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