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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 | |
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 |
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 | |
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 | |
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 | |
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 | |
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 | |
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(hsize * sizeof(struct bsd_dict)); |
410 | if (!db->dict) |
411 | { |
412 | bsd_free (db); |
413 | return NULL; |
414 | } |
415 | |
416 | /* |
417 | * If this is the compression buffer then there is no length data. |
418 | */ |
419 | if (!decomp) |
420 | { |
421 | db->lens = NULL; |
422 | } |
423 | /* |
424 | * For decompression, the length information is needed as well. |
425 | */ |
426 | else |
427 | { |
428 | db->lens = vmalloc((maxmaxcode + 1) * sizeof(db->lens[0])); |
429 | if (!db->lens) |
430 | { |
431 | bsd_free (db); |
432 | return (NULL); |
433 | } |
434 | } |
435 | /* |
436 | * Initialize the data information for the compression code |
437 | */ |
438 | db->totlen = sizeof (struct bsd_db) + |
439 | (sizeof (struct bsd_dict) * hsize); |
440 | |
441 | db->hsize = hsize; |
442 | db->hshift = hshift; |
443 | db->maxmaxcode = maxmaxcode; |
444 | db->maxbits = bits; |
445 | |
446 | return (void *) db; |
447 | } |
448 | |
449 | static void *bsd_comp_alloc (unsigned char *options, int opt_len) |
450 | { |
451 | return bsd_alloc (options, opt_len, 0); |
452 | } |
453 | |
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 | |
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 | |
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 | |
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 |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |
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 |
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