Annotation of sys/net/bsd-comp.c, Revision 1.1
1.1 ! nbrk 1: /* $OpenBSD: bsd-comp.c,v 1.6 2003/06/02 23:28:11 millert Exp $ */
! 2: /* $NetBSD: bsd-comp.c,v 1.6 1996/10/13 02:10:58 christos Exp $ */
! 3:
! 4: /* Because this code is derived from the 4.3BSD compress source:
! 5: *
! 6: *
! 7: * Copyright (c) 1985, 1986 The Regents of the University of California.
! 8: * All rights reserved.
! 9: *
! 10: * This code is derived from software contributed to Berkeley by
! 11: * James A. Woods, derived from original work by Spencer Thomas
! 12: * and Joseph Orost.
! 13: *
! 14: * Redistribution and use in source and binary forms, with or without
! 15: * modification, are permitted provided that the following conditions
! 16: * are met:
! 17: * 1. Redistributions of source code must retain the above copyright
! 18: * notice, this list of conditions and the following disclaimer.
! 19: * 2. Redistributions in binary form must reproduce the above copyright
! 20: * notice, this list of conditions and the following disclaimer in the
! 21: * documentation and/or other materials provided with the distribution.
! 22: * 3. Neither the name of the University nor the names of its contributors
! 23: * may be used to endorse or promote products derived from this software
! 24: * without specific prior written permission.
! 25: *
! 26: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 27: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 28: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 29: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 30: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 31: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 32: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 33: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 34: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 35: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 36: * SUCH DAMAGE.
! 37: */
! 38:
! 39: /*
! 40: * This version is for use with mbufs on BSD-derived systems.
! 41: */
! 42:
! 43: #include <sys/param.h>
! 44: #include <sys/types.h>
! 45: #include <sys/systm.h>
! 46: #include <sys/mbuf.h>
! 47: #include <sys/socket.h>
! 48: #include <net/if.h>
! 49: #include <net/if_types.h>
! 50: #include <net/ppp_defs.h>
! 51: #include <net/if_ppp.h>
! 52:
! 53: #define PACKETPTR struct mbuf *
! 54: #include <net/ppp-comp.h>
! 55:
! 56: #if DO_BSD_COMPRESS
! 57: /*
! 58: * PPP "BSD compress" compression
! 59: * The differences between this compression and the classic BSD LZW
! 60: * source are obvious from the requirement that the classic code worked
! 61: * with files while this handles arbitrarily long streams that
! 62: * are broken into packets. They are:
! 63: *
! 64: * When the code size expands, a block of junk is not emitted by
! 65: * the compressor and not expected by the decompressor.
! 66: *
! 67: * New codes are not necessarily assigned every time an old
! 68: * code is output by the compressor. This is because a packet
! 69: * end forces a code to be emitted, but does not imply that a
! 70: * new sequence has been seen.
! 71: *
! 72: * The compression ratio is checked at the first end of a packet
! 73: * after the appropriate gap. Besides simplifying and speeding
! 74: * things up, this makes it more likely that the transmitter
! 75: * and receiver will agree when the dictionary is cleared when
! 76: * compression is not going well.
! 77: */
! 78:
! 79: /*
! 80: * A dictionary for doing BSD compress.
! 81: */
! 82: struct bsd_db {
! 83: int totlen; /* length of this structure */
! 84: u_int hsize; /* size of the hash table */
! 85: u_char hshift; /* used in hash function */
! 86: u_char n_bits; /* current bits/code */
! 87: u_char maxbits;
! 88: u_char debug;
! 89: u_char unit;
! 90: u_int16_t seqno; /* sequence # of next packet */
! 91: u_int hdrlen; /* header length to preallocate */
! 92: u_int mru;
! 93: u_int maxmaxcode; /* largest valid code */
! 94: u_int max_ent; /* largest code in use */
! 95: u_int in_count; /* uncompressed bytes, aged */
! 96: u_int bytes_out; /* compressed bytes, aged */
! 97: u_int ratio; /* recent compression ratio */
! 98: u_int checkpoint; /* when to next check the ratio */
! 99: u_int clear_count; /* times dictionary cleared */
! 100: u_int incomp_count; /* incompressible packets */
! 101: u_int incomp_bytes; /* incompressible bytes */
! 102: u_int uncomp_count; /* uncompressed packets */
! 103: u_int uncomp_bytes; /* uncompressed bytes */
! 104: u_int comp_count; /* compressed packets */
! 105: u_int comp_bytes; /* compressed bytes */
! 106: u_int16_t *lens; /* array of lengths of codes */
! 107: struct bsd_dict {
! 108: union { /* hash value */
! 109: u_int32_t fcode;
! 110: struct {
! 111: #if BYTE_ORDER == LITTLE_ENDIAN
! 112: u_int16_t prefix; /* preceding code */
! 113: u_char suffix; /* last character of new code */
! 114: u_char pad;
! 115: #else
! 116: u_char pad;
! 117: u_char suffix; /* last character of new code */
! 118: u_int16_t prefix; /* preceding code */
! 119: #endif
! 120: } hs;
! 121: } f;
! 122: u_int16_t codem1; /* output of hash table -1 */
! 123: u_int16_t cptr; /* map code to hash table entry */
! 124: } dict[1];
! 125: };
! 126:
! 127: #define BSD_OVHD 2 /* BSD compress overhead/packet */
! 128: #define BSD_INIT_BITS BSD_MIN_BITS
! 129:
! 130: static void *bsd_comp_alloc(u_char *options, int opt_len);
! 131: static void *bsd_decomp_alloc(u_char *options, int opt_len);
! 132: static void bsd_free(void *state);
! 133: static int bsd_comp_init(void *state, u_char *options, int opt_len,
! 134: int unit, int hdrlen, int debug);
! 135: static int bsd_decomp_init(void *state, u_char *options, int opt_len,
! 136: int unit, int hdrlen, int mru, int debug);
! 137: static int bsd_compress(void *state, struct mbuf **mret,
! 138: struct mbuf *mp, int slen, int maxolen);
! 139: static void bsd_incomp(void *state, struct mbuf *dmsg);
! 140: static int bsd_decompress(void *state, struct mbuf *cmp,
! 141: struct mbuf **dmpp);
! 142: static void bsd_reset(void *state);
! 143: static void bsd_comp_stats(void *state, struct compstat *stats);
! 144:
! 145: /*
! 146: * Procedures exported to if_ppp.c.
! 147: */
! 148: struct compressor ppp_bsd_compress = {
! 149: CI_BSD_COMPRESS, /* compress_proto */
! 150: bsd_comp_alloc, /* comp_alloc */
! 151: bsd_free, /* comp_free */
! 152: bsd_comp_init, /* comp_init */
! 153: bsd_reset, /* comp_reset */
! 154: bsd_compress, /* compress */
! 155: bsd_comp_stats, /* comp_stat */
! 156: bsd_decomp_alloc, /* decomp_alloc */
! 157: bsd_free, /* decomp_free */
! 158: bsd_decomp_init, /* decomp_init */
! 159: bsd_reset, /* decomp_reset */
! 160: bsd_decompress, /* decompress */
! 161: bsd_incomp, /* incomp */
! 162: bsd_comp_stats, /* decomp_stat */
! 163: };
! 164:
! 165: /*
! 166: * the next two codes should not be changed lightly, as they must not
! 167: * lie within the contiguous general code space.
! 168: */
! 169: #define CLEAR 256 /* table clear output code */
! 170: #define FIRST 257 /* first free entry */
! 171: #define LAST 255
! 172:
! 173: #define MAXCODE(b) ((1 << (b)) - 1)
! 174: #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
! 175:
! 176: #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
! 177: ^ (u_int32_t)(prefix))
! 178: #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
! 179: + (u_int32_t)(prefix))
! 180:
! 181: #define CHECK_GAP 10000 /* Ratio check interval */
! 182:
! 183: #define RATIO_SCALE_LOG 8
! 184: #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
! 185: #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
! 186:
! 187: static void bsd_clear(struct bsd_db *);
! 188: static int bsd_check(struct bsd_db *);
! 189: static void *bsd_alloc(u_char *, int, int);
! 190: static int bsd_init(struct bsd_db *, u_char *, int, int, int, int,
! 191: int, int);
! 192:
! 193: /*
! 194: * clear the dictionary
! 195: */
! 196: static void
! 197: bsd_clear(db)
! 198: struct bsd_db *db;
! 199: {
! 200: db->clear_count++;
! 201: db->max_ent = FIRST-1;
! 202: db->n_bits = BSD_INIT_BITS;
! 203: db->ratio = 0;
! 204: db->bytes_out = 0;
! 205: db->in_count = 0;
! 206: db->incomp_count = 0;
! 207: db->checkpoint = CHECK_GAP;
! 208: }
! 209:
! 210: /*
! 211: * If the dictionary is full, then see if it is time to reset it.
! 212: *
! 213: * Compute the compression ratio using fixed-point arithmetic
! 214: * with 8 fractional bits.
! 215: *
! 216: * Since we have an infinite stream instead of a single file,
! 217: * watch only the local compression ratio.
! 218: *
! 219: * Since both peers must reset the dictionary at the same time even in
! 220: * the absence of CLEAR codes (while packets are incompressible), they
! 221: * must compute the same ratio.
! 222: */
! 223: static int /* 1=output CLEAR */
! 224: bsd_check(db)
! 225: struct bsd_db *db;
! 226: {
! 227: u_int new_ratio;
! 228:
! 229: if (db->in_count >= db->checkpoint) {
! 230: /* age the ratio by limiting the size of the counts */
! 231: if (db->in_count >= RATIO_MAX
! 232: || db->bytes_out >= RATIO_MAX) {
! 233: db->in_count -= db->in_count/4;
! 234: db->bytes_out -= db->bytes_out/4;
! 235: }
! 236:
! 237: db->checkpoint = db->in_count + CHECK_GAP;
! 238:
! 239: if (db->max_ent >= db->maxmaxcode) {
! 240: /* Reset the dictionary only if the ratio is worse,
! 241: * or if it looks as if it has been poisoned
! 242: * by incompressible data.
! 243: *
! 244: * This does not overflow, because
! 245: * db->in_count <= RATIO_MAX.
! 246: */
! 247: new_ratio = db->in_count << RATIO_SCALE_LOG;
! 248: if (db->bytes_out != 0)
! 249: new_ratio /= db->bytes_out;
! 250:
! 251: if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
! 252: bsd_clear(db);
! 253: return 1;
! 254: }
! 255: db->ratio = new_ratio;
! 256: }
! 257: }
! 258: return 0;
! 259: }
! 260:
! 261: /*
! 262: * Return statistics.
! 263: */
! 264: static void
! 265: bsd_comp_stats(state, stats)
! 266: void *state;
! 267: struct compstat *stats;
! 268: {
! 269: struct bsd_db *db = (struct bsd_db *) state;
! 270: u_int out;
! 271:
! 272: stats->unc_bytes = db->uncomp_bytes;
! 273: stats->unc_packets = db->uncomp_count;
! 274: stats->comp_bytes = db->comp_bytes;
! 275: stats->comp_packets = db->comp_count;
! 276: stats->inc_bytes = db->incomp_bytes;
! 277: stats->inc_packets = db->incomp_count;
! 278: stats->ratio = db->in_count;
! 279: out = db->bytes_out;
! 280: if (stats->ratio <= 0x7fffff)
! 281: stats->ratio <<= 8;
! 282: else
! 283: out >>= 8;
! 284: if (out != 0)
! 285: stats->ratio /= out;
! 286: }
! 287:
! 288: /*
! 289: * Reset state, as on a CCP ResetReq.
! 290: */
! 291: static void
! 292: bsd_reset(state)
! 293: void *state;
! 294: {
! 295: struct bsd_db *db = (struct bsd_db *) state;
! 296:
! 297: db->seqno = 0;
! 298: bsd_clear(db);
! 299: db->clear_count = 0;
! 300: }
! 301:
! 302: /*
! 303: * Allocate space for a (de) compressor.
! 304: */
! 305: static void *
! 306: bsd_alloc(options, opt_len, decomp)
! 307: u_char *options;
! 308: int opt_len, decomp;
! 309: {
! 310: int bits;
! 311: u_int newlen, hsize, hshift, maxmaxcode;
! 312: struct bsd_db *db;
! 313:
! 314: if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
! 315: || options[1] != CILEN_BSD_COMPRESS
! 316: || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
! 317: return NULL;
! 318: bits = BSD_NBITS(options[2]);
! 319: switch (bits) {
! 320: case 9: /* needs 82152 for both directions */
! 321: case 10: /* needs 84144 */
! 322: case 11: /* needs 88240 */
! 323: case 12: /* needs 96432 */
! 324: hsize = 5003;
! 325: hshift = 4;
! 326: break;
! 327: case 13: /* needs 176784 */
! 328: hsize = 9001;
! 329: hshift = 5;
! 330: break;
! 331: case 14: /* needs 353744 */
! 332: hsize = 18013;
! 333: hshift = 6;
! 334: break;
! 335: case 15: /* needs 691440 */
! 336: hsize = 35023;
! 337: hshift = 7;
! 338: break;
! 339: case 16: /* needs 1366160--far too much, */
! 340: /* hsize = 69001; */ /* and 69001 is too big for cptr */
! 341: /* hshift = 8; */ /* in struct bsd_db */
! 342: /* break; */
! 343: default:
! 344: return NULL;
! 345: }
! 346:
! 347: maxmaxcode = MAXCODE(bits);
! 348: newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
! 349: MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
! 350: if (!db)
! 351: return NULL;
! 352: bzero(db, sizeof(*db) - sizeof(db->dict));
! 353:
! 354: if (!decomp) {
! 355: db->lens = NULL;
! 356: } else {
! 357: MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
! 358: M_DEVBUF, M_NOWAIT);
! 359: if (!db->lens) {
! 360: FREE(db, M_DEVBUF);
! 361: return NULL;
! 362: }
! 363: }
! 364:
! 365: db->totlen = newlen;
! 366: db->hsize = hsize;
! 367: db->hshift = hshift;
! 368: db->maxmaxcode = maxmaxcode;
! 369: db->maxbits = bits;
! 370:
! 371: return (void *) db;
! 372: }
! 373:
! 374: static void
! 375: bsd_free(state)
! 376: void *state;
! 377: {
! 378: struct bsd_db *db = (struct bsd_db *) state;
! 379:
! 380: if (db->lens)
! 381: FREE(db->lens, M_DEVBUF);
! 382: FREE(db, M_DEVBUF);
! 383: }
! 384:
! 385: static void *
! 386: bsd_comp_alloc(options, opt_len)
! 387: u_char *options;
! 388: int opt_len;
! 389: {
! 390: return bsd_alloc(options, opt_len, 0);
! 391: }
! 392:
! 393: static void *
! 394: bsd_decomp_alloc(options, opt_len)
! 395: u_char *options;
! 396: int opt_len;
! 397: {
! 398: return bsd_alloc(options, opt_len, 1);
! 399: }
! 400:
! 401: /*
! 402: * Initialize the database.
! 403: */
! 404: static int
! 405: bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
! 406: struct bsd_db *db;
! 407: u_char *options;
! 408: int opt_len, unit, hdrlen, mru, debug, decomp;
! 409: {
! 410: int i;
! 411:
! 412: if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
! 413: || options[1] != CILEN_BSD_COMPRESS
! 414: || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
! 415: || BSD_NBITS(options[2]) != db->maxbits
! 416: || (decomp && db->lens == NULL))
! 417: return 0;
! 418:
! 419: if (decomp) {
! 420: i = LAST+1;
! 421: while (i != 0)
! 422: db->lens[--i] = 1;
! 423: }
! 424: i = db->hsize;
! 425: while (i != 0) {
! 426: db->dict[--i].codem1 = BADCODEM1;
! 427: db->dict[i].cptr = 0;
! 428: }
! 429:
! 430: db->unit = unit;
! 431: db->hdrlen = hdrlen;
! 432: db->mru = mru;
! 433: #ifndef DEBUG
! 434: if (debug)
! 435: #endif
! 436: db->debug = 1;
! 437:
! 438: bsd_reset(db);
! 439:
! 440: return 1;
! 441: }
! 442:
! 443: static int
! 444: bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
! 445: void *state;
! 446: u_char *options;
! 447: int opt_len, unit, hdrlen, debug;
! 448: {
! 449: return bsd_init((struct bsd_db *) state, options, opt_len,
! 450: unit, hdrlen, 0, debug, 0);
! 451: }
! 452:
! 453: static int
! 454: bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
! 455: void *state;
! 456: u_char *options;
! 457: int opt_len, unit, hdrlen, mru, debug;
! 458: {
! 459: return bsd_init((struct bsd_db *) state, options, opt_len,
! 460: unit, hdrlen, mru, debug, 1);
! 461: }
! 462:
! 463:
! 464: /*
! 465: * compress a packet
! 466: * One change from the BSD compress command is that when the
! 467: * code size expands, we do not output a bunch of padding.
! 468: */
! 469: int /* new slen */
! 470: bsd_compress(state, mret, mp, slen, maxolen)
! 471: void *state;
! 472: struct mbuf **mret; /* return compressed mbuf chain here */
! 473: struct mbuf *mp; /* from here */
! 474: int slen; /* uncompressed length */
! 475: int maxolen; /* max compressed length */
! 476: {
! 477: struct bsd_db *db = (struct bsd_db *) state;
! 478: int hshift = db->hshift;
! 479: u_int max_ent = db->max_ent;
! 480: u_int n_bits = db->n_bits;
! 481: u_int bitno = 32;
! 482: u_int32_t accm = 0, fcode;
! 483: struct bsd_dict *dictp;
! 484: u_char c;
! 485: int hval, disp, ent, ilen;
! 486: u_char *rptr, *wptr;
! 487: u_char *cp_end;
! 488: int olen;
! 489: struct mbuf *m;
! 490:
! 491: #define PUTBYTE(v) { \
! 492: ++olen; \
! 493: if (wptr) { \
! 494: *wptr++ = (v); \
! 495: if (wptr >= cp_end) { \
! 496: m->m_len = wptr - mtod(m, u_char *); \
! 497: MGET(m->m_next, M_DONTWAIT, MT_DATA); \
! 498: m = m->m_next; \
! 499: if (m) { \
! 500: m->m_len = 0; \
! 501: if (maxolen - olen > MLEN) \
! 502: MCLGET(m, M_DONTWAIT); \
! 503: wptr = mtod(m, u_char *); \
! 504: cp_end = wptr + M_TRAILINGSPACE(m); \
! 505: } else \
! 506: wptr = NULL; \
! 507: } \
! 508: } \
! 509: }
! 510:
! 511: #define OUTPUT(ent) { \
! 512: bitno -= n_bits; \
! 513: accm |= ((ent) << bitno); \
! 514: do { \
! 515: PUTBYTE(accm >> 24); \
! 516: accm <<= 8; \
! 517: bitno += 8; \
! 518: } while (bitno <= 24); \
! 519: }
! 520:
! 521: /*
! 522: * If the protocol is not in the range we're interested in,
! 523: * just return without compressing the packet. If it is,
! 524: * the protocol becomes the first byte to compress.
! 525: */
! 526: rptr = mtod(mp, u_char *);
! 527: ent = PPP_PROTOCOL(rptr);
! 528: if (ent < 0x21 || ent > 0xf9) {
! 529: *mret = NULL;
! 530: return slen;
! 531: }
! 532:
! 533: /* Don't generate compressed packets which are larger than
! 534: the uncompressed packet. */
! 535: if (maxolen > slen)
! 536: maxolen = slen;
! 537:
! 538: /* Allocate one mbuf to start with. */
! 539: MGET(m, M_DONTWAIT, MT_DATA);
! 540: *mret = m;
! 541: if (m != NULL) {
! 542: m->m_len = 0;
! 543: if (maxolen + db->hdrlen > MLEN)
! 544: MCLGET(m, M_DONTWAIT);
! 545: m->m_data += db->hdrlen;
! 546: wptr = mtod(m, u_char *);
! 547: cp_end = wptr + M_TRAILINGSPACE(m);
! 548: } else
! 549: wptr = cp_end = NULL;
! 550:
! 551: /*
! 552: * Copy the PPP header over, changing the protocol,
! 553: * and install the 2-byte packet sequence number.
! 554: */
! 555: if (wptr) {
! 556: *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
! 557: *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
! 558: *wptr++ = 0; /* change the protocol */
! 559: *wptr++ = PPP_COMP;
! 560: *wptr++ = db->seqno >> 8;
! 561: *wptr++ = db->seqno;
! 562: }
! 563: ++db->seqno;
! 564:
! 565: olen = 0;
! 566: rptr += PPP_HDRLEN;
! 567: slen = mp->m_len - PPP_HDRLEN;
! 568: ilen = slen + 1;
! 569: for (;;) {
! 570: if (slen <= 0) {
! 571: mp = mp->m_next;
! 572: if (!mp)
! 573: break;
! 574: rptr = mtod(mp, u_char *);
! 575: slen = mp->m_len;
! 576: if (!slen)
! 577: continue; /* handle 0-length buffers */
! 578: ilen += slen;
! 579: }
! 580:
! 581: slen--;
! 582: c = *rptr++;
! 583: fcode = BSD_KEY(ent, c);
! 584: hval = BSD_HASH(ent, c, hshift);
! 585: dictp = &db->dict[hval];
! 586:
! 587: /* Validate and then check the entry. */
! 588: if (dictp->codem1 >= max_ent)
! 589: goto nomatch;
! 590: if (dictp->f.fcode == fcode) {
! 591: ent = dictp->codem1+1;
! 592: continue; /* found (prefix,suffix) */
! 593: }
! 594:
! 595: /* continue probing until a match or invalid entry */
! 596: disp = (hval == 0) ? 1 : hval;
! 597: do {
! 598: hval += disp;
! 599: if (hval >= db->hsize)
! 600: hval -= db->hsize;
! 601: dictp = &db->dict[hval];
! 602: if (dictp->codem1 >= max_ent)
! 603: goto nomatch;
! 604: } while (dictp->f.fcode != fcode);
! 605: ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
! 606: continue;
! 607:
! 608: nomatch:
! 609: OUTPUT(ent); /* output the prefix */
! 610:
! 611: /* code -> hashtable */
! 612: if (max_ent < db->maxmaxcode) {
! 613: struct bsd_dict *dictp2;
! 614: /* expand code size if needed */
! 615: if (max_ent >= MAXCODE(n_bits))
! 616: db->n_bits = ++n_bits;
! 617:
! 618: /* Invalidate old hash table entry using
! 619: * this code, and then take it over.
! 620: */
! 621: dictp2 = &db->dict[max_ent+1];
! 622: if (db->dict[dictp2->cptr].codem1 == max_ent)
! 623: db->dict[dictp2->cptr].codem1 = BADCODEM1;
! 624: dictp2->cptr = hval;
! 625: dictp->codem1 = max_ent;
! 626: dictp->f.fcode = fcode;
! 627:
! 628: db->max_ent = ++max_ent;
! 629: }
! 630: ent = c;
! 631: }
! 632:
! 633: OUTPUT(ent); /* output the last code */
! 634: db->bytes_out += olen;
! 635: db->in_count += ilen;
! 636: if (bitno < 32)
! 637: ++db->bytes_out; /* count complete bytes */
! 638:
! 639: if (bsd_check(db))
! 640: OUTPUT(CLEAR); /* do not count the CLEAR */
! 641:
! 642: /*
! 643: * Pad dribble bits of last code with ones.
! 644: * Do not emit a completely useless byte of ones.
! 645: */
! 646: if (bitno != 32)
! 647: PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
! 648:
! 649: if (m != NULL) {
! 650: m->m_len = wptr - mtod(m, u_char *);
! 651: m->m_next = NULL;
! 652: }
! 653:
! 654: /*
! 655: * Increase code size if we would have without the packet
! 656: * boundary and as the decompressor will.
! 657: */
! 658: if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
! 659: db->n_bits++;
! 660:
! 661: db->uncomp_bytes += ilen;
! 662: ++db->uncomp_count;
! 663: if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
! 664: /* throw away the compressed stuff if it is longer than uncompressed */
! 665: if (*mret != NULL) {
! 666: m_freem(*mret);
! 667: *mret = NULL;
! 668: }
! 669: ++db->incomp_count;
! 670: db->incomp_bytes += ilen;
! 671: } else {
! 672: ++db->comp_count;
! 673: db->comp_bytes += olen + BSD_OVHD;
! 674: }
! 675:
! 676: return olen + PPP_HDRLEN + BSD_OVHD;
! 677: #undef OUTPUT
! 678: #undef PUTBYTE
! 679: }
! 680:
! 681:
! 682: /*
! 683: * Update the "BSD Compress" dictionary on the receiver for
! 684: * incompressible data by pretending to compress the incoming data.
! 685: */
! 686: static void
! 687: bsd_incomp(state, dmsg)
! 688: void *state;
! 689: struct mbuf *dmsg;
! 690: {
! 691: struct bsd_db *db = (struct bsd_db *) state;
! 692: u_int hshift = db->hshift;
! 693: u_int max_ent = db->max_ent;
! 694: u_int n_bits = db->n_bits;
! 695: struct bsd_dict *dictp;
! 696: u_int32_t fcode;
! 697: u_char c;
! 698: u_int32_t hval, disp;
! 699: int slen, ilen;
! 700: u_int bitno = 7;
! 701: u_char *rptr;
! 702: u_int ent;
! 703:
! 704: /*
! 705: * If the protocol is not in the range we're interested in,
! 706: * just return without looking at the packet. If it is,
! 707: * the protocol becomes the first byte to "compress".
! 708: */
! 709: rptr = mtod(dmsg, u_char *);
! 710: ent = PPP_PROTOCOL(rptr);
! 711: if (ent < 0x21 || ent > 0xf9)
! 712: return;
! 713:
! 714: db->incomp_count++;
! 715: db->seqno++;
! 716: ilen = 1; /* count the protocol as 1 byte */
! 717: rptr += PPP_HDRLEN;
! 718: slen = dmsg->m_len - PPP_HDRLEN;
! 719: for (;;) {
! 720: if (slen <= 0) {
! 721: dmsg = dmsg->m_next;
! 722: if (!dmsg)
! 723: break;
! 724: rptr = mtod(dmsg, u_char *);
! 725: slen = dmsg->m_len;
! 726: continue;
! 727: }
! 728: ilen += slen;
! 729:
! 730: do {
! 731: c = *rptr++;
! 732: fcode = BSD_KEY(ent, c);
! 733: hval = BSD_HASH(ent, c, hshift);
! 734: dictp = &db->dict[hval];
! 735:
! 736: /* validate and then check the entry */
! 737: if (dictp->codem1 >= max_ent)
! 738: goto nomatch;
! 739: if (dictp->f.fcode == fcode) {
! 740: ent = dictp->codem1+1;
! 741: continue; /* found (prefix,suffix) */
! 742: }
! 743:
! 744: /* continue probing until a match or invalid entry */
! 745: disp = (hval == 0) ? 1 : hval;
! 746: do {
! 747: hval += disp;
! 748: if (hval >= db->hsize)
! 749: hval -= db->hsize;
! 750: dictp = &db->dict[hval];
! 751: if (dictp->codem1 >= max_ent)
! 752: goto nomatch;
! 753: } while (dictp->f.fcode != fcode);
! 754: ent = dictp->codem1+1;
! 755: continue; /* finally found (prefix,suffix) */
! 756:
! 757: nomatch: /* output (count) the prefix */
! 758: bitno += n_bits;
! 759:
! 760: /* code -> hashtable */
! 761: if (max_ent < db->maxmaxcode) {
! 762: struct bsd_dict *dictp2;
! 763: /* expand code size if needed */
! 764: if (max_ent >= MAXCODE(n_bits))
! 765: db->n_bits = ++n_bits;
! 766:
! 767: /* Invalidate previous hash table entry
! 768: * assigned this code, and then take it over.
! 769: */
! 770: dictp2 = &db->dict[max_ent+1];
! 771: if (db->dict[dictp2->cptr].codem1 == max_ent)
! 772: db->dict[dictp2->cptr].codem1 = BADCODEM1;
! 773: dictp2->cptr = hval;
! 774: dictp->codem1 = max_ent;
! 775: dictp->f.fcode = fcode;
! 776:
! 777: db->max_ent = ++max_ent;
! 778: db->lens[max_ent] = db->lens[ent]+1;
! 779: }
! 780: ent = c;
! 781: } while (--slen != 0);
! 782: }
! 783: bitno += n_bits; /* output (count) the last code */
! 784: db->bytes_out += bitno/8;
! 785: db->in_count += ilen;
! 786: (void)bsd_check(db);
! 787:
! 788: ++db->incomp_count;
! 789: db->incomp_bytes += ilen;
! 790: ++db->uncomp_count;
! 791: db->uncomp_bytes += ilen;
! 792:
! 793: /* Increase code size if we would have without the packet
! 794: * boundary and as the decompressor will.
! 795: */
! 796: if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
! 797: db->n_bits++;
! 798: }
! 799:
! 800:
! 801: /*
! 802: * Decompress "BSD Compress".
! 803: *
! 804: * Because of patent problems, we return DECOMP_ERROR for errors
! 805: * found by inspecting the input data and for system problems, but
! 806: * DECOMP_FATALERROR for any errors which could possibly be said to
! 807: * be being detected "after" decompression. For DECOMP_ERROR,
! 808: * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
! 809: * infringing a patent of Motorola's if we do, so we take CCP down
! 810: * instead.
! 811: *
! 812: * Given that the frame has the correct sequence number and a good FCS,
! 813: * errors such as invalid codes in the input most likely indicate a
! 814: * bug, so we return DECOMP_FATALERROR for them in order to turn off
! 815: * compression, even though they are detected by inspecting the input.
! 816: */
! 817: int
! 818: bsd_decompress(state, cmp, dmpp)
! 819: void *state;
! 820: struct mbuf *cmp, **dmpp;
! 821: {
! 822: struct bsd_db *db = (struct bsd_db *) state;
! 823: u_int max_ent = db->max_ent;
! 824: u_int32_t accm = 0;
! 825: u_int bitno = 32; /* 1st valid bit in accm */
! 826: u_int n_bits = db->n_bits;
! 827: u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
! 828: struct bsd_dict *dictp;
! 829: int explen, i, seq, len;
! 830: u_int incode, oldcode, finchar;
! 831: u_char *p, *rptr, *wptr;
! 832: struct mbuf *m, *dmp, *mret;
! 833: int adrs, ctrl, ilen;
! 834: int space, codelen, extra;
! 835:
! 836: /*
! 837: * Save the address/control from the PPP header
! 838: * and then get the sequence number.
! 839: */
! 840: *dmpp = NULL;
! 841: rptr = mtod(cmp, u_char *);
! 842: adrs = PPP_ADDRESS(rptr);
! 843: ctrl = PPP_CONTROL(rptr);
! 844: rptr += PPP_HDRLEN;
! 845: len = cmp->m_len - PPP_HDRLEN;
! 846: seq = 0;
! 847: for (i = 0; i < 2; ++i) {
! 848: while (len <= 0) {
! 849: cmp = cmp->m_next;
! 850: if (cmp == NULL)
! 851: return DECOMP_ERROR;
! 852: rptr = mtod(cmp, u_char *);
! 853: len = cmp->m_len;
! 854: }
! 855: seq = (seq << 8) + *rptr++;
! 856: --len;
! 857: }
! 858:
! 859: /*
! 860: * Check the sequence number and give up if it differs from
! 861: * the value we're expecting.
! 862: */
! 863: if (seq != db->seqno) {
! 864: if (db->debug)
! 865: printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
! 866: db->unit, seq, db->seqno - 1);
! 867: return DECOMP_ERROR;
! 868: }
! 869: ++db->seqno;
! 870:
! 871: /*
! 872: * Allocate one mbuf to start with.
! 873: */
! 874: MGETHDR(dmp, M_DONTWAIT, MT_DATA);
! 875: if (dmp == NULL)
! 876: return DECOMP_ERROR;
! 877: mret = dmp;
! 878: dmp->m_len = 0;
! 879: dmp->m_next = NULL;
! 880: MCLGET(dmp, M_DONTWAIT);
! 881: dmp->m_data += db->hdrlen;
! 882: wptr = mtod(dmp, u_char *);
! 883: space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
! 884:
! 885: /*
! 886: * Fill in the ppp header, but not the last byte of the protocol
! 887: * (that comes from the decompressed data).
! 888: */
! 889: wptr[0] = adrs;
! 890: wptr[1] = ctrl;
! 891: wptr[2] = 0;
! 892: wptr += PPP_HDRLEN - 1;
! 893:
! 894: ilen = len;
! 895: oldcode = CLEAR;
! 896: explen = 0;
! 897: for (;;) {
! 898: if (len == 0) {
! 899: cmp = cmp->m_next;
! 900: if (!cmp) /* quit at end of message */
! 901: break;
! 902: rptr = mtod(cmp, u_char *);
! 903: len = cmp->m_len;
! 904: ilen += len;
! 905: continue; /* handle 0-length buffers */
! 906: }
! 907:
! 908: /*
! 909: * Accumulate bytes until we have a complete code.
! 910: * Then get the next code, relying on the 32-bit,
! 911: * unsigned accm to mask the result.
! 912: */
! 913: bitno -= 8;
! 914: accm |= *rptr++ << bitno;
! 915: --len;
! 916: if (tgtbitno < bitno)
! 917: continue;
! 918: incode = accm >> tgtbitno;
! 919: accm <<= n_bits;
! 920: bitno += n_bits;
! 921:
! 922: if (incode == CLEAR) {
! 923: /*
! 924: * The dictionary must only be cleared at
! 925: * the end of a packet. But there could be an
! 926: * empty mbuf at the end.
! 927: */
! 928: if (len > 0 || cmp->m_next != NULL) {
! 929: while ((cmp = cmp->m_next) != NULL)
! 930: len += cmp->m_len;
! 931: if (len > 0) {
! 932: m_freem(mret);
! 933: if (db->debug)
! 934: printf("bsd_decomp%d: bad CLEAR\n", db->unit);
! 935: return DECOMP_FATALERROR; /* probably a bug */
! 936: }
! 937: }
! 938: bsd_clear(db);
! 939: explen = ilen = 0;
! 940: break;
! 941: }
! 942:
! 943: if (incode > max_ent + 2 || incode > db->maxmaxcode
! 944: || (incode > max_ent && oldcode == CLEAR)) {
! 945: m_freem(mret);
! 946: if (db->debug) {
! 947: printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
! 948: db->unit, incode, oldcode);
! 949: printf("max_ent=0x%x explen=%d seqno=%d\n",
! 950: max_ent, explen, db->seqno);
! 951: }
! 952: return DECOMP_FATALERROR; /* probably a bug */
! 953: }
! 954:
! 955: /* Special case for KwKwK string. */
! 956: if (incode > max_ent) {
! 957: finchar = oldcode;
! 958: extra = 1;
! 959: } else {
! 960: finchar = incode;
! 961: extra = 0;
! 962: }
! 963:
! 964: codelen = db->lens[finchar];
! 965: explen += codelen + extra;
! 966: if (explen > db->mru + 1) {
! 967: m_freem(mret);
! 968: if (db->debug) {
! 969: printf("bsd_decomp%d: ran out of mru\n", db->unit);
! 970: #ifdef DEBUG
! 971: while ((cmp = cmp->m_next) != NULL)
! 972: len += cmp->m_len;
! 973: printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
! 974: len, finchar, codelen, explen);
! 975: #endif
! 976: }
! 977: return DECOMP_FATALERROR;
! 978: }
! 979:
! 980: /*
! 981: * For simplicity, the decoded characters go in a single mbuf,
! 982: * so we allocate a single extra cluster mbuf if necessary.
! 983: */
! 984: if ((space -= codelen + extra) < 0) {
! 985: dmp->m_len = wptr - mtod(dmp, u_char *);
! 986: MGET(m, M_DONTWAIT, MT_DATA);
! 987: if (m == NULL) {
! 988: m_freem(mret);
! 989: return DECOMP_ERROR;
! 990: }
! 991: m->m_len = 0;
! 992: m->m_next = NULL;
! 993: dmp->m_next = m;
! 994: MCLGET(m, M_DONTWAIT);
! 995: space = M_TRAILINGSPACE(m) - (codelen + extra);
! 996: if (space < 0) {
! 997: /* now that's what I call *compression*. */
! 998: m_freem(mret);
! 999: return DECOMP_ERROR;
! 1000: }
! 1001: dmp = m;
! 1002: wptr = mtod(dmp, u_char *);
! 1003: }
! 1004:
! 1005: /*
! 1006: * Decode this code and install it in the decompressed buffer.
! 1007: */
! 1008: p = (wptr += codelen);
! 1009: while (finchar > LAST) {
! 1010: dictp = &db->dict[db->dict[finchar].cptr];
! 1011: #ifdef DEBUG
! 1012: if (--codelen <= 0 || dictp->codem1 != finchar-1)
! 1013: goto bad;
! 1014: #endif
! 1015: *--p = dictp->f.hs.suffix;
! 1016: finchar = dictp->f.hs.prefix;
! 1017: }
! 1018: *--p = finchar;
! 1019:
! 1020: #ifdef DEBUG
! 1021: if (--codelen != 0)
! 1022: printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
! 1023: db->unit, codelen, incode, max_ent);
! 1024: #endif
! 1025:
! 1026: if (extra) /* the KwKwK case again */
! 1027: *wptr++ = finchar;
! 1028:
! 1029: /*
! 1030: * If not first code in a packet, and
! 1031: * if not out of code space, then allocate a new code.
! 1032: *
! 1033: * Keep the hash table correct so it can be used
! 1034: * with uncompressed packets.
! 1035: */
! 1036: if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
! 1037: struct bsd_dict *dictp2;
! 1038: u_int32_t fcode;
! 1039: u_int32_t hval, disp;
! 1040:
! 1041: fcode = BSD_KEY(oldcode,finchar);
! 1042: hval = BSD_HASH(oldcode,finchar,db->hshift);
! 1043: dictp = &db->dict[hval];
! 1044:
! 1045: /* look for a free hash table entry */
! 1046: if (dictp->codem1 < max_ent) {
! 1047: disp = (hval == 0) ? 1 : hval;
! 1048: do {
! 1049: hval += disp;
! 1050: if (hval >= db->hsize)
! 1051: hval -= db->hsize;
! 1052: dictp = &db->dict[hval];
! 1053: } while (dictp->codem1 < max_ent);
! 1054: }
! 1055:
! 1056: /*
! 1057: * Invalidate previous hash table entry
! 1058: * assigned this code, and then take it over
! 1059: */
! 1060: dictp2 = &db->dict[max_ent+1];
! 1061: if (db->dict[dictp2->cptr].codem1 == max_ent) {
! 1062: db->dict[dictp2->cptr].codem1 = BADCODEM1;
! 1063: }
! 1064: dictp2->cptr = hval;
! 1065: dictp->codem1 = max_ent;
! 1066: dictp->f.fcode = fcode;
! 1067:
! 1068: db->max_ent = ++max_ent;
! 1069: db->lens[max_ent] = db->lens[oldcode]+1;
! 1070:
! 1071: /* Expand code size if needed. */
! 1072: if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
! 1073: db->n_bits = ++n_bits;
! 1074: tgtbitno = 32-n_bits;
! 1075: }
! 1076: }
! 1077: oldcode = incode;
! 1078: }
! 1079: dmp->m_len = wptr - mtod(dmp, u_char *);
! 1080:
! 1081: /*
! 1082: * Keep the checkpoint right so that incompressible packets
! 1083: * clear the dictionary at the right times.
! 1084: */
! 1085: db->bytes_out += ilen;
! 1086: db->in_count += explen;
! 1087: if (bsd_check(db) && db->debug) {
! 1088: printf("bsd_decomp%d: peer should have cleared dictionary\n",
! 1089: db->unit);
! 1090: }
! 1091:
! 1092: ++db->comp_count;
! 1093: db->comp_bytes += ilen + BSD_OVHD;
! 1094: ++db->uncomp_count;
! 1095: db->uncomp_bytes += explen;
! 1096:
! 1097: *dmpp = mret;
! 1098: return DECOMP_OK;
! 1099:
! 1100: #ifdef DEBUG
! 1101: bad:
! 1102: if (codelen <= 0) {
! 1103: printf("bsd_decomp%d: fell off end of chain ", db->unit);
! 1104: printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
! 1105: incode, finchar, db->dict[finchar].cptr, max_ent);
! 1106: } else if (dictp->codem1 != finchar-1) {
! 1107: printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
! 1108: db->unit, incode, finchar);
! 1109: printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
! 1110: db->dict[finchar].cptr, dictp->codem1);
! 1111: }
! 1112: m_freem(mret);
! 1113: return DECOMP_FATALERROR;
! 1114: #endif /* DEBUG */
! 1115: }
! 1116: #endif /* DO_BSD_COMPRESS */
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