linux-old/drivers/net/bsd_comp.c
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   1/*
   2 * Update: The Berkeley copyright was changed, and the change 
   3 * is retroactive to all "true" BSD software (ie everything
   4 * from UCB as opposed to other peoples code that just carried
   5 * the same license). The new copyright doesn't clash with the
   6 * GPL, so the module-only restriction has been removed..
   7 */
   8
   9/* Because this code is derived from the 4.3BSD compress source:
  10 *
  11 * Copyright (c) 1985, 1986 The Regents of the University of California.
  12 * All rights reserved.
  13 *
  14 * This code is derived from software contributed to Berkeley by
  15 * James A. Woods, derived from original work by Spencer Thomas
  16 * and Joseph Orost.
  17 *
  18 * Redistribution and use in source and binary forms, with or without
  19 * modification, are permitted provided that the following conditions
  20 * are met:
  21 * 1. Redistributions of source code must retain the above copyright
  22 *    notice, this list of conditions and the following disclaimer.
  23 * 2. Redistributions in binary form must reproduce the above copyright
  24 *    notice, this list of conditions and the following disclaimer in the
  25 *    documentation and/or other materials provided with the distribution.
  26 * 3. All advertising materials mentioning features or use of this software
  27 *    must display the following acknowledgement:
  28 *      This product includes software developed by the University of
  29 *      California, Berkeley and its contributors.
  30 * 4. Neither the name of the University nor the names of its contributors
  31 *    may be used to endorse or promote products derived from this software
  32 *    without specific prior written permission.
  33 *
  34 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  35 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  36 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  37 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  38 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  39 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  40 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  41 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  42 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  43 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  44 * SUCH DAMAGE.
  45 */
  46
  47/*
  48 * This version is for use with contiguous buffers on Linux-derived systems.
  49 *
  50 *  ==FILEVERSION 20000226==
  51 *
  52 *  NOTE TO MAINTAINERS:
  53 *     If you modify this file at all, please set the number above to the
  54 *     date of the modification as YYMMDD (year month day).
  55 *     bsd_comp.c is shipped with a PPP distribution as well as with
  56 *     the kernel; if everyone increases the FILEVERSION number above,
  57 *     then scripts can do the right thing when deciding whether to
  58 *     install a new bsd_comp.c file. Don't change the format of that
  59 *     line otherwise, so the installation script can recognize it.
  60 *
  61 * From: bsd_comp.c,v 1.3 1994/12/08 01:59:58 paulus Exp
  62 */
  63
  64#include <linux/module.h>
  65#include <linux/init.h>
  66#include <linux/malloc.h>
  67#include <linux/vmalloc.h>
  68
  69#include <linux/ppp_defs.h>
  70
  71#undef   PACKETPTR
  72#define  PACKETPTR 1
  73#include <linux/ppp-comp.h>
  74#undef   PACKETPTR
  75
  76/*
  77 * PPP "BSD compress" compression
  78 *  The differences between this compression and the classic BSD LZW
  79 *  source are obvious from the requirement that the classic code worked
  80 *  with files while this handles arbitrarily long streams that
  81 *  are broken into packets.  They are:
  82 *
  83 *      When the code size expands, a block of junk is not emitted by
  84 *          the compressor and not expected by the decompressor.
  85 *
  86 *      New codes are not necessarily assigned every time an old
  87 *          code is output by the compressor.  This is because a packet
  88 *          end forces a code to be emitted, but does not imply that a
  89 *          new sequence has been seen.
  90 *
  91 *      The compression ratio is checked at the first end of a packet
  92 *          after the appropriate gap.  Besides simplifying and speeding
  93 *          things up, this makes it more likely that the transmitter
  94 *          and receiver will agree when the dictionary is cleared when
  95 *          compression is not going well.
  96 */
  97
  98/*
  99 * Macros to extract protocol version and number of bits
 100 * from the third byte of the BSD Compress CCP configuration option.
 101 */
 102
 103#define BSD_VERSION(x)  ((x) >> 5)
 104#define BSD_NBITS(x)    ((x) & 0x1F)
 105
 106#define BSD_CURRENT_VERSION     1
 107
 108/*
 109 * A dictionary for doing BSD compress.
 110 */
 111
 112struct bsd_dict {
 113    union {                             /* hash value */
 114        unsigned long   fcode;
 115        struct {
 116#if defined(__LITTLE_ENDIAN)            /* Little endian order */
 117            unsigned short      prefix; /* preceding code */
 118            unsigned char       suffix; /* last character of new code */
 119            unsigned char       pad;
 120#elif defined(__BIG_ENDIAN)             /* Big endian order */
 121            unsigned char       pad;
 122            unsigned char       suffix; /* last character of new code */
 123            unsigned short      prefix; /* preceding code */
 124#else
 125#error Endianness not defined...
 126#endif
 127        } hs;
 128    } f;
 129    unsigned short codem1;              /* output of hash table -1 */
 130    unsigned short cptr;                /* map code to hash table entry */
 131};
 132
 133struct bsd_db {
 134    int     totlen;                     /* length of this structure */
 135    unsigned int   hsize;               /* size of the hash table */
 136    unsigned char  hshift;              /* used in hash function */
 137    unsigned char  n_bits;              /* current bits/code */
 138    unsigned char  maxbits;             /* maximum bits/code */
 139    unsigned char  debug;               /* non-zero if debug desired */
 140    unsigned char  unit;                /* ppp unit number */
 141    unsigned short seqno;               /* sequence # of next packet */
 142    unsigned int   mru;                 /* size of receive (decompress) bufr */
 143    unsigned int   maxmaxcode;          /* largest valid code */
 144    unsigned int   max_ent;             /* largest code in use */
 145    unsigned int   in_count;            /* uncompressed bytes, aged */
 146    unsigned int   bytes_out;           /* compressed bytes, aged */
 147    unsigned int   ratio;               /* recent compression ratio */
 148    unsigned int   checkpoint;          /* when to next check the ratio */
 149    unsigned int   clear_count;         /* times dictionary cleared */
 150    unsigned int   incomp_count;        /* incompressible packets */
 151    unsigned int   incomp_bytes;        /* incompressible bytes */
 152    unsigned int   uncomp_count;        /* uncompressed packets */
 153    unsigned int   uncomp_bytes;        /* uncompressed bytes */
 154    unsigned int   comp_count;          /* compressed packets */
 155    unsigned int   comp_bytes;          /* compressed bytes */
 156    unsigned short  *lens;              /* array of lengths of codes */
 157    struct bsd_dict *dict;              /* dictionary */
 158};
 159
 160#define BSD_OVHD        2               /* BSD compress overhead/packet */
 161#define MIN_BSD_BITS    9
 162#define BSD_INIT_BITS   MIN_BSD_BITS
 163#define MAX_BSD_BITS    15
 164
 165static void     bsd_free (void *state);
 166static void     *bsd_alloc(unsigned char *options, int opt_len, int decomp);
 167static void     *bsd_comp_alloc (unsigned char *options, int opt_len);
 168static void     *bsd_decomp_alloc (unsigned char *options, int opt_len);
 169
 170static int      bsd_init        (void *db, unsigned char *options,
 171                                 int opt_len, int unit, int debug, int decomp);
 172static int      bsd_comp_init   (void *state, unsigned char *options,
 173                                 int opt_len, int unit, int opthdr, int debug);
 174static int      bsd_decomp_init (void *state, unsigned char *options,
 175                                 int opt_len, int unit, int opthdr, int mru,
 176                                 int debug);
 177
 178static void     bsd_reset (void *state);
 179static void     bsd_comp_stats (void *state, struct compstat *stats);
 180
 181static int      bsd_compress (void *state, unsigned char *rptr,
 182                              unsigned char *obuf, int isize, int osize);
 183static void     bsd_incomp (void *state, unsigned char *ibuf, int icnt);
 184
 185static int      bsd_decompress (void *state, unsigned char *ibuf, int isize,
 186                                unsigned char *obuf, int osize);
 187
 188/* These are in ppp.c */
 189extern int  ppp_register_compressor   (struct compressor *cp);
 190extern void ppp_unregister_compressor (struct compressor *cp);
 191
 192/*
 193 * the next two codes should not be changed lightly, as they must not
 194 * lie within the contiguous general code space.
 195 */
 196#define CLEAR   256                     /* table clear output code */
 197#define FIRST   257                     /* first free entry */
 198#define LAST    255
 199
 200#define MAXCODE(b)      ((1 << (b)) - 1)
 201#define BADCODEM1       MAXCODE(MAX_BSD_BITS);
 202
 203#define BSD_HASH(prefix,suffix,hshift) ((((unsigned long)(suffix))<<(hshift)) \
 204                                         ^ (unsigned long)(prefix))
 205#define BSD_KEY(prefix,suffix)          ((((unsigned long)(suffix)) << 16) \
 206                                         + (unsigned long)(prefix))
 207
 208#define CHECK_GAP       10000           /* Ratio check interval */
 209
 210#define RATIO_SCALE_LOG 8
 211#define RATIO_SCALE     (1<<RATIO_SCALE_LOG)
 212#define RATIO_MAX       (0x7fffffff>>RATIO_SCALE_LOG)
 213
 214/*
 215 * clear the dictionary
 216 */
 217
 218static void
 219bsd_clear(struct bsd_db *db)
 220{
 221    db->clear_count++;
 222    db->max_ent      = FIRST-1;
 223    db->n_bits       = BSD_INIT_BITS;
 224    db->bytes_out    = 0;
 225    db->in_count     = 0;
 226    db->ratio        = 0;
 227    db->checkpoint   = CHECK_GAP;
 228}
 229
 230/*
 231 * If the dictionary is full, then see if it is time to reset it.
 232 *
 233 * Compute the compression ratio using fixed-point arithmetic
 234 * with 8 fractional bits.
 235 *
 236 * Since we have an infinite stream instead of a single file,
 237 * watch only the local compression ratio.
 238 *
 239 * Since both peers must reset the dictionary at the same time even in
 240 * the absence of CLEAR codes (while packets are incompressible), they
 241 * must compute the same ratio.
 242 */
 243
 244static int bsd_check (struct bsd_db *db)        /* 1=output CLEAR */
 245  {
 246    unsigned int new_ratio;
 247
 248    if (db->in_count >= db->checkpoint)
 249      {
 250        /* age the ratio by limiting the size of the counts */
 251        if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
 252          {
 253            db->in_count  -= (db->in_count  >> 2);
 254            db->bytes_out -= (db->bytes_out >> 2);
 255          }
 256        
 257        db->checkpoint = db->in_count + CHECK_GAP;
 258        
 259        if (db->max_ent >= db->maxmaxcode)
 260          {
 261            /* Reset the dictionary only if the ratio is worse,
 262             * or if it looks as if it has been poisoned
 263             * by incompressible data.
 264             *
 265             * This does not overflow, because
 266             *  db->in_count <= RATIO_MAX.
 267             */
 268
 269            new_ratio = db->in_count << RATIO_SCALE_LOG;
 270            if (db->bytes_out != 0)
 271              {
 272                new_ratio /= db->bytes_out;
 273              }
 274            
 275            if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
 276              {
 277                bsd_clear (db);
 278                return 1;
 279              }
 280            db->ratio = new_ratio;
 281          }
 282      }
 283    return 0;
 284  }
 285
 286/*
 287 * Return statistics.
 288 */
 289
 290static void bsd_comp_stats (void *state, struct compstat *stats)
 291  {
 292    struct bsd_db *db = (struct bsd_db *) state;
 293    
 294    stats->unc_bytes    = db->uncomp_bytes;
 295    stats->unc_packets  = db->uncomp_count;
 296    stats->comp_bytes   = db->comp_bytes;
 297    stats->comp_packets = db->comp_count;
 298    stats->inc_bytes    = db->incomp_bytes;
 299    stats->inc_packets  = db->incomp_count;
 300    stats->in_count     = db->in_count;
 301    stats->bytes_out    = db->bytes_out;
 302  }
 303
 304/*
 305 * Reset state, as on a CCP ResetReq.
 306 */
 307
 308static void bsd_reset (void *state)
 309  {
 310    struct bsd_db *db = (struct bsd_db *) state;
 311
 312    bsd_clear(db);
 313
 314    db->seqno       = 0;
 315    db->clear_count = 0;
 316  }
 317
 318/*
 319 * Release the compression structure
 320 */
 321
 322static void bsd_free (void *state)
 323  {
 324    struct bsd_db *db = (struct bsd_db *) state;
 325    
 326    if (db)
 327      {
 328/*
 329 * Release the dictionary
 330 */
 331        if (db->dict)
 332          {
 333            vfree (db->dict);
 334            db->dict = NULL;
 335          }
 336/*
 337 * Release the string buffer
 338 */
 339        if (db->lens)
 340          {
 341            vfree (db->lens);
 342            db->lens = NULL;
 343          }
 344/*
 345 * Finally release the structure itself.
 346 */
 347        kfree (db);
 348        MOD_DEC_USE_COUNT;
 349      }
 350  }
 351
 352/*
 353 * Allocate space for a (de) compressor.
 354 */
 355
 356static void *bsd_alloc (unsigned char *options, int opt_len, int decomp)
 357  {
 358    int bits;
 359    unsigned int hsize, hshift, maxmaxcode;
 360    struct bsd_db *db;
 361
 362    if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3
 363        || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
 364      {
 365        return NULL;
 366      }
 367
 368    bits = BSD_NBITS(options[2]);
 369
 370    switch (bits)
 371      {
 372    case 9:                     /* needs 82152 for both directions */
 373    case 10:                    /* needs 84144 */
 374    case 11:                    /* needs 88240 */
 375    case 12:                    /* needs 96432 */
 376        hsize = 5003;
 377        hshift = 4;
 378        break;
 379    case 13:                    /* needs 176784 */
 380        hsize = 9001;
 381        hshift = 5;
 382        break;
 383    case 14:                    /* needs 353744 */
 384        hsize = 18013;
 385        hshift = 6;
 386        break;
 387    case 15:                    /* needs 691440 */
 388        hsize = 35023;
 389        hshift = 7;
 390        break;
 391    case 16:                    /* needs 1366160--far too much, */
 392        /* hsize = 69001; */    /* and 69001 is too big for cptr */
 393        /* hshift = 8; */       /* in struct bsd_db */
 394        /* break; */
 395    default:
 396        return NULL;
 397      }
 398/*
 399 * Allocate the main control structure for this instance.
 400 */
 401    maxmaxcode = MAXCODE(bits);
 402    db         = (struct bsd_db *) kmalloc (sizeof (struct bsd_db),
 403                                            GFP_KERNEL);
 404    if (!db)
 405      {
 406        return NULL;
 407      }
 408
 409    memset (db, 0, sizeof(struct bsd_db));
 410/*
 411 * Allocate space for the dictionary. This may be more than one page in
 412 * length.
 413 */
 414    db->dict = (struct bsd_dict *) vmalloc (hsize *
 415                                            sizeof (struct bsd_dict));
 416    if (!db->dict)
 417      {
 418        bsd_free (db);
 419        return NULL;
 420      }
 421
 422    MOD_INC_USE_COUNT;
 423/*
 424 * If this is the compression buffer then there is no length data.
 425 */
 426    if (!decomp)
 427      {
 428        db->lens = NULL;
 429      }
 430/*
 431 * For decompression, the length information is needed as well.
 432 */
 433    else
 434      {
 435        db->lens = (unsigned short *) vmalloc ((maxmaxcode + 1) *
 436                                               sizeof (db->lens[0]));
 437        if (!db->lens)
 438          {
 439            bsd_free (db);
 440            return (NULL);
 441          }
 442      }
 443/*
 444 * Initialize the data information for the compression code
 445 */
 446    db->totlen     = sizeof (struct bsd_db)   +
 447                    (sizeof (struct bsd_dict) * hsize);
 448
 449    db->hsize      = hsize;
 450    db->hshift     = hshift;
 451    db->maxmaxcode = maxmaxcode;
 452    db->maxbits    = bits;
 453
 454    return (void *) db;
 455  }
 456
 457static void *bsd_comp_alloc (unsigned char *options, int opt_len)
 458  {
 459    return bsd_alloc (options, opt_len, 0);
 460  }
 461
 462static void *bsd_decomp_alloc (unsigned char *options, int opt_len)
 463  {
 464    return bsd_alloc (options, opt_len, 1);
 465  }
 466
 467/*
 468 * Initialize the database.
 469 */
 470
 471static int bsd_init (void *state, unsigned char *options,
 472                     int opt_len, int unit, int debug, int decomp)
 473  {
 474    struct bsd_db *db = state;
 475    int indx;
 476    
 477    if ((opt_len != 3) || (options[0] != CI_BSD_COMPRESS) || (options[1] != 3)
 478        || (BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
 479        || (BSD_NBITS(options[2]) != db->maxbits)
 480        || (decomp && db->lens == NULL))
 481      {
 482        return 0;
 483      }
 484
 485    if (decomp)
 486      {
 487        indx = LAST;
 488        do
 489          {
 490            db->lens[indx] = 1;
 491          }
 492        while (indx-- > 0);
 493      }
 494
 495    indx = db->hsize;
 496    while (indx-- != 0)
 497      {
 498        db->dict[indx].codem1 = BADCODEM1;
 499        db->dict[indx].cptr   = 0;
 500      }
 501
 502    db->unit = unit;
 503    db->mru  = 0;
 504#ifndef DEBUG
 505    if (debug)
 506#endif
 507      db->debug = 1;
 508    
 509    bsd_reset(db);
 510    
 511    return 1;
 512  }
 513
 514static int bsd_comp_init (void *state, unsigned char *options,
 515                          int opt_len, int unit, int opthdr, int debug)
 516  {
 517    return bsd_init (state, options, opt_len, unit, debug, 0);
 518  }
 519
 520static int bsd_decomp_init (void *state, unsigned char *options,
 521                            int opt_len, int unit, int opthdr, int mru,
 522                            int debug)
 523  {
 524    return bsd_init (state, options, opt_len, unit, debug, 1);
 525  }
 526
 527/*
 528 * Obtain pointers to the various structures in the compression tables
 529 */
 530
 531#define dict_ptrx(p,idx) &(p->dict[idx])
 532#define lens_ptrx(p,idx) &(p->lens[idx])
 533
 534#ifdef DEBUG
 535static unsigned short *lens_ptr(struct bsd_db *db, int idx)
 536  {
 537    if ((unsigned int) idx > (unsigned int) db->maxmaxcode)
 538      {
 539        printk ("<9>ppp: lens_ptr(%d) > max\n", idx);
 540        idx = 0;
 541      }
 542    return lens_ptrx (db, idx);
 543  }
 544
 545static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
 546  {
 547    if ((unsigned int) idx >= (unsigned int) db->hsize)
 548      {
 549        printk ("<9>ppp: dict_ptr(%d) > max\n", idx);
 550        idx = 0;
 551      }
 552    return dict_ptrx (db, idx);
 553  }
 554
 555#else
 556#define lens_ptr(db,idx) lens_ptrx(db,idx)
 557#define dict_ptr(db,idx) dict_ptrx(db,idx)
 558#endif
 559
 560/*
 561 * compress a packet
 562 *
 563 *      The result of this function is the size of the compressed
 564 *      packet. A zero is returned if the packet was not compressed
 565 *      for some reason, such as the size being larger than uncompressed.
 566 *
 567 *      One change from the BSD compress command is that when the
 568 *      code size expands, we do not output a bunch of padding.
 569 */
 570
 571static int bsd_compress (void *state, unsigned char *rptr, unsigned char *obuf,
 572                         int isize, int osize)
 573  {
 574    struct bsd_db *db;
 575    int hshift;
 576    unsigned int max_ent;
 577    unsigned int n_bits;
 578    unsigned int bitno;
 579    unsigned long accm;
 580    int ent;
 581    unsigned long fcode;
 582    struct bsd_dict *dictp;
 583    unsigned char c;
 584    int hval;
 585    int disp;
 586    int ilen;
 587    int mxcode;
 588    unsigned char *wptr;
 589    int olen;
 590
 591#define PUTBYTE(v)                      \
 592  {                                     \
 593    ++olen;                             \
 594    if (wptr)                           \
 595      {                                 \
 596        *wptr++ = (unsigned char) (v);  \
 597        if (olen >= osize)              \
 598          {                             \
 599            wptr = NULL;                \
 600          }                             \
 601      }                                 \
 602  }
 603
 604#define OUTPUT(ent)                     \
 605  {                                     \
 606    bitno -= n_bits;                    \
 607    accm |= ((ent) << bitno);           \
 608    do                                  \
 609      {                                 \
 610        PUTBYTE(accm >> 24);            \
 611        accm <<= 8;                     \
 612        bitno += 8;                     \
 613      }                                 \
 614    while (bitno <= 24);                \
 615  }
 616
 617  /*
 618   * If the protocol is not in the range we're interested in,
 619   * just return without compressing the packet.  If it is,
 620   * the protocol becomes the first byte to compress.
 621   */
 622
 623    ent = PPP_PROTOCOL(rptr);
 624    if (ent < 0x21 || ent > 0xf9)
 625      {
 626        return 0;
 627      }
 628
 629    db      = (struct bsd_db *) state;
 630    hshift  = db->hshift;
 631    max_ent = db->max_ent;
 632    n_bits  = db->n_bits;
 633    bitno   = 32;
 634    accm    = 0;
 635    mxcode  = MAXCODE (n_bits);
 636
 637    /* Initialize the output pointers */
 638    wptr  = obuf;
 639    olen  = PPP_HDRLEN + BSD_OVHD;
 640
 641    if (osize > isize)
 642      {
 643        osize = isize;
 644      }
 645
 646    /* This is the PPP header information */
 647    if (wptr)
 648      {
 649        *wptr++ = PPP_ADDRESS(rptr);
 650        *wptr++ = PPP_CONTROL(rptr);
 651        *wptr++ = 0;
 652        *wptr++ = PPP_COMP;
 653        *wptr++ = db->seqno >> 8;
 654        *wptr++ = db->seqno;
 655      }
 656
 657    /* Skip the input header */
 658    rptr  += PPP_HDRLEN;
 659    isize -= PPP_HDRLEN;
 660    ilen   = ++isize;   /* Low byte of protocol is counted as input */
 661
 662    while (--ilen > 0)
 663      {
 664        c     = *rptr++;
 665        fcode = BSD_KEY  (ent, c);
 666        hval  = BSD_HASH (ent, c, hshift);
 667        dictp = dict_ptr (db, hval);
 668        
 669        /* Validate and then check the entry. */
 670        if (dictp->codem1 >= max_ent)
 671          {
 672            goto nomatch;
 673          }
 674
 675        if (dictp->f.fcode == fcode)
 676          {
 677            ent = dictp->codem1 + 1;
 678            continue;   /* found (prefix,suffix) */
 679          }
 680        
 681        /* continue probing until a match or invalid entry */
 682        disp = (hval == 0) ? 1 : hval;
 683
 684        do
 685          {
 686            hval += disp;
 687            if (hval >= db->hsize)
 688              {
 689                hval -= db->hsize;
 690              }
 691            dictp = dict_ptr (db, hval);
 692            if (dictp->codem1 >= max_ent)
 693              {
 694                goto nomatch;
 695              }
 696          }
 697        while (dictp->f.fcode != fcode);
 698
 699        ent = dictp->codem1 + 1;        /* finally found (prefix,suffix) */
 700        continue;
 701        
 702nomatch:
 703        OUTPUT(ent);            /* output the prefix */
 704        
 705        /* code -> hashtable */
 706        if (max_ent < db->maxmaxcode)
 707          {
 708            struct bsd_dict *dictp2;
 709            struct bsd_dict *dictp3;
 710            int    indx;
 711
 712            /* expand code size if needed */
 713            if (max_ent >= mxcode)
 714              {
 715                db->n_bits = ++n_bits;
 716                mxcode     = MAXCODE (n_bits);
 717              }
 718            
 719            /* Invalidate old hash table entry using
 720             * this code, and then take it over.
 721             */
 722
 723            dictp2 = dict_ptr (db, max_ent + 1);
 724            indx   = dictp2->cptr;
 725            dictp3 = dict_ptr (db, indx);
 726
 727            if (dictp3->codem1 == max_ent)
 728              {
 729                dictp3->codem1 = BADCODEM1;
 730              }
 731
 732            dictp2->cptr   = hval;
 733            dictp->codem1  = max_ent;
 734            dictp->f.fcode = fcode;
 735            db->max_ent    = ++max_ent;
 736
 737            if (db->lens)
 738              {
 739                unsigned short *len1 = lens_ptr (db, max_ent);
 740                unsigned short *len2 = lens_ptr (db, ent);
 741                *len1 = *len2 + 1;
 742              }
 743          }
 744        ent = c;
 745      }
 746    
 747    OUTPUT(ent);                /* output the last code */
 748
 749    db->bytes_out    += olen - PPP_HDRLEN - BSD_OVHD;
 750    db->uncomp_bytes += isize;
 751    db->in_count     += isize;
 752    ++db->uncomp_count;
 753    ++db->seqno;
 754
 755    if (bitno < 32)
 756      {
 757        ++db->bytes_out; /* must be set before calling bsd_check */
 758      }
 759
 760    /*
 761     * Generate the clear command if needed
 762     */
 763
 764    if (bsd_check(db))
 765      {
 766        OUTPUT (CLEAR);
 767      }
 768    
 769    /*
 770     * Pad dribble bits of last code with ones.
 771     * Do not emit a completely useless byte of ones.
 772     */
 773
 774    if (bitno != 32)
 775      {
 776        PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
 777      }
 778    
 779    /*
 780     * Increase code size if we would have without the packet
 781     * boundary because the decompressor will do so.
 782     */
 783
 784    if (max_ent >= mxcode && max_ent < db->maxmaxcode)
 785      {
 786        db->n_bits++;
 787      }
 788
 789    /* If output length is too large then this is an incomplete frame. */
 790    if (wptr == NULL)
 791      {
 792        ++db->incomp_count;
 793        db->incomp_bytes += isize;
 794        olen              = 0;
 795      }
 796    else /* Count the number of compressed frames */
 797      {
 798        ++db->comp_count;
 799        db->comp_bytes += olen;
 800      }
 801
 802    /* Return the resulting output length */
 803    return olen;
 804#undef OUTPUT
 805#undef PUTBYTE
 806  }
 807
 808/*
 809 * Update the "BSD Compress" dictionary on the receiver for
 810 * incompressible data by pretending to compress the incoming data.
 811 */
 812
 813static void bsd_incomp (void *state, unsigned char *ibuf, int icnt)
 814  {
 815    (void) bsd_compress (state, ibuf, (char *) 0, icnt, 0);
 816  }
 817
 818/*
 819 * Decompress "BSD Compress".
 820 *
 821 * Because of patent problems, we return DECOMP_ERROR for errors
 822 * found by inspecting the input data and for system problems, but
 823 * DECOMP_FATALERROR for any errors which could possibly be said to
 824 * be being detected "after" decompression.  For DECOMP_ERROR,
 825 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
 826 * infringing a patent of Motorola's if we do, so we take CCP down
 827 * instead.
 828 *
 829 * Given that the frame has the correct sequence number and a good FCS,
 830 * errors such as invalid codes in the input most likely indicate a
 831 * bug, so we return DECOMP_FATALERROR for them in order to turn off
 832 * compression, even though they are detected by inspecting the input.
 833 */
 834
 835static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
 836                           unsigned char *obuf, int osize)
 837  {
 838    struct bsd_db *db;
 839    unsigned int max_ent;
 840    unsigned long accm;
 841    unsigned int bitno;         /* 1st valid bit in accm */
 842    unsigned int n_bits;
 843    unsigned int tgtbitno;      /* bitno when we have a code */
 844    struct bsd_dict *dictp;
 845    int explen;
 846    int seq;
 847    unsigned int incode;
 848    unsigned int oldcode;
 849    unsigned int finchar;
 850    unsigned char *p;
 851    unsigned char *wptr;
 852    int adrs;
 853    int ctrl;
 854    int ilen;
 855    int codelen;
 856    int extra;
 857
 858    db       = (struct bsd_db *) state;
 859    max_ent  = db->max_ent;
 860    accm     = 0;
 861    bitno    = 32;              /* 1st valid bit in accm */
 862    n_bits   = db->n_bits;
 863    tgtbitno = 32 - n_bits;     /* bitno when we have a code */
 864    
 865    /*
 866     * Save the address/control from the PPP header
 867     * and then get the sequence number.
 868     */
 869
 870    adrs  = PPP_ADDRESS (ibuf);
 871    ctrl  = PPP_CONTROL (ibuf);
 872
 873    seq   = (ibuf[4] << 8) + ibuf[5];
 874
 875    ibuf += (PPP_HDRLEN + 2);
 876    ilen  = isize - (PPP_HDRLEN + 2);
 877    
 878    /*
 879     * Check the sequence number and give up if it differs from
 880     * the value we're expecting.
 881     */
 882
 883    if (seq != db->seqno)
 884      {
 885        if (db->debug)
 886          {
 887            printk("bsd_decomp%d: bad sequence # %d, expected %d\n",
 888                   db->unit, seq, db->seqno - 1);
 889          }
 890        return DECOMP_ERROR;
 891      }
 892
 893    ++db->seqno;
 894    db->bytes_out += ilen;
 895
 896    /*
 897     * Fill in the ppp header, but not the last byte of the protocol
 898     * (that comes from the decompressed data).
 899     */
 900
 901    wptr    = obuf;
 902    *wptr++ = adrs;
 903    *wptr++ = ctrl;
 904    *wptr++ = 0;
 905    
 906    oldcode = CLEAR;
 907    explen  = 3;
 908
 909    /*
 910     * Keep the checkpoint correctly so that incompressible packets
 911     * clear the dictionary at the proper times.
 912     */
 913
 914    for (;;)
 915      {
 916        if (ilen-- <= 0)
 917          {
 918            db->in_count += (explen - 3); /* don't count the header */
 919            break;
 920          }
 921
 922        /*
 923         * Accumulate bytes until we have a complete code.
 924         * Then get the next code, relying on the 32-bit,
 925         * unsigned accm to mask the result.
 926         */
 927
 928        bitno -= 8;
 929        accm  |= *ibuf++ << bitno;
 930        if (tgtbitno < bitno)
 931          {
 932            continue;
 933          }
 934
 935        incode = accm >> tgtbitno;
 936        accm <<= n_bits;
 937        bitno += n_bits;
 938
 939        /*
 940         * The dictionary must only be cleared at the end of a packet.
 941         */
 942        
 943        if (incode == CLEAR)
 944          {
 945            if (ilen > 0)
 946              {
 947                if (db->debug)
 948                  {
 949                    printk("bsd_decomp%d: bad CLEAR\n", db->unit);
 950                  }
 951                return DECOMP_FATALERROR;       /* probably a bug */
 952              }
 953            
 954            bsd_clear(db);
 955            break;
 956          }
 957
 958        if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
 959            || (incode > max_ent && oldcode == CLEAR))
 960          {
 961            if (db->debug)
 962              {
 963                printk("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
 964                       db->unit, incode, oldcode);
 965                printk("max_ent=0x%x explen=%d seqno=%d\n",
 966                       max_ent, explen, db->seqno);
 967              }
 968            return DECOMP_FATALERROR;   /* probably a bug */
 969          }
 970        
 971        /* Special case for KwKwK string. */
 972        if (incode > max_ent)
 973          {
 974            finchar = oldcode;
 975            extra   = 1;
 976          }
 977        else
 978          {
 979            finchar = incode;
 980            extra   = 0;
 981          }
 982        
 983        codelen = *(lens_ptr (db, finchar));
 984        explen += codelen + extra;
 985        if (explen > osize)
 986          {
 987            if (db->debug)
 988              {
 989                printk("bsd_decomp%d: ran out of mru\n", db->unit);
 990#ifdef DEBUG
 991                printk("  len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
 992                       ilen, finchar, codelen, explen);
 993#endif
 994              }
 995            return DECOMP_FATALERROR;
 996          }
 997        
 998        /*
 999         * Decode this code and install it in the decompressed buffer.
1000         */
1001
1002        wptr += codelen;
1003        p     = wptr;
1004        while (finchar > LAST)
1005          {
1006            struct bsd_dict *dictp2 = dict_ptr (db, finchar);
1007            
1008            dictp = dict_ptr (db, dictp2->cptr);
1009#ifdef DEBUG
1010            if (--codelen <= 0 || dictp->codem1 != finchar-1)
1011              {
1012                if (codelen <= 0)
1013                  {
1014                    printk("bsd_decomp%d: fell off end of chain ", db->unit);
1015                    printk("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1016                           incode, finchar, dictp2->cptr, max_ent);
1017                  }
1018                else
1019                  {
1020                    if (dictp->codem1 != finchar-1)
1021                      {
1022                        printk("bsd_decomp%d: bad code chain 0x%x "
1023                               "finchar=0x%x ",
1024                               db->unit, incode, finchar);
1025
1026                        printk("oldcode=0x%x cptr=0x%x codem1=0x%x\n",
1027                               oldcode, dictp2->cptr, dictp->codem1);
1028                      }
1029                  }
1030                return DECOMP_FATALERROR;
1031              }
1032#endif
1033            *--p    = dictp->f.hs.suffix;
1034            finchar = dictp->f.hs.prefix;
1035          }
1036        *--p = finchar;
1037        
1038#ifdef DEBUG
1039        if (--codelen != 0)
1040          {
1041            printk("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1042                   db->unit, codelen, incode, max_ent);
1043          }
1044#endif
1045        
1046        if (extra)              /* the KwKwK case again */
1047          {
1048            *wptr++ = finchar;
1049          }
1050        
1051        /*
1052         * If not first code in a packet, and
1053         * if not out of code space, then allocate a new code.
1054         *
1055         * Keep the hash table correct so it can be used
1056         * with uncompressed packets.
1057         */
1058
1059        if (oldcode != CLEAR && max_ent < db->maxmaxcode)
1060          {
1061            struct bsd_dict *dictp2, *dictp3;
1062            unsigned short  *lens1,  *lens2;
1063            unsigned long fcode;
1064            int hval, disp, indx;
1065            
1066            fcode = BSD_KEY(oldcode,finchar);
1067            hval  = BSD_HASH(oldcode,finchar,db->hshift);
1068            dictp = dict_ptr (db, hval);
1069            
1070            /* look for a free hash table entry */
1071            if (dictp->codem1 < max_ent)
1072              {
1073                disp = (hval == 0) ? 1 : hval;
1074                do
1075                  {
1076                    hval += disp;
1077                    if (hval >= db->hsize)
1078                      {
1079                        hval -= db->hsize;
1080                      }
1081                    dictp = dict_ptr (db, hval);
1082                  }
1083                while (dictp->codem1 < max_ent);
1084              }
1085            
1086            /*
1087             * Invalidate previous hash table entry
1088             * assigned this code, and then take it over
1089             */
1090
1091            dictp2 = dict_ptr (db, max_ent + 1);
1092            indx   = dictp2->cptr;
1093            dictp3 = dict_ptr (db, indx);
1094
1095            if (dictp3->codem1 == max_ent)
1096              {
1097                dictp3->codem1 = BADCODEM1;
1098              }
1099
1100            dictp2->cptr   = hval;
1101            dictp->codem1  = max_ent;
1102            dictp->f.fcode = fcode;
1103            db->max_ent    = ++max_ent;
1104
1105            /* Update the length of this string. */
1106            lens1  = lens_ptr (db, max_ent);
1107            lens2  = lens_ptr (db, oldcode);
1108            *lens1 = *lens2 + 1;
1109            
1110            /* Expand code size if needed. */
1111            if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
1112              {
1113                db->n_bits = ++n_bits;
1114                tgtbitno   = 32-n_bits;
1115              }
1116          }
1117        oldcode = incode;
1118      }
1119
1120    ++db->comp_count;
1121    ++db->uncomp_count;
1122    db->comp_bytes   += isize - BSD_OVHD - PPP_HDRLEN;
1123    db->uncomp_bytes += explen;
1124
1125    if (bsd_check(db))
1126      {
1127        if (db->debug)
1128          {
1129            printk("bsd_decomp%d: peer should have cleared dictionary on %d\n",
1130                   db->unit, db->seqno - 1);
1131          }
1132      }
1133    return explen;
1134  }
1135     
1136/*************************************************************
1137 * Table of addresses for the BSD compression module
1138 *************************************************************/
1139
1140static struct compressor ppp_bsd_compress = {
1141    CI_BSD_COMPRESS,            /* compress_proto */
1142    bsd_comp_alloc,             /* comp_alloc */
1143    bsd_free,                   /* comp_free */
1144    bsd_comp_init,              /* comp_init */
1145    bsd_reset,                  /* comp_reset */
1146    bsd_compress,               /* compress */
1147    bsd_comp_stats,             /* comp_stat */
1148    bsd_decomp_alloc,           /* decomp_alloc */
1149    bsd_free,                   /* decomp_free */
1150    bsd_decomp_init,            /* decomp_init */
1151    bsd_reset,                  /* decomp_reset */
1152    bsd_decompress,             /* decompress */
1153    bsd_incomp,                 /* incomp */
1154    bsd_comp_stats              /* decomp_stat */
1155};
1156
1157/*************************************************************
1158 * Module support routines
1159 *************************************************************/
1160
1161int bsdcomp_init(void)
1162{
1163        int answer = ppp_register_compressor(&ppp_bsd_compress);
1164        if (answer == 0)
1165                printk(KERN_INFO "PPP BSD Compression module registered\n");
1166        return answer;
1167}
1168
1169void bsdcomp_cleanup(void)
1170{
1171        ppp_unregister_compressor(&ppp_bsd_compress);
1172}
1173
1174module_init(bsdcomp_init);
1175module_exit(bsdcomp_cleanup);
1176
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