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