FreeBSD/Linux Kernel Cross Reference
sys/net/bsd-comp.c
1 /* $NetBSD: bsd-comp.c,v 1.12 2003/08/07 16:32:48 agc Exp $ */
2 /* Id: bsd-comp.c,v 1.6 1996/08/28 06:31:58 paulus Exp */
3
4 /* Because this code is derived from the 4.3BSD compress source:
5 *
6 *
7 * Copyright (c) 1985, 1986 The Regents of the University of California.
8 * All rights reserved.
9 *
10 * This code is derived from software contributed to Berkeley by
11 * James A. Woods, derived from original work by Spencer Thomas
12 * and Joseph Orost.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 * 3. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38
39 /*
40 * This version is for use with mbufs on BSD-derived systems.
41 */
42
43 #include <sys/cdefs.h>
44 __KERNEL_RCSID(0, "$NetBSD: bsd-comp.c,v 1.12 2003/08/07 16:32:48 agc Exp $");
45
46 #include <sys/param.h>
47 #include <sys/systm.h>
48 #include <sys/mbuf.h>
49 #include <sys/socket.h>
50 #include <net/if.h>
51 #include <net/if_types.h>
52 #include <net/ppp_defs.h>
53 #include <net/if_ppp.h>
54
55 #define PACKETPTR struct mbuf *
56 #include <net/ppp-comp.h>
57
58 #if DO_BSD_COMPRESS
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_comp_alloc __P((u_char *options, int opt_len));
133 static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
134 static void bsd_free __P((void *state));
135 static int bsd_comp_init __P((void *state, u_char *options, int opt_len,
136 int unit, int hdrlen, int debug));
137 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
138 int unit, int hdrlen, int mru, int debug));
139 static int bsd_compress __P((void *state, struct mbuf **mret,
140 struct mbuf *mp, int slen, int maxolen));
141 static void bsd_incomp __P((void *state, struct mbuf *dmsg));
142 static int bsd_decompress __P((void *state, struct mbuf *cmp,
143 struct mbuf **dmpp));
144 static void bsd_reset __P((void *state));
145 static void bsd_comp_stats __P((void *state, struct compstat *stats));
146
147 /*
148 * Procedures exported to if_ppp.c.
149 */
150 struct compressor ppp_bsd_compress = {
151 CI_BSD_COMPRESS, /* compress_proto */
152 bsd_comp_alloc, /* comp_alloc */
153 bsd_free, /* comp_free */
154 bsd_comp_init, /* comp_init */
155 bsd_reset, /* comp_reset */
156 bsd_compress, /* compress */
157 bsd_comp_stats, /* comp_stat */
158 bsd_decomp_alloc, /* decomp_alloc */
159 bsd_free, /* decomp_free */
160 bsd_decomp_init, /* decomp_init */
161 bsd_reset, /* decomp_reset */
162 bsd_decompress, /* decompress */
163 bsd_incomp, /* incomp */
164 bsd_comp_stats, /* decomp_stat */
165 };
166
167 /*
168 * the next two codes should not be changed lightly, as they must not
169 * lie within the contiguous general code space.
170 */
171 #define CLEAR 256 /* table clear output code */
172 #define FIRST 257 /* first free entry */
173 #define LAST 255
174
175 #define MAXCODE(b) ((1 << (b)) - 1)
176 #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
177
178 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
179 ^ (u_int32_t)(prefix))
180 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
181 + (u_int32_t)(prefix))
182
183 #define CHECK_GAP 10000 /* Ratio check interval */
184
185 #define RATIO_SCALE_LOG 8
186 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
187 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
188
189 static void bsd_clear __P((struct bsd_db *));
190 static int bsd_check __P((struct bsd_db *));
191 static void *bsd_alloc __P((u_char *, int, int));
192 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int,
193 int, int));
194
195 /*
196 * clear the dictionary
197 */
198 static void
199 bsd_clear(db)
200 struct bsd_db *db;
201 {
202 db->clear_count++;
203 db->max_ent = FIRST-1;
204 db->n_bits = BSD_INIT_BITS;
205 db->ratio = 0;
206 db->bytes_out = 0;
207 db->in_count = 0;
208 db->checkpoint = CHECK_GAP;
209 }
210
211 /*
212 * If the dictionary is full, then see if it is time to reset it.
213 *
214 * Compute the compression ratio using fixed-point arithmetic
215 * with 8 fractional bits.
216 *
217 * Since we have an infinite stream instead of a single file,
218 * watch only the local compression ratio.
219 *
220 * Since both peers must reset the dictionary at the same time even in
221 * the absence of CLEAR codes (while packets are incompressible), they
222 * must compute the same ratio.
223 */
224 static int /* 1=output CLEAR */
225 bsd_check(db)
226 struct bsd_db *db;
227 {
228 u_int new_ratio;
229
230 if (db->in_count >= db->checkpoint) {
231 /* age the ratio by limiting the size of the counts */
232 if (db->in_count >= RATIO_MAX
233 || db->bytes_out >= RATIO_MAX) {
234 db->in_count -= db->in_count/4;
235 db->bytes_out -= db->bytes_out/4;
236 }
237
238 db->checkpoint = db->in_count + CHECK_GAP;
239
240 if (db->max_ent >= db->maxmaxcode) {
241 /* Reset the dictionary only if the ratio is worse,
242 * or if it looks as if it has been poisoned
243 * by incompressible data.
244 *
245 * This does not overflow, because
246 * db->in_count <= RATIO_MAX.
247 */
248 new_ratio = db->in_count << RATIO_SCALE_LOG;
249 if (db->bytes_out != 0)
250 new_ratio /= db->bytes_out;
251
252 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
253 bsd_clear(db);
254 return 1;
255 }
256 db->ratio = new_ratio;
257 }
258 }
259 return 0;
260 }
261
262 /*
263 * Return statistics.
264 */
265 static void
266 bsd_comp_stats(state, stats)
267 void *state;
268 struct compstat *stats;
269 {
270 struct bsd_db *db = (struct bsd_db *) state;
271 u_int out;
272
273 stats->unc_bytes = db->uncomp_bytes;
274 stats->unc_packets = db->uncomp_count;
275 stats->comp_bytes = db->comp_bytes;
276 stats->comp_packets = db->comp_count;
277 stats->inc_bytes = db->incomp_bytes;
278 stats->inc_packets = db->incomp_count;
279 stats->ratio = db->in_count;
280 out = db->bytes_out;
281 if (stats->ratio <= 0x7fffff)
282 stats->ratio <<= 8;
283 else
284 out >>= 8;
285 if (out != 0)
286 stats->ratio /= out;
287 }
288
289 /*
290 * Reset state, as on a CCP ResetReq.
291 */
292 static void
293 bsd_reset(state)
294 void *state;
295 {
296 struct bsd_db *db = (struct bsd_db *) state;
297
298 db->seqno = 0;
299 bsd_clear(db);
300 db->clear_count = 0;
301 }
302
303 /*
304 * Allocate space for a (de) compressor.
305 */
306 static void *
307 bsd_alloc(options, opt_len, decomp)
308 u_char *options;
309 int opt_len, decomp;
310 {
311 int bits;
312 u_int newlen, hsize, hshift, maxmaxcode;
313 struct bsd_db *db;
314
315 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
316 || options[1] != CILEN_BSD_COMPRESS
317 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
318 return NULL;
319 bits = BSD_NBITS(options[2]);
320 switch (bits) {
321 case 9: /* needs 82152 for both directions */
322 case 10: /* needs 84144 */
323 case 11: /* needs 88240 */
324 case 12: /* needs 96432 */
325 hsize = 5003;
326 hshift = 4;
327 break;
328 case 13: /* needs 176784 */
329 hsize = 9001;
330 hshift = 5;
331 break;
332 case 14: /* needs 353744 */
333 hsize = 18013;
334 hshift = 6;
335 break;
336 case 15: /* needs 691440 */
337 hsize = 35023;
338 hshift = 7;
339 break;
340 case 16: /* needs 1366160--far too much, */
341 /* hsize = 69001; */ /* and 69001 is too big for cptr */
342 /* hshift = 8; */ /* in struct bsd_db */
343 /* break; */
344 default:
345 return NULL;
346 }
347
348 maxmaxcode = MAXCODE(bits);
349 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
350 db = malloc(newlen, M_DEVBUF, M_NOWAIT);
351 if (!db)
352 return NULL;
353 memset(db, 0, sizeof(*db) - sizeof(db->dict));
354
355 if (!decomp) {
356 db->lens = NULL;
357 } else {
358 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]),
359 M_DEVBUF, M_NOWAIT);
360 if (!db->lens) {
361 free(db, M_DEVBUF);
362 return NULL;
363 }
364 }
365
366 db->totlen = newlen;
367 db->hsize = hsize;
368 db->hshift = hshift;
369 db->maxmaxcode = maxmaxcode;
370 db->maxbits = bits;
371
372 return (void *) db;
373 }
374
375 static void
376 bsd_free(state)
377 void *state;
378 {
379 struct bsd_db *db = (struct bsd_db *) state;
380
381 if (db->lens)
382 free(db->lens, M_DEVBUF);
383 free(db, M_DEVBUF);
384 }
385
386 static void *
387 bsd_comp_alloc(options, opt_len)
388 u_char *options;
389 int opt_len;
390 {
391 return bsd_alloc(options, opt_len, 0);
392 }
393
394 static void *
395 bsd_decomp_alloc(options, opt_len)
396 u_char *options;
397 int opt_len;
398 {
399 return bsd_alloc(options, opt_len, 1);
400 }
401
402 /*
403 * Initialize the database.
404 */
405 static int
406 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
407 struct bsd_db *db;
408 u_char *options;
409 int opt_len, unit, hdrlen, mru, debug, decomp;
410 {
411 int i;
412
413 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
414 || options[1] != CILEN_BSD_COMPRESS
415 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
416 || BSD_NBITS(options[2]) != db->maxbits
417 || (decomp && db->lens == NULL))
418 return 0;
419
420 if (decomp) {
421 i = LAST+1;
422 while (i != 0)
423 db->lens[--i] = 1;
424 }
425 i = db->hsize;
426 while (i != 0) {
427 db->dict[--i].codem1 = BADCODEM1;
428 db->dict[i].cptr = 0;
429 }
430
431 db->unit = unit;
432 db->hdrlen = hdrlen;
433 db->mru = mru;
434 #ifndef DEBUG
435 if (debug)
436 #endif
437 db->debug = 1;
438
439 bsd_reset(db);
440
441 return 1;
442 }
443
444 static int
445 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
446 void *state;
447 u_char *options;
448 int opt_len, unit, hdrlen, debug;
449 {
450 return bsd_init((struct bsd_db *) state, options, opt_len,
451 unit, hdrlen, 0, debug, 0);
452 }
453
454 static int
455 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
456 void *state;
457 u_char *options;
458 int opt_len, unit, hdrlen, mru, debug;
459 {
460 return bsd_init((struct bsd_db *) state, options, opt_len,
461 unit, hdrlen, mru, debug, 1);
462 }
463
464
465 /*
466 * compress a packet
467 * One change from the BSD compress command is that when the
468 * code size expands, we do not output a bunch of padding.
469 */
470 int /* new slen */
471 bsd_compress(state, mret, mp, slen, maxolen)
472 void *state;
473 struct mbuf **mret; /* return compressed mbuf chain here */
474 struct mbuf *mp; /* from here */
475 int slen; /* uncompressed length */
476 int maxolen; /* max compressed length */
477 {
478 struct bsd_db *db = (struct bsd_db *) state;
479 int hshift = db->hshift;
480 u_int max_ent = db->max_ent;
481 u_int n_bits = db->n_bits;
482 u_int bitno = 32;
483 u_int32_t accm = 0, fcode;
484 struct bsd_dict *dictp;
485 u_char c;
486 int hval, disp, ent, ilen;
487 u_char *rptr, *wptr;
488 u_char *cp_end;
489 int olen;
490 struct mbuf *m;
491
492 #define PUTBYTE(v) { \
493 ++olen; \
494 if (wptr) { \
495 *wptr++ = (v); \
496 if (wptr >= cp_end) { \
497 m->m_len = wptr - mtod(m, u_char *); \
498 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
499 m = m->m_next; \
500 if (m) { \
501 m->m_len = 0; \
502 if (maxolen - olen > MLEN) \
503 MCLGET(m, M_DONTWAIT); \
504 wptr = mtod(m, u_char *); \
505 cp_end = wptr + M_TRAILINGSPACE(m); \
506 } else \
507 wptr = NULL; \
508 } \
509 } \
510 }
511
512 #define OUTPUT(ent) { \
513 bitno -= n_bits; \
514 accm |= ((ent) << bitno); \
515 do { \
516 PUTBYTE(accm >> 24); \
517 accm <<= 8; \
518 bitno += 8; \
519 } while (bitno <= 24); \
520 }
521
522 /*
523 * If the protocol is not in the range we're interested in,
524 * just return without compressing the packet. If it is,
525 * the protocol becomes the first byte to compress.
526 */
527 rptr = mtod(mp, u_char *);
528 ent = PPP_PROTOCOL(rptr);
529 if (ent < 0x21 || ent > 0xf9) {
530 *mret = NULL;
531 return slen;
532 }
533
534 /* Don't generate compressed packets which are larger than
535 the uncompressed packet. */
536 if (maxolen > slen)
537 maxolen = slen;
538
539 /* Allocate one mbuf to start with. */
540 MGET(m, M_DONTWAIT, MT_DATA);
541 *mret = m;
542 if (m != NULL) {
543 m->m_len = 0;
544 if (maxolen + db->hdrlen > MLEN)
545 MCLGET(m, M_DONTWAIT);
546 m->m_data += db->hdrlen;
547 wptr = mtod(m, u_char *);
548 cp_end = wptr + M_TRAILINGSPACE(m);
549 } else
550 wptr = cp_end = NULL;
551
552 /*
553 * Copy the PPP header over, changing the protocol,
554 * and install the 2-byte packet sequence number.
555 */
556 if (wptr) {
557 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
558 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
559 *wptr++ = 0; /* change the protocol */
560 *wptr++ = PPP_COMP;
561 *wptr++ = db->seqno >> 8;
562 *wptr++ = db->seqno;
563 }
564 ++db->seqno;
565
566 olen = 0;
567 rptr += PPP_HDRLEN;
568 slen = mp->m_len - PPP_HDRLEN;
569 ilen = slen + 1;
570 for (;;) {
571 if (slen <= 0) {
572 mp = mp->m_next;
573 if (!mp)
574 break;
575 rptr = mtod(mp, u_char *);
576 slen = mp->m_len;
577 if (!slen)
578 continue; /* handle 0-length buffers */
579 ilen += slen;
580 }
581
582 slen--;
583 c = *rptr++;
584 fcode = BSD_KEY(ent, c);
585 hval = BSD_HASH(ent, c, hshift);
586 dictp = &db->dict[hval];
587
588 /* Validate and then check the entry. */
589 if (dictp->codem1 >= max_ent)
590 goto nomatch;
591 if (dictp->f.fcode == fcode) {
592 ent = dictp->codem1+1;
593 continue; /* found (prefix,suffix) */
594 }
595
596 /* continue probing until a match or invalid entry */
597 disp = (hval == 0) ? 1 : hval;
598 do {
599 hval += disp;
600 if (hval >= db->hsize)
601 hval -= db->hsize;
602 dictp = &db->dict[hval];
603 if (dictp->codem1 >= max_ent)
604 goto nomatch;
605 } while (dictp->f.fcode != fcode);
606 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
607 continue;
608
609 nomatch:
610 OUTPUT(ent); /* output the prefix */
611
612 /* code -> hashtable */
613 if (max_ent < db->maxmaxcode) {
614 struct bsd_dict *dictp2;
615 /* expand code size if needed */
616 if (max_ent >= MAXCODE(n_bits))
617 db->n_bits = ++n_bits;
618
619 /* Invalidate old hash table entry using
620 * this code, and then take it over.
621 */
622 dictp2 = &db->dict[max_ent+1];
623 if (db->dict[dictp2->cptr].codem1 == max_ent)
624 db->dict[dictp2->cptr].codem1 = BADCODEM1;
625 dictp2->cptr = hval;
626 dictp->codem1 = max_ent;
627 dictp->f.fcode = fcode;
628
629 db->max_ent = ++max_ent;
630 }
631 ent = c;
632 }
633
634 OUTPUT(ent); /* output the last code */
635 db->bytes_out += olen;
636 db->in_count += ilen;
637 if (bitno < 32)
638 ++db->bytes_out; /* count complete bytes */
639
640 if (bsd_check(db))
641 OUTPUT(CLEAR); /* do not count the CLEAR */
642
643 /*
644 * Pad dribble bits of last code with ones.
645 * Do not emit a completely useless byte of ones.
646 */
647 if (bitno != 32)
648 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
649
650 if (m != NULL) {
651 m->m_len = wptr - mtod(m, u_char *);
652 m->m_next = NULL;
653 }
654
655 /*
656 * Increase code size if we would have without the packet
657 * boundary and as the decompressor will.
658 */
659 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
660 db->n_bits++;
661
662 db->uncomp_bytes += ilen;
663 ++db->uncomp_count;
664 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
665 /* throw away the compressed stuff if it is longer than uncompressed */
666 if (*mret != NULL) {
667 m_freem(*mret);
668 *mret = NULL;
669 }
670 ++db->incomp_count;
671 db->incomp_bytes += ilen;
672 } else {
673 ++db->comp_count;
674 db->comp_bytes += olen + BSD_OVHD;
675 }
676
677 return olen + PPP_HDRLEN + BSD_OVHD;
678 #undef OUTPUT
679 #undef PUTBYTE
680 }
681
682
683 /*
684 * Update the "BSD Compress" dictionary on the receiver for
685 * incompressible data by pretending to compress the incoming data.
686 */
687 static void
688 bsd_incomp(state, dmsg)
689 void *state;
690 struct mbuf *dmsg;
691 {
692 struct bsd_db *db = (struct bsd_db *) state;
693 u_int hshift = db->hshift;
694 u_int max_ent = db->max_ent;
695 u_int n_bits = db->n_bits;
696 struct bsd_dict *dictp;
697 u_int32_t fcode;
698 u_char c;
699 u_int32_t hval, disp;
700 int slen, ilen;
701 u_int bitno = 7;
702 u_char *rptr;
703 u_int ent;
704
705 /*
706 * If the protocol is not in the range we're interested in,
707 * just return without looking at the packet. If it is,
708 * the protocol becomes the first byte to "compress".
709 */
710 rptr = mtod(dmsg, u_char *);
711 ent = PPP_PROTOCOL(rptr);
712 if (ent < 0x21 || ent > 0xf9)
713 return;
714
715 db->seqno++;
716 ilen = 1; /* count the protocol as 1 byte */
717 rptr += PPP_HDRLEN;
718 slen = dmsg->m_len - PPP_HDRLEN;
719 for (;;) {
720 if (slen <= 0) {
721 dmsg = dmsg->m_next;
722 if (!dmsg)
723 break;
724 rptr = mtod(dmsg, u_char *);
725 slen = dmsg->m_len;
726 continue;
727 }
728 ilen += slen;
729
730 do {
731 c = *rptr++;
732 fcode = BSD_KEY(ent, c);
733 hval = BSD_HASH(ent, c, hshift);
734 dictp = &db->dict[hval];
735
736 /* validate and then check the entry */
737 if (dictp->codem1 >= max_ent)
738 goto nomatch;
739 if (dictp->f.fcode == fcode) {
740 ent = dictp->codem1+1;
741 continue; /* found (prefix,suffix) */
742 }
743
744 /* continue probing until a match or invalid entry */
745 disp = (hval == 0) ? 1 : hval;
746 do {
747 hval += disp;
748 if (hval >= db->hsize)
749 hval -= db->hsize;
750 dictp = &db->dict[hval];
751 if (dictp->codem1 >= max_ent)
752 goto nomatch;
753 } while (dictp->f.fcode != fcode);
754 ent = dictp->codem1+1;
755 continue; /* finally found (prefix,suffix) */
756
757 nomatch: /* output (count) the prefix */
758 bitno += n_bits;
759
760 /* code -> hashtable */
761 if (max_ent < db->maxmaxcode) {
762 struct bsd_dict *dictp2;
763 /* expand code size if needed */
764 if (max_ent >= MAXCODE(n_bits))
765 db->n_bits = ++n_bits;
766
767 /* Invalidate previous hash table entry
768 * assigned this code, and then take it over.
769 */
770 dictp2 = &db->dict[max_ent+1];
771 if (db->dict[dictp2->cptr].codem1 == max_ent)
772 db->dict[dictp2->cptr].codem1 = BADCODEM1;
773 dictp2->cptr = hval;
774 dictp->codem1 = max_ent;
775 dictp->f.fcode = fcode;
776
777 db->max_ent = ++max_ent;
778 db->lens[max_ent] = db->lens[ent]+1;
779 }
780 ent = c;
781 } while (--slen != 0);
782 }
783 bitno += n_bits; /* output (count) the last code */
784 db->bytes_out += bitno/8;
785 db->in_count += ilen;
786 (void)bsd_check(db);
787
788 ++db->incomp_count;
789 db->incomp_bytes += ilen;
790 ++db->uncomp_count;
791 db->uncomp_bytes += ilen;
792
793 /* Increase code size if we would have without the packet
794 * boundary and as the decompressor will.
795 */
796 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
797 db->n_bits++;
798 }
799
800
801 /*
802 * Decompress "BSD Compress".
803 *
804 * Because of patent problems, we return DECOMP_ERROR for errors
805 * found by inspecting the input data and for system problems, but
806 * DECOMP_FATALERROR for any errors which could possibly be said to
807 * be being detected "after" decompression. For DECOMP_ERROR,
808 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
809 * infringing a patent of Motorola's if we do, so we take CCP down
810 * instead.
811 *
812 * Given that the frame has the correct sequence number and a good FCS,
813 * errors such as invalid codes in the input most likely indicate a
814 * bug, so we return DECOMP_FATALERROR for them in order to turn off
815 * compression, even though they are detected by inspecting the input.
816 */
817 int
818 bsd_decompress(state, cmp, dmpp)
819 void *state;
820 struct mbuf *cmp, **dmpp;
821 {
822 struct bsd_db *db = (struct bsd_db *) state;
823 u_int max_ent = db->max_ent;
824 u_int32_t accm = 0;
825 u_int bitno = 32; /* 1st valid bit in accm */
826 u_int n_bits = db->n_bits;
827 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
828 struct bsd_dict *dictp;
829 int explen, i, seq, len;
830 u_int incode, oldcode, finchar;
831 u_char *p, *rptr, *wptr;
832 struct mbuf *m, *dmp, *mret;
833 int adrs, ctrl, ilen;
834 int space, codelen, extra;
835
836 /*
837 * Save the address/control from the PPP header
838 * and then get the sequence number.
839 */
840 *dmpp = NULL;
841 rptr = mtod(cmp, u_char *);
842 adrs = PPP_ADDRESS(rptr);
843 ctrl = PPP_CONTROL(rptr);
844 rptr += PPP_HDRLEN;
845 len = cmp->m_len - PPP_HDRLEN;
846 seq = 0;
847 for (i = 0; i < 2; ++i) {
848 while (len <= 0) {
849 cmp = cmp->m_next;
850 if (cmp == NULL)
851 return DECOMP_ERROR;
852 rptr = mtod(cmp, u_char *);
853 len = cmp->m_len;
854 }
855 seq = (seq << 8) + *rptr++;
856 --len;
857 }
858
859 /*
860 * Check the sequence number and give up if it differs from
861 * the value we're expecting.
862 */
863 if (seq != db->seqno) {
864 if (db->debug)
865 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
866 db->unit, seq, db->seqno - 1);
867 return DECOMP_ERROR;
868 }
869 ++db->seqno;
870
871 /*
872 * Allocate one mbuf to start with.
873 */
874 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
875 if (dmp == NULL)
876 return DECOMP_ERROR;
877 mret = dmp;
878 dmp->m_len = 0;
879 dmp->m_next = NULL;
880 MCLGET(dmp, M_DONTWAIT);
881 dmp->m_data += db->hdrlen;
882 wptr = mtod(dmp, u_char *);
883 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
884
885 /*
886 * Fill in the ppp header, but not the last byte of the protocol
887 * (that comes from the decompressed data).
888 */
889 wptr[0] = adrs;
890 wptr[1] = ctrl;
891 wptr[2] = 0;
892 wptr += PPP_HDRLEN - 1;
893
894 ilen = len;
895 oldcode = CLEAR;
896 explen = 0;
897 for (;;) {
898 if (len == 0) {
899 cmp = cmp->m_next;
900 if (!cmp) /* quit at end of message */
901 break;
902 rptr = mtod(cmp, u_char *);
903 len = cmp->m_len;
904 ilen += len;
905 continue; /* handle 0-length buffers */
906 }
907
908 /*
909 * Accumulate bytes until we have a complete code.
910 * Then get the next code, relying on the 32-bit,
911 * unsigned accm to mask the result.
912 */
913 bitno -= 8;
914 accm |= *rptr++ << bitno;
915 --len;
916 if (tgtbitno < bitno)
917 continue;
918 incode = accm >> tgtbitno;
919 accm <<= n_bits;
920 bitno += n_bits;
921
922 if (incode == CLEAR) {
923 /*
924 * The dictionary must only be cleared at
925 * the end of a packet. But there could be an
926 * empty mbuf at the end.
927 */
928 if (len > 0 || cmp->m_next != NULL) {
929 while ((cmp = cmp->m_next) != NULL)
930 len += cmp->m_len;
931 if (len > 0) {
932 m_freem(mret);
933 if (db->debug)
934 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
935 return DECOMP_FATALERROR; /* probably a bug */
936 }
937 }
938 bsd_clear(db);
939 explen = ilen = 0;
940 break;
941 }
942
943 if (incode > max_ent + 2 || incode > db->maxmaxcode
944 || (incode > max_ent && oldcode == CLEAR)) {
945 m_freem(mret);
946 if (db->debug) {
947 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
948 db->unit, incode, oldcode);
949 printf("max_ent=0x%x explen=%d seqno=%d\n",
950 max_ent, explen, db->seqno);
951 }
952 return DECOMP_FATALERROR; /* probably a bug */
953 }
954
955 /* Special case for KwKwK string. */
956 if (incode > max_ent) {
957 finchar = oldcode;
958 extra = 1;
959 } else {
960 finchar = incode;
961 extra = 0;
962 }
963
964 codelen = db->lens[finchar];
965 explen += codelen + extra;
966 if (explen > db->mru + 1) {
967 m_freem(mret);
968 if (db->debug) {
969 printf("bsd_decomp%d: ran out of mru\n", db->unit);
970 #ifdef DEBUG
971 while ((cmp = cmp->m_next) != NULL)
972 len += cmp->m_len;
973 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
974 len, finchar, codelen, explen);
975 #endif
976 }
977 return DECOMP_FATALERROR;
978 }
979
980 /*
981 * For simplicity, the decoded characters go in a single mbuf,
982 * so we allocate a single extra cluster mbuf if necessary.
983 */
984 if ((space -= codelen + extra) < 0) {
985 dmp->m_len = wptr - mtod(dmp, u_char *);
986 MGET(m, M_DONTWAIT, MT_DATA);
987 if (m == NULL) {
988 m_freem(mret);
989 return DECOMP_ERROR;
990 }
991 m->m_len = 0;
992 m->m_next = NULL;
993 dmp->m_next = m;
994 MCLGET(m, M_DONTWAIT);
995 space = M_TRAILINGSPACE(m) - (codelen + extra);
996 if (space < 0) {
997 /* now that's what I call *compression*. */
998 m_freem(mret);
999 return DECOMP_ERROR;
1000 }
1001 dmp = m;
1002 wptr = mtod(dmp, u_char *);
1003 }
1004
1005 /*
1006 * Decode this code and install it in the decompressed buffer.
1007 */
1008 p = (wptr += codelen);
1009 while (finchar > LAST) {
1010 dictp = &db->dict[db->dict[finchar].cptr];
1011 #ifdef DEBUG
1012 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1013 goto bad;
1014 #endif
1015 *--p = dictp->f.hs.suffix;
1016 finchar = dictp->f.hs.prefix;
1017 }
1018 *--p = finchar;
1019
1020 #ifdef DEBUG
1021 if (--codelen != 0)
1022 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1023 db->unit, codelen, incode, max_ent);
1024 #endif
1025
1026 if (extra) /* the KwKwK case again */
1027 *wptr++ = finchar;
1028
1029 /*
1030 * If not first code in a packet, and
1031 * if not out of code space, then allocate a new code.
1032 *
1033 * Keep the hash table correct so it can be used
1034 * with uncompressed packets.
1035 */
1036 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1037 struct bsd_dict *dictp2;
1038 u_int32_t fcode;
1039 u_int32_t hval, disp;
1040
1041 fcode = BSD_KEY(oldcode,finchar);
1042 hval = BSD_HASH(oldcode,finchar,db->hshift);
1043 dictp = &db->dict[hval];
1044
1045 /* look for a free hash table entry */
1046 if (dictp->codem1 < max_ent) {
1047 disp = (hval == 0) ? 1 : hval;
1048 do {
1049 hval += disp;
1050 if (hval >= db->hsize)
1051 hval -= db->hsize;
1052 dictp = &db->dict[hval];
1053 } while (dictp->codem1 < max_ent);
1054 }
1055
1056 /*
1057 * Invalidate previous hash table entry
1058 * assigned this code, and then take it over
1059 */
1060 dictp2 = &db->dict[max_ent+1];
1061 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1062 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1063 }
1064 dictp2->cptr = hval;
1065 dictp->codem1 = max_ent;
1066 dictp->f.fcode = fcode;
1067
1068 db->max_ent = ++max_ent;
1069 db->lens[max_ent] = db->lens[oldcode]+1;
1070
1071 /* Expand code size if needed. */
1072 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1073 db->n_bits = ++n_bits;
1074 tgtbitno = 32-n_bits;
1075 }
1076 }
1077 oldcode = incode;
1078 }
1079 dmp->m_len = wptr - mtod(dmp, u_char *);
1080
1081 /*
1082 * Keep the checkpoint right so that incompressible packets
1083 * clear the dictionary at the right times.
1084 */
1085 db->bytes_out += ilen;
1086 db->in_count += explen;
1087 if (bsd_check(db) && db->debug) {
1088 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1089 db->unit);
1090 }
1091
1092 ++db->comp_count;
1093 db->comp_bytes += ilen + BSD_OVHD;
1094 ++db->uncomp_count;
1095 db->uncomp_bytes += explen;
1096
1097 *dmpp = mret;
1098 return DECOMP_OK;
1099
1100 #ifdef DEBUG
1101 bad:
1102 if (codelen <= 0) {
1103 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1104 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1105 incode, finchar, db->dict[finchar].cptr, max_ent);
1106 } else if (dictp->codem1 != finchar-1) {
1107 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1108 db->unit, incode, finchar);
1109 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1110 db->dict[finchar].cptr, dictp->codem1);
1111 }
1112 m_freem(mret);
1113 return DECOMP_FATALERROR;
1114 #endif /* DEBUG */
1115 }
1116 #endif /* DO_BSD_COMPRESS */
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