sys/net/bsd_comp.c

   1 /* Because this code is derived from the 4.3BSD compress source:
   2  *
   3  *
   4  * Copyright (c) 1985, 1986 The Regents of the University of California.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * James A. Woods, derived from original work by Spencer Thomas
   9  * and Joseph Orost.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. All advertising materials mentioning features or use of this software
  20  *    must display the following acknowledgement:
  21  *      This product includes software developed by the University of
  22  *      California, Berkeley and its contributors.
  23  * 4. Neither the name of the University nor the names of its contributors
  24  *    may be used to endorse or promote products derived from this software
  25  *    without specific prior written permission.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  37  * SUCH DAMAGE.
  38  */
  39
  40 /*
  41  * This version is for use with mbufs on BSD-derived systems.
  42  *
  43  * $FreeBSD: src/sys/net/bsd_comp.c,v 1.11.2.1 2002/04/14 21:41:48 luigi Exp $
  44  * $DragonFly: src/sys/net/bsd_comp.c,v 1.11 2006/12/22 23:44:54 swildner Exp $
  45  */
  46
  47 #include <sys/param.h>
  48 #include <sys/systm.h>
  49 #include <sys/malloc.h>
  50 #include <sys/mbuf.h>
  51 #include <net/ppp_layer/ppp_defs.h>
  52
  53 #define PACKETPTR       struct mbuf *
  54 #include <net/ppp_layer/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_clear (struct bsd_db *db);
 131 static int      bsd_check (struct bsd_db *db);
 132 static void     *bsd_alloc (u_char *options, int opt_len, int decomp);
 133 static int      bsd_init (struct bsd_db *db, u_char *options, int opt_len,
 134                               int unit, int hdrlen, int mru, int debug,
 135                               int decomp);
 136 static void     *bsd_comp_alloc (u_char *options, int opt_len);
 137 static void     *bsd_decomp_alloc (u_char *options, int opt_len);
 138 static void     bsd_free (void *state);
 139 static int      bsd_comp_init (void *state, u_char *options, int opt_len,
 140                                    int unit, int hdrlen, int debug);
 141 static int      bsd_decomp_init (void *state, u_char *options, int opt_len,
 142                                      int unit, int hdrlen, int mru, int debug);
 143 static int      bsd_compress (void *state, struct mbuf **mret,
 144                                   struct mbuf *mp, int slen, int maxolen);
 145 static void     bsd_incomp (void *state, struct mbuf *dmsg);
 146 static int      bsd_decompress (void *state, struct mbuf *cmp,
 147                                     struct mbuf **dmpp);
 148 static void     bsd_reset (void *state);
 149 static void     bsd_comp_stats (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 /*
 194  * clear the dictionary
 195  */
 196 static void
 197 bsd_clear(struct bsd_db *db)
 198 {
 199     db->clear_count++;
 200     db->max_ent = FIRST-1;
 201     db->n_bits = BSD_INIT_BITS;
 202     db->ratio = 0;
 203     db->bytes_out = 0;
 204     db->in_count = 0;
 205     db->checkpoint = CHECK_GAP;
 206 }
 207
 208 /*
 209  * If the dictionary is full, then see if it is time to reset it.
 210  *
 211  * Compute the compression ratio using fixed-point arithmetic
 212  * with 8 fractional bits.
 213  *
 214  * Since we have an infinite stream instead of a single file,
 215  * watch only the local compression ratio.
 216  *
 217  * Since both peers must reset the dictionary at the same time even in
 218  * the absence of CLEAR codes (while packets are incompressible), they
 219  * must compute the same ratio.
 220  *
 221  * Return 1=output CLEAR
 222  */
 223 static int
 224 bsd_check(struct bsd_db *db)
 225 {
 226     u_int new_ratio;
 227
 228     if (db->in_count >= db->checkpoint) {
 229         /* age the ratio by limiting the size of the counts */
 230         if (db->in_count >= RATIO_MAX
 231             || db->bytes_out >= RATIO_MAX) {
 232             db->in_count -= db->in_count/4;
 233             db->bytes_out -= db->bytes_out/4;
 234         }
 235
 236         db->checkpoint = db->in_count + CHECK_GAP;
 237
 238         if (db->max_ent >= db->maxmaxcode) {
 239             /* Reset the dictionary only if the ratio is worse,
 240              * or if it looks as if it has been poisoned
 241              * by incompressible data.
 242              *
 243              * This does not overflow, because
 244              *  db->in_count <= RATIO_MAX.
 245              */
 246             new_ratio = db->in_count << RATIO_SCALE_LOG;
 247             if (db->bytes_out != 0)
 248                 new_ratio /= db->bytes_out;
 249
 250             if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
 251                 bsd_clear(db);
 252                 return 1;
 253             }
 254             db->ratio = new_ratio;
 255         }
 256     }
 257     return 0;
 258 }
 259
 260 /*
 261  * Return statistics.
 262  */
 263 static void
 264 bsd_comp_stats(void *state, struct compstat *stats)
 265 {
 266     struct bsd_db *db = (struct bsd_db *) state;
 267     u_int out;
 268
 269     stats->unc_bytes = db->uncomp_bytes;
 270     stats->unc_packets = db->uncomp_count;
 271     stats->comp_bytes = db->comp_bytes;
 272     stats->comp_packets = db->comp_count;
 273     stats->inc_bytes = db->incomp_bytes;
 274     stats->inc_packets = db->incomp_count;
 275     stats->ratio = db->in_count;
 276     out = db->bytes_out;
 277     if (stats->ratio <= 0x7fffff)
 278         stats->ratio <<= 8;
 279     else
 280         out >>= 8;
 281     if (out != 0)
 282         stats->ratio /= out;
 283 }
 284
 285 /*
 286  * Reset state, as on a CCP ResetReq.
 287  */
 288 static void
 289 bsd_reset(void *state)
 290 {
 291     struct bsd_db *db = (struct bsd_db *) state;
 292
 293     db->seqno = 0;
 294     bsd_clear(db);
 295     db->clear_count = 0;
 296 }
 297
 298 /*
 299  * Allocate space for a (de) compressor.
 300  */
 301 static void *
 302 bsd_alloc(u_char *options, int opt_len, int decomp)
 303 {
 304     int bits;
 305     u_int newlen, hsize, hshift, maxmaxcode;
 306     struct bsd_db *db;
 307
 308     if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
 309         || options[1] != CILEN_BSD_COMPRESS
 310         || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
 311         return NULL;
 312     bits = BSD_NBITS(options[2]);
 313     switch (bits) {
 314     case 9:                     /* needs 82152 for both directions */
 315     case 10:                    /* needs 84144 */
 316     case 11:                    /* needs 88240 */
 317     case 12:                    /* needs 96432 */
 318         hsize = 5003;
 319         hshift = 4;
 320         break;
 321     case 13:                    /* needs 176784 */
 322         hsize = 9001;
 323         hshift = 5;
 324         break;
 325     case 14:                    /* needs 353744 */
 326         hsize = 18013;
 327         hshift = 6;
 328         break;
 329     case 15:                    /* needs 691440 */
 330         hsize = 35023;
 331         hshift = 7;
 332         break;
 333     case 16:                    /* needs 1366160--far too much, */
 334         /* hsize = 69001; */    /* and 69001 is too big for cptr */
 335         /* hshift = 8; */       /* in struct bsd_db */
 336         /* break; */
 337     default:
 338         return NULL;
 339     }
 340
 341     maxmaxcode = MAXCODE(bits);
 342     newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
 343     MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_WAITOK);
 344     bzero(db, sizeof(*db) - sizeof(db->dict));
 345
 346     if (!decomp) {
 347         db->lens = NULL;
 348     } else {
 349         MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
 350                M_DEVBUF, M_WAITOK);
 351     }
 352
 353     db->totlen = newlen;
 354     db->hsize = hsize;
 355     db->hshift = hshift;
 356     db->maxmaxcode = maxmaxcode;
 357     db->maxbits = bits;
 358
 359     return (void *) db;
 360 }
 361
 362 static void
 363 bsd_free(void *state)
 364 {
 365     struct bsd_db *db = (struct bsd_db *) state;
 366
 367     if (db->lens)
 368         kfree(db->lens, M_DEVBUF);
 369     kfree(db, M_DEVBUF);
 370 }
 371
 372 static void *
 373 bsd_comp_alloc(u_char *options, int opt_len)
 374 {
 375     return bsd_alloc(options, opt_len, 0);
 376 }
 377
 378 static void *
 379 bsd_decomp_alloc(u_char *options, int opt_len)
 380 {
 381     return bsd_alloc(options, opt_len, 1);
 382 }
 383
 384 /*
 385  * Initialize the database.
 386  */
 387 static int
 388 bsd_init(struct bsd_db *db, u_char *options, int opt_len, int unit,
 389     int hdrlen, int mru, int debug, int decomp)
 390 {
 391     int i;
 392
 393     if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
 394         || options[1] != CILEN_BSD_COMPRESS
 395         || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
 396         || BSD_NBITS(options[2]) != db->maxbits
 397         || (decomp && db->lens == NULL))
 398         return 0;
 399
 400     if (decomp) {
 401         i = LAST+1;
 402         while (i != 0)
 403             db->lens[--i] = 1;
 404     }
 405     i = db->hsize;
 406     while (i != 0) {
 407         db->dict[--i].codem1 = BADCODEM1;
 408         db->dict[i].cptr = 0;
 409     }
 410
 411     db->unit = unit;
 412     db->hdrlen = hdrlen;
 413     db->mru = mru;
 414 #ifndef DEBUG
 415     if (debug)
 416 #endif
 417         db->debug = 1;
 418
 419     bsd_reset(db);
 420
 421     return 1;
 422 }
 423
 424 static int
 425 bsd_comp_init(void *state, u_char *options, int opt_len, int unit,
 426     int hdrlen, int debug)
 427 {
 428     return bsd_init((struct bsd_db *) state, options, opt_len,
 429                     unit, hdrlen, 0, debug, 0);
 430 }
 431
 432 static int
 433 bsd_decomp_init(void *state, u_char *options, int opt_len,
 434     int unit, int hdrlen, int mru, int debug)
 435 {
 436         return bsd_init((struct bsd_db *) state, options, opt_len,
 437             unit, hdrlen, mru, debug, 1);
 438 }
 439
 440
 441 /*
 442  * compress a packet
 443  *      One change from the BSD compress command is that when the
 444  *      code size expands, we do not output a bunch of padding.
 445  *   **mret     - return compressed mbuf chain here
 446  *   *mp        - from here
 447  *   slen       - uncompressed length
 448  *   maxolen    - max compressed length
 449  *
 450  * return new slen
 451  */
 452 int
 453 bsd_compress(void *state, struct mbuf **mret, struct mbuf *mp,
 454     int slen, int maxolen)
 455 {
 456     struct bsd_db *db = (struct bsd_db *) state;
 457     int hshift = db->hshift;
 458     u_int max_ent = db->max_ent;
 459     u_int n_bits = db->n_bits;
 460     u_int bitno = 32;
 461     u_int32_t accm = 0, fcode;
 462     struct bsd_dict *dictp;
 463     u_char c;
 464     int hval, disp, ent, ilen;
 465     u_char *rptr, *wptr;
 466     u_char *cp_end;
 467     int olen;
 468     struct mbuf *m;
 469
 470 #define PUTBYTE(v) {                                    \
 471     ++olen;                                             \
 472     if (wptr) {                                         \
 473         *wptr++ = (v);                                  \
 474         if (wptr >= cp_end) {                           \
 475             m->m_len = wptr - mtod(m, u_char *);        \
 476             MGET(m->m_next, MB_DONTWAIT, MT_DATA);      \
 477             m = m->m_next;                              \
 478             if (m) {                                    \
 479                 m->m_len = 0;                           \
 480                 if (maxolen - olen > MLEN)              \
 481                     MCLGET(m, MB_DONTWAIT);             \
 482                 wptr = mtod(m, u_char *);               \
 483                 cp_end = wptr + M_TRAILINGSPACE(m);     \
 484             } else                                      \
 485                 wptr = NULL;                            \
 486         }                                               \
 487     }                                                   \
 488 }
 489
 490 #define OUTPUT(ent) {                                   \
 491     bitno -= n_bits;                                    \
 492     accm |= ((ent) << bitno);                           \
 493     do {                                                \
 494         PUTBYTE(accm >> 24);                            \
 495         accm <<= 8;                                     \
 496         bitno += 8;                                     \
 497     } while (bitno <= 24);                              \
 498 }
 499
 500     /*
 501      * If the protocol is not in the range we're interested in,
 502      * just return without compressing the packet.  If it is,
 503      * the protocol becomes the first byte to compress.
 504      */
 505     rptr = mtod(mp, u_char *);
 506     ent = PPP_PROTOCOL(rptr);
 507     if (ent < 0x21 || ent > 0xf9) {
 508         *mret = NULL;
 509         return slen;
 510     }
 511
 512     /* Don't generate compressed packets which are larger than
 513        the uncompressed packet. */
 514     if (maxolen > slen)
 515         maxolen = slen;
 516
 517     /* Allocate one mbuf to start with. */
 518     MGET(m, MB_DONTWAIT, MT_DATA);
 519     *mret = m;
 520     if (m != NULL) {
 521         m->m_len = 0;
 522         if (maxolen + db->hdrlen > MLEN)
 523             MCLGET(m, MB_DONTWAIT);
 524         m->m_data += db->hdrlen;
 525         wptr = mtod(m, u_char *);
 526         cp_end = wptr + M_TRAILINGSPACE(m);
 527     } else
 528         wptr = cp_end = NULL;
 529
 530     /*
 531      * Copy the PPP header over, changing the protocol,
 532      * and install the 2-byte packet sequence number.
 533      */
 534     if (wptr) {
 535         *wptr++ = PPP_ADDRESS(rptr);    /* assumes the ppp header is */
 536         *wptr++ = PPP_CONTROL(rptr);    /* all in one mbuf */
 537         *wptr++ = 0;                    /* change the protocol */
 538         *wptr++ = PPP_COMP;
 539         *wptr++ = db->seqno >> 8;
 540         *wptr++ = db->seqno;
 541     }
 542     ++db->seqno;
 543
 544     olen = 0;
 545     rptr += PPP_HDRLEN;
 546     slen = mp->m_len - PPP_HDRLEN;
 547     ilen = slen + 1;
 548     for (;;) {
 549         if (slen <= 0) {
 550             mp = mp->m_next;
 551             if (!mp)
 552                 break;
 553             rptr = mtod(mp, u_char *);
 554             slen = mp->m_len;
 555             if (!slen)
 556                 continue;   /* handle 0-length buffers */
 557             ilen += slen;
 558         }
 559
 560         slen--;
 561         c = *rptr++;
 562         fcode = BSD_KEY(ent, c);
 563         hval = BSD_HASH(ent, c, hshift);
 564         dictp = &db->dict[hval];
 565
 566         /* Validate and then check the entry. */
 567         if (dictp->codem1 >= max_ent)
 568             goto nomatch;
 569         if (dictp->f.fcode == fcode) {
 570             ent = dictp->codem1+1;
 571             continue;   /* found (prefix,suffix) */
 572         }
 573
 574         /* continue probing until a match or invalid entry */
 575         disp = (hval == 0) ? 1 : hval;
 576         do {
 577             hval += disp;
 578             if (hval >= db->hsize)
 579                 hval -= db->hsize;
 580             dictp = &db->dict[hval];
 581             if (dictp->codem1 >= max_ent)
 582                 goto nomatch;
 583         } while (dictp->f.fcode != fcode);
 584         ent = dictp->codem1 + 1;        /* finally found (prefix,suffix) */
 585         continue;
 586
 587     nomatch:
 588         OUTPUT(ent);            /* output the prefix */
 589
 590         /* code -> hashtable */
 591         if (max_ent < db->maxmaxcode) {
 592             struct bsd_dict *dictp2;
 593             /* expand code size if needed */
 594             if (max_ent >= MAXCODE(n_bits))
 595                 db->n_bits = ++n_bits;
 596
 597             /* Invalidate old hash table entry using
 598              * this code, and then take it over.
 599              */
 600             dictp2 = &db->dict[max_ent+1];
 601             if (db->dict[dictp2->cptr].codem1 == max_ent)
 602                 db->dict[dictp2->cptr].codem1 = BADCODEM1;
 603             dictp2->cptr = hval;
 604             dictp->codem1 = max_ent;
 605             dictp->f.fcode = fcode;
 606
 607             db->max_ent = ++max_ent;
 608         }
 609         ent = c;
 610     }
 611
 612     OUTPUT(ent);                /* output the last code */
 613     db->bytes_out += olen;
 614     db->in_count += ilen;
 615     if (bitno < 32)
 616         ++db->bytes_out;        /* count complete bytes */
 617
 618     if (bsd_check(db))
 619         OUTPUT(CLEAR);          /* do not count the CLEAR */
 620
 621     /*
 622      * Pad dribble bits of last code with ones.
 623      * Do not emit a completely useless byte of ones.
 624      */
 625     if (bitno != 32)
 626         PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
 627
 628     if (m != NULL) {
 629         m->m_len = wptr - mtod(m, u_char *);
 630         m->m_next = NULL;
 631     }
 632
 633     /*
 634      * Increase code size if we would have without the packet
 635      * boundary and as the decompressor will.
 636      */
 637     if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
 638         db->n_bits++;
 639
 640     db->uncomp_bytes += ilen;
 641     ++db->uncomp_count;
 642     if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
 643         /* throw away the compressed stuff if it is longer than uncompressed */
 644         if (*mret != NULL) {
 645             m_freem(*mret);
 646             *mret = NULL;
 647         }
 648         ++db->incomp_count;
 649         db->incomp_bytes += ilen;
 650     } else {
 651         ++db->comp_count;
 652         db->comp_bytes += olen + BSD_OVHD;
 653     }
 654
 655     return olen + PPP_HDRLEN + BSD_OVHD;
 656 #undef OUTPUT
 657 #undef PUTBYTE
 658 }
 659
 660
 661 /*
 662  * Update the "BSD Compress" dictionary on the receiver for
 663  * incompressible data by pretending to compress the incoming data.
 664  */
 665 static void
 666 bsd_incomp(void *state, struct mbuf *dmsg)
 667 {
 668     struct bsd_db *db = (struct bsd_db *) state;
 669     u_int hshift = db->hshift;
 670     u_int max_ent = db->max_ent;
 671     u_int n_bits = db->n_bits;
 672     struct bsd_dict *dictp;
 673     u_int32_t fcode;
 674     u_char c;
 675     u_int32_t hval, disp;
 676     int slen, ilen;
 677     u_int bitno = 7;
 678     u_char *rptr;
 679     u_int ent;
 680
 681     /*
 682      * If the protocol is not in the range we're interested in,
 683      * just return without looking at the packet.  If it is,
 684      * the protocol becomes the first byte to "compress".
 685      */
 686     rptr = mtod(dmsg, u_char *);
 687     ent = PPP_PROTOCOL(rptr);
 688     if (ent < 0x21 || ent > 0xf9)
 689         return;
 690
 691     db->seqno++;
 692     ilen = 1;           /* count the protocol as 1 byte */
 693     rptr += PPP_HDRLEN;
 694     slen = dmsg->m_len - PPP_HDRLEN;
 695     for (;;) {
 696         if (slen <= 0) {
 697             dmsg = dmsg->m_next;
 698             if (!dmsg)
 699                 break;
 700             rptr = mtod(dmsg, u_char *);
 701             slen = dmsg->m_len;
 702             continue;
 703         }
 704         ilen += slen;
 705
 706         do {
 707             c = *rptr++;
 708             fcode = BSD_KEY(ent, c);
 709             hval = BSD_HASH(ent, c, hshift);
 710             dictp = &db->dict[hval];
 711
 712             /* validate and then check the entry */
 713             if (dictp->codem1 >= max_ent)
 714                 goto nomatch;
 715             if (dictp->f.fcode == fcode) {
 716                 ent = dictp->codem1+1;
 717                 continue;   /* found (prefix,suffix) */
 718             }
 719
 720             /* continue probing until a match or invalid entry */
 721             disp = (hval == 0) ? 1 : hval;
 722             do {
 723                 hval += disp;
 724                 if (hval >= db->hsize)
 725                     hval -= db->hsize;
 726                 dictp = &db->dict[hval];
 727                 if (dictp->codem1 >= max_ent)
 728                     goto nomatch;
 729             } while (dictp->f.fcode != fcode);
 730             ent = dictp->codem1+1;
 731             continue;   /* finally found (prefix,suffix) */
 732
 733         nomatch:                /* output (count) the prefix */
 734             bitno += n_bits;
 735
 736             /* code -> hashtable */
 737             if (max_ent < db->maxmaxcode) {
 738                 struct bsd_dict *dictp2;
 739                 /* expand code size if needed */
 740                 if (max_ent >= MAXCODE(n_bits))
 741                     db->n_bits = ++n_bits;
 742
 743                 /* Invalidate previous hash table entry
 744                  * assigned this code, and then take it over.
 745                  */
 746                 dictp2 = &db->dict[max_ent+1];
 747                 if (db->dict[dictp2->cptr].codem1 == max_ent)
 748                     db->dict[dictp2->cptr].codem1 = BADCODEM1;
 749                 dictp2->cptr = hval;
 750                 dictp->codem1 = max_ent;
 751                 dictp->f.fcode = fcode;
 752
 753                 db->max_ent = ++max_ent;
 754                 db->lens[max_ent] = db->lens[ent]+1;
 755             }
 756             ent = c;
 757         } while (--slen != 0);
 758     }
 759     bitno += n_bits;            /* output (count) the last code */
 760     db->bytes_out += bitno/8;
 761     db->in_count += ilen;
 762     bsd_check(db);
 763
 764     ++db->incomp_count;
 765     db->incomp_bytes += ilen;
 766     ++db->uncomp_count;
 767     db->uncomp_bytes += ilen;
 768
 769     /* Increase code size if we would have without the packet
 770      * boundary and as the decompressor will.
 771      */
 772     if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
 773         db->n_bits++;
 774 }
 775
 776
 777 /*
 778  * Decompress "BSD Compress".
 779  *
 780  * Because of patent problems, we return DECOMP_ERROR for errors
 781  * found by inspecting the input data and for system problems, but
 782  * DECOMP_FATALERROR for any errors which could possibly be said to
 783  * be being detected "after" decompression.  For DECOMP_ERROR,
 784  * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
 785  * infringing a patent of Motorola's if we do, so we take CCP down
 786  * instead.
 787  *
 788  * Given that the frame has the correct sequence number and a good FCS,
 789  * errors such as invalid codes in the input most likely indicate a
 790  * bug, so we return DECOMP_FATALERROR for them in order to turn off
 791  * compression, even though they are detected by inspecting the input.
 792  */
 793 int
 794 bsd_decompress(void *state, struct mbuf *cmp, struct mbuf **dmpp)
 795 {
 796     struct bsd_db *db = (struct bsd_db *) state;
 797     u_int max_ent = db->max_ent;
 798     u_int32_t accm = 0;
 799     u_int bitno = 32;           /* 1st valid bit in accm */
 800     u_int n_bits = db->n_bits;
 801     u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
 802     struct bsd_dict *dictp;
 803     int explen, i, seq, len;
 804     u_int incode, oldcode, finchar;
 805     u_char *p, *rptr, *wptr;
 806     struct mbuf *m, *dmp, *mret;
 807     int adrs, ctrl, ilen;
 808     int space, codelen, extra;
 809
 810     /*
 811      * Save the address/control from the PPP header
 812      * and then get the sequence number.
 813      */
 814     *dmpp = NULL;
 815     rptr = mtod(cmp, u_char *);
 816     adrs = PPP_ADDRESS(rptr);
 817     ctrl = PPP_CONTROL(rptr);
 818     rptr += PPP_HDRLEN;
 819     len = cmp->m_len - PPP_HDRLEN;
 820     seq = 0;
 821     for (i = 0; i < 2; ++i) {
 822         while (len <= 0) {
 823             cmp = cmp->m_next;
 824             if (cmp == NULL)
 825                 return DECOMP_ERROR;
 826             rptr = mtod(cmp, u_char *);
 827             len = cmp->m_len;
 828         }
 829         seq = (seq << 8) + *rptr++;
 830         --len;
 831     }
 832
 833     /*
 834      * Check the sequence number and give up if it differs from
 835      * the value we're expecting.
 836      */
 837     if (seq != db->seqno) {
 838         if (db->debug)
 839             kprintf("bsd_decomp%d: bad sequence # %d, expected %d\n",
 840                    db->unit, seq, db->seqno - 1);
 841         return DECOMP_ERROR;
 842     }
 843     ++db->seqno;
 844
 845     /*
 846      * Allocate one mbuf to start with.
 847      */
 848     MGETHDR(dmp, MB_DONTWAIT, MT_DATA);
 849     if (dmp == NULL)
 850         return DECOMP_ERROR;
 851     mret = dmp;
 852     dmp->m_len = 0;
 853     dmp->m_next = NULL;
 854     MCLGET(dmp, MB_DONTWAIT);
 855     dmp->m_data += db->hdrlen;
 856     wptr = mtod(dmp, u_char *);
 857     space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
 858
 859     /*
 860      * Fill in the ppp header, but not the last byte of the protocol
 861      * (that comes from the decompressed data).
 862      */
 863     wptr[0] = adrs;
 864     wptr[1] = ctrl;
 865     wptr[2] = 0;
 866     wptr += PPP_HDRLEN - 1;
 867
 868     ilen = len;
 869     oldcode = CLEAR;
 870     explen = 0;
 871     for (;;) {
 872         if (len == 0) {
 873             cmp = cmp->m_next;
 874             if (!cmp)           /* quit at end of message */
 875                 break;
 876             rptr = mtod(cmp, u_char *);
 877             len = cmp->m_len;
 878             ilen += len;
 879             continue;           /* handle 0-length buffers */
 880         }
 881
 882         /*
 883          * Accumulate bytes until we have a complete code.
 884          * Then get the next code, relying on the 32-bit,
 885          * unsigned accm to mask the result.
 886          */
 887         bitno -= 8;
 888         accm |= *rptr++ << bitno;
 889         --len;
 890         if (tgtbitno < bitno)
 891             continue;
 892         incode = accm >> tgtbitno;
 893         accm <<= n_bits;
 894         bitno += n_bits;
 895
 896         if (incode == CLEAR) {
 897             /*
 898              * The dictionary must only be cleared at
 899              * the end of a packet.  But there could be an
 900              * empty mbuf at the end.
 901              */
 902             if (len > 0 || cmp->m_next != NULL) {
 903                 while ((cmp = cmp->m_next) != NULL)
 904                     len += cmp->m_len;
 905                 if (len > 0) {
 906                     m_freem(mret);
 907                     if (db->debug)
 908                         kprintf("bsd_decomp%d: bad CLEAR\n", db->unit);
 909                     return DECOMP_FATALERROR;   /* probably a bug */
 910                 }
 911             }
 912             bsd_clear(db);
 913             explen = ilen = 0;
 914             break;
 915         }
 916
 917         if (incode > max_ent + 2 || incode > db->maxmaxcode
 918             || (incode > max_ent && oldcode == CLEAR)) {
 919             m_freem(mret);
 920             if (db->debug) {
 921                 kprintf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
 922                        db->unit, incode, oldcode);
 923                 kprintf("max_ent=0x%x explen=%d seqno=%d\n",
 924                        max_ent, explen, db->seqno);
 925             }
 926             return DECOMP_FATALERROR;   /* probably a bug */
 927         }
 928
 929         /* Special case for KwKwK string. */
 930         if (incode > max_ent) {
 931             finchar = oldcode;
 932             extra = 1;
 933         } else {
 934             finchar = incode;
 935             extra = 0;
 936         }
 937
 938         codelen = db->lens[finchar];
 939         explen += codelen + extra;
 940         if (explen > db->mru + 1) {
 941             m_freem(mret);
 942             if (db->debug) {
 943                 kprintf("bsd_decomp%d: ran out of mru\n", db->unit);
 944 #ifdef DEBUG
 945                 while ((cmp = cmp->m_next) != NULL)
 946                     len += cmp->m_len;
 947                 kprintf("  len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
 948                        len, finchar, codelen, explen);
 949 #endif
 950             }
 951             return DECOMP_FATALERROR;
 952         }
 953
 954         /*
 955          * For simplicity, the decoded characters go in a single mbuf,
 956          * so we allocate a single extra cluster mbuf if necessary.
 957          */
 958         if ((space -= codelen + extra) < 0) {
 959             dmp->m_len = wptr - mtod(dmp, u_char *);
 960             MGET(m, MB_DONTWAIT, MT_DATA);
 961             if (m == NULL) {
 962                 m_freem(mret);
 963                 return DECOMP_ERROR;
 964             }
 965             m->m_len = 0;
 966             m->m_next = NULL;
 967             dmp->m_next = m;
 968             MCLGET(m, MB_DONTWAIT);
 969             space = M_TRAILINGSPACE(m) - (codelen + extra);
 970             if (space < 0) {
 971                 /* now that's what I call *compression*. */
 972                 m_freem(mret);
 973                 return DECOMP_ERROR;
 974             }
 975             dmp = m;
 976             wptr = mtod(dmp, u_char *);
 977         }
 978
 979         /*
 980          * Decode this code and install it in the decompressed buffer.
 981          */
 982         p = (wptr += codelen);
 983         while (finchar > LAST) {
 984             dictp = &db->dict[db->dict[finchar].cptr];
 985 #ifdef DEBUG
 986             if (--codelen <= 0 || dictp->codem1 != finchar-1)
 987                 goto bad;
 988 #endif
 989             *--p = dictp->f.hs.suffix;
 990             finchar = dictp->f.hs.prefix;
 991         }
 992         *--p = finchar;
 993
 994 #ifdef DEBUG
 995         if (--codelen != 0)
 996             kprintf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
 997                    db->unit, codelen, incode, max_ent);
 998 #endif
 999
1000         if (extra)              /* the KwKwK case again */
1001             *wptr++ = finchar;
1002
1003         /*
1004          * If not first code in a packet, and
1005          * if not out of code space, then allocate a new code.
1006          *
1007          * Keep the hash table correct so it can be used
1008          * with uncompressed packets.
1009          */
1010         if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1011             struct bsd_dict *dictp2;
1012             u_int32_t fcode;
1013             u_int32_t hval, disp;
1014
1015             fcode = BSD_KEY(oldcode,finchar);
1016             hval = BSD_HASH(oldcode,finchar,db->hshift);
1017             dictp = &db->dict[hval];
1018
1019             /* look for a free hash table entry */
1020             if (dictp->codem1 < max_ent) {
1021                 disp = (hval == 0) ? 1 : hval;
1022                 do {
1023                     hval += disp;
1024                     if (hval >= db->hsize)
1025                         hval -= db->hsize;
1026                     dictp = &db->dict[hval];
1027                 } while (dictp->codem1 < max_ent);
1028             }
1029
1030             /*
1031              * Invalidate previous hash table entry
1032              * assigned this code, and then take it over
1033              */
1034             dictp2 = &db->dict[max_ent+1];
1035             if (db->dict[dictp2->cptr].codem1 == max_ent) {
1036                 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1037             }
1038             dictp2->cptr = hval;
1039             dictp->codem1 = max_ent;
1040             dictp->f.fcode = fcode;
1041
1042             db->max_ent = ++max_ent;
1043             db->lens[max_ent] = db->lens[oldcode]+1;
1044
1045             /* Expand code size if needed. */
1046             if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1047                 db->n_bits = ++n_bits;
1048                 tgtbitno = 32-n_bits;
1049             }
1050         }
1051         oldcode = incode;
1052     }
1053     dmp->m_len = wptr - mtod(dmp, u_char *);
1054
1055     /*
1056      * Keep the checkpoint right so that incompressible packets
1057      * clear the dictionary at the right times.
1058      */
1059     db->bytes_out += ilen;
1060     db->in_count += explen;
1061     if (bsd_check(db) && db->debug) {
1062         kprintf("bsd_decomp%d: peer should have cleared dictionary\n",
1063                db->unit);
1064     }
1065
1066     ++db->comp_count;
1067     db->comp_bytes += ilen + BSD_OVHD;
1068     ++db->uncomp_count;
1069     db->uncomp_bytes += explen;
1070
1071     *dmpp = mret;
1072     return DECOMP_OK;
1073
1074 #ifdef DEBUG
1075  bad:
1076     if (codelen <= 0) {
1077         kprintf("bsd_decomp%d: fell off end of chain ", db->unit);
1078         kprintf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1079                incode, finchar, db->dict[finchar].cptr, max_ent);
1080     } else if (dictp->codem1 != finchar-1) {
1081         kprintf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1082                db->unit, incode, finchar);
1083         kprintf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1084                db->dict[finchar].cptr, dictp->codem1);
1085     }
1086     m_freem(mret);
1087     return DECOMP_FATALERROR;
1088 #endif /* DEBUG */
1089 }
1090 #endif /* DO_BSD_COMPRESS */