blob: fb4098ed469eeb8a2be64d6754cddda98e640324 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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)
Jesper Juhlf91012102005-09-10 00:26:54 -0700326{
327 struct bsd_db *db = state;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328
Jesper Juhlf91012102005-09-10 00:26:54 -0700329 if (!db)
330 return;
331
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332/*
333 * Release the dictionary
334 */
Jesper Juhlf91012102005-09-10 00:26:54 -0700335 vfree(db->dict);
336 db->dict = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337/*
338 * Release the string buffer
339 */
Jesper Juhlf91012102005-09-10 00:26:54 -0700340 vfree(db->lens);
341 db->lens = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342/*
343 * Finally release the structure itself.
344 */
Jesper Juhlf91012102005-09-10 00:26:54 -0700345 kfree(db);
346}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347
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 = (struct bsd_db *) kmalloc (sizeof (struct bsd_db),
399 GFP_KERNEL);
400 if (!db)
401 {
402 return NULL;
403 }
404
405 memset (db, 0, sizeof(struct bsd_db));
406/*
407 * Allocate space for the dictionary. This may be more than one page in
408 * length.
409 */
410 db->dict = (struct bsd_dict *) vmalloc (hsize *
411 sizeof (struct bsd_dict));
412 if (!db->dict)
413 {
414 bsd_free (db);
415 return NULL;
416 }
417
418/*
419 * If this is the compression buffer then there is no length data.
420 */
421 if (!decomp)
422 {
423 db->lens = NULL;
424 }
425/*
426 * For decompression, the length information is needed as well.
427 */
428 else
429 {
430 db->lens = (unsigned short *) vmalloc ((maxmaxcode + 1) *
431 sizeof (db->lens[0]));
432 if (!db->lens)
433 {
434 bsd_free (db);
435 return (NULL);
436 }
437 }
438/*
439 * Initialize the data information for the compression code
440 */
441 db->totlen = sizeof (struct bsd_db) +
442 (sizeof (struct bsd_dict) * hsize);
443
444 db->hsize = hsize;
445 db->hshift = hshift;
446 db->maxmaxcode = maxmaxcode;
447 db->maxbits = bits;
448
449 return (void *) db;
450 }
451
452static void *bsd_comp_alloc (unsigned char *options, int opt_len)
453 {
454 return bsd_alloc (options, opt_len, 0);
455 }
456
457static void *bsd_decomp_alloc (unsigned char *options, int opt_len)
458 {
459 return bsd_alloc (options, opt_len, 1);
460 }
461
462/*
463 * Initialize the database.
464 */
465
466static int bsd_init (void *state, unsigned char *options,
467 int opt_len, int unit, int debug, int decomp)
468 {
469 struct bsd_db *db = state;
470 int indx;
471
472 if ((opt_len != 3) || (options[0] != CI_BSD_COMPRESS) || (options[1] != 3)
473 || (BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
474 || (BSD_NBITS(options[2]) != db->maxbits)
475 || (decomp && db->lens == NULL))
476 {
477 return 0;
478 }
479
480 if (decomp)
481 {
482 indx = LAST;
483 do
484 {
485 db->lens[indx] = 1;
486 }
487 while (indx-- > 0);
488 }
489
490 indx = db->hsize;
491 while (indx-- != 0)
492 {
493 db->dict[indx].codem1 = BADCODEM1;
494 db->dict[indx].cptr = 0;
495 }
496
497 db->unit = unit;
498 db->mru = 0;
499#ifndef DEBUG
500 if (debug)
501#endif
502 db->debug = 1;
503
504 bsd_reset(db);
505
506 return 1;
507 }
508
509static int bsd_comp_init (void *state, unsigned char *options,
510 int opt_len, int unit, int opthdr, int debug)
511 {
512 return bsd_init (state, options, opt_len, unit, debug, 0);
513 }
514
515static int bsd_decomp_init (void *state, unsigned char *options,
516 int opt_len, int unit, int opthdr, int mru,
517 int debug)
518 {
519 return bsd_init (state, options, opt_len, unit, debug, 1);
520 }
521
522/*
523 * Obtain pointers to the various structures in the compression tables
524 */
525
526#define dict_ptrx(p,idx) &(p->dict[idx])
527#define lens_ptrx(p,idx) &(p->lens[idx])
528
529#ifdef DEBUG
530static unsigned short *lens_ptr(struct bsd_db *db, int idx)
531 {
532 if ((unsigned int) idx > (unsigned int) db->maxmaxcode)
533 {
534 printk ("<9>ppp: lens_ptr(%d) > max\n", idx);
535 idx = 0;
536 }
537 return lens_ptrx (db, idx);
538 }
539
540static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
541 {
542 if ((unsigned int) idx >= (unsigned int) db->hsize)
543 {
544 printk ("<9>ppp: dict_ptr(%d) > max\n", idx);
545 idx = 0;
546 }
547 return dict_ptrx (db, idx);
548 }
549
550#else
551#define lens_ptr(db,idx) lens_ptrx(db,idx)
552#define dict_ptr(db,idx) dict_ptrx(db,idx)
553#endif
554
555/*
556 * compress a packet
557 *
558 * The result of this function is the size of the compressed
559 * packet. A zero is returned if the packet was not compressed
560 * for some reason, such as the size being larger than uncompressed.
561 *
562 * One change from the BSD compress command is that when the
563 * code size expands, we do not output a bunch of padding.
564 */
565
566static int bsd_compress (void *state, unsigned char *rptr, unsigned char *obuf,
567 int isize, int osize)
568 {
569 struct bsd_db *db;
570 int hshift;
571 unsigned int max_ent;
572 unsigned int n_bits;
573 unsigned int bitno;
574 unsigned long accm;
575 int ent;
576 unsigned long fcode;
577 struct bsd_dict *dictp;
578 unsigned char c;
579 int hval;
580 int disp;
581 int ilen;
582 int mxcode;
583 unsigned char *wptr;
584 int olen;
585
586#define PUTBYTE(v) \
587 { \
588 ++olen; \
589 if (wptr) \
590 { \
591 *wptr++ = (unsigned char) (v); \
592 if (olen >= osize) \
593 { \
594 wptr = NULL; \
595 } \
596 } \
597 }
598
599#define OUTPUT(ent) \
600 { \
601 bitno -= n_bits; \
602 accm |= ((ent) << bitno); \
603 do \
604 { \
605 PUTBYTE(accm >> 24); \
606 accm <<= 8; \
607 bitno += 8; \
608 } \
609 while (bitno <= 24); \
610 }
611
612 /*
613 * If the protocol is not in the range we're interested in,
614 * just return without compressing the packet. If it is,
615 * the protocol becomes the first byte to compress.
616 */
617
618 ent = PPP_PROTOCOL(rptr);
619 if (ent < 0x21 || ent > 0xf9)
620 {
621 return 0;
622 }
623
624 db = (struct bsd_db *) state;
625 hshift = db->hshift;
626 max_ent = db->max_ent;
627 n_bits = db->n_bits;
628 bitno = 32;
629 accm = 0;
630 mxcode = MAXCODE (n_bits);
631
632 /* Initialize the output pointers */
633 wptr = obuf;
634 olen = PPP_HDRLEN + BSD_OVHD;
635
636 if (osize > isize)
637 {
638 osize = isize;
639 }
640
641 /* This is the PPP header information */
642 if (wptr)
643 {
644 *wptr++ = PPP_ADDRESS(rptr);
645 *wptr++ = PPP_CONTROL(rptr);
646 *wptr++ = 0;
647 *wptr++ = PPP_COMP;
648 *wptr++ = db->seqno >> 8;
649 *wptr++ = db->seqno;
650 }
651
652 /* Skip the input header */
653 rptr += PPP_HDRLEN;
654 isize -= PPP_HDRLEN;
655 ilen = ++isize; /* Low byte of protocol is counted as input */
656
657 while (--ilen > 0)
658 {
659 c = *rptr++;
660 fcode = BSD_KEY (ent, c);
661 hval = BSD_HASH (ent, c, hshift);
662 dictp = dict_ptr (db, hval);
663
664 /* Validate and then check the entry. */
665 if (dictp->codem1 >= max_ent)
666 {
667 goto nomatch;
668 }
669
670 if (dictp->f.fcode == fcode)
671 {
672 ent = dictp->codem1 + 1;
673 continue; /* found (prefix,suffix) */
674 }
675
676 /* continue probing until a match or invalid entry */
677 disp = (hval == 0) ? 1 : hval;
678
679 do
680 {
681 hval += disp;
682 if (hval >= db->hsize)
683 {
684 hval -= db->hsize;
685 }
686 dictp = dict_ptr (db, hval);
687 if (dictp->codem1 >= max_ent)
688 {
689 goto nomatch;
690 }
691 }
692 while (dictp->f.fcode != fcode);
693
694 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
695 continue;
696
697nomatch:
698 OUTPUT(ent); /* output the prefix */
699
700 /* code -> hashtable */
701 if (max_ent < db->maxmaxcode)
702 {
703 struct bsd_dict *dictp2;
704 struct bsd_dict *dictp3;
705 int indx;
706
707 /* expand code size if needed */
708 if (max_ent >= mxcode)
709 {
710 db->n_bits = ++n_bits;
711 mxcode = MAXCODE (n_bits);
712 }
713
714 /* Invalidate old hash table entry using
715 * this code, and then take it over.
716 */
717
718 dictp2 = dict_ptr (db, max_ent + 1);
719 indx = dictp2->cptr;
720 dictp3 = dict_ptr (db, indx);
721
722 if (dictp3->codem1 == max_ent)
723 {
724 dictp3->codem1 = BADCODEM1;
725 }
726
727 dictp2->cptr = hval;
728 dictp->codem1 = max_ent;
729 dictp->f.fcode = fcode;
730 db->max_ent = ++max_ent;
731
732 if (db->lens)
733 {
734 unsigned short *len1 = lens_ptr (db, max_ent);
735 unsigned short *len2 = lens_ptr (db, ent);
736 *len1 = *len2 + 1;
737 }
738 }
739 ent = c;
740 }
741
742 OUTPUT(ent); /* output the last code */
743
744 db->bytes_out += olen - PPP_HDRLEN - BSD_OVHD;
745 db->uncomp_bytes += isize;
746 db->in_count += isize;
747 ++db->uncomp_count;
748 ++db->seqno;
749
750 if (bitno < 32)
751 {
752 ++db->bytes_out; /* must be set before calling bsd_check */
753 }
754
755 /*
756 * Generate the clear command if needed
757 */
758
759 if (bsd_check(db))
760 {
761 OUTPUT (CLEAR);
762 }
763
764 /*
765 * Pad dribble bits of last code with ones.
766 * Do not emit a completely useless byte of ones.
767 */
768
769 if (bitno != 32)
770 {
771 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
772 }
773
774 /*
775 * Increase code size if we would have without the packet
776 * boundary because the decompressor will do so.
777 */
778
779 if (max_ent >= mxcode && max_ent < db->maxmaxcode)
780 {
781 db->n_bits++;
782 }
783
784 /* If output length is too large then this is an incomplete frame. */
785 if (wptr == NULL)
786 {
787 ++db->incomp_count;
788 db->incomp_bytes += isize;
789 olen = 0;
790 }
791 else /* Count the number of compressed frames */
792 {
793 ++db->comp_count;
794 db->comp_bytes += olen;
795 }
796
797 /* Return the resulting output length */
798 return olen;
799#undef OUTPUT
800#undef PUTBYTE
801 }
802
803/*
804 * Update the "BSD Compress" dictionary on the receiver for
805 * incompressible data by pretending to compress the incoming data.
806 */
807
808static void bsd_incomp (void *state, unsigned char *ibuf, int icnt)
809 {
810 (void) bsd_compress (state, ibuf, (char *) 0, icnt, 0);
811 }
812
813/*
814 * Decompress "BSD Compress".
815 *
816 * Because of patent problems, we return DECOMP_ERROR for errors
817 * found by inspecting the input data and for system problems, but
818 * DECOMP_FATALERROR for any errors which could possibly be said to
819 * be being detected "after" decompression. For DECOMP_ERROR,
820 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
821 * infringing a patent of Motorola's if we do, so we take CCP down
822 * instead.
823 *
824 * Given that the frame has the correct sequence number and a good FCS,
825 * errors such as invalid codes in the input most likely indicate a
826 * bug, so we return DECOMP_FATALERROR for them in order to turn off
827 * compression, even though they are detected by inspecting the input.
828 */
829
830static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
831 unsigned char *obuf, int osize)
832 {
833 struct bsd_db *db;
834 unsigned int max_ent;
835 unsigned long accm;
836 unsigned int bitno; /* 1st valid bit in accm */
837 unsigned int n_bits;
838 unsigned int tgtbitno; /* bitno when we have a code */
839 struct bsd_dict *dictp;
840 int explen;
841 int seq;
842 unsigned int incode;
843 unsigned int oldcode;
844 unsigned int finchar;
845 unsigned char *p;
846 unsigned char *wptr;
847 int adrs;
848 int ctrl;
849 int ilen;
850 int codelen;
851 int extra;
852
853 db = (struct bsd_db *) state;
854 max_ent = db->max_ent;
855 accm = 0;
856 bitno = 32; /* 1st valid bit in accm */
857 n_bits = db->n_bits;
858 tgtbitno = 32 - n_bits; /* bitno when we have a code */
859
860 /*
861 * Save the address/control from the PPP header
862 * and then get the sequence number.
863 */
864
865 adrs = PPP_ADDRESS (ibuf);
866 ctrl = PPP_CONTROL (ibuf);
867
868 seq = (ibuf[4] << 8) + ibuf[5];
869
870 ibuf += (PPP_HDRLEN + 2);
871 ilen = isize - (PPP_HDRLEN + 2);
872
873 /*
874 * Check the sequence number and give up if it differs from
875 * the value we're expecting.
876 */
877
878 if (seq != db->seqno)
879 {
880 if (db->debug)
881 {
882 printk("bsd_decomp%d: bad sequence # %d, expected %d\n",
883 db->unit, seq, db->seqno - 1);
884 }
885 return DECOMP_ERROR;
886 }
887
888 ++db->seqno;
889 db->bytes_out += ilen;
890
891 /*
892 * Fill in the ppp header, but not the last byte of the protocol
893 * (that comes from the decompressed data).
894 */
895
896 wptr = obuf;
897 *wptr++ = adrs;
898 *wptr++ = ctrl;
899 *wptr++ = 0;
900
901 oldcode = CLEAR;
902 explen = 3;
903
904 /*
905 * Keep the checkpoint correctly so that incompressible packets
906 * clear the dictionary at the proper times.
907 */
908
909 for (;;)
910 {
911 if (ilen-- <= 0)
912 {
913 db->in_count += (explen - 3); /* don't count the header */
914 break;
915 }
916
917 /*
918 * Accumulate bytes until we have a complete code.
919 * Then get the next code, relying on the 32-bit,
920 * unsigned accm to mask the result.
921 */
922
923 bitno -= 8;
924 accm |= *ibuf++ << bitno;
925 if (tgtbitno < bitno)
926 {
927 continue;
928 }
929
930 incode = accm >> tgtbitno;
931 accm <<= n_bits;
932 bitno += n_bits;
933
934 /*
935 * The dictionary must only be cleared at the end of a packet.
936 */
937
938 if (incode == CLEAR)
939 {
940 if (ilen > 0)
941 {
942 if (db->debug)
943 {
944 printk("bsd_decomp%d: bad CLEAR\n", db->unit);
945 }
946 return DECOMP_FATALERROR; /* probably a bug */
947 }
948
949 bsd_clear(db);
950 break;
951 }
952
953 if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
954 || (incode > max_ent && oldcode == CLEAR))
955 {
956 if (db->debug)
957 {
958 printk("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
959 db->unit, incode, oldcode);
960 printk("max_ent=0x%x explen=%d seqno=%d\n",
961 max_ent, explen, db->seqno);
962 }
963 return DECOMP_FATALERROR; /* probably a bug */
964 }
965
966 /* Special case for KwKwK string. */
967 if (incode > max_ent)
968 {
969 finchar = oldcode;
970 extra = 1;
971 }
972 else
973 {
974 finchar = incode;
975 extra = 0;
976 }
977
978 codelen = *(lens_ptr (db, finchar));
979 explen += codelen + extra;
980 if (explen > osize)
981 {
982 if (db->debug)
983 {
984 printk("bsd_decomp%d: ran out of mru\n", db->unit);
985#ifdef DEBUG
986 printk(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
987 ilen, finchar, codelen, explen);
988#endif
989 }
990 return DECOMP_FATALERROR;
991 }
992
993 /*
994 * Decode this code and install it in the decompressed buffer.
995 */
996
997 wptr += codelen;
998 p = wptr;
999 while (finchar > LAST)
1000 {
1001 struct bsd_dict *dictp2 = dict_ptr (db, finchar);
1002
1003 dictp = dict_ptr (db, dictp2->cptr);
1004#ifdef DEBUG
1005 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1006 {
1007 if (codelen <= 0)
1008 {
1009 printk("bsd_decomp%d: fell off end of chain ", db->unit);
1010 printk("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1011 incode, finchar, dictp2->cptr, max_ent);
1012 }
1013 else
1014 {
1015 if (dictp->codem1 != finchar-1)
1016 {
1017 printk("bsd_decomp%d: bad code chain 0x%x "
1018 "finchar=0x%x ",
1019 db->unit, incode, finchar);
1020
1021 printk("oldcode=0x%x cptr=0x%x codem1=0x%x\n",
1022 oldcode, dictp2->cptr, dictp->codem1);
1023 }
1024 }
1025 return DECOMP_FATALERROR;
1026 }
1027#endif
1028 *--p = dictp->f.hs.suffix;
1029 finchar = dictp->f.hs.prefix;
1030 }
1031 *--p = finchar;
1032
1033#ifdef DEBUG
1034 if (--codelen != 0)
1035 {
1036 printk("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1037 db->unit, codelen, incode, max_ent);
1038 }
1039#endif
1040
1041 if (extra) /* the KwKwK case again */
1042 {
1043 *wptr++ = finchar;
1044 }
1045
1046 /*
1047 * If not first code in a packet, and
1048 * if not out of code space, then allocate a new code.
1049 *
1050 * Keep the hash table correct so it can be used
1051 * with uncompressed packets.
1052 */
1053
1054 if (oldcode != CLEAR && max_ent < db->maxmaxcode)
1055 {
1056 struct bsd_dict *dictp2, *dictp3;
1057 unsigned short *lens1, *lens2;
1058 unsigned long fcode;
1059 int hval, disp, indx;
1060
1061 fcode = BSD_KEY(oldcode,finchar);
1062 hval = BSD_HASH(oldcode,finchar,db->hshift);
1063 dictp = dict_ptr (db, hval);
1064
1065 /* look for a free hash table entry */
1066 if (dictp->codem1 < max_ent)
1067 {
1068 disp = (hval == 0) ? 1 : hval;
1069 do
1070 {
1071 hval += disp;
1072 if (hval >= db->hsize)
1073 {
1074 hval -= db->hsize;
1075 }
1076 dictp = dict_ptr (db, hval);
1077 }
1078 while (dictp->codem1 < max_ent);
1079 }
1080
1081 /*
1082 * Invalidate previous hash table entry
1083 * assigned this code, and then take it over
1084 */
1085
1086 dictp2 = dict_ptr (db, max_ent + 1);
1087 indx = dictp2->cptr;
1088 dictp3 = dict_ptr (db, indx);
1089
1090 if (dictp3->codem1 == max_ent)
1091 {
1092 dictp3->codem1 = BADCODEM1;
1093 }
1094
1095 dictp2->cptr = hval;
1096 dictp->codem1 = max_ent;
1097 dictp->f.fcode = fcode;
1098 db->max_ent = ++max_ent;
1099
1100 /* Update the length of this string. */
1101 lens1 = lens_ptr (db, max_ent);
1102 lens2 = lens_ptr (db, oldcode);
1103 *lens1 = *lens2 + 1;
1104
1105 /* Expand code size if needed. */
1106 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
1107 {
1108 db->n_bits = ++n_bits;
1109 tgtbitno = 32-n_bits;
1110 }
1111 }
1112 oldcode = incode;
1113 }
1114
1115 ++db->comp_count;
1116 ++db->uncomp_count;
1117 db->comp_bytes += isize - BSD_OVHD - PPP_HDRLEN;
1118 db->uncomp_bytes += explen;
1119
1120 if (bsd_check(db))
1121 {
1122 if (db->debug)
1123 {
1124 printk("bsd_decomp%d: peer should have cleared dictionary on %d\n",
1125 db->unit, db->seqno - 1);
1126 }
1127 }
1128 return explen;
1129 }
1130
1131/*************************************************************
1132 * Table of addresses for the BSD compression module
1133 *************************************************************/
1134
1135static struct compressor ppp_bsd_compress = {
1136 .compress_proto = CI_BSD_COMPRESS,
1137 .comp_alloc = bsd_comp_alloc,
1138 .comp_free = bsd_free,
1139 .comp_init = bsd_comp_init,
1140 .comp_reset = bsd_reset,
1141 .compress = bsd_compress,
1142 .comp_stat = bsd_comp_stats,
1143 .decomp_alloc = bsd_decomp_alloc,
1144 .decomp_free = bsd_free,
1145 .decomp_init = bsd_decomp_init,
1146 .decomp_reset = bsd_reset,
1147 .decompress = bsd_decompress,
1148 .incomp = bsd_incomp,
1149 .decomp_stat = bsd_comp_stats,
1150 .owner = THIS_MODULE
1151};
1152
1153/*************************************************************
1154 * Module support routines
1155 *************************************************************/
1156
1157static int __init bsdcomp_init(void)
1158{
1159 int answer = ppp_register_compressor(&ppp_bsd_compress);
1160 if (answer == 0)
1161 printk(KERN_INFO "PPP BSD Compression module registered\n");
1162 return answer;
1163}
1164
1165static void __exit bsdcomp_cleanup(void)
1166{
1167 ppp_unregister_compressor(&ppp_bsd_compress);
1168}
1169
1170module_init(bsdcomp_init);
1171module_exit(bsdcomp_cleanup);
1172MODULE_LICENSE("Dual BSD/GPL");
1173MODULE_ALIAS("ppp-compress-" __stringify(CI_BSD_COMPRESS));