->in_count <= RATIO_MAX. 252 */ 253 new_ratio = db->in_count << RATIO_SCALE_LOG; 254 if (db->bytes_out != 0) 255 new_ratio /= db->bytes_out; 256 257 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) { 258 bsd_clear(db); 259 return 1; 260 } 261 db->ratio = new_ratio; 262 } 263 } 264 return 0; 265 } 266 267 /* 268 * Return statistics. 269 */ 270 static void 271 bsd_comp_stats(state, stats) 272 void *state; 273 struct compstat *stats; 274 { 275 struct bsd_db *db = (struct bsd_db *) state; 276 u_int out; 277 278 stats->unc_bytes = db->uncomp_bytes; 279 stats->unc_packets = db->uncomp_count; 280 stats->comp_bytes = db->comp_bytes; 281 stats->comp_packets = db->comp_count; 282 stats->inc_bytes = db->incomp_bytes; 283 stats->inc_packets = db->incomp_count; 284 stats->ratio = db->in_count; 285 out = db->bytes_out; 286 if (stats->ratio <= 0x7fffff) 287 stats->ratio <<= 8; 288 else 289 out >>= 8; 290 if (out != 0) 291 stats->ratio /= out; 292 } 293 294 /* 295 * Reset state, as on a CCP ResetReq. 296 */ 297 static void 298 bsd_reset(state) 299 void *state; 300 { 301 struct bsd_db *db = (struct bsd_db *) state; 302 303 db->seqno = 0; 304 bsd_clear(db); 305 db->clear_count = 0; 306 } 307 308 /* 309 * Allocate space for a (de) compressor. 310 */ 311 static void * 312 bsd_alloc(options, opt_len, decomp) 313 u_char *options; 314 int opt_len, decomp; 315 { 316 int bits; 317 u_int newlen, hsize, hshift, maxmaxcode; 318 struct bsd_db *db; 319 320 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 321 || options[1] != CILEN_BSD_COMPRESS 322 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION) 323 return NULL; 324 bits = BSD_NBITS(options[2]); 325 switch (bits) { 326 case 9: /* needs 82152 for both directions */ 327 case 10: /* needs 84144 */ 328 case 11: /* needs 88240 */ 329 case 12: /* needs 96432 */ 330 hsize = 5003; 331 hshift = 4; 332 break; 333 case 13: /* needs 176784 */ 334 hsize = 9001; 335 hshift = 5; 336 break; 337 case 14: /* needs 353744 */ 338 hsize = 18013; 339 hshift = 6; 340 break; 341 case 15: /* needs 691440 */ 342 hsize = 35023; 343 hshift = 7; 344 break; 345 case 16: /* needs 1366160--far too much, */ 346 /* hsize = 69001; */ /* and 69001 is too big for cptr */ 347 /* hshift = 8; */ /* in struct bsd_db */ 348 /* break; */ 349 default: 350 return NULL; 351 } 352 353 maxmaxcode = MAXCODE(bits); 354 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0])); 355 db = malloc(newlen, M_DEVBUF, M_NOWAIT); 356 if (!db) 357 return NULL; 358 memset(db, 0, sizeof(*db) - sizeof(db->dict)); 359 360 if (!decomp) { 361 db->lens = NULL; 362 } else { 363 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]), 364 M_DEVBUF, M_NOWAIT); 365 if (!db->lens) { 366 free(db, M_DEVBUF); 367 return NULL; 368 } 369 } 370 371 db->totlen = newlen; 372 db->hsize = hsize; 373 db->hshift = hshift; 374 db->maxmaxcode = maxmaxcode; 375 db->maxbits = bits; 376 377 return (void *) db; 378 } 379 380 static void 381 bsd_free(state) 382 void *state; 383 { 384 struct bsd_db *db = (struct bsd_db *) state; 385 386 if (db->lens) 387 free(db->lens, M_DEVBUF); 388 free(db, M_DEVBUF); 389 } 390 391 static void * 392 bsd_comp_alloc(options, opt_len) 393 u_char *options; 394 int opt_len; 395 { 396 return bsd_alloc(options, opt_len, 0); 397 } 398 399 static void * 400 bsd_decomp_alloc(options, opt_len) 401 u_char *options; 402 int opt_len; 403 { 404 return bsd_alloc(options, opt_len, 1); 405 } 406 407 /* 408 * Initialize the database. 409 */ 410 static int 411 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp) 412 struct bsd_db *db; 413 u_char *options; 414 int opt_len, unit, hdrlen, mru, debug, decomp; 415 { 416 int i; 417 418 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS 419 || options[1] != CILEN_BSD_COMPRESS 420 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION 421 || BSD_NBITS(options[2]) != db->maxbits 422 || (decomp && db->lens == NULL)) 423 return 0; 424 425 if (decomp) { 426 i = LAST+1; 427 while (i != 0) 428 db->lens[--i] = 1; 429 } 430 i = db->hsize; 431 while (i != 0) { 432 db->dict[--i].codem1 = BADCODEM1; 433 db->dict[i].cptr = 0; 434 } 435 436 db->unit = unit; 437 db->hdrlen = hdrlen; 438 db->mru = mru; 439 #ifndef DEBUG 440 if (debug) 441 #endif 442 db->debug = 1; 443 444 bsd_reset(db); 445 446 return 1; 447 } 448 449 static int 450 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug) 451 void *state; 452 u_char *options; 453 int opt_len, unit, hdrlen, debug; 454 { 455 return bsd_init((struct bsd_db *) state, options, opt_len, 456 unit, hdrlen, 0, debug, 0); 457 } 458 459 static int 460 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug) 461 void *state; 462 u_char *options; 463 int opt_len, unit, hdrlen, mru, debug; 464 { 465 return bsd_init((struct bsd_db *) state, options, opt_len, 466 unit, hdrlen, mru, debug, 1); 467 } 468 469 470 /* 471 * compress a packet 472 * One change from the BSD compress command is that when the 473 * code size expands, we do not output a bunch of padding. 474 */ 475 int /* new slen */ 476 bsd_compress(state, mret, mp, slen, maxolen) 477 void *state; 478 struct mbuf **mret; /* return compressed mbuf chain here */ 479 struct mbuf *mp; /* from here */ 480 int slen; /* uncompressed length */ 481 int maxolen; /* max compressed length */ 482 { 483 struct bsd_db *db = (struct bsd_db *) state; 484 int hshift = db->hshift; 485 u_int max_ent = db->max_ent; 486 u_int n_bits = db->n_bits; 487 u_int bitno = 32; 488 u_int32_t accm = 0, fcode; 489 struct bsd_dict *dictp; 490 u_char c; 491 int hval, disp, ent, ilen; 492 u_char *rptr, *wptr; 493 u_char *cp_end; 494 int olen; 495 struct mbuf *m; 496 497 #define PUTBYTE(v) { \ 498 ++olen; \ 499 if (wptr) { \ 500 *wptr++ = (v); \ 501 if (wptr >= cp_end) { \ 502 m->m_len = wptr - mtod(m, u_char *); \ 503 MGET(m->m_next, M_DONTWAIT, MT_DATA); \ 504 m = m->m_next; \ 505 if (m) { \ 506 m->m_len = 0; \ 507 if (maxolen - olen > MLEN) \ 508 MCLGET(m, M_DONTWAIT); \ 509 wptr = mtod(m, u_char *); \ 510 cp_end = wptr + M_TRAILINGSPACE(m); \ 511 } else \ 512 wptr = NULL; \ 513 } \ 514 } \ 515 } 516 517 #define OUTPUT(ent) { \ 518 bitno -= n_bits; \ 519 accm |= ((ent) << bitno); \ 520 do { \ 521 PUTBYTE(accm >> 24); \ 522 accm <<= 8; \ 523 bitno += 8; \ 524 } while (bitno <= 24); \ 525 } 526 527 /* 528 * If the protocol is not in the range we're interested in, 529 * just return without compressing the packet. If it is, 530 * the protocol becomes the first byte to compress. 531 */ 532 rptr = mtod(mp, u_char *); 533 ent = PPP_PROTOCOL(rptr); 534 if (ent < 0x21 || ent > 0xf9) { 535 *mret = NULL; 536 return slen; 537 } 538 539 /* Don't generate compressed packets which are larger than 540 the uncompressed packet. */ 541 if (maxolen > slen) 542 maxolen = slen; 543 544 /* Allocate one mbuf to start with. */ 545 MGET(m, M_DONTWAIT, MT_DATA); 546 *mret = m; 547 if (m != NULL) { 548 m->m_len = 0; 549 if (maxolen + db->hdrlen > MLEN) 550 MCLGET(m, M_DONTWAIT); 551 m->m_data += db->hdrlen; 552 wptr = mtod(m, u_char *); 553 cp_end = wptr + M_TRAILINGSPACE(m); 554 } else 555 wptr = cp_end = NULL; 556 557 /* 558 * Copy the PPP header over, changing the protocol, 559 * and install the 2-byte packet sequence number. 560 */ 561 if (wptr) { 562 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */ 563 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */ 564 *wptr++ = 0; /* change the protocol */ 565 *wptr++ = PPP_COMP; 566 *wptr++ = db->seqno >> 8; 567 *wptr++ = db->seqno; 568 } 569 ++db->seqno; 570 571 olen = 0; 572 rptr += PPP_HDRLEN; 573 slen = mp->m_len - PPP_HDRLEN; 574 ilen = slen + 1; 575 for (;;) { 576 if (slen <= 0) { 577 mp = mp->m_next; 578 if (!mp) 579 break; 580 rptr = mtod(mp, u_char *); 581 slen = mp->m_len; 582 if (!slen) 583 continue; /* handle 0-length buffers */ 584 ilen += slen; 585 } 586 587 slen--; 588 c = *rptr++; 589 fcode = BSD_KEY(ent, c); 590 hval = BSD_HASH(ent, c, hshift); 591 dictp = &db->dict[hval]; 592 593 /* Validate and then check the entry. */ 594 if (dictp->codem1 >= max_ent) 595 goto nomatch; 596 if (dictp->f.fcode == fcode) { 597 ent = dictp->codem1+1; 598 continue; /* found (prefix,suffix) */ 599 } 600 601 /* continue probing until a match or invalid entry */ 602 disp = (hval == 0) ? 1 : hval; 603 do { 604 hval += disp; 605 if (hval >= db->hsize) 606 hval -= db->hsize; 607 dictp = &db->dict[hval]; 608 if (dictp->codem1 >= max_ent) 609 goto nomatch; 610 } while (dictp->f.fcode != fcode); 611 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */ 612 continue; 613 614 nomatch: 615 OUTPUT(ent); /* output the prefix */ 616 617 /* code -> hashtable */ 618 if (max_ent < db->maxmaxcode) { 619 struct bsd_dict *dictp2; 620 /* expand code size if needed */ 621 if (max_ent >= MAXCODE(n_bits)) 622 db->n_bits = ++n_bits; 623 624 /* Invalidate old hash table entry using 625 * this code, and then take it over. 626 */ 627 dictp2 = &db->dict[max_ent+1]; 628 if (db->dict[dictp2->cptr].codem1 == max_ent) 629 db->dict[dictp2->cptr].codem1 = BADCODEM1; 630 dictp2->cptr = hval; 631 dictp->codem1 = max_ent; 632 dictp->f.fcode = fcode; 633 634 db->max_ent = ++max_ent; 635 } 636 ent = c; 637 } 638 639 OUTPUT(ent); /* output the last code */ 640 db->bytes_out += olen; 641 db->in_count += ilen; 642 if (bitno < 32) 643 ++db->bytes_out; /* count complete bytes */ 644 645 if (bsd_check(db)) 646 OUTPUT(CLEAR); /* do not count the CLEAR */ 647 648 /* 649 * Pad dribble bits of last code with ones. 650 * Do not emit a completely useless byte of ones. 651 */ 652 if (bitno != 32) 653 PUTBYTE((accm | (0xff << (bitno-8))) >> 24); 654 655 if (m != NULL) { 656 m->m_len = wptr - mtod(m, u_char *); 657 m->m_next = NULL; 658 } 659 660 /* 661 * Increase code size if we would have without the packet 662 * boundary and as the decompressor will. 663 */ 664 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 665 db->n_bits++; 666 667 db->uncomp_bytes += ilen; 668 ++db->uncomp_count; 669 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) { 670 /* throw away the compressed stuff if it is longer than uncompressed */ 671 if (*mret != NULL) { 672 m_freem(*mret); 673 *mret = NULL; 674 } 675 ++db->incomp_count; 676 db->incomp_bytes += ilen; 677 } else { 678 ++db->comp_count; 679 db->comp_bytes += olen + BSD_OVHD; 680 } 681 682 return olen + PPP_HDRLEN + BSD_OVHD; 683 #undef OUTPUT 684 #undef PUTBYTE 685 } 686 687 688 /* 689 * Update the "BSD Compress" dictionary on the receiver for 690 * incompressible data by pretending to compress the incoming data. 691 */ 692 static void 693 bsd_incomp(state, dmsg) 694 void *state; 695 struct mbuf *dmsg; 696 { 697 struct bsd_db *db = (struct bsd_db *) state; 698 u_int hshift = db->hshift; 699 u_int max_ent = db->max_ent; 700 u_int n_bits = db->n_bits; 701 struct bsd_dict *dictp; 702 u_int32_t fcode; 703 u_char c; 704 u_int32_t hval, disp; 705 int slen, ilen; 706 u_int bitno = 7; 707 u_char *rptr; 708 u_int ent; 709 710 /* 711 * If the protocol is not in the range we're interested in, 712 * just return without looking at the packet. If it is, 713 * the protocol becomes the first byte to "compress". 714 */ 715 rptr = mtod(dmsg, u_char *); 716 ent = PPP_PROTOCOL(rptr); 717 if (ent < 0x21 || ent > 0xf9) 718 return; 719 720 db->seqno++; 721 ilen = 1; /* count the protocol as 1 byte */ 722 rptr += PPP_HDRLEN; 723 slen = dmsg->m_len - PPP_HDRLEN; 724 for (;;) { 725 if (slen <= 0) { 726 dmsg = dmsg->m_next; 727 if (!dmsg) 728 break; 729 rptr = mtod(dmsg, u_char *); 730 slen = dmsg->m_len; 731 continue; 732 } 733 ilen += slen; 734 735 do { 736 c = *rptr++; 737 fcode = BSD_KEY(ent, c); 738 hval = BSD_HASH(ent, c, hshift); 739 dictp = &db->dict[hval]; 740 741 /* validate and then check the entry */ 742 if (dictp->codem1 >= max_ent) 743 goto nomatch; 744 if (dictp->f.fcode == fcode) { 745 ent = dictp->codem1+1; 746 continue; /* found (prefix,suffix) */ 747 } 748 749 /* continue probing until a match or invalid entry */ 750 disp = (hval == 0) ? 1 : hval; 751 do { 752 hval += disp; 753 if (hval >= db->hsize) 754 hval -= db->hsize; 755 dictp = &db->dict[hval]; 756 if (dictp->codem1 >= max_ent) 757 goto nomatch; 758 } while (dictp->f.fcode != fcode); 759 ent = dictp->codem1+1; 760 continue; /* finally found (prefix,suffix) */ 761 762 nomatch: /* output (count) the prefix */ 763 bitno += n_bits; 764 765 /* code -> hashtable */ 766 if (max_ent < db->maxmaxcode) { 767 struct bsd_dict *dictp2; 768 /* expand code size if needed */ 769 if (max_ent >= MAXCODE(n_bits)) 770 db->n_bits = ++n_bits; 771 772 /* Invalidate previous hash table entry 773 * assigned this code, and then take it over. 774 */ 775 dictp2 = &db->dict[max_ent+1]; 776 if (db->dict[dictp2->cptr].codem1 == max_ent) 777 db->dict[dictp2->cptr].codem1 = BADCODEM1; 778 dictp2->cptr = hval; 779 dictp->codem1 = max_ent; 780 dictp->f.fcode = fcode; 781 782 db->max_ent = ++max_ent; 783 db->lens[max_ent] = db->lens[ent]+1; 784 } 785 ent = c; 786 } while (--slen != 0); 787 } 788 bitno += n_bits; /* output (count) the last code */ 789 db->bytes_out += bitno/8; 790 db->in_count += ilen; 791 (void)bsd_check(db); 792 793 ++db->incomp_count; 794 db->incomp_bytes += ilen; 795 ++db->uncomp_count; 796 db->uncomp_bytes += ilen; 797 798 /* Increase code size if we would have without the packet 799 * boundary and as the decompressor will. 800 */ 801 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) 802 db->n_bits++; 803 } 804 805 806 /* 807 * Decompress "BSD Compress". 808 * 809 * Because of patent problems, we return DECOMP_ERROR for errors 810 * found by inspecting the input data and for system problems, but 811 * DECOMP_FATALERROR for any errors which could possibly be said to 812 * be being detected "after" decompression. For DECOMP_ERROR, 813 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be 814 * infringing a patent of Motorola's if we do, so we take CCP down 815 * instead. 816 * 817 * Given that the frame has the correct sequence number and a good FCS, 818 * errors such as invalid codes in the input most likely indicate a 819 * bug, so we return DECOMP_FATALERROR for them in order to turn off 820 * compression, even though they are detected by inspecting the input. 821 */ 822 int 823 bsd_decompress(state, cmp, dmpp) 824 void *state; 825 struct mbuf *cmp, **dmpp; 826 { 827 struct bsd_db *db = (struct bsd_db *) state; 828 u_int max_ent = db->max_ent; 829 u_int32_t accm = 0; 830 u_int bitno = 32; /* 1st valid bit in accm */ 831 u_int n_bits = db->n_bits; 832 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */ 833 struct bsd_dict *dictp; 834 int explen, i, seq, len; 835 u_int incode, oldcode, finchar; 836 u_char *p, *rptr, *wptr; 837 struct mbuf *m, *dmp, *mret; 838 int adrs, ctrl, ilen; 839 int space, codelen, extra; 840 841 /* 842 * Save the address/control from the PPP header 843 * and then get the sequence number. 844 */ 845 *dmpp = NULL; 846 rptr = mtod(cmp, u_char *); 847 adrs = PPP_ADDRESS(rptr); 848 ctrl = PPP_CONTROL(rptr); 849 rptr += PPP_HDRLEN; 850 len = cmp->m_len - PPP_HDRLEN; 851 seq = 0; 852 for (i = 0; i < 2; ++i) { 853 while (len <= 0) { 854 cmp = cmp->m_next; 855 if (cmp == NULL) 856 return DECOMP_ERROR; 857 rptr = mtod(cmp, u_char *); 858 len = cmp->m_len; 859 } 860 seq = (seq << 8) + *rptr++; 861 --len; 862 } 863 864 /* 865 * Check the sequence number and give up if it differs from 866 * the value we're expecting. 867 */ 868 if (seq != db->seqno) { 869 if (db->debug) 870 printf("bsd_decomp%d: bad sequence # %d, expected %d\n", 871 db->unit, seq, db->seqno - 1); 872 return DECOMP_ERROR; 873 } 874 ++db->seqno; 875 876 /* 877 * Allocate one mbuf to start with. 878 */ 879 MGETHDR(dmp, M_DONTWAIT, MT_DATA); 880 if (dmp == NULL) 881 return DECOMP_ERROR; 882 mret = dmp; 883 dmp->m_len = 0; 884 dmp->m_next = NULL; 885 MCLGET(dmp, M_DONTWAIT); 886 dmp->m_data += db->hdrlen; 887 wptr = mtod(dmp, u_char *); 888 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1; 889 890 /* 891 * Fill in the ppp header, but not the last byte of the protocol 892 * (that comes from the decompressed data). 893 */ 894 wptr[0] = adrs; 895 wptr[1] = ctrl; 896 wptr[2] = 0; 897 wptr += PPP_HDRLEN - 1; 898 899 ilen = len; 900 oldcode = CLEAR; 901 explen = 0; 902 for (;;) { 903 if (len == 0) { 904 cmp = cmp->m_next; 905 if (!cmp) /* quit at end of message */ 906 break; 907 rptr = mtod(cmp, u_char *); 908 len = cmp->m_len; 909 ilen += len; 910 continue; /* handle 0-length buffers */ 911 } 912 913 /* 914 * Accumulate bytes until we have a complete code. 915 * Then get the next code, relying on the 32-bit, 916 * unsigned accm to mask the result. 917 */ 918 bitno -= 8; 919 accm |= *rptr++ << bitno; 920 --len; 921 if (tgtbitno < bitno) 922 continue; 923 incode = accm >> tgtbitno; 924 accm <<= n_bits; 925 bitno += n_bits; 926 927 if (incode == CLEAR) { 928 /* 929 * The dictionary must only be cleared at 930 * the end of a packet. But there could be an 931 * empty mbuf at the end. 932 */ 933 if (len > 0 || cmp->m_next != NULL) { 934 while ((cmp = cmp->m_next) != NULL) 935 len += cmp->m_len; 936 if (len > 0) { 937 m_freem(mret); 938 if (db->debug) 939 printf("bsd_decomp%d: bad CLEAR\n", db->unit); 940 return DECOMP_FATALERROR; /* probably a bug */ 941 } 942 } 943 bsd_clear(db); 944 explen = ilen = 0; 945 break; 946 } 947 948 if (incode > max_ent + 2 || incode > db->maxmaxcode 949 || (incode > max_ent && oldcode == CLEAR)) { 950 m_freem(mret); 951 if (db->debug) { 952 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ", 953 db->unit, incode, oldcode); 954 printf("max_ent=0x%x explen=%d seqno=%d\n", 955 max_ent, explen, db->seqno); 956 } 957 return DECOMP_FATALERROR; /* probably a bug */ 958 } 959 960 /* Special case for KwKwK string. */ 961 if (incode > max_ent) { 962 finchar = oldcode; 963 extra = 1; 964 } else { 965 finchar = incode; 966 extra = 0; 967 } 968 969 codelen = db->lens[finchar]; 970 explen += codelen + extra; 971 if (explen > db->mru + 1) { 972 m_freem(mret); 973 if (db->debug) { 974 printf("bsd_decomp%d: ran out of mru\n", db->unit); 975 #ifdef DEBUG 976 while ((cmp = cmp->m_next) != NULL) 977 len += cmp->m_len; 978 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n", 979 len, finchar, codelen, explen); 980 #endif 981 } 982 return DECOMP_FATALERROR; 983 } 984 985 /* 986 * For simplicity, the decoded characters go in a single mbuf, 987 * so we allocate a single extra cluster mbuf if necessary. 988 */ 989 if ((space -= codelen + extra) < 0) { 990 dmp->m_len = wptr - mtod(dmp, u_char *); 991 MGET(m, M_DONTWAIT, MT_DATA); 992 if (m == NULL) { 993 m_freem(mret); 994 return DECOMP_ERROR; 995 } 996 m->m_len = 0; 997 m->m_next = NULL; 998 dmp->m_next = m; 999 MCLGET(m, M_DONTWAIT); 1000 space = M_TRAILINGSPACE(m) - (codelen + extra); 1001 if (space < 0) { 1002 /* now that's what I call *compression*. */ 1003 m_freem(mret); 1004 return DECOMP_ERROR; 1005 } 1006 dmp = m; 1007 wptr = mtod(dmp, u_char *); 1008 } 1009 1010 /* 1011 * Decode this code and install it in the decompressed buffer. 1012 */ 1013 p = (wptr += codelen); 1014 while (finchar > LAST) { 1015 dictp = &db->dict[db->dict[finchar].cptr]; 1016 #ifdef DEBUG 1017 if (--codelen <= 0 || dictp->codem1 != finchar-1) 1018 goto bad; 1019 #endif 1020 *--p = dictp->f.hs.suffix; 1021 finchar = dictp->f.hs.prefix; 1022 } 1023 *--p = finchar; 1024 1025 #ifdef DEBUG 1026 if (--codelen != 0) 1027 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", 1028 db->unit, codelen, incode, max_ent); 1029 #endif 1030 1031 if (extra) /* the KwKwK case again */ 1032 *wptr++ = finchar; 1033 1034 /* 1035 * If not first code in a packet, and 1036 * if not out of code space, then allocate a new code. 1037 * 1038 * Keep the hash table correct so it can be used 1039 * with uncompressed packets. 1040 */ 1041 if (oldcode != CLEAR && max_ent < db->maxmaxcode) { 1042 struct bsd_dict *dictp2; 1043 u_int32_t fcode; 1044 u_int32_t hval, disp; 1045 1046 fcode = BSD_KEY(oldcode,finchar); 1047 hval = BSD_HASH(oldcode,finchar,db->hshift); 1048 dictp = &db->dict[hval]; 1049 1050 /* look for a free hash table entry */ 1051 if (dictp->codem1 < max_ent) { 1052 disp = (hval == 0) ? 1 : hval; 1053 do { 1054 hval += disp; 1055 if (hval >= db->hsize) 1056 hval -= db->hsize; 1057 dictp = &db->dict[hval]; 1058 } while (dictp->codem1 < max_ent); 1059 } 1060 1061 /* 1062 * Invalidate previous hash table entry 1063 * assigned this code, and then take it over 1064 */ 1065 dictp2 = &db->dict[max_ent+1]; 1066 if (db->dict[dictp2->cptr].codem1 == max_ent) { 1067 db->dict[dictp2->cptr].codem1 = BADCODEM1; 1068 } 1069 dictp2->cptr = hval; 1070 dictp->codem1 = max_ent; 1071 dictp->f.fcode = fcode; 1072 1073 db->max_ent = ++max_ent; 1074 db->lens[max_ent] = db->lens[oldcode]+1; 1075 1076 /* Expand code size if needed. */ 1077 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) { 1078 db->n_bits = ++n_bits; 1079 tgtbitno = 32-n_bits; 1080 } 1081 } 1082 oldcode = incode; 1083 } 1084 dmp->m_len = wptr - mtod(dmp, u_char *); 1085 1086 /* 1087 * Keep the checkpoint right so that incompressible packets 1088 * clear the dictionary at the right times. 1089 */ 1090 db->bytes_out += ilen; 1091 db->in_count += explen; 1092 if (bsd_check(db) && db->debug) { 1093 printf("bsd_decomp%d: peer should have cleared dictionary\n", 1094 db->unit); 1095 } 1096 1097 ++db->comp_count; 1098 db->comp_bytes += ilen + BSD_OVHD; 1099 ++db->uncomp_count; 1100 db->uncomp_bytes += explen; 1101 1102 *dmpp = mret; 1103 return DECOMP_OK; 1104 1105 #ifdef DEBUG 1106 bad: 1107 if (codelen <= 0) { 1108 printf("bsd_decomp%d: fell off end of chain ", db->unit); 1109 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n", 1110 incode, finchar, db->dict[finchar].cptr, max_ent); 1111 } else if (dictp->codem1 != finchar-1) { 1112 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", 1113 db->unit, incode, finchar); 1114 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, 1115 db->dict[finchar].cptr, dictp->codem1); 1116 } 1117 m_freem(mret); 1118 return DECOMP_FATALERROR; 1119 #endif /* DEBUG */ 1120 } 1121 #endif /* DO_BSD_COMPRESS */ 1122