FreeBSD/Linux Kernel Cross Reference
sys/net/bsd_comp.c
1 /*-
2 * Because this code is derived from the 4.3BSD compress source:
3 *
4 *
5 * Copyright (c) 1985, 1986 The Regents of the University of California.
6 * All rights reserved.
7 *
8 * This code is derived from software contributed to Berkeley by
9 * James A. Woods, derived from original work by Spencer Thomas
10 * and Joseph Orost.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 /*
38 * This version is for use with mbufs on BSD-derived systems.
39 *
40 * $FreeBSD: releng/7.4/sys/net/bsd_comp.c 163606 2006-10-22 11:52:19Z rwatson $
41 */
42
43 #include "opt_mac.h"
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/lock.h>
48 #include <sys/malloc.h>
49 #include <sys/mbuf.h>
50 #include <sys/mutex.h>
51
52 #include <net/ppp_defs.h>
53
54 #define PACKETPTR struct mbuf *
55 #include <net/ppp_comp.h>
56
57 #include <security/mac/mac_framework.h>
58
59 /*
60 * PPP "BSD compress" compression
61 * The differences between this compression and the classic BSD LZW
62 * source are obvious from the requirement that the classic code worked
63 * with files while this handles arbitrarily long streams that
64 * are broken into packets. They are:
65 *
66 * When the code size expands, a block of junk is not emitted by
67 * the compressor and not expected by the decompressor.
68 *
69 * New codes are not necessarily assigned every time an old
70 * code is output by the compressor. This is because a packet
71 * end forces a code to be emitted, but does not imply that a
72 * new sequence has been seen.
73 *
74 * The compression ratio is checked at the first end of a packet
75 * after the appropriate gap. Besides simplifying and speeding
76 * things up, this makes it more likely that the transmitter
77 * and receiver will agree when the dictionary is cleared when
78 * compression is not going well.
79 */
80
81 /*
82 * A dictionary for doing BSD compress.
83 */
84 struct bsd_db {
85 int totlen; /* length of this structure */
86 u_int hsize; /* size of the hash table */
87 u_char hshift; /* used in hash function */
88 u_char n_bits; /* current bits/code */
89 u_char maxbits;
90 u_char debug;
91 u_char unit;
92 u_int16_t seqno; /* sequence # of next packet */
93 u_int hdrlen; /* header length to preallocate */
94 u_int mru;
95 u_int maxmaxcode; /* largest valid code */
96 u_int max_ent; /* largest code in use */
97 u_int in_count; /* uncompressed bytes, aged */
98 u_int bytes_out; /* compressed bytes, aged */
99 u_int ratio; /* recent compression ratio */
100 u_int checkpoint; /* when to next check the ratio */
101 u_int clear_count; /* times dictionary cleared */
102 u_int incomp_count; /* incompressible packets */
103 u_int incomp_bytes; /* incompressible bytes */
104 u_int uncomp_count; /* uncompressed packets */
105 u_int uncomp_bytes; /* uncompressed bytes */
106 u_int comp_count; /* compressed packets */
107 u_int comp_bytes; /* compressed bytes */
108 u_int16_t *lens; /* array of lengths of codes */
109 struct bsd_dict {
110 union { /* hash value */
111 u_int32_t fcode;
112 struct {
113 #if BYTE_ORDER == LITTLE_ENDIAN
114 u_int16_t prefix; /* preceding code */
115 u_char suffix; /* last character of new code */
116 u_char pad;
117 #else
118 u_char pad;
119 u_char suffix; /* last character of new code */
120 u_int16_t prefix; /* preceding code */
121 #endif
122 } hs;
123 } f;
124 u_int16_t codem1; /* output of hash table -1 */
125 u_int16_t cptr; /* map code to hash table entry */
126 } dict[1];
127 };
128
129 #define BSD_OVHD 2 /* BSD compress overhead/packet */
130 #define BSD_INIT_BITS BSD_MIN_BITS
131
132 static void bsd_clear(struct bsd_db *db);
133 static int bsd_check(struct bsd_db *db);
134 static void *bsd_alloc(u_char *options, int opt_len, int decomp);
135 static int bsd_init(struct bsd_db *db, u_char *options, int opt_len,
136 int unit, int hdrlen, int mru, int debug, int decomp);
137 static void *bsd_comp_alloc(u_char *options, int opt_len);
138 static void *bsd_decomp_alloc(u_char *options, int opt_len);
139 static void bsd_free(void *state);
140 static int bsd_comp_init(void *state, u_char *options, int opt_len,
141 int unit, int hdrlen, int debug);
142 static int bsd_decomp_init(void *state, u_char *options, int opt_len,
143 int unit, int hdrlen, int mru, int debug);
144 static int bsd_compress(void *state, struct mbuf **mret, struct mbuf *mp,
145 int slen, int maxolen);
146 static void bsd_incomp(void *state, struct mbuf *dmsg);
147 static int bsd_decompress(void *state, struct mbuf *cmp,
148 struct mbuf **dmpp);
149 static void bsd_reset(void *state);
150 static void bsd_comp_stats(void *state, struct compstat *stats);
151
152 /*
153 * Procedures exported to if_ppp.c.
154 */
155 struct compressor ppp_bsd_compress = {
156 CI_BSD_COMPRESS, /* compress_proto */
157 bsd_comp_alloc, /* comp_alloc */
158 bsd_free, /* comp_free */
159 bsd_comp_init, /* comp_init */
160 bsd_reset, /* comp_reset */
161 bsd_compress, /* compress */
162 bsd_comp_stats, /* comp_stat */
163 bsd_decomp_alloc, /* decomp_alloc */
164 bsd_free, /* decomp_free */
165 bsd_decomp_init, /* decomp_init */
166 bsd_reset, /* decomp_reset */
167 bsd_decompress, /* decompress */
168 bsd_incomp, /* incomp */
169 bsd_comp_stats, /* decomp_stat */
170 };
171
172 /*
173 * the next two codes should not be changed lightly, as they must not
174 * lie within the contiguous general code space.
175 */
176 #define CLEAR 256 /* table clear output code */
177 #define FIRST 257 /* first free entry */
178 #define LAST 255
179
180 #define MAXCODE(b) ((1 << (b)) - 1)
181 #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
182
183 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
184 ^ (u_int32_t)(prefix))
185 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
186 + (u_int32_t)(prefix))
187
188 #define CHECK_GAP 10000 /* Ratio check interval */
189
190 #define RATIO_SCALE_LOG 8
191 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
192 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
193
194 /*
195 * clear the dictionary
196 */
197 static void
198 bsd_clear(db)
199 struct bsd_db *db;
200 {
201 db->clear_count++;
202 db->max_ent = FIRST-1;
203 db->n_bits = BSD_INIT_BITS;
204 db->ratio = 0;
205 db->bytes_out = 0;
206 db->in_count = 0;
207 db->checkpoint = CHECK_GAP;
208 }
209
210 /*
211 * If the dictionary is full, then see if it is time to reset it.
212 *
213 * Compute the compression ratio using fixed-point arithmetic
214 * with 8 fractional bits.
215 *
216 * Since we have an infinite stream instead of a single file,
217 * watch only the local compression ratio.
218 *
219 * Since both peers must reset the dictionary at the same time even in
220 * the absence of CLEAR codes (while packets are incompressible), they
221 * must compute the same ratio.
222 */
223 static int /* 1=output CLEAR */
224 bsd_check(db)
225 struct bsd_db *db;
226 {
227 u_int new_ratio;
228
229 if (db->in_count >= db->checkpoint) {
230 /* age the ratio by limiting the size of the counts */
231 if (db->in_count >= RATIO_MAX
232 || db->bytes_out >= RATIO_MAX) {
233 db->in_count -= db->in_count/4;
234 db->bytes_out -= db->bytes_out/4;
235 }
236
237 db->checkpoint = db->in_count + CHECK_GAP;
238
239 if (db->max_ent >= db->maxmaxcode) {
240 /* Reset the dictionary only if the ratio is worse,
241 * or if it looks as if it has been poisoned
242 * by incompressible data.
243 *
244 * This does not overflow, because
245 * db->in_count <= RATIO_MAX.
246 */
247 new_ratio = db->in_count << RATIO_SCALE_LOG;
248 if (db->bytes_out != 0)
249 new_ratio /= db->bytes_out;
250
251 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
252 bsd_clear(db);
253 return 1;
254 }
255 db->ratio = new_ratio;
256 }
257 }
258 return 0;
259 }
260
261 /*
262 * Return statistics.
263 */
264 static void
265 bsd_comp_stats(state, stats)
266 void *state;
267 struct compstat *stats;
268 {
269 struct bsd_db *db = (struct bsd_db *) state;
270 u_int out;
271
272 stats->unc_bytes = db->uncomp_bytes;
273 stats->unc_packets = db->uncomp_count;
274 stats->comp_bytes = db->comp_bytes;
275 stats->comp_packets = db->comp_count;
276 stats->inc_bytes = db->incomp_bytes;
277 stats->inc_packets = db->incomp_count;
278 stats->ratio = db->in_count;
279 out = db->bytes_out;
280 if (stats->ratio <= 0x7fffff)
281 stats->ratio <<= 8;
282 else
283 out >>= 8;
284 if (out != 0)
285 stats->ratio /= out;
286 }
287
288 /*
289 * Reset state, as on a CCP ResetReq.
290 */
291 static void
292 bsd_reset(state)
293 void *state;
294 {
295 struct bsd_db *db = (struct bsd_db *) state;
296
297 db->seqno = 0;
298 bsd_clear(db);
299 db->clear_count = 0;
300 }
301
302 /*
303 * Allocate space for a (de) compressor.
304 */
305 static void *
306 bsd_alloc(options, opt_len, decomp)
307 u_char *options;
308 int opt_len, decomp;
309 {
310 int bits;
311 u_int newlen, hsize, hshift, maxmaxcode;
312 struct bsd_db *db;
313
314 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
315 || options[1] != CILEN_BSD_COMPRESS
316 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
317 return NULL;
318 bits = BSD_NBITS(options[2]);
319 switch (bits) {
320 case 9: /* needs 82152 for both directions */
321 case 10: /* needs 84144 */
322 case 11: /* needs 88240 */
323 case 12: /* needs 96432 */
324 hsize = 5003;
325 hshift = 4;
326 break;
327 case 13: /* needs 176784 */
328 hsize = 9001;
329 hshift = 5;
330 break;
331 case 14: /* needs 353744 */
332 hsize = 18013;
333 hshift = 6;
334 break;
335 case 15: /* needs 691440 */
336 hsize = 35023;
337 hshift = 7;
338 break;
339 case 16: /* needs 1366160--far too much, */
340 /* hsize = 69001; */ /* and 69001 is too big for cptr */
341 /* hshift = 8; */ /* in struct bsd_db */
342 /* break; */
343 default:
344 return NULL;
345 }
346
347 maxmaxcode = MAXCODE(bits);
348 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
349 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
350 if (!db)
351 return NULL;
352 bzero(db, sizeof(*db) - sizeof(db->dict));
353
354 if (!decomp) {
355 db->lens = NULL;
356 } else {
357 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
358 M_DEVBUF, M_NOWAIT);
359 if (!db->lens) {
360 free(db, M_DEVBUF);
361 return NULL;
362 }
363 }
364
365 db->totlen = newlen;
366 db->hsize = hsize;
367 db->hshift = hshift;
368 db->maxmaxcode = maxmaxcode;
369 db->maxbits = bits;
370
371 return (void *) db;
372 }
373
374 static void
375 bsd_free(state)
376 void *state;
377 {
378 struct bsd_db *db = (struct bsd_db *) state;
379
380 if (db->lens)
381 free(db->lens, M_DEVBUF);
382 free(db, M_DEVBUF);
383 }
384
385 static void *
386 bsd_comp_alloc(options, opt_len)
387 u_char *options;
388 int opt_len;
389 {
390 return bsd_alloc(options, opt_len, 0);
391 }
392
393 static void *
394 bsd_decomp_alloc(options, opt_len)
395 u_char *options;
396 int opt_len;
397 {
398 return bsd_alloc(options, opt_len, 1);
399 }
400
401 /*
402 * Initialize the database.
403 */
404 static int
405 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
406 struct bsd_db *db;
407 u_char *options;
408 int opt_len, unit, hdrlen, mru, debug, decomp;
409 {
410 int i;
411
412 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
413 || options[1] != CILEN_BSD_COMPRESS
414 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
415 || BSD_NBITS(options[2]) != db->maxbits
416 || (decomp && db->lens == NULL))
417 return 0;
418
419 if (decomp) {
420 i = LAST+1;
421 while (i != 0)
422 db->lens[--i] = 1;
423 }
424 i = db->hsize;
425 while (i != 0) {
426 db->dict[--i].codem1 = BADCODEM1;
427 db->dict[i].cptr = 0;
428 }
429
430 db->unit = unit;
431 db->hdrlen = hdrlen;
432 db->mru = mru;
433 #ifndef DEBUG
434 if (debug)
435 #endif
436 db->debug = 1;
437
438 bsd_reset(db);
439
440 return 1;
441 }
442
443 static int
444 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
445 void *state;
446 u_char *options;
447 int opt_len, unit, hdrlen, debug;
448 {
449 return bsd_init((struct bsd_db *) state, options, opt_len,
450 unit, hdrlen, 0, debug, 0);
451 }
452
453 static int
454 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
455 void *state;
456 u_char *options;
457 int opt_len, unit, hdrlen, mru, debug;
458 {
459 return bsd_init((struct bsd_db *) state, options, opt_len,
460 unit, hdrlen, mru, debug, 1);
461 }
462
463
464 /*
465 * compress a packet
466 * One change from the BSD compress command is that when the
467 * code size expands, we do not output a bunch of padding.
468 */
469 static int /* new slen */
470 bsd_compress(state, mret, mp, slen, maxolen)
471 void *state;
472 struct mbuf **mret; /* return compressed mbuf chain here */
473 struct mbuf *mp; /* from here */
474 int slen; /* uncompressed length */
475 int maxolen; /* max compressed length */
476 {
477 struct bsd_db *db = (struct bsd_db *) state;
478 int hshift = db->hshift;
479 u_int max_ent = db->max_ent;
480 u_int n_bits = db->n_bits;
481 u_int bitno = 32;
482 u_int32_t accm = 0, fcode;
483 struct bsd_dict *dictp;
484 u_char c;
485 int hval, disp, ent, ilen;
486 u_char *rptr, *wptr;
487 u_char *cp_end;
488 int olen;
489 struct mbuf *m;
490
491 #define PUTBYTE(v) { \
492 ++olen; \
493 if (wptr) { \
494 *wptr++ = (v); \
495 if (wptr >= cp_end) { \
496 m->m_len = wptr - mtod(m, u_char *); \
497 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
498 m = m->m_next; \
499 if (m) { \
500 m->m_len = 0; \
501 if (maxolen - olen > MLEN) \
502 MCLGET(m, M_DONTWAIT); \
503 wptr = mtod(m, u_char *); \
504 cp_end = wptr + M_TRAILINGSPACE(m); \
505 } else \
506 wptr = NULL; \
507 } \
508 } \
509 }
510
511 #define OUTPUT(ent) { \
512 bitno -= n_bits; \
513 accm |= ((ent) << bitno); \
514 do { \
515 PUTBYTE(accm >> 24); \
516 accm <<= 8; \
517 bitno += 8; \
518 } while (bitno <= 24); \
519 }
520
521 /*
522 * If the protocol is not in the range we're interested in,
523 * just return without compressing the packet. If it is,
524 * the protocol becomes the first byte to compress.
525 */
526 rptr = mtod(mp, u_char *);
527 ent = PPP_PROTOCOL(rptr);
528 if (ent < 0x21 || ent > 0xf9) {
529 *mret = NULL;
530 return slen;
531 }
532
533 /* Don't generate compressed packets which are larger than
534 the uncompressed packet. */
535 if (maxolen > slen)
536 maxolen = slen;
537
538 /* Allocate one mbuf to start with. */
539 MGET(m, M_DONTWAIT, MT_DATA);
540 *mret = m;
541 if (m != NULL) {
542 m->m_len = 0;
543 if (maxolen + db->hdrlen > MLEN)
544 MCLGET(m, M_DONTWAIT);
545 m->m_data += db->hdrlen;
546 wptr = mtod(m, u_char *);
547 cp_end = wptr + M_TRAILINGSPACE(m);
548 } else
549 wptr = cp_end = NULL;
550
551 /*
552 * Copy the PPP header over, changing the protocol,
553 * and install the 2-byte packet sequence number.
554 */
555 if (wptr) {
556 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
557 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
558 *wptr++ = 0; /* change the protocol */
559 *wptr++ = PPP_COMP;
560 *wptr++ = db->seqno >> 8;
561 *wptr++ = db->seqno;
562 }
563 ++db->seqno;
564
565 olen = 0;
566 rptr += PPP_HDRLEN;
567 slen = mp->m_len - PPP_HDRLEN;
568 ilen = slen + 1;
569 for (;;) {
570 if (slen <= 0) {
571 mp = mp->m_next;
572 if (!mp)
573 break;
574 rptr = mtod(mp, u_char *);
575 slen = mp->m_len;
576 if (!slen)
577 continue; /* handle 0-length buffers */
578 ilen += slen;
579 }
580
581 slen--;
582 c = *rptr++;
583 fcode = BSD_KEY(ent, c);
584 hval = BSD_HASH(ent, c, hshift);
585 dictp = &db->dict[hval];
586
587 /* Validate and then check the entry. */
588 if (dictp->codem1 >= max_ent)
589 goto nomatch;
590 if (dictp->f.fcode == fcode) {
591 ent = dictp->codem1+1;
592 continue; /* found (prefix,suffix) */
593 }
594
595 /* continue probing until a match or invalid entry */
596 disp = (hval == 0) ? 1 : hval;
597 do {
598 hval += disp;
599 if (hval >= db->hsize)
600 hval -= db->hsize;
601 dictp = &db->dict[hval];
602 if (dictp->codem1 >= max_ent)
603 goto nomatch;
604 } while (dictp->f.fcode != fcode);
605 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
606 continue;
607
608 nomatch:
609 OUTPUT(ent); /* output the prefix */
610
611 /* code -> hashtable */
612 if (max_ent < db->maxmaxcode) {
613 struct bsd_dict *dictp2;
614 /* expand code size if needed */
615 if (max_ent >= MAXCODE(n_bits))
616 db->n_bits = ++n_bits;
617
618 /* Invalidate old hash table entry using
619 * this code, and then take it over.
620 */
621 dictp2 = &db->dict[max_ent+1];
622 if (db->dict[dictp2->cptr].codem1 == max_ent)
623 db->dict[dictp2->cptr].codem1 = BADCODEM1;
624 dictp2->cptr = hval;
625 dictp->codem1 = max_ent;
626 dictp->f.fcode = fcode;
627
628 db->max_ent = ++max_ent;
629 }
630 ent = c;
631 }
632
633 OUTPUT(ent); /* output the last code */
634 db->bytes_out += olen;
635 db->in_count += ilen;
636 if (bitno < 32)
637 ++db->bytes_out; /* count complete bytes */
638
639 if (bsd_check(db))
640 OUTPUT(CLEAR); /* do not count the CLEAR */
641
642 /*
643 * Pad dribble bits of last code with ones.
644 * Do not emit a completely useless byte of ones.
645 */
646 if (bitno != 32)
647 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
648
649 if (m != NULL) {
650 m->m_len = wptr - mtod(m, u_char *);
651 m->m_next = NULL;
652 }
653
654 /*
655 * Increase code size if we would have without the packet
656 * boundary and as the decompressor will.
657 */
658 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
659 db->n_bits++;
660
661 db->uncomp_bytes += ilen;
662 ++db->uncomp_count;
663 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
664 /* throw away the compressed stuff if it is longer than uncompressed */
665 if (*mret != NULL) {
666 m_freem(*mret);
667 *mret = NULL;
668 }
669 ++db->incomp_count;
670 db->incomp_bytes += ilen;
671 } else {
672 ++db->comp_count;
673 db->comp_bytes += olen + BSD_OVHD;
674 }
675
676 return olen + PPP_HDRLEN + BSD_OVHD;
677 #undef OUTPUT
678 #undef PUTBYTE
679 }
680
681
682 /*
683 * Update the "BSD Compress" dictionary on the receiver for
684 * incompressible data by pretending to compress the incoming data.
685 */
686 static void
687 bsd_incomp(state, dmsg)
688 void *state;
689 struct mbuf *dmsg;
690 {
691 struct bsd_db *db = (struct bsd_db *) state;
692 u_int hshift = db->hshift;
693 u_int max_ent = db->max_ent;
694 u_int n_bits = db->n_bits;
695 struct bsd_dict *dictp;
696 u_int32_t fcode;
697 u_char c;
698 u_int32_t hval, disp;
699 int slen, ilen;
700 u_int bitno = 7;
701 u_char *rptr;
702 u_int ent;
703
704 /*
705 * If the protocol is not in the range we're interested in,
706 * just return without looking at the packet. If it is,
707 * the protocol becomes the first byte to "compress".
708 */
709 rptr = mtod(dmsg, u_char *);
710 ent = PPP_PROTOCOL(rptr);
711 if (ent < 0x21 || ent > 0xf9)
712 return;
713
714 db->seqno++;
715 ilen = 1; /* count the protocol as 1 byte */
716 rptr += PPP_HDRLEN;
717 slen = dmsg->m_len - PPP_HDRLEN;
718 for (;;) {
719 if (slen <= 0) {
720 dmsg = dmsg->m_next;
721 if (!dmsg)
722 break;
723 rptr = mtod(dmsg, u_char *);
724 slen = dmsg->m_len;
725 continue;
726 }
727 ilen += slen;
728
729 do {
730 c = *rptr++;
731 fcode = BSD_KEY(ent, c);
732 hval = BSD_HASH(ent, c, hshift);
733 dictp = &db->dict[hval];
734
735 /* validate and then check the entry */
736 if (dictp->codem1 >= max_ent)
737 goto nomatch;
738 if (dictp->f.fcode == fcode) {
739 ent = dictp->codem1+1;
740 continue; /* found (prefix,suffix) */
741 }
742
743 /* continue probing until a match or invalid entry */
744 disp = (hval == 0) ? 1 : hval;
745 do {
746 hval += disp;
747 if (hval >= db->hsize)
748 hval -= db->hsize;
749 dictp = &db->dict[hval];
750 if (dictp->codem1 >= max_ent)
751 goto nomatch;
752 } while (dictp->f.fcode != fcode);
753 ent = dictp->codem1+1;
754 continue; /* finally found (prefix,suffix) */
755
756 nomatch: /* output (count) the prefix */
757 bitno += n_bits;
758
759 /* code -> hashtable */
760 if (max_ent < db->maxmaxcode) {
761 struct bsd_dict *dictp2;
762 /* expand code size if needed */
763 if (max_ent >= MAXCODE(n_bits))
764 db->n_bits = ++n_bits;
765
766 /* Invalidate previous hash table entry
767 * assigned this code, and then take it over.
768 */
769 dictp2 = &db->dict[max_ent+1];
770 if (db->dict[dictp2->cptr].codem1 == max_ent)
771 db->dict[dictp2->cptr].codem1 = BADCODEM1;
772 dictp2->cptr = hval;
773 dictp->codem1 = max_ent;
774 dictp->f.fcode = fcode;
775
776 db->max_ent = ++max_ent;
777 db->lens[max_ent] = db->lens[ent]+1;
778 }
779 ent = c;
780 } while (--slen != 0);
781 }
782 bitno += n_bits; /* output (count) the last code */
783 db->bytes_out += bitno/8;
784 db->in_count += ilen;
785 (void)bsd_check(db);
786
787 ++db->incomp_count;
788 db->incomp_bytes += ilen;
789 ++db->uncomp_count;
790 db->uncomp_bytes += ilen;
791
792 /* Increase code size if we would have without the packet
793 * boundary and as the decompressor will.
794 */
795 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
796 db->n_bits++;
797 }
798
799
800 /*
801 * Decompress "BSD Compress".
802 *
803 * Because of patent problems, we return DECOMP_ERROR for errors
804 * found by inspecting the input data and for system problems, but
805 * DECOMP_FATALERROR for any errors which could possibly be said to
806 * be being detected "after" decompression. For DECOMP_ERROR,
807 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
808 * infringing a patent of Motorola's if we do, so we take CCP down
809 * instead.
810 *
811 * Given that the frame has the correct sequence number and a good FCS,
812 * errors such as invalid codes in the input most likely indicate a
813 * bug, so we return DECOMP_FATALERROR for them in order to turn off
814 * compression, even though they are detected by inspecting the input.
815 */
816 static int
817 bsd_decompress(state, cmp, dmpp)
818 void *state;
819 struct mbuf *cmp, **dmpp;
820 {
821 struct bsd_db *db = (struct bsd_db *) state;
822 u_int max_ent = db->max_ent;
823 u_int32_t accm = 0;
824 u_int bitno = 32; /* 1st valid bit in accm */
825 u_int n_bits = db->n_bits;
826 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
827 struct bsd_dict *dictp;
828 int explen, i, seq, len;
829 u_int incode, oldcode, finchar;
830 u_char *p, *rptr, *wptr;
831 struct mbuf *m, *dmp, *mret;
832 int adrs, ctrl, ilen;
833 int space, codelen, extra;
834
835 /*
836 * Save the address/control from the PPP header
837 * and then get the sequence number.
838 */
839 *dmpp = NULL;
840 rptr = mtod(cmp, u_char *);
841 adrs = PPP_ADDRESS(rptr);
842 ctrl = PPP_CONTROL(rptr);
843 rptr += PPP_HDRLEN;
844 len = cmp->m_len - PPP_HDRLEN;
845 seq = 0;
846 for (i = 0; i < 2; ++i) {
847 while (len <= 0) {
848 cmp = cmp->m_next;
849 if (cmp == NULL)
850 return DECOMP_ERROR;
851 rptr = mtod(cmp, u_char *);
852 len = cmp->m_len;
853 }
854 seq = (seq << 8) + *rptr++;
855 --len;
856 }
857
858 /*
859 * Check the sequence number and give up if it differs from
860 * the value we're expecting.
861 */
862 if (seq != db->seqno) {
863 if (db->debug)
864 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
865 db->unit, seq, db->seqno - 1);
866 return DECOMP_ERROR;
867 }
868 ++db->seqno;
869
870 /*
871 * Allocate one mbuf to start with.
872 */
873 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
874 if (dmp == NULL)
875 return DECOMP_ERROR;
876 mret = dmp;
877 dmp->m_len = 0;
878 dmp->m_next = NULL;
879 MCLGET(dmp, M_DONTWAIT);
880 dmp->m_data += db->hdrlen;
881 wptr = mtod(dmp, u_char *);
882 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
883 #ifdef MAC
884 mac_copy_mbuf(cmp, dmp);
885 #endif
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 wptr[0] = adrs;
892 wptr[1] = ctrl;
893 wptr[2] = 0;
894 wptr += PPP_HDRLEN - 1;
895
896 ilen = len;
897 oldcode = CLEAR;
898 explen = 0;
899 for (;;) {
900 if (len == 0) {
901 cmp = cmp->m_next;
902 if (!cmp) /* quit at end of message */
903 break;
904 rptr = mtod(cmp, u_char *);
905 len = cmp->m_len;
906 ilen += len;
907 continue; /* handle 0-length buffers */
908 }
909
910 /*
911 * Accumulate bytes until we have a complete code.
912 * Then get the next code, relying on the 32-bit,
913 * unsigned accm to mask the result.
914 */
915 bitno -= 8;
916 accm |= *rptr++ << bitno;
917 --len;
918 if (tgtbitno < bitno)
919 continue;
920 incode = accm >> tgtbitno;
921 accm <<= n_bits;
922 bitno += n_bits;
923
924 if (incode == CLEAR) {
925 /*
926 * The dictionary must only be cleared at
927 * the end of a packet. But there could be an
928 * empty mbuf at the end.
929 */
930 if (len > 0 || cmp->m_next != NULL) {
931 while ((cmp = cmp->m_next) != NULL)
932 len += cmp->m_len;
933 if (len > 0) {
934 m_freem(mret);
935 if (db->debug)
936 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
937 return DECOMP_FATALERROR; /* probably a bug */
938 }
939 }
940 bsd_clear(db);
941 explen = ilen = 0;
942 break;
943 }
944
945 if (incode > max_ent + 2 || incode > db->maxmaxcode
946 || (incode > max_ent && oldcode == CLEAR)) {
947 m_freem(mret);
948 if (db->debug) {
949 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
950 db->unit, incode, oldcode);
951 printf("max_ent=0x%x explen=%d seqno=%d\n",
952 max_ent, explen, db->seqno);
953 }
954 return DECOMP_FATALERROR; /* probably a bug */
955 }
956
957 /* Special case for KwKwK string. */
958 if (incode > max_ent) {
959 finchar = oldcode;
960 extra = 1;
961 } else {
962 finchar = incode;
963 extra = 0;
964 }
965
966 codelen = db->lens[finchar];
967 explen += codelen + extra;
968 if (explen > db->mru + 1) {
969 m_freem(mret);
970 if (db->debug) {
971 printf("bsd_decomp%d: ran out of mru\n", db->unit);
972 #ifdef DEBUG
973 while ((cmp = cmp->m_next) != NULL)
974 len += cmp->m_len;
975 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
976 len, finchar, codelen, explen);
977 #endif
978 }
979 return DECOMP_FATALERROR;
980 }
981
982 /*
983 * For simplicity, the decoded characters go in a single mbuf,
984 * so we allocate a single extra cluster mbuf if necessary.
985 */
986 if ((space -= codelen + extra) < 0) {
987 dmp->m_len = wptr - mtod(dmp, u_char *);
988 MGET(m, M_DONTWAIT, MT_DATA);
989 if (m == NULL) {
990 m_freem(mret);
991 return DECOMP_ERROR;
992 }
993 m->m_len = 0;
994 m->m_next = NULL;
995 dmp->m_next = m;
996 MCLGET(m, M_DONTWAIT);
997 space = M_TRAILINGSPACE(m) - (codelen + extra);
998 if (space < 0) {
999 /* now that's what I call *compression*. */
1000 m_freem(mret);
1001 return DECOMP_ERROR;
1002 }
1003 dmp = m;
1004 wptr = mtod(dmp, u_char *);
1005 }
1006
1007 /*
1008 * Decode this code and install it in the decompressed buffer.
1009 */
1010 p = (wptr += codelen);
1011 while (finchar > LAST) {
1012 dictp = &db->dict[db->dict[finchar].cptr];
1013 #ifdef DEBUG
1014 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1015 goto bad;
1016 #endif
1017 *--p = dictp->f.hs.suffix;
1018 finchar = dictp->f.hs.prefix;
1019 }
1020 *--p = finchar;
1021
1022 #ifdef DEBUG
1023 if (--codelen != 0)
1024 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1025 db->unit, codelen, incode, max_ent);
1026 #endif
1027
1028 if (extra) /* the KwKwK case again */
1029 *wptr++ = finchar;
1030
1031 /*
1032 * If not first code in a packet, and
1033 * if not out of code space, then allocate a new code.
1034 *
1035 * Keep the hash table correct so it can be used
1036 * with uncompressed packets.
1037 */
1038 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1039 struct bsd_dict *dictp2;
1040 u_int32_t fcode;
1041 u_int32_t hval, disp;
1042
1043 fcode = BSD_KEY(oldcode,finchar);
1044 hval = BSD_HASH(oldcode,finchar,db->hshift);
1045 dictp = &db->dict[hval];
1046
1047 /* look for a free hash table entry */
1048 if (dictp->codem1 < max_ent) {
1049 disp = (hval == 0) ? 1 : hval;
1050 do {
1051 hval += disp;
1052 if (hval >= db->hsize)
1053 hval -= db->hsize;
1054 dictp = &db->dict[hval];
1055 } while (dictp->codem1 < max_ent);
1056 }
1057
1058 /*
1059 * Invalidate previous hash table entry
1060 * assigned this code, and then take it over
1061 */
1062 dictp2 = &db->dict[max_ent+1];
1063 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1064 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1065 }
1066 dictp2->cptr = hval;
1067 dictp->codem1 = max_ent;
1068 dictp->f.fcode = fcode;
1069
1070 db->max_ent = ++max_ent;
1071 db->lens[max_ent] = db->lens[oldcode]+1;
1072
1073 /* Expand code size if needed. */
1074 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1075 db->n_bits = ++n_bits;
1076 tgtbitno = 32-n_bits;
1077 }
1078 }
1079 oldcode = incode;
1080 }
1081 dmp->m_len = wptr - mtod(dmp, u_char *);
1082
1083 /*
1084 * Keep the checkpoint right so that incompressible packets
1085 * clear the dictionary at the right times.
1086 */
1087 db->bytes_out += ilen;
1088 db->in_count += explen;
1089 if (bsd_check(db) && db->debug) {
1090 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1091 db->unit);
1092 }
1093
1094 ++db->comp_count;
1095 db->comp_bytes += ilen + BSD_OVHD;
1096 ++db->uncomp_count;
1097 db->uncomp_bytes += explen;
1098
1099 *dmpp = mret;
1100 return DECOMP_OK;
1101
1102 #ifdef DEBUG
1103 bad:
1104 if (codelen <= 0) {
1105 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1106 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1107 incode, finchar, db->dict[finchar].cptr, max_ent);
1108 } else if (dictp->codem1 != finchar-1) {
1109 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1110 db->unit, incode, finchar);
1111 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1112 db->dict[finchar].cptr, dictp->codem1);
1113 }
1114 m_freem(mret);
1115 return DECOMP_FATALERROR;
1116 #endif /* DEBUG */
1117 }
Cache object: 2185a60a9505c44c09490c26d32639d3
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