Add realtek target files

Signed-off-by: Roman Yeryomin <roman@advem.lv>

1 files changed, 1405 insertions, 0 deletions

diff --git a/target/linux/realtek/files/drivers/net/ppp_mppe_mppc.c b/target/linux/realtek/files/drivers/net/ppp_mppe_mppc.c
new file mode 100644
index 000000000..52f722587
--- /dev/null
+++ b/target/linux/realtek/files/drivers/net/ppp_mppe_mppc.c
@@ -0,0 +1,1405 @@
+/*
+ * ppp_mppe_mppc.c - MPPC/MPPE "compressor/decompressor" module.
+ *
+ * Copyright (c) 1994 ÁpáMagosái <mag@bunuel.tii.matav.hu>
+ * Copyright (c) 1999 Tim Hockin, Cobalt Networks Inc. <thockin@cobaltnet.com>
+ * Copyright (c) 2002-2004 Jan Dubiec <jdx@slackware.pl>
+ * 
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation is hereby granted, provided that the above copyright
+ * notice appears in all copies. This software is provided without any
+ * warranty, express or implied.
+ *
+ * The code is based on MPPE kernel module written by ÁpáMagosái and
+ * Tim Hockin which can be found on http://planetmirror.com/pub/mppe/.
+ * I have added MPPC and 56 bit session keys support in MPPE.
+ *
+ * WARNING! Although this is open source code, its usage in some countries
+ * (in particular in the USA) may violate Stac Inc. patent for MPPC.
+ *
+ *  ==FILEVERSION 20040815==
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <asm/scatterlist.h>
+#include <linux/vmalloc.h>
+#include <linux/crypto.h>
+
+#include <linux/ppp_defs.h>
+#include <linux/ppp-comp.h>
+
+/*
+ * SHA1 definitions and prototypes
+ */
+typedef struct {
+    u32 state[5];
+    u32 count[2];
+    u8 buffer[64];
+} SHA1_CTX;
+
+#define SHA1_SIGNATURE_SIZE 20
+
+static void SHA1_Init(SHA1_CTX *);
+static void SHA1_Update(SHA1_CTX *, const u8 *, u32);
+static void SHA1_Final(u8[SHA1_SIGNATURE_SIZE], SHA1_CTX *);
+
+/*
+ * State for a mppc/mppe "(de)compressor".
+ */
+struct ppp_mppe_state {
+    struct crypto_tfm *arc4_tfm;
+    u8		master_key[MPPE_MAX_KEY_LEN];
+    u8		session_key[MPPE_MAX_KEY_LEN];
+    u8		mppc;		/* do we use compression (MPPC)? */
+    u8		mppe;		/* do we use encryption (MPPE)? */
+    u8		keylen;		/* key length in bytes */
+    u8		bitkeylen;	/* key length in bits */
+    u16		ccount;		/* coherency counter */
+    u16		bits;		/* MPPC/MPPE control bits */
+    u8		stateless;	/* do we use stateless mode? */
+    u8		nextflushed;	/* set A bit in the next outgoing packet;
+				   used only by compressor*/
+    u8		flushexpected;	/* drop packets until A bit is received;
+				   used only by decompressor*/
+    u8		*hist;		/* MPPC history */
+    u16		*hash;		/* Hash table; used only by compressor */
+    u16		histptr;	/* history "cursor" */
+    int		unit;
+    int		debug;
+    int		mru;
+    struct compstat stats;
+};
+
+#define MPPE_HIST_LEN		8192	/* MPPC history size */
+#define MPPE_MAX_CCOUNT		0x0FFF	/* max. coherency counter value */
+
+#define MPPE_BIT_FLUSHED	0x80	/* bit A */
+#define MPPE_BIT_RESET		0x40	/* bit B */
+#define MPPE_BIT_COMP		0x20	/* bit C */
+#define MPPE_BIT_ENCRYPTED	0x10	/* bit D */
+
+#define MPPE_SALT0		0xD1	/* values used in MPPE key derivation */
+#define MPPE_SALT1		0x26	/* according to RFC3079 */
+#define MPPE_SALT2		0x9E
+
+#define MPPE_CCOUNT(x)		((((x)[4] & 0x0f) << 8) + (x)[5])
+#define MPPE_BITS(x)		((x)[4] & 0xf0)
+#define MPPE_CTRLHI(x)		((((x)->ccount & 0xf00)>>8)|((x)->bits))
+#define MPPE_CTRLLO(x)		((x)->ccount & 0xff)
+
+static inline void
+setup_sg(struct scatterlist *sg, const void  *address, unsigned int length)
+{
+    sg[0].page_link = virt_to_page(address);
+    sg[0].offset = offset_in_page(address);
+    sg[0].length = length;
+}
+
+static inline void
+arc4_setkey(struct ppp_mppe_state *state, const unsigned char *key,
+	    const unsigned int keylen)
+{
+    crypto_cipher_setkey(state->arc4_tfm, key, keylen);
+}
+
+static inline void
+arc4_encrypt(struct ppp_mppe_state *state, const unsigned char *in,
+	     const unsigned int len, unsigned char *out)
+{
+    int i;
+    for (i = 0; i < len; i++)
+    {
+       crypto_cipher_encrypt_one(state->arc4_tfm, out+i, in+i);
+    }
+}
+
+#define arc4_decrypt arc4_encrypt
+
+/*
+ * Key Derivation, from RFC 3078, RFC 3079.
+ * Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
+ */
+static void
+GetNewKeyFromSHA(struct ppp_mppe_state *state, unsigned char *MasterKey,
+		 unsigned char *SessionKey, unsigned long SessionKeyLength,
+		 unsigned char *InterimKey)
+{
+    /*Pads used in key derivation */
+    static const unsigned char  SHAPad1[40] = {
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+    };
+
+    static const unsigned char  SHAPad2[40] = {
+	0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+	0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+	0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+	0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2
+    };
+
+    unsigned char Digest[SHA1_SIGNATURE_SIZE];
+    SHA1_CTX Context;
+
+    SHA1_Init(&Context);
+    SHA1_Update(&Context, MasterKey, SessionKeyLength);
+    SHA1_Update(&Context, SHAPad1, sizeof(SHAPad1));
+    SHA1_Update(&Context, SessionKey, SessionKeyLength);
+    SHA1_Update(&Context, SHAPad2, sizeof(SHAPad2));
+    SHA1_Final(Digest, &Context);
+
+    memcpy(InterimKey, Digest, SessionKeyLength);
+}
+
+static void
+mppe_change_key(struct ppp_mppe_state *state, int initialize)
+{
+    unsigned char InterimKey[MPPE_MAX_KEY_LEN];
+
+    GetNewKeyFromSHA(state, state->master_key, state->session_key,
+		     state->keylen, InterimKey);
+    if (initialize) {
+	memcpy(state->session_key, InterimKey, state->keylen);
+    } else {
+	arc4_setkey(state, InterimKey, state->keylen);
+	arc4_encrypt(state, InterimKey, state->keylen, state->session_key);
+    }
+    if (state->keylen == 8) {
+	if (state->bitkeylen == 40) {
+	    state->session_key[0] = MPPE_SALT0;
+	    state->session_key[1] = MPPE_SALT1;
+	    state->session_key[2] = MPPE_SALT2;
+	} else {
+	    state->session_key[0] = MPPE_SALT0;
+	}
+    }
+    arc4_setkey(state, state->session_key, state->keylen);
+}
+
+/* increase 12-bit coherency counter */
+static inline void
+mppe_increase_ccount(struct ppp_mppe_state *state)
+{
+    state->ccount = (state->ccount + 1) & MPPE_MAX_CCOUNT;
+    if (state->mppe) {
+	if (state->stateless) {
+	    mppe_change_key(state, 0);
+	    state->nextflushed = 1;
+	} else {
+	    if ((state->ccount & 0xff) == 0xff) {
+		mppe_change_key(state, 0);
+	    }
+	}
+    }
+}
+
+/* allocate space for a MPPE/MPPC (de)compressor.  */
+/*   comp != 0 -> init compressor */
+/*   comp = 0 -> init decompressor */
+static void *
+mppe_alloc(unsigned char *options, int opt_len, int comp)
+{
+    struct ppp_mppe_state *state;
+    u8* fname;
+
+    fname = comp ? "mppe_comp_alloc" : "mppe_decomp_alloc";
+
+    /*  
+ 	* Hack warning - additionally to the standard MPPC/MPPE configuration
+	* options, pppd passes to the (de)copressor 8 or 16 byte session key.
+ 	* Therefore options[1] contains MPPC/MPPE configuration option length
+ 	* (CILEN_MPPE = 6), but the real options length, depending on the key
+	* length, is 6+8 or 6+16.
+ 	*/
+    if (opt_len < CILEN_MPPE) {
+	printk(KERN_WARNING "%s: wrong options length: %u\n", fname, opt_len);
+	return NULL;
+    }
+
+    if (options[0] != CI_MPPE || options[1] != CILEN_MPPE ||
+	(options[2] & ~MPPE_STATELESS) != 0 ||
+	options[3] != 0 || options[4] != 0 ||
+	(options[5] & ~(MPPE_128BIT|MPPE_56BIT|MPPE_40BIT|MPPE_MPPC)) != 0 ||
+	(options[5] & (MPPE_128BIT|MPPE_56BIT|MPPE_40BIT|MPPE_MPPC)) == 0) {
+	printk(KERN_WARNING "%s: options rejected: o[0]=%02x, o[1]=%02x, "
+	       "o[2]=%02x, o[3]=%02x, o[4]=%02x, o[5]=%02x\n", fname, options[0],
+	       options[1], options[2], options[3], options[4], options[5]);
+	return NULL;
+    }
+
+    state = (struct ppp_mppe_state *)kmalloc(sizeof(*state), GFP_KERNEL);
+    if (state == NULL) {
+	printk(KERN_ERR "%s: cannot allocate space for %scompressor\n", fname,
+	       comp ? "" : "de");
+	return NULL;
+    }
+    memset(state, 0, sizeof(struct ppp_mppe_state));
+
+    state->mppc = options[5] & MPPE_MPPC;	/* Do we use MPPC? */
+    state->mppe = options[5] & (MPPE_128BIT | MPPE_56BIT |
+	MPPE_40BIT);				/* Do we use MPPE? */
+
+    if (state->mppc) {
+	/* allocate MPPC history */
+	state->hist = (u8*)vmalloc(2*MPPE_HIST_LEN*sizeof(u8));
+	if (state->hist == NULL) {
+	    kfree(state);
+	    printk(KERN_ERR "%s: cannot allocate space for MPPC history\n",
+		   fname);
+	    return NULL;
+	}
+
+	/* allocate hashtable for MPPC compressor */
+	if (comp) {
+	    state->hash = (u16*)vmalloc(MPPE_HIST_LEN*sizeof(u16));
+	    if (state->hash == NULL) {
+		vfree(state->hist);
+		kfree(state);
+		printk(KERN_ERR "%s: cannot allocate space for MPPC history\n",
+		       fname);
+		return NULL;
+	    }
+	}
+    }
+
+    if (state->mppe) { /* specific for MPPE */
+	/* Load ARC4 algorithm */
+	state->arc4_tfm = crypto_alloc_base("arc4", 0, 0);
+	if (state->arc4_tfm == NULL) {
+	    vfree(state->hash);
+	    vfree(state->hist);
+	    kfree(state);
+	    printk(KERN_ERR "%s: cannot load ARC4 module\n", fname);
+	    return NULL;
+	}
+
+	memcpy(state->master_key, options+CILEN_MPPE, MPPE_MAX_KEY_LEN);
+	memcpy(state->session_key, state->master_key, MPPE_MAX_KEY_LEN);
+	/* initial key generation is done in mppe_init() */
+    }
+
+    return (void *) state;
+}
+
+static void *
+mppe_comp_alloc(unsigned char *options, int opt_len)
+{
+    return mppe_alloc(options, opt_len, 1);
+}
+
+static void *
+mppe_decomp_alloc(unsigned char *options, int opt_len)
+{
+    return mppe_alloc(options, opt_len, 0);
+}
+
+/* cleanup the (de)compressor */
+static void
+mppe_comp_free(void *arg)
+{
+    struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
+
+    if (state != NULL) {
+	if (state->mppe) {
+	    if (state->arc4_tfm != NULL)
+		crypto_free_tfm(state->arc4_tfm);
+	}
+	if (state->hist != NULL)
+	    vfree(state->hist);
+	if (state->hash != NULL)
+	    vfree(state->hash);
+	kfree(state);
+    }
+}
+
+/* init MPPC/MPPE (de)compresor */
+/*   comp != 0 -> init compressor */
+/*   comp = 0 -> init decompressor */
+static int
+mppe_init(void *arg, unsigned char *options, int opt_len, int unit,
+	  int hdrlen, int mru, int debug, int comp)
+{
+    struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
+    u8* fname;
+
+    fname = comp ? "mppe_comp_init" : "mppe_decomp_init";
+
+    if (opt_len < CILEN_MPPE) {
+	if (debug)
+	    printk(KERN_WARNING "%s: wrong options length: %u\n",
+		   fname, opt_len);
+	return 0;
+    }
+
+    if (options[0] != CI_MPPE || options[1] != CILEN_MPPE ||
+	(options[2] & ~MPPE_STATELESS) != 0 ||
+	options[3] != 0 || options[4] != 0 ||
+	(options[5] & ~(MPPE_56BIT|MPPE_128BIT|MPPE_40BIT|MPPE_MPPC)) != 0 ||
+	(options[5] & (MPPE_56BIT|MPPE_128BIT|MPPE_40BIT|MPPE_MPPC)) == 0) {
+	if (debug)
+	    printk(KERN_WARNING "%s: options rejected: o[0]=%02x, o[1]=%02x, "
+		   "o[2]=%02x, o[3]=%02x, o[4]=%02x, o[5]=%02x\n", fname,
+		   options[0], options[1], options[2], options[3], options[4],
+		   options[5]);
+	return 0;
+    }
+
+    if ((options[5] & ~MPPE_MPPC) != MPPE_128BIT &&
+	(options[5] & ~MPPE_MPPC) != MPPE_56BIT &&
+	(options[5] & ~MPPE_MPPC) != MPPE_40BIT &&
+	(options[5] & MPPE_MPPC) != MPPE_MPPC) {
+	if (debug)
+	    printk(KERN_WARNING "%s: don't know what to do: o[5]=%02x\n",
+		   fname, options[5]);
+	return 0;
+    }
+
+    state->mppc = options[5] & MPPE_MPPC;	/* Do we use MPPC? */
+    state->mppe = options[5] & (MPPE_128BIT | MPPE_56BIT |
+	MPPE_40BIT);				/* Do we use MPPE? */
+    state->stateless = options[2] & MPPE_STATELESS; /* Do we use stateless mode? */
+
+    switch (state->mppe) {
+    case MPPE_40BIT:     /* 40 bit key */
+	state->keylen = 8;
+	state->bitkeylen = 40;
+	break;
+    case MPPE_56BIT:     /* 56 bit key */
+	state->keylen = 8;
+	state->bitkeylen = 56;
+	break;
+    case MPPE_128BIT:    /* 128 bit key */
+	state->keylen = 16;
+	state->bitkeylen = 128;
+	break;
+    default:
+	state->keylen = 0;
+	state->bitkeylen = 0;
+    }
+
+    state->ccount = MPPE_MAX_CCOUNT;
+    state->bits = 0;
+    state->unit  = unit;
+    state->debug = debug;
+    state->histptr = MPPE_HIST_LEN;
+    if (state->mppc) {	/* reset history if MPPC was negotiated */
+	memset(state->hist, 0, 2*MPPE_HIST_LEN*sizeof(u8));
+    }
+
+    if (state->mppe) { /* generate initial session keys */
+	mppe_change_key(state, 1);
+    }
+
+    if (comp) { /* specific for compressor */
+	state->nextflushed = 1;
+    } else { /* specific for decompressor */
+	state->mru = mru;
+	state->flushexpected = 1;
+    }
+
+    return 1;
+}
+
+static int
+mppe_comp_init(void *arg, unsigned char *options, int opt_len, int unit,
+	       int hdrlen, int debug)
+{
+    return mppe_init(arg, options, opt_len, unit, hdrlen, 0, debug, 1);
+}
+
+
+static int
+mppe_decomp_init(void *arg, unsigned char *options, int opt_len, int unit,
+		 int hdrlen, int mru, int debug)
+{
+    return mppe_init(arg, options, opt_len, unit, hdrlen, mru, debug, 0);
+}
+
+static void
+mppe_comp_reset(void *arg)
+{
+    struct ppp_mppe_state *state = (struct ppp_mppe_state *)arg;
+
+    if (state->debug)
+	printk(KERN_DEBUG "%s%d: resetting MPPC/MPPE compressor\n",
+	       __FUNCTION__, state->unit);
+
+    state->nextflushed = 1;
+    if (state->mppe)
+	arc4_setkey(state, state->session_key, state->keylen);
+}
+
+static void
+mppe_decomp_reset(void *arg)
+{
+    /* When MPPC/MPPE is in use, we shouldn't receive any CCP Reset-Ack.
+ *        But when we receive such a packet, we just ignore it. */
+    return;
+}
+
+static void
+mppe_stats(void *arg, struct compstat *stats)
+{
+    struct ppp_mppe_state *state = (struct ppp_mppe_state *)arg;
+
+    *stats = state->stats;
+}
+
+/***************************/
+/**** Compression stuff ****/
+/***************************/
+/* inserts 1 to 8 bits into the output buffer */
+static inline void putbits8(u8 *buf, u32 val, const u32 n, u32 *i, u32 *l)
+{
+    buf += *i;
+    if (*l >= n) {
+	*l = (*l) - n;
+	val <<= *l;
+	*buf = *buf | (val & 0xff);
+	if (*l == 0) {
+	    *l = 8;
+	    (*i)++;
+	    *(++buf) = 0;
+	}
+    } else {
+	(*i)++;
+	*l = 8 - n + (*l);
+	val <<= *l;
+	*buf = *buf | ((val >> 8) & 0xff);
+	*(++buf) = val & 0xff;
+    }
+}
+
+/* inserts 9 to 16 bits into the output buffer */
+static inline void putbits16(u8 *buf, u32 val, const u32 n, u32 *i, u32 *l)
+{
+    buf += *i;
+    if (*l >= n - 8) {
+	(*i)++;
+	*l = 8 - n + (*l);
+	val <<= *l;
+	*buf = *buf | ((val >> 8) & 0xff);
+	*(++buf) = val & 0xff;
+	if (*l == 0) {
+	    *l = 8;
+	    (*i)++;
+	    *(++buf) = 0;
+	}
+    } else {
+	(*i)++; (*i)++;
+	*l = 16 - n + (*l);
+	val <<= *l;
+	*buf = *buf | ((val >> 16) & 0xff);
+	*(++buf) = (val >> 8) & 0xff;
+	*(++buf) = val & 0xff;
+    }
+}
+
+/* inserts 17 to 24 bits into the output buffer */
+static inline void putbits24(u8 *buf, u32 val, const u32 n, u32 *i, u32 *l)
+{
+    buf += *i;
+    if (*l >= n - 16) {
+	(*i)++; (*i)++;
+	*l = 16 - n + (*l);
+	val <<= *l;
+	*buf = *buf | ((val >> 16) & 0xff);
+	*(++buf) = (val >> 8) & 0xff;
+	*(++buf) = val & 0xff;
+	if (*l == 0) {
+	    *l = 8;
+	    (*i)++;
+	    *(++buf) = 0;
+	}
+    } else {
+	(*i)++; (*i)++; (*i)++;
+	*l = 24 - n + (*l);
+	val <<= *l;
+	*buf = *buf | ((val >> 24) & 0xff);
+	*(++buf) = (val >> 16) & 0xff;
+	*(++buf) = (val >> 8) & 0xff;
+	*(++buf) = val & 0xff;
+    }
+}
+
+static int
+mppc_compress(struct ppp_mppe_state *state, unsigned char *ibuf,
+	      unsigned char *obuf, int isize, int osize)
+{
+    u32 olen, off, len, idx, i, l;
+    u8 *hist, *sbuf, *p, *q, *r, *s;
+
+    /*  
+  	At this point, to avoid possible buffer overflow caused by packet
+  	expansion during/after compression,  we should make sure that
+  	osize >= (((isize*9)/8)+1)+2, but we don't do that because in
+  	ppp_generic.c we simply allocate bigger obuf.
+
+  	Maximum MPPC packet expansion is 12.5%. This is the worst case when
+  	all octets in the input buffer are >= 0x80 and we cannot find any
+  	repeated tokens. Additionally we have to reserve 2 bytes for MPPE/MPPC
+  	status bits and coherency counter.
+  	*/
+
+    hist = state->hist + MPPE_HIST_LEN;
+    /* check if there is enough room at the end of the history */
+    if (state->histptr + isize >= 2*MPPE_HIST_LEN) {
+	state->bits |= MPPE_BIT_RESET;
+	state->histptr = MPPE_HIST_LEN;
+	memcpy(state->hist, hist, MPPE_HIST_LEN);
+    }
+    /* add packet to the history; isize must be <= MPPE_HIST_LEN */
+    sbuf = state->hist + state->histptr;
+    memcpy(sbuf, ibuf, isize);
+    state->histptr += isize;
+
+    /* compress data */
+    r = sbuf + isize;
+    *obuf = olen = i = 0;
+    l = 8;
+    while (i < isize - 2) {
+	s = q = sbuf + i;
+	idx = ((40543*((((s[0]<<4)^s[1])<<4)^s[2]))>>4) & 0x1fff;
+	p = hist + state->hash[idx];
+	state->hash[idx] = (u16) (s - hist);
+	off = s - p;
+	if (off > MPPE_HIST_LEN - 1 || off < 1 || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++) {
+	    /* no match found; encode literal byte */
+	    if (ibuf[i] < 0x80) {		/* literal byte < 0x80 */
+		putbits8(obuf, (u32) ibuf[i], 8, &olen, &l);
+	    } else {				/* literal byte >= 0x80 */
+		putbits16(obuf, (u32) (0x100|(ibuf[i]&0x7f)), 9, &olen, &l);
+	    }
+	    ++i;
+	    continue;
+	}
+	if (r - q >= 64) {
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++ || *p++ != *s++ || *p++ != *s++ || *p++ != *s++ ||
+	    *p++ != *s++;
+	    if (s - q == 64) {
+		p--; s--;
+		while((*p++ == *s++) && (s < r) && (p < q));
+	    }
+	} else {
+	    while((*p++ == *s++) && (s < r) && (p < q));
+	}
+	len = s - q - 1;
+	i += len;
+
+	/* at least 3 character match found; code data */
+	/* encode offset */
+	if (off < 64) {			/* 10-bit offset; 0 <= offset < 64 */
+	    putbits16(obuf, 0x3c0|off, 10, &olen, &l);
+	} else if (off < 320) {		/* 12-bit offset; 64 <= offset < 320 */
+	    putbits16(obuf, 0xe00|(off-64), 12, &olen, &l);
+	} else if (off < 8192) {	/* 16-bit offset; 320 <= offset < 8192 */
+	    putbits16(obuf, 0xc000|(off-320), 16, &olen, &l);
+	} else {
+	    /* This shouldn't happen; we return 0 what means "packet expands",
+ 	    and we send packet uncompressed. */
+	    if (state->debug)
+		printk(KERN_DEBUG "%s%d: wrong offset value: %d\n",
+		       __FUNCTION__, state->unit, off);
+	    return 0;
+	}
+	/* encode length of match */
+	if (len < 4) {			/* length = 3 */
+	    putbits8(obuf, 0, 1, &olen, &l);
+	} else if (len < 8) {		/* 4 <= length < 8 */
+	    putbits8(obuf, 0x08|(len&0x03), 4, &olen, &l);
+	} else if (len < 16) {		/* 8 <= length < 16 */
+	    putbits8(obuf, 0x30|(len&0x07), 6, &olen, &l);
+	} else if (len < 32) {		/* 16 <= length < 32 */
+	    putbits8(obuf, 0xe0|(len&0x0f), 8, &olen, &l);
+	} else if (len < 64) {		/* 32 <= length < 64 */
+	    putbits16(obuf, 0x3c0|(len&0x1f), 10, &olen, &l);
+	} else if (len < 128) {		/* 64 <= length < 128 */
+	    putbits16(obuf, 0xf80|(len&0x3f), 12, &olen, &l);
+	} else if (len < 256) {		/* 128 <= length < 256 */
+	    putbits16(obuf, 0x3f00|(len&0x7f), 14, &olen, &l);
+	} else if (len < 512) {		/* 256 <= length < 512 */
+	    putbits16(obuf, 0xfe00|(len&0xff), 16, &olen, &l);
+	} else if (len < 1024) {	/* 512 <= length < 1024 */
+	    putbits24(obuf, 0x3fc00|(len&0x1ff), 18, &olen, &l);
+	} else if (len < 2048) {	/* 1024 <= length < 2048 */
+	    putbits24(obuf, 0xff800|(len&0x3ff), 20, &olen, &l);
+	} else if (len < 4096) {	/* 2048 <= length < 4096 */
+	    putbits24(obuf, 0x3ff000|(len&0x7ff), 22, &olen, &l);
+	} else if (len < 8192) {	/* 4096 <= length < 8192 */
+	    putbits24(obuf, 0xffe000|(len&0xfff), 24, &olen, &l);
+	} else {
+	    /* This shouldn't happen; we return 0 what means "packet expands",
+ 	    and send packet uncompressed. */
+	    if (state->debug)
+		printk(KERN_DEBUG "%s%d: wrong length of match value: %d\n",
+		       __FUNCTION__, state->unit, len);
+	    return 0;
+	}
+    }
+
+    /* Add remaining octets to the output */
+    while(isize - i > 0) {
+	if (ibuf[i] < 0x80) {	/* literal byte < 0x80 */
+	    putbits8(obuf, (u32) ibuf[i++], 8, &olen, &l);
+	} else {		/* literal byte >= 0x80 */
+	    putbits16(obuf, (u32) (0x100|(ibuf[i++]&0x7f)), 9, &olen, &l);
+	}
+    }
+    /* Reset unused bits of the last output octet */
+    if ((l != 0) && (l != 8)) {
+	putbits8(obuf, 0, l, &olen, &l);
+    }
+
+    return (int) olen;
+}
+
+int
+mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
+	      int isize, int osize)
+{
+    struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
+    int proto, olen, complen, off;
+    unsigned char *wptr;
+
+    /* Check that the protocol is in the range we handle. */
+    proto = PPP_PROTOCOL(ibuf);
+    if (proto < 0x0021 || proto > 0x00fa)
+	return 0;
+
+    wptr = obuf;
+    /* Copy over the PPP header */
+    wptr[0] = PPP_ADDRESS(ibuf);
+    wptr[1] = PPP_CONTROL(ibuf);
+    wptr[2] = PPP_COMP >> 8;
+    wptr[3] = PPP_COMP;
+    wptr += PPP_HDRLEN + (MPPE_OVHD / 2); /* Leave two octets for MPPE/MPPC bits */
+
+    /* 
+     * In ver. 0.99 protocol field was compressed. Deflate and BSD compress
+     * do PFC before actual compression, RCF2118 and RFC3078 are not precise
+     * on this topic so I decided to do PFC. Unfortunately this change caused
+     * incompatibility with older/other MPPE/MPPC modules. I have received
+     * a lot of complaints from unexperienced users so I have decided to revert
+     * to previous state, i.e. the protocol field is sent uncompressed now.
+     * Although this may be changed in the future.
+     *
+     * Receiving side (mppe_decompress()) still accepts packets with compressed
+     * and uncompressed protocol field so you shouldn't get "Unsupported protocol
+     * 0x2145 received" messages anymore.
+     */
+    //off = (proto > 0xff) ? 2 : 3; /* PFC - skip first protocol byte if 0 */
+    off = 2;
+
+    ibuf += off;
+
+    mppe_increase_ccount(state);
+
+    if (state->nextflushed) {
+	state->bits |= MPPE_BIT_FLUSHED;
+	state->nextflushed = 0;
+	if (state->mppe && !state->stateless) {
+	    /*
+ 	     * If this is the flag packet, the key has been already changed in
+ 	     * mppe_increase_ccount() so we dont't do it once again.
+ 	     */
+	    if ((state->ccount & 0xff) != 0xff) {
+		arc4_setkey(state, state->session_key, state->keylen);
+	    }
+	}
+	if (state->mppc) { /* reset history */
+	    state->bits |= MPPE_BIT_RESET;
+	    state->histptr = MPPE_HIST_LEN;
+	    memset(state->hist + MPPE_HIST_LEN, 0, MPPE_HIST_LEN*sizeof(u8));
+	}
+    }
+
+    if (state->mppc && !state->mppe) { /* Do only compression */
+	complen = mppc_compress(state, ibuf, wptr, isize - off,
+				osize - PPP_HDRLEN - (MPPE_OVHD / 2));
+	/*
+ 	 * TODO: Implement an heuristics to handle packet expansion in a smart
+ 	 * way. Now, when a packet expands, we send it as uncompressed and
+ 	 * when next packet is sent we have to reset compressor's history.
+ 	 * Maybe it would be better to send such packet as compressed in order
+ 	 * to keep history's continuity.
+ 	 */
+	if ((complen > isize) || (complen > osize - PPP_HDRLEN) ||
+	    (complen == 0)) {
+	    /* packet expands */
+	    state->nextflushed = 1;
+	    memcpy(wptr, ibuf, isize - off);
+	    olen = isize - (off - 2) + MPPE_OVHD;
+	    (state->stats).inc_bytes += olen;
+	    (state->stats).inc_packets++;
+	} else {
+	    state->bits |= MPPE_BIT_COMP;
+	    olen = complen + PPP_HDRLEN + (MPPE_OVHD / 2);
+	    (state->stats).comp_bytes += olen;
+	    (state->stats).comp_packets++;
+	}
+    } else { /* Do encryption with or without compression */
+	state->bits |= MPPE_BIT_ENCRYPTED;
+	if (!state->mppc && state->mppe) { /* Do only encryption */
+	    /* read from ibuf, write to wptr, adjust for PPP_HDRLEN */
+	    arc4_encrypt(state, ibuf, isize - off, wptr);
+	    olen = isize - (off - 2) + MPPE_OVHD;
+	    (state->stats).inc_bytes += olen;
+	    (state->stats).inc_packets++;
+	} else { /* Do compression and then encryption - RFC3078 */
+	    complen = mppc_compress(state, ibuf, wptr, isize - off,
+				    osize - PPP_HDRLEN - (MPPE_OVHD / 2));
+	    /*
+ 	     * TODO: Implement an heuristics to handle packet expansion in a smart
+ 	     * way. Now, when a packet expands, we send it as uncompressed and
+ 	     * when next packet is sent we have to reset compressor's history.
+ 	     * Maybe it would be good to send such packet as compressed in order
+ 	     * to keep history's continuity.
+ 	     */
+	    if ((complen > isize) || (complen > osize - PPP_HDRLEN) ||
+		(complen == 0)) {
+		/* packet expands */
+		state->nextflushed = 1;
+		arc4_encrypt(state, ibuf, isize - off, wptr);
+		olen = isize - (off - 2) + MPPE_OVHD;
+		(state->stats).inc_bytes += olen;
+		(state->stats).inc_packets++;
+	    } else {
+		state->bits |= MPPE_BIT_COMP;
+		/* Hack warning !!! RC4 implementation which we use does
+ 		   encryption "in place" - it means that input and output
+ 		   buffers can be *the same* memory area. Therefore we don't
+ 		   need to use a temporary buffer. But be careful - other
+ 		   implementations don't have to be so nice.
+ 		   I used to use ibuf as temporary buffer here, but it led
+ 		   packet sniffers into error. Thanks to Wilfried Weissmann
+ 		   for pointing that. */
+		arc4_encrypt(state, wptr, complen, wptr);
+		olen = complen + PPP_HDRLEN + (MPPE_OVHD / 2);
+		(state->stats).comp_bytes += olen;
+		(state->stats).comp_packets++;
+	    }
+	}
+    }
+
+    /* write status bits and coherency counter into the output buffer */
+    wptr = obuf + PPP_HDRLEN;
+    wptr[0] = MPPE_CTRLHI(state);
+    wptr[1] = MPPE_CTRLLO(state);
+
+    state->bits = 0;
+
+    (state->stats).unc_bytes += isize;
+    (state->stats).unc_packets++;
+
+    return olen;
+}
+
+/***************************/
+/*** Decompression stuff ***/
+/***************************/
+static inline u32 getbits(const u8 *buf, const u32 n, u32 *i, u32 *l)
+{
+    static const u32 m[] = {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
+    u32 res, ol;
+
+    ol = *l;
+    if (*l >= n) {
+	*l = (*l) - n;
+	res = (buf[*i] & m[ol]) >> (*l);
+	if (*l == 0) {
+	    *l = 8;
+	    (*i)++;
+	}
+    } else {
+	*l = 8 - n + (*l);
+	res = (buf[(*i)++] & m[ol]) << 8;
+	res = (res | buf[*i]) >> (*l);
+    }
+
+    return res;
+}
+
+static inline u32 getbyte(const u8 *buf, const u32 i, const u32 l)
+{
+    if (l == 8) {
+	return buf[i];
+    } else {
+	return (((buf[i] << 8) | buf[i+1]) >> l) & 0xff;
+    }
+}
+
+static inline void lamecopy(u8 *dst, u8 *src, u32 len)
+{
+    while (len--)
+	*dst++ = *src++;
+}
+
+static int
+mppc_decompress(struct ppp_mppe_state *state, unsigned char *ibuf,
+		unsigned char *obuf, int isize, int osize)
+{
+    u32 olen, off, len, bits, val, sig, i, l;
+    u8 *history, *s;
+
+    history = state->hist + state->histptr;
+    olen = len = i = 0;
+    l = 8;
+    bits = isize * 8;
+    while (bits >= 8) {
+	val = getbyte(ibuf, i++, l);
+	if (val < 0x80) {		/* literal byte < 0x80 */
+	    if (state->histptr < 2*MPPE_HIST_LEN) {
+		/* copy uncompressed byte to the history */
+		(state->hist)[(state->histptr)++] = (u8) val;
+	    } else {
+		/* buffer overflow; drop packet */
+		if (state->debug)
+		    printk(KERN_ERR "%s%d: trying to write outside history "
+			   "buffer\n", __FUNCTION__, state->unit);
+		return DECOMP_ERROR;
+	    }
+	    olen++;
+	    bits -= 8;
+	    continue;
+	}
+
+	sig = val & 0xc0;
+	if (sig == 0x80) {		/* literal byte >= 0x80 */
+	    if (state->histptr < 2*MPPE_HIST_LEN) {
+		/* copy uncompressed byte to the history */
+		(state->hist)[(state->histptr)++] = 
+		    (u8) (0x80|((val&0x3f)<<1)|getbits(ibuf, 1 , &i ,&l));
+	    } else {
+		/* buffer overflow; drop packet */
+		if (state->debug)
+		    printk(KERN_ERR "%s%d: trying to write outside history "
+			   "buffer\n", __FUNCTION__, state->unit);
+		return DECOMP_ERROR;
+	    }
+	    olen++;
+	    bits -= 9;
+	    continue;
+	}
+
+	/* Not a literal byte so it must be an (offset,length) pair */
+	/* decode offset */
+	sig = val & 0xf0;
+	if (sig == 0xf0) {		/* 10-bit offset; 0 <= offset < 64 */
+	    off = (((val&0x0f)<<2)|getbits(ibuf, 2 , &i ,&l));
+	    bits -= 10;
+	} else {
+	    if (sig == 0xe0) {		/* 12-bit offset; 64 <= offset < 320 */
+		off = ((((val&0x0f)<<4)|getbits(ibuf, 4 , &i ,&l))+64);
+		bits -= 12;
+	    } else {
+		if ((sig&0xe0) == 0xc0) {/* 16-bit offset; 320 <= offset < 8192 */
+		    off = ((((val&0x1f)<<8)|getbyte(ibuf, i++, l))+320);
+		    bits -= 16;
+		    if (off > MPPE_HIST_LEN - 1) {
+			if (state->debug)
+			    printk(KERN_DEBUG "%s%d: too big offset value: %d\n",
+				   __FUNCTION__, state->unit, off);
+			return DECOMP_ERROR;
+		    }
+		} else {		/* this shouldn't happen */
+		    if (state->debug)
+			printk(KERN_DEBUG "%s%d: cannot decode offset value\n",
+			       __FUNCTION__, state->unit);
+		    return DECOMP_ERROR;
+		}
+	    }
+	}
+	/* decode length of match */
+	val = getbyte(ibuf, i, l);
+	if ((val & 0x80) == 0x00) {			/* len = 3 */
+	    len = 3;
+	    bits--;
+	    getbits(ibuf, 1 , &i ,&l);
+	} else if ((val & 0xc0) == 0x80) {		/* 4 <= len < 8 */
+	    len = 0x04 | ((val>>4) & 0x03);
+	    bits -= 4;
+	    getbits(ibuf, 4 , &i ,&l);
+	} else if ((val & 0xe0) == 0xc0) {		/* 8 <= len < 16 */
+	    len = 0x08 | ((val>>2) & 0x07);
+	    bits -= 6;
+	    getbits(ibuf, 6 , &i ,&l);
+	} else if ((val & 0xf0) == 0xe0) {		/* 16 <= len < 32 */
+	    len = 0x10 | (val & 0x0f);
+	    bits -= 8;
+	    i++;
+	} else {
+	    bits -= 8;
+	    val = (val << 8) | getbyte(ibuf, ++i, l);
+	    if ((val & 0xf800) == 0xf000) {		/* 32 <= len < 64 */
+		len = 0x0020 | ((val >> 6) & 0x001f);
+		bits -= 2;
+		getbits(ibuf, 2 , &i ,&l);
+	    } else if ((val & 0xfc00) == 0xf800) {	/* 64 <= len < 128 */
+		len = 0x0040 | ((val >> 4) & 0x003f);
+		bits -= 4;
+		getbits(ibuf, 4 , &i ,&l);
+	    } else if ((val & 0xfe00) == 0xfc00) {	/* 128 <= len < 256 */
+		len = 0x0080 | ((val >> 2) & 0x007f);
+		bits -= 6;
+		getbits(ibuf, 6 , &i ,&l);
+	    } else if ((val & 0xff00) == 0xfe00) {	/* 256 <= len < 512 */
+		len = 0x0100 | (val & 0x00ff);
+		bits -= 8;
+		i++;
+	    } else {
+		bits -= 8;
+		val = (val << 8) | getbyte(ibuf, ++i, l);
+		if ((val & 0xff8000) == 0xff0000) {	/* 512 <= len < 1024 */
+		    len = 0x000200 | ((val >> 6) & 0x0001ff);
+		    bits -= 2;
+		    getbits(ibuf, 2 , &i ,&l);
+		} else if ((val & 0xffc000) == 0xff8000) {/* 1024 <= len < 2048 */
+		    len = 0x000400 | ((val >> 4) & 0x0003ff);
+		    bits -= 4;
+		    getbits(ibuf, 4 , &i ,&l);
+		} else if ((val & 0xffe000) == 0xffc000) {/* 2048 <= len < 4096 */
+		    len = 0x000800 | ((val >> 2) & 0x0007ff);
+		    bits -= 6;
+		    getbits(ibuf, 6 , &i ,&l);
+		} else if ((val & 0xfff000) == 0xffe000) {/* 4096 <= len < 8192 */
+		    len = 0x001000 | (val & 0x000fff);
+		    bits -= 8;
+		    i++;
+		} else {				/* this shouldn't happen */
+		    if (state->debug)
+			printk(KERN_DEBUG "%s%d: wrong length code: 0x%X\n",
+			       __FUNCTION__, state->unit, val);
+		    return DECOMP_ERROR;
+		}
+	    }
+	}
+	s = state->hist + state->histptr;
+	state->histptr += len;
+	olen += len;
+	if (state->histptr < 2*MPPE_HIST_LEN) {
+	    /* copy uncompressed bytes to the history */
+
+	    /* In some cases len may be greater than off. It means that memory
+ 	     * areas pointed by s and s-off overlap. I had used memmove() here
+ 	     * because I thought that it acts as libc's version. Unfortunately,
+ 	     * I was wrong. :-) I got strange errors sometimes. Wilfried suggested
+ 	     * using of byte by byte copying here and strange errors disappeared.
+ 	     */
+	    lamecopy(s, s - off, len);
+	} else {
+	    /* buffer overflow; drop packet */
+	    if (state->debug)
+		printk(KERN_ERR "%s%d: trying to write outside history "
+		       "buffer\n", __FUNCTION__, state->unit);
+	    return DECOMP_ERROR;
+	}
+    }
+
+    /* Do PFC decompression */
+    len = olen;
+    if ((history[0] & 0x01) != 0) {
+	obuf[0] = 0;
+	obuf++;
+	len++;
+    }
+
+    if (len <= osize) {
+	/* copy uncompressed packet to the output buffer */
+	memcpy(obuf, history, olen);
+    } else {
+	/* buffer overflow; drop packet */
+	if (state->debug)
+	    printk(KERN_ERR "%s%d: too big uncompressed packet: %d\n",
+		   __FUNCTION__, state->unit, len + (PPP_HDRLEN / 2));
+	return DECOMP_ERROR;
+    }
+
+    return (int) len;
+}
+
+int
+mppe_decompress(void *arg, unsigned char *ibuf, int isize,
+		unsigned char *obuf, int osize)
+{
+    struct ppp_mppe_state *state = (struct ppp_mppe_state *)arg;
+    int seq, bits, uncomplen;
+
+    if (isize <= PPP_HDRLEN + MPPE_OVHD) {
+	if (state->debug) {
+	    printk(KERN_DEBUG "%s%d: short packet (len=%d)\n",  __FUNCTION__,
+		   state->unit, isize);
+	}
+	return DECOMP_ERROR;
+    }
+
+    /* Get coherency counter and control bits from input buffer */
+    seq = MPPE_CCOUNT(ibuf);
+    bits = MPPE_BITS(ibuf);
+
+    if (state->stateless) {
+	/* RFC 3078, sec 8.1. */
+	mppe_increase_ccount(state);
+	if ((seq != state->ccount) && state->debug)
+	    printk(KERN_DEBUG "%s%d: bad sequence number: %d, expected: %d\n",
+		   __FUNCTION__, state->unit, seq, state->ccount);
+	while (seq != state->ccount)
+	    mppe_increase_ccount(state);
+    } else {
+	/* RFC 3078, sec 8.2. */
+	if (state->flushexpected) { /* discard state */
+	    if ((bits & MPPE_BIT_FLUSHED)) { /* we received expected FLUSH bit */
+		while (seq != state->ccount)
+		    mppe_increase_ccount(state);
+		state->flushexpected = 0;
+	    } else /* drop packet*/
+		return DECOMP_ERROR;
+	} else { /* normal state */
+	    mppe_increase_ccount(state);
+	    if (seq != state->ccount) {
+		/* Packet loss detected, enter the discard state. */
+		if (state->debug)
+		    printk(KERN_DEBUG "%s%d: bad sequence number: %d, expected: %d\n",
+			   __FUNCTION__, state->unit, seq, state->ccount);
+		state->flushexpected = 1;
+		return DECOMP_ERROR;
+	    }
+	}
+	if (state->mppe && (bits & MPPE_BIT_FLUSHED)) {
+	    arc4_setkey(state, state->session_key, state->keylen);
+	}
+    }
+
+    if (state->mppc && (bits & (MPPE_BIT_FLUSHED | MPPE_BIT_RESET))) {
+	state->histptr = MPPE_HIST_LEN;
+	if ((bits & MPPE_BIT_FLUSHED)) {
+	    memset(state->hist + MPPE_HIST_LEN, 0, MPPE_HIST_LEN*sizeof(u8));
+	} else
+	    if ((bits & MPPE_BIT_RESET)) {
+		memcpy(state->hist, state->hist + MPPE_HIST_LEN, MPPE_HIST_LEN);
+	    }
+    }
+
+    /* Fill in the first part of the PPP header. The protocol field
+       comes from the decompressed data. */
+    obuf[0] = PPP_ADDRESS(ibuf);
+    obuf[1] = PPP_CONTROL(ibuf);
+    obuf += PPP_HDRLEN / 2;
+
+    if (state->mppe) { /* process encrypted packet */
+	if ((bits & MPPE_BIT_ENCRYPTED)) {
+	    /* OK, packet encrypted, so decrypt it */
+	    if (state->mppc && (bits & MPPE_BIT_COMP)) {
+		/* Hack warning !!! RC4 implementation which we use does
+ 		   decryption "in place" - it means that input and output
+ 		   buffers can be *the same* memory area. Therefore we don't
+ 		   need to use a temporary buffer. But be careful - other
+ 		   implementations don't have to be so nice. */
+		arc4_decrypt(state, ibuf + PPP_HDRLEN +	(MPPE_OVHD / 2), isize -
+			     PPP_HDRLEN - (MPPE_OVHD / 2), ibuf + PPP_HDRLEN +
+			     (MPPE_OVHD / 2));
+		uncomplen = mppc_decompress(state, ibuf + PPP_HDRLEN +
+					    (MPPE_OVHD / 2), obuf, isize -
+					    PPP_HDRLEN - (MPPE_OVHD / 2),
+					    osize - (PPP_HDRLEN / 2));
+		if (uncomplen == DECOMP_ERROR) {
+		    state->flushexpected = 1;
+		    return DECOMP_ERROR;
+		}
+		uncomplen += PPP_HDRLEN / 2;
+		(state->stats).comp_bytes += isize;
+		(state->stats).comp_packets++;
+	    } else {
+		uncomplen = isize - MPPE_OVHD;
+		/* Decrypt the first byte in order to check if it is
+ 		   compressed or uncompressed protocol field */
+		arc4_decrypt(state, ibuf + PPP_HDRLEN +	(MPPE_OVHD / 2), 1, obuf);
+		/* Do PFC decompression */
+		if ((obuf[0] & 0x01) != 0) {
+		    obuf[1] = obuf[0];
+		    obuf[0] = 0;
+		    obuf++;
+		    uncomplen++;
+		}
+		/* And finally, decrypt the rest of the frame. */
+		arc4_decrypt(state, ibuf + PPP_HDRLEN +	(MPPE_OVHD / 2) + 1,
+			     isize - PPP_HDRLEN - (MPPE_OVHD / 2) - 1, obuf + 1);
+		(state->stats).inc_bytes += isize;
+		(state->stats).inc_packets++;
+	    }
+	} else { /* this shouldn't happen */
+	    if (state->debug)
+		printk(KERN_ERR "%s%d: encryption negotiated but not an "
+		       "encrypted packet received\n", __FUNCTION__, state->unit);
+	    mppe_change_key(state, 0);
+	    state->flushexpected = 1;
+	    return DECOMP_ERROR;
+	}
+    } else {
+	if (state->mppc) { /* no MPPE, only MPPC */
+	    if ((bits & MPPE_BIT_COMP)) {
+		uncomplen = mppc_decompress(state, ibuf + PPP_HDRLEN +
+					    (MPPE_OVHD / 2), obuf, isize -
+					    PPP_HDRLEN - (MPPE_OVHD / 2),
+					    osize - (PPP_HDRLEN / 2));
+		if (uncomplen == DECOMP_ERROR) {
+		    state->flushexpected = 1;
+		    return DECOMP_ERROR;
+		}
+		uncomplen += PPP_HDRLEN / 2;
+		(state->stats).comp_bytes += isize;
+		(state->stats).comp_packets++;
+	    } else {
+		memcpy(obuf, ibuf + PPP_HDRLEN + (MPPE_OVHD / 2), isize -
+		       PPP_HDRLEN - (MPPE_OVHD / 2));
+		uncomplen = isize - MPPE_OVHD;
+		(state->stats).inc_bytes += isize;
+		(state->stats).inc_packets++;
+	    }
+	} else { /* this shouldn't happen */
+	    if (state->debug)
+		printk(KERN_ERR "%s%d: error - not an  MPPC or MPPE frame "
+		       "received\n", __FUNCTION__, state->unit);
+	    state->flushexpected = 1;
+	    return DECOMP_ERROR;
+	}
+    }
+
+    (state->stats).unc_bytes += uncomplen;
+    (state->stats).unc_packets++;
+
+    return uncomplen;
+}
+
+
+/************************************************************
+ *  * Module interface table
+ *   ************************************************************/
+
+/* These are in ppp_generic.c */
+extern int  ppp_register_compressor   (struct compressor *cp);
+extern void ppp_unregister_compressor (struct compressor *cp);
+
+/*
+ * Functions exported to ppp_generic.c.
+ *
+ * In case of MPPC/MPPE there is no need to process incompressible data
+ * because such a data is sent in MPPC/MPPE frame. Therefore the (*incomp)
+ * callback function isn't needed.
+ */
+struct compressor ppp_mppe = {
+    .compress_proto =	CI_MPPE,
+    .comp_alloc =	mppe_comp_alloc,
+    .comp_free =	mppe_comp_free,
+    .comp_init =	mppe_comp_init,
+    .comp_reset =	mppe_comp_reset,
+    .compress =		mppe_compress,
+    .comp_stat =	mppe_stats,
+    .decomp_alloc =	mppe_decomp_alloc,
+    .decomp_free =	mppe_comp_free,
+    .decomp_init =	mppe_decomp_init,
+    .decomp_reset =	mppe_decomp_reset,
+    .decompress =	mppe_decompress,
+    .incomp =		NULL,
+    .decomp_stat =	mppe_stats,
+    .owner =		THIS_MODULE
+};
+
+/************************************************************
+ * Module support routines
+ ************************************************************/
+
+int __init mppe_module_init(void)
+{
+    int answer = ppp_register_compressor(&ppp_mppe);
+    if (answer == 0) {
+	printk(KERN_INFO "MPPE/MPPC encryption/compression module registered\n");
+    }
+    return answer;
+}
+
+void __exit mppe_module_cleanup(void)
+{
+    ppp_unregister_compressor(&ppp_mppe);
+    printk(KERN_INFO "MPPE/MPPC encryption/compression module unregistered\n");
+}
+
+module_init(mppe_module_init);
+module_exit(mppe_module_cleanup);
+
+MODULE_AUTHOR("Jan Dubiec <jdx@slackware.pl>");
+MODULE_DESCRIPTION("MPPE/MPPC encryption/compression module for Linux");
+MODULE_VERSION("1.1");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
+
+/*
+ * SHA1 implementation
+ */
+static void SHA1_Transform(u32[5], const u8[64]);
+
+#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))
+
+/* blk0() and blk() perform the initial expand. */
+/* I got the idea of expanding during the round function from SSLeay */
+#if defined(__LITTLE_ENDIAN) || defined(_LITTLE_ENDIAN)
+#define blk0(i) (block->l[i] = (rol(block->l[i],24)&0xFF00FF00) \
+    |(rol(block->l[i],8)&0x00FF00FF))
+#elif defined(__BIG_ENDIAN) || defined(_BIG_ENDIAN)
+#define blk0(i) block->l[i]
+#else
+#error Endianness not defined
+#endif
+#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15]^block->l[(i+8)&15] \
+    ^block->l[(i+2)&15]^block->l[i&15],1))
+
+/* (R0+R1), R2, R3, R4 are the different operations used in SHA1 */
+#define R0(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk0(i)+0x5A827999+rol(v,5);w=rol(w,30);
+#define R1(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk(i)+0x5A827999+rol(v,5);w=rol(w,30);
+#define R2(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0x6ED9EBA1+rol(v,5);w=rol(w,30);
+#define R3(v,w,x,y,z,i) z+=(((w|x)&y)|(w&x))+blk(i)+0x8F1BBCDC+rol(v,5);w=rol(w,30);
+#define R4(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0xCA62C1D6+rol(v,5);w=rol(w,30);
+
+/* Hash a single 512-bit block. This is the core of the algorithm. */
+static void
+SHA1_Transform(u32 state[5], const u8 buffer[64])
+{
+    u32 a, b, c, d, e;
+    typedef union {
+	u8 c[64];
+	u32 l[16];
+    } CHAR64LONG16;
+    CHAR64LONG16 *block;
+
+#ifdef SHA1HANDSOFF
+    static u8 workspace[64];
+    block = (CHAR64LONG16 *) workspace;
+    memcpy(block, buffer, 64);
+#else
+    block = (CHAR64LONG16 *) buffer;
+#endif
+    /* Copy context->state[] to working vars */
+    a = state[0];
+    b = state[1];
+    c = state[2];
+    d = state[3];
+    e = state[4];
+    /* 4 rounds of 20 operations each. Loop unrolled. */
+    R0(a,b,c,d,e, 0); R0(e,a,b,c,d, 1); R0(d,e,a,b,c, 2); R0(c,d,e,a,b, 3);
+    R0(b,c,d,e,a, 4); R0(a,b,c,d,e, 5); R0(e,a,b,c,d, 6); R0(d,e,a,b,c, 7);
+    R0(c,d,e,a,b, 8); R0(b,c,d,e,a, 9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
+    R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
+    R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
+    R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
+    R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
+    R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
+    R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
+    R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
+    R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
+    R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
+    R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
+    R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
+    R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
+    R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
+    R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
+    R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
+    R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
+    R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);
+    /* Add the working vars back into context.state[] */
+    state[0] += a;
+    state[1] += b;
+    state[2] += c;
+    state[3] += d;
+    state[4] += e;
+    /* Wipe variables */
+#ifdef SHA1HANDSOFF
+    memset(&workspace, 0, sizeof(workspace));
+#endif
+    a = b = c = d = e = 0;
+}
+
+/* SHA1Init - Initialize new context */
+static void
+SHA1_Init(SHA1_CTX *context)
+{
+    /* SHA1 initialization constants */
+    context->state[0] = 0x67452301;
+    context->state[1] = 0xEFCDAB89;
+    context->state[2] = 0x98BADCFE;
+    context->state[3] = 0x10325476;
+    context->state[4] = 0xC3D2E1F0;
+    context->count[0] = context->count[1] = 0;
+}
+
+/* Run your data through this. */
+static void
+SHA1_Update(SHA1_CTX *context, const u8 *data, u32 len)
+{
+    u32 i, j;
+
+    j = (context->count[0] >> 3) & 63;
+    if ((context->count[0] += len << 3) < (len << 3)) context->count[1]++;
+    context->count[1] += (len >> 29);
+    if ((j + len) > 63) {
+	memcpy(&context->buffer[j], data, (i = 64-j));
+	SHA1_Transform(context->state, context->buffer);
+	for ( ; i + 63 < len; i += 64) {
+	    SHA1_Transform(context->state, &data[i]);
+	}
+	j = 0;
+    }
+    else
+	i = 0;
+
+    memcpy(&context->buffer[j], &data[i], len - i);
+}
+
+/* Add padding and return the message digest. */
+static void
+SHA1_Final(u8 digest[20], SHA1_CTX *context)
+{
+    u32 i, j;
+    u8 finalcount[8];
+
+    for (i = 0; i < 8; i++) {
+        finalcount[i] = (u8) ((context->count[(i >= 4 ? 0 : 1)]
+         >> ((3-(i & 3)) * 8) ) & 255);  /* Endian independent */
+    }
+    SHA1_Update(context, (u8 *) "\200", 1);
+    while ((context->count[0] & 504) != 448) {
+	SHA1_Update(context, (u8 *) "\0", 1);
+    }
+    SHA1_Update(context, finalcount, 8);  /* Should cause a SHA1Transform() */
+    for (i = 0; i < 20; i++) {
+	digest[i] = (u8) ((context->state[i>>2] >> ((3-(i & 3)) * 8) ) & 255);
+    }
+    /* Wipe variables */
+    i = j = 0;
+    memset(context->buffer, 0, 64);
+    memset(context->state, 0, 20);
+    memset(context->count, 0, 8);
+    memset(&finalcount, 0, 8);
+#ifdef SHA1HANDSOFF  /* make SHA1Transform overwrite it's own static vars */
+    SHA1Transform(context->state, context->buffer);
+#endif
+}
+