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
115 struct 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
136 struct 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
168 static void bsd_free (void *state);
169 static void *bsd_alloc(unsigned char *options, int opt_len, int decomp);
170 static void *bsd_comp_alloc (unsigned char *options, int opt_len);
171 static void *bsd_decomp_alloc (unsigned char *options, int opt_len);
172
173 static int bsd_init (void *db, unsigned char *options,
174 int opt_len, int unit, int debug, int decomp);
175 static int bsd_comp_init (void *state, unsigned char *options,
176 int opt_len, int unit, int opthdr, int debug);
177 static int bsd_decomp_init (void *state, unsigned char *options,
178 int opt_len, int unit, int opthdr, int mru,
179 int debug);
180
181 static void bsd_reset (void *state);
182 static void bsd_comp_stats (void *state, struct compstat *stats);
183
184 static int bsd_compress (void *state, unsigned char *rptr,
185 unsigned char *obuf, int isize, int osize);
186 static void bsd_incomp (void *state, unsigned char *ibuf, int icnt);
187
188 static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
189 unsigned char *obuf, int osize);
190
191 /* These are in ppp_generic.c */
192 extern int ppp_register_compressor (struct compressor *cp);
193 extern 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
221 static void
bsd_clear(struct bsd_db * db)222 bsd_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
bsd_check(struct bsd_db * db)247 static 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
bsd_comp_stats(void * state,struct compstat * stats)293 static 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
bsd_reset(void * state)311 static 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
bsd_free(void * state)325 static 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
bsd_alloc(unsigned char * options,int opt_len,int decomp)352 static 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(array_size(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(array_size(sizeof(db->lens[0]), (maxmaxcode + 1)));
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
bsd_comp_alloc(unsigned char * options,int opt_len)449 static void *bsd_comp_alloc (unsigned char *options, int opt_len)
450 {
451 return bsd_alloc (options, opt_len, 0);
452 }
453
bsd_decomp_alloc(unsigned char * options,int opt_len)454 static 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
bsd_init(void * state,unsigned char * options,int opt_len,int unit,int debug,int decomp)463 static 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
bsd_comp_init(void * state,unsigned char * options,int opt_len,int unit,int opthdr,int debug)506 static 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
bsd_decomp_init(void * state,unsigned char * options,int opt_len,int unit,int opthdr,int mru,int debug)512 static 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
lens_ptr(struct bsd_db * db,int idx)527 static 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
dict_ptr(struct bsd_db * db,int idx)537 static 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
bsd_compress(void * state,unsigned char * rptr,unsigned char * obuf,int isize,int osize)563 static 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
694 nomatch:
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
bsd_incomp(void * state,unsigned char * ibuf,int icnt)805 static 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
bsd_decompress(void * state,unsigned char * ibuf,int isize,unsigned char * obuf,int osize)827 static 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
1132 static 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
bsdcomp_init(void)1154 static 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
bsdcomp_cleanup(void)1162 static void __exit bsdcomp_cleanup(void)
1163 {
1164 ppp_unregister_compressor(&ppp_bsd_compress);
1165 }
1166
1167 module_init(bsdcomp_init);
1168 module_exit(bsdcomp_cleanup);
1169 MODULE_LICENSE("Dual BSD/GPL");
1170 MODULE_ALIAS("ppp-compress-" __stringify(CI_BSD_COMPRESS));
1171
