1 /*
2 * BSD compression module
3 *
4 * Patched version for ISDN syncPPP written 1997/1998 by Michael Hipp
5 * The whole module is now SKB based.
6 *
7 * Compile with:
8 * gcc -O2 -I/usr/src/linux/include -D__KERNEL__ -DMODULE -c isdn_bsdcomp.c
9 */
10
11 /*
12 * Original copyright notice:
13 *
14 * Copyright (c) 1985, 1986 The Regents of the University of California.
15 * All rights reserved.
16 *
17 * This code is derived from software contributed to Berkeley by
18 * James A. Woods, derived from original work by Spencer Thomas
19 * and Joseph Orost.
20 *
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
23 * are met:
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
29 * 3. All advertising materials mentioning features or use of this software
30 * must display the following acknowledgement:
31 * This product includes software developed by the University of
32 * California, Berkeley and its contributors.
33 * 4. Neither the name of the University nor the names of its contributors
34 * may be used to endorse or promote products derived from this software
35 * without specific prior written permission.
36 *
37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
47 * SUCH DAMAGE.
48 */
49
50 #ifndef MODULE
51 #error This file must be compiled as a module.
52 #endif
53
54 #include <linux/module.h>
55
56 #include <linux/kernel.h>
57 #include <linux/sched.h>
58 #include <linux/types.h>
59 #include <linux/fcntl.h>
60 #include <linux/interrupt.h>
61 #include <linux/ptrace.h>
62 #include <linux/ioport.h>
63 #include <linux/in.h>
64 #include <linux/malloc.h>
65 #include <linux/tty.h>
66 #include <linux/errno.h>
67 #include <linux/string.h> /* used in new tty drivers */
68 #include <linux/signal.h> /* used in new tty drivers */
69
70 #include <asm/system.h>
71 #include <asm/bitops.h>
72 #include <asm/segment.h>
73 #include <asm/byteorder.h>
74 #include <asm/types.h>
75
76 #include <linux/if.h>
77
78 #include <linux/if_ether.h>
79 #include <linux/netdevice.h>
80 #include <linux/skbuff.h>
81 #include <linux/inet.h>
82 #include <linux/ioctl.h>
83
84 #include <linux/ppp_defs.h>
85
86 #include <linux/isdn.h>
87 #include <linux/isdn_ppp.h>
88 /* #include <linux/netprotocol.h> */
89 #include <linux/ip.h>
90 #include <linux/tcp.h>
91 #include <linux/if_arp.h>
92 #include <linux/ppp-comp.h>
93
94 #include "isdn_ppp.h"
95
96 #define BSD_VERSION(x) ((x) >> 5)
97 #define BSD_NBITS(x) ((x) & 0x1F)
98
99 #define BSD_CURRENT_VERSION 1
100
101 #define DEBUG 1
102
103 /*
104 * A dictionary for doing BSD compress.
105 */
106
107 struct bsd_dict {
108 u32 fcode;
109 u16 codem1; /* output of hash table -1 */
110 u16 cptr; /* map code to hash table entry */
111 };
112
113 struct bsd_db {
114 int totlen; /* length of this structure */
115 unsigned int hsize; /* size of the hash table */
116 unsigned char hshift; /* used in hash function */
117 unsigned char n_bits; /* current bits/code */
118 unsigned char maxbits; /* maximum bits/code */
119 unsigned char debug; /* non-zero if debug desired */
120 unsigned char unit; /* ppp unit number */
121 u16 seqno; /* sequence # of next packet */
122 unsigned int mru; /* size of receive (decompress) bufr */
123 unsigned int maxmaxcode; /* largest valid code */
124 unsigned int max_ent; /* largest code in use */
125 unsigned int in_count; /* uncompressed bytes, aged */
126 unsigned int bytes_out; /* compressed bytes, aged */
127 unsigned int ratio; /* recent compression ratio */
128 unsigned int checkpoint; /* when to next check the ratio */
129 unsigned int clear_count; /* times dictionary cleared */
130 unsigned int incomp_count; /* incompressible packets */
131 unsigned int incomp_bytes; /* incompressible bytes */
132 unsigned int uncomp_count; /* uncompressed packets */
133 unsigned int uncomp_bytes; /* uncompressed bytes */
134 unsigned int comp_count; /* compressed packets */
135 unsigned int comp_bytes; /* compressed bytes */
136 unsigned short *lens; /* array of lengths of codes */
137 struct bsd_dict *dict; /* dictionary */
138 int xmit;
139 };
140
141 #define BSD_OVHD 2 /* BSD compress overhead/packet */
142 #define MIN_BSD_BITS 9
143 #define BSD_INIT_BITS MIN_BSD_BITS
144 #define MAX_BSD_BITS 15
145
146 /*
147 * the next two codes should not be changed lightly, as they must not
148 * lie within the contiguous general code space.
149 */
150 #define CLEAR 256 /* table clear output code */
151 #define FIRST 257 /* first free entry */
152 #define LAST 255
153
154 #define MAXCODE(b) ((1 << (b)) - 1)
155 #define BADCODEM1 MAXCODE(MAX_BSD_BITS);
156
157 #define BSD_HASH(prefix,suffix,hshift) ((((unsigned long)(suffix))<<(hshift)) \
158 ^ (unsigned long)(prefix))
159 #define BSD_KEY(prefix,suffix) ((((unsigned long)(suffix)) << 16) \
160 + (unsigned long)(prefix))
161
162 #define CHECK_GAP 10000 /* Ratio check interval */
163
164 #define RATIO_SCALE_LOG 8
165 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
166 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
167
168 /*
169 * clear the dictionary
170 */
171
172 static void bsd_clear(struct bsd_db *db)
173 {
174 db->clear_count++;
175 db->max_ent = FIRST-1;
176 db->n_bits = BSD_INIT_BITS;
177 db->bytes_out = 0;
178 db->in_count = 0;
179 db->incomp_count = 0;
180 db->ratio = 0;
181 db->checkpoint = CHECK_GAP;
182 }
183
184 /*
185 * If the dictionary is full, then see if it is time to reset it.
186 *
187 * Compute the compression ratio using fixed-point arithmetic
188 * with 8 fractional bits.
189 *
190 * Since we have an infinite stream instead of a single file,
191 * watch only the local compression ratio.
192 *
193 * Since both peers must reset the dictionary at the same time even in
194 * the absence of CLEAR codes (while packets are incompressible), they
195 * must compute the same ratio.
196 */
197 static int bsd_check (struct bsd_db *db) /* 1=output CLEAR */
198 {
199 unsigned int new_ratio;
200
201 if (db->in_count >= db->checkpoint)
202 {
203 /* age the ratio by limiting the size of the counts */
204 if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
205 {
206 db->in_count -= (db->in_count >> 2);
207 db->bytes_out -= (db->bytes_out >> 2);
208 }
209
210 db->checkpoint = db->in_count + CHECK_GAP;
211
212 if (db->max_ent >= db->maxmaxcode)
213 {
214 /* Reset the dictionary only if the ratio is worse,
215 * or if it looks as if it has been poisoned
216 * by incompressible data.
217 *
218 * This does not overflow, because
219 * db->in_count <= RATIO_MAX.
220 */
221
222 new_ratio = db->in_count << RATIO_SCALE_LOG;
223 if (db->bytes_out != 0)
224 {
225 new_ratio /= db->bytes_out;
226 }
227
228 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
229 {
230 bsd_clear (db);
231 return 1;
232 }
233 db->ratio = new_ratio;
234 }
235 }
236 return 0;
237 }
238
239 /*
240 * Return statistics.
241 */
242
243 static void bsd_stats (void *state, struct compstat *stats)
244 {
245 struct bsd_db *db = (struct bsd_db *) state;
246
247 stats->unc_bytes = db->uncomp_bytes;
248 stats->unc_packets = db->uncomp_count;
249 stats->comp_bytes = db->comp_bytes;
250 stats->comp_packets = db->comp_count;
251 stats->inc_bytes = db->incomp_bytes;
252 stats->inc_packets = db->incomp_count;
253 stats->in_count = db->in_count;
254 stats->bytes_out = db->bytes_out;
255 }
256
257 /*
258 * Reset state, as on a CCP ResetReq.
259 */
260 static void bsd_reset (void *state,unsigned char code, unsigned char id,
261 unsigned char *data, unsigned len,
262 struct isdn_ppp_resetparams *rsparm)
263 {
264 struct bsd_db *db = (struct bsd_db *) state;
265
266 bsd_clear(db);
267 db->seqno = 0;
268 db->clear_count = 0;
269 }
270
271 /*
272 * Release the compression structure
273 */
274 static void bsd_free (void *state)
275 {
276 struct bsd_db *db = (struct bsd_db *) state;
277
278 if (db) {
279 /*
280 * Release the dictionary
281 */
282 if (db->dict) {
283 vfree (db->dict);
284 db->dict = NULL;
285 }
286
287 /*
288 * Release the string buffer
289 */
290 if (db->lens) {
291 vfree (db->lens);
292 db->lens = NULL;
293 }
294
295 /*
296 * Finally release the structure itself.
297 */
298 kfree (db);
299 MOD_DEC_USE_COUNT;
300 }
301 }
302
303
304 /*
305 * Allocate space for a (de) compressor.
306 */
307 static void *bsd_alloc (struct isdn_ppp_comp_data *data)
308 {
309 int bits;
310 unsigned int hsize, hshift, maxmaxcode;
311 struct bsd_db *db;
312 int decomp;
313
314 static unsigned int htab[][2] = {
315 { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } ,
316 { 9001 , 5 } , { 18013 , 6 } , { 35023 , 7 } , { 69001 , 8 }
317 };
318
319 if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
320 || BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
321 return NULL;
322
323 bits = BSD_NBITS(data->options[0]);
324
325 if(bits < 9 || bits > 15)
326 return NULL;
327
328 hsize = htab[bits-9][0];
329 hshift = htab[bits-9][1];
330
331 /*
332 * Allocate the main control structure for this instance.
333 */
334 maxmaxcode = MAXCODE(bits);
335 db = (struct bsd_db *) kmalloc (sizeof (struct bsd_db),GFP_KERNEL);
336 if (!db)
337 return NULL;
338
339 memset (db, 0, sizeof(struct bsd_db));
340
341 db->xmit = data->flags & IPPP_COMP_FLAG_XMIT;
342 decomp = db->xmit ? 0 : 1;
343
344 /*
345 * Allocate space for the dictionary. This may be more than one page in
346 * length.
347 */
348 db->dict = (struct bsd_dict *) vmalloc (hsize * sizeof (struct bsd_dict));
349 if (!db->dict) {
350 bsd_free (db);
351 return NULL;
352 }
353
354 MOD_INC_USE_COUNT;
355
356 /*
357 * If this is the compression buffer then there is no length data.
358 * For decompression, the length information is needed as well.
359 */
360 if (!decomp)
361 db->lens = NULL;
362 else {
363 db->lens = (unsigned short *) vmalloc ((maxmaxcode + 1) *
364 sizeof (db->lens[0]));
365 if (!db->lens) {
366 bsd_free (db); /* calls MOD_DEC_USE_COUNT; */
367 return (NULL);
368 }
369 }
370
371 /*
372 * Initialize the data information for the compression code
373 */
374 db->totlen = sizeof (struct bsd_db) + (sizeof (struct bsd_dict) * hsize);
375 db->hsize = hsize;
376 db->hshift = hshift;
377 db->maxmaxcode = maxmaxcode;
378 db->maxbits = bits;
379
380 return (void *) db;
381 }
382
383 /*
384 * Initialize the database.
385 */
386 static int bsd_init (void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
387 {
388 struct bsd_db *db = state;
389 int indx;
390 int decomp;
391
392 if(!state || !data) {
393 printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n",unit,(long)state,(long)data);
394 return 0;
395 }
396
397 decomp = db->xmit ? 0 : 1;
398
399 if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
400 || (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
401 || (BSD_NBITS(data->options[0]) != db->maxbits)
402 || (decomp && db->lens == NULL)) {
403 printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n",data->optlen,data->num,data->options[0],decomp,(unsigned long)db->lens);
404 return 0;
405 }
406
407 if (decomp)
408 for(indx=LAST;indx>=0;indx--)
409 db->lens[indx] = 1;
410
411 indx = db->hsize;
412 while (indx-- != 0) {
413 db->dict[indx].codem1 = BADCODEM1;
414 db->dict[indx].cptr = 0;
415 }
416
417 db->unit = unit;
418 db->mru = 0;
419
420 db->debug = 1;
421
422 bsd_reset(db,0,0,NULL,0,NULL);
423
424 return 1;
425 }
426
427 /*
428 * Obtain pointers to the various structures in the compression tables
429 */
430
431 #define dict_ptrx(p,idx) &(p->dict[idx])
432 #define lens_ptrx(p,idx) &(p->lens[idx])
433
434 #ifdef DEBUG
435 static unsigned short *lens_ptr(struct bsd_db *db, int idx)
436 {
437 if ((unsigned int) idx > (unsigned int) db->maxmaxcode) {
438 printk (KERN_DEBUG "<9>ppp: lens_ptr(%d) > max\n", idx);
439 idx = 0;
440 }
441 return lens_ptrx (db, idx);
442 }
443
444 static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
445 {
446 if ((unsigned int) idx >= (unsigned int) db->hsize) {
447 printk (KERN_DEBUG "<9>ppp: dict_ptr(%d) > max\n", idx);
448 idx = 0;
449 }
450 return dict_ptrx (db, idx);
451 }
452
453 #else
454 #define lens_ptr(db,idx) lens_ptrx(db,idx)
455 #define dict_ptr(db,idx) dict_ptrx(db,idx)
456 #endif
457
458 /*
459 * compress a packet
460 */
461 static int bsd_compress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,int proto)
462 {
463 struct bsd_db *db;
464 int hshift;
465 unsigned int max_ent;
466 unsigned int n_bits;
467 unsigned int bitno;
468 unsigned long accm;
469 int ent;
470 unsigned long fcode;
471 struct bsd_dict *dictp;
472 unsigned char c;
473 int hval,disp,ilen,mxcode;
474 unsigned char *rptr = skb_in->data;
475 int isize = skb_in->len;
476
477 #define OUTPUT(ent) \
478 { \
479 bitno -= n_bits; \
480 accm |= ((ent) << bitno); \
481 do { \
482 if(skb_out && skb_tailroom(skb_out) > 0) \
483 *(skb_put(skb_out,1)) = (unsigned char) (accm>>24); \
484 accm <<= 8; \
485 bitno += 8; \
486 } while (bitno <= 24); \
487 }
488
489 /*
490 * If the protocol is not in the range we're interested in,
491 * just return without compressing the packet. If it is,
492 * the protocol becomes the first byte to compress.
493 */
494 printk(KERN_DEBUG "bsd_compress called with %x\n",proto);
495
496 ent = proto;
497 if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1) )
498 return 0;
499
500 db = (struct bsd_db *) state;
501 hshift = db->hshift;
502 max_ent = db->max_ent;
503 n_bits = db->n_bits;
504 bitno = 32;
505 accm = 0;
506 mxcode = MAXCODE (n_bits);
507
508 /* This is the PPP header information */
509 if(skb_out && skb_tailroom(skb_out) >= 2) {
510 char *v = skb_put(skb_out,2);
511 /* we only push our own data on the header,
512 AC,PC and protos is pushed by caller */
513 v[0] = db->seqno >> 8;
514 v[1] = db->seqno;
515 }
516
517 ilen = ++isize; /* This is off by one, but that is what is in draft! */
518
519 while (--ilen > 0) {
520 c = *rptr++;
521 fcode = BSD_KEY (ent, c);
522 hval = BSD_HASH (ent, c, hshift);
523 dictp = dict_ptr (db, hval);
524
525 /* Validate and then check the entry. */
526 if (dictp->codem1 >= max_ent)
527 goto nomatch;
528
529 if (dictp->fcode == fcode) {
530 ent = dictp->codem1 + 1;
531 continue; /* found (prefix,suffix) */
532 }
533
534 /* continue probing until a match or invalid entry */
535 disp = (hval == 0) ? 1 : hval;
536
537 do {
538 hval += disp;
539 if (hval >= db->hsize)
540 hval -= db->hsize;
541 dictp = dict_ptr (db, hval);
542 if (dictp->codem1 >= max_ent)
543 goto nomatch;
544 } while (dictp->fcode != fcode);
545
546 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
547 continue;
548
549 nomatch:
550 OUTPUT(ent); /* output the prefix */
551
552 /* code -> hashtable */
553 if (max_ent < db->maxmaxcode) {
554 struct bsd_dict *dictp2;
555 struct bsd_dict *dictp3;
556 int indx;
557
558 /* expand code size if needed */
559 if (max_ent >= mxcode) {
560 db->n_bits = ++n_bits;
561 mxcode = MAXCODE (n_bits);
562 }
563
564 /*
565 * Invalidate old hash table entry using
566 * this code, and then take it over.
567 */
568 dictp2 = dict_ptr (db, max_ent + 1);
569 indx = dictp2->cptr;
570 dictp3 = dict_ptr (db, indx);
571
572 if (dictp3->codem1 == max_ent)
573 dictp3->codem1 = BADCODEM1;
574
575 dictp2->cptr = hval;
576 dictp->codem1 = max_ent;
577 dictp->fcode = fcode;
578 db->max_ent = ++max_ent;
579
580 if (db->lens) {
581 unsigned short *len1 = lens_ptr (db, max_ent);
582 unsigned short *len2 = lens_ptr (db, ent);
583 *len1 = *len2 + 1;
584 }
585 }
586 ent = c;
587 }
588
589 OUTPUT(ent); /* output the last code */
590
591 if(skb_out)
592 db->bytes_out += skb_out->len; /* Do not count bytes from here */
593 db->uncomp_bytes += isize;
594 db->in_count += isize;
595 ++db->uncomp_count;
596 ++db->seqno;
597
598 if (bitno < 32)
599 ++db->bytes_out; /* must be set before calling bsd_check */
600
601 /*
602 * Generate the clear command if needed
603 */
604
605 if (bsd_check(db))
606 OUTPUT (CLEAR);
607
608 /*
609 * Pad dribble bits of last code with ones.
610 * Do not emit a completely useless byte of ones.
611 */
612 if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0)
613 *(skb_put(skb_out,1)) = (unsigned char) ((accm | (0xff << (bitno-8))) >> 24);
614
615 /*
616 * Increase code size if we would have without the packet
617 * boundary because the decompressor will do so.
618 */
619 if (max_ent >= mxcode && max_ent < db->maxmaxcode)
620 db->n_bits++;
621
622 /* If output length is too large then this is an incompressible frame. */
623 if (!skb_out || (skb_out && skb_out->len >= skb_in->len) ) {
624 ++db->incomp_count;
625 db->incomp_bytes += isize;
626 return 0;
627 }
628
629 /* Count the number of compressed frames */
630 ++db->comp_count;
631 db->comp_bytes += skb_out->len;
632 return skb_out->len;
633
634 #undef OUTPUT
635 }
636
637 /*
638 * Update the "BSD Compress" dictionary on the receiver for
639 * incompressible data by pretending to compress the incoming data.
640 */
641 static void bsd_incomp (void *state, struct sk_buff *skb_in,int proto)
642 {
643 bsd_compress (state, skb_in, NULL, proto);
644 }
645
646 /*
647 * Decompress "BSD Compress".
648 */
649 static int bsd_decompress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,
650 struct isdn_ppp_resetparams *rsparm)
651 {
652 struct bsd_db *db;
653 unsigned int max_ent;
654 unsigned long accm;
655 unsigned int bitno; /* 1st valid bit in accm */
656 unsigned int n_bits;
657 unsigned int tgtbitno; /* bitno when we have a code */
658 struct bsd_dict *dictp;
659 int seq;
660 unsigned int incode;
661 unsigned int oldcode;
662 unsigned int finchar;
663 unsigned char *p,*ibuf;
664 int ilen;
665 int codelen;
666 int extra;
667
668 db = (struct bsd_db *) state;
669 max_ent = db->max_ent;
670 accm = 0;
671 bitno = 32; /* 1st valid bit in accm */
672 n_bits = db->n_bits;
673 tgtbitno = 32 - n_bits; /* bitno when we have a code */
674
675 printk(KERN_DEBUG "bsd_decompress called\n");
676
677 if(!skb_in || !skb_out) {
678 printk(KERN_ERR "bsd_decompress called with NULL parameter\n");
679 return DECOMP_ERROR;
680 }
681
682 /*
683 * Get the sequence number.
684 */
685 if( (p = skb_pull(skb_in,2)) == NULL) {
686 return DECOMP_ERROR;
687 }
688 p-=2;
689 seq = (p[0] << 8) + p[1];
690 ilen = skb_in->len;
691 ibuf = skb_in->data;
692
693 /*
694 * Check the sequence number and give up if it differs from
695 * the value we're expecting.
696 */
697 if (seq != db->seqno) {
698 if (db->debug) {
699 printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n",
700 db->unit, seq, db->seqno - 1);
701 }
702 return DECOMP_ERROR;
703 }
704
705 ++db->seqno;
706 db->bytes_out += ilen;
707
708 if(skb_tailroom(skb_out) > 0)
709 *(skb_put(skb_out,1)) = 0;
710 else
711 return DECOMP_ERR_NOMEM;
712
713 oldcode = CLEAR;
714
715 /*
716 * Keep the checkpoint correctly so that incompressible packets
717 * clear the dictionary at the proper times.
718 */
719
720 for (;;) {
721 if (ilen-- <= 0) {
722 db->in_count += (skb_out->len - 1); /* don't count the header */
723 break;
724 }
725
726 /*
727 * Accumulate bytes until we have a complete code.
728 * Then get the next code, relying on the 32-bit,
729 * unsigned accm to mask the result.
730 */
731
732 bitno -= 8;
733 accm |= *ibuf++ << bitno;
734 if (tgtbitno < bitno)
735 continue;
736
737 incode = accm >> tgtbitno;
738 accm <<= n_bits;
739 bitno += n_bits;
740
741 /*
742 * The dictionary must only be cleared at the end of a packet.
743 */
744
745 if (incode == CLEAR) {
746 if (ilen > 0) {
747 if (db->debug)
748 printk(KERN_DEBUG "bsd_decomp%d: bad CLEAR\n", db->unit);
749 return DECOMP_FATALERROR; /* probably a bug */
750 }
751 bsd_clear(db);
752 break;
753 }
754
755 if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
756 || (incode > max_ent && oldcode == CLEAR)) {
757 if (db->debug) {
758 printk(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
759 db->unit, incode, oldcode);
760 printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n",
761 max_ent, skb_out->len, db->seqno);
762 }
763 return DECOMP_FATALERROR; /* probably a bug */
764 }
765
766 /* Special case for KwKwK string. */
767 if (incode > max_ent) {
768 finchar = oldcode;
769 extra = 1;
770 } else {
771 finchar = incode;
772 extra = 0;
773 }
774
775 codelen = *(lens_ptr (db, finchar));
776 if( skb_tailroom(skb_out) < codelen + extra) {
777 if (db->debug) {
778 printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit);
779 #ifdef DEBUG
780 printk(KERN_DEBUG " len=%d, finchar=0x%x, codelen=%d,skblen=%d\n",
781 ilen, finchar, codelen, skb_out->len);
782 #endif
783 }
784 return DECOMP_FATALERROR;
785 }
786
787 /*
788 * Decode this code and install it in the decompressed buffer.
789 */
790
791 p = skb_put(skb_out,codelen);
792 p += codelen;
793 while (finchar > LAST) {
794 struct bsd_dict *dictp2 = dict_ptr (db, finchar);
795
796 dictp = dict_ptr (db, dictp2->cptr);
797
798 #ifdef DEBUG
799 if (--codelen <= 0 || dictp->codem1 != finchar-1) {
800 if (codelen <= 0) {
801 printk(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit);
802 printk(KERN_ERR "0x%x at 0x%x by 0x%x, max_ent=0x%x\n", incode, finchar, dictp2->cptr, max_ent);
803 } else {
804 if (dictp->codem1 != finchar-1) {
805 printk(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",db->unit, incode, finchar);
806 printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1);
807 }
808 }
809 return DECOMP_FATALERROR;
810 }
811 #endif
812
813 {
814 u32 fcode = dictp->fcode;
815 *--p = (fcode >> 16) & 0xff;
816 finchar = fcode & 0xffff;
817 }
818 }
819 *--p = finchar;
820
821 #ifdef DEBUG
822 if (--codelen != 0)
823 printk(KERN_ERR "bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", db->unit, codelen, incode, max_ent);
824 #endif
825
826 if (extra) /* the KwKwK case again */
827 *(skb_put(skb_out,1)) = finchar;
828
829 /*
830 * If not first code in a packet, and
831 * if not out of code space, then allocate a new code.
832 *
833 * Keep the hash table correct so it can be used
834 * with uncompressed packets.
835 */
836 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
837 struct bsd_dict *dictp2, *dictp3;
838 u16 *lens1, *lens2;
839 unsigned long fcode;
840 int hval, disp, indx;
841
842 fcode = BSD_KEY(oldcode,finchar);
843 hval = BSD_HASH(oldcode,finchar,db->hshift);
844 dictp = dict_ptr (db, hval);
845
846 /* look for a free hash table entry */
847 if (dictp->codem1 < max_ent) {
848 disp = (hval == 0) ? 1 : hval;
849 do {
850 hval += disp;
851 if (hval >= db->hsize)
852 hval -= db->hsize;
853 dictp = dict_ptr (db, hval);
854 } while (dictp->codem1 < max_ent);
855 }
856
857 /*
858 * Invalidate previous hash table entry
859 * assigned this code, and then take it over
860 */
861
862 dictp2 = dict_ptr (db, max_ent + 1);
863 indx = dictp2->cptr;
864 dictp3 = dict_ptr (db, indx);
865
866 if (dictp3->codem1 == max_ent)
867 dictp3->codem1 = BADCODEM1;
868
869 dictp2->cptr = hval;
870 dictp->codem1 = max_ent;
871 dictp->fcode = fcode;
872 db->max_ent = ++max_ent;
873
874 /* Update the length of this string. */
875 lens1 = lens_ptr (db, max_ent);
876 lens2 = lens_ptr (db, oldcode);
877 *lens1 = *lens2 + 1;
878
879 /* Expand code size if needed. */
880 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
881 db->n_bits = ++n_bits;
882 tgtbitno = 32-n_bits;
883 }
884 }
885 oldcode = incode;
886 }
887
888 ++db->comp_count;
889 ++db->uncomp_count;
890 db->comp_bytes += skb_in->len - BSD_OVHD;
891 db->uncomp_bytes += skb_out->len;
892
893 if (bsd_check(db)) {
894 if (db->debug)
895 printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n",
896 db->unit, db->seqno - 1);
897 }
898 return skb_out->len;
899 }
900
901 /*************************************************************
902 * Table of addresses for the BSD compression module
903 *************************************************************/
904
905 static struct isdn_ppp_compressor ippp_bsd_compress = {
906 NULL,NULL, /* prev,next: overwritten by isdn_ppp */
907 CI_BSD_COMPRESS, /* compress_proto */
908 bsd_alloc, /* alloc */
909 bsd_free, /* free */
910 bsd_init, /* init */
911 bsd_reset, /* reset */
912 bsd_compress, /* compress */
913 bsd_decompress, /* decompress */
914 bsd_incomp, /* incomp */
915 bsd_stats /* comp_stat */
916 };
917
918 /*************************************************************
919 * Module support routines
920 *************************************************************/
921
922 int init_module(void)
923 {
924 int answer = isdn_ppp_register_compressor (&ippp_bsd_compress);
925 if (answer == 0)
926 printk (KERN_INFO "PPP BSD Compression module registered\n");
927 return answer;
928 }
929
930 void cleanup_module(void)
931 {
932 isdn_ppp_unregister_compressor (&ippp_bsd_compress);
933 }
934
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