1/* $NetBSD: bsd-comp.c,v 1.22 2016/08/06 22:38:18 pgoyette 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 1.22 2016/08/06 22:38:18 pgoyette Exp $");
45
46#include <sys/param.h>
47#include <sys/systm.h>
48#include <sys/mbuf.h>
49#include <sys/socket.h>
50#include <sys/module.h>
51#include <net/if.h>
52#include <net/if_types.h>
53#include <net/ppp_defs.h>
54#include <net/if_ppp.h>
55
56#define PACKETPTR struct mbuf *
57#include <net/ppp-comp.h>
58
59#if DO_BSD_COMPRESS
60/*
61 * PPP "BSD compress" compression
62 * The differences between this compression and the classic BSD LZW
63 * source are obvious from the requirement that the classic code worked
64 * with files while this handles arbitrarily long streams that
65 * are broken into packets. They are:
66 *
67 * When the code size expands, a block of junk is not emitted by
68 * the compressor and not expected by the decompressor.
69 *
70 * New codes are not necessarily assigned every time an old
71 * code is output by the compressor. This is because a packet
72 * end forces a code to be emitted, but does not imply that a
73 * new sequence has been seen.
74 *
75 * The compression ratio is checked at the first end of a packet
76 * after the appropriate gap. Besides simplifying and speeding
77 * things up, this makes it more likely that the transmitter
78 * and receiver will agree when the dictionary is cleared when
79 * compression is not going well.
80 */
81
82/*
83 * A dictionary for doing BSD compress.
84 */
85struct bsd_db {
86 int totlen; /* length of this structure */
87 u_int hsize; /* size of the hash table */
88 u_char hshift; /* used in hash function */
89 u_char n_bits; /* current bits/code */
90 u_char maxbits;
91 u_char debug;
92 u_char unit;
93 uint16_t seqno; /* sequence # of next packet */
94 u_int hdrlen; /* header length to preallocate */
95 u_int mru;
96 u_int maxmaxcode; /* largest valid code */
97 u_int max_ent; /* largest code in use */
98 u_int in_count; /* uncompressed bytes, aged */
99 u_int bytes_out; /* compressed bytes, aged */
100 u_int ratio; /* recent compression ratio */
101 u_int checkpoint; /* when to next check the ratio */
102 u_int clear_count; /* times dictionary cleared */
103 u_int incomp_count; /* incompressible packets */
104 u_int incomp_bytes; /* incompressible bytes */
105 u_int uncomp_count; /* uncompressed packets */
106 u_int uncomp_bytes; /* uncompressed bytes */
107 u_int comp_count; /* compressed packets */
108 u_int comp_bytes; /* compressed bytes */
109 uint16_t *lens; /* array of lengths of codes */
110 struct bsd_dict {
111 union { /* hash value */
112 uint32_t fcode;
113 struct {
114#if BYTE_ORDER == LITTLE_ENDIAN
115 uint16_t prefix; /* preceding code */
116 u_char suffix; /* last character of new code */
117 u_char pad;
118#else
119 u_char pad;
120 u_char suffix; /* last character of new code */
121 uint16_t prefix; /* preceding code */
122#endif
123 } hs;
124 } f;
125 uint16_t codem1; /* output of hash table -1 */
126 uint16_t cptr; /* map code to hash table entry */
127 } dict[1];
128};
129
130#define BSD_OVHD 2 /* BSD compress overhead/packet */
131#define BSD_INIT_BITS BSD_MIN_BITS
132
133static void *bsd_comp_alloc(u_char *options, int opt_len);
134static void *bsd_decomp_alloc(u_char *options, int opt_len);
135static void bsd_free(void *state);
136static int bsd_comp_init(void *state, u_char *options, int opt_len,
137 int unit, int hdrlen, int debug);
138static int bsd_decomp_init(void *state, u_char *options, int opt_len,
139 int unit, int hdrlen, int mru, int debug);
140static int bsd_compress(void *state, struct mbuf **mret,
141 struct mbuf *mp, int slen, int maxolen);
142static void bsd_incomp(void *state, struct mbuf *dmsg);
143static int bsd_decompress(void *state, struct mbuf *cmp,
144 struct mbuf **dmpp);
145static void bsd_reset(void *state);
146static void bsd_comp_stats(void *state, struct compstat *stats);
147
148/*
149 * Procedures exported to if_ppp.c.
150 */
151static struct compressor ppp_bsd_compress = {
152 .compress_proto = CI_BSD_COMPRESS,
153 .comp_alloc = bsd_comp_alloc,
154 .comp_free = bsd_free,
155 .comp_init = bsd_comp_init,
156 .comp_reset = bsd_reset,
157 .compress = bsd_compress,
158 .comp_stat = bsd_comp_stats,
159 .decomp_alloc = bsd_decomp_alloc,
160 .decomp_free = bsd_free,
161 .decomp_init = bsd_decomp_init,
162 .decomp_reset = bsd_reset,
163 .decompress = bsd_decompress,
164 .incomp = bsd_incomp,
165 .decomp_stat = bsd_comp_stats,
166};
167
168/*
169 * the next two codes should not be changed lightly, as they must not
170 * lie within the contiguous general code space.
171 */
172#define CLEAR 256 /* table clear output code */
173#define FIRST 257 /* first free entry */
174#define LAST 255
175
176#define MAXCODE(b) ((1 << (b)) - 1)
177#define BADCODEM1 MAXCODE(BSD_MAX_BITS)
178
179#define BSD_HASH(prefix,suffix,hshift) ((((uint32_t)(suffix)) << (hshift)) \
180 ^ (uint32_t)(prefix))
181#define BSD_KEY(prefix,suffix) ((((uint32_t)(suffix)) << 16) \
182 + (uint32_t)(prefix))
183
184#define CHECK_GAP 10000 /* Ratio check interval */
185
186#define RATIO_SCALE_LOG 8
187#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
188#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
189
190static void bsd_clear(struct bsd_db *);
191static int bsd_check(struct bsd_db *);
192static void *bsd_alloc(u_char *, int, int);
193static int bsd_init(struct bsd_db *, u_char *, int, int, int, int,
194 int, int);
195
196/*
197 * clear the dictionary
198 */
199static void
200bsd_clear(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 */
224static int /* 1=output CLEAR */
225bsd_check(struct bsd_db *db)
226{
227 u_int new_ratio;
228
229 if (db->in_count >= db->checkpoint) {
230 /* age the ratio by limiting the size of the counts */
231 if (db->in_count >= RATIO_MAX
232 || db->bytes_out >= RATIO_MAX) {
233 db->in_count -= db->in_count/4;
234 db->bytes_out -= db->bytes_out/4;
235 }
236
237 db->checkpoint = db->in_count + CHECK_GAP;
238
239 if (db->max_ent >= db->maxmaxcode) {
240 /* Reset the dictionary only if the ratio is worse,
241 * or if it looks as if it has been poisoned
242 * by incompressible data.
243 *
244 * This does not overflow, because
245 * db->in_count <= RATIO_MAX.
246 */
247 new_ratio = db->in_count << RATIO_SCALE_LOG;
248 if (db->bytes_out != 0)
249 new_ratio /= db->bytes_out;
250
251 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
252 bsd_clear(db);
253 return 1;
254 }
255 db->ratio = new_ratio;
256 }
257 }
258 return 0;
259}
260
261/*
262 * Return statistics.
263 */
264static void
265bsd_comp_stats(void *state, struct compstat *stats)
266{
267 struct bsd_db *db = (struct bsd_db *) state;
268 u_int out;
269
270 stats->unc_bytes = db->uncomp_bytes;
271 stats->unc_packets = db->uncomp_count;
272 stats->comp_bytes = db->comp_bytes;
273 stats->comp_packets = db->comp_count;
274 stats->inc_bytes = db->incomp_bytes;
275 stats->inc_packets = db->incomp_count;
276 stats->ratio = db->in_count;
277 out = db->bytes_out;
278 if (stats->ratio <= 0x7fffff)
279 stats->ratio <<= 8;
280 else
281 out >>= 8;
282 if (out != 0)
283 stats->ratio /= out;
284}
285
286/*
287 * Reset state, as on a CCP ResetReq.
288 */
289static void
290bsd_reset(void *state)
291{
292 struct bsd_db *db = (struct bsd_db *) state;
293
294 db->seqno = 0;
295 bsd_clear(db);
296 db->clear_count = 0;
297}
298
299/*
300 * Allocate space for a (de) compressor.
301 */
302static void *
303bsd_alloc(u_char *options, int opt_len, int decomp)
304{
305 int bits;
306 u_int newlen, hsize, hshift, maxmaxcode;
307 struct bsd_db *db;
308
309 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
310 || options[1] != CILEN_BSD_COMPRESS
311 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
312 return NULL;
313 bits = BSD_NBITS(options[2]);
314 switch (bits) {
315 case 9: /* needs 82152 for both directions */
316 case 10: /* needs 84144 */
317 case 11: /* needs 88240 */
318 case 12: /* needs 96432 */
319 hsize = 5003;
320 hshift = 4;
321 break;
322 case 13: /* needs 176784 */
323 hsize = 9001;
324 hshift = 5;
325 break;
326 case 14: /* needs 353744 */
327 hsize = 18013;
328 hshift = 6;
329 break;
330 case 15: /* needs 691440 */
331 hsize = 35023;
332 hshift = 7;
333 break;
334 case 16: /* needs 1366160--far too much, */
335 /* hsize = 69001; */ /* and 69001 is too big for cptr */
336 /* hshift = 8; */ /* in struct bsd_db */
337 /* break; */
338 default:
339 return NULL;
340 }
341
342 maxmaxcode = MAXCODE(bits);
343 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
344 db = malloc(newlen, M_DEVBUF, M_NOWAIT|M_ZERO);
345 if (!db)
346 return NULL;
347
348 if (!decomp) {
349 db->lens = NULL;
350 } else {
351 db->lens = malloc((maxmaxcode+1) * sizeof(db->lens[0]),
352 M_DEVBUF, M_NOWAIT);
353 if (!db->lens) {
354 free(db, M_DEVBUF);
355 return NULL;
356 }
357 }
358
359 db->totlen = newlen;
360 db->hsize = hsize;
361 db->hshift = hshift;
362 db->maxmaxcode = maxmaxcode;
363 db->maxbits = bits;
364
365 return (void *) db;
366}
367
368static void
369bsd_free(void *state)
370{
371 struct bsd_db *db = (struct bsd_db *) state;
372
373 if (db->lens)
374 free(db->lens, M_DEVBUF);
375 free(db, M_DEVBUF);
376}
377
378static void *
379bsd_comp_alloc(u_char *options, int opt_len)
380{
381 return bsd_alloc(options, opt_len, 0);
382}
383
384static void *
385bsd_decomp_alloc(u_char *options, int opt_len)
386{
387 return bsd_alloc(options, opt_len, 1);
388}
389
390/*
391 * Initialize the database.
392 */
393static int
394bsd_init(struct bsd_db *db, u_char *options, int opt_len, int unit, int hdrlen,
395 int mru, int debug, int decomp)
396{
397 int i;
398
399 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
400 || options[1] != CILEN_BSD_COMPRESS
401 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
402 || BSD_NBITS(options[2]) != db->maxbits
403 || (decomp && db->lens == NULL))
404 return 0;
405
406 if (decomp) {
407 i = LAST+1;
408 while (i != 0)
409 db->lens[--i] = 1;
410 }
411 i = db->hsize;
412 while (i != 0) {
413 db->dict[--i].codem1 = BADCODEM1;
414 db->dict[i].cptr = 0;
415 }
416
417 db->unit = unit;
418 db->hdrlen = hdrlen;
419 db->mru = mru;
420#ifndef DEBUG
421 if (debug)
422#endif
423 db->debug = 1;
424
425 bsd_reset(db);
426
427 return 1;
428}
429
430static int
431bsd_comp_init(void *state, u_char *options, int opt_len, int unit, int hdrlen,
432 int debug)
433{
434 return bsd_init((struct bsd_db *) state, options, opt_len,
435 unit, hdrlen, 0, debug, 0);
436}
437
438static int
439bsd_decomp_init(void *state, u_char *options, int opt_len, int unit, int hdrlen,
440 int mru, int debug)
441{
442 return bsd_init((struct bsd_db *) state, options, opt_len,
443 unit, hdrlen, mru, debug, 1);
444}
445
446
447/*
448 * compress a packet
449 * One change from the BSD compress command is that when the
450 * code size expands, we do not output a bunch of padding.
451 */
452int /* new slen */
453bsd_compress(void *state,
454 struct mbuf **mret /* return compressed mbuf chain here */,
455 struct mbuf *mp /* from here */,
456 int slen, int maxolen)
457{
458 struct bsd_db *db = (struct bsd_db *) state;
459 int hshift = db->hshift;
460 u_int max_ent = db->max_ent;
461 u_int n_bits = db->n_bits;
462 u_int bitno = 32;
463 uint32_t accm = 0, fcode;
464 struct bsd_dict *dictp;
465 u_char c;
466 int hval, disp, ent, ilen;
467 u_char *rptr, *wptr;
468 u_char *cp_end;
469 int olen;
470 struct mbuf *m;
471
472#define PUTBYTE(v) { \
473 ++olen; \
474 if (wptr) { \
475 *wptr++ = (v); \
476 if (wptr >= cp_end) { \
477 m->m_len = wptr - mtod(m, u_char *); \
478 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
479 m = m->m_next; \
480 if (m) { \
481 m->m_len = 0; \
482 if (maxolen - olen > MLEN) \
483 MCLGET(m, M_DONTWAIT); \
484 wptr = mtod(m, u_char *); \
485 cp_end = wptr + M_TRAILINGSPACE(m); \
486 } else \
487 wptr = NULL; \
488 } \
489 } \
490}
491
492#define OUTPUT(ent) { \
493 bitno -= n_bits; \
494 accm |= ((ent) << bitno); \
495 do { \
496 PUTBYTE(accm >> 24); \
497 accm <<= 8; \
498 bitno += 8; \
499 } while (bitno <= 24); \
500}
501
502 /*
503 * If the protocol is not in the range we're interested in,
504 * just return without compressing the packet. If it is,
505 * the protocol becomes the first byte to compress.
506 */
507 rptr = mtod(mp, u_char *);
508 ent = PPP_PROTOCOL(rptr);
509 if (ent < 0x21 || ent > 0xf9) {
510 *mret = NULL;
511 return slen;
512 }
513
514 /* Don't generate compressed packets which are larger than
515 the uncompressed packet. */
516 if (maxolen > slen)
517 maxolen = slen;
518
519 /* Allocate one mbuf to start with. */
520 MGET(m, M_DONTWAIT, MT_DATA);
521 *mret = m;
522 if (m != NULL) {
523 m->m_len = 0;
524 if (maxolen + db->hdrlen > MLEN)
525 MCLGET(m, M_DONTWAIT);
526 m->m_data += db->hdrlen;
527 wptr = mtod(m, u_char *);
528 cp_end = wptr + M_TRAILINGSPACE(m);
529 } else
530 wptr = cp_end = NULL;
531
532 /*
533 * Copy the PPP header over, changing the protocol,
534 * and install the 2-byte packet sequence number.
535 */
536 if (wptr) {
537 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
538 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
539 *wptr++ = 0; /* change the protocol */
540 *wptr++ = PPP_COMP;
541 *wptr++ = db->seqno >> 8;
542 *wptr++ = db->seqno;
543 }
544 ++db->seqno;
545
546 olen = 0;
547 rptr += PPP_HDRLEN;
548 slen = mp->m_len - PPP_HDRLEN;
549 ilen = slen + 1;
550 for (;;) {
551 if (slen <= 0) {
552 mp = mp->m_next;
553 if (!mp)
554 break;
555 rptr = mtod(mp, u_char *);
556 slen = mp->m_len;
557 if (!slen)
558 continue; /* handle 0-length buffers */
559 ilen += slen;
560 }
561
562 slen--;
563 c = *rptr++;
564 fcode = BSD_KEY(ent, c);
565 hval = BSD_HASH(ent, c, hshift);
566 dictp = &db->dict[hval];
567
568 /* Validate and then check the entry. */
569 if (dictp->codem1 >= max_ent)
570 goto nomatch;
571 if (dictp->f.fcode == fcode) {
572 ent = dictp->codem1+1;
573 continue; /* found (prefix,suffix) */
574 }
575
576 /* continue probing until a match or invalid entry */
577 disp = (hval == 0) ? 1 : hval;
578 do {
579 hval += disp;
580 if (hval >= db->hsize)
581 hval -= db->hsize;
582 dictp = &db->dict[hval];
583 if (dictp->codem1 >= max_ent)
584 goto nomatch;
585 } while (dictp->f.fcode != fcode);
586 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
587 continue;
588
589 nomatch:
590 OUTPUT(ent); /* output the prefix */
591
592 /* code -> hashtable */
593 if (max_ent < db->maxmaxcode) {
594 struct bsd_dict *dictp2;
595 /* expand code size if needed */
596 if (max_ent >= MAXCODE(n_bits))
597 db->n_bits = ++n_bits;
598
599 /* Invalidate old hash table entry using
600 * this code, and then take it over.
601 */
602 dictp2 = &db->dict[max_ent+1];
603 if (db->dict[dictp2->cptr].codem1 == max_ent)
604 db->dict[dictp2->cptr].codem1 = BADCODEM1;
605 dictp2->cptr = hval;
606 dictp->codem1 = max_ent;
607 dictp->f.fcode = fcode;
608
609 db->max_ent = ++max_ent;
610 }
611 ent = c;
612 }
613
614 OUTPUT(ent); /* output the last code */
615 db->bytes_out += olen;
616 db->in_count += ilen;
617 if (bitno < 32)
618 ++db->bytes_out; /* count complete bytes */
619
620 if (bsd_check(db))
621 OUTPUT(CLEAR); /* do not count the CLEAR */
622
623 /*
624 * Pad dribble bits of last code with ones.
625 * Do not emit a completely useless byte of ones.
626 */
627 if (bitno != 32)
628 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
629
630 if (m != NULL) {
631 m->m_len = wptr - mtod(m, u_char *);
632 m->m_next = NULL;
633 }
634
635 /*
636 * Increase code size if we would have without the packet
637 * boundary and as the decompressor will.
638 */
639 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
640 db->n_bits++;
641
642 db->uncomp_bytes += ilen;
643 ++db->uncomp_count;
644 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
645 /* throw away the compressed stuff if it is longer than uncompressed */
646 if (*mret != NULL) {
647 m_freem(*mret);
648 *mret = NULL;
649 }
650 ++db->incomp_count;
651 db->incomp_bytes += ilen;
652 } else {
653 ++db->comp_count;
654 db->comp_bytes += olen + BSD_OVHD;
655 }
656
657 return olen + PPP_HDRLEN + BSD_OVHD;
658#undef OUTPUT
659#undef PUTBYTE
660}
661
662
663/*
664 * Update the "BSD Compress" dictionary on the receiver for
665 * incompressible data by pretending to compress the incoming data.
666 */
667static void
668bsd_incomp(void *state, struct mbuf *dmsg)
669{
670 struct bsd_db *db = (struct bsd_db *) state;
671 u_int hshift = db->hshift;
672 u_int max_ent = db->max_ent;
673 u_int n_bits = db->n_bits;
674 struct bsd_dict *dictp;
675 uint32_t fcode;
676 u_char c;
677 uint32_t hval, disp;
678 int slen, ilen;
679 u_int bitno = 7;
680 u_char *rptr;
681 u_int ent;
682
683 /*
684 * If the protocol is not in the range we're interested in,
685 * just return without looking at the packet. If it is,
686 * the protocol becomes the first byte to "compress".
687 */
688 rptr = mtod(dmsg, u_char *);
689 ent = PPP_PROTOCOL(rptr);
690 if (ent < 0x21 || ent > 0xf9)
691 return;
692
693 db->seqno++;
694 ilen = 1; /* count the protocol as 1 byte */
695 rptr += PPP_HDRLEN;
696 slen = dmsg->m_len - PPP_HDRLEN;
697 for (;;) {
698 if (slen <= 0) {
699 dmsg = dmsg->m_next;
700 if (!dmsg)
701 break;
702 rptr = mtod(dmsg, u_char *);
703 slen = dmsg->m_len;
704 continue;
705 }
706 ilen += slen;
707
708 do {
709 c = *rptr++;
710 fcode = BSD_KEY(ent, c);
711 hval = BSD_HASH(ent, c, hshift);
712 dictp = &db->dict[hval];
713
714 /* validate and then check the entry */
715 if (dictp->codem1 >= max_ent)
716 goto nomatch;
717 if (dictp->f.fcode == fcode) {
718 ent = dictp->codem1+1;
719 continue; /* found (prefix,suffix) */
720 }
721
722 /* continue probing until a match or invalid entry */
723 disp = (hval == 0) ? 1 : hval;
724 do {
725 hval += disp;
726 if (hval >= db->hsize)
727 hval -= db->hsize;
728 dictp = &db->dict[hval];
729 if (dictp->codem1 >= max_ent)
730 goto nomatch;
731 } while (dictp->f.fcode != fcode);
732 ent = dictp->codem1+1;
733 continue; /* finally found (prefix,suffix) */
734
735 nomatch: /* output (count) the prefix */
736 bitno += n_bits;
737
738 /* code -> hashtable */
739 if (max_ent < db->maxmaxcode) {
740 struct bsd_dict *dictp2;
741 /* expand code size if needed */
742 if (max_ent >= MAXCODE(n_bits))
743 db->n_bits = ++n_bits;
744
745 /* Invalidate previous hash table entry
746 * assigned this code, and then take it over.
747 */
748 dictp2 = &db->dict[max_ent+1];
749 if (db->dict[dictp2->cptr].codem1 == max_ent)
750 db->dict[dictp2->cptr].codem1 = BADCODEM1;
751 dictp2->cptr = hval;
752 dictp->codem1 = max_ent;
753 dictp->f.fcode = fcode;
754
755 db->max_ent = ++max_ent;
756 db->lens[max_ent] = db->lens[ent]+1;
757 }
758 ent = c;
759 } while (--slen != 0);
760 }
761 bitno += n_bits; /* output (count) the last code */
762 db->bytes_out += bitno/8;
763 db->in_count += ilen;
764 (void)bsd_check(db);
765
766 ++db->incomp_count;
767 db->incomp_bytes += ilen;
768 ++db->uncomp_count;
769 db->uncomp_bytes += ilen;
770
771 /* Increase code size if we would have without the packet
772 * boundary and as the decompressor will.
773 */
774 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
775 db->n_bits++;
776}
777
778
779/*
780 * Decompress "BSD Compress".
781 *
782 * Because of patent problems, we return DECOMP_ERROR for errors
783 * found by inspecting the input data and for system problems, but
784 * DECOMP_FATALERROR for any errors which could possibly be said to
785 * be being detected "after" decompression. For DECOMP_ERROR,
786 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
787 * infringing a patent of Motorola's if we do, so we take CCP down
788 * instead.
789 *
790 * Given that the frame has the correct sequence number and a good FCS,
791 * errors such as invalid codes in the input most likely indicate a
792 * bug, so we return DECOMP_FATALERROR for them in order to turn off
793 * compression, even though they are detected by inspecting the input.
794 */
795int
796bsd_decompress(void *state, struct mbuf *cmp, struct mbuf **dmpp)
797{
798 struct bsd_db *db = (struct bsd_db *) state;
799 u_int max_ent = db->max_ent;
800 uint32_t accm = 0;
801 u_int bitno = 32; /* 1st valid bit in accm */
802 u_int n_bits = db->n_bits;
803 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
804 struct bsd_dict *dictp;
805 int explen, i, seq, len;
806 u_int incode, oldcode, finchar;
807 u_char *p, *rptr, *wptr;
808 struct mbuf *m, *dmp, *mret;
809 int adrs, ctrl, ilen;
810 int space, codelen, extra;
811
812 /*
813 * Save the address/control from the PPP header
814 * and then get the sequence number.
815 */
816 *dmpp = NULL;
817 rptr = mtod(cmp, u_char *);
818 adrs = PPP_ADDRESS(rptr);
819 ctrl = PPP_CONTROL(rptr);
820 rptr += PPP_HDRLEN;
821 len = cmp->m_len - PPP_HDRLEN;
822 seq = 0;
823 for (i = 0; i < 2; ++i) {
824 while (len <= 0) {
825 cmp = cmp->m_next;
826 if (cmp == NULL)
827 return DECOMP_ERROR;
828 rptr = mtod(cmp, u_char *);
829 len = cmp->m_len;
830 }
831 seq = (seq << 8) + *rptr++;
832 --len;
833 }
834
835 /*
836 * Check the sequence number and give up if it differs from
837 * the value we're expecting.
838 */
839 if (seq != db->seqno) {
840 if (db->debug)
841 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
842 db->unit, seq, db->seqno - 1);
843 return DECOMP_ERROR;
844 }
845 ++db->seqno;
846
847 /*
848 * Allocate one mbuf to start with.
849 */
850 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
851 if (dmp == NULL)
852 return DECOMP_ERROR;
853 mret = dmp;
854 dmp->m_len = 0;
855 dmp->m_next = NULL;
856 MCLGET(dmp, M_DONTWAIT);
857 dmp->m_data += db->hdrlen;
858 wptr = mtod(dmp, u_char *);
859 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
860
861 /*
862 * Fill in the ppp header, but not the last byte of the protocol
863 * (that comes from the decompressed data).
864 */
865 wptr[0] = adrs;
866 wptr[1] = ctrl;
867 wptr[2] = 0;
868 wptr += PPP_HDRLEN - 1;
869
870 ilen = len;
871 oldcode = CLEAR;
872 explen = 0;
873 for (;;) {
874 if (len == 0) {
875 cmp = cmp->m_next;
876 if (!cmp) /* quit at end of message */
877 break;
878 rptr = mtod(cmp, u_char *);
879 len = cmp->m_len;
880 ilen += len;
881 continue; /* handle 0-length buffers */
882 }
883
884 /*
885 * Accumulate bytes until we have a complete code.
886 * Then get the next code, relying on the 32-bit,
887 * unsigned accm to mask the result.
888 */
889 bitno -= 8;
890 accm |= *rptr++ << bitno;
891 --len;
892 if (tgtbitno < bitno)
893 continue;
894 incode = accm >> tgtbitno;
895 accm <<= n_bits;
896 bitno += n_bits;
897
898 if (incode == CLEAR) {
899 /*
900 * The dictionary must only be cleared at
901 * the end of a packet. But there could be an
902 * empty mbuf at the end.
903 */
904 if (len > 0 || cmp->m_next != NULL) {
905 while ((cmp = cmp->m_next) != NULL)
906 len += cmp->m_len;
907 if (len > 0) {
908 m_freem(mret);
909 if (db->debug)
910 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
911 return DECOMP_FATALERROR; /* probably a bug */
912 }
913 }
914 bsd_clear(db);
915 explen = ilen = 0;
916 break;
917 }
918
919 if (incode > max_ent + 2 || incode > db->maxmaxcode
920 || (incode > max_ent && oldcode == CLEAR)) {
921 m_freem(mret);
922 if (db->debug) {
923 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
924 db->unit, incode, oldcode);
925 printf("max_ent=0x%x explen=%d seqno=%d\n",
926 max_ent, explen, db->seqno);
927 }
928 return DECOMP_FATALERROR; /* probably a bug */
929 }
930
931 /* Special case for KwKwK string. */
932 if (incode > max_ent) {
933 finchar = oldcode;
934 extra = 1;
935 } else {
936 finchar = incode;
937 extra = 0;
938 }
939
940 codelen = db->lens[finchar];
941 explen += codelen + extra;
942 if (explen > db->mru + 1) {
943 m_freem(mret);
944 if (db->debug) {
945 printf("bsd_decomp%d: ran out of mru\n", db->unit);
946#ifdef DEBUG
947 while ((cmp = cmp->m_next) != NULL)
948 len += cmp->m_len;
949 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
950 len, finchar, codelen, explen);
951#endif
952 }
953 return DECOMP_FATALERROR;
954 }
955
956 /*
957 * For simplicity, the decoded characters go in a single mbuf,
958 * so we allocate a single extra cluster mbuf if necessary.
959 */
960 if ((space -= codelen + extra) < 0) {
961 dmp->m_len = wptr - mtod(dmp, u_char *);
962 MGET(m, M_DONTWAIT, MT_DATA);
963 if (m == NULL) {
964 m_freem(mret);
965 return DECOMP_ERROR;
966 }
967 m->m_len = 0;
968 m->m_next = NULL;
969 dmp->m_next = m;
970 MCLGET(m, M_DONTWAIT);
971 space = M_TRAILINGSPACE(m) - (codelen + extra);
972 if (space < 0) {
973 /* now that's what I call *compression*. */
974 m_freem(mret);
975 return DECOMP_ERROR;
976 }
977 dmp = m;
978 wptr = mtod(dmp, u_char *);
979 }
980
981 /*
982 * Decode this code and install it in the decompressed buffer.
983 */
984 p = (wptr += codelen);
985 while (finchar > LAST) {
986 dictp = &db->dict[db->dict[finchar].cptr];
987#ifdef DEBUG
988 if (--codelen <= 0 || dictp->codem1 != finchar-1)
989 goto bad;
990#endif
991 *--p = dictp->f.hs.suffix;
992 finchar = dictp->f.hs.prefix;
993 }
994 *--p = finchar;
995
996#ifdef DEBUG
997 if (--codelen != 0)
998 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
999 db->unit, codelen, incode, max_ent);
1000#endif
1001
1002 if (extra) /* the KwKwK case again */
1003 *wptr++ = finchar;
1004
1005 /*
1006 * If not first code in a packet, and
1007 * if not out of code space, then allocate a new code.
1008 *
1009 * Keep the hash table correct so it can be used
1010 * with uncompressed packets.
1011 */
1012 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1013 struct bsd_dict *dictp2;
1014 uint32_t fcode;
1015 uint32_t hval, disp;
1016
1017 fcode = BSD_KEY(oldcode,finchar);
1018 hval = BSD_HASH(oldcode,finchar,db->hshift);
1019 dictp = &db->dict[hval];
1020
1021 /* look for a free hash table entry */
1022 if (dictp->codem1 < max_ent) {
1023 disp = (hval == 0) ? 1 : hval;
1024 do {
1025 hval += disp;
1026 if (hval >= db->hsize)
1027 hval -= db->hsize;
1028 dictp = &db->dict[hval];
1029 } while (dictp->codem1 < max_ent);
1030 }
1031
1032 /*
1033 * Invalidate previous hash table entry
1034 * assigned this code, and then take it over
1035 */
1036 dictp2 = &db->dict[max_ent+1];
1037 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1038 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1039 }
1040 dictp2->cptr = hval;
1041 dictp->codem1 = max_ent;
1042 dictp->f.fcode = fcode;
1043
1044 db->max_ent = ++max_ent;
1045 db->lens[max_ent] = db->lens[oldcode]+1;
1046
1047 /* Expand code size if needed. */
1048 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1049 db->n_bits = ++n_bits;
1050 tgtbitno = 32-n_bits;
1051 }
1052 }
1053 oldcode = incode;
1054 }
1055 dmp->m_len = wptr - mtod(dmp, u_char *);
1056
1057 /*
1058 * Keep the checkpoint right so that incompressible packets
1059 * clear the dictionary at the right times.
1060 */
1061 db->bytes_out += ilen;
1062 db->in_count += explen;
1063 if (bsd_check(db) && db->debug) {
1064 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1065 db->unit);
1066 }
1067
1068 ++db->comp_count;
1069 db->comp_bytes += ilen + BSD_OVHD;
1070 ++db->uncomp_count;
1071 db->uncomp_bytes += explen;
1072
1073 *dmpp = mret;
1074 return DECOMP_OK;
1075
1076#ifdef DEBUG
1077 bad:
1078 if (codelen <= 0) {
1079 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1080 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1081 incode, finchar, db->dict[finchar].cptr, max_ent);
1082 } else if (dictp->codem1 != finchar-1) {
1083 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1084 db->unit, incode, finchar);
1085 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1086 db->dict[finchar].cptr, dictp->codem1);
1087 }
1088 m_freem(mret);
1089 return DECOMP_FATALERROR;
1090#endif /* DEBUG */
1091}
1092
1093MODULE(MODULE_CLASS_MISC, ppp_bsdcomp, "if_ppp");
1094
1095static int
1096ppp_bsdcomp_modcmd(modcmd_t cmd, void *arg)
1097{
1098
1099 switch (cmd) {
1100 case MODULE_CMD_INIT:
1101 return ppp_register_compressor(&ppp_bsd_compress, 1);
1102 case MODULE_CMD_FINI:
1103 return ppp_unregister_compressor(&ppp_bsd_compress, 1);
1104 case MODULE_CMD_STAT:
1105 return 0;
1106 default:
1107 return ENOTTY;
1108 }
1109
1110 return ENOTTY;
1111}
1112#endif /* DO_BSD_COMPRESS */
1113