Initial import

1 files changed, 1170 insertions, 0 deletions

diff --git a/drivers/net/ppp/bsd_comp.c b/drivers/net/ppp/bsd_comp.c
new file mode 100644
index 000000000..a9b759add
--- /dev/null
+++ b/drivers/net/ppp/bsd_comp.c
@@ -0,0 +1,1170 @@
+/*
+ * 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(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((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;
+  }
+
+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));