isdn_bsdcomp.c
/*
* BSD compression module
*
* Patched version for ISDN syncPPP written 1997/1998 by Michael Hipp
* The whole module is now SKB based.
*
* Compile with:
* gcc -O2 -I/usr/src/linux/include -D__KERNEL__ -DMODULE -c isdn_bsdcomp.c
*/
/*
* Original copyright notice:
*
* 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.
*/
#ifndef MODULE
#error This file must be compiled as a module.
#endif
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/interrupt.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/in.h>
#include <linux/malloc.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/sched.h> /* to get the struct task_struct */
#include <linux/string.h> /* used in new tty drivers */
#include <linux/signal.h> /* used in new tty drivers */
#include <asm/system.h>
#include <asm/bitops.h>
#include <asm/segment.h>
#include <asm/byteorder.h>
#include <asm/types.h>
#include <linux/if.h>
#include <linux/if_ether.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/inet.h>
#include <linux/ioctl.h>
#include <linux/ppp_defs.h>
#include <linux/isdn.h>
#include <linux/isdn_ppp.h>
/* #include <linux/netprotocol.h> */
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/if_arp.h>
#include <linux/ppp-comp.h>
#include "isdn_ppp.h"
#define BSD_VERSION(x) ((x) >> 5)
#define BSD_NBITS(x) ((x) & 0x1F)
#define BSD_CURRENT_VERSION 1
#define DEBUG 1
/*
* A dictionary for doing BSD compress.
*/
struct bsd_dict {
u32 fcode;
u16 codem1; /* output of hash table -1 */
u16 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 */
u16 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 */
int xmit;
};
#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
/*
* 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->incomp_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_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 = (struct bsd_db *) state;
if (db) {
/*
* Release the dictionary
*/
if (db->dict) {
vfree (db->dict);
db->dict = NULL;
}
/*
* Release the string buffer
*/
if (db->lens) {
vfree (db->lens);
db->lens = NULL;
}
/*
* Finally release the structure itself.
*/
kfree (db);
MOD_DEC_USE_COUNT;
}
}
/*
* Allocate space for a (de) compressor.
*/
static void *bsd_alloc (struct isdn_ppp_comp_data *data)
{
int bits;
unsigned int hsize, hshift, maxmaxcode;
struct bsd_db *db;
int decomp;
static unsigned int htab[][2] = {
{ 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } , { 5003 , 4 } ,
{ 9001 , 5 } , { 18013 , 6 } , { 35023 , 7 } , { 69001 , 8 }
};
if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
|| BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
return NULL;
bits = BSD_NBITS(data->options[0]);
if(bits < 9 || bits > 15)
return NULL;
hsize = htab[bits-9][0];
hshift = htab[bits-9][1];
/*
* Allocate the main control structure for this instance.
*/
maxmaxcode = MAXCODE(bits);
db = (struct bsd_db *) kmalloc (sizeof (struct bsd_db),GFP_KERNEL);
if (!db)
return NULL;
memset (db, 0, sizeof(struct bsd_db));
db->xmit = data->flags & IPPP_COMP_FLAG_XMIT;
decomp = db->xmit ? 0 : 1;
/*
* Allocate space for the dictionary. This may be more than one page in
* length.
*/
db->dict = (struct bsd_dict *) vmalloc (hsize * sizeof (struct bsd_dict));
if (!db->dict) {
bsd_free (db);
return NULL;
}
MOD_INC_USE_COUNT;
/*
* If this is the compression buffer then there is no length data.
* For decompression, the length information is needed as well.
*/
if (!decomp)
db->lens = NULL;
else {
db->lens = (unsigned short *) vmalloc ((maxmaxcode + 1) *
sizeof (db->lens[0]));
if (!db->lens) {
bsd_free (db); /* calls MOD_DEC_USE_COUNT; */
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;
}
/*
* Initialize the database.
*/
static int bsd_init (void *state, struct isdn_ppp_comp_data *data, int unit, int debug)
{
struct bsd_db *db = state;
int indx;
int decomp;
if(!state || !data) {
printk(KERN_ERR "isdn_bsd_init: [%d] ERR, state %lx data %lx\n",unit,(long)state,(long)data);
return 0;
}
decomp = db->xmit ? 0 : 1;
if (data->optlen != 1 || data->num != CI_BSD_COMPRESS
|| (BSD_VERSION(data->options[0]) != BSD_CURRENT_VERSION)
|| (BSD_NBITS(data->options[0]) != db->maxbits)
|| (decomp && db->lens == NULL)) {
printk(KERN_ERR "isdn_bsd: %d %d %d %d %lx\n",data->optlen,data->num,data->options[0],decomp,(unsigned long)db->lens);
return 0;
}
if (decomp)
for(indx=LAST;indx>=0;indx--)
db->lens[indx] = 1;
indx = db->hsize;
while (indx-- != 0) {
db->dict[indx].codem1 = BADCODEM1;
db->dict[indx].cptr = 0;
}
db->unit = unit;
db->mru = 0;
db->debug = 1;
bsd_reset(db);
return 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 (KERN_DEBUG "<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 (KERN_DEBUG "<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
*/
static int bsd_compress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out,int proto)
{
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,disp,ilen,mxcode;
unsigned char *rptr = skb_in->data;
int isize = skb_in->len;
#define OUTPUT(ent) \
{ \
bitno -= n_bits; \
accm |= ((ent) << bitno); \
do { \
if(skb_out && skb_tailroom(skb_out) > 0) \
*(skb_put(skb_out,1)) = (unsigned char) (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.
*/
printk(KERN_DEBUG "bsd_compress called with %x\n",proto);
ent = proto;
if (proto < 0x21 || proto > 0xf9 || !(proto & 0x1) )
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);
/* This is the PPP header information */
if(skb_out && skb_tailroom(skb_out) >= 2) {
char *v = skb_put(skb_out,2);
/* we only push our own data on the header,
AC,PC and protos is pushed by caller */
v[0] = db->seqno >> 8;
v[1] = db->seqno;
}
ilen = ++isize; /* This is off by one, but that is what is in draft! */
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->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->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->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 */
if(skb_out)
db->bytes_out += skb_out->len; /* Do not count bytes from here */
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 && skb_out && skb_tailroom(skb_out) > 0)
*(skb_put(skb_out,1)) = (unsigned char) ((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 incompressible frame. */
if (!skb_out || (skb_out && skb_out->len >= skb_in->len) ) {
++db->incomp_count;
db->incomp_bytes += isize;
return 0;
}
/* Count the number of compressed frames */
++db->comp_count;
db->comp_bytes += skb_out->len;
return skb_out->len;
#undef OUTPUT
}
/*
* Update the "BSD Compress" dictionary on the receiver for
* incompressible data by pretending to compress the incoming data.
*/
static void bsd_incomp (void *state, struct sk_buff *skb_in,int proto)
{
bsd_compress (state, skb_in, NULL, proto);
}
/*
* Decompress "BSD Compress".
*/
static int bsd_decompress (void *state, struct sk_buff *skb_in, struct sk_buff *skb_out)
{
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 seq;
unsigned int incode;
unsigned int oldcode;
unsigned int finchar;
unsigned char *p,*ibuf;
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 */
printk(KERN_DEBUG "bsd_decompress called\n");
if(!skb_in || !skb_out) {
printk(KERN_ERR "bsd_decompress called with NULL parameter\n");
return DECOMP_ERROR;
}
/*
* Get the sequence number.
*/
if( (p = skb_pull(skb_in,2)) == NULL) {
return DECOMP_ERROR;
}
p-=2;
seq = (p[0] << 8) + p[1];
ilen = skb_in->len;
ibuf = skb_in->data;
/*
* Check the sequence number and give up if it differs from
* the value we're expecting.
*/
if (seq != db->seqno) {
if (db->debug) {
printk(KERN_DEBUG "bsd_decomp%d: bad sequence # %d, expected %d\n",
db->unit, seq, db->seqno - 1);
}
return DECOMP_ERROR;
}
++db->seqno;
db->bytes_out += ilen;
if(skb_tailroom(skb_out) > 0)
*(skb_put(skb_out,1)) = 0;
else
return DECOMP_ERR_NOMEM;
oldcode = CLEAR;
/*
* Keep the checkpoint correctly so that incompressible packets
* clear the dictionary at the proper times.
*/
for (;;) {
if (ilen-- <= 0) {
db->in_count += (skb_out->len - 1); /* 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(KERN_DEBUG "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(KERN_DEBUG "bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
db->unit, incode, oldcode);
printk(KERN_DEBUG "max_ent=0x%x skb->Len=%d seqno=%d\n",
max_ent, skb_out->len, 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));
if( skb_tailroom(skb_out) < codelen + extra) {
if (db->debug) {
printk(KERN_DEBUG "bsd_decomp%d: ran out of mru\n", db->unit);
#ifdef DEBUG
printk(KERN_DEBUG " len=%d, finchar=0x%x, codelen=%d,skblen=%d\n",
ilen, finchar, codelen, skb_out->len);
#endif
}
return DECOMP_FATALERROR;
}
/*
* Decode this code and install it in the decompressed buffer.
*/
p = skb_put(skb_out,codelen);
p += codelen;
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(KERN_ERR "bsd_decomp%d: fell off end of chain ", db->unit);
printk(KERN_ERR "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(KERN_ERR "bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",db->unit, incode, finchar);
printk(KERN_ERR "oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode, dictp2->cptr, dictp->codem1);
}
}
return DECOMP_FATALERROR;
}
#endif
{
u32 fcode = dictp->fcode;
*--p = (fcode >> 16) & 0xff;
finchar = fcode & 0xffff;
}
}
*--p = finchar;
#ifdef DEBUG
if (--codelen != 0)
printk(KERN_ERR "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 */
*(skb_put(skb_out,1)) = 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;
u16 *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->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 += skb_in->len - BSD_OVHD;
db->uncomp_bytes += skb_out->len;
if (bsd_check(db)) {
if (db->debug)
printk(KERN_DEBUG "bsd_decomp%d: peer should have cleared dictionary on %d\n",
db->unit, db->seqno - 1);
}
return skb_out->len;
}
/*************************************************************
* Table of addresses for the BSD compression module
*************************************************************/
static struct isdn_ppp_compressor ippp_bsd_compress = {
NULL,NULL, /* prev,next: overwritten by isdn_ppp */
CI_BSD_COMPRESS, /* compress_proto */
bsd_alloc, /* alloc */
bsd_free, /* free */
bsd_init, /* init */
bsd_reset, /* reset */
bsd_compress, /* compress */
bsd_decompress, /* decompress */
bsd_incomp, /* incomp */
bsd_stats /* comp_stat */
};
/*************************************************************
* Module support routines
*************************************************************/
int init_module(void)
{
int answer = isdn_ppp_register_compressor (&ippp_bsd_compress);
if (answer == 0)
printk (KERN_INFO "PPP BSD Compression module registered\n");
return answer;
}
void cleanup_module(void)
{
isdn_ppp_unregister_compressor (&ippp_bsd_compress);
}
