FreeBSD/Linux Kernel Cross Reference
sys/net/bsd_comp.c
1 /* Because this code is derived from the 4.3BSD compress source:
2 *
3 *
4 * Copyright (c) 1985, 1986 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * James A. Woods, derived from original work by Spencer Thomas
9 * and Joseph Orost.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by the University of
22 * California, Berkeley and its contributors.
23 * 4. Neither the name of the University nor the names of its contributors
24 * may be used to endorse or promote products derived from this software
25 * without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 */
39
40 /*
41 * This version is for use with mbufs on BSD-derived systems.
42 *
43 * $FreeBSD$
44 */
45
46 #include <sys/param.h>
47 #include <sys/systm.h>
48 #include <sys/malloc.h>
49 #include <sys/mbuf.h>
50 #include <net/ppp_defs.h>
51
52 #define PACKETPTR struct mbuf *
53 #include <net/ppp_comp.h>
54
55 #if DO_BSD_COMPRESS
56 /*
57 * PPP "BSD compress" compression
58 * The differences between this compression and the classic BSD LZW
59 * source are obvious from the requirement that the classic code worked
60 * with files while this handles arbitrarily long streams that
61 * are broken into packets. They are:
62 *
63 * When the code size expands, a block of junk is not emitted by
64 * the compressor and not expected by the decompressor.
65 *
66 * New codes are not necessarily assigned every time an old
67 * code is output by the compressor. This is because a packet
68 * end forces a code to be emitted, but does not imply that a
69 * new sequence has been seen.
70 *
71 * The compression ratio is checked at the first end of a packet
72 * after the appropriate gap. Besides simplifying and speeding
73 * things up, this makes it more likely that the transmitter
74 * and receiver will agree when the dictionary is cleared when
75 * compression is not going well.
76 */
77
78 /*
79 * A dictionary for doing BSD compress.
80 */
81 struct bsd_db {
82 int totlen; /* length of this structure */
83 u_int hsize; /* size of the hash table */
84 u_char hshift; /* used in hash function */
85 u_char n_bits; /* current bits/code */
86 u_char maxbits;
87 u_char debug;
88 u_char unit;
89 u_int16_t seqno; /* sequence # of next packet */
90 u_int hdrlen; /* header length to preallocate */
91 u_int mru;
92 u_int maxmaxcode; /* largest valid code */
93 u_int max_ent; /* largest code in use */
94 u_int in_count; /* uncompressed bytes, aged */
95 u_int bytes_out; /* compressed bytes, aged */
96 u_int ratio; /* recent compression ratio */
97 u_int checkpoint; /* when to next check the ratio */
98 u_int clear_count; /* times dictionary cleared */
99 u_int incomp_count; /* incompressible packets */
100 u_int incomp_bytes; /* incompressible bytes */
101 u_int uncomp_count; /* uncompressed packets */
102 u_int uncomp_bytes; /* uncompressed bytes */
103 u_int comp_count; /* compressed packets */
104 u_int comp_bytes; /* compressed bytes */
105 u_int16_t *lens; /* array of lengths of codes */
106 struct bsd_dict {
107 union { /* hash value */
108 u_int32_t fcode;
109 struct {
110 #if BYTE_ORDER == LITTLE_ENDIAN
111 u_int16_t prefix; /* preceding code */
112 u_char suffix; /* last character of new code */
113 u_char pad;
114 #else
115 u_char pad;
116 u_char suffix; /* last character of new code */
117 u_int16_t prefix; /* preceding code */
118 #endif
119 } hs;
120 } f;
121 u_int16_t codem1; /* output of hash table -1 */
122 u_int16_t cptr; /* map code to hash table entry */
123 } dict[1];
124 };
125
126 #define BSD_OVHD 2 /* BSD compress overhead/packet */
127 #define BSD_INIT_BITS BSD_MIN_BITS
128
129 static void bsd_clear __P((struct bsd_db *db));
130 static int bsd_check __P((struct bsd_db *db));
131 static void *bsd_alloc __P((u_char *options, int opt_len, int decomp));
132 static int bsd_init __P((struct bsd_db *db, u_char *options, int opt_len,
133 int unit, int hdrlen, int mru, int debug,
134 int decomp));
135 static void *bsd_comp_alloc __P((u_char *options, int opt_len));
136 static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
137 static void bsd_free __P((void *state));
138 static int bsd_comp_init __P((void *state, u_char *options, int opt_len,
139 int unit, int hdrlen, int debug));
140 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
141 int unit, int hdrlen, int mru, int debug));
142 static int bsd_compress __P((void *state, struct mbuf **mret,
143 struct mbuf *mp, int slen, int maxolen));
144 static void bsd_incomp __P((void *state, struct mbuf *dmsg));
145 static int bsd_decompress __P((void *state, struct mbuf *cmp,
146 struct mbuf **dmpp));
147 static void bsd_reset __P((void *state));
148 static void bsd_comp_stats __P((void *state, struct compstat *stats));
149
150 /*
151 * Procedures exported to if_ppp.c.
152 */
153 struct compressor ppp_bsd_compress = {
154 CI_BSD_COMPRESS, /* compress_proto */
155 bsd_comp_alloc, /* comp_alloc */
156 bsd_free, /* comp_free */
157 bsd_comp_init, /* comp_init */
158 bsd_reset, /* comp_reset */
159 bsd_compress, /* compress */
160 bsd_comp_stats, /* comp_stat */
161 bsd_decomp_alloc, /* decomp_alloc */
162 bsd_free, /* decomp_free */
163 bsd_decomp_init, /* decomp_init */
164 bsd_reset, /* decomp_reset */
165 bsd_decompress, /* decompress */
166 bsd_incomp, /* incomp */
167 bsd_comp_stats, /* decomp_stat */
168 };
169
170 /*
171 * the next two codes should not be changed lightly, as they must not
172 * lie within the contiguous general code space.
173 */
174 #define CLEAR 256 /* table clear output code */
175 #define FIRST 257 /* first free entry */
176 #define LAST 255
177
178 #define MAXCODE(b) ((1 << (b)) - 1)
179 #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
180
181 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
182 ^ (u_int32_t)(prefix))
183 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
184 + (u_int32_t)(prefix))
185
186 #define CHECK_GAP 10000 /* Ratio check interval */
187
188 #define RATIO_SCALE_LOG 8
189 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
190 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
191
192 /*
193 * clear the dictionary
194 */
195 static void
196 bsd_clear(db)
197 struct bsd_db *db;
198 {
199 db->clear_count++;
200 db->max_ent = FIRST-1;
201 db->n_bits = BSD_INIT_BITS;
202 db->ratio = 0;
203 db->bytes_out = 0;
204 db->in_count = 0;
205 db->checkpoint = CHECK_GAP;
206 }
207
208 /*
209 * If the dictionary is full, then see if it is time to reset it.
210 *
211 * Compute the compression ratio using fixed-point arithmetic
212 * with 8 fractional bits.
213 *
214 * Since we have an infinite stream instead of a single file,
215 * watch only the local compression ratio.
216 *
217 * Since both peers must reset the dictionary at the same time even in
218 * the absence of CLEAR codes (while packets are incompressible), they
219 * must compute the same ratio.
220 */
221 static int /* 1=output CLEAR */
222 bsd_check(db)
223 struct bsd_db *db;
224 {
225 u_int new_ratio;
226
227 if (db->in_count >= db->checkpoint) {
228 /* age the ratio by limiting the size of the counts */
229 if (db->in_count >= RATIO_MAX
230 || db->bytes_out >= RATIO_MAX) {
231 db->in_count -= db->in_count/4;
232 db->bytes_out -= db->bytes_out/4;
233 }
234
235 db->checkpoint = db->in_count + CHECK_GAP;
236
237 if (db->max_ent >= db->maxmaxcode) {
238 /* Reset the dictionary only if the ratio is worse,
239 * or if it looks as if it has been poisoned
240 * by incompressible data.
241 *
242 * This does not overflow, because
243 * db->in_count <= RATIO_MAX.
244 */
245 new_ratio = db->in_count << RATIO_SCALE_LOG;
246 if (db->bytes_out != 0)
247 new_ratio /= db->bytes_out;
248
249 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
250 bsd_clear(db);
251 return 1;
252 }
253 db->ratio = new_ratio;
254 }
255 }
256 return 0;
257 }
258
259 /*
260 * Return statistics.
261 */
262 static void
263 bsd_comp_stats(state, stats)
264 void *state;
265 struct compstat *stats;
266 {
267 struct bsd_db *db = (struct bsd_db *) state;
268 u_int out;
269
270 stats->unc_bytes = db->uncomp_bytes;
271 stats->unc_packets = db->uncomp_count;
272 stats->comp_bytes = db->comp_bytes;
273 stats->comp_packets = db->comp_count;
274 stats->inc_bytes = db->incomp_bytes;
275 stats->inc_packets = db->incomp_count;
276 stats->ratio = db->in_count;
277 out = db->bytes_out;
278 if (stats->ratio <= 0x7fffff)
279 stats->ratio <<= 8;
280 else
281 out >>= 8;
282 if (out != 0)
283 stats->ratio /= out;
284 }
285
286 /*
287 * Reset state, as on a CCP ResetReq.
288 */
289 static void
290 bsd_reset(state)
291 void *state;
292 {
293 struct bsd_db *db = (struct bsd_db *) state;
294
295 db->seqno = 0;
296 bsd_clear(db);
297 db->clear_count = 0;
298 }
299
300 /*
301 * Allocate space for a (de) compressor.
302 */
303 static void *
304 bsd_alloc(options, opt_len, decomp)
305 u_char *options;
306 int opt_len, decomp;
307 {
308 int bits;
309 u_int newlen, hsize, hshift, maxmaxcode;
310 struct bsd_db *db;
311
312 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
313 || options[1] != CILEN_BSD_COMPRESS
314 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
315 return NULL;
316 bits = BSD_NBITS(options[2]);
317 switch (bits) {
318 case 9: /* needs 82152 for both directions */
319 case 10: /* needs 84144 */
320 case 11: /* needs 88240 */
321 case 12: /* needs 96432 */
322 hsize = 5003;
323 hshift = 4;
324 break;
325 case 13: /* needs 176784 */
326 hsize = 9001;
327 hshift = 5;
328 break;
329 case 14: /* needs 353744 */
330 hsize = 18013;
331 hshift = 6;
332 break;
333 case 15: /* needs 691440 */
334 hsize = 35023;
335 hshift = 7;
336 break;
337 case 16: /* needs 1366160--far too much, */
338 /* hsize = 69001; */ /* and 69001 is too big for cptr */
339 /* hshift = 8; */ /* in struct bsd_db */
340 /* break; */
341 default:
342 return NULL;
343 }
344
345 maxmaxcode = MAXCODE(bits);
346 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
347 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
348 if (!db)
349 return NULL;
350 bzero(db, sizeof(*db) - sizeof(db->dict));
351
352 if (!decomp) {
353 db->lens = NULL;
354 } else {
355 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
356 M_DEVBUF, M_NOWAIT);
357 if (!db->lens) {
358 free(db, M_DEVBUF);
359 return NULL;
360 }
361 }
362
363 db->totlen = newlen;
364 db->hsize = hsize;
365 db->hshift = hshift;
366 db->maxmaxcode = maxmaxcode;
367 db->maxbits = bits;
368
369 return (void *) db;
370 }
371
372 static void
373 bsd_free(state)
374 void *state;
375 {
376 struct bsd_db *db = (struct bsd_db *) state;
377
378 if (db->lens)
379 free(db->lens, M_DEVBUF);
380 free(db, M_DEVBUF);
381 }
382
383 static void *
384 bsd_comp_alloc(options, opt_len)
385 u_char *options;
386 int opt_len;
387 {
388 return bsd_alloc(options, opt_len, 0);
389 }
390
391 static void *
392 bsd_decomp_alloc(options, opt_len)
393 u_char *options;
394 int opt_len;
395 {
396 return bsd_alloc(options, opt_len, 1);
397 }
398
399 /*
400 * Initialize the database.
401 */
402 static int
403 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
404 struct bsd_db *db;
405 u_char *options;
406 int opt_len, unit, hdrlen, mru, debug, decomp;
407 {
408 int i;
409
410 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
411 || options[1] != CILEN_BSD_COMPRESS
412 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
413 || BSD_NBITS(options[2]) != db->maxbits
414 || (decomp && db->lens == NULL))
415 return 0;
416
417 if (decomp) {
418 i = LAST+1;
419 while (i != 0)
420 db->lens[--i] = 1;
421 }
422 i = db->hsize;
423 while (i != 0) {
424 db->dict[--i].codem1 = BADCODEM1;
425 db->dict[i].cptr = 0;
426 }
427
428 db->unit = unit;
429 db->hdrlen = hdrlen;
430 db->mru = mru;
431 #ifndef DEBUG
432 if (debug)
433 #endif
434 db->debug = 1;
435
436 bsd_reset(db);
437
438 return 1;
439 }
440
441 static int
442 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
443 void *state;
444 u_char *options;
445 int opt_len, unit, hdrlen, debug;
446 {
447 return bsd_init((struct bsd_db *) state, options, opt_len,
448 unit, hdrlen, 0, debug, 0);
449 }
450
451 static int
452 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
453 void *state;
454 u_char *options;
455 int opt_len, unit, hdrlen, mru, debug;
456 {
457 return bsd_init((struct bsd_db *) state, options, opt_len,
458 unit, hdrlen, mru, debug, 1);
459 }
460
461
462 /*
463 * compress a packet
464 * One change from the BSD compress command is that when the
465 * code size expands, we do not output a bunch of padding.
466 */
467 int /* new slen */
468 bsd_compress(state, mret, mp, slen, maxolen)
469 void *state;
470 struct mbuf **mret; /* return compressed mbuf chain here */
471 struct mbuf *mp; /* from here */
472 int slen; /* uncompressed length */
473 int maxolen; /* max compressed length */
474 {
475 struct bsd_db *db = (struct bsd_db *) state;
476 int hshift = db->hshift;
477 u_int max_ent = db->max_ent;
478 u_int n_bits = db->n_bits;
479 u_int bitno = 32;
480 u_int32_t accm = 0, fcode;
481 struct bsd_dict *dictp;
482 u_char c;
483 int hval, disp, ent, ilen;
484 u_char *rptr, *wptr;
485 u_char *cp_end;
486 int olen;
487 struct mbuf *m;
488
489 #define PUTBYTE(v) { \
490 ++olen; \
491 if (wptr) { \
492 *wptr++ = (v); \
493 if (wptr >= cp_end) { \
494 m->m_len = wptr - mtod(m, u_char *); \
495 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
496 m = m->m_next; \
497 if (m) { \
498 m->m_len = 0; \
499 if (maxolen - olen > MLEN) \
500 MCLGET(m, M_DONTWAIT); \
501 wptr = mtod(m, u_char *); \
502 cp_end = wptr + M_TRAILINGSPACE(m); \
503 } else \
504 wptr = NULL; \
505 } \
506 } \
507 }
508
509 #define OUTPUT(ent) { \
510 bitno -= n_bits; \
511 accm |= ((ent) << bitno); \
512 do { \
513 PUTBYTE(accm >> 24); \
514 accm <<= 8; \
515 bitno += 8; \
516 } while (bitno <= 24); \
517 }
518
519 /*
520 * If the protocol is not in the range we're interested in,
521 * just return without compressing the packet. If it is,
522 * the protocol becomes the first byte to compress.
523 */
524 rptr = mtod(mp, u_char *);
525 ent = PPP_PROTOCOL(rptr);
526 if (ent < 0x21 || ent > 0xf9) {
527 *mret = NULL;
528 return slen;
529 }
530
531 /* Don't generate compressed packets which are larger than
532 the uncompressed packet. */
533 if (maxolen > slen)
534 maxolen = slen;
535
536 /* Allocate one mbuf to start with. */
537 MGET(m, M_DONTWAIT, MT_DATA);
538 *mret = m;
539 if (m != NULL) {
540 m->m_len = 0;
541 if (maxolen + db->hdrlen > MLEN)
542 MCLGET(m, M_DONTWAIT);
543 m->m_data += db->hdrlen;
544 wptr = mtod(m, u_char *);
545 cp_end = wptr + M_TRAILINGSPACE(m);
546 } else
547 wptr = cp_end = NULL;
548
549 /*
550 * Copy the PPP header over, changing the protocol,
551 * and install the 2-byte packet sequence number.
552 */
553 if (wptr) {
554 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
555 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
556 *wptr++ = 0; /* change the protocol */
557 *wptr++ = PPP_COMP;
558 *wptr++ = db->seqno >> 8;
559 *wptr++ = db->seqno;
560 }
561 ++db->seqno;
562
563 olen = 0;
564 rptr += PPP_HDRLEN;
565 slen = mp->m_len - PPP_HDRLEN;
566 ilen = slen + 1;
567 for (;;) {
568 if (slen <= 0) {
569 mp = mp->m_next;
570 if (!mp)
571 break;
572 rptr = mtod(mp, u_char *);
573 slen = mp->m_len;
574 if (!slen)
575 continue; /* handle 0-length buffers */
576 ilen += slen;
577 }
578
579 slen--;
580 c = *rptr++;
581 fcode = BSD_KEY(ent, c);
582 hval = BSD_HASH(ent, c, hshift);
583 dictp = &db->dict[hval];
584
585 /* Validate and then check the entry. */
586 if (dictp->codem1 >= max_ent)
587 goto nomatch;
588 if (dictp->f.fcode == fcode) {
589 ent = dictp->codem1+1;
590 continue; /* found (prefix,suffix) */
591 }
592
593 /* continue probing until a match or invalid entry */
594 disp = (hval == 0) ? 1 : hval;
595 do {
596 hval += disp;
597 if (hval >= db->hsize)
598 hval -= db->hsize;
599 dictp = &db->dict[hval];
600 if (dictp->codem1 >= max_ent)
601 goto nomatch;
602 } while (dictp->f.fcode != fcode);
603 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
604 continue;
605
606 nomatch:
607 OUTPUT(ent); /* output the prefix */
608
609 /* code -> hashtable */
610 if (max_ent < db->maxmaxcode) {
611 struct bsd_dict *dictp2;
612 /* expand code size if needed */
613 if (max_ent >= MAXCODE(n_bits))
614 db->n_bits = ++n_bits;
615
616 /* Invalidate old hash table entry using
617 * this code, and then take it over.
618 */
619 dictp2 = &db->dict[max_ent+1];
620 if (db->dict[dictp2->cptr].codem1 == max_ent)
621 db->dict[dictp2->cptr].codem1 = BADCODEM1;
622 dictp2->cptr = hval;
623 dictp->codem1 = max_ent;
624 dictp->f.fcode = fcode;
625
626 db->max_ent = ++max_ent;
627 }
628 ent = c;
629 }
630
631 OUTPUT(ent); /* output the last code */
632 db->bytes_out += olen;
633 db->in_count += ilen;
634 if (bitno < 32)
635 ++db->bytes_out; /* count complete bytes */
636
637 if (bsd_check(db))
638 OUTPUT(CLEAR); /* do not count the CLEAR */
639
640 /*
641 * Pad dribble bits of last code with ones.
642 * Do not emit a completely useless byte of ones.
643 */
644 if (bitno != 32)
645 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
646
647 if (m != NULL) {
648 m->m_len = wptr - mtod(m, u_char *);
649 m->m_next = NULL;
650 }
651
652 /*
653 * Increase code size if we would have without the packet
654 * boundary and as the decompressor will.
655 */
656 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
657 db->n_bits++;
658
659 db->uncomp_bytes += ilen;
660 ++db->uncomp_count;
661 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
662 /* throw away the compressed stuff if it is longer than uncompressed */
663 if (*mret != NULL) {
664 m_freem(*mret);
665 *mret = NULL;
666 }
667 ++db->incomp_count;
668 db->incomp_bytes += ilen;
669 } else {
670 ++db->comp_count;
671 db->comp_bytes += olen + BSD_OVHD;
672 }
673
674 return olen + PPP_HDRLEN + BSD_OVHD;
675 #undef OUTPUT
676 #undef PUTBYTE
677 }
678
679
680 /*
681 * Update the "BSD Compress" dictionary on the receiver for
682 * incompressible data by pretending to compress the incoming data.
683 */
684 static void
685 bsd_incomp(state, dmsg)
686 void *state;
687 struct mbuf *dmsg;
688 {
689 struct bsd_db *db = (struct bsd_db *) state;
690 u_int hshift = db->hshift;
691 u_int max_ent = db->max_ent;
692 u_int n_bits = db->n_bits;
693 struct bsd_dict *dictp;
694 u_int32_t fcode;
695 u_char c;
696 u_int32_t hval, disp;
697 int slen, ilen;
698 u_int bitno = 7;
699 u_char *rptr;
700 u_int ent;
701
702 /*
703 * If the protocol is not in the range we're interested in,
704 * just return without looking at the packet. If it is,
705 * the protocol becomes the first byte to "compress".
706 */
707 rptr = mtod(dmsg, u_char *);
708 ent = PPP_PROTOCOL(rptr);
709 if (ent < 0x21 || ent > 0xf9)
710 return;
711
712 db->seqno++;
713 ilen = 1; /* count the protocol as 1 byte */
714 rptr += PPP_HDRLEN;
715 slen = dmsg->m_len - PPP_HDRLEN;
716 for (;;) {
717 if (slen <= 0) {
718 dmsg = dmsg->m_next;
719 if (!dmsg)
720 break;
721 rptr = mtod(dmsg, u_char *);
722 slen = dmsg->m_len;
723 continue;
724 }
725 ilen += slen;
726
727 do {
728 c = *rptr++;
729 fcode = BSD_KEY(ent, c);
730 hval = BSD_HASH(ent, c, hshift);
731 dictp = &db->dict[hval];
732
733 /* validate and then check the entry */
734 if (dictp->codem1 >= max_ent)
735 goto nomatch;
736 if (dictp->f.fcode == fcode) {
737 ent = dictp->codem1+1;
738 continue; /* found (prefix,suffix) */
739 }
740
741 /* continue probing until a match or invalid entry */
742 disp = (hval == 0) ? 1 : hval;
743 do {
744 hval += disp;
745 if (hval >= db->hsize)
746 hval -= db->hsize;
747 dictp = &db->dict[hval];
748 if (dictp->codem1 >= max_ent)
749 goto nomatch;
750 } while (dictp->f.fcode != fcode);
751 ent = dictp->codem1+1;
752 continue; /* finally found (prefix,suffix) */
753
754 nomatch: /* output (count) the prefix */
755 bitno += n_bits;
756
757 /* code -> hashtable */
758 if (max_ent < db->maxmaxcode) {
759 struct bsd_dict *dictp2;
760 /* expand code size if needed */
761 if (max_ent >= MAXCODE(n_bits))
762 db->n_bits = ++n_bits;
763
764 /* Invalidate previous hash table entry
765 * assigned this code, and then take it over.
766 */
767 dictp2 = &db->dict[max_ent+1];
768 if (db->dict[dictp2->cptr].codem1 == max_ent)
769 db->dict[dictp2->cptr].codem1 = BADCODEM1;
770 dictp2->cptr = hval;
771 dictp->codem1 = max_ent;
772 dictp->f.fcode = fcode;
773
774 db->max_ent = ++max_ent;
775 db->lens[max_ent] = db->lens[ent]+1;
776 }
777 ent = c;
778 } while (--slen != 0);
779 }
780 bitno += n_bits; /* output (count) the last code */
781 db->bytes_out += bitno/8;
782 db->in_count += ilen;
783 (void)bsd_check(db);
784
785 ++db->incomp_count;
786 db->incomp_bytes += ilen;
787 ++db->uncomp_count;
788 db->uncomp_bytes += ilen;
789
790 /* Increase code size if we would have without the packet
791 * boundary and as the decompressor will.
792 */
793 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
794 db->n_bits++;
795 }
796
797
798 /*
799 * Decompress "BSD Compress".
800 *
801 * Because of patent problems, we return DECOMP_ERROR for errors
802 * found by inspecting the input data and for system problems, but
803 * DECOMP_FATALERROR for any errors which could possibly be said to
804 * be being detected "after" decompression. For DECOMP_ERROR,
805 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
806 * infringing a patent of Motorola's if we do, so we take CCP down
807 * instead.
808 *
809 * Given that the frame has the correct sequence number and a good FCS,
810 * errors such as invalid codes in the input most likely indicate a
811 * bug, so we return DECOMP_FATALERROR for them in order to turn off
812 * compression, even though they are detected by inspecting the input.
813 */
814 int
815 bsd_decompress(state, cmp, dmpp)
816 void *state;
817 struct mbuf *cmp, **dmpp;
818 {
819 struct bsd_db *db = (struct bsd_db *) state;
820 u_int max_ent = db->max_ent;
821 u_int32_t accm = 0;
822 u_int bitno = 32; /* 1st valid bit in accm */
823 u_int n_bits = db->n_bits;
824 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
825 struct bsd_dict *dictp;
826 int explen, i, seq, len;
827 u_int incode, oldcode, finchar;
828 u_char *p, *rptr, *wptr;
829 struct mbuf *m, *dmp, *mret;
830 int adrs, ctrl, ilen;
831 int space, codelen, extra;
832
833 /*
834 * Save the address/control from the PPP header
835 * and then get the sequence number.
836 */
837 *dmpp = NULL;
838 rptr = mtod(cmp, u_char *);
839 adrs = PPP_ADDRESS(rptr);
840 ctrl = PPP_CONTROL(rptr);
841 rptr += PPP_HDRLEN;
842 len = cmp->m_len - PPP_HDRLEN;
843 seq = 0;
844 for (i = 0; i < 2; ++i) {
845 while (len <= 0) {
846 cmp = cmp->m_next;
847 if (cmp == NULL)
848 return DECOMP_ERROR;
849 rptr = mtod(cmp, u_char *);
850 len = cmp->m_len;
851 }
852 seq = (seq << 8) + *rptr++;
853 --len;
854 }
855
856 /*
857 * Check the sequence number and give up if it differs from
858 * the value we're expecting.
859 */
860 if (seq != db->seqno) {
861 if (db->debug)
862 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
863 db->unit, seq, db->seqno - 1);
864 return DECOMP_ERROR;
865 }
866 ++db->seqno;
867
868 /*
869 * Allocate one mbuf to start with.
870 */
871 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
872 if (dmp == NULL)
873 return DECOMP_ERROR;
874 mret = dmp;
875 dmp->m_len = 0;
876 dmp->m_next = NULL;
877 MCLGET(dmp, M_DONTWAIT);
878 dmp->m_data += db->hdrlen;
879 wptr = mtod(dmp, u_char *);
880 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
881
882 /*
883 * Fill in the ppp header, but not the last byte of the protocol
884 * (that comes from the decompressed data).
885 */
886 wptr[0] = adrs;
887 wptr[1] = ctrl;
888 wptr[2] = 0;
889 wptr += PPP_HDRLEN - 1;
890
891 ilen = len;
892 oldcode = CLEAR;
893 explen = 0;
894 for (;;) {
895 if (len == 0) {
896 cmp = cmp->m_next;
897 if (!cmp) /* quit at end of message */
898 break;
899 rptr = mtod(cmp, u_char *);
900 len = cmp->m_len;
901 ilen += len;
902 continue; /* handle 0-length buffers */
903 }
904
905 /*
906 * Accumulate bytes until we have a complete code.
907 * Then get the next code, relying on the 32-bit,
908 * unsigned accm to mask the result.
909 */
910 bitno -= 8;
911 accm |= *rptr++ << bitno;
912 --len;
913 if (tgtbitno < bitno)
914 continue;
915 incode = accm >> tgtbitno;
916 accm <<= n_bits;
917 bitno += n_bits;
918
919 if (incode == CLEAR) {
920 /*
921 * The dictionary must only be cleared at
922 * the end of a packet. But there could be an
923 * empty mbuf at the end.
924 */
925 if (len > 0 || cmp->m_next != NULL) {
926 while ((cmp = cmp->m_next) != NULL)
927 len += cmp->m_len;
928 if (len > 0) {
929 m_freem(mret);
930 if (db->debug)
931 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
932 return DECOMP_FATALERROR; /* probably a bug */
933 }
934 }
935 bsd_clear(db);
936 explen = ilen = 0;
937 break;
938 }
939
940 if (incode > max_ent + 2 || incode > db->maxmaxcode
941 || (incode > max_ent && oldcode == CLEAR)) {
942 m_freem(mret);
943 if (db->debug) {
944 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
945 db->unit, incode, oldcode);
946 printf("max_ent=0x%x explen=%d seqno=%d\n",
947 max_ent, explen, db->seqno);
948 }
949 return DECOMP_FATALERROR; /* probably a bug */
950 }
951
952 /* Special case for KwKwK string. */
953 if (incode > max_ent) {
954 finchar = oldcode;
955 extra = 1;
956 } else {
957 finchar = incode;
958 extra = 0;
959 }
960
961 codelen = db->lens[finchar];
962 explen += codelen + extra;
963 if (explen > db->mru + 1) {
964 m_freem(mret);
965 if (db->debug) {
966 printf("bsd_decomp%d: ran out of mru\n", db->unit);
967 #ifdef DEBUG
968 while ((cmp = cmp->m_next) != NULL)
969 len += cmp->m_len;
970 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
971 len, finchar, codelen, explen);
972 #endif
973 }
974 return DECOMP_FATALERROR;
975 }
976
977 /*
978 * For simplicity, the decoded characters go in a single mbuf,
979 * so we allocate a single extra cluster mbuf if necessary.
980 */
981 if ((space -= codelen + extra) < 0) {
982 dmp->m_len = wptr - mtod(dmp, u_char *);
983 MGET(m, M_DONTWAIT, MT_DATA);
984 if (m == NULL) {
985 m_freem(mret);
986 return DECOMP_ERROR;
987 }
988 m->m_len = 0;
989 m->m_next = NULL;
990 dmp->m_next = m;
991 MCLGET(m, M_DONTWAIT);
992 space = M_TRAILINGSPACE(m) - (codelen + extra);
993 if (space < 0) {
994 /* now that's what I call *compression*. */
995 m_freem(mret);
996 return DECOMP_ERROR;
997 }
998 dmp = m;
999 wptr = mtod(dmp, u_char *);
1000 }
1001
1002 /*
1003 * Decode this code and install it in the decompressed buffer.
1004 */
1005 p = (wptr += codelen);
1006 while (finchar > LAST) {
1007 dictp = &db->dict[db->dict[finchar].cptr];
1008 #ifdef DEBUG
1009 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1010 goto bad;
1011 #endif
1012 *--p = dictp->f.hs.suffix;
1013 finchar = dictp->f.hs.prefix;
1014 }
1015 *--p = finchar;
1016
1017 #ifdef DEBUG
1018 if (--codelen != 0)
1019 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1020 db->unit, codelen, incode, max_ent);
1021 #endif
1022
1023 if (extra) /* the KwKwK case again */
1024 *wptr++ = finchar;
1025
1026 /*
1027 * If not first code in a packet, and
1028 * if not out of code space, then allocate a new code.
1029 *
1030 * Keep the hash table correct so it can be used
1031 * with uncompressed packets.
1032 */
1033 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1034 struct bsd_dict *dictp2;
1035 u_int32_t fcode;
1036 u_int32_t hval, disp;
1037
1038 fcode = BSD_KEY(oldcode,finchar);
1039 hval = BSD_HASH(oldcode,finchar,db->hshift);
1040 dictp = &db->dict[hval];
1041
1042 /* look for a free hash table entry */
1043 if (dictp->codem1 < max_ent) {
1044 disp = (hval == 0) ? 1 : hval;
1045 do {
1046 hval += disp;
1047 if (hval >= db->hsize)
1048 hval -= db->hsize;
1049 dictp = &db->dict[hval];
1050 } while (dictp->codem1 < max_ent);
1051 }
1052
1053 /*
1054 * Invalidate previous hash table entry
1055 * assigned this code, and then take it over
1056 */
1057 dictp2 = &db->dict[max_ent+1];
1058 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1059 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1060 }
1061 dictp2->cptr = hval;
1062 dictp->codem1 = max_ent;
1063 dictp->f.fcode = fcode;
1064
1065 db->max_ent = ++max_ent;
1066 db->lens[max_ent] = db->lens[oldcode]+1;
1067
1068 /* Expand code size if needed. */
1069 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1070 db->n_bits = ++n_bits;
1071 tgtbitno = 32-n_bits;
1072 }
1073 }
1074 oldcode = incode;
1075 }
1076 dmp->m_len = wptr - mtod(dmp, u_char *);
1077
1078 /*
1079 * Keep the checkpoint right so that incompressible packets
1080 * clear the dictionary at the right times.
1081 */
1082 db->bytes_out += ilen;
1083 db->in_count += explen;
1084 if (bsd_check(db) && db->debug) {
1085 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1086 db->unit);
1087 }
1088
1089 ++db->comp_count;
1090 db->comp_bytes += ilen + BSD_OVHD;
1091 ++db->uncomp_count;
1092 db->uncomp_bytes += explen;
1093
1094 *dmpp = mret;
1095 return DECOMP_OK;
1096
1097 #ifdef DEBUG
1098 bad:
1099 if (codelen <= 0) {
1100 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1101 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1102 incode, finchar, db->dict[finchar].cptr, max_ent);
1103 } else if (dictp->codem1 != finchar-1) {
1104 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1105 db->unit, incode, finchar);
1106 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1107 db->dict[finchar].cptr, dictp->codem1);
1108 }
1109 m_freem(mret);
1110 return DECOMP_FATALERROR;
1111 #endif /* DEBUG */
1112 }
1113 #endif /* DO_BSD_COMPRESS */
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