2 * BSD compression module
4 * Patched version for ISDN syncPPP written 1997/1998 by Michael Hipp
5 * The whole module is now SKB based.
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..
18 * Original copyright notice:
20 * Copyright (c) 1985, 1986 The Regents of the University of California.
21 * All rights reserved.
23 * This code is derived from software contributed to Berkeley by
24 * James A. Woods, derived from original work by Spencer Thomas
27 * Redistribution and use in source and binary forms, with or without
28 * modification, are permitted provided that the following conditions
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.
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
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>
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>
72 #include <asm/byteorder.h>
73 #include <asm/types.h>
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>
84 #include <linux/ppp_defs.h>
86 #include <linux/isdn.h>
87 #include <linux/isdn_ppp.h>
89 #include <linux/tcp.h>
90 #include <linux/if_arp.h>
91 #include <linux/ppp-comp.h>
95 MODULE_DESCRIPTION("ISDN4Linux: BSD Compression for PPP over ISDN");
96 MODULE_LICENSE("Dual BSD/GPL");
98 #define BSD_VERSION(x) ((x) >> 5)
99 #define BSD_NBITS(x) ((x) & 0x1F)
101 #define BSD_CURRENT_VERSION 1
106 * A dictionary for doing BSD compress.
111 u16 codem1; /* output of hash table -1 */
112 u16 cptr; /* map code to hash table entry */
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 */
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
149 * the next two codes should not be changed lightly, as they must not
150 * lie within the contiguous general code space.
152 #define CLEAR 256 /* table clear output code */
153 #define FIRST 257 /* first free entry */
156 #define MAXCODE(b) ((1 << (b)) - 1)
157 #define BADCODEM1 MAXCODE(MAX_BSD_BITS)
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))
164 #define CHECK_GAP 10000 /* Ratio check interval */
166 #define RATIO_SCALE_LOG 8
167 #define RATIO_SCALE (1 << RATIO_SCALE_LOG)
168 #define RATIO_MAX (0x7fffffff >> RATIO_SCALE_LOG)
171 * clear the dictionary
174 static void bsd_clear(struct bsd_db *db)
177 db->max_ent = FIRST - 1;
178 db->n_bits = BSD_INIT_BITS;
181 db->incomp_count = 0;
183 db->checkpoint = CHECK_GAP;
187 * If the dictionary is full, then see if it is time to reset it.
189 * Compute the compression ratio using fixed-point arithmetic
190 * with 8 fractional bits.
192 * Since we have an infinite stream instead of a single file,
193 * watch only the local compression ratio.
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.
199 static int bsd_check(struct bsd_db *db) /* 1=output CLEAR */
201 unsigned int new_ratio;
203 if (db->in_count >= db->checkpoint)
205 /* age the ratio by limiting the size of the counts */
206 if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
208 db->in_count -= (db->in_count >> 2);
209 db->bytes_out -= (db->bytes_out >> 2);
212 db->checkpoint = db->in_count + CHECK_GAP;
214 if (db->max_ent >= db->maxmaxcode)
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.
220 * This does not overflow, because
221 * db->in_count <= RATIO_MAX.
224 new_ratio = db->in_count << RATIO_SCALE_LOG;
225 if (db->bytes_out != 0)
227 new_ratio /= db->bytes_out;
230 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
235 db->ratio = new_ratio;
245 static void bsd_stats(void *state, struct compstat *stats)
247 struct bsd_db *db = (struct bsd_db *) state;
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;
260 * Reset state, as on a CCP ResetReq.
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)
266 struct bsd_db *db = (struct bsd_db *) state;
274 * Release the compression structure
276 static void bsd_free(void *state)
278 struct bsd_db *db = (struct bsd_db *) state;
282 * Release the dictionary
288 * Release the string buffer
294 * Finally release the structure itself.
302 * Allocate space for a (de) compressor.
304 static void *bsd_alloc(struct isdn_ppp_comp_data *data)
307 unsigned int hsize, hshift, maxmaxcode;
311 static unsigned int htab[][2] = {
312 { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } ,
313 { 9001 , 5 } , { 18013 , 6 } , { 35023 , 7 } , { 69001 , 8 }
316 if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
317 || BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
320 bits = BSD_NBITS(data->options[0]);
322 if (bits < 9 || bits > 15)
325 hsize = htab[bits - 9][0];
326 hshift = htab[bits - 9][1];
329 * Allocate the main control structure for this instance.
331 maxmaxcode = MAXCODE(bits);
332 db = kzalloc(sizeof(struct bsd_db), GFP_KERNEL);
336 db->xmit = data->flags & IPPP_COMP_FLAG_XMIT;
337 decomp = db->xmit ? 0 : 1;
340 * Allocate space for the dictionary. This may be more than one page in
343 db->dict = vmalloc(hsize * sizeof(struct bsd_dict));
350 * If this is the compression buffer then there is no length data.
351 * For decompression, the length information is needed as well.
356 db->lens = vmalloc((maxmaxcode + 1) * sizeof(db->lens[0]));
364 * Initialize the data information for the compression code
366 db->totlen = sizeof(struct bsd_db) + (sizeof(struct bsd_dict) * hsize);
369 db->maxmaxcode = maxmaxcode;
376 * Initialize the database.
378 static int bsd_init(void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
380 struct bsd_db *db = state;
384 if (!state || !data) {
385 printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n", unit, (long)state, (long)data);
389 decomp = db->xmit ? 0 : 1;
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);
400 for (indx = LAST; indx >= 0; indx--)
404 while (indx-- != 0) {
405 db->dict[indx].codem1 = BADCODEM1;
406 db->dict[indx].cptr = 0;
414 bsd_reset(db, 0, 0, NULL, 0, NULL);
420 * Obtain pointers to the various structures in the compression tables
423 #define dict_ptrx(p, idx) &(p->dict[idx])
424 #define lens_ptrx(p, idx) &(p->lens[idx])
427 static unsigned short *lens_ptr(struct bsd_db *db, int idx)
429 if ((unsigned int) idx > (unsigned int) db->maxmaxcode) {
430 printk(KERN_DEBUG "<9>ppp: lens_ptr(%d) > max\n", idx);
433 return lens_ptrx(db, idx);
436 static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
438 if ((unsigned int) idx >= (unsigned int) db->hsize) {
439 printk(KERN_DEBUG "<9>ppp: dict_ptr(%d) > max\n", idx);
442 return dict_ptrx(db, idx);
446 #define lens_ptr(db, idx) lens_ptrx(db, idx)
447 #define dict_ptr(db, idx) dict_ptrx(db, idx)
453 static int bsd_compress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out, int proto)
457 unsigned int max_ent;
463 struct bsd_dict *dictp;
465 int hval, disp, ilen, mxcode;
466 unsigned char *rptr = skb_in->data;
467 int isize = skb_in->len;
469 #define OUTPUT(ent) \
472 accm |= ((ent) << bitno); \
474 if (skb_out && skb_tailroom(skb_out) > 0) \
475 *(skb_put(skb_out, 1)) = (unsigned char)(accm >> 24); \
478 } while (bitno <= 24); \
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.
486 printk(KERN_DEBUG "bsd_compress called with %x\n", proto);
489 if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1))
492 db = (struct bsd_db *) state;
494 max_ent = db->max_ent;
498 mxcode = MAXCODE(n_bits);
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;
509 ilen = ++isize; /* This is off by one, but that is what is in draft! */
513 fcode = BSD_KEY(ent, c);
514 hval = BSD_HASH(ent, c, hshift);
515 dictp = dict_ptr(db, hval);
517 /* Validate and then check the entry. */
518 if (dictp->codem1 >= max_ent)
521 if (dictp->fcode == fcode) {
522 ent = dictp->codem1 + 1;
523 continue; /* found (prefix,suffix) */
526 /* continue probing until a match or invalid entry */
527 disp = (hval == 0) ? 1 : hval;
531 if (hval >= db->hsize)
533 dictp = dict_ptr(db, hval);
534 if (dictp->codem1 >= max_ent)
536 } while (dictp->fcode != fcode);
538 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
542 OUTPUT(ent); /* output the prefix */
544 /* code -> hashtable */
545 if (max_ent < db->maxmaxcode) {
546 struct bsd_dict *dictp2;
547 struct bsd_dict *dictp3;
550 /* expand code size if needed */
551 if (max_ent >= mxcode) {
552 db->n_bits = ++n_bits;
553 mxcode = MAXCODE(n_bits);
557 * Invalidate old hash table entry using
558 * this code, and then take it over.
560 dictp2 = dict_ptr(db, max_ent + 1);
562 dictp3 = dict_ptr(db, indx);
564 if (dictp3->codem1 == max_ent)
565 dictp3->codem1 = BADCODEM1;
568 dictp->codem1 = max_ent;
569 dictp->fcode = fcode;
570 db->max_ent = ++max_ent;
573 unsigned short *len1 = lens_ptr(db, max_ent);
574 unsigned short *len2 = lens_ptr(db, ent);
581 OUTPUT(ent); /* output the last code */
584 db->bytes_out += skb_out->len; /* Do not count bytes from here */
585 db->uncomp_bytes += isize;
586 db->in_count += isize;
591 ++db->bytes_out; /* must be set before calling bsd_check */
594 * Generate the clear command if needed
601 * Pad dribble bits of last code with ones.
602 * Do not emit a completely useless byte of ones.
604 if (bitno < 32 && skb_out && skb_tailroom(skb_out) > 0)
605 *(skb_put(skb_out, 1)) = (unsigned char)((accm | (0xff << (bitno - 8))) >> 24);
608 * Increase code size if we would have without the packet
609 * boundary because the decompressor will do so.
611 if (max_ent >= mxcode && max_ent < db->maxmaxcode)
614 /* If output length is too large then this is an incompressible frame. */
615 if (!skb_out || skb_out->len >= skb_in->len) {
617 db->incomp_bytes += isize;
621 /* Count the number of compressed frames */
623 db->comp_bytes += skb_out->len;
630 * Update the "BSD Compress" dictionary on the receiver for
631 * incompressible data by pretending to compress the incoming data.
633 static void bsd_incomp(void *state, struct sk_buff *skb_in, int proto)
635 bsd_compress(state, skb_in, NULL, proto);
639 * Decompress "BSD Compress".
641 static int bsd_decompress(void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,
642 struct isdn_ppp_resetparams *rsparm)
645 unsigned int max_ent;
647 unsigned int bitno; /* 1st valid bit in accm */
649 unsigned int tgtbitno; /* bitno when we have a code */
650 struct bsd_dict *dictp;
653 unsigned int oldcode;
654 unsigned int finchar;
655 unsigned char *p, *ibuf;
660 db = (struct bsd_db *) state;
661 max_ent = db->max_ent;
663 bitno = 32; /* 1st valid bit in accm */
665 tgtbitno = 32 - n_bits; /* bitno when we have a code */
667 printk(KERN_DEBUG "bsd_decompress called\n");
669 if (!skb_in || !skb_out) {
670 printk(KERN_ERR "bsd_decompress called with NULL parameter\n");
675 * Get the sequence number.
677 if ((p = skb_pull(skb_in, 2)) == NULL) {
681 seq = (p[0] << 8) + p[1];
686 * Check the sequence number and give up if it differs from
687 * the value we're expecting.
689 if (seq != db->seqno) {
691 printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n",
692 db->unit, seq, db->seqno - 1);
698 db->bytes_out += ilen;
700 if (skb_tailroom(skb_out) > 0)
701 *(skb_put(skb_out, 1)) = 0;
703 return DECOMP_ERR_NOMEM;
708 * Keep the checkpoint correctly so that incompressible packets
709 * clear the dictionary at the proper times.
714 db->in_count += (skb_out->len - 1); /* don't count the header */
719 * Accumulate bytes until we have a complete code.
720 * Then get the next code, relying on the 32-bit,
721 * unsigned accm to mask the result.
725 accm |= *ibuf++ << bitno;
726 if (tgtbitno < bitno)
729 incode = accm >> tgtbitno;
734 * The dictionary must only be cleared at the end of a packet.
737 if (incode == CLEAR) {
740 printk(KERN_DEBUG "bsd_decomp%d: bad CLEAR\n", db->unit);
741 return DECOMP_FATALERROR; /* probably a bug */
747 if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
748 || (incode > max_ent && oldcode == CLEAR)) {
750 printk(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
751 db->unit, incode, oldcode);
752 printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n",
753 max_ent, skb_out->len, db->seqno);
755 return DECOMP_FATALERROR; /* probably a bug */
758 /* Special case for KwKwK string. */
759 if (incode > max_ent) {
767 codelen = *(lens_ptr(db, finchar));
768 if (skb_tailroom(skb_out) < codelen + extra) {
770 printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit);
772 printk(KERN_DEBUG " len=%d, finchar=0x%x, codelen=%d,skblen=%d\n",
773 ilen, finchar, codelen, skb_out->len);
776 return DECOMP_FATALERROR;
780 * Decode this code and install it in the decompressed buffer.
783 p = skb_put(skb_out, codelen);
785 while (finchar > LAST) {
786 struct bsd_dict *dictp2 = dict_ptr(db, finchar);
788 dictp = dict_ptr(db, dictp2->cptr);
791 if (--codelen <= 0 || dictp->codem1 != finchar - 1) {
793 printk(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit);
794 printk(KERN_ERR "0x%x at 0x%x by 0x%x, max_ent=0x%x\n", incode, finchar, dictp2->cptr, max_ent);
796 if (dictp->codem1 != finchar - 1) {
797 printk(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ", db->unit, incode, finchar);
798 printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1);
801 return DECOMP_FATALERROR;
806 u32 fcode = dictp->fcode;
807 *--p = (fcode >> 16) & 0xff;
808 finchar = fcode & 0xffff;
815 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 if (extra) /* the KwKwK case again */
819 *(skb_put(skb_out, 1)) = finchar;
822 * If not first code in a packet, and
823 * if not out of code space, then allocate a new code.
825 * Keep the hash table correct so it can be used
826 * with uncompressed packets.
828 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
829 struct bsd_dict *dictp2, *dictp3;
832 int hval, disp, indx;
834 fcode = BSD_KEY(oldcode, finchar);
835 hval = BSD_HASH(oldcode, finchar, db->hshift);
836 dictp = dict_ptr(db, hval);
838 /* look for a free hash table entry */
839 if (dictp->codem1 < max_ent) {
840 disp = (hval == 0) ? 1 : hval;
843 if (hval >= db->hsize)
845 dictp = dict_ptr(db, hval);
846 } while (dictp->codem1 < max_ent);
850 * Invalidate previous hash table entry
851 * assigned this code, and then take it over
854 dictp2 = dict_ptr(db, max_ent + 1);
856 dictp3 = dict_ptr(db, indx);
858 if (dictp3->codem1 == max_ent)
859 dictp3->codem1 = BADCODEM1;
862 dictp->codem1 = max_ent;
863 dictp->fcode = fcode;
864 db->max_ent = ++max_ent;
866 /* Update the length of this string. */
867 lens1 = lens_ptr(db, max_ent);
868 lens2 = lens_ptr(db, oldcode);
871 /* Expand code size if needed. */
872 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
873 db->n_bits = ++n_bits;
874 tgtbitno = 32-n_bits;
882 db->comp_bytes += skb_in->len - BSD_OVHD;
883 db->uncomp_bytes += skb_out->len;
887 printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n",
888 db->unit, db->seqno - 1);
893 /*************************************************************
894 * Table of addresses for the BSD compression module
895 *************************************************************/
897 static struct isdn_ppp_compressor ippp_bsd_compress = {
898 .owner = THIS_MODULE,
899 .num = CI_BSD_COMPRESS,
904 .compress = bsd_compress,
905 .decompress = bsd_decompress,
906 .incomp = bsd_incomp,
910 /*************************************************************
911 * Module support routines
912 *************************************************************/
914 static int __init isdn_bsdcomp_init(void)
916 int answer = isdn_ppp_register_compressor(&ippp_bsd_compress);
918 printk(KERN_INFO "PPP BSD Compression module registered\n");
922 static void __exit isdn_bsdcomp_exit(void)
924 isdn_ppp_unregister_compressor(&ippp_bsd_compress);
927 module_init(isdn_bsdcomp_init);
928 module_exit(isdn_bsdcomp_exit);