__P() removal
[dragonfly.git] / sys / net / bsd_comp.c
CommitLineData
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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: src/sys/net/bsd_comp.c,v 1.11.2.1 2002/04/14 21:41:48 luigi Exp $
158abb01 44 * $DragonFly: src/sys/net/bsd_comp.c,v 1.4 2003/08/26 20:49:47 rob Exp $
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45 */
46
47#include <sys/param.h>
48#include <sys/systm.h>
49#include <sys/malloc.h>
50#include <sys/mbuf.h>
d2438d69 51#include <net/ppp_layer/ppp_defs.h>
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52
53#define PACKETPTR struct mbuf *
d2438d69 54#include <net/ppp_layer/ppp_comp.h>
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55
56#if DO_BSD_COMPRESS
57/*
58 * PPP "BSD compress" compression
59 * The differences between this compression and the classic BSD LZW
60 * source are obvious from the requirement that the classic code worked
61 * with files while this handles arbitrarily long streams that
62 * are broken into packets. They are:
63 *
64 * When the code size expands, a block of junk is not emitted by
65 * the compressor and not expected by the decompressor.
66 *
67 * New codes are not necessarily assigned every time an old
68 * code is output by the compressor. This is because a packet
69 * end forces a code to be emitted, but does not imply that a
70 * new sequence has been seen.
71 *
72 * The compression ratio is checked at the first end of a packet
73 * after the appropriate gap. Besides simplifying and speeding
74 * things up, this makes it more likely that the transmitter
75 * and receiver will agree when the dictionary is cleared when
76 * compression is not going well.
77 */
78
79/*
80 * A dictionary for doing BSD compress.
81 */
82struct bsd_db {
83 int totlen; /* length of this structure */
84 u_int hsize; /* size of the hash table */
85 u_char hshift; /* used in hash function */
86 u_char n_bits; /* current bits/code */
87 u_char maxbits;
88 u_char debug;
89 u_char unit;
90 u_int16_t seqno; /* sequence # of next packet */
91 u_int hdrlen; /* header length to preallocate */
92 u_int mru;
93 u_int maxmaxcode; /* largest valid code */
94 u_int max_ent; /* largest code in use */
95 u_int in_count; /* uncompressed bytes, aged */
96 u_int bytes_out; /* compressed bytes, aged */
97 u_int ratio; /* recent compression ratio */
98 u_int checkpoint; /* when to next check the ratio */
99 u_int clear_count; /* times dictionary cleared */
100 u_int incomp_count; /* incompressible packets */
101 u_int incomp_bytes; /* incompressible bytes */
102 u_int uncomp_count; /* uncompressed packets */
103 u_int uncomp_bytes; /* uncompressed bytes */
104 u_int comp_count; /* compressed packets */
105 u_int comp_bytes; /* compressed bytes */
106 u_int16_t *lens; /* array of lengths of codes */
107 struct bsd_dict {
108 union { /* hash value */
109 u_int32_t fcode;
110 struct {
111#if BYTE_ORDER == LITTLE_ENDIAN
112 u_int16_t prefix; /* preceding code */
113 u_char suffix; /* last character of new code */
114 u_char pad;
115#else
116 u_char pad;
117 u_char suffix; /* last character of new code */
118 u_int16_t prefix; /* preceding code */
119#endif
120 } hs;
121 } f;
122 u_int16_t codem1; /* output of hash table -1 */
123 u_int16_t cptr; /* map code to hash table entry */
124 } dict[1];
125};
126
127#define BSD_OVHD 2 /* BSD compress overhead/packet */
128#define BSD_INIT_BITS BSD_MIN_BITS
129
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130static void bsd_clear (struct bsd_db *db);
131static int bsd_check (struct bsd_db *db);
132static void *bsd_alloc (u_char *options, int opt_len, int decomp);
133static int bsd_init (struct bsd_db *db, u_char *options, int opt_len,
984263bc 134 int unit, int hdrlen, int mru, int debug,
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135 int decomp);
136static void *bsd_comp_alloc (u_char *options, int opt_len);
137static void *bsd_decomp_alloc (u_char *options, int opt_len);
138static void bsd_free (void *state);
139static int bsd_comp_init (void *state, u_char *options, int opt_len,
140 int unit, int hdrlen, int debug);
141static int bsd_decomp_init (void *state, u_char *options, int opt_len,
142 int unit, int hdrlen, int mru, int debug);
143static int bsd_compress (void *state, struct mbuf **mret,
144 struct mbuf *mp, int slen, int maxolen);
145static void bsd_incomp (void *state, struct mbuf *dmsg);
146static int bsd_decompress (void *state, struct mbuf *cmp,
147 struct mbuf **dmpp);
148static void bsd_reset (void *state);
149static void bsd_comp_stats (void *state, struct compstat *stats);
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150
151/*
152 * Procedures exported to if_ppp.c.
153 */
154struct compressor ppp_bsd_compress = {
155 CI_BSD_COMPRESS, /* compress_proto */
156 bsd_comp_alloc, /* comp_alloc */
157 bsd_free, /* comp_free */
158 bsd_comp_init, /* comp_init */
159 bsd_reset, /* comp_reset */
160 bsd_compress, /* compress */
161 bsd_comp_stats, /* comp_stat */
162 bsd_decomp_alloc, /* decomp_alloc */
163 bsd_free, /* decomp_free */
164 bsd_decomp_init, /* decomp_init */
165 bsd_reset, /* decomp_reset */
166 bsd_decompress, /* decompress */
167 bsd_incomp, /* incomp */
168 bsd_comp_stats, /* decomp_stat */
169};
170
171/*
172 * the next two codes should not be changed lightly, as they must not
173 * lie within the contiguous general code space.
174 */
175#define CLEAR 256 /* table clear output code */
176#define FIRST 257 /* first free entry */
177#define LAST 255
178
179#define MAXCODE(b) ((1 << (b)) - 1)
180#define BADCODEM1 MAXCODE(BSD_MAX_BITS)
181
182#define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
183 ^ (u_int32_t)(prefix))
184#define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
185 + (u_int32_t)(prefix))
186
187#define CHECK_GAP 10000 /* Ratio check interval */
188
189#define RATIO_SCALE_LOG 8
190#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
191#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
192
193/*
194 * clear the dictionary
195 */
196static void
197bsd_clear(db)
198 struct bsd_db *db;
199{
200 db->clear_count++;
201 db->max_ent = FIRST-1;
202 db->n_bits = BSD_INIT_BITS;
203 db->ratio = 0;
204 db->bytes_out = 0;
205 db->in_count = 0;
206 db->checkpoint = CHECK_GAP;
207}
208
209/*
210 * If the dictionary is full, then see if it is time to reset it.
211 *
212 * Compute the compression ratio using fixed-point arithmetic
213 * with 8 fractional bits.
214 *
215 * Since we have an infinite stream instead of a single file,
216 * watch only the local compression ratio.
217 *
218 * Since both peers must reset the dictionary at the same time even in
219 * the absence of CLEAR codes (while packets are incompressible), they
220 * must compute the same ratio.
221 */
222static int /* 1=output CLEAR */
223bsd_check(db)
224 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 */
263static void
264bsd_comp_stats(state, stats)
265 void *state;
266 struct compstat *stats;
267{
268 struct bsd_db *db = (struct bsd_db *) state;
269 u_int out;
270
271 stats->unc_bytes = db->uncomp_bytes;
272 stats->unc_packets = db->uncomp_count;
273 stats->comp_bytes = db->comp_bytes;
274 stats->comp_packets = db->comp_count;
275 stats->inc_bytes = db->incomp_bytes;
276 stats->inc_packets = db->incomp_count;
277 stats->ratio = db->in_count;
278 out = db->bytes_out;
279 if (stats->ratio <= 0x7fffff)
280 stats->ratio <<= 8;
281 else
282 out >>= 8;
283 if (out != 0)
284 stats->ratio /= out;
285}
286
287/*
288 * Reset state, as on a CCP ResetReq.
289 */
290static void
291bsd_reset(state)
292 void *state;
293{
294 struct bsd_db *db = (struct bsd_db *) state;
295
296 db->seqno = 0;
297 bsd_clear(db);
298 db->clear_count = 0;
299}
300
301/*
302 * Allocate space for a (de) compressor.
303 */
304static void *
305bsd_alloc(options, opt_len, decomp)
306 u_char *options;
307 int opt_len, decomp;
308{
309 int bits;
310 u_int newlen, hsize, hshift, maxmaxcode;
311 struct bsd_db *db;
312
313 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
314 || options[1] != CILEN_BSD_COMPRESS
315 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
316 return NULL;
317 bits = BSD_NBITS(options[2]);
318 switch (bits) {
319 case 9: /* needs 82152 for both directions */
320 case 10: /* needs 84144 */
321 case 11: /* needs 88240 */
322 case 12: /* needs 96432 */
323 hsize = 5003;
324 hshift = 4;
325 break;
326 case 13: /* needs 176784 */
327 hsize = 9001;
328 hshift = 5;
329 break;
330 case 14: /* needs 353744 */
331 hsize = 18013;
332 hshift = 6;
333 break;
334 case 15: /* needs 691440 */
335 hsize = 35023;
336 hshift = 7;
337 break;
338 case 16: /* needs 1366160--far too much, */
339 /* hsize = 69001; */ /* and 69001 is too big for cptr */
340 /* hshift = 8; */ /* in struct bsd_db */
341 /* break; */
342 default:
343 return NULL;
344 }
345
346 maxmaxcode = MAXCODE(bits);
347 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
348 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
349 if (!db)
350 return NULL;
351 bzero(db, sizeof(*db) - sizeof(db->dict));
352
353 if (!decomp) {
354 db->lens = NULL;
355 } else {
356 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
357 M_DEVBUF, M_NOWAIT);
358 if (!db->lens) {
359 free(db, M_DEVBUF);
360 return NULL;
361 }
362 }
363
364 db->totlen = newlen;
365 db->hsize = hsize;
366 db->hshift = hshift;
367 db->maxmaxcode = maxmaxcode;
368 db->maxbits = bits;
369
370 return (void *) db;
371}
372
373static void
374bsd_free(state)
375 void *state;
376{
377 struct bsd_db *db = (struct bsd_db *) state;
378
379 if (db->lens)
380 free(db->lens, M_DEVBUF);
381 free(db, M_DEVBUF);
382}
383
384static void *
385bsd_comp_alloc(options, opt_len)
386 u_char *options;
387 int opt_len;
388{
389 return bsd_alloc(options, opt_len, 0);
390}
391
392static void *
393bsd_decomp_alloc(options, opt_len)
394 u_char *options;
395 int opt_len;
396{
397 return bsd_alloc(options, opt_len, 1);
398}
399
400/*
401 * Initialize the database.
402 */
403static int
404bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
405 struct bsd_db *db;
406 u_char *options;
407 int opt_len, unit, hdrlen, mru, debug, decomp;
408{
409 int i;
410
411 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
412 || options[1] != CILEN_BSD_COMPRESS
413 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
414 || BSD_NBITS(options[2]) != db->maxbits
415 || (decomp && db->lens == NULL))
416 return 0;
417
418 if (decomp) {
419 i = LAST+1;
420 while (i != 0)
421 db->lens[--i] = 1;
422 }
423 i = db->hsize;
424 while (i != 0) {
425 db->dict[--i].codem1 = BADCODEM1;
426 db->dict[i].cptr = 0;
427 }
428
429 db->unit = unit;
430 db->hdrlen = hdrlen;
431 db->mru = mru;
432#ifndef DEBUG
433 if (debug)
434#endif
435 db->debug = 1;
436
437 bsd_reset(db);
438
439 return 1;
440}
441
442static int
443bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
444 void *state;
445 u_char *options;
446 int opt_len, unit, hdrlen, debug;
447{
448 return bsd_init((struct bsd_db *) state, options, opt_len,
449 unit, hdrlen, 0, debug, 0);
450}
451
452static int
453bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
454 void *state;
455 u_char *options;
456 int opt_len, unit, hdrlen, mru, debug;
457{
458 return bsd_init((struct bsd_db *) state, options, opt_len,
459 unit, hdrlen, mru, debug, 1);
460}
461
462
463/*
464 * compress a packet
465 * One change from the BSD compress command is that when the
466 * code size expands, we do not output a bunch of padding.
467 */
468int /* new slen */
469bsd_compress(state, mret, mp, slen, maxolen)
470 void *state;
471 struct mbuf **mret; /* return compressed mbuf chain here */
472 struct mbuf *mp; /* from here */
473 int slen; /* uncompressed length */
474 int maxolen; /* max compressed length */
475{
476 struct bsd_db *db = (struct bsd_db *) state;
477 int hshift = db->hshift;
478 u_int max_ent = db->max_ent;
479 u_int n_bits = db->n_bits;
480 u_int bitno = 32;
481 u_int32_t accm = 0, fcode;
482 struct bsd_dict *dictp;
483 u_char c;
484 int hval, disp, ent, ilen;
485 u_char *rptr, *wptr;
486 u_char *cp_end;
487 int olen;
488 struct mbuf *m;
489
490#define PUTBYTE(v) { \
491 ++olen; \
492 if (wptr) { \
493 *wptr++ = (v); \
494 if (wptr >= cp_end) { \
495 m->m_len = wptr - mtod(m, u_char *); \
496 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
497 m = m->m_next; \
498 if (m) { \
499 m->m_len = 0; \
500 if (maxolen - olen > MLEN) \
501 MCLGET(m, M_DONTWAIT); \
502 wptr = mtod(m, u_char *); \
503 cp_end = wptr + M_TRAILINGSPACE(m); \
504 } else \
505 wptr = NULL; \
506 } \
507 } \
508}
509
510#define OUTPUT(ent) { \
511 bitno -= n_bits; \
512 accm |= ((ent) << bitno); \
513 do { \
514 PUTBYTE(accm >> 24); \
515 accm <<= 8; \
516 bitno += 8; \
517 } while (bitno <= 24); \
518}
519
520 /*
521 * If the protocol is not in the range we're interested in,
522 * just return without compressing the packet. If it is,
523 * the protocol becomes the first byte to compress.
524 */
525 rptr = mtod(mp, u_char *);
526 ent = PPP_PROTOCOL(rptr);
527 if (ent < 0x21 || ent > 0xf9) {
528 *mret = NULL;
529 return slen;
530 }
531
532 /* Don't generate compressed packets which are larger than
533 the uncompressed packet. */
534 if (maxolen > slen)
535 maxolen = slen;
536
537 /* Allocate one mbuf to start with. */
538 MGET(m, M_DONTWAIT, MT_DATA);
539 *mret = m;
540 if (m != NULL) {
541 m->m_len = 0;
542 if (maxolen + db->hdrlen > MLEN)
543 MCLGET(m, M_DONTWAIT);
544 m->m_data += db->hdrlen;
545 wptr = mtod(m, u_char *);
546 cp_end = wptr + M_TRAILINGSPACE(m);
547 } else
548 wptr = cp_end = NULL;
549
550 /*
551 * Copy the PPP header over, changing the protocol,
552 * and install the 2-byte packet sequence number.
553 */
554 if (wptr) {
555 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
556 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
557 *wptr++ = 0; /* change the protocol */
558 *wptr++ = PPP_COMP;
559 *wptr++ = db->seqno >> 8;
560 *wptr++ = db->seqno;
561 }
562 ++db->seqno;
563
564 olen = 0;
565 rptr += PPP_HDRLEN;
566 slen = mp->m_len - PPP_HDRLEN;
567 ilen = slen + 1;
568 for (;;) {
569 if (slen <= 0) {
570 mp = mp->m_next;
571 if (!mp)
572 break;
573 rptr = mtod(mp, u_char *);
574 slen = mp->m_len;
575 if (!slen)
576 continue; /* handle 0-length buffers */
577 ilen += slen;
578 }
579
580 slen--;
581 c = *rptr++;
582 fcode = BSD_KEY(ent, c);
583 hval = BSD_HASH(ent, c, hshift);
584 dictp = &db->dict[hval];
585
586 /* Validate and then check the entry. */
587 if (dictp->codem1 >= max_ent)
588 goto nomatch;
589 if (dictp->f.fcode == fcode) {
590 ent = dictp->codem1+1;
591 continue; /* found (prefix,suffix) */
592 }
593
594 /* continue probing until a match or invalid entry */
595 disp = (hval == 0) ? 1 : hval;
596 do {
597 hval += disp;
598 if (hval >= db->hsize)
599 hval -= db->hsize;
600 dictp = &db->dict[hval];
601 if (dictp->codem1 >= max_ent)
602 goto nomatch;
603 } while (dictp->f.fcode != fcode);
604 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
605 continue;
606
607 nomatch:
608 OUTPUT(ent); /* output the prefix */
609
610 /* code -> hashtable */
611 if (max_ent < db->maxmaxcode) {
612 struct bsd_dict *dictp2;
613 /* expand code size if needed */
614 if (max_ent >= MAXCODE(n_bits))
615 db->n_bits = ++n_bits;
616
617 /* Invalidate old hash table entry using
618 * this code, and then take it over.
619 */
620 dictp2 = &db->dict[max_ent+1];
621 if (db->dict[dictp2->cptr].codem1 == max_ent)
622 db->dict[dictp2->cptr].codem1 = BADCODEM1;
623 dictp2->cptr = hval;
624 dictp->codem1 = max_ent;
625 dictp->f.fcode = fcode;
626
627 db->max_ent = ++max_ent;
628 }
629 ent = c;
630 }
631
632 OUTPUT(ent); /* output the last code */
633 db->bytes_out += olen;
634 db->in_count += ilen;
635 if (bitno < 32)
636 ++db->bytes_out; /* count complete bytes */
637
638 if (bsd_check(db))
639 OUTPUT(CLEAR); /* do not count the CLEAR */
640
641 /*
642 * Pad dribble bits of last code with ones.
643 * Do not emit a completely useless byte of ones.
644 */
645 if (bitno != 32)
646 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
647
648 if (m != NULL) {
649 m->m_len = wptr - mtod(m, u_char *);
650 m->m_next = NULL;
651 }
652
653 /*
654 * Increase code size if we would have without the packet
655 * boundary and as the decompressor will.
656 */
657 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
658 db->n_bits++;
659
660 db->uncomp_bytes += ilen;
661 ++db->uncomp_count;
662 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
663 /* throw away the compressed stuff if it is longer than uncompressed */
664 if (*mret != NULL) {
665 m_freem(*mret);
666 *mret = NULL;
667 }
668 ++db->incomp_count;
669 db->incomp_bytes += ilen;
670 } else {
671 ++db->comp_count;
672 db->comp_bytes += olen + BSD_OVHD;
673 }
674
675 return olen + PPP_HDRLEN + BSD_OVHD;
676#undef OUTPUT
677#undef PUTBYTE
678}
679
680
681/*
682 * Update the "BSD Compress" dictionary on the receiver for
683 * incompressible data by pretending to compress the incoming data.
684 */
685static void
686bsd_incomp(state, dmsg)
687 void *state;
688 struct mbuf *dmsg;
689{
690 struct bsd_db *db = (struct bsd_db *) state;
691 u_int hshift = db->hshift;
692 u_int max_ent = db->max_ent;
693 u_int n_bits = db->n_bits;
694 struct bsd_dict *dictp;
695 u_int32_t fcode;
696 u_char c;
697 u_int32_t hval, disp;
698 int slen, ilen;
699 u_int bitno = 7;
700 u_char *rptr;
701 u_int ent;
702
703 /*
704 * If the protocol is not in the range we're interested in,
705 * just return without looking at the packet. If it is,
706 * the protocol becomes the first byte to "compress".
707 */
708 rptr = mtod(dmsg, u_char *);
709 ent = PPP_PROTOCOL(rptr);
710 if (ent < 0x21 || ent > 0xf9)
711 return;
712
713 db->seqno++;
714 ilen = 1; /* count the protocol as 1 byte */
715 rptr += PPP_HDRLEN;
716 slen = dmsg->m_len - PPP_HDRLEN;
717 for (;;) {
718 if (slen <= 0) {
719 dmsg = dmsg->m_next;
720 if (!dmsg)
721 break;
722 rptr = mtod(dmsg, u_char *);
723 slen = dmsg->m_len;
724 continue;
725 }
726 ilen += slen;
727
728 do {
729 c = *rptr++;
730 fcode = BSD_KEY(ent, c);
731 hval = BSD_HASH(ent, c, hshift);
732 dictp = &db->dict[hval];
733
734 /* validate and then check the entry */
735 if (dictp->codem1 >= max_ent)
736 goto nomatch;
737 if (dictp->f.fcode == fcode) {
738 ent = dictp->codem1+1;
739 continue; /* found (prefix,suffix) */
740 }
741
742 /* continue probing until a match or invalid entry */
743 disp = (hval == 0) ? 1 : hval;
744 do {
745 hval += disp;
746 if (hval >= db->hsize)
747 hval -= db->hsize;
748 dictp = &db->dict[hval];
749 if (dictp->codem1 >= max_ent)
750 goto nomatch;
751 } while (dictp->f.fcode != fcode);
752 ent = dictp->codem1+1;
753 continue; /* finally found (prefix,suffix) */
754
755 nomatch: /* output (count) the prefix */
756 bitno += n_bits;
757
758 /* code -> hashtable */
759 if (max_ent < db->maxmaxcode) {
760 struct bsd_dict *dictp2;
761 /* expand code size if needed */
762 if (max_ent >= MAXCODE(n_bits))
763 db->n_bits = ++n_bits;
764
765 /* Invalidate previous hash table entry
766 * assigned this code, and then take it over.
767 */
768 dictp2 = &db->dict[max_ent+1];
769 if (db->dict[dictp2->cptr].codem1 == max_ent)
770 db->dict[dictp2->cptr].codem1 = BADCODEM1;
771 dictp2->cptr = hval;
772 dictp->codem1 = max_ent;
773 dictp->f.fcode = fcode;
774
775 db->max_ent = ++max_ent;
776 db->lens[max_ent] = db->lens[ent]+1;
777 }
778 ent = c;
779 } while (--slen != 0);
780 }
781 bitno += n_bits; /* output (count) the last code */
782 db->bytes_out += bitno/8;
783 db->in_count += ilen;
784 (void)bsd_check(db);
785
786 ++db->incomp_count;
787 db->incomp_bytes += ilen;
788 ++db->uncomp_count;
789 db->uncomp_bytes += ilen;
790
791 /* Increase code size if we would have without the packet
792 * boundary and as the decompressor will.
793 */
794 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
795 db->n_bits++;
796}
797
798
799/*
800 * Decompress "BSD Compress".
801 *
802 * Because of patent problems, we return DECOMP_ERROR for errors
803 * found by inspecting the input data and for system problems, but
804 * DECOMP_FATALERROR for any errors which could possibly be said to
805 * be being detected "after" decompression. For DECOMP_ERROR,
806 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
807 * infringing a patent of Motorola's if we do, so we take CCP down
808 * instead.
809 *
810 * Given that the frame has the correct sequence number and a good FCS,
811 * errors such as invalid codes in the input most likely indicate a
812 * bug, so we return DECOMP_FATALERROR for them in order to turn off
813 * compression, even though they are detected by inspecting the input.
814 */
815int
816bsd_decompress(state, cmp, dmpp)
817 void *state;
818 struct mbuf *cmp, **dmpp;
819{
820 struct bsd_db *db = (struct bsd_db *) state;
821 u_int max_ent = db->max_ent;
822 u_int32_t accm = 0;
823 u_int bitno = 32; /* 1st valid bit in accm */
824 u_int n_bits = db->n_bits;
825 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
826 struct bsd_dict *dictp;
827 int explen, i, seq, len;
828 u_int incode, oldcode, finchar;
829 u_char *p, *rptr, *wptr;
830 struct mbuf *m, *dmp, *mret;
831 int adrs, ctrl, ilen;
832 int space, codelen, extra;
833
834 /*
835 * Save the address/control from the PPP header
836 * and then get the sequence number.
837 */
838 *dmpp = NULL;
839 rptr = mtod(cmp, u_char *);
840 adrs = PPP_ADDRESS(rptr);
841 ctrl = PPP_CONTROL(rptr);
842 rptr += PPP_HDRLEN;
843 len = cmp->m_len - PPP_HDRLEN;
844 seq = 0;
845 for (i = 0; i < 2; ++i) {
846 while (len <= 0) {
847 cmp = cmp->m_next;
848 if (cmp == NULL)
849 return DECOMP_ERROR;
850 rptr = mtod(cmp, u_char *);
851 len = cmp->m_len;
852 }
853 seq = (seq << 8) + *rptr++;
854 --len;
855 }
856
857 /*
858 * Check the sequence number and give up if it differs from
859 * the value we're expecting.
860 */
861 if (seq != db->seqno) {
862 if (db->debug)
863 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
864 db->unit, seq, db->seqno - 1);
865 return DECOMP_ERROR;
866 }
867 ++db->seqno;
868
869 /*
870 * Allocate one mbuf to start with.
871 */
872 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
873 if (dmp == NULL)
874 return DECOMP_ERROR;
875 mret = dmp;
876 dmp->m_len = 0;
877 dmp->m_next = NULL;
878 MCLGET(dmp, M_DONTWAIT);
879 dmp->m_data += db->hdrlen;
880 wptr = mtod(dmp, u_char *);
881 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
882
883 /*
884 * Fill in the ppp header, but not the last byte of the protocol
885 * (that comes from the decompressed data).
886 */
887 wptr[0] = adrs;
888 wptr[1] = ctrl;
889 wptr[2] = 0;
890 wptr += PPP_HDRLEN - 1;
891
892 ilen = len;
893 oldcode = CLEAR;
894 explen = 0;
895 for (;;) {
896 if (len == 0) {
897 cmp = cmp->m_next;
898 if (!cmp) /* quit at end of message */
899 break;
900 rptr = mtod(cmp, u_char *);
901 len = cmp->m_len;
902 ilen += len;
903 continue; /* handle 0-length buffers */
904 }
905
906 /*
907 * Accumulate bytes until we have a complete code.
908 * Then get the next code, relying on the 32-bit,
909 * unsigned accm to mask the result.
910 */
911 bitno -= 8;
912 accm |= *rptr++ << bitno;
913 --len;
914 if (tgtbitno < bitno)
915 continue;
916 incode = accm >> tgtbitno;
917 accm <<= n_bits;
918 bitno += n_bits;
919
920 if (incode == CLEAR) {
921 /*
922 * The dictionary must only be cleared at
923 * the end of a packet. But there could be an
924 * empty mbuf at the end.
925 */
926 if (len > 0 || cmp->m_next != NULL) {
927 while ((cmp = cmp->m_next) != NULL)
928 len += cmp->m_len;
929 if (len > 0) {
930 m_freem(mret);
931 if (db->debug)
932 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
933 return DECOMP_FATALERROR; /* probably a bug */
934 }
935 }
936 bsd_clear(db);
937 explen = ilen = 0;
938 break;
939 }
940
941 if (incode > max_ent + 2 || incode > db->maxmaxcode
942 || (incode > max_ent && oldcode == CLEAR)) {
943 m_freem(mret);
944 if (db->debug) {
945 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
946 db->unit, incode, oldcode);
947 printf("max_ent=0x%x explen=%d seqno=%d\n",
948 max_ent, explen, db->seqno);
949 }
950 return DECOMP_FATALERROR; /* probably a bug */
951 }
952
953 /* Special case for KwKwK string. */
954 if (incode > max_ent) {
955 finchar = oldcode;
956 extra = 1;
957 } else {
958 finchar = incode;
959 extra = 0;
960 }
961
962 codelen = db->lens[finchar];
963 explen += codelen + extra;
964 if (explen > db->mru + 1) {
965 m_freem(mret);
966 if (db->debug) {
967 printf("bsd_decomp%d: ran out of mru\n", db->unit);
968#ifdef DEBUG
969 while ((cmp = cmp->m_next) != NULL)
970 len += cmp->m_len;
971 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
972 len, finchar, codelen, explen);
973#endif
974 }
975 return DECOMP_FATALERROR;
976 }
977
978 /*
979 * For simplicity, the decoded characters go in a single mbuf,
980 * so we allocate a single extra cluster mbuf if necessary.
981 */
982 if ((space -= codelen + extra) < 0) {
983 dmp->m_len = wptr - mtod(dmp, u_char *);
984 MGET(m, M_DONTWAIT, MT_DATA);
985 if (m == NULL) {
986 m_freem(mret);
987 return DECOMP_ERROR;
988 }
989 m->m_len = 0;
990 m->m_next = NULL;
991 dmp->m_next = m;
992 MCLGET(m, M_DONTWAIT);
993 space = M_TRAILINGSPACE(m) - (codelen + extra);
994 if (space < 0) {
995 /* now that's what I call *compression*. */
996 m_freem(mret);
997 return DECOMP_ERROR;
998 }
999 dmp = m;
1000 wptr = mtod(dmp, u_char *);
1001 }
1002
1003 /*
1004 * Decode this code and install it in the decompressed buffer.
1005 */
1006 p = (wptr += codelen);
1007 while (finchar > LAST) {
1008 dictp = &db->dict[db->dict[finchar].cptr];
1009#ifdef DEBUG
1010 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1011 goto bad;
1012#endif
1013 *--p = dictp->f.hs.suffix;
1014 finchar = dictp->f.hs.prefix;
1015 }
1016 *--p = finchar;
1017
1018#ifdef DEBUG
1019 if (--codelen != 0)
1020 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1021 db->unit, codelen, incode, max_ent);
1022#endif
1023
1024 if (extra) /* the KwKwK case again */
1025 *wptr++ = finchar;
1026
1027 /*
1028 * If not first code in a packet, and
1029 * if not out of code space, then allocate a new code.
1030 *
1031 * Keep the hash table correct so it can be used
1032 * with uncompressed packets.
1033 */
1034 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1035 struct bsd_dict *dictp2;
1036 u_int32_t fcode;
1037 u_int32_t hval, disp;
1038
1039 fcode = BSD_KEY(oldcode,finchar);
1040 hval = BSD_HASH(oldcode,finchar,db->hshift);
1041 dictp = &db->dict[hval];
1042
1043 /* look for a free hash table entry */
1044 if (dictp->codem1 < max_ent) {
1045 disp = (hval == 0) ? 1 : hval;
1046 do {
1047 hval += disp;
1048 if (hval >= db->hsize)
1049 hval -= db->hsize;
1050 dictp = &db->dict[hval];
1051 } while (dictp->codem1 < max_ent);
1052 }
1053
1054 /*
1055 * Invalidate previous hash table entry
1056 * assigned this code, and then take it over
1057 */
1058 dictp2 = &db->dict[max_ent+1];
1059 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1060 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1061 }
1062 dictp2->cptr = hval;
1063 dictp->codem1 = max_ent;
1064 dictp->f.fcode = fcode;
1065
1066 db->max_ent = ++max_ent;
1067 db->lens[max_ent] = db->lens[oldcode]+1;
1068
1069 /* Expand code size if needed. */
1070 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1071 db->n_bits = ++n_bits;
1072 tgtbitno = 32-n_bits;
1073 }
1074 }
1075 oldcode = incode;
1076 }
1077 dmp->m_len = wptr - mtod(dmp, u_char *);
1078
1079 /*
1080 * Keep the checkpoint right so that incompressible packets
1081 * clear the dictionary at the right times.
1082 */
1083 db->bytes_out += ilen;
1084 db->in_count += explen;
1085 if (bsd_check(db) && db->debug) {
1086 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1087 db->unit);
1088 }
1089
1090 ++db->comp_count;
1091 db->comp_bytes += ilen + BSD_OVHD;
1092 ++db->uncomp_count;
1093 db->uncomp_bytes += explen;
1094
1095 *dmpp = mret;
1096 return DECOMP_OK;
1097
1098#ifdef DEBUG
1099 bad:
1100 if (codelen <= 0) {
1101 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1102 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1103 incode, finchar, db->dict[finchar].cptr, max_ent);
1104 } else if (dictp->codem1 != finchar-1) {
1105 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1106 db->unit, incode, finchar);
1107 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1108 db->dict[finchar].cptr, dictp->codem1);
1109 }
1110 m_freem(mret);
1111 return DECOMP_FATALERROR;
1112#endif /* DEBUG */
1113}
1114#endif /* DO_BSD_COMPRESS */