- obsolete

[packages/kernel.git] / 2.6.x-ppp_mppe.patch

diff -Nur linux-2.6.2.org/drivers/net/Kconfig linux-2.6.2/drivers/net/Kconfig
--- linux-2.6.2.org/drivers/net/Kconfig	2004-02-04 03:44:28.000000000 +0000
+++ linux-2.6.2/drivers/net/Kconfig	2004-02-05 09:45:21.000000000 +0000
@@ -2313,6 +2313,11 @@
 	  module; it is called bsd_comp and will show up in the directory
 	  modules once you have said "make modules". If unsure, say N.
 
+config PPP_MPPE
+	tristate "PPP MPPE commpression (encrypted) (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && PPP
+	help
+	
 config PPPOE
 	tristate "PPP over Ethernet (EXPERIMENTAL)"
 	depends on EXPERIMENTAL && PPP
diff -Nur linux-2.6.2.org/drivers/net/Makefile linux-2.6.2/drivers/net/Makefile
--- linux-2.6.2.org/drivers/net/Makefile	2004-02-04 03:43:34.000000000 +0000
+++ linux-2.6.2/drivers/net/Makefile	2004-02-05 10:36:30.000000000 +0000
@@ -4,6 +4,8 @@
 
 rcpci-objs	:=	rcpci45.o rclanmtl.o
 
+ppp_mppe-objs	:=	ppp_mppe_compress.o sha1.o arcfour.o
+
 ifeq ($(CONFIG_ISDN_PPP),y)
   obj-$(CONFIG_ISDN) += slhc.o
 endif
@@ -100,6 +102,7 @@
 obj-$(CONFIG_PPP) += ppp_generic.o slhc.o
 obj-$(CONFIG_PPP_ASYNC) += ppp_async.o
 obj-$(CONFIG_PPP_SYNC_TTY) += ppp_synctty.o
+obj-$(CONFIG_PPP_MPPE) += ppp_mppe.o
 obj-$(CONFIG_PPP_DEFLATE) += ppp_deflate.o
 obj-$(CONFIG_PPP_BSDCOMP) += bsd_comp.o
 obj-$(CONFIG_PPPOE) += pppox.o pppoe.o
diff -Nur linux-2.6.2.org/drivers/net/arcfour.c linux-2.6.2/drivers/net/arcfour.c
--- linux-2.6.2.org/drivers/net/arcfour.c	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.2/drivers/net/arcfour.c	2003-07-07 02:25:13.000000000 +0000
@@ -0,0 +1,75 @@
+/*
+ * arcfour.c
+ * by Frank Cusack <frank@google.com>
+ * 100% public domain
+ *
+ * Implemented from the description in _Applied Cryptography_, 2nd ed.
+ *
+ * ** Distribution ** of this software is unlimited and unrestricted.
+ *
+ * ** Use ** of this software is almost certainly legal; however, refer
+ * to <http://theory.lcs.mit.edu/~rivest/faq.html>.
+ */
+
+#include "arcfour.h"
+#if defined(__linux__)
+#include <linux/string.h>
+#endif
+
+#define swap(a, b)		\
+{				\
+    unsigned char t = b;	\
+    b = a;			\
+    a = t;			\
+}
+
+/*
+ * Initialize arcfour from a key.
+ */
+void
+arcfour_setkey(arcfour_context *context, const unsigned char *key,
+	       unsigned keylen)
+{
+    unsigned i, j;
+    unsigned char K[256];
+
+    context->i = context->j = 0;
+
+    for (i = 0; i < 256; i++) {
+	context->S[i] = i;
+	K[i] = key[i % keylen];
+    }
+
+    j = 0;
+    for (i = 0; i < 256; i++) {
+	j = (j + context->S[i] + K[i]) % 256;
+	swap(context->S[i], context->S[j]);
+    }
+
+    memset(K, 0, sizeof(K));
+}
+
+/*
+ * plaintext -> ciphertext (or vice versa)
+ */
+void
+arcfour_encrypt(arcfour_context *context, const unsigned char *in, unsigned len,
+		unsigned char *out)
+{
+    unsigned i = context->i;
+    unsigned j = context->j;
+    unsigned char *S = context->S;
+    unsigned char K;
+
+    while (len--) {
+	i = (i + 1) % 256;
+	j = (j + S[i]) % 256;
+	swap(S[i], S[j]);
+	K = S[(S[i] + S[j]) % 256];
+	*out++ = *in++ ^ K;
+    }
+
+    context->i = i;
+    context->j = j;
+}
+
diff -Nur linux-2.6.2.org/drivers/net/arcfour.h linux-2.6.2/drivers/net/arcfour.h
--- linux-2.6.2.org/drivers/net/arcfour.h	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.2/drivers/net/arcfour.h	2002-04-02 07:01:37.000000000 +0000
@@ -0,0 +1,17 @@
+/* arcfour.h */
+
+#ifndef _ARCFOUR_H
+#define _ARCFOUR_H
+
+typedef struct {
+    unsigned i;
+    unsigned j;
+    unsigned char S[256];
+} arcfour_context;
+
+extern void arcfour_setkey(arcfour_context *, const unsigned char *, unsigned);
+extern void arcfour_encrypt(arcfour_context *, const unsigned char *, unsigned,
+			    unsigned char *);
+#define arcfour_decrypt arcfour_encrypt
+
+#endif /* _ARCFOUR_H */
diff -Nur linux-2.6.2.org/drivers/net/ppp_generic.c linux-2.6.2/drivers/net/ppp_generic.c
--- linux-2.6.2.org/drivers/net/ppp_generic.c	2004-02-04 03:44:44.000000000 +0000
+++ linux-2.6.2/drivers/net/ppp_generic.c	2004-02-05 10:33:41.000000000 +0000
@@ -104,6 +104,7 @@
 	spinlock_t	rlock;		/* lock for receive side 58 */
 	spinlock_t	wlock;		/* lock for transmit side 5c */
 	int		mru;		/* max receive unit 60 */
+	int		mru_alloc;	/* MAX(1500,MRU) for dev_alloc_skb() */
 	unsigned int	flags;		/* control bits 64 */
 	unsigned int	xstate;		/* transmit state bits 68 */
 	unsigned int	rstate;		/* receive state bits 6c */
@@ -131,6 +132,7 @@
 	struct sock_fprog pass_filter;	/* filter for packets to pass */
 	struct sock_fprog active_filter;/* filter for pkts to reset idle */
 #endif /* CONFIG_PPP_FILTER */
+	int		xpad;		/* ECP or CCP (MPPE) transmit padding */
 };
 
 /*
@@ -568,7 +570,9 @@
 	case PPPIOCSMRU:
 		if (get_user(val, (int *) arg))
 			break;
-		ppp->mru = val;
+		ppp->mru_alloc = ppp->mru = val;
+		if (ppp->mru_alloc < PPP_MRU)
+		    ppp->mru_alloc = PPP_MRU;	/* increase for broken peers */
 		err = 0;
 		break;
 
@@ -1045,8 +1049,8 @@
 	/* try to do packet compression */
 	if ((ppp->xstate & SC_COMP_RUN) && ppp->xc_state != 0
 	    && proto != PPP_LCP && proto != PPP_CCP) {
-		new_skb = alloc_skb(ppp->dev->mtu + ppp->dev->hard_header_len,
-				    GFP_ATOMIC);
+		new_skb = alloc_skb(ppp->dev->mtu + ppp->dev->hard_header_len
+				    + ppp->xpad, GFP_ATOMIC);
 		if (new_skb == 0) {
 			printk(KERN_ERR "PPP: no memory (comp pkt)\n");
 			goto drop;
@@ -1058,15 +1062,28 @@
 		/* compressor still expects A/C bytes in hdr */
 		len = ppp->xcomp->compress(ppp->xc_state, skb->data - 2,
 					   new_skb->data, skb->len + 2,
-					   ppp->dev->mtu + PPP_HDRLEN);
+					   ppp->dev->mtu + ppp->xpad
+					   + PPP_HDRLEN);
 		if (len > 0 && (ppp->flags & SC_CCP_UP)) {
 			kfree_skb(skb);
 			skb = new_skb;
 			skb_put(skb, len);
 			skb_pull(skb, 2);	/* pull off A/C bytes */
-		} else {
+		} else if (len == 0) {
 			/* didn't compress, or CCP not up yet */
 			kfree_skb(new_skb);
+		} else {
+			/*
+			 * (len < 0)
+			 * MPPE requires that we do not send unencrypted
+			 * frames.  The compressor will return -1 if we
+			 * should drop the frame.  We cannot simply test
+			 * the compress_proto because MPPE and MPPC share
+			 * the same number.
+			 */
+			printk(KERN_ERR "ppp: compressor dropped pkt\n");
+			kfree_skb(new_skb);
+			goto drop;
 		}
 	}
 
@@ -1571,14 +1588,15 @@
 		goto err;
 
 	if (proto == PPP_COMP) {
-		ns = dev_alloc_skb(ppp->mru + PPP_HDRLEN);
+		ns = dev_alloc_skb(ppp->mru_alloc + PPP_HDRLEN);
 		if (ns == 0) {
 			printk(KERN_ERR "ppp_decompress_frame: no memory\n");
 			goto err;
 		}
 		/* the decompressor still expects the A/C bytes in the hdr */
 		len = ppp->rcomp->decompress(ppp->rc_state, skb->data - 2,
-				skb->len + 2, ns->data, ppp->mru + PPP_HDRLEN);
+				skb->len + 2, ns->data,
+				ppp->mru_alloc + PPP_HDRLEN);
 		if (len < 0) {
 			/* Pass the compressed frame to pppd as an
 			   error indication. */
@@ -1736,6 +1754,7 @@
 	struct sk_buff *head, *tail;
 	struct sk_buff *skb = NULL;
 	int lost = 0, len = 0;
+	unsigned char ccp_option[CCP_MAX_OPTION_LENGTH];
 
 	if (ppp->mrru == 0)	/* do nothing until mrru is set */
 		return NULL;
@@ -1824,6 +1843,20 @@
 			++ppp->stats.rx_dropped;
 			ppp_receive_error(ppp);
 		}
+		if (ccp_option[0] == CI_MPPE)
+			/*
+			 * pppd (userland) has reduced the MTU by MPPE_PAD,
+			 * to accomodate "compressor" growth.  We must
+			 * increase the space allocated for compressor
+			 * output in ppp_send_frame() accordingly.  Note
+			 * that from a purist's view, it may be more correct
+			 * to require multilink and fragment large packets,
+			 * but that seems inefficient compared to this
+			 * little trick.
+			 */
+			ppp->xpad = MPPE_PAD;
+		else
+			ppp->xpad = 0;
 
 		if (head != tail)
 			/* copy to a single skb */
@@ -2290,6 +2323,7 @@
 	/* Initialize the new ppp unit */
 	ppp->file.index = unit;
 	ppp->mru = PPP_MRU;
+	ppp->mru_alloc = PPP_MRU;
 	init_ppp_file(&ppp->file, INTERFACE);
 	ppp->file.hdrlen = PPP_HDRLEN - 2;	/* don't count proto bytes */
 	for (i = 0; i < NUM_NP; ++i)
diff -Nur linux-2.6.2.org/drivers/net/ppp_mppe_compress.c linux-2.6.2/drivers/net/ppp_mppe_compress.c
--- linux-2.6.2.org/drivers/net/ppp_mppe_compress.c	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.2/drivers/net/ppp_mppe_compress.c	2003-03-06 23:55:15.000000000 +0000
@@ -0,0 +1,621 @@
+/*
+ *  ==FILEVERSION 20020521==
+ *
+ * ppp_mppe_compress.c - interface MPPE to the PPP code.
+ * This version is for use with Linux kernel 2.2.19+ and 2.4.x.
+ *
+ * By Frank Cusack <frank@google.com>.
+ * Copyright (c) 2002 Google, Inc.
+ * All rights reserved.
+ *
+ * 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.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include <linux/ppp_defs.h>
+#include <linux/ppp-comp.h>
+
+#include "arcfour.h"
+#include "sha1.h"
+
+/*
+ * State for an MPPE (de)compressor.
+ */
+typedef struct ppp_mppe_state {
+    unsigned char	master_key[MPPE_MAX_KEY_LEN];
+    unsigned char	session_key[MPPE_MAX_KEY_LEN];
+    arcfour_context	arcfour_context; /* encryption state */
+    unsigned		keylen;		/* key length in bytes             */
+					/* NB: 128-bit == 16, 40-bit == 8! */
+					/* If we want to support 56-bit,   */
+					/* the unit has to change to bits  */
+    unsigned char	bits;		/* MPPE control bits */
+    unsigned		ccount;		/* 12-bit coherency count (seqno)  */
+    unsigned		stateful;	/* stateful mode flag */
+    int			discard;	/* stateful mode packet loss flag */
+    int			sanity_errors;	/* take down LCP if too many */
+    int			unit;
+    int			debug;
+    struct compstat	stats;
+} ppp_mppe_state;
+
+/* ppp_mppe_state.bits definitions */
+#define MPPE_BIT_A	0x80	/* Encryption table were (re)inititalized */
+#define MPPE_BIT_B	0x40	/* MPPC only (not implemented) */
+#define MPPE_BIT_C	0x20	/* MPPC only (not implemented) */
+#define MPPE_BIT_D	0x10	/* This is an encrypted frame */
+
+#define MPPE_BIT_FLUSHED	MPPE_BIT_A
+#define MPPE_BIT_ENCRYPTED	MPPE_BIT_D
+
+#define MPPE_BITS(p) ((p)[4] & 0xf0)
+#define MPPE_CCOUNT(p) ((((p)[4] & 0x0f) << 8) + (p)[5])
+#define MPPE_CCOUNT_SPACE 0x1000	/* The size of the ccount space */
+
+#define MPPE_OVHD	2		/* MPPE overhead/packet */
+#define SANITY_MAX	1600		/* Max bogon factor we will tolerate */
+
+static void	GetNewKeyFromSHA __P((unsigned char *StartKey,
+				      unsigned char *SessionKey,
+				      unsigned SessionKeyLength,
+				      unsigned char *InterimKey));
+static void	mppe_rekey __P((ppp_mppe_state *state, int));
+static void	*mppe_alloc __P((unsigned char *options, int optlen));
+static void	mppe_free __P((void *state));
+static int	mppe_init __P((void *state, unsigned char *options,
+			       int optlen, int unit, int debug, const char *));
+static int	mppe_comp_init __P((void *state, unsigned char *options,
+				    int optlen,
+				    int unit, int hdrlen, int debug));
+static int	mppe_decomp_init __P((void *state, unsigned char *options,
+				      int optlen, int unit,
+				      int hdrlen, int mru, int debug));
+static int	mppe_compress __P((void *state, unsigned char *ibuf,
+				   unsigned char *obuf,
+				   int isize, int osize));
+static void	mppe_incomp __P((void *state, unsigned char *ibuf, int icnt));
+static int	mppe_decompress __P((void *state, unsigned char *ibuf,
+				     int isize, unsigned char *obuf,int osize));
+static void	mppe_comp_reset __P((void *state));
+static void	mppe_decomp_reset __P((void *state));
+static void	mppe_comp_stats __P((void *state, struct compstat *stats));
+
+
+/*
+ * Key Derivation, from RFC 3078, RFC 3079.
+ * Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
+ */
+static void
+GetNewKeyFromSHA(unsigned char *MasterKey, unsigned char *SessionKey,
+		 unsigned SessionKeyLength, unsigned char *InterimKey)
+{
+    SHA1_CTX Context;
+    unsigned char Digest[SHA1_SIGNATURE_SIZE];
+
+    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 };
+    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 };
+
+    /* assert(SessionKeyLength <= SHA1_SIGNATURE_SIZE); */
+
+    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);
+}
+
+/*
+ * Perform the MPPE rekey algorithm, from RFC 3078, sec. 7.3.
+ * Well, not what's written there, but rather what they meant.
+ */
+static void
+mppe_rekey(ppp_mppe_state *state, int initial_key)
+{
+    unsigned char InterimKey[MPPE_MAX_KEY_LEN];
+
+    GetNewKeyFromSHA(state->master_key, state->session_key,
+		     state->keylen, InterimKey);
+    if (!initial_key) {
+	arcfour_setkey(&state->arcfour_context, InterimKey, state->keylen);
+	arcfour_encrypt(&state->arcfour_context, InterimKey, state->keylen,
+			state->session_key);
+    } else {
+	memcpy(state->session_key, InterimKey, state->keylen);
+    }
+    if (state->keylen == 8) {
+	/* See RFC 3078 */
+	state->session_key[0] = 0xd1;
+	state->session_key[1] = 0x26;
+	state->session_key[2] = 0x9e;
+    }
+    arcfour_setkey(&state->arcfour_context, state->session_key, state->keylen);
+}
+
+
+/*
+ * Allocate space for a (de)compressor.
+ */
+static void *
+mppe_alloc(unsigned char *options, int optlen)
+{
+    ppp_mppe_state *state;
+
+    if (optlen != CILEN_MPPE + sizeof(state->master_key)
+	|| options[0] != CI_MPPE
+	|| options[1] != CILEN_MPPE)
+	return NULL;
+
+    state = (ppp_mppe_state *) kmalloc(sizeof(*state), GFP_KERNEL);
+    if (state == NULL)
+	return NULL;
+
+    MOD_INC_USE_COUNT;
+    memset(state, 0, sizeof(*state));
+
+    /* Save keys. */
+    memcpy(state->master_key, &options[CILEN_MPPE], sizeof(state->master_key));
+    memcpy(state->session_key, state->master_key, sizeof(state->master_key));
+    /*
+     * We defer initial key generation until mppe_init(), as mppe_alloc()
+     * is called frequently during negotiation.
+     */
+
+    return (void *) state;
+}
+
+/*
+ * Deallocate space for a (de)compressor.
+ */
+static void
+mppe_free(void *arg)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+    if (state) {
+	kfree(state);
+	MOD_DEC_USE_COUNT;
+    }
+}
+
+
+/* 
+ * Initialize (de)compressor state.
+ */
+static int
+mppe_init(void *arg, unsigned char *options, int optlen, int unit, int debug,
+	  const char *debugstr)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+    unsigned char mppe_opts;
+
+    if (optlen != CILEN_MPPE
+	|| options[0] != CI_MPPE
+	|| options[1] != CILEN_MPPE)
+	return 0;
+
+    MPPE_CI_TO_OPTS(&options[2], mppe_opts);
+    if (mppe_opts & MPPE_OPT_128)
+	state->keylen = 16;
+    else if (mppe_opts & MPPE_OPT_40)
+	state->keylen = 8;
+    else {
+	printk(KERN_WARNING "%s[%d]: unknown key length\n", debugstr, unit);
+	return 0;
+    }
+    if (mppe_opts & MPPE_OPT_STATEFUL)
+	state->stateful = 1;
+
+    /* Generate the initial session key. */
+    mppe_rekey(state, 1);
+
+    if (debug) {
+	int i;
+	char mkey[sizeof(state->master_key) * 2 + 1];
+	char skey[sizeof(state->session_key) * 2 + 1];
+
+	printk(KERN_DEBUG "%s[%d]: initialized with %d-bit %s mode\n", debugstr,
+	       unit, (state->keylen == 16)? 128: 40,
+	       (state->stateful)? "stateful": "stateless");
+
+	for (i = 0; i < sizeof(state->master_key); i++)
+	    sprintf(mkey + i * 2, "%.2x", state->master_key[i]);
+	for (i = 0; i < sizeof(state->session_key); i++)
+	    sprintf(skey + i * 2, "%.2x", state->session_key[i]);
+	printk(KERN_DEBUG "%s[%d]: keys: master: %s initial session: %s\n",
+	       debugstr, unit, mkey, skey);
+    }
+
+    /*
+     * Initialize the coherency count.  The initial value is not specified
+     * in RFC 3078, but we can make a reasonable assumption that it will
+     * start at 0.  Setting it to the max here makes the comp/decomp code
+     * do the right thing (determined through experiment).
+     */
+    state->ccount = MPPE_CCOUNT_SPACE - 1;
+
+    /*
+     * Note that even though we have initialized the key table, we don't
+     * set the FLUSHED bit.  This is contrary to RFC 3078, sec. 3.1.
+     */
+    state->bits = MPPE_BIT_ENCRYPTED;
+
+    state->unit  = unit;
+    state->debug = debug;
+
+    return 1;
+}
+
+
+
+static int
+mppe_comp_init(void *arg, unsigned char *options, int optlen, int unit,
+	       int hdrlen, int debug)
+{
+    /* ARGSUSED */
+    return mppe_init(arg, options, optlen, unit, debug, "mppe_comp_init");
+}
+
+/*
+ * We received a CCP Reset-Request (actually, we are sending a Reset-Ack),
+ * tell the compressor to rekey.  Note that we MUST NOT rekey for
+ * every CCP Reset-Request; we only rekey on the next xmit packet.
+ * We might get multiple CCP Reset-Requests if our CCP Reset-Ack is lost.
+ * So, rekeying for every CCP Reset-Request is broken as the peer will not
+ * know how many times we've rekeyed.  (If we rekey and THEN get another
+ * CCP Reset-Request, we must rekey again.)
+ */
+static void
+mppe_comp_reset(void *arg)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+    state->bits |= MPPE_BIT_FLUSHED;
+}
+
+/*
+ * Compress (encrypt) a packet.
+ * It's strange to call this a compressor, since the output is always
+ * MPPE_OVHD + 2 bytes larger than the input.
+ */
+int
+mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
+	      int isize, int osize)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+    int proto;
+
+    /*
+     * Check that the protocol is in the range we handle.
+     */
+    proto = PPP_PROTOCOL(ibuf);
+    if (proto < 0x0021 || proto > 0x00fa)
+	return 0;
+
+    /* Make sure we have enough room to generate an encrypted packet. */
+    if (osize < isize + MPPE_OVHD + 2) {
+	/* Drop the packet if we should encrypt it, but can't. */
+	printk(KERN_DEBUG "mppe_compress[%d]: osize too small! "
+	       "(have: %d need: %d)\n", state->unit,
+	       osize, osize + MPPE_OVHD + 2);
+	return -1;
+    }
+
+    osize = isize + MPPE_OVHD + 2;
+
+    /*
+     * Copy over the PPP header and set control bits.
+     */
+    obuf[0] = PPP_ADDRESS(ibuf);
+    obuf[1] = PPP_CONTROL(ibuf);
+    obuf[2] = PPP_COMP >> 8;		/* isize + MPPE_OVHD + 1 */
+    obuf[3] = PPP_COMP;			/* isize + MPPE_OVHD + 2 */
+    obuf += PPP_HDRLEN;
+
+    state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
+    if (state->debug >= 7)
+	printk(KERN_DEBUG "mppe_compress[%d]: ccount %d\n", state->unit,
+	       state->ccount);
+    obuf[0] = state->ccount >> 8;
+    obuf[1] = state->ccount & 0xff;
+
+    if (!state->stateful ||			/* stateless mode     */
+	((state->ccount & 0xff) == 0xff) ||	/* "flag" packet      */
+	(state->bits & MPPE_BIT_FLUSHED)) {	/* CCP Reset-Request  */
+	/* We must rekey */
+	if (state->debug && state->stateful)
+	    printk(KERN_DEBUG "mppe_compress[%d]: rekeying\n", state->unit);
+	mppe_rekey(state, 0);
+	state->bits |= MPPE_BIT_FLUSHED;
+    }
+    obuf[0] |= state->bits;
+    state->bits &= ~MPPE_BIT_FLUSHED;	/* reset for next xmit */
+
+    obuf  += MPPE_OVHD;
+    ibuf  += 2;	/* skip to proto field */
+    isize -= 2;
+
+    /* Encrypt packet */
+    arcfour_encrypt(&state->arcfour_context, ibuf, isize, obuf);
+
+    state->stats.unc_bytes += isize;
+    state->stats.unc_packets++;
+    state->stats.comp_bytes += osize;
+    state->stats.comp_packets++;
+
+    return osize;
+}
+
+/*
+ * Since every frame grows by MPPE_OVHD + 2 bytes, this is always going
+ * to look bad ... and the longer the link is up the worse it will get.
+ */
+static void
+mppe_comp_stats(void *arg, struct compstat *stats)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+    *stats = state->stats;
+}
+
+
+static int
+mppe_decomp_init(void *arg, unsigned char *options, int optlen, int unit,
+		 int hdrlen, int mru, int debug)
+{
+    /* ARGSUSED */
+    return mppe_init(arg, options, optlen, unit, debug, "mppe_decomp_init");
+}
+
+/*
+ * We received a CCP Reset-Ack.  Just ignore it.
+ */
+static void
+mppe_decomp_reset(void *arg)
+{
+    /* ARGSUSED */
+    return;
+}
+
+/*
+ * Decompress (decrypt) an MPPE packet.
+ */
+int
+mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
+		int osize)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+    unsigned ccount;
+    int flushed = MPPE_BITS(ibuf) & MPPE_BIT_FLUSHED;
+    int sanity = 0;
+
+    if (isize <= PPP_HDRLEN + MPPE_OVHD) {
+	if (state->debug)
+	    printk(KERN_DEBUG "mppe_decompress[%d]: short pkt (%d)\n",
+		   state->unit, isize);
+	return DECOMP_ERROR;
+    }
+
+    /* Make sure we have enough room to decrypt the packet. */
+    if (osize < isize - MPPE_OVHD - 2) {
+	printk(KERN_DEBUG "mppe_decompress[%d]: osize too small! "
+	       "(have: %d need: %d)\n", state->unit,
+	       osize, isize - MPPE_OVHD - 2);
+	return DECOMP_ERROR;
+    }
+    osize = isize - MPPE_OVHD - 2;
+
+    ccount = MPPE_CCOUNT(ibuf);
+    if (state->debug >= 7)
+	printk(KERN_DEBUG "mppe_decompress[%d]: ccount %d\n", state->unit,
+	       ccount);
+
+    /* sanity checks -- terminate with extreme prejudice */
+    if (!(MPPE_BITS(ibuf) & MPPE_BIT_ENCRYPTED)) {
+	printk(KERN_DEBUG "mppe_decompress[%d]: ENCRYPTED bit not set!\n",
+	       state->unit);
+	state->sanity_errors += 100;
+	sanity = 1;
+    }
+    if (!state->stateful && !flushed) {
+	printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set in "
+	       "stateless mode!\n", state->unit);
+	state->sanity_errors += 100;
+	sanity = 1;
+    }
+    if (state->stateful && ((ccount & 0xff) == 0xff) && !flushed) {
+	printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set on "
+	       "flag packet!\n", state->unit);
+	state->sanity_errors += 100;
+	sanity = 1;
+    }
+
+    if (sanity) {
+	if (state->sanity_errors < SANITY_MAX)
+	    return DECOMP_ERROR;
+	else
+	    /*
+	     * Take LCP down if the peer is sending too many bogons.
+	     * We don't want to do this for a single or just a few
+	     * instances since it could just be due to packet corruption.
+	     */
+	    return DECOMP_FATALERROR;
+    }
+
+    /*
+     * Check the coherency count.
+     */
+
+    if (!state->stateful) {
+	/* RFC 3078, sec 8.1.  Rekey for every packet. */
+	while (state->ccount != ccount) {
+	    mppe_rekey(state, 0);
+	    state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
+	}
+    } else {
+	/* RFC 3078, sec 8.2. */
+	if (!state->discard) {
+	    /* normal state */
+	    state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
+	    if (ccount != state->ccount) {
+		/*
+		 * (ccount > state->ccount)
+		 * Packet loss detected, enter the discard state.
+		 * Signal the peer to rekey (by sending a CCP Reset-Request).
+		 */
+		state->discard = 1;
+		return DECOMP_ERROR;
+	    }
+	} else {
+	    /* discard state */
+	   if (!flushed) {
+		/* ccp.c will be silent (no additional CCP Reset-Requests). */
+		return DECOMP_ERROR;
+	    } else {
+		/* Rekey for every missed "flag" packet. */
+		while ((ccount & ~0xff) != (state->ccount & ~0xff)) {
+		    mppe_rekey(state, 0);
+		    state->ccount = (state->ccount + 256) % MPPE_CCOUNT_SPACE;
+		}
+
+		/* reset */
+		state->discard = 0;
+		state->ccount = ccount;
+		/*
+		 * Another problem with RFC 3078 here.  It implies that the
+		 * peer need not send a Reset-Ack packet.  But RFC 1962
+		 * requires it.  Hopefully, M$ does send a Reset-Ack; even
+		 * though it isn't required for MPPE synchronization, it is
+		 * required to reset CCP state.
+		 */
+	    }
+	}
+	if (flushed)
+	    mppe_rekey(state, 0);
+    }
+
+    /*
+     * Fill in the first part of the PPP header.  The protocol field
+     * comes from the decrypted data.
+     */
+    obuf[0] = PPP_ADDRESS(ibuf);	/* +1 */
+    obuf[1] = PPP_CONTROL(ibuf);	/* +1 */
+    obuf  += 2;
+    ibuf  += PPP_HDRLEN + MPPE_OVHD;
+    isize -= PPP_HDRLEN + MPPE_OVHD;	/* -6 */
+					/* net osize: isize-4 */
+
+    /* And finally, decrypt the packet. */
+    arcfour_decrypt(&state->arcfour_context, ibuf, isize, obuf);
+
+    state->stats.unc_bytes += osize;
+    state->stats.unc_packets++;
+    state->stats.comp_bytes += isize;
+    state->stats.comp_packets++;
+
+    /* good packet credit */
+    state->sanity_errors >>= 1;
+
+    return osize;
+}
+
+/*
+ * Incompressible data has arrived (this should never happen!).
+ * We should probably drop the link if the protocol is in the range
+ * of what should be encrypted.  At the least, we should drop this
+ * packet.  (How to do this?)
+ */
+static void
+mppe_incomp(void *arg, unsigned char *ibuf, int icnt)
+{
+    ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+    if (state->debug &&
+	(PPP_PROTOCOL(ibuf) >= 0x0021 && PPP_PROTOCOL(ibuf) <= 0x00fa))
+	printk(KERN_DEBUG "mppe_incomp[%d]: incompressible (unencrypted) data! "
+	       "(proto %04x)\n", state->unit, PPP_PROTOCOL(ibuf));
+
+    state->stats.inc_bytes += icnt;
+    state->stats.inc_packets++;
+    state->stats.unc_bytes += icnt;
+    state->stats.unc_packets++;
+}
+
+/*************************************************************
+ * Module interface table
+ *************************************************************/
+
+/* These are in ppp.c (2.2.x) or ppp_generic.c (2.4.x) */
+extern int  ppp_register_compressor   (struct compressor *cp);
+extern void ppp_unregister_compressor (struct compressor *cp);
+
+/*
+ * Procedures exported to if_ppp.c.
+ */
+struct compressor ppp_mppe = {
+    CI_MPPE,		/* compress_proto */
+    mppe_alloc,		/* comp_alloc */
+    mppe_free,		/* comp_free */
+    mppe_comp_init,	/* comp_init */
+    mppe_comp_reset,	/* comp_reset */
+    mppe_compress,	/* compress */
+    mppe_comp_stats,	/* comp_stat */
+    mppe_alloc,		/* decomp_alloc */
+    mppe_free,		/* decomp_free */
+    mppe_decomp_init,	/* decomp_init */
+    mppe_decomp_reset,	/* decomp_reset */
+    mppe_decompress,	/* decompress */
+    mppe_incomp,	/* incomp */
+    mppe_comp_stats,	/* decomp_stat */
+};
+
+/* 2.2 compatibility defines */
+#ifndef __init
+#define __init
+#endif
+#ifndef __exit
+#define __exit
+#endif
+#ifndef MODULE_LICENSE
+#define MODULE_LICENSE(license)
+#endif
+
+int __init
+ppp_mppe_init(void)
+{  
+    int answer = ppp_register_compressor(&ppp_mppe);
+
+    if (answer == 0)
+	printk(KERN_INFO "PPP MPPE Compression module registered\n");
+    return answer;
+}
+
+void __exit
+ppp_mppe_cleanup(void)
+{
+    ppp_unregister_compressor(&ppp_mppe);
+}
+
+module_init(ppp_mppe_init);
+module_exit(ppp_mppe_cleanup);
+MODULE_LICENSE("BSD without advertisement clause");
diff -Nur linux-2.6.2.org/drivers/net/sha1.c linux-2.6.2/drivers/net/sha1.c
--- linux-2.6.2.org/drivers/net/sha1.c	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.2/drivers/net/sha1.c	2003-07-07 02:25:13.000000000 +0000
@@ -0,0 +1,185 @@
+/*
+ * ftp://ftp.funet.fi/pub/crypt/hash/sha/sha1.c
+ * 
+ * SHA-1 in C
+ * By Steve Reid <steve@edmweb.com>
+ * 100% Public Domain
+ * 
+ * Test Vectors (from FIPS PUB 180-1)
+ * "abc"
+ * A9993E36 4706816A BA3E2571 7850C26C 9CD0D89D
+ * "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
+ * 84983E44 1C3BD26E BAAE4AA1 F95129E5 E54670F1
+ * A million repetitions of "a"
+ * 34AA973C D4C4DAA4 F61EEB2B DBAD2731 6534016F
+ */
+
+/* #define SHA1HANDSOFF * Copies data before messing with it. */
+
+#if defined(__linux__)
+#include <asm/byteorder.h>
+#include <linux/string.h>
+#elif defined(__solaris__)
+#include <sys/isa_defs.h>
+#include <sys/ddi.h>
+#include <sys/sunddi.h>
+#define memcpy(d, s, c) bcopy(s, d, c)
+#define memset(d, b, c) bzero(d, c)
+#endif
+
+#include "sha1.h"
+
+static void SHA1_Transform(unsigned long[5], const unsigned char[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(unsigned long state[5], const unsigned char buffer[64])
+{
+    unsigned long a, b, c, d, e;
+    typedef union {
+	unsigned char c[64];
+	unsigned long l[16];
+    } CHAR64LONG16;
+    CHAR64LONG16 *block;
+
+#ifdef SHA1HANDSOFF
+    static unsigned char 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 */
+    a = b = c = d = e = 0;
+}
+
+
+/* SHA1Init - Initialize new context */
+
+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. */
+
+void
+SHA1_Update(SHA1_CTX *context, const unsigned char *data, unsigned int len)
+{
+    unsigned int 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. */
+
+void
+SHA1_Final(unsigned char digest[20], SHA1_CTX *context)
+{
+    unsigned long i, j;
+    unsigned char finalcount[8];
+
+    for (i = 0; i < 8; i++) {
+        finalcount[i] = (unsigned char)((context->count[(i >= 4 ? 0 : 1)]
+         >> ((3-(i & 3)) * 8) ) & 255);  /* Endian independent */
+    }
+    SHA1_Update(context, (unsigned char *) "\200", 1);
+    while ((context->count[0] & 504) != 448) {
+	SHA1_Update(context, (unsigned char *) "\0", 1);
+    }
+    SHA1_Update(context, finalcount, 8);  /* Should cause a SHA1Transform() */
+    for (i = 0; i < 20; i++) {
+	digest[i] = (unsigned char)
+		     ((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
+}
+
diff -Nur linux-2.6.2.org/drivers/net/sha1.h linux-2.6.2/drivers/net/sha1.h
--- linux-2.6.2.org/drivers/net/sha1.h	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.2/drivers/net/sha1.h	2002-04-02 07:01:37.000000000 +0000
@@ -0,0 +1,18 @@
+/* sha1.h */
+
+#ifndef _SHA1_H
+#define _SHA1_H
+
+typedef struct {
+    unsigned long state[5];
+    unsigned long count[2];
+    unsigned char buffer[64];
+} SHA1_CTX;
+
+#define SHA1_SIGNATURE_SIZE 20
+
+extern void SHA1_Init(SHA1_CTX *);
+extern void SHA1_Update(SHA1_CTX *, const unsigned char *, unsigned int);
+extern void SHA1_Final(unsigned char[SHA1_SIGNATURE_SIZE], SHA1_CTX *);
+
+#endif /* _SHA1_H */
diff -Nur linux-2.6.2.org/include/linux/ppp-comp.h linux-2.6.2/include/linux/ppp-comp.h
--- linux-2.6.2.org/include/linux/ppp-comp.h	2004-02-04 03:43:03.000000000 +0000
+++ linux-2.6.2/include/linux/ppp-comp.h	2004-02-05 09:48:34.000000000 +0000
@@ -191,6 +191,100 @@
 #define DEFLATE_CHK_SEQUENCE	0
 
 /*
+ * Definitions for MPPE.
+ */
+
+#define CI_MPPE			18	/* config option for MPPE */
+#define CILEN_MPPE		6	/* length of config option */
+
+#define MPPE_PAD		4	/* MPPE growth per frame */
+#define MPPE_MAX_KEY_LEN	16	/* largest key length (128-bit) */
+
+/* option bits for ccp_options.mppe */
+#define MPPE_OPT_40		0x01	/* 40 bit */
+#define MPPE_OPT_128		0x02	/* 128 bit */
+#define MPPE_OPT_STATEFUL	0x04	/* stateful mode */
+/* unsupported opts */
+#define MPPE_OPT_56		0x08	/* 56 bit */
+#define MPPE_OPT_MPPC		0x10	/* MPPC compression */
+#define MPPE_OPT_D		0x20	/* Unknown */
+#define MPPE_OPT_UNSUPPORTED (MPPE_OPT_56|MPPE_OPT_MPPC|MPPE_OPT_D)
+#define MPPE_OPT_UNKNOWN	0x40	/* Bits !defined in RFC 3078 were set */
+
+/*
+ * This is not nice ... the alternative is a bitfield struct though.
+ * And unfortunately, we cannot share the same bits for the option
+ * names above since C and H are the same bit.  We could do a u_int32
+ * but then we have to do a htonl() all the time and/or we still need
+ * to know which octet is which.
+ */
+#define MPPE_C_BIT		0x01	/* MPPC */
+#define MPPE_D_BIT		0x10	/* Obsolete, usage unknown */
+#define MPPE_L_BIT		0x20	/* 40-bit */
+#define MPPE_S_BIT		0x40	/* 128-bit */
+#define MPPE_M_BIT		0x80	/* 56-bit, not supported */
+#define MPPE_H_BIT		0x01	/* Stateless (in a different byte) */
+
+/* Does not include H bit; used for least significant octet only. */
+#define MPPE_ALL_BITS (MPPE_D_BIT|MPPE_L_BIT|MPPE_S_BIT|MPPE_M_BIT|MPPE_H_BIT)
+
+/* Build a CI from mppe opts (see RFC 3078) */
+#define MPPE_OPTS_TO_CI(opts, ci)		\
+    do {					\
+	u_char *ptr = ci; /* u_char[4] */	\
+						\
+	/* H bit */				\
+	if (opts & MPPE_OPT_STATEFUL)		\
+	    *ptr++ = 0x0;			\
+	else					\
+	    *ptr++ = MPPE_H_BIT;		\
+	*ptr++ = 0;				\
+	*ptr++ = 0;				\
+						\
+	/* S,L bits */				\
+	*ptr = 0;				\
+	if (opts & MPPE_OPT_128)		\
+	    *ptr |= MPPE_S_BIT;			\
+	if (opts & MPPE_OPT_40)			\
+	    *ptr |= MPPE_L_BIT;			\
+	/* M,D,C bits not supported */		\
+    } while (/* CONSTCOND */ 0)
+
+/* The reverse of the above */
+#define MPPE_CI_TO_OPTS(ci, opts)		\
+    do {					\
+	u_char *ptr = ci; /* u_char[4] */	\
+						\
+	opts = 0;				\
+						\
+	/* H bit */				\
+	if (!(ptr[0] & MPPE_H_BIT))		\
+	    opts |= MPPE_OPT_STATEFUL;		\
+						\
+	/* S,L bits */				\
+	if (ptr[3] & MPPE_S_BIT)		\
+	    opts |= MPPE_OPT_128;		\
+	if (ptr[3] & MPPE_L_BIT)		\
+	    opts |= MPPE_OPT_40;		\
+						\
+	/* M,D,C bits */			\
+	if (ptr[3] & MPPE_M_BIT)		\
+	    opts |= MPPE_OPT_56;		\
+	if (ptr[3] & MPPE_D_BIT)		\
+	    opts |= MPPE_OPT_D;			\
+	if (ptr[3] & MPPE_C_BIT)		\
+	    opts |= MPPE_OPT_MPPC;		\
+						\
+	/* Other bits */			\
+	if (ptr[0] & ~MPPE_H_BIT)		\
+	    opts |= MPPE_OPT_UNKNOWN;		\
+	if (ptr[1] || ptr[2])			\
+	    opts |= MPPE_OPT_UNKNOWN;		\
+	if (ptr[3] & ~MPPE_ALL_BITS)		\
+	    opts |= MPPE_OPT_UNKNOWN;		\
+    } while (/* CONSTCOND */ 0)
+
+/*
  * Definitions for other, as yet unsupported, compression methods.
  */