FreeBSD/Linux Kernel Cross Reference
sys/net/bsd-comp.c
1 /* $NetBSD: bsd-comp.c,v 1.18 2008/06/15 16:37:21 christos 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 1.18 2008/06/15 16:37:21 christos 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 uint16_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 uint16_t *lens; /* array of lengths of codes */
109 struct bsd_dict {
110 union { /* hash value */
111 uint32_t fcode;
112 struct {
113 #if BYTE_ORDER == LITTLE_ENDIAN
114 uint16_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 uint16_t prefix; /* preceding code */
121 #endif
122 } hs;
123 } f;
124 uint16_t codem1; /* output of hash table -1 */
125 uint16_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(u_char *options, int opt_len);
133 static void *bsd_decomp_alloc(u_char *options, int opt_len);
134 static void bsd_free(void *state);
135 static int bsd_comp_init(void *state, u_char *options, int opt_len,
136 int unit, int hdrlen, int debug);
137 static int bsd_decomp_init(void *state, u_char *options, int opt_len,
138 int unit, int hdrlen, int mru, int debug);
139 static int bsd_compress(void *state, struct mbuf **mret,
140 struct mbuf *mp, int slen, int maxolen);
141 static void bsd_incomp(void *state, struct mbuf *dmsg);
142 static int bsd_decompress(void *state, struct mbuf *cmp,
143 struct mbuf **dmpp);
144 static void bsd_reset(void *state);
145 static void bsd_comp_stats(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) ((((uint32_t)(suffix)) << (hshift)) \
179 ^ (uint32_t)(prefix))
180 #define BSD_KEY(prefix,suffix) ((((uint32_t)(suffix)) << 16) \
181 + (uint32_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(struct bsd_db *);
190 static int bsd_check(struct bsd_db *);
191 static void *bsd_alloc(u_char *, int, int);
192 static int bsd_init(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(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(struct bsd_db *db)
225 {
226 u_int new_ratio;
227
228 if (db->in_count >= db->checkpoint) {
229 /* age the ratio by limiting the size of the counts */
230 if (db->in_count >= RATIO_MAX
231 || db->bytes_out >= RATIO_MAX) {
232 db->in_count -= db->in_count/4;
233 db->bytes_out -= db->bytes_out/4;
234 }
235
236 db->checkpoint = db->in_count + CHECK_GAP;
237
238 if (db->max_ent >= db->maxmaxcode) {
239 /* Reset the dictionary only if the ratio is worse,
240 * or if it looks as if it has been poisoned
241 * by incompressible data.
242 *
243 * This does not overflow, because
244 * db->in_count <= RATIO_MAX.
245 */
246 new_ratio = db->in_count << RATIO_SCALE_LOG;
247 if (db->bytes_out != 0)
248 new_ratio /= db->bytes_out;
249
250 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
251 bsd_clear(db);
252 return 1;
253 }
254 db->ratio = new_ratio;
255 }
256 }
257 return 0;
258 }
259
260 /*
261 * Return statistics.
262 */
263 static void
264 bsd_comp_stats(void *state, struct compstat *stats)
265 {
266 struct bsd_db *db = (struct bsd_db *) state;
267 u_int out;
268
269 stats->unc_bytes = db->uncomp_bytes;
270 stats->unc_packets = db->uncomp_count;
271 stats->comp_bytes = db->comp_bytes;
272 stats->comp_packets = db->comp_count;
273 stats->inc_bytes = db->incomp_bytes;
274 stats->inc_packets = db->incomp_count;
275 stats->ratio = db->in_count;
276 out = db->bytes_out;
277 if (stats->ratio <= 0x7fffff)
278 stats->ratio <<= 8;
279 else
280 out >>= 8;
281 if (out != 0)
282 stats->ratio /= out;
283 }
284
285 /*
286 * Reset state, as on a CCP ResetReq.
287 */
288 static void
289 bsd_reset(void *state)
290 {
291 struct bsd_db *db = (struct bsd_db *) state;
292
293 db->seqno = 0;
294 bsd_clear(db);
295 db->clear_count = 0;
296 }
297
298 /*
299 * Allocate space for a (de) compressor.
300 */
301 static void *
302 bsd_alloc(u_char *options, int opt_len, int decomp)
303 {
304 int bits;
305 u_int newlen, hsize, hshift, maxmaxcode;
306 struct bsd_db *db;
307
308 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
309 || options[1] != CILEN_BSD_COMPRESS
310 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
311 return NULL;
312 bits = BSD_NBITS(options[2]);
313 switch (bits) {
314 case 9: /* needs 82152 for both directions */
315 case 10: /* needs 84144 */
316 case 11: /* needs 88240 */
317 case 12: /* needs 96432 */
318 hsize = 5003;
319 hshift = 4;
320 break;
321 case 13: /* needs 176784 */
322 hsize = 9001;
323 hshift = 5;
324 break;
325 case 14: /* needs 353744 */
326 hsize = 18013;
327 hshift = 6;
328 break;
329 case 15: /* needs 691440 */
330 hsize = 35023;
331 hshift = 7;
332 break;
333 case 16: /* needs 1366160--far too much, */
334 /* hsize = 69001; */ /* and 69001 is too big for cptr */
335 /* hshift = 8; */ /* in struct bsd_db */
336 /* break; */
337 default:
338 return NULL;
339 }
340
341 maxmaxcode = MAXCODE(bits);
342 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
343 db = malloc(newlen, M_DEVBUF, M_NOWAIT|M_ZERO);
344 if (!db)
345 return NULL;
346
347 if (!decomp) {
348 db->lens = NULL;
349 } else {
350 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]),
351 M_DEVBUF, M_NOWAIT);
352 if (!db->lens) {
353 free(db, M_DEVBUF);
354 return NULL;
355 }
356 }
357
358 db->totlen = newlen;
359 db->hsize = hsize;
360 db->hshift = hshift;
361 db->maxmaxcode = maxmaxcode;
362 db->maxbits = bits;
363
364 return (void *) db;
365 }
366
367 static void
368 bsd_free(void *state)
369 {
370 struct bsd_db *db = (struct bsd_db *) state;
371
372 if (db->lens)
373 free(db->lens, M_DEVBUF);
374 free(db, M_DEVBUF);
375 }
376
377 static void *
378 bsd_comp_alloc(u_char *options, int opt_len)
379 {
380 return bsd_alloc(options, opt_len, 0);
381 }
382
383 static void *
384 bsd_decomp_alloc(u_char *options, int opt_len)
385 {
386 return bsd_alloc(options, opt_len, 1);
387 }
388
389 /*
390 * Initialize the database.
391 */
392 static int
393 bsd_init(struct bsd_db *db, u_char *options, int opt_len, int unit, int hdrlen,
394 int mru, int debug, int decomp)
395 {
396 int i;
397
398 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
399 || options[1] != CILEN_BSD_COMPRESS
400 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
401 || BSD_NBITS(options[2]) != db->maxbits
402 || (decomp && db->lens == NULL))
403 return 0;
404
405 if (decomp) {
406 i = LAST+1;
407 while (i != 0)
408 db->lens[--i] = 1;
409 }
410 i = db->hsize;
411 while (i != 0) {
412 db->dict[--i].codem1 = BADCODEM1;
413 db->dict[i].cptr = 0;
414 }
415
416 db->unit = unit;
417 db->hdrlen = hdrlen;
418 db->mru = mru;
419 #ifndef DEBUG
420 if (debug)
421 #endif
422 db->debug = 1;
423
424 bsd_reset(db);
425
426 return 1;
427 }
428
429 static int
430 bsd_comp_init(void *state, u_char *options, int opt_len, int unit, int hdrlen,
431 int debug)
432 {
433 return bsd_init((struct bsd_db *) state, options, opt_len,
434 unit, hdrlen, 0, debug, 0);
435 }
436
437 static int
438 bsd_decomp_init(void *state, u_char *options, int opt_len, int unit, int hdrlen,
439 int mru, int debug)
440 {
441 return bsd_init((struct bsd_db *) state, options, opt_len,
442 unit, hdrlen, mru, debug, 1);
443 }
444
445
446 /*
447 * compress a packet
448 * One change from the BSD compress command is that when the
449 * code size expands, we do not output a bunch of padding.
450 */
451 int /* new slen */
452 bsd_compress(void *state,
453 struct mbuf **mret /* return compressed mbuf chain here */,
454 struct mbuf *mp /* from here */,
455 int slen, int maxolen)
456 {
457 struct bsd_db *db = (struct bsd_db *) state;
458 int hshift = db->hshift;
459 u_int max_ent = db->max_ent;
460 u_int n_bits = db->n_bits;
461 u_int bitno = 32;
462 uint32_t accm = 0, fcode;
463 struct bsd_dict *dictp;
464 u_char c;
465 int hval, disp, ent, ilen;
466 u_char *rptr, *wptr;
467 u_char *cp_end;
468 int olen;
469 struct mbuf *m;
470
471 #define PUTBYTE(v) { \
472 ++olen; \
473 if (wptr) { \
474 *wptr++ = (v); \
475 if (wptr >= cp_end) { \
476 m->m_len = wptr - mtod(m, u_char *); \
477 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
478 m = m->m_next; \
479 if (m) { \
480 m->m_len = 0; \
481 if (maxolen - olen > MLEN) \
482 MCLGET(m, M_DONTWAIT); \
483 wptr = mtod(m, u_char *); \
484 cp_end = wptr + M_TRAILINGSPACE(m); \
485 } else \
486 wptr = NULL; \
487 } \
488 } \
489 }
490
491 #define OUTPUT(ent) { \
492 bitno -= n_bits; \
493 accm |= ((ent) << bitno); \
494 do { \
495 PUTBYTE(accm >> 24); \
496 accm <<= 8; \
497 bitno += 8; \
498 } while (bitno <= 24); \
499 }
500
501 /*
502 * If the protocol is not in the range we're interested in,
503 * just return without compressing the packet. If it is,
504 * the protocol becomes the first byte to compress.
505 */
506 rptr = mtod(mp, u_char *);
507 ent = PPP_PROTOCOL(rptr);
508 if (ent < 0x21 || ent > 0xf9) {
509 *mret = NULL;
510 return slen;
511 }
512
513 /* Don't generate compressed packets which are larger than
514 the uncompressed packet. */
515 if (maxolen > slen)
516 maxolen = slen;
517
518 /* Allocate one mbuf to start with. */
519 MGET(m, M_DONTWAIT, MT_DATA);
520 *mret = m;
521 if (m != NULL) {
522 m->m_len = 0;
523 if (maxolen + db->hdrlen > MLEN)
524 MCLGET(m, M_DONTWAIT);
525 m->m_data += db->hdrlen;
526 wptr = mtod(m, u_char *);
527 cp_end = wptr + M_TRAILINGSPACE(m);
528 } else
529 wptr = cp_end = NULL;
530
531 /*
532 * Copy the PPP header over, changing the protocol,
533 * and install the 2-byte packet sequence number.
534 */
535 if (wptr) {
536 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
537 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
538 *wptr++ = 0; /* change the protocol */
539 *wptr++ = PPP_COMP;
540 *wptr++ = db->seqno >> 8;
541 *wptr++ = db->seqno;
542 }
543 ++db->seqno;
544
545 olen = 0;
546 rptr += PPP_HDRLEN;
547 slen = mp->m_len - PPP_HDRLEN;
548 ilen = slen + 1;
549 for (;;) {
550 if (slen <= 0) {
551 mp = mp->m_next;
552 if (!mp)
553 break;
554 rptr = mtod(mp, u_char *);
555 slen = mp->m_len;
556 if (!slen)
557 continue; /* handle 0-length buffers */
558 ilen += slen;
559 }
560
561 slen--;
562 c = *rptr++;
563 fcode = BSD_KEY(ent, c);
564 hval = BSD_HASH(ent, c, hshift);
565 dictp = &db->dict[hval];
566
567 /* Validate and then check the entry. */
568 if (dictp->codem1 >= max_ent)
569 goto nomatch;
570 if (dictp->f.fcode == fcode) {
571 ent = dictp->codem1+1;
572 continue; /* found (prefix,suffix) */
573 }
574
575 /* continue probing until a match or invalid entry */
576 disp = (hval == 0) ? 1 : hval;
577 do {
578 hval += disp;
579 if (hval >= db->hsize)
580 hval -= db->hsize;
581 dictp = &db->dict[hval];
582 if (dictp->codem1 >= max_ent)
583 goto nomatch;
584 } while (dictp->f.fcode != fcode);
585 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
586 continue;
587
588 nomatch:
589 OUTPUT(ent); /* output the prefix */
590
591 /* code -> hashtable */
592 if (max_ent < db->maxmaxcode) {
593 struct bsd_dict *dictp2;
594 /* expand code size if needed */
595 if (max_ent >= MAXCODE(n_bits))
596 db->n_bits = ++n_bits;
597
598 /* Invalidate old hash table entry using
599 * this code, and then take it over.
600 */
601 dictp2 = &db->dict[max_ent+1];
602 if (db->dict[dictp2->cptr].codem1 == max_ent)
603 db->dict[dictp2->cptr].codem1 = BADCODEM1;
604 dictp2->cptr = hval;
605 dictp->codem1 = max_ent;
606 dictp->f.fcode = fcode;
607
608 db->max_ent = ++max_ent;
609 }
610 ent = c;
611 }
612
613 OUTPUT(ent); /* output the last code */
614 db->bytes_out += olen;
615 db->in_count += ilen;
616 if (bitno < 32)
617 ++db->bytes_out; /* count complete bytes */
618
619 if (bsd_check(db))
620 OUTPUT(CLEAR); /* do not count the CLEAR */
621
622 /*
623 * Pad dribble bits of last code with ones.
624 * Do not emit a completely useless byte of ones.
625 */
626 if (bitno != 32)
627 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
628
629 if (m != NULL) {
630 m->m_len = wptr - mtod(m, u_char *);
631 m->m_next = NULL;
632 }
633
634 /*
635 * Increase code size if we would have without the packet
636 * boundary and as the decompressor will.
637 */
638 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
639 db->n_bits++;
640
641 db->uncomp_bytes += ilen;
642 ++db->uncomp_count;
643 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
644 /* throw away the compressed stuff if it is longer than uncompressed */
645 if (*mret != NULL) {
646 m_freem(*mret);
647 *mret = NULL;
648 }
649 ++db->incomp_count;
650 db->incomp_bytes += ilen;
651 } else {
652 ++db->comp_count;
653 db->comp_bytes += olen + BSD_OVHD;
654 }
655
656 return olen + PPP_HDRLEN + BSD_OVHD;
657 #undef OUTPUT
658 #undef PUTBYTE
659 }
660
661
662 /*
663 * Update the "BSD Compress" dictionary on the receiver for
664 * incompressible data by pretending to compress the incoming data.
665 */
666 static void
667 bsd_incomp(void *state, struct mbuf *dmsg)
668 {
669 struct bsd_db *db = (struct bsd_db *) state;
670 u_int hshift = db->hshift;
671 u_int max_ent = db->max_ent;
672 u_int n_bits = db->n_bits;
673 struct bsd_dict *dictp;
674 uint32_t fcode;
675 u_char c;
676 uint32_t hval, disp;
677 int slen, ilen;
678 u_int bitno = 7;
679 u_char *rptr;
680 u_int ent;
681
682 /*
683 * If the protocol is not in the range we're interested in,
684 * just return without looking at the packet. If it is,
685 * the protocol becomes the first byte to "compress".
686 */
687 rptr = mtod(dmsg, u_char *);
688 ent = PPP_PROTOCOL(rptr);
689 if (ent < 0x21 || ent > 0xf9)
690 return;
691
692 db->seqno++;
693 ilen = 1; /* count the protocol as 1 byte */
694 rptr += PPP_HDRLEN;
695 slen = dmsg->m_len - PPP_HDRLEN;
696 for (;;) {
697 if (slen <= 0) {
698 dmsg = dmsg->m_next;
699 if (!dmsg)
700 break;
701 rptr = mtod(dmsg, u_char *);
702 slen = dmsg->m_len;
703 continue;
704 }
705 ilen += slen;
706
707 do {
708 c = *rptr++;
709 fcode = BSD_KEY(ent, c);
710 hval = BSD_HASH(ent, c, hshift);
711 dictp = &db->dict[hval];
712
713 /* validate and then check the entry */
714 if (dictp->codem1 >= max_ent)
715 goto nomatch;
716 if (dictp->f.fcode == fcode) {
717 ent = dictp->codem1+1;
718 continue; /* found (prefix,suffix) */
719 }
720
721 /* continue probing until a match or invalid entry */
722 disp = (hval == 0) ? 1 : hval;
723 do {
724 hval += disp;
725 if (hval >= db->hsize)
726 hval -= db->hsize;
727 dictp = &db->dict[hval];
728 if (dictp->codem1 >= max_ent)
729 goto nomatch;
730 } while (dictp->f.fcode != fcode);
731 ent = dictp->codem1+1;
732 continue; /* finally found (prefix,suffix) */
733
734 nomatch: /* output (count) the prefix */
735 bitno += n_bits;
736
737 /* code -> hashtable */
738 if (max_ent < db->maxmaxcode) {
739 struct bsd_dict *dictp2;
740 /* expand code size if needed */
741 if (max_ent >= MAXCODE(n_bits))
742 db->n_bits = ++n_bits;
743
744 /* Invalidate previous hash table entry
745 * assigned this code, and then take it over.
746 */
747 dictp2 = &db->dict[max_ent+1];
748 if (db->dict[dictp2->cptr].codem1 == max_ent)
749 db->dict[dictp2->cptr].codem1 = BADCODEM1;
750 dictp2->cptr = hval;
751 dictp->codem1 = max_ent;
752 dictp->f.fcode = fcode;
753
754 db->max_ent = ++max_ent;
755 db->lens[max_ent] = db->lens[ent]+1;
756 }
757 ent = c;
758 } while (--slen != 0);
759 }
760 bitno += n_bits; /* output (count) the last code */
761 db->bytes_out += bitno/8;
762 db->in_count += ilen;
763 (void)bsd_check(db);
764
765 ++db->incomp_count;
766 db->incomp_bytes += ilen;
767 ++db->uncomp_count;
768 db->uncomp_bytes += ilen;
769
770 /* Increase code size if we would have without the packet
771 * boundary and as the decompressor will.
772 */
773 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
774 db->n_bits++;
775 }
776
777
778 /*
779 * Decompress "BSD Compress".
780 *
781 * Because of patent problems, we return DECOMP_ERROR for errors
782 * found by inspecting the input data and for system problems, but
783 * DECOMP_FATALERROR for any errors which could possibly be said to
784 * be being detected "after" decompression. For DECOMP_ERROR,
785 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
786 * infringing a patent of Motorola's if we do, so we take CCP down
787 * instead.
788 *
789 * Given that the frame has the correct sequence number and a good FCS,
790 * errors such as invalid codes in the input most likely indicate a
791 * bug, so we return DECOMP_FATALERROR for them in order to turn off
792 * compression, even though they are detected by inspecting the input.
793 */
794 int
795 bsd_decompress(void *state, struct mbuf *cmp, struct mbuf **dmpp)
796 {
797 struct bsd_db *db = (struct bsd_db *) state;
798 u_int max_ent = db->max_ent;
799 uint32_t accm = 0;
800 u_int bitno = 32; /* 1st valid bit in accm */
801 u_int n_bits = db->n_bits;
802 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
803 struct bsd_dict *dictp;
804 int explen, i, seq, len;
805 u_int incode, oldcode, finchar;
806 u_char *p, *rptr, *wptr;
807 struct mbuf *m, *dmp, *mret;
808 int adrs, ctrl, ilen;
809 int space, codelen, extra;
810
811 /*
812 * Save the address/control from the PPP header
813 * and then get the sequence number.
814 */
815 *dmpp = NULL;
816 rptr = mtod(cmp, u_char *);
817 adrs = PPP_ADDRESS(rptr);
818 ctrl = PPP_CONTROL(rptr);
819 rptr += PPP_HDRLEN;
820 len = cmp->m_len - PPP_HDRLEN;
821 seq = 0;
822 for (i = 0; i < 2; ++i) {
823 while (len <= 0) {
824 cmp = cmp->m_next;
825 if (cmp == NULL)
826 return DECOMP_ERROR;
827 rptr = mtod(cmp, u_char *);
828 len = cmp->m_len;
829 }
830 seq = (seq << 8) + *rptr++;
831 --len;
832 }
833
834 /*
835 * Check the sequence number and give up if it differs from
836 * the value we're expecting.
837 */
838 if (seq != db->seqno) {
839 if (db->debug)
840 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
841 db->unit, seq, db->seqno - 1);
842 return DECOMP_ERROR;
843 }
844 ++db->seqno;
845
846 /*
847 * Allocate one mbuf to start with.
848 */
849 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
850 if (dmp == NULL)
851 return DECOMP_ERROR;
852 mret = dmp;
853 dmp->m_len = 0;
854 dmp->m_next = NULL;
855 MCLGET(dmp, M_DONTWAIT);
856 dmp->m_data += db->hdrlen;
857 wptr = mtod(dmp, u_char *);
858 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
859
860 /*
861 * Fill in the ppp header, but not the last byte of the protocol
862 * (that comes from the decompressed data).
863 */
864 wptr[0] = adrs;
865 wptr[1] = ctrl;
866 wptr[2] = 0;
867 wptr += PPP_HDRLEN - 1;
868
869 ilen = len;
870 oldcode = CLEAR;
871 explen = 0;
872 for (;;) {
873 if (len == 0) {
874 cmp = cmp->m_next;
875 if (!cmp) /* quit at end of message */
876 break;
877 rptr = mtod(cmp, u_char *);
878 len = cmp->m_len;
879 ilen += len;
880 continue; /* handle 0-length buffers */
881 }
882
883 /*
884 * Accumulate bytes until we have a complete code.
885 * Then get the next code, relying on the 32-bit,
886 * unsigned accm to mask the result.
887 */
888 bitno -= 8;
889 accm |= *rptr++ << bitno;
890 --len;
891 if (tgtbitno < bitno)
892 continue;
893 incode = accm >> tgtbitno;
894 accm <<= n_bits;
895 bitno += n_bits;
896
897 if (incode == CLEAR) {
898 /*
899 * The dictionary must only be cleared at
900 * the end of a packet. But there could be an
901 * empty mbuf at the end.
902 */
903 if (len > 0 || cmp->m_next != NULL) {
904 while ((cmp = cmp->m_next) != NULL)
905 len += cmp->m_len;
906 if (len > 0) {
907 m_freem(mret);
908 if (db->debug)
909 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
910 return DECOMP_FATALERROR; /* probably a bug */
911 }
912 }
913 bsd_clear(db);
914 explen = ilen = 0;
915 break;
916 }
917
918 if (incode > max_ent + 2 || incode > db->maxmaxcode
919 || (incode > max_ent && oldcode == CLEAR)) {
920 m_freem(mret);
921 if (db->debug) {
922 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
923 db->unit, incode, oldcode);
924 printf("max_ent=0x%x explen=%d seqno=%d\n",
925 max_ent, explen, db->seqno);
926 }
927 return DECOMP_FATALERROR; /* probably a bug */
928 }
929
930 /* Special case for KwKwK string. */
931 if (incode > max_ent) {
932 finchar = oldcode;
933 extra = 1;
934 } else {
935 finchar = incode;
936 extra = 0;
937 }
938
939 codelen = db->lens[finchar];
940 explen += codelen + extra;
941 if (explen > db->mru + 1) {
942 m_freem(mret);
943 if (db->debug) {
944 printf("bsd_decomp%d: ran out of mru\n", db->unit);
945 #ifdef DEBUG
946 while ((cmp = cmp->m_next) != NULL)
947 len += cmp->m_len;
948 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
949 len, finchar, codelen, explen);
950 #endif
951 }
952 return DECOMP_FATALERROR;
953 }
954
955 /*
956 * For simplicity, the decoded characters go in a single mbuf,
957 * so we allocate a single extra cluster mbuf if necessary.
958 */
959 if ((space -= codelen + extra) < 0) {
960 dmp->m_len = wptr - mtod(dmp, u_char *);
961 MGET(m, M_DONTWAIT, MT_DATA);
962 if (m == NULL) {
963 m_freem(mret);
964 return DECOMP_ERROR;
965 }
966 m->m_len = 0;
967 m->m_next = NULL;
968 dmp->m_next = m;
969 MCLGET(m, M_DONTWAIT);
970 space = M_TRAILINGSPACE(m) - (codelen + extra);
971 if (space < 0) {
972 /* now that's what I call *compression*. */
973 m_freem(mret);
974 return DECOMP_ERROR;
975 }
976 dmp = m;
977 wptr = mtod(dmp, u_char *);
978 }
979
980 /*
981 * Decode this code and install it in the decompressed buffer.
982 */
983 p = (wptr += codelen);
984 while (finchar > LAST) {
985 dictp = &db->dict[db->dict[finchar].cptr];
986 #ifdef DEBUG
987 if (--codelen <= 0 || dictp->codem1 != finchar-1)
988 goto bad;
989 #endif
990 *--p = dictp->f.hs.suffix;
991 finchar = dictp->f.hs.prefix;
992 }
993 *--p = finchar;
994
995 #ifdef DEBUG
996 if (--codelen != 0)
997 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
998 db->unit, codelen, incode, max_ent);
999 #endif
1000
1001 if (extra) /* the KwKwK case again */
1002 *wptr++ = finchar;
1003
1004 /*
1005 * If not first code in a packet, and
1006 * if not out of code space, then allocate a new code.
1007 *
1008 * Keep the hash table correct so it can be used
1009 * with uncompressed packets.
1010 */
1011 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1012 struct bsd_dict *dictp2;
1013 uint32_t fcode;
1014 uint32_t hval, disp;
1015
1016 fcode = BSD_KEY(oldcode,finchar);
1017 hval = BSD_HASH(oldcode,finchar,db->hshift);
1018 dictp = &db->dict[hval];
1019
1020 /* look for a free hash table entry */
1021 if (dictp->codem1 < max_ent) {
1022 disp = (hval == 0) ? 1 : hval;
1023 do {
1024 hval += disp;
1025 if (hval >= db->hsize)
1026 hval -= db->hsize;
1027 dictp = &db->dict[hval];
1028 } while (dictp->codem1 < max_ent);
1029 }
1030
1031 /*
1032 * Invalidate previous hash table entry
1033 * assigned this code, and then take it over
1034 */
1035 dictp2 = &db->dict[max_ent+1];
1036 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1037 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1038 }
1039 dictp2->cptr = hval;
1040 dictp->codem1 = max_ent;
1041 dictp->f.fcode = fcode;
1042
1043 db->max_ent = ++max_ent;
1044 db->lens[max_ent] = db->lens[oldcode]+1;
1045
1046 /* Expand code size if needed. */
1047 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1048 db->n_bits = ++n_bits;
1049 tgtbitno = 32-n_bits;
1050 }
1051 }
1052 oldcode = incode;
1053 }
1054 dmp->m_len = wptr - mtod(dmp, u_char *);
1055
1056 /*
1057 * Keep the checkpoint right so that incompressible packets
1058 * clear the dictionary at the right times.
1059 */
1060 db->bytes_out += ilen;
1061 db->in_count += explen;
1062 if (bsd_check(db) && db->debug) {
1063 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1064 db->unit);
1065 }
1066
1067 ++db->comp_count;
1068 db->comp_bytes += ilen + BSD_OVHD;
1069 ++db->uncomp_count;
1070 db->uncomp_bytes += explen;
1071
1072 *dmpp = mret;
1073 return DECOMP_OK;
1074
1075 #ifdef DEBUG
1076 bad:
1077 if (codelen <= 0) {
1078 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1079 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1080 incode, finchar, db->dict[finchar].cptr, max_ent);
1081 } else if (dictp->codem1 != finchar-1) {
1082 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1083 db->unit, incode, finchar);
1084 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1085 db->dict[finchar].cptr, dictp->codem1);
1086 }
1087 m_freem(mret);
1088 return DECOMP_FATALERROR;
1089 #endif /* DEBUG */
1090 }
1091 #endif /* DO_BSD_COMPRESS */
Cache object: af07ed4ac626a71a313e2fdf43091dfc
|