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(array_size(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(array_size(sizeof(db->lens[0]),
357 maxmaxcode + 1));
358 if (!db->lens) {
359 bsd_free(db);
360 return (NULL);
361 }
362 }
363
364 /*
365 * Initialize the data information for the compression code
366 */
367 db->totlen = sizeof(struct bsd_db) + (sizeof(struct bsd_dict) * hsize);
368 db->hsize = hsize;
369 db->hshift = hshift;
370 db->maxmaxcode = maxmaxcode;
371 db->maxbits = bits;
372
373 return (void *)db;
374 }
375
376 /*
377 * Initialize the database.
378 */
bsd_init(void * state,struct isdn_ppp_comp_data * data,int unit,int debug)379 static int bsd_init(void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
380 {
381 struct bsd_db *db = state;
382 int indx;
383 int decomp;
384
385 if (!state || !data) {
386 printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n", unit, (long)state, (long)data);
387 return 0;
388 }
389
390 decomp = db->xmit ? 0 : 1;
391
392 if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
393 || (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
394 || (BSD_NBITS(data->options[0]) != db->maxbits)
395 || (decomp && db->lens == NULL)) {
396 printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n", data->optlen, data->num, data->options[0], decomp, (unsigned long)db->lens);
397 return 0;
398 }
399
400 if (decomp)
401 for (indx = LAST; indx >= 0; indx--)
402 db->lens[indx] = 1;
403
404 indx = db->hsize;
405 while (indx-- != 0) {
406 db->dict[indx].codem1 = BADCODEM1;
407 db->dict[indx].cptr = 0;
408 }
409
410 db->unit = unit;
411 db->mru = 0;
412
413 db->debug = 1;
414
415 bsd_reset(db, 0, 0, NULL, 0, NULL);
416
417 return 1;
418 }
419
420 /*
421 * Obtain pointers to the various structures in the compression tables
422 */
423
424 #define dict_ptrx(p, idx) &(p->dict[idx])
425 #define lens_ptrx(p, idx) &(p->lens[idx])
426
427 #ifdef DEBUG
lens_ptr(struct bsd_db * db,int idx)428 static unsigned short *lens_ptr(struct bsd_db *db, int idx)
429 {
430 if ((unsigned int) idx > (unsigned int) db->maxmaxcode) {
431 printk(KERN_DEBUG "<9>ppp: lens_ptr(%d) > max\n", idx);
432 idx = 0;
433 }
434 return lens_ptrx(db, idx);
435 }
436
dict_ptr(struct bsd_db * db,int idx)437 static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
438 {
439 if ((unsigned int) idx >= (unsigned int) db->hsize) {
440 printk(KERN_DEBUG "<9>ppp: dict_ptr(%d) > max\n", idx);
441 idx = 0;
442 }
443 return dict_ptrx(db, idx);
444 }
445
446 #else
447 #define lens_ptr(db, idx) lens_ptrx(db, idx)
448 #define dict_ptr(db, idx) dict_ptrx(db, idx)
449 #endif
450
451 /*
452 * compress a packet
453 */
bsd_compress(void * state,struct sk_buff * skb_in,struct sk_buff * skb_out,int proto)454 static int bsd_compress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out, int proto)
455 {
456 struct bsd_db *db;
457 int hshift;
458 unsigned int max_ent;
459 unsigned int n_bits;
460 unsigned int bitno;
461 unsigned long accm;
462 int ent;
463 unsigned long fcode;
464 struct bsd_dict *dictp;
465 unsigned char c;
466 int hval, disp, ilen, mxcode;
467 unsigned char *rptr = skb_in->data;
468 int isize = skb_in->len;
469
470 #define OUTPUT(ent) \
471 { \
472 bitno -= n_bits; \
473 accm |= ((ent) << bitno); \
474 do { \
475 if (skb_out && skb_tailroom(skb_out) > 0) \
476 skb_put_u8(skb_out, (u8)(accm >> 24)); \
477 accm <<= 8; \
478 bitno += 8; \
479 } while (bitno <= 24); \
480 }
481
482 /*
483 * If the protocol is not in the range we're interested in,
484 * just return without compressing the packet. If it is,
485 * the protocol becomes the first byte to compress.
486 */
487 printk(KERN_DEBUG "bsd_compress called with %x\n", proto);
488
489 ent = proto;
490 if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1))
491 return 0;
492
493 db = (struct bsd_db *) state;
494 hshift = db->hshift;
495 max_ent = db->max_ent;
496 n_bits = db->n_bits;
497 bitno = 32;
498 accm = 0;
499 mxcode = MAXCODE(n_bits);
500
501 /* This is the PPP header information */
502 if (skb_out && skb_tailroom(skb_out) >= 2) {
503 char *v = skb_put(skb_out, 2);
504 /* we only push our own data on the header,
505 AC,PC and protos is pushed by caller */
506 v[0] = db->seqno >> 8;
507 v[1] = db->seqno;
508 }
509
510 ilen = ++isize; /* This is off by one, but that is what is in draft! */
511
512 while (--ilen > 0) {
513 c = *rptr++;
514 fcode = BSD_KEY(ent, c);
515 hval = BSD_HASH(ent, c, hshift);
516 dictp = dict_ptr(db, hval);
517
518 /* Validate and then check the entry. */
519 if (dictp->codem1 >= max_ent)
520 goto nomatch;
521
522 if (dictp->fcode == fcode) {
523 ent = dictp->codem1 + 1;
524 continue; /* found (prefix,suffix) */
525 }
526
527 /* continue probing until a match or invalid entry */
528 disp = (hval == 0) ? 1 : hval;
529
530 do {
531 hval += disp;
532 if (hval >= db->hsize)
533 hval -= db->hsize;
534 dictp = dict_ptr(db, hval);
535 if (dictp->codem1 >= max_ent)
536 goto nomatch;
537 } while (dictp->fcode != fcode);
538
539 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
540 continue;
541
542 nomatch:
543 OUTPUT(ent); /* output the prefix */
544
545 /* code -> hashtable */
546 if (max_ent < db->maxmaxcode) {
547 struct bsd_dict *dictp2;
548 struct bsd_dict *dictp3;
549 int indx;
550
551 /* expand code size if needed */
552 if (max_ent >= mxcode) {
553 db->n_bits = ++n_bits;
554 mxcode = MAXCODE(n_bits);
555 }
556
557 /*
558 * Invalidate old hash table entry using
559 * this code, and then take it over.
560 */
561 dictp2 = dict_ptr(db, max_ent + 1);
562 indx = dictp2->cptr;
563 dictp3 = dict_ptr(db, indx);
564
565 if (dictp3->codem1 == max_ent)
566 dictp3->codem1 = BADCODEM1;
567
568 dictp2->cptr = hval;
569 dictp->codem1 = max_ent;
570 dictp->fcode = fcode;
571 db->max_ent = ++max_ent;
572
573 if (db->lens) {
574 unsigned short *len1 = lens_ptr(db, max_ent);
575 unsigned short *len2 = lens_ptr(db, ent);
576 *len1 = *len2 + 1;
577 }
578 }
579 ent = c;
580 }
581
582 OUTPUT(ent); /* output the last code */
583
584 if (skb_out)
585 db->bytes_out += skb_out->len; /* Do not count bytes from here */
586 db->uncomp_bytes += isize;
587 db->in_count += isize;
588 ++db->uncomp_count;
589 ++db->seqno;
590
591 if (bitno < 32)
592 ++db->bytes_out; /* must be set before calling bsd_check */
593
594 /*
595 * Generate the clear command if needed
596 */
597
598 if (bsd_check(db))
599 OUTPUT(CLEAR);
600
601 /*
602 * Pad dribble bits of last code with ones.
603 * Do not emit a completely useless byte of ones.
604 */
605 if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0)
606 skb_put_u8(skb_out,
607 (unsigned char)((accm | (0xff << (bitno - 8))) >> 24));
608
609 /*
610 * Increase code size if we would have without the packet
611 * boundary because the decompressor will do so.
612 */
613 if (max_ent >= mxcode && max_ent < db->maxmaxcode)
614 db->n_bits++;
615
616 /* If output length is too large then this is an incompressible frame. */
617 if (!skb_out || skb_out->len >= skb_in->len) {
618 ++db->incomp_count;
619 db->incomp_bytes += isize;
620 return 0;
621 }
622
623 /* Count the number of compressed frames */
624 ++db->comp_count;
625 db->comp_bytes += skb_out->len;
626 return skb_out->len;
627
628 #undef OUTPUT
629 }
630
631 /*
632 * Update the "BSD Compress" dictionary on the receiver for
633 * incompressible data by pretending to compress the incoming data.
634 */
bsd_incomp(void * state,struct sk_buff * skb_in,int proto)635 static void bsd_incomp(void *state, struct sk_buff *skb_in, int proto)
636 {
637 bsd_compress(state, skb_in, NULL, proto);
638 }
639
640 /*
641 * Decompress "BSD Compress".
642 */
bsd_decompress(void * state,struct sk_buff * skb_in,struct sk_buff * skb_out,struct isdn_ppp_resetparams * rsparm)643 static int bsd_decompress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,
644 struct isdn_ppp_resetparams *rsparm)
645 {
646 struct bsd_db *db;
647 unsigned int max_ent;
648 unsigned long accm;
649 unsigned int bitno; /* 1st valid bit in accm */
650 unsigned int n_bits;
651 unsigned int tgtbitno; /* bitno when we have a code */
652 struct bsd_dict *dictp;
653 int seq;
654 unsigned int incode;
655 unsigned int oldcode;
656 unsigned int finchar;
657 unsigned char *p, *ibuf;
658 int ilen;
659 int codelen;
660 int extra;
661
662 db = (struct bsd_db *) state;
663 max_ent = db->max_ent;
664 accm = 0;
665 bitno = 32; /* 1st valid bit in accm */
666 n_bits = db->n_bits;
667 tgtbitno = 32 - n_bits; /* bitno when we have a code */
668
669 printk(KERN_DEBUG "bsd_decompress called\n");
670
671 if (!skb_in || !skb_out) {
672 printk(KERN_ERR "bsd_decompress called with NULL parameter\n");
673 return DECOMP_ERROR;
674 }
675
676 /*
677 * Get the sequence number.
678 */
679 if ((p = skb_pull(skb_in, 2)) == NULL) {
680 return DECOMP_ERROR;
681 }
682 p -= 2;
683 seq = (p[0] << 8) + p[1];
684 ilen = skb_in->len;
685 ibuf = skb_in->data;
686
687 /*
688 * Check the sequence number and give up if it differs from
689 * the value we're expecting.
690 */
691 if (seq != db->seqno) {
692 if (db->debug) {
693 printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n",
694 db->unit, seq, db->seqno - 1);
695 }
696 return DECOMP_ERROR;
697 }
698
699 ++db->seqno;
700 db->bytes_out += ilen;
701
702 if (skb_tailroom(skb_out) > 0)
703 skb_put_u8(skb_out, 0);
704 else
705 return DECOMP_ERR_NOMEM;
706
707 oldcode = CLEAR;
708
709 /*
710 * Keep the checkpoint correctly so that incompressible packets
711 * clear the dictionary at the proper times.
712 */
713
714 for (;;) {
715 if (ilen-- <= 0) {
716 db->in_count += (skb_out->len - 1); /* don't count the header */
717 break;
718 }
719
720 /*
721 * Accumulate bytes until we have a complete code.
722 * Then get the next code, relying on the 32-bit,
723 * unsigned accm to mask the result.
724 */
725
726 bitno -= 8;
727 accm |= *ibuf++ << bitno;
728 if (tgtbitno < bitno)
729 continue;
730
731 incode = accm >> tgtbitno;
732 accm <<= n_bits;
733 bitno += n_bits;
734
735 /*
736 * The dictionary must only be cleared at the end of a packet.
737 */
738
739 if (incode == CLEAR) {
740 if (ilen > 0) {
741 if (db->debug)
742 printk(KERN_DEBUG "bsd_decomp%d: bad CLEAR\n", db->unit);
743 return DECOMP_FATALERROR; /* probably a bug */
744 }
745 bsd_clear(db);
746 break;
747 }
748
749 if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
750 || (incode > max_ent && oldcode == CLEAR)) {
751 if (db->debug) {
752 printk(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
753 db->unit, incode, oldcode);
754 printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n",
755 max_ent, skb_out->len, db->seqno);
756 }
757 return DECOMP_FATALERROR; /* probably a bug */
758 }
759
760 /* Special case for KwKwK string. */
761 if (incode > max_ent) {
762 finchar = oldcode;
763 extra = 1;
764 } else {
765 finchar = incode;
766 extra = 0;
767 }
768
769 codelen = *(lens_ptr(db, finchar));
770 if (skb_tailroom(skb_out) < codelen + extra) {
771 if (db->debug) {
772 printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit);
773 #ifdef DEBUG
774 printk(KERN_DEBUG " len=%d, finchar=0x%x, codelen=%d,skblen=%d\n",
775 ilen, finchar, codelen, skb_out->len);
776 #endif
777 }
778 return DECOMP_FATALERROR;
779 }
780
781 /*
782 * Decode this code and install it in the decompressed buffer.
783 */
784
785 p = skb_put(skb_out, codelen);
786 p += codelen;
787 while (finchar > LAST) {
788 struct bsd_dict *dictp2 = dict_ptr(db, finchar);
789
790 dictp = dict_ptr(db, dictp2->cptr);
791
792 #ifdef DEBUG
793 if (--codelen <= 0 || dictp->codem1 != finchar - 1) {
794 if (codelen <= 0) {
795 printk(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit);
796 printk(KERN_ERR "0x%x at 0x%x by 0x%x, max_ent=0x%x\n", incode, finchar, dictp2->cptr, max_ent);
797 } else {
798 if (dictp->codem1 != finchar - 1) {
799 printk(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", db->unit, incode, finchar);
800 printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1);
801 }
802 }
803 return DECOMP_FATALERROR;
804 }
805 #endif
806
807 {
808 u32 fcode = dictp->fcode;
809 *--p = (fcode >> 16) & 0xff;
810 finchar = fcode & 0xffff;
811 }
812 }
813 *--p = finchar;
814
815 #ifdef DEBUG
816 if (--codelen != 0)
817 printk(KERN_ERR "bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n", db->unit, codelen, incode, max_ent);
818 #endif
819
820 if (extra) /* the KwKwK case again */
821 skb_put_u8(skb_out, finchar);
822
823 /*
824 * If not first code in a packet, and
825 * if not out of code space, then allocate a new code.
826 *
827 * Keep the hash table correct so it can be used
828 * with uncompressed packets.
829 */
830 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
831 struct bsd_dict *dictp2, *dictp3;
832 u16 *lens1, *lens2;
833 unsigned long fcode;
834 int hval, disp, indx;
835
836 fcode = BSD_KEY(oldcode, finchar);
837 hval = BSD_HASH(oldcode, finchar, db->hshift);
838 dictp = dict_ptr(db, hval);
839
840 /* look for a free hash table entry */
841 if (dictp->codem1 < max_ent) {
842 disp = (hval == 0) ? 1 : hval;
843 do {
844 hval += disp;
845 if (hval >= db->hsize)
846 hval -= db->hsize;
847 dictp = dict_ptr(db, hval);
848 } while (dictp->codem1 < max_ent);
849 }
850
851 /*
852 * Invalidate previous hash table entry
853 * assigned this code, and then take it over
854 */
855
856 dictp2 = dict_ptr(db, max_ent + 1);
857 indx = dictp2->cptr;
858 dictp3 = dict_ptr(db, indx);
859
860 if (dictp3->codem1 == max_ent)
861 dictp3->codem1 = BADCODEM1;
862
863 dictp2->cptr = hval;
864 dictp->codem1 = max_ent;
865 dictp->fcode = fcode;
866 db->max_ent = ++max_ent;
867
868 /* Update the length of this string. */
869 lens1 = lens_ptr(db, max_ent);
870 lens2 = lens_ptr(db, oldcode);
871 *lens1 = *lens2 + 1;
872
873 /* Expand code size if needed. */
874 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
875 db->n_bits = ++n_bits;
876 tgtbitno = 32-n_bits;
877 }
878 }
879 oldcode = incode;
880 }
881
882 ++db->comp_count;
883 ++db->uncomp_count;
884 db->comp_bytes += skb_in->len - BSD_OVHD;
885 db->uncomp_bytes += skb_out->len;
886
887 if (bsd_check(db)) {
888 if (db->debug)
889 printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n",
890 db->unit, db->seqno - 1);
891 }
892 return skb_out->len;
893 }
894
895 /*************************************************************
896 * Table of addresses for the BSD compression module
897 *************************************************************/
898
899 static struct isdn_ppp_compressor ippp_bsd_compress = {
900 .owner = THIS_MODULE,
901 .num = CI_BSD_COMPRESS,
902 .alloc = bsd_alloc,
903 .free = bsd_free,
904 .init = bsd_init,
905 .reset = bsd_reset,
906 .compress = bsd_compress,
907 .decompress = bsd_decompress,
908 .incomp = bsd_incomp,
909 .stat = bsd_stats,
910 };
911
912 /*************************************************************
913 * Module support routines
914 *************************************************************/
915
isdn_bsdcomp_init(void)916 static int __init isdn_bsdcomp_init(void)
917 {
918 int answer = isdn_ppp_register_compressor(&ippp_bsd_compress);
919 if (answer == 0)
920 printk(KERN_INFO "PPP BSD Compression module registered\n");
921 return answer;
922 }
923
isdn_bsdcomp_exit(void)924 static void __exit isdn_bsdcomp_exit(void)
925 {
926 isdn_ppp_unregister_compressor(&ippp_bsd_compress);
927 }
928
929 module_init(isdn_bsdcomp_init);
930 module_exit(isdn_bsdcomp_exit);
931