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 */
8
9 /*
10 * Update: The Berkeley copyright was changed, and the change
11 * is retroactive to all "true" BSD software (ie everything
12 * from UCB as opposed to other peoples code that just carried
13 * the same license). The new copyright doesn't clash with the
14 * GPL, so the module-only restriction has been removed..
15 */
16
17 /*
18 * Original copyright notice:
19 *
20 * Copyright (c) 1985, 1986 The Regents of the University of California.
21 * All rights reserved.
22 *
23 * This code is derived from software contributed to Berkeley by
24 * James A. Woods, derived from original work by Spencer Thomas
25 * and Joseph Orost.
26 *
27 * Redistribution and use in source and binary forms, with or without
28 * modification, are permitted provided that the following conditions
29 * are met:
30 * 1. Redistributions of source code must retain the above copyright
31 * notice, this list of conditions and the following disclaimer.
32 * 2. Redistributions in binary form must reproduce the above copyright
33 * notice, this list of conditions and the following disclaimer in the
34 * documentation and/or other materials provided with the distribution.
35 * 3. All advertising materials mentioning features or use of this software
36 * must display the following acknowledgement:
37 * This product includes software developed by the University of
38 * California, Berkeley and its contributors.
39 * 4. Neither the name of the University nor the names of its contributors
40 * may be used to endorse or promote products derived from this software
41 * without specific prior written permission.
42 *
43 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
44 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
45 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
46 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
47 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
48 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
49 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
50 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
51 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
52 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * SUCH DAMAGE.
54 */
55
56 #include <linux/module.h>
57 #include <linux/init.h>
58 #include <linux/kernel.h>
59 #include <linux/types.h>
60 #include <linux/fcntl.h>
61 #include <linux/interrupt.h>
62 #include <linux/ptrace.h>
63 #include <linux/ioport.h>
64 #include <linux/in.h>
65 #include <linux/slab.h>
66 #include <linux/tty.h>
67 #include <linux/errno.h>
68 #include <linux/string.h> /* used in new tty drivers */
69 #include <linux/signal.h> /* used in new tty drivers */
70 #include <linux/bitops.h>
71
72 #include <asm/byteorder.h>
73 #include <asm/types.h>
74
75 #include <linux/if.h>
76
77 #include <linux/if_ether.h>
78 #include <linux/netdevice.h>
79 #include <linux/skbuff.h>
80 #include <linux/inet.h>
81 #include <linux/ioctl.h>
82 #include <linux/vmalloc.h>
83
84 #include <linux/ppp_defs.h>
85
86 #include <linux/isdn.h>
87 #include <linux/isdn_ppp.h>
88 #include <linux/ip.h>
89 #include <linux/tcp.h>
90 #include <linux/if_arp.h>
91 #include <linux/ppp-comp.h>
92
93 #include "isdn_ppp.h"
94
95 MODULE_DESCRIPTION("ISDN4Linux: BSD Compression for PPP over ISDN");
96 MODULE_LICENSE("Dual BSD/GPL");
97
98 #define BSD_VERSION(x) ((x) >> 5)
99 #define BSD_NBITS(x) ((x) & 0x1F)
100
101 #define BSD_CURRENT_VERSION 1
102
103 #define DEBUG 1
104
105 /*
106 * A dictionary for doing BSD compress.
107 */
108
109 struct bsd_dict {
110 u32 fcode;
111 u16 codem1; /* output of hash table -1 */
112 u16 cptr; /* map code to hash table entry */
113 };
114
115 struct bsd_db {
116 int totlen; /* length of this structure */
117 unsigned int hsize; /* size of the hash table */
118 unsigned char hshift; /* used in hash function */
119 unsigned char n_bits; /* current bits/code */
120 unsigned char maxbits; /* maximum bits/code */
121 unsigned char debug; /* non-zero if debug desired */
122 unsigned char unit; /* ppp unit number */
123 u16 seqno; /* sequence # of next packet */
124 unsigned int mru; /* size of receive (decompress) bufr */
125 unsigned int maxmaxcode; /* largest valid code */
126 unsigned int max_ent; /* largest code in use */
127 unsigned int in_count; /* uncompressed bytes, aged */
128 unsigned int bytes_out; /* compressed bytes, aged */
129 unsigned int ratio; /* recent compression ratio */
130 unsigned int checkpoint; /* when to next check the ratio */
131 unsigned int clear_count; /* times dictionary cleared */
132 unsigned int incomp_count; /* incompressible packets */
133 unsigned int incomp_bytes; /* incompressible bytes */
134 unsigned int uncomp_count; /* uncompressed packets */
135 unsigned int uncomp_bytes; /* uncompressed bytes */
136 unsigned int comp_count; /* compressed packets */
137 unsigned int comp_bytes; /* compressed bytes */
138 unsigned short *lens; /* array of lengths of codes */
139 struct bsd_dict *dict; /* dictionary */
140 int xmit;
141 };
142
143 #define BSD_OVHD 2 /* BSD compress overhead/packet */
144 #define MIN_BSD_BITS 9
145 #define BSD_INIT_BITS MIN_BSD_BITS
146 #define MAX_BSD_BITS 15
147
148 /*
149 * the next two codes should not be changed lightly, as they must not
150 * lie within the contiguous general code space.
151 */
152 #define CLEAR 256 /* table clear output code */
153 #define FIRST 257 /* first free entry */
154 #define LAST 255
155
156 #define MAXCODE(b) ((1 << (b)) - 1)
157 #define BADCODEM1 MAXCODE(MAX_BSD_BITS)
158
159 #define BSD_HASH(prefix, suffix, hshift) ((((unsigned long)(suffix)) << (hshift)) \
160 ^ (unsigned long)(prefix))
161 #define BSD_KEY(prefix, suffix) ((((unsigned long)(suffix)) << 16) \
162 + (unsigned long)(prefix))
163
164 #define CHECK_GAP 10000 /* Ratio check interval */
165
166 #define RATIO_SCALE_LOG 8
167 #define RATIO_SCALE (1 << RATIO_SCALE_LOG)
168 #define RATIO_MAX (0x7fffffff >> RATIO_SCALE_LOG)
169
170 /*
171 * clear the dictionary
172 */
173
bsd_clear(struct bsd_db * db)174 static void bsd_clear(struct bsd_db *db)
175 {
176 db->clear_count++;
177 db->max_ent = FIRST - 1;
178 db->n_bits = BSD_INIT_BITS;
179 db->bytes_out = 0;
180 db->in_count = 0;
181 db->incomp_count = 0;
182 db->ratio = 0;
183 db->checkpoint = CHECK_GAP;
184 }
185
186 /*
187 * If the dictionary is full, then see if it is time to reset it.
188 *
189 * Compute the compression ratio using fixed-point arithmetic
190 * with 8 fractional bits.
191 *
192 * Since we have an infinite stream instead of a single file,
193 * watch only the local compression ratio.
194 *
195 * Since both peers must reset the dictionary at the same time even in
196 * the absence of CLEAR codes (while packets are incompressible), they
197 * must compute the same ratio.
198 */
bsd_check(struct bsd_db * db)199 static int bsd_check(struct bsd_db *db) /* 1=output CLEAR */
200 {
201 unsigned int new_ratio;
202
203 if (db->in_count >= db->checkpoint)
204 {
205 /* age the ratio by limiting the size of the counts */
206 if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
207 {
208 db->in_count -= (db->in_count >> 2);
209 db->bytes_out -= (db->bytes_out >> 2);
210 }
211
212 db->checkpoint = db->in_count + CHECK_GAP;
213
214 if (db->max_ent >= db->maxmaxcode)
215 {
216 /* Reset the dictionary only if the ratio is worse,
217 * or if it looks as if it has been poisoned
218 * by incompressible data.
219 *
220 * This does not overflow, because
221 * db->in_count <= RATIO_MAX.
222 */
223
224 new_ratio = db->in_count << RATIO_SCALE_LOG;
225 if (db->bytes_out != 0)
226 {
227 new_ratio /= db->bytes_out;
228 }
229
230 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
231 {
232 bsd_clear(db);
233 return 1;
234 }
235 db->ratio = new_ratio;
236 }
237 }
238 return 0;
239 }
240
241 /*
242 * Return statistics.
243 */
244
bsd_stats(void * state,struct compstat * stats)245 static void bsd_stats(void *state, struct compstat *stats)
246 {
247 struct bsd_db *db = (struct bsd_db *) state;
248
249 stats->unc_bytes = db->uncomp_bytes;
250 stats->unc_packets = db->uncomp_count;
251 stats->comp_bytes = db->comp_bytes;
252 stats->comp_packets = db->comp_count;
253 stats->inc_bytes = db->incomp_bytes;
254 stats->inc_packets = db->incomp_count;
255 stats->in_count = db->in_count;
256 stats->bytes_out = db->bytes_out;
257 }
258
259 /*
260 * Reset state, as on a CCP ResetReq.
261 */
bsd_reset(void * state,unsigned char code,unsigned char id,unsigned char * data,unsigned len,struct isdn_ppp_resetparams * rsparm)262 static void bsd_reset(void *state, unsigned char code, unsigned char id,
263 unsigned char *data, unsigned len,
264 struct isdn_ppp_resetparams *rsparm)
265 {
266 struct bsd_db *db = (struct bsd_db *) state;
267
268 bsd_clear(db);
269 db->seqno = 0;
270 db->clear_count = 0;
271 }
272
273 /*
274 * Release the compression structure
275 */
bsd_free(void * state)276 static void bsd_free(void *state)
277 {
278 struct bsd_db *db = (struct bsd_db *) state;
279
280 if (db) {
281 /*
282 * Release the dictionary
283 */
284 vfree(db->dict);
285 db->dict = NULL;
286
287 /*
288 * Release the string buffer
289 */
290 vfree(db->lens);
291 db->lens = NULL;
292
293 /*
294 * Finally release the structure itself.
295 */
296 kfree(db);
297 }
298 }
299
300
301 /*
302 * Allocate space for a (de) compressor.
303 */
bsd_alloc(struct isdn_ppp_comp_data * data)304 static void *bsd_alloc(struct isdn_ppp_comp_data *data)
305 {
306 int bits;
307 unsigned int hsize, hshift, maxmaxcode;
308 struct bsd_db *db;
309 int decomp;
310
311 static unsigned int htab[][2] = {
312 { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } ,
313 { 9001 , 5 } , { 18013 , 6 } , { 35023 , 7 } , { 69001 , 8 }
314 };
315
316 if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
317 || BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
318 return NULL;
319
320 bits = BSD_NBITS(data->options[0]);
321
322 if (bits < 9 || bits > 15)
323 return NULL;
324
325 hsize = htab[bits - 9][0];
326 hshift = htab[bits - 9][1];
327
328 /*
329 * Allocate the main control structure for this instance.
330 */
331 maxmaxcode = MAXCODE(bits);
332 db = kzalloc(sizeof(struct bsd_db), GFP_KERNEL);
333 if (!db)
334 return NULL;
335
336 db->xmit = data->flags & IPPP_COMP_FLAG_XMIT;
337 decomp = db->xmit ? 0 : 1;
338
339 /*
340 * Allocate space for the dictionary. This may be more than one page in
341 * length.
342 */
343 db->dict = vmalloc(hsize * sizeof(struct bsd_dict));
344 if (!db->dict) {
345 bsd_free(db);
346 return NULL;
347 }
348
349 /*
350 * If this is the compression buffer then there is no length data.
351 * For decompression, the length information is needed as well.
352 */
353 if (!decomp)
354 db->lens = NULL;
355 else {
356 db->lens = vmalloc((maxmaxcode + 1) * sizeof(db->lens[0]));
357 if (!db->lens) {
358 bsd_free(db);
359 return (NULL);
360 }
361 }
362
363 /*
364 * Initialize the data information for the compression code
365 */
366 db->totlen = sizeof(struct bsd_db) + (sizeof(struct bsd_dict) * hsize);
367 db->hsize = hsize;
368 db->hshift = hshift;
369 db->maxmaxcode = maxmaxcode;
370 db->maxbits = bits;
371
372 return (void *)db;
373 }
374
375 /*
376 * Initialize the database.
377 */
bsd_init(void * state,struct isdn_ppp_comp_data * data,int unit,int debug)378 static int bsd_init(void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
379 {
380 struct bsd_db *db = state;
381 int indx;
382 int decomp;
383
384 if (!state || !data) {
385 printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n", unit, (long)state, (long)data);
386 return 0;
387 }
388
389 decomp = db->xmit ? 0 : 1;
390
391 if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
392 || (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
393 || (BSD_NBITS(data->options[0]) != db->maxbits)
394 || (decomp && db->lens == NULL)) {
395 printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n", data->optlen, data->num, data->options[0], decomp, (unsigned long)db->lens);
396 return 0;
397 }
398
399 if (decomp)
400 for (indx = LAST; indx >= 0; indx--)
401 db->lens[indx] = 1;
402
403 indx = db->hsize;
404 while (indx-- != 0) {
405 db->dict[indx].codem1 = BADCODEM1;
406 db->dict[indx].cptr = 0;
407 }
408
409 db->unit = unit;
410 db->mru = 0;
411
412 db->debug = 1;
413
414 bsd_reset(db, 0, 0, NULL, 0, NULL);
415
416 return 1;
417 }
418
419 /*
420 * Obtain pointers to the various structures in the compression tables
421 */
422
423 #define dict_ptrx(p, idx) &(p->dict[idx])
424 #define lens_ptrx(p, idx) &(p->lens[idx])
425
426 #ifdef DEBUG
lens_ptr(struct bsd_db * db,int idx)427 static unsigned short *lens_ptr(struct bsd_db *db, int idx)
428 {
429 if ((unsigned int) idx > (unsigned int) db->maxmaxcode) {
430 printk(KERN_DEBUG "<9>ppp: lens_ptr(%d) > max\n", idx);
431 idx = 0;
432 }
433 return lens_ptrx(db, idx);
434 }
435
dict_ptr(struct bsd_db * db,int idx)436 static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
437 {
438 if ((unsigned int) idx >= (unsigned int) db->hsize) {
439 printk(KERN_DEBUG "<9>ppp: dict_ptr(%d) > max\n", idx);
440 idx = 0;
441 }
442 return dict_ptrx(db, idx);
443 }
444
445 #else
446 #define lens_ptr(db, idx) lens_ptrx(db, idx)
447 #define dict_ptr(db, idx) dict_ptrx(db, idx)
448 #endif
449
450 /*
451 * compress a packet
452 */
bsd_compress(void * state,struct sk_buff * skb_in,struct sk_buff * skb_out,int proto)453 static int bsd_compress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out, int proto)
454 {
455 struct bsd_db *db;
456 int hshift;
457 unsigned int max_ent;
458 unsigned int n_bits;
459 unsigned int bitno;
460 unsigned long accm;
461 int ent;
462 unsigned long fcode;
463 struct bsd_dict *dictp;
464 unsigned char c;
465 int hval, disp, ilen, mxcode;
466 unsigned char *rptr = skb_in->data;
467 int isize = skb_in->len;
468
469 #define OUTPUT(ent) \
470 { \
471 bitno -= n_bits; \
472 accm |= ((ent) << bitno); \
473 do { \
474 if (skb_out && skb_tailroom(skb_out) > 0) \
475 skb_put_u8(skb_out, (u8)(accm >> 24)); \
476 accm <<= 8; \
477 bitno += 8; \
478 } while (bitno <= 24); \
479 }
480
481 /*
482 * If the protocol is not in the range we're interested in,
483 * just return without compressing the packet. If it is,
484 * the protocol becomes the first byte to compress.
485 */
486 printk(KERN_DEBUG "bsd_compress called with %x\n", proto);
487
488 ent = proto;
489 if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1))
490 return 0;
491
492 db = (struct bsd_db *) state;
493 hshift = db->hshift;
494 max_ent = db->max_ent;
495 n_bits = db->n_bits;
496 bitno = 32;
497 accm = 0;
498 mxcode = MAXCODE(n_bits);
499
500 /* This is the PPP header information */
501 if (skb_out && skb_tailroom(skb_out) >= 2) {
502 char *v = skb_put(skb_out, 2);
503 /* we only push our own data on the header,
504 AC,PC and protos is pushed by caller */
505 v[0] = db->seqno >> 8;
506 v[1] = db->seqno;
507 }
508
509 ilen = ++isize; /* This is off by one, but that is what is in draft! */
510
511 while (--ilen > 0) {
512 c = *rptr++;
513 fcode = BSD_KEY(ent, c);
514 hval = BSD_HASH(ent, c, hshift);
515 dictp = dict_ptr(db, hval);
516
517 /* Validate and then check the entry. */
518 if (dictp->codem1 >= max_ent)
519 goto nomatch;
520
521 if (dictp->fcode == fcode) {
522 ent = dictp->codem1 + 1;
523 continue; /* found (prefix,suffix) */
524 }
525
526 /* continue probing until a match or invalid entry */
527 disp = (hval == 0) ? 1 : hval;
528
529 do {
530 hval += disp;
531 if (hval >= db->hsize)
532 hval -= db->hsize;
533 dictp = dict_ptr(db, hval);
534 if (dictp->codem1 >= max_ent)
535 goto nomatch;
536 } while (dictp->fcode != fcode);
537
538 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
539 continue;
540
541 nomatch:
542 OUTPUT(ent); /* output the prefix */
543
544 /* code -> hashtable */
545 if (max_ent < db->maxmaxcode) {
546 struct bsd_dict *dictp2;
547 struct bsd_dict *dictp3;
548 int indx;
549
550 /* expand code size if needed */
551 if (max_ent >= mxcode) {
552 db->n_bits = ++n_bits;
553 mxcode = MAXCODE(n_bits);
554 }
555
556 /*
557 * Invalidate old hash table entry using
558 * this code, and then take it over.
559 */
560 dictp2 = dict_ptr(db, max_ent + 1);
561 indx = dictp2->cptr;
562 dictp3 = dict_ptr(db, indx);
563
564 if (dictp3->codem1 == max_ent)
565 dictp3->codem1 = BADCODEM1;
566
567 dictp2->cptr = hval;
568 dictp->codem1 = max_ent;
569 dictp->fcode = fcode;
570 db->max_ent = ++max_ent;
571
572 if (db->lens) {
573 unsigned short *len1 = lens_ptr(db, max_ent);
574 unsigned short *len2 = lens_ptr(db, ent);
575 *len1 = *len2 + 1;
576 }
577 }
578 ent = c;
579 }
580
581 OUTPUT(ent); /* output the last code */
582
583 if (skb_out)
584 db->bytes_out += skb_out->len; /* Do not count bytes from here */
585 db->uncomp_bytes += isize;
586 db->in_count += isize;
587 ++db->uncomp_count;
588 ++db->seqno;
589
590 if (bitno < 32)
591 ++db->bytes_out; /* must be set before calling bsd_check */
592
593 /*
594 * Generate the clear command if needed
595 */
596
597 if (bsd_check(db))
598 OUTPUT(CLEAR);
599
600 /*
601 * Pad dribble bits of last code with ones.
602 * Do not emit a completely useless byte of ones.
603 */
604 if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0)
605 skb_put_u8(skb_out,
606 (unsigned char)((accm | (0xff << (bitno - 8))) >> 24));
607
608 /*
609 * Increase code size if we would have without the packet
610 * boundary because the decompressor will do so.
611 */
612 if (max_ent >= mxcode && max_ent < db->maxmaxcode)
613 db->n_bits++;
614
615 /* If output length is too large then this is an incompressible frame. */
616 if (!skb_out || skb_out->len >= skb_in->len) {
617 ++db->incomp_count;
618 db->incomp_bytes += isize;
619 return 0;
620 }
621
622 /* Count the number of compressed frames */
623 ++db->comp_count;
624 db->comp_bytes += skb_out->len;
625 return skb_out->len;
626
627 #undef OUTPUT
628 }
629
630 /*
631 * Update the "BSD Compress" dictionary on the receiver for
632 * incompressible data by pretending to compress the incoming data.
633 */
bsd_incomp(void * state,struct sk_buff * skb_in,int proto)634 static void bsd_incomp(void *state, struct sk_buff *skb_in, int proto)
635 {
636 bsd_compress(state, skb_in, NULL, proto);
637 }
638
639 /*
640 * Decompress "BSD Compress".
641 */
bsd_decompress(void * state,struct sk_buff * skb_in,struct sk_buff * skb_out,struct isdn_ppp_resetparams * rsparm)642 static int bsd_decompress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,
643 struct isdn_ppp_resetparams *rsparm)
644 {
645 struct bsd_db *db;
646 unsigned int max_ent;
647 unsigned long accm;
648 unsigned int bitno; /* 1st valid bit in accm */
649 unsigned int n_bits;
650 unsigned int tgtbitno; /* bitno when we have a code */
651 struct bsd_dict *dictp;
652 int seq;
653 unsigned int incode;
654 unsigned int oldcode;
655 unsigned int finchar;
656 unsigned char *p, *ibuf;
657 int ilen;
658 int codelen;
659 int extra;
660
661 db = (struct bsd_db *) state;
662 max_ent = db->max_ent;
663 accm = 0;
664 bitno = 32; /* 1st valid bit in accm */
665 n_bits = db->n_bits;
666 tgtbitno = 32 - n_bits; /* bitno when we have a code */
667
668 printk(KERN_DEBUG "bsd_decompress called\n");
669
670 if (!skb_in || !skb_out) {
671 printk(KERN_ERR "bsd_decompress called with NULL parameter\n");
672 return DECOMP_ERROR;
673 }
674
675 /*
676 * Get the sequence number.
677 */
678 if ((p = skb_pull(skb_in, 2)) == NULL) {
679 return DECOMP_ERROR;
680 }
681 p -= 2;
682 seq = (p[0] << 8) + p[1];
683 ilen = skb_in->len;
684 ibuf = skb_in->data;
685
686 /*
687 * Check the sequence number and give up if it differs from
688 * the value we're expecting.
689 */
690 if (seq != db->seqno) {
691 if (db->debug) {
692 printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n",
693 db->unit, seq, db->seqno - 1);
694 }
695 return DECOMP_ERROR;
696 }
697
698 ++db->seqno;
699 db->bytes_out += ilen;
700
701 if (skb_tailroom(skb_out) > 0)
702 skb_put_u8(skb_out, 0);
703 else
704 return DECOMP_ERR_NOMEM;
705
706 oldcode = CLEAR;
707
708 /*
709 * Keep the checkpoint correctly so that incompressible packets
710 * clear the dictionary at the proper times.
711 */
712
713 for (;;) {
714 if (ilen-- <= 0) {
715 db->in_count += (skb_out->len - 1); /* don't count the header */
716 break;
717 }
718
719 /*
720 * Accumulate bytes until we have a complete code.
721 * Then get the next code, relying on the 32-bit,
722 * unsigned accm to mask the result.
723 */
724
725 bitno -= 8;
726 accm |= *ibuf++ << bitno;
727 if (tgtbitno < bitno)
728 continue;
729
730 incode = accm >> tgtbitno;
731 accm <<= n_bits;
732 bitno += n_bits;
733
734 /*
735 * The dictionary must only be cleared at the end of a packet.
736 */
737
738 if (incode == CLEAR) {
739 if (ilen > 0) {
740 if (db->debug)
741 printk(KERN_DEBUG "bsd_decomp%d: bad CLEAR\n", db->unit);
742 return DECOMP_FATALERROR; /* probably a bug */
743 }
744 bsd_clear(db);
745 break;
746 }
747
748 if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
749 || (incode > max_ent && oldcode == CLEAR)) {
750 if (db->debug) {
751 printk(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
752 db->unit, incode, oldcode);
753 printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n",
754 max_ent, skb_out->len, db->seqno);
755 }
756 return DECOMP_FATALERROR; /* probably a bug */
757 }
758
759 /* Special case for KwKwK string. */
760 if (incode > max_ent) {
761 finchar = oldcode;
762 extra = 1;
763 } else {
764 finchar = incode;
765 extra = 0;
766 }
767
768 codelen = *(lens_ptr(db, finchar));
769 if (skb_tailroom(skb_out) < codelen + extra) {
770 if (db->debug) {
771 printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit);
772 #ifdef DEBUG
773 printk(KERN_DEBUG " len=%d, finchar=0x%x, codelen=%d,skblen=%d\n",
774 ilen, finchar, codelen, skb_out->len);
775 #endif
776 }
777 return DECOMP_FATALERROR;
778 }
779
780 /*
781 * Decode this code and install it in the decompressed buffer.
782 */
783
784 p = skb_put(skb_out, codelen);
785 p += codelen;
786 while (finchar > LAST) {
787 struct bsd_dict *dictp2 = dict_ptr(db, finchar);
788
789 dictp = dict_ptr(db, dictp2->cptr);
790
791 #ifdef DEBUG
792 if (--codelen <= 0 || dictp->codem1 != finchar - 1) {
793 if (codelen <= 0) {
794 printk(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit);
795 printk(KERN_ERR "0x%x at 0x%x by 0x%x, max_ent=0x%x\n", incode, finchar, dictp2->cptr, max_ent);
796 } else {
797 if (dictp->codem1 != finchar - 1) {
798 printk(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", db->unit, incode, finchar);
799 printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1);
800 }
801 }
802 return DECOMP_FATALERROR;
803 }
804 #endif
805
806 {
807 u32 fcode = dictp->fcode;
808 *--p = (fcode >> 16) & 0xff;
809 finchar = fcode & 0xffff;
810 }
811 }
812 *--p = finchar;
813
814 #ifdef DEBUG
815 if (--codelen != 0)
816 printk(KERN_ERR "bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", db->unit, codelen, incode, max_ent);
817 #endif
818
819 if (extra) /* the KwKwK case again */
820 skb_put_u8(skb_out, finchar);
821
822 /*
823 * If not first code in a packet, and
824 * if not out of code space, then allocate a new code.
825 *
826 * Keep the hash table correct so it can be used
827 * with uncompressed packets.
828 */
829 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
830 struct bsd_dict *dictp2, *dictp3;
831 u16 *lens1, *lens2;
832 unsigned long fcode;
833 int hval, disp, indx;
834
835 fcode = BSD_KEY(oldcode, finchar);
836 hval = BSD_HASH(oldcode, finchar, db->hshift);
837 dictp = dict_ptr(db, hval);
838
839 /* look for a free hash table entry */
840 if (dictp->codem1 < max_ent) {
841 disp = (hval == 0) ? 1 : hval;
842 do {
843 hval += disp;
844 if (hval >= db->hsize)
845 hval -= db->hsize;
846 dictp = dict_ptr(db, hval);
847 } while (dictp->codem1 < max_ent);
848 }
849
850 /*
851 * Invalidate previous hash table entry
852 * assigned this code, and then take it over
853 */
854
855 dictp2 = dict_ptr(db, max_ent + 1);
856 indx = dictp2->cptr;
857 dictp3 = dict_ptr(db, indx);
858
859 if (dictp3->codem1 == max_ent)
860 dictp3->codem1 = BADCODEM1;
861
862 dictp2->cptr = hval;
863 dictp->codem1 = max_ent;
864 dictp->fcode = fcode;
865 db->max_ent = ++max_ent;
866
867 /* Update the length of this string. */
868 lens1 = lens_ptr(db, max_ent);
869 lens2 = lens_ptr(db, oldcode);
870 *lens1 = *lens2 + 1;
871
872 /* Expand code size if needed. */
873 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
874 db->n_bits = ++n_bits;
875 tgtbitno = 32-n_bits;
876 }
877 }
878 oldcode = incode;
879 }
880
881 ++db->comp_count;
882 ++db->uncomp_count;
883 db->comp_bytes += skb_in->len - BSD_OVHD;
884 db->uncomp_bytes += skb_out->len;
885
886 if (bsd_check(db)) {
887 if (db->debug)
888 printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n",
889 db->unit, db->seqno - 1);
890 }
891 return skb_out->len;
892 }
893
894 /*************************************************************
895 * Table of addresses for the BSD compression module
896 *************************************************************/
897
898 static struct isdn_ppp_compressor ippp_bsd_compress = {
899 .owner = THIS_MODULE,
900 .num = CI_BSD_COMPRESS,
901 .alloc = bsd_alloc,
902 .free = bsd_free,
903 .init = bsd_init,
904 .reset = bsd_reset,
905 .compress = bsd_compress,
906 .decompress = bsd_decompress,
907 .incomp = bsd_incomp,
908 .stat = bsd_stats,
909 };
910
911 /*************************************************************
912 * Module support routines
913 *************************************************************/
914
isdn_bsdcomp_init(void)915 static int __init isdn_bsdcomp_init(void)
916 {
917 int answer = isdn_ppp_register_compressor(&ippp_bsd_compress);
918 if (answer == 0)
919 printk(KERN_INFO "PPP BSD Compression module registered\n");
920 return answer;
921 }
922
isdn_bsdcomp_exit(void)923 static void __exit isdn_bsdcomp_exit(void)
924 {
925 isdn_ppp_unregister_compressor(&ippp_bsd_compress);
926 }
927
928 module_init(isdn_bsdcomp_init);
929 module_exit(isdn_bsdcomp_exit);
930