isdn_bsdcomp.c

linux-2.6.15.6

/*
 * BSD compression module
 *
 * Patched version for ISDN syncPPP written 1997/1998 by Michael Hipp
 * The whole module is now SKB based.
 *
 */

/*
 * 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..
 */

/*
 * 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.
 */

#include <linux/module.h>
#include <linux/init.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/slab.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/string.h>	/* used in new tty drivers */
#include <linux/signal.h>	/* used in new tty drivers */
#include <linux/bitops.h>

#include <asm/system.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/vmalloc.h>

#include <linux/ppp_defs.h>

#include <linux/isdn.h>
#include <linux/isdn_ppp.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/if_arp.h>
#include <linux/ppp-comp.h>

#include "isdn_ppp.h"

MODULE_DESCRIPTION("ISDN4Linux: BSD Compression for PPP over ISDN");
MODULE_LICENSE("Dual BSD/GPL");

#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,unsigned char code, unsigned char id,
			unsigned char *data, unsigned len,
			struct isdn_ppp_resetparams *rsparm)
{
	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
		 */
		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 (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;
	}

	/*
	 * 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);
			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,0,0,NULL,0,NULL);
    
	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;