PPTP: PPP over IPv4 (Point-to-Point Tunneling Protocol)

PPP: introduce "pptp" module which implements point-to-point tunneling protocol using pppox framework
NET: introduce the "gre" module for demultiplexing GRE packets on version criteria
     (required to pptp and ip_gre may coexists)
NET: ip_gre: update to use the "gre" module

This patch introduces then pptp support to the linux kernel which
dramatically speeds up pptp vpn connections and decreases cpu usage in
comparison of existing user-space implementation
(poptop/pptpclient). There is accel-pptp project
(https://sourceforge.net/projects/accel-pptp/) to utilize this module,
it contains plugin for pppd to use pptp in client-mode and modified
pptpd (poptop) to build high-performance pptp NAS.

There was many changes from initial submitted patch, most important are:
1. using rcu instead of read-write locks
2. using static bitmap instead of dynamically allocated
3. using vmalloc for memory allocation instead of BITS_PER_LONG + __get_free_pages
4. fixed many coding style issues
Thanks to Eric Dumazet.

Signed-off-by: Dmitry Kozlov <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

MAINTAINERS

@@ -6528,6 +6528,20 @@ M:	"Maciej W. Rozycki" <[email protected]>
 S:	Maintained
 F:	drivers/serial/zs.*
 
+GRE DEMULTIPLEXER DRIVER
+M:	Dmitry Kozlov <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	net/ipv4/gre.c
+F:	include/net/gre.h
+
+PPTP DRIVER
+M:	Dmitry Kozlov <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	drivers/net/pptp.c
+W:	http://sourceforge.net/projects/accel-pptp
+
 THE REST
 M:	Linus Torvalds <[email protected]>
 L:	[email protected]

drivers/net/Kconfig

@@ -3192,6 +3192,17 @@ config PPPOE
 	  which contains instruction on how to use this driver (under 
 	  the heading "Kernel mode PPPoE").
 
+config PPTP
+	tristate "PPP over IPv4 (PPTP) (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && PPP && NET_IPGRE_DEMUX
+	help
+	  Support for PPP over IPv4.(Point-to-Point Tunneling Protocol)
+
+	  This driver requires pppd plugin to work in client mode or
+	  modified pptpd (poptop) to work in server mode.
+	  See http://accel-pptp.sourceforge.net/ for information how to
+	  utilize this module.
+
 config PPPOATM
 	tristate "PPP over ATM"
 	depends on ATM && PPP

drivers/net/Makefile

@@ -162,6 +162,7 @@ obj-$(CONFIG_PPP_BSDCOMP) += bsd_comp.o
 obj-$(CONFIG_PPP_MPPE) += ppp_mppe.o
 obj-$(CONFIG_PPPOE) += pppox.o pppoe.o
 obj-$(CONFIG_PPPOL2TP) += pppox.o
+obj-$(CONFIG_PPTP) += pppox.o pptp.o
 
 obj-$(CONFIG_SLIP) += slip.o
 obj-$(CONFIG_SLHC) += slhc.o