linux/drivers/isdn/i4l/isdn_bsdcomp.c
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   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
  96MODULE_DESCRIPTION("ISDN4Linux: BSD Compression for PPP over ISDN");
  97MODULE_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
 110struct bsd_dict {
 111        u32 fcode;
 112        u16 codem1;             /* output of hash table -1 */
 113        u16 cptr;               /* map code to hash table entry */
 114};
 115
 116struct 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
 175static 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 */
 200static 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
 246static 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 */
 263static 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 */
 277static 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 */
 305static 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 = 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 = vmalloc((maxmaxcode + 1) * sizeof(db->lens[0]));
 358                if (!db->lens) {
 359                        bsd_free (db);
 360                        return (NULL);
 361                }
 362        }
 363
 364        /*
 365         * Initialize the data information for the compression code
 366         */
 367        db->totlen     = sizeof (struct bsd_db) + (sizeof (struct bsd_dict) * hsize);
 368        db->hsize      = hsize;
 369        db->hshift     = hshift;
 370        db->maxmaxcode = maxmaxcode;
 371        db->maxbits    = bits;
 372
 373        return (void *) db;
 374}
 375
 376/*
 377 * Initialize the database.
 378 */
 379static int bsd_init (void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
 380{
 381        struct bsd_db *db = state;
 382        int indx;
 383        int decomp;
 384
 385        if(!state || !data) {
 386                printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n",unit,(long)state,(long)data);
 387                return 0;
 388        }
 389
 390        decomp = db->xmit ? 0 : 1;
 391    
 392        if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
 393                || (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
 394                || (BSD_NBITS(data->options[0]) != db->maxbits)
 395                || (decomp && db->lens == NULL)) {
 396                printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n",data->optlen,data->num,data->options[0],decomp,(unsigned long)db->lens);
 397                return 0;
 398        }
 399
 400        if (decomp)
 401                for(indx=LAST;indx>=0;indx--)
 402                        db->lens[indx] = 1;
 403
 404        indx = db->hsize;
 405        while (indx-- != 0) {
 406                db->dict[indx].codem1 = BADCODEM1;
 407                db->dict[indx].cptr   = 0;
 408        }
 409
 410        db->unit = unit;
 411        db->mru  = 0;
 412
 413        db->debug = 1;
 414    
 415        bsd_reset(db,0,0,NULL,0,NULL);
 416    
 417        return 1;
 418}
 419
 420/*
 421 * Obtain pointers to the various structures in the compression tables
 422 */
 423
 424#define dict_ptrx(p,idx) &(p->dict[idx])
 425#define lens_ptrx(p,idx) &(p->lens[idx])
 426
 427#ifdef DEBUG
 428static unsigned short *lens_ptr(struct bsd_db *db, int idx)
 429{
 430        if ((unsigned int) idx > (unsigned int) db->maxmaxcode) {
 431                printk (KERN_DEBUG "<9>ppp: lens_ptr(%d) > max\n", idx);
 432                idx = 0;
 433        }
 434        return lens_ptrx (db, idx);
 435}
 436
 437static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
 438{
 439        if ((unsigned int) idx >= (unsigned int) db->hsize) {
 440                printk (KERN_DEBUG "<9>ppp: dict_ptr(%d) > max\n", idx);
 441                idx = 0;
 442        }
 443        return dict_ptrx (db, idx);
 444}
 445
 446#else
 447#define lens_ptr(db,idx) lens_ptrx(db,idx)
 448#define dict_ptr(db,idx) dict_ptrx(db,idx)
 449#endif
 450
 451/*
 452 * compress a packet
 453 */
 454static int bsd_compress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,int proto)
 455{
 456        struct bsd_db *db;
 457        int hshift;
 458        unsigned int max_ent;
 459        unsigned int n_bits;
 460        unsigned int bitno;
 461        unsigned long accm;
 462        int ent;
 463        unsigned long fcode;
 464        struct bsd_dict *dictp;
 465        unsigned char c;
 466        int hval,disp,ilen,mxcode;
 467        unsigned char *rptr = skb_in->data;
 468        int isize = skb_in->len;
 469
 470#define OUTPUT(ent)                     \
 471  {                                     \
 472    bitno -= n_bits;                    \
 473    accm |= ((ent) << bitno);           \
 474    do  {                               \
 475        if(skb_out && skb_tailroom(skb_out) > 0)        \
 476                *(skb_put(skb_out,1)) = (unsigned char) (accm>>24); \
 477        accm <<= 8;                     \
 478        bitno += 8;                     \
 479    } while (bitno <= 24);              \
 480  }
 481
 482        /*
 483         * If the protocol is not in the range we're interested in,
 484         * just return without compressing the packet.  If it is,
 485         * the protocol becomes the first byte to compress.
 486         */
 487        printk(KERN_DEBUG "bsd_compress called with %x\n",proto);
 488        
 489        ent = proto;
 490        if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1) )
 491                return 0;
 492
 493        db      = (struct bsd_db *) state;
 494        hshift  = db->hshift;
 495        max_ent = db->max_ent;
 496        n_bits  = db->n_bits;
 497        bitno   = 32;
 498        accm    = 0;
 499        mxcode  = MAXCODE (n_bits);
 500        
 501        /* This is the PPP header information */
 502        if(skb_out && skb_tailroom(skb_out) >= 2) {
 503                char *v = skb_put(skb_out,2);
 504                /* we only push our own data on the header,
 505                  AC,PC and protos is pushed by caller  */
 506                v[0] = db->seqno >> 8;
 507                v[1] = db->seqno;
 508        }
 509
 510        ilen   = ++isize; /* This is off by one, but that is what is in draft! */
 511
 512        while (--ilen > 0) {
 513                c     = *rptr++;
 514                fcode = BSD_KEY  (ent, c);
 515                hval  = BSD_HASH (ent, c, hshift);
 516                dictp = dict_ptr (db, hval);
 517        
 518                /* Validate and then check the entry. */
 519                if (dictp->codem1 >= max_ent)
 520                        goto nomatch;
 521
 522                if (dictp->fcode == fcode) {
 523                        ent = dictp->codem1 + 1;
 524                        continue;       /* found (prefix,suffix) */
 525                }
 526        
 527                /* continue probing until a match or invalid entry */
 528                disp = (hval == 0) ? 1 : hval;
 529
 530                do {
 531                        hval += disp;
 532                        if (hval >= db->hsize)
 533                                hval -= db->hsize;
 534                        dictp = dict_ptr (db, hval);
 535                        if (dictp->codem1 >= max_ent)
 536                                goto nomatch;
 537                } while (dictp->fcode != fcode);
 538
 539                ent = dictp->codem1 + 1;        /* finally found (prefix,suffix) */
 540                continue;
 541        
 542nomatch:
 543                OUTPUT(ent);            /* output the prefix */
 544        
 545                /* code -> hashtable */
 546                if (max_ent < db->maxmaxcode) {
 547                        struct bsd_dict *dictp2;
 548                        struct bsd_dict *dictp3;
 549                        int indx;
 550
 551                        /* expand code size if needed */
 552                        if (max_ent >= mxcode) {
 553                                db->n_bits = ++n_bits;
 554                                mxcode = MAXCODE (n_bits);
 555                        }
 556            
 557                        /* 
 558                         * Invalidate old hash table entry using
 559                         * this code, and then take it over.
 560                         */
 561                        dictp2 = dict_ptr (db, max_ent + 1);
 562                        indx   = dictp2->cptr;
 563                        dictp3 = dict_ptr (db, indx);
 564
 565                        if (dictp3->codem1 == max_ent)
 566                                dictp3->codem1 = BADCODEM1;
 567
 568                        dictp2->cptr   = hval;
 569                        dictp->codem1  = max_ent;
 570                        dictp->fcode = fcode;
 571                        db->max_ent    = ++max_ent;
 572
 573                        if (db->lens) {
 574                                unsigned short *len1 = lens_ptr (db, max_ent);
 575                                unsigned short *len2 = lens_ptr (db, ent);
 576                                *len1 = *len2 + 1;
 577                        }
 578                }
 579                ent = c;
 580        }
 581    
 582        OUTPUT(ent);            /* output the last code */
 583
 584        if(skb_out)
 585                db->bytes_out    += skb_out->len; /* Do not count bytes from here */
 586        db->uncomp_bytes += isize;
 587        db->in_count     += isize;
 588        ++db->uncomp_count;
 589        ++db->seqno;
 590
 591        if (bitno < 32)
 592                ++db->bytes_out; /* must be set before calling bsd_check */
 593
 594        /*
 595         * Generate the clear command if needed
 596         */
 597
 598        if (bsd_check(db))
 599                OUTPUT (CLEAR);
 600
 601        /*
 602         * Pad dribble bits of last code with ones.
 603         * Do not emit a completely useless byte of ones.
 604         */
 605        if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0) 
 606                *(skb_put(skb_out,1)) = (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 && 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 */
 634static 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 */
 642static 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(skb_out,1)) = 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(skb_out,1)) = 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
 898static 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
 915static 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
 923static void __exit isdn_bsdcomp_exit(void)
 924{
 925        isdn_ppp_unregister_compressor (&ippp_bsd_compress);
 926}
 927
 928module_init(isdn_bsdcomp_init);
 929module_exit(isdn_bsdcomp_exit);
 930