Root/drivers/net/bsd_comp.c

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

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