drivers/isdn/i4l/isdn_bsdcomp.c

   1 /*
   2  * BSD compression module
   3  *
   4  * Patched version for ISDN syncPPP written 1997/1998 by Michael Hipp
   5  * The whole module is now SKB based.
   6  *
   7  */
   8
   9 /*
  10  * Update: The Berkeley copyright was changed, and the change
  11  * is retroactive to all "true" BSD software (ie everything
  12  * from UCB as opposed to other peoples code that just carried
  13  * the same license). The new copyright doesn't clash with the
  14  * GPL, so the module-only restriction has been removed..
  15  */
  16
  17 /*
  18  * Original copyright notice:
  19  *
  20  * Copyright (c) 1985, 1986 The Regents of the University of California.
  21  * All rights reserved.
  22  *
  23  * This code is derived from software contributed to Berkeley by
  24  * James A. Woods, derived from original work by Spencer Thomas
  25  * and Joseph Orost.
  26  *
  27  * Redistribution and use in source and binary forms, with or without
  28  * modification, are permitted provided that the following conditions
  29  * are met:
  30  * 1. Redistributions of source code must retain the above copyright
  31  *    notice, this list of conditions and the following disclaimer.
  32  * 2. Redistributions in binary form must reproduce the above copyright
  33  *    notice, this list of conditions and the following disclaimer in the
  34  *    documentation and/or other materials provided with the distribution.
  35  * 3. All advertising materials mentioning features or use of this software
  36  *    must display the following acknowledgement:
  37  *      This product includes software developed by the University of
  38  *      California, Berkeley and its contributors.
  39  * 4. Neither the name of the University nor the names of its contributors
  40  *    may be used to endorse or promote products derived from this software
  41  *    without specific prior written permission.
  42  *
  43  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  44  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  45  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  46  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  47  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  48  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  49  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  50  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  51  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  52  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  53  * SUCH DAMAGE.
  54  */
  55
  56 #include <linux/module.h>
  57 #include <linux/init.h>
  58 #include <linux/kernel.h>
  59 #include <linux/types.h>
  60 #include <linux/fcntl.h>
  61 #include <linux/interrupt.h>
  62 #include <linux/ptrace.h>
  63 #include <linux/ioport.h>
  64 #include <linux/in.h>
  65 #include <linux/slab.h>
  66 #include <linux/tty.h>
  67 #include <linux/errno.h>
  68 #include <linux/string.h>       /* used in new tty drivers */
  69 #include <linux/signal.h>       /* used in new tty drivers */
  70 #include <linux/bitops.h>
  71
  72 #include <asm/byteorder.h>
  73 #include <asm/types.h>
  74
  75 #include <linux/if.h>
  76
  77 #include <linux/if_ether.h>
  78 #include <linux/netdevice.h>
  79 #include <linux/skbuff.h>
  80 #include <linux/inet.h>
  81 #include <linux/ioctl.h>
  82 #include <linux/vmalloc.h>
  83
  84 #include <linux/ppp_defs.h>
  85
  86 #include <linux/isdn.h>
  87 #include <linux/isdn_ppp.h>
  88 #include <linux/ip.h>
  89 #include <linux/tcp.h>
  90 #include <linux/if_arp.h>
  91 #include <linux/ppp-comp.h>
  92
  93 #include "isdn_ppp.h"
  94
  95 MODULE_DESCRIPTION("ISDN4Linux: BSD Compression for PPP over ISDN");
  96 MODULE_LICENSE("Dual BSD/GPL");
  97
  98 #define BSD_VERSION(x)  ((x) >> 5)
  99 #define BSD_NBITS(x)    ((x) & 0x1F)
 100
 101 #define BSD_CURRENT_VERSION     1
 102
 103 #define DEBUG 1
 104
 105 /*
 106  * A dictionary for doing BSD compress.
 107  */
 108
 109 struct bsd_dict {
 110         u32 fcode;
 111         u16 codem1;             /* output of hash table -1 */
 112         u16 cptr;               /* map code to hash table entry */
 113 };
 114
 115 struct bsd_db {
 116         int            totlen;          /* length of this structure */
 117         unsigned int   hsize;           /* size of the hash table */
 118         unsigned char  hshift;          /* used in hash function */
 119         unsigned char  n_bits;          /* current bits/code */
 120         unsigned char  maxbits;         /* maximum bits/code */
 121         unsigned char  debug;           /* non-zero if debug desired */
 122         unsigned char  unit;            /* ppp unit number */
 123         u16 seqno;                      /* sequence # of next packet */
 124         unsigned int   mru;             /* size of receive (decompress) bufr */
 125         unsigned int   maxmaxcode;      /* largest valid code */
 126         unsigned int   max_ent;         /* largest code in use */
 127         unsigned int   in_count;        /* uncompressed bytes, aged */
 128         unsigned int   bytes_out;       /* compressed bytes, aged */
 129         unsigned int   ratio;           /* recent compression ratio */
 130         unsigned int   checkpoint;      /* when to next check the ratio */
 131         unsigned int   clear_count;     /* times dictionary cleared */
 132         unsigned int   incomp_count;    /* incompressible packets */
 133         unsigned int   incomp_bytes;    /* incompressible bytes */
 134         unsigned int   uncomp_count;    /* uncompressed packets */
 135         unsigned int   uncomp_bytes;    /* uncompressed bytes */
 136         unsigned int   comp_count;      /* compressed packets */
 137         unsigned int   comp_bytes;      /* compressed bytes */
 138         unsigned short  *lens;          /* array of lengths of codes */
 139         struct bsd_dict *dict;          /* dictionary */
 140         int xmit;
 141 };
 142
 143 #define BSD_OVHD        2               /* BSD compress overhead/packet */
 144 #define MIN_BSD_BITS    9
 145 #define BSD_INIT_BITS   MIN_BSD_BITS
 146 #define MAX_BSD_BITS    15
 147
 148 /*
 149  * the next two codes should not be changed lightly, as they must not
 150  * lie within the contiguous general code space.
 151  */
 152 #define CLEAR   256                     /* table clear output code */
 153 #define FIRST   257                     /* first free entry */
 154 #define LAST    255
 155
 156 #define MAXCODE(b)      ((1 << (b)) - 1)
 157 #define BADCODEM1       MAXCODE(MAX_BSD_BITS)
 158
 159 #define BSD_HASH(prefix, suffix, hshift) ((((unsigned long)(suffix)) << (hshift)) \
 160                                           ^ (unsigned long)(prefix))
 161 #define BSD_KEY(prefix, suffix)         ((((unsigned long)(suffix)) << 16) \
 162                                          + (unsigned long)(prefix))
 163
 164 #define CHECK_GAP       10000           /* Ratio check interval */
 165
 166 #define RATIO_SCALE_LOG 8
 167 #define RATIO_SCALE     (1 << RATIO_SCALE_LOG)
 168 #define RATIO_MAX       (0x7fffffff >> RATIO_SCALE_LOG)
 169
 170 /*
 171  * clear the dictionary
 172  */
 173
 174 static void bsd_clear(struct bsd_db *db)
 175 {
 176         db->clear_count++;
 177         db->max_ent      = FIRST - 1;
 178         db->n_bits       = BSD_INIT_BITS;
 179         db->bytes_out    = 0;
 180         db->in_count     = 0;
 181         db->incomp_count = 0;
 182         db->ratio            = 0;
 183         db->checkpoint   = CHECK_GAP;
 184 }
 185
 186 /*
 187  * If the dictionary is full, then see if it is time to reset it.
 188  *
 189  * Compute the compression ratio using fixed-point arithmetic
 190  * with 8 fractional bits.
 191  *
 192  * Since we have an infinite stream instead of a single file,
 193  * watch only the local compression ratio.
 194  *
 195  * Since both peers must reset the dictionary at the same time even in
 196  * the absence of CLEAR codes (while packets are incompressible), they
 197  * must compute the same ratio.
 198  */
 199 static int bsd_check(struct bsd_db *db) /* 1=output CLEAR */
 200 {
 201         unsigned int new_ratio;
 202
 203         if (db->in_count >= db->checkpoint)
 204         {
 205                 /* age the ratio by limiting the size of the counts */
 206                 if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
 207                 {
 208                         db->in_count  -= (db->in_count  >> 2);
 209                         db->bytes_out -= (db->bytes_out >> 2);
 210                 }
 211
 212                 db->checkpoint = db->in_count + CHECK_GAP;
 213
 214                 if (db->max_ent >= db->maxmaxcode)
 215                 {
 216                         /* Reset the dictionary only if the ratio is worse,
 217                          * or if it looks as if it has been poisoned
 218                          * by incompressible data.
 219                          *
 220                          * This does not overflow, because
 221                          *      db->in_count <= RATIO_MAX.
 222                          */
 223
 224                         new_ratio = db->in_count << RATIO_SCALE_LOG;
 225                         if (db->bytes_out != 0)
 226                         {
 227                                 new_ratio /= db->bytes_out;
 228                         }
 229
 230                         if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
 231                         {
 232                                 bsd_clear(db);
 233                                 return 1;
 234                         }
 235                         db->ratio = new_ratio;
 236                 }
 237         }
 238         return 0;
 239 }
 240
 241 /*
 242  * Return statistics.
 243  */
 244
 245 static void bsd_stats(void *state, struct compstat *stats)
 246 {
 247         struct bsd_db *db = (struct bsd_db *) state;
 248
 249         stats->unc_bytes    = db->uncomp_bytes;
 250         stats->unc_packets  = db->uncomp_count;
 251         stats->comp_bytes   = db->comp_bytes;
 252         stats->comp_packets = db->comp_count;
 253         stats->inc_bytes    = db->incomp_bytes;
 254         stats->inc_packets  = db->incomp_count;
 255         stats->in_count     = db->in_count;
 256         stats->bytes_out    = db->bytes_out;
 257 }
 258
 259 /*
 260  * Reset state, as on a CCP ResetReq.
 261  */
 262 static void bsd_reset(void *state, unsigned char code, unsigned char id,
 263                       unsigned char *data, unsigned len,
 264                       struct isdn_ppp_resetparams *rsparm)
 265 {
 266         struct bsd_db *db = (struct bsd_db *) state;
 267
 268         bsd_clear(db);
 269         db->seqno       = 0;
 270         db->clear_count = 0;
 271 }
 272
 273 /*
 274  * Release the compression structure
 275  */
 276 static void bsd_free(void *state)
 277 {
 278         struct bsd_db *db = (struct bsd_db *) state;
 279
 280         if (db) {
 281                 /*
 282                  * Release the dictionary
 283                  */
 284                 vfree(db->dict);
 285                 db->dict = NULL;
 286
 287                 /*
 288                  * Release the string buffer
 289                  */
 290                 vfree(db->lens);
 291                 db->lens = NULL;
 292
 293                 /*
 294                  * Finally release the structure itself.
 295                  */
 296                 kfree(db);
 297         }
 298 }
 299
 300
 301 /*
 302  * Allocate space for a (de) compressor.
 303  */
 304 static void *bsd_alloc(struct isdn_ppp_comp_data *data)
 305 {
 306         int bits;
 307         unsigned int hsize, hshift, maxmaxcode;
 308         struct bsd_db *db;
 309         int decomp;
 310
 311         static unsigned int htab[][2] = {
 312                 { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } ,
 313                 { 9001 , 5 } , { 18013 , 6 } , { 35023 , 7 } , { 69001 , 8 }
 314         };
 315
 316         if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
 317             || BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
 318                 return NULL;
 319
 320         bits = BSD_NBITS(data->options[0]);
 321
 322         if (bits < 9 || bits > 15)
 323                 return NULL;
 324
 325         hsize = htab[bits - 9][0];
 326         hshift = htab[bits - 9][1];
 327
 328         /*
 329          * Allocate the main control structure for this instance.
 330          */
 331         maxmaxcode = MAXCODE(bits);
 332         db = kzalloc(sizeof(struct bsd_db), GFP_KERNEL);
 333         if (!db)
 334                 return NULL;
 335
 336         db->xmit = data->flags & IPPP_COMP_FLAG_XMIT;
 337         decomp = db->xmit ? 0 : 1;
 338
 339         /*
 340          * Allocate space for the dictionary. This may be more than one page in
 341          * length.
 342          */
 343         db->dict = vmalloc(hsize * sizeof(struct bsd_dict));
 344         if (!db->dict) {
 345                 bsd_free(db);
 346                 return NULL;
 347         }
 348
 349         /*
 350          * If this is the compression buffer then there is no length data.
 351          * For decompression, the length information is needed as well.
 352          */
 353         if (!decomp)
 354                 db->lens = NULL;
 355         else {
 356                 db->lens = vmalloc((maxmaxcode + 1) * sizeof(db->lens[0]));
 357                 if (!db->lens) {
 358                         bsd_free(db);
 359                         return (NULL);
 360                 }
 361         }
 362
 363         /*
 364          * Initialize the data information for the compression code
 365          */
 366         db->totlen = sizeof(struct bsd_db) + (sizeof(struct bsd_dict) * hsize);
 367         db->hsize = hsize;
 368         db->hshift = hshift;
 369         db->maxmaxcode = maxmaxcode;
 370         db->maxbits = bits;
 371
 372         return (void *)db;
 373 }
 374
 375 /*
 376  * Initialize the database.
 377  */
 378 static int bsd_init(void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
 379 {
 380         struct bsd_db *db = state;
 381         int indx;
 382         int decomp;
 383
 384         if (!state || !data) {
 385                 printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n", unit, (long)state, (long)data);
 386                 return 0;
 387         }
 388
 389         decomp = db->xmit ? 0 : 1;
 390
 391         if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
 392             || (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
 393             || (BSD_NBITS(data->options[0]) != db->maxbits)
 394             || (decomp && db->lens == NULL)) {
 395                 printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n", data->optlen, data->num, data->options[0], decomp, (unsigned long)db->lens);
 396                 return 0;
 397         }
 398
 399         if (decomp)
 400                 for (indx = LAST; indx >= 0; indx--)
 401                         db->lens[indx] = 1;
 402
 403         indx = db->hsize;
 404         while (indx-- != 0) {
 405                 db->dict[indx].codem1 = BADCODEM1;
 406                 db->dict[indx].cptr   = 0;
 407         }
 408
 409         db->unit = unit;
 410         db->mru  = 0;
 411
 412         db->debug = 1;
 413
 414         bsd_reset(db, 0, 0, NULL, 0, NULL);
 415
 416         return 1;
 417 }
 418
 419 /*
 420  * Obtain pointers to the various structures in the compression tables
 421  */
 422
 423 #define dict_ptrx(p, idx) &(p->dict[idx])
 424 #define lens_ptrx(p, idx) &(p->lens[idx])
 425
 426 #ifdef DEBUG
 427 static unsigned short *lens_ptr(struct bsd_db *db, int idx)
 428 {
 429         if ((unsigned int) idx > (unsigned int) db->maxmaxcode) {
 430                 printk(KERN_DEBUG "<9>ppp: lens_ptr(%d) > max\n", idx);
 431                 idx = 0;
 432         }
 433         return lens_ptrx(db, idx);
 434 }
 435
 436 static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
 437 {
 438         if ((unsigned int) idx >= (unsigned int) db->hsize) {
 439                 printk(KERN_DEBUG "<9>ppp: dict_ptr(%d) > max\n", idx);
 440                 idx = 0;
 441         }
 442         return dict_ptrx(db, idx);
 443 }
 444
 445 #else
 446 #define lens_ptr(db, idx) lens_ptrx(db, idx)
 447 #define dict_ptr(db, idx) dict_ptrx(db, idx)
 448 #endif
 449
 450 /*
 451  * compress a packet
 452  */
 453 static int bsd_compress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out, int proto)
 454 {
 455         struct bsd_db *db;
 456         int hshift;
 457         unsigned int max_ent;
 458         unsigned int n_bits;
 459         unsigned int bitno;
 460         unsigned long accm;
 461         int ent;
 462         unsigned long fcode;
 463         struct bsd_dict *dictp;
 464         unsigned char c;
 465         int hval, disp, ilen, mxcode;
 466         unsigned char *rptr = skb_in->data;
 467         int isize = skb_in->len;
 468
 469 #define OUTPUT(ent)                                                     \
 470         {                                                               \
 471                 bitno -= n_bits;                                        \
 472                 accm |= ((ent) << bitno);                               \
 473                 do      {                                               \
 474                         if (skb_out && skb_tailroom(skb_out) > 0)       \
 475                                 skb_put_u8(skb_out, (u8)(accm >> 24));  \
 476                         accm <<= 8;                                     \
 477                         bitno += 8;                                     \
 478                 } while (bitno <= 24);                                  \
 479         }
 480
 481         /*
 482          * If the protocol is not in the range we're interested in,
 483          * just return without compressing the packet.  If it is,
 484          * the protocol becomes the first byte to compress.
 485          */
 486         printk(KERN_DEBUG "bsd_compress called with %x\n", proto);
 487
 488         ent = proto;
 489         if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1))
 490                 return 0;
 491
 492         db      = (struct bsd_db *) state;
 493         hshift  = db->hshift;
 494         max_ent = db->max_ent;
 495         n_bits  = db->n_bits;
 496         bitno   = 32;
 497         accm    = 0;
 498         mxcode  = MAXCODE(n_bits);
 499
 500         /* This is the PPP header information */
 501         if (skb_out && skb_tailroom(skb_out) >= 2) {
 502                 char *v = skb_put(skb_out, 2);
 503                 /* we only push our own data on the header,
 504                    AC,PC and protos is pushed by caller  */
 505                 v[0] = db->seqno >> 8;
 506                 v[1] = db->seqno;
 507         }
 508
 509         ilen = ++isize; /* This is off by one, but that is what is in draft! */
 510
 511         while (--ilen > 0) {
 512                 c = *rptr++;
 513                 fcode = BSD_KEY(ent, c);
 514                 hval = BSD_HASH(ent, c, hshift);
 515                 dictp = dict_ptr(db, hval);
 516
 517                 /* Validate and then check the entry. */
 518                 if (dictp->codem1 >= max_ent)
 519                         goto nomatch;
 520
 521                 if (dictp->fcode == fcode) {
 522                         ent = dictp->codem1 + 1;
 523                         continue;       /* found (prefix,suffix) */
 524                 }
 525
 526                 /* continue probing until a match or invalid entry */
 527                 disp = (hval == 0) ? 1 : hval;
 528
 529                 do {
 530                         hval += disp;
 531                         if (hval >= db->hsize)
 532                                 hval -= db->hsize;
 533                         dictp = dict_ptr(db, hval);
 534                         if (dictp->codem1 >= max_ent)
 535                                 goto nomatch;
 536                 } while (dictp->fcode != fcode);
 537
 538                 ent = dictp->codem1 + 1;        /* finally found (prefix,suffix) */
 539                 continue;
 540
 541         nomatch:
 542                 OUTPUT(ent);            /* output the prefix */
 543
 544                 /* code -> hashtable */
 545                 if (max_ent < db->maxmaxcode) {
 546                         struct bsd_dict *dictp2;
 547                         struct bsd_dict *dictp3;
 548                         int indx;
 549
 550                         /* expand code size if needed */
 551                         if (max_ent >= mxcode) {
 552                                 db->n_bits = ++n_bits;
 553                                 mxcode = MAXCODE(n_bits);
 554                         }
 555
 556                         /*
 557                          * Invalidate old hash table entry using
 558                          * this code, and then take it over.
 559                          */
 560                         dictp2 = dict_ptr(db, max_ent + 1);
 561                         indx   = dictp2->cptr;
 562                         dictp3 = dict_ptr(db, indx);
 563
 564                         if (dictp3->codem1 == max_ent)
 565                                 dictp3->codem1 = BADCODEM1;
 566
 567                         dictp2->cptr   = hval;
 568                         dictp->codem1  = max_ent;
 569                         dictp->fcode = fcode;
 570                         db->max_ent    = ++max_ent;
 571
 572                         if (db->lens) {
 573                                 unsigned short *len1 = lens_ptr(db, max_ent);
 574                                 unsigned short *len2 = lens_ptr(db, ent);
 575                                 *len1 = *len2 + 1;
 576                         }
 577                 }
 578                 ent = c;
 579         }
 580
 581         OUTPUT(ent);            /* output the last code */
 582
 583         if (skb_out)
 584                 db->bytes_out    += skb_out->len; /* Do not count bytes from here */
 585         db->uncomp_bytes += isize;
 586         db->in_count     += isize;
 587         ++db->uncomp_count;
 588         ++db->seqno;
 589
 590         if (bitno < 32)
 591                 ++db->bytes_out; /* must be set before calling bsd_check */
 592
 593         /*
 594          * Generate the clear command if needed
 595          */
 596
 597         if (bsd_check(db))
 598                 OUTPUT(CLEAR);
 599
 600         /*
 601          * Pad dribble bits of last code with ones.
 602          * Do not emit a completely useless byte of ones.
 603          */
 604         if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0)
 605                 skb_put_u8(skb_out,
 606                            (unsigned char)((accm | (0xff << (bitno - 8))) >> 24));
 607
 608         /*
 609          * Increase code size if we would have without the packet
 610          * boundary because the decompressor will do so.
 611          */
 612         if (max_ent >= mxcode && max_ent < db->maxmaxcode)
 613                 db->n_bits++;
 614
 615         /* If output length is too large then this is an incompressible frame. */
 616         if (!skb_out || skb_out->len >= skb_in->len) {
 617                 ++db->incomp_count;
 618                 db->incomp_bytes += isize;
 619                 return 0;
 620         }
 621
 622         /* Count the number of compressed frames */
 623         ++db->comp_count;
 624         db->comp_bytes += skb_out->len;
 625         return skb_out->len;
 626
 627 #undef OUTPUT
 628 }
 629
 630 /*
 631  * Update the "BSD Compress" dictionary on the receiver for
 632  * incompressible data by pretending to compress the incoming data.
 633  */
 634 static void bsd_incomp(void *state, struct sk_buff *skb_in, int proto)
 635 {
 636         bsd_compress(state, skb_in, NULL, proto);
 637 }
 638
 639 /*
 640  * Decompress "BSD Compress".
 641  */
 642 static int bsd_decompress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,
 643                           struct isdn_ppp_resetparams *rsparm)
 644 {
 645         struct bsd_db *db;
 646         unsigned int max_ent;
 647         unsigned long accm;
 648         unsigned int bitno;             /* 1st valid bit in accm */
 649         unsigned int n_bits;
 650         unsigned int tgtbitno;  /* bitno when we have a code */
 651         struct bsd_dict *dictp;
 652         int seq;
 653         unsigned int incode;
 654         unsigned int oldcode;
 655         unsigned int finchar;
 656         unsigned char *p, *ibuf;
 657         int ilen;
 658         int codelen;
 659         int extra;
 660
 661         db       = (struct bsd_db *) state;
 662         max_ent  = db->max_ent;
 663         accm     = 0;
 664         bitno    = 32;          /* 1st valid bit in accm */
 665         n_bits   = db->n_bits;
 666         tgtbitno = 32 - n_bits; /* bitno when we have a code */
 667
 668         printk(KERN_DEBUG "bsd_decompress called\n");
 669
 670         if (!skb_in || !skb_out) {
 671                 printk(KERN_ERR "bsd_decompress called with NULL parameter\n");
 672                 return DECOMP_ERROR;
 673         }
 674
 675         /*
 676          * Get the sequence number.
 677          */
 678         if ((p = skb_pull(skb_in, 2)) == NULL) {
 679                 return DECOMP_ERROR;
 680         }
 681         p -= 2;
 682         seq = (p[0] << 8) + p[1];
 683         ilen = skb_in->len;
 684         ibuf = skb_in->data;
 685
 686         /*
 687          * Check the sequence number and give up if it differs from
 688          * the value we're expecting.
 689          */
 690         if (seq != db->seqno) {
 691                 if (db->debug) {
 692                         printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n",
 693                                db->unit, seq, db->seqno - 1);
 694                 }
 695                 return DECOMP_ERROR;
 696         }
 697
 698         ++db->seqno;
 699         db->bytes_out += ilen;
 700
 701         if (skb_tailroom(skb_out) > 0)
 702                 skb_put_u8(skb_out, 0);
 703         else
 704                 return DECOMP_ERR_NOMEM;
 705
 706         oldcode = CLEAR;
 707
 708         /*
 709          * Keep the checkpoint correctly so that incompressible packets
 710          * clear the dictionary at the proper times.
 711          */
 712
 713         for (;;) {
 714                 if (ilen-- <= 0) {
 715                         db->in_count += (skb_out->len - 1); /* don't count the header */
 716                         break;
 717                 }
 718
 719                 /*
 720                  * Accumulate bytes until we have a complete code.
 721                  * Then get the next code, relying on the 32-bit,
 722                  * unsigned accm to mask the result.
 723                  */
 724
 725                 bitno -= 8;
 726                 accm  |= *ibuf++ << bitno;
 727                 if (tgtbitno < bitno)
 728                         continue;
 729
 730                 incode = accm >> tgtbitno;
 731                 accm <<= n_bits;
 732                 bitno += n_bits;
 733
 734                 /*
 735                  * The dictionary must only be cleared at the end of a packet.
 736                  */
 737
 738                 if (incode == CLEAR) {
 739                         if (ilen > 0) {
 740                                 if (db->debug)
 741                                         printk(KERN_DEBUG "bsd_decomp%d: bad CLEAR\n", db->unit);
 742                                 return DECOMP_FATALERROR;       /* probably a bug */
 743                         }
 744                         bsd_clear(db);
 745                         break;
 746                 }
 747
 748                 if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
 749                     || (incode > max_ent && oldcode == CLEAR)) {
 750                         if (db->debug) {
 751                                 printk(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
 752                                        db->unit, incode, oldcode);
 753                                 printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n",
 754                                        max_ent, skb_out->len, db->seqno);
 755                         }
 756                         return DECOMP_FATALERROR;       /* probably a bug */
 757                 }
 758
 759                 /* Special case for KwKwK string. */
 760                 if (incode > max_ent) {
 761                         finchar = oldcode;
 762                         extra   = 1;
 763                 } else {
 764                         finchar = incode;
 765                         extra   = 0;
 766                 }
 767
 768                 codelen = *(lens_ptr(db, finchar));
 769                 if (skb_tailroom(skb_out) < codelen + extra) {
 770                         if (db->debug) {
 771                                 printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit);
 772 #ifdef DEBUG
 773                                 printk(KERN_DEBUG "  len=%d, finchar=0x%x, codelen=%d,skblen=%d\n",
 774                                        ilen, finchar, codelen, skb_out->len);
 775 #endif
 776                         }
 777                         return DECOMP_FATALERROR;
 778                 }
 779
 780                 /*
 781                  * Decode this code and install it in the decompressed buffer.
 782                  */
 783
 784                 p = skb_put(skb_out, codelen);
 785                 p += codelen;
 786                 while (finchar > LAST) {
 787                         struct bsd_dict *dictp2 = dict_ptr(db, finchar);
 788
 789                         dictp = dict_ptr(db, dictp2->cptr);
 790
 791 #ifdef DEBUG
 792                         if (--codelen <= 0 || dictp->codem1 != finchar - 1) {
 793                                 if (codelen <= 0) {
 794                                         printk(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit);
 795                                         printk(KERN_ERR "0x%x at 0x%x by 0x%x, max_ent=0x%x\n", incode, finchar, dictp2->cptr, max_ent);
 796                                 } else {
 797                                         if (dictp->codem1 != finchar - 1) {
 798                                                 printk(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", db->unit, incode, finchar);
 799                                                 printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1);
 800                                         }
 801                                 }
 802                                 return DECOMP_FATALERROR;
 803                         }
 804 #endif
 805
 806                         {
 807                                 u32 fcode = dictp->fcode;
 808                                 *--p    = (fcode >> 16) & 0xff;
 809                                 finchar = fcode & 0xffff;
 810                         }
 811                 }
 812                 *--p = finchar;
 813
 814 #ifdef DEBUG
 815                 if (--codelen != 0)
 816                         printk(KERN_ERR "bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", db->unit, codelen, incode, max_ent);
 817 #endif
 818
 819                 if (extra)              /* the KwKwK case again */
 820                         skb_put_u8(skb_out, finchar);
 821
 822                 /*
 823                  * If not first code in a packet, and
 824                  * if not out of code space, then allocate a new code.
 825                  *
 826                  * Keep the hash table correct so it can be used
 827                  * with uncompressed packets.
 828                  */
 829                 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
 830                         struct bsd_dict *dictp2, *dictp3;
 831                         u16 *lens1, *lens2;
 832                         unsigned long fcode;
 833                         int hval, disp, indx;
 834
 835                         fcode = BSD_KEY(oldcode, finchar);
 836                         hval  = BSD_HASH(oldcode, finchar, db->hshift);
 837                         dictp = dict_ptr(db, hval);
 838
 839                         /* look for a free hash table entry */
 840                         if (dictp->codem1 < max_ent) {
 841                                 disp = (hval == 0) ? 1 : hval;
 842                                 do {
 843                                         hval += disp;
 844                                         if (hval >= db->hsize)
 845                                                 hval -= db->hsize;
 846                                         dictp = dict_ptr(db, hval);
 847                                 } while (dictp->codem1 < max_ent);
 848                         }
 849
 850                         /*
 851                          * Invalidate previous hash table entry
 852                          * assigned this code, and then take it over
 853                          */
 854
 855                         dictp2 = dict_ptr(db, max_ent + 1);
 856                         indx   = dictp2->cptr;
 857                         dictp3 = dict_ptr(db, indx);
 858
 859                         if (dictp3->codem1 == max_ent)
 860                                 dictp3->codem1 = BADCODEM1;
 861
 862                         dictp2->cptr   = hval;
 863                         dictp->codem1  = max_ent;
 864                         dictp->fcode = fcode;
 865                         db->max_ent    = ++max_ent;
 866
 867                         /* Update the length of this string. */
 868                         lens1  = lens_ptr(db, max_ent);
 869                         lens2  = lens_ptr(db, oldcode);
 870                         *lens1 = *lens2 + 1;
 871
 872                         /* Expand code size if needed. */
 873                         if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
 874                                 db->n_bits = ++n_bits;
 875                                 tgtbitno   = 32-n_bits;
 876                         }
 877                 }
 878                 oldcode = incode;
 879         }
 880
 881         ++db->comp_count;
 882         ++db->uncomp_count;
 883         db->comp_bytes   += skb_in->len - BSD_OVHD;
 884         db->uncomp_bytes += skb_out->len;
 885
 886         if (bsd_check(db)) {
 887                 if (db->debug)
 888                         printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n",
 889                                db->unit, db->seqno - 1);
 890         }
 891         return skb_out->len;
 892 }
 893
 894 /*************************************************************
 895  * Table of addresses for the BSD compression module
 896  *************************************************************/
 897
 898 static struct isdn_ppp_compressor ippp_bsd_compress = {
 899         .owner          = THIS_MODULE,
 900         .num            = CI_BSD_COMPRESS,
 901         .alloc          = bsd_alloc,
 902         .free           = bsd_free,
 903         .init           = bsd_init,
 904         .reset          = bsd_reset,
 905         .compress       = bsd_compress,
 906         .decompress     = bsd_decompress,
 907         .incomp         = bsd_incomp,
 908         .stat           = bsd_stats,
 909 };
 910
 911 /*************************************************************
 912  * Module support routines
 913  *************************************************************/
 914
 915 static int __init isdn_bsdcomp_init(void)
 916 {
 917         int answer = isdn_ppp_register_compressor(&ippp_bsd_compress);
 918         if (answer == 0)
 919                 printk(KERN_INFO "PPP BSD Compression module registered\n");
 920         return answer;
 921 }
 922
 923 static void __exit isdn_bsdcomp_exit(void)
 924 {
 925         isdn_ppp_unregister_compressor(&ippp_bsd_compress);
 926 }
 927
 928 module_init(isdn_bsdcomp_init);
 929 module_exit(isdn_bsdcomp_exit);