[PPP]: add PPP MPPE encryption module

From: Matt Domsch <Matt_Domsch@dell.com>

The patch below implements the Microsoft Point-to-Point Encryption method
as a PPP compressor/decompressor.  This is necessary for Linux clients and
servers to interoperate with Microsoft Point-to-Point Tunneling Protocol
(PPTP) servers (either Microsoft PPTP servers or the poptop project) which
use MPPE to encrypt data when creating a VPN.

This patch differs from the kernel_ppp_mppe DKMS pacakge at
pptpclient.sourceforge.net by utilizing the kernel crypto routines rather
than providing its own SHA1 and arcfour implementations.

Minor changes to ppp_generic.c try to prevent a link from disabling
compression (in our case, the encryption) after it has started using
compression (encryption).

Feedback to <pptpclient-devel@lists.sourceforge.net> please.

Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Cc: James Cameron <james.cameron@hp.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Brice Goglin <Brice.Goglin@ens-lyon.org>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 14 insertions, 2 deletions

diff --git a/include/linux/if_ppp.h b/include/linux/if_ppp.h
index 572aff7daa21..768372f07caa 100644
--- a/include/linux/if_ppp.h
+++ b/include/linux/if_ppp.h
@@ -21,7 +21,7 @@
  */
 
 /*
- *  ==FILEVERSION 20000724==
+ *  ==FILEVERSION 20050812==
  *
  *  NOTE TO MAINTAINERS:
  *     If you modify this file at all, please set the above date.
@@ -35,6 +35,8 @@
 #ifndef _IF_PPP_H_
 #define _IF_PPP_H_
 
+#include <linux/compiler.h>
+
 /*
  * Packet sizes
  */
@@ -70,7 +72,8 @@
 #define SC_LOG_RAWIN    0x00080000      /* log all chars received */
 #define SC_LOG_FLUSH    0x00100000      /* log all chars flushed */
 #define SC_SYNC         0x00200000      /* synchronous serial mode */
-#define SC_MASK         0x0f200fff      /* bits that user can change */
+#define SC_MUST_COMP    0x00400000      /* no uncompressed packets may be sent or received */
+#define SC_MASK         0x0f600fff      /* bits that user can change */
 
 /* state bits */
 #define SC_XMIT_BUSY    0x10000000      /* (used by isdn_ppp?) */
diff --git a/include/linux/ppp-comp.h b/include/linux/ppp-comp.h
index 7227e653b3be..e86a7a5cf355 100644
--- a/include/linux/ppp-comp.h
+++ b/include/linux/ppp-comp.h
@@ -111,6 +111,8 @@ struct compressor {
 
         /* Used in locking compressor modules */
         struct module *owner;
+        /* Extra skb space needed by the compressor algorithm */
+        unsigned int comp_extra;
 };
 
 /*
@@ -191,6 +193,13 @@ struct compressor {
 #define DEFLATE_CHK_SEQUENCE    0
 
 /*
+ * Definitions for MPPE.
+ */
+
+#define CI_MPPE                18      /* config option for MPPE */
+#define CILEN_MPPE              6      /* length of config option */
+
+/*
  * Definitions for other, as yet unsupported, compression methods.
  */