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