patch-2.3.4 linux/drivers/isdn/isdn_bsdcomp.c

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diff -u --recursive --new-file v2.3.3/linux/drivers/isdn/isdn_bsdcomp.c linux/drivers/isdn/isdn_bsdcomp.c
@@ -0,0 +1,934 @@
+/*
+ * 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,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
+		 */
+		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,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;
+	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 isdn_ppp_resetparams *rsparm)
+{
+	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);
+}

FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)