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linux-zen-server/drivers/net/ppp/bsd_comp.c

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2023-08-30 17:53:23 +02:00
/*
* Update: The Berkeley copyright was changed, and the change
* is retroactive to all "true" BSD software (ie everything
* from UCB as opposed to other peoples code that just carried
* the same license). The new copyright doesn't clash with the
* GPL, so the module-only restriction has been removed..
*/
/* Because this code is derived from the 4.3BSD compress source:
*
* Copyright (c) 1985, 1986 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* James A. Woods, derived from original work by Spencer Thomas
* and Joseph Orost.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* This version is for use with contiguous buffers on Linux-derived systems.
*
* ==FILEVERSION 20000226==
*
* NOTE TO MAINTAINERS:
* If you modify this file at all, please set the number above to the
* date of the modification as YYMMDD (year month day).
* bsd_comp.c is shipped with a PPP distribution as well as with
* the kernel; if everyone increases the FILEVERSION number above,
* then scripts can do the right thing when deciding whether to
* install a new bsd_comp.c file. Don't change the format of that
* line otherwise, so the installation script can recognize it.
*
* From: bsd_comp.c,v 1.3 1994/12/08 01:59:58 paulus Exp
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/string.h>
#include <linux/ppp_defs.h>
#undef PACKETPTR
#define PACKETPTR 1
#include <linux/ppp-comp.h>
#undef PACKETPTR
#include <asm/byteorder.h>
/*
* PPP "BSD compress" compression
* The differences between this compression and the classic BSD LZW
* source are obvious from the requirement that the classic code worked
* with files while this handles arbitrarily long streams that
* are broken into packets. They are:
*
* When the code size expands, a block of junk is not emitted by
* the compressor and not expected by the decompressor.
*
* New codes are not necessarily assigned every time an old
* code is output by the compressor. This is because a packet
* end forces a code to be emitted, but does not imply that a
* new sequence has been seen.
*
* The compression ratio is checked at the first end of a packet
* after the appropriate gap. Besides simplifying and speeding
* things up, this makes it more likely that the transmitter
* and receiver will agree when the dictionary is cleared when
* compression is not going well.
*/
/*
* Macros to extract protocol version and number of bits
* from the third byte of the BSD Compress CCP configuration option.
*/
#define BSD_VERSION(x) ((x) >> 5)
#define BSD_NBITS(x) ((x) & 0x1F)
#define BSD_CURRENT_VERSION 1
/*
* A dictionary for doing BSD compress.
*/
struct bsd_dict {
union { /* hash value */
unsigned long fcode;
struct {
#if defined(__LITTLE_ENDIAN) /* Little endian order */
unsigned short prefix; /* preceding code */
unsigned char suffix; /* last character of new code */
unsigned char pad;
#elif defined(__BIG_ENDIAN) /* Big endian order */
unsigned char pad;
unsigned char suffix; /* last character of new code */
unsigned short prefix; /* preceding code */
#else
#error Endianness not defined...
#endif
} hs;
} f;
unsigned short codem1; /* output of hash table -1 */
unsigned short cptr; /* map code to hash table entry */
};
struct bsd_db {
int totlen; /* length of this structure */
unsigned int hsize; /* size of the hash table */
unsigned char hshift; /* used in hash function */
unsigned char n_bits; /* current bits/code */
unsigned char maxbits; /* maximum bits/code */
unsigned char debug; /* non-zero if debug desired */
unsigned char unit; /* ppp unit number */
unsigned short seqno; /* sequence # of next packet */
unsigned int mru; /* size of receive (decompress) bufr */
unsigned int maxmaxcode; /* largest valid code */
unsigned int max_ent; /* largest code in use */
unsigned int in_count; /* uncompressed bytes, aged */
unsigned int bytes_out; /* compressed bytes, aged */
unsigned int ratio; /* recent compression ratio */
unsigned int checkpoint; /* when to next check the ratio */
unsigned int clear_count; /* times dictionary cleared */
unsigned int incomp_count; /* incompressible packets */
unsigned int incomp_bytes; /* incompressible bytes */
unsigned int uncomp_count; /* uncompressed packets */
unsigned int uncomp_bytes; /* uncompressed bytes */
unsigned int comp_count; /* compressed packets */
unsigned int comp_bytes; /* compressed bytes */
unsigned short *lens; /* array of lengths of codes */
struct bsd_dict *dict; /* dictionary */
};
#define BSD_OVHD 2 /* BSD compress overhead/packet */
#define MIN_BSD_BITS 9
#define BSD_INIT_BITS MIN_BSD_BITS
#define MAX_BSD_BITS 15
static void bsd_free (void *state);
static void *bsd_alloc(unsigned char *options, int opt_len, int decomp);
static void *bsd_comp_alloc (unsigned char *options, int opt_len);
static void *bsd_decomp_alloc (unsigned char *options, int opt_len);
static int bsd_init (void *db, unsigned char *options,
int opt_len, int unit, int debug, int decomp);
static int bsd_comp_init (void *state, unsigned char *options,
int opt_len, int unit, int opthdr, int debug);
static int bsd_decomp_init (void *state, unsigned char *options,
int opt_len, int unit, int opthdr, int mru,
int debug);
static void bsd_reset (void *state);
static void bsd_comp_stats (void *state, struct compstat *stats);
static int bsd_compress (void *state, unsigned char *rptr,
unsigned char *obuf, int isize, int osize);
static void bsd_incomp (void *state, unsigned char *ibuf, int icnt);
static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
unsigned char *obuf, int osize);
/* These are in ppp_generic.c */
extern int ppp_register_compressor (struct compressor *cp);
extern void ppp_unregister_compressor (struct compressor *cp);
/*
* the next two codes should not be changed lightly, as they must not
* lie within the contiguous general code space.
*/
#define CLEAR 256 /* table clear output code */
#define FIRST 257 /* first free entry */
#define LAST 255
#define MAXCODE(b) ((1 << (b)) - 1)
#define BADCODEM1 MAXCODE(MAX_BSD_BITS)
#define BSD_HASH(prefix,suffix,hshift) ((((unsigned long)(suffix))<<(hshift)) \
^ (unsigned long)(prefix))
#define BSD_KEY(prefix,suffix) ((((unsigned long)(suffix)) << 16) \
+ (unsigned long)(prefix))
#define CHECK_GAP 10000 /* Ratio check interval */
#define RATIO_SCALE_LOG 8
#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
/*
* clear the dictionary
*/
static void
bsd_clear(struct bsd_db *db)
{
db->clear_count++;
db->max_ent = FIRST-1;
db->n_bits = BSD_INIT_BITS;
db->bytes_out = 0;
db->in_count = 0;
db->ratio = 0;
db->checkpoint = CHECK_GAP;
}
/*
* If the dictionary is full, then see if it is time to reset it.
*
* Compute the compression ratio using fixed-point arithmetic
* with 8 fractional bits.
*
* Since we have an infinite stream instead of a single file,
* watch only the local compression ratio.
*
* Since both peers must reset the dictionary at the same time even in
* the absence of CLEAR codes (while packets are incompressible), they
* must compute the same ratio.
*/
static int bsd_check (struct bsd_db *db) /* 1=output CLEAR */
{
unsigned int new_ratio;
if (db->in_count >= db->checkpoint)
{
/* age the ratio by limiting the size of the counts */
if (db->in_count >= RATIO_MAX || db->bytes_out >= RATIO_MAX)
{
db->in_count -= (db->in_count >> 2);
db->bytes_out -= (db->bytes_out >> 2);
}
db->checkpoint = db->in_count + CHECK_GAP;
if (db->max_ent >= db->maxmaxcode)
{
/* Reset the dictionary only if the ratio is worse,
* or if it looks as if it has been poisoned
* by incompressible data.
*
* This does not overflow, because
* db->in_count <= RATIO_MAX.
*/
new_ratio = db->in_count << RATIO_SCALE_LOG;
if (db->bytes_out != 0)
{
new_ratio /= db->bytes_out;
}
if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE)
{
bsd_clear (db);
return 1;
}
db->ratio = new_ratio;
}
}
return 0;
}
/*
* Return statistics.
*/
static void bsd_comp_stats (void *state, struct compstat *stats)
{
struct bsd_db *db = (struct bsd_db *) state;
stats->unc_bytes = db->uncomp_bytes;
stats->unc_packets = db->uncomp_count;
stats->comp_bytes = db->comp_bytes;
stats->comp_packets = db->comp_count;
stats->inc_bytes = db->incomp_bytes;
stats->inc_packets = db->incomp_count;
stats->in_count = db->in_count;
stats->bytes_out = db->bytes_out;
}
/*
* Reset state, as on a CCP ResetReq.
*/
static void bsd_reset (void *state)
{
struct bsd_db *db = (struct bsd_db *) state;
bsd_clear(db);
db->seqno = 0;
db->clear_count = 0;
}
/*
* Release the compression structure
*/
static void bsd_free (void *state)
{
struct bsd_db *db = state;
if (!db)
return;
/*
* Release the dictionary
*/
vfree(db->dict);
db->dict = NULL;
/*
* Release the string buffer
*/
vfree(db->lens);
db->lens = NULL;
/*
* Finally release the structure itself.
*/
kfree(db);
}
/*
* Allocate space for a (de) compressor.
*/
static void *bsd_alloc (unsigned char *options, int opt_len, int decomp)
{
int bits;
unsigned int hsize, hshift, maxmaxcode;
struct bsd_db *db;
if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3
|| BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
{
return NULL;
}
bits = BSD_NBITS(options[2]);
switch (bits)
{
case 9: /* needs 82152 for both directions */
case 10: /* needs 84144 */
case 11: /* needs 88240 */
case 12: /* needs 96432 */
hsize = 5003;
hshift = 4;
break;
case 13: /* needs 176784 */
hsize = 9001;
hshift = 5;
break;
case 14: /* needs 353744 */
hsize = 18013;
hshift = 6;
break;
case 15: /* needs 691440 */
hsize = 35023;
hshift = 7;
break;
case 16: /* needs 1366160--far too much, */
/* hsize = 69001; */ /* and 69001 is too big for cptr */
/* hshift = 8; */ /* in struct bsd_db */
/* break; */
default:
return NULL;
}
/*
* Allocate the main control structure for this instance.
*/
maxmaxcode = MAXCODE(bits);
db = kzalloc(sizeof (struct bsd_db),
GFP_KERNEL);
if (!db)
{
return NULL;
}
/*
* Allocate space for the dictionary. This may be more than one page in
* length.
*/
db->dict = vmalloc(array_size(hsize, sizeof(struct bsd_dict)));
if (!db->dict)
{
bsd_free (db);
return NULL;
}
/*
* If this is the compression buffer then there is no length data.
*/
if (!decomp)
{
db->lens = NULL;
}
/*
* For decompression, the length information is needed as well.
*/
else
{
db->lens = vmalloc(array_size(sizeof(db->lens[0]), (maxmaxcode + 1)));
if (!db->lens)
{
bsd_free (db);
return NULL;
}
}
/*
* Initialize the data information for the compression code
*/
db->totlen = sizeof (struct bsd_db) +
(sizeof (struct bsd_dict) * hsize);
db->hsize = hsize;
db->hshift = hshift;
db->maxmaxcode = maxmaxcode;
db->maxbits = bits;
return (void *) db;
}
static void *bsd_comp_alloc (unsigned char *options, int opt_len)
{
return bsd_alloc (options, opt_len, 0);
}
static void *bsd_decomp_alloc (unsigned char *options, int opt_len)
{
return bsd_alloc (options, opt_len, 1);
}
/*
* Initialize the database.
*/
static int bsd_init (void *state, unsigned char *options,
int opt_len, int unit, int debug, int decomp)
{
struct bsd_db *db = state;
int indx;
if ((opt_len != 3) || (options[0] != CI_BSD_COMPRESS) || (options[1] != 3)
|| (BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
|| (BSD_NBITS(options[2]) != db->maxbits)
|| (decomp && db->lens == NULL))
{
return 0;
}
if (decomp)
{
indx = LAST;
do
{
db->lens[indx] = 1;
}
while (indx-- > 0);
}
indx = db->hsize;
while (indx-- != 0)
{
db->dict[indx].codem1 = BADCODEM1;
db->dict[indx].cptr = 0;
}
db->unit = unit;
db->mru = 0;
#ifndef DEBUG
if (debug)
#endif
db->debug = 1;
bsd_reset(db);
return 1;
}
static int bsd_comp_init (void *state, unsigned char *options,
int opt_len, int unit, int opthdr, int debug)
{
return bsd_init (state, options, opt_len, unit, debug, 0);
}
static int bsd_decomp_init (void *state, unsigned char *options,
int opt_len, int unit, int opthdr, int mru,
int debug)
{
return bsd_init (state, options, opt_len, unit, debug, 1);
}
/*
* Obtain pointers to the various structures in the compression tables
*/
#define dict_ptrx(p,idx) &(p->dict[idx])
#define lens_ptrx(p,idx) &(p->lens[idx])
#ifdef DEBUG
static unsigned short *lens_ptr(struct bsd_db *db, int idx)
{
if ((unsigned int) idx > (unsigned int) db->maxmaxcode)
{
printk ("<9>ppp: lens_ptr(%d) > max\n", idx);
idx = 0;
}
return lens_ptrx (db, idx);
}
static struct bsd_dict *dict_ptr(struct bsd_db *db, int idx)
{
if ((unsigned int) idx >= (unsigned int) db->hsize)
{
printk ("<9>ppp: dict_ptr(%d) > max\n", idx);
idx = 0;
}
return dict_ptrx (db, idx);
}
#else
#define lens_ptr(db,idx) lens_ptrx(db,idx)
#define dict_ptr(db,idx) dict_ptrx(db,idx)
#endif
/*
* compress a packet
*
* The result of this function is the size of the compressed
* packet. A zero is returned if the packet was not compressed
* for some reason, such as the size being larger than uncompressed.
*
* One change from the BSD compress command is that when the
* code size expands, we do not output a bunch of padding.
*/
static int bsd_compress (void *state, unsigned char *rptr, unsigned char *obuf,
int isize, int osize)
{
struct bsd_db *db;
int hshift;
unsigned int max_ent;
unsigned int n_bits;
unsigned int bitno;
unsigned long accm;
int ent;
unsigned long fcode;
struct bsd_dict *dictp;
unsigned char c;
int hval;
int disp;
int ilen;
int mxcode;
unsigned char *wptr;
int olen;
#define PUTBYTE(v) \
{ \
++olen; \
if (wptr) \
{ \
*wptr++ = (unsigned char) (v); \
if (olen >= osize) \
{ \
wptr = NULL; \
} \
} \
}
#define OUTPUT(ent) \
{ \
bitno -= n_bits; \
accm |= ((ent) << bitno); \
do \
{ \
PUTBYTE(accm >> 24); \
accm <<= 8; \
bitno += 8; \
} \
while (bitno <= 24); \
}
/*
* If the protocol is not in the range we're interested in,
* just return without compressing the packet. If it is,
* the protocol becomes the first byte to compress.
*/
ent = PPP_PROTOCOL(rptr);
if (ent < 0x21 || ent > 0xf9)
{
return 0;
}
db = (struct bsd_db *) state;
hshift = db->hshift;
max_ent = db->max_ent;
n_bits = db->n_bits;
bitno = 32;
accm = 0;
mxcode = MAXCODE (n_bits);
/* Initialize the output pointers */
wptr = obuf;
olen = PPP_HDRLEN + BSD_OVHD;
if (osize > isize)
{
osize = isize;
}
/* This is the PPP header information */
if (wptr)
{
*wptr++ = PPP_ADDRESS(rptr);
*wptr++ = PPP_CONTROL(rptr);
*wptr++ = 0;
*wptr++ = PPP_COMP;
*wptr++ = db->seqno >> 8;
*wptr++ = db->seqno;
}
/* Skip the input header */
rptr += PPP_HDRLEN;
isize -= PPP_HDRLEN;
ilen = ++isize; /* Low byte of protocol is counted as input */
while (--ilen > 0)
{
c = *rptr++;
fcode = BSD_KEY (ent, c);
hval = BSD_HASH (ent, c, hshift);
dictp = dict_ptr (db, hval);
/* Validate and then check the entry. */
if (dictp->codem1 >= max_ent)
{
goto nomatch;
}
if (dictp->f.fcode == fcode)
{
ent = dictp->codem1 + 1;
continue; /* found (prefix,suffix) */
}
/* continue probing until a match or invalid entry */
disp = (hval == 0) ? 1 : hval;
do
{
hval += disp;
if (hval >= db->hsize)
{
hval -= db->hsize;
}
dictp = dict_ptr (db, hval);
if (dictp->codem1 >= max_ent)
{
goto nomatch;
}
}
while (dictp->f.fcode != fcode);
ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
continue;
nomatch:
OUTPUT(ent); /* output the prefix */
/* code -> hashtable */
if (max_ent < db->maxmaxcode)
{
struct bsd_dict *dictp2;
struct bsd_dict *dictp3;
int indx;
/* expand code size if needed */
if (max_ent >= mxcode)
{
db->n_bits = ++n_bits;
mxcode = MAXCODE (n_bits);
}
/* Invalidate old hash table entry using
* this code, and then take it over.
*/
dictp2 = dict_ptr (db, max_ent + 1);
indx = dictp2->cptr;
dictp3 = dict_ptr (db, indx);
if (dictp3->codem1 == max_ent)
{
dictp3->codem1 = BADCODEM1;
}
dictp2->cptr = hval;
dictp->codem1 = max_ent;
dictp->f.fcode = fcode;
db->max_ent = ++max_ent;
if (db->lens)
{
unsigned short *len1 = lens_ptr (db, max_ent);
unsigned short *len2 = lens_ptr (db, ent);
*len1 = *len2 + 1;
}
}
ent = c;
}
OUTPUT(ent); /* output the last code */
db->bytes_out += olen - PPP_HDRLEN - BSD_OVHD;
db->uncomp_bytes += isize;
db->in_count += isize;
++db->uncomp_count;
++db->seqno;
if (bitno < 32)
{
++db->bytes_out; /* must be set before calling bsd_check */
}
/*
* Generate the clear command if needed
*/
if (bsd_check(db))
{
OUTPUT (CLEAR);
}
/*
* Pad dribble bits of last code with ones.
* Do not emit a completely useless byte of ones.
*/
if (bitno != 32)
{
PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
}
/*
* Increase code size if we would have without the packet
* boundary because the decompressor will do so.
*/
if (max_ent >= mxcode && max_ent < db->maxmaxcode)
{
db->n_bits++;
}
/* If output length is too large then this is an incomplete frame. */
if (wptr == NULL)
{
++db->incomp_count;
db->incomp_bytes += isize;
olen = 0;
}
else /* Count the number of compressed frames */
{
++db->comp_count;
db->comp_bytes += olen;
}
/* Return the resulting output length */
return olen;
#undef OUTPUT
#undef PUTBYTE
}
/*
* Update the "BSD Compress" dictionary on the receiver for
* incompressible data by pretending to compress the incoming data.
*/
static void bsd_incomp (void *state, unsigned char *ibuf, int icnt)
{
(void) bsd_compress (state, ibuf, (char *) 0, icnt, 0);
}
/*
* Decompress "BSD Compress".
*
* Because of patent problems, we return DECOMP_ERROR for errors
* found by inspecting the input data and for system problems, but
* DECOMP_FATALERROR for any errors which could possibly be said to
* be being detected "after" decompression. For DECOMP_ERROR,
* we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
* infringing a patent of Motorola's if we do, so we take CCP down
* instead.
*
* Given that the frame has the correct sequence number and a good FCS,
* errors such as invalid codes in the input most likely indicate a
* bug, so we return DECOMP_FATALERROR for them in order to turn off
* compression, even though they are detected by inspecting the input.
*/
static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
unsigned char *obuf, int osize)
{
struct bsd_db *db;
unsigned int max_ent;
unsigned long accm;
unsigned int bitno; /* 1st valid bit in accm */
unsigned int n_bits;
unsigned int tgtbitno; /* bitno when we have a code */
struct bsd_dict *dictp;
int explen;
int seq;
unsigned int incode;
unsigned int oldcode;
unsigned int finchar;
unsigned char *p;
unsigned char *wptr;
int adrs;
int ctrl;
int ilen;
int codelen;
int extra;
db = (struct bsd_db *) state;
max_ent = db->max_ent;
accm = 0;
bitno = 32; /* 1st valid bit in accm */
n_bits = db->n_bits;
tgtbitno = 32 - n_bits; /* bitno when we have a code */
/*
* Save the address/control from the PPP header
* and then get the sequence number.
*/
adrs = PPP_ADDRESS (ibuf);
ctrl = PPP_CONTROL (ibuf);
seq = (ibuf[4] << 8) + ibuf[5];
ibuf += (PPP_HDRLEN + 2);
ilen = isize - (PPP_HDRLEN + 2);
/*
* Check the sequence number and give up if it differs from
* the value we're expecting.
*/
if (seq != db->seqno)
{
if (db->debug)
{
printk("bsd_decomp%d: bad sequence # %d, expected %d\n",
db->unit, seq, db->seqno - 1);
}
return DECOMP_ERROR;
}
++db->seqno;
db->bytes_out += ilen;
/*
* Fill in the ppp header, but not the last byte of the protocol
* (that comes from the decompressed data).
*/
wptr = obuf;
*wptr++ = adrs;
*wptr++ = ctrl;
*wptr++ = 0;
oldcode = CLEAR;
explen = 3;
/*
* Keep the checkpoint correctly so that incompressible packets
* clear the dictionary at the proper times.
*/
for (;;)
{
if (ilen-- <= 0)
{
db->in_count += (explen - 3); /* don't count the header */
break;
}
/*
* Accumulate bytes until we have a complete code.
* Then get the next code, relying on the 32-bit,
* unsigned accm to mask the result.
*/
bitno -= 8;
accm |= *ibuf++ << bitno;
if (tgtbitno < bitno)
{
continue;
}
incode = accm >> tgtbitno;
accm <<= n_bits;
bitno += n_bits;
/*
* The dictionary must only be cleared at the end of a packet.
*/
if (incode == CLEAR)
{
if (ilen > 0)
{
if (db->debug)
{
printk("bsd_decomp%d: bad CLEAR\n", db->unit);
}
return DECOMP_FATALERROR; /* probably a bug */
}
bsd_clear(db);
break;
}
if ((incode > max_ent + 2) || (incode > db->maxmaxcode)
|| (incode > max_ent && oldcode == CLEAR))
{
if (db->debug)
{
printk("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
db->unit, incode, oldcode);
printk("max_ent=0x%x explen=%d seqno=%d\n",
max_ent, explen, db->seqno);
}
return DECOMP_FATALERROR; /* probably a bug */
}
/* Special case for KwKwK string. */
if (incode > max_ent)
{
finchar = oldcode;
extra = 1;
}
else
{
finchar = incode;
extra = 0;
}
codelen = *(lens_ptr (db, finchar));
explen += codelen + extra;
if (explen > osize)
{
if (db->debug)
{
printk("bsd_decomp%d: ran out of mru\n", db->unit);
#ifdef DEBUG
printk(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
ilen, finchar, codelen, explen);
#endif
}
return DECOMP_FATALERROR;
}
/*
* Decode this code and install it in the decompressed buffer.
*/
wptr += codelen;
p = wptr;
while (finchar > LAST)
{
struct bsd_dict *dictp2 = dict_ptr (db, finchar);
dictp = dict_ptr (db, dictp2->cptr);
#ifdef DEBUG
if (--codelen <= 0 || dictp->codem1 != finchar-1)
{
if (codelen <= 0)
{
printk("bsd_decomp%d: fell off end of chain ", db->unit);
printk("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
incode, finchar, dictp2->cptr, max_ent);
}
else
{
if (dictp->codem1 != finchar-1)
{
printk("bsd_decomp%d: bad code chain 0x%x "
"finchar=0x%x ",
db->unit, incode, finchar);
printk("oldcode=0x%x cptr=0x%x codem1=0x%x\n",
oldcode, dictp2->cptr, dictp->codem1);
}
}
return DECOMP_FATALERROR;
}
#endif
*--p = dictp->f.hs.suffix;
finchar = dictp->f.hs.prefix;
}
*--p = finchar;
#ifdef DEBUG
if (--codelen != 0)
{
printk("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
db->unit, codelen, incode, max_ent);
}
#endif
if (extra) /* the KwKwK case again */
{
*wptr++ = finchar;
}
/*
* If not first code in a packet, and
* if not out of code space, then allocate a new code.
*
* Keep the hash table correct so it can be used
* with uncompressed packets.
*/
if (oldcode != CLEAR && max_ent < db->maxmaxcode)
{
struct bsd_dict *dictp2, *dictp3;
unsigned short *lens1, *lens2;
unsigned long fcode;
int hval, disp, indx;
fcode = BSD_KEY(oldcode,finchar);
hval = BSD_HASH(oldcode,finchar,db->hshift);
dictp = dict_ptr (db, hval);
/* look for a free hash table entry */
if (dictp->codem1 < max_ent)
{
disp = (hval == 0) ? 1 : hval;
do
{
hval += disp;
if (hval >= db->hsize)
{
hval -= db->hsize;
}
dictp = dict_ptr (db, hval);
}
while (dictp->codem1 < max_ent);
}
/*
* Invalidate previous hash table entry
* assigned this code, and then take it over
*/
dictp2 = dict_ptr (db, max_ent + 1);
indx = dictp2->cptr;
dictp3 = dict_ptr (db, indx);
if (dictp3->codem1 == max_ent)
{
dictp3->codem1 = BADCODEM1;
}
dictp2->cptr = hval;
dictp->codem1 = max_ent;
dictp->f.fcode = fcode;
db->max_ent = ++max_ent;
/* Update the length of this string. */
lens1 = lens_ptr (db, max_ent);
lens2 = lens_ptr (db, oldcode);
*lens1 = *lens2 + 1;
/* Expand code size if needed. */
if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
{
db->n_bits = ++n_bits;
tgtbitno = 32-n_bits;
}
}
oldcode = incode;
}
++db->comp_count;
++db->uncomp_count;
db->comp_bytes += isize - BSD_OVHD - PPP_HDRLEN;
db->uncomp_bytes += explen;
if (bsd_check(db))
{
if (db->debug)
{
printk("bsd_decomp%d: peer should have cleared dictionary on %d\n",
db->unit, db->seqno - 1);
}
}
return explen;
}
/*************************************************************
* Table of addresses for the BSD compression module
*************************************************************/
static struct compressor ppp_bsd_compress = {
.compress_proto = CI_BSD_COMPRESS,
.comp_alloc = bsd_comp_alloc,
.comp_free = bsd_free,
.comp_init = bsd_comp_init,
.comp_reset = bsd_reset,
.compress = bsd_compress,
.comp_stat = bsd_comp_stats,
.decomp_alloc = bsd_decomp_alloc,
.decomp_free = bsd_free,
.decomp_init = bsd_decomp_init,
.decomp_reset = bsd_reset,
.decompress = bsd_decompress,
.incomp = bsd_incomp,
.decomp_stat = bsd_comp_stats,
.owner = THIS_MODULE
};
/*************************************************************
* Module support routines
*************************************************************/
static int __init bsdcomp_init(void)
{
int answer = ppp_register_compressor(&ppp_bsd_compress);
if (answer == 0)
printk(KERN_INFO "PPP BSD Compression module registered\n");
return answer;
}
static void __exit bsdcomp_cleanup(void)
{
ppp_unregister_compressor(&ppp_bsd_compress);
}
module_init(bsdcomp_init);
module_exit(bsdcomp_cleanup);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("ppp-compress-" __stringify(CI_BSD_COMPRESS));