l2tp: Split pppol2tp patch into separate l2tp and ppp parts

This patch splits the pppol2tp driver into separate L2TP and PPP parts
to prepare for L2TPv3 support. In L2TPv3, protocols other than PPP can
be carried, so this split creates a common L2TP core that will handle
the common L2TP bits which protocol support modules such as PPP will
use.

Note that the existing pppol2tp module is split into l2tp_core and
l2tp_ppp by this change.

There are no feature changes here. Internally, however, there are
significant changes, mostly to handle the separation of PPP-specific
data from the L2TP session and to provide hooks in the core for
modules like PPP to access.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Kconfig

@@ -3158,17 +3158,12 @@ config PPPOATM
 
 config PPPOL2TP
 	tristate "PPP over L2TP (EXPERIMENTAL)"
-	depends on EXPERIMENTAL && PPP && INET
+	depends on EXPERIMENTAL && L2TP && PPP
 	help
 	  Support for PPP-over-L2TP socket family. L2TP is a protocol
 	  used by ISPs and enterprises to tunnel PPP traffic over UDP
 	  tunnels. L2TP is replacing PPTP for VPN uses.
 
-	  This kernel component handles only L2TP data packets: a
-	  userland daemon handles L2TP the control protocol (tunnel
-	  and session setup). One such daemon is OpenL2TP
-	  (http://openl2tp.sourceforge.net/).
-
 config SLIP
 	tristate "SLIP (serial line) support"
 	---help---

include/linux/if_pppol2tp.h

@@ -2,7 +2,7 @@
  * Linux PPP over L2TP (PPPoL2TP) Socket Implementation (RFC 2661)
  *
  * This file supplies definitions required by the PPP over L2TP driver
- * (pppol2tp.c).  All version information wrt this file is located in pppol2tp.c
+ * (l2tp_ppp.c).  All version information wrt this file is located in l2tp_ppp.c
  *
  * License:
  *		This program is free software; you can redistribute it and/or

net/Kconfig

@@ -186,6 +186,7 @@ source "net/sctp/Kconfig"
 source "net/rds/Kconfig"
 source "net/tipc/Kconfig"
 source "net/atm/Kconfig"
+source "net/l2tp/Kconfig"
 source "net/802/Kconfig"
 source "net/bridge/Kconfig"
 source "net/dsa/Kconfig"

net/Makefile

@@ -40,7 +40,7 @@ obj-$(CONFIG_BT)		+= bluetooth/
 obj-$(CONFIG_SUNRPC)		+= sunrpc/
 obj-$(CONFIG_AF_RXRPC)		+= rxrpc/
 obj-$(CONFIG_ATM)		+= atm/
-obj-$(CONFIG_PPPOL2TP)		+= l2tp/
+obj-$(CONFIG_L2TP)		+= l2tp/
 obj-$(CONFIG_DECNET)		+= decnet/
 obj-$(CONFIG_ECONET)		+= econet/
 obj-$(CONFIG_PHONET)		+= phonet/

net/l2tp/Kconfig

@@ -0,0 +1,28 @@
+#
+# Layer Two Tunneling Protocol (L2TP)
+#
+
+menuconfig L2TP
+	tristate "Layer Two Tunneling Protocol (L2TP)"
+	depends on INET
+	---help---
+	  Layer Two Tunneling Protocol
+
+	  From RFC 2661 <http://www.ietf.org/rfc/rfc2661.txt>.
+
+	  L2TP facilitates the tunneling of packets across an
+	  intervening network in a way that is as transparent as
+	  possible to both end-users and applications.
+
+	  L2TP is often used to tunnel PPP traffic over IP
+	  tunnels. One IP tunnel may carry thousands of individual PPP
+	  connections. L2TP is also used as a VPN protocol, popular
+	  with home workers to connect to their offices.
+
+	  The kernel component handles only L2TP data packets: a
+	  userland daemon handles L2TP the control protocol (tunnel
+	  and session setup). One such daemon is OpenL2TP
+	  (http://openl2tp.org/).
+
+	  If you don't need L2TP, say N. To compile all L2TP code as
+	  modules, choose M here.

net/l2tp/Makefile

@@ -2,4 +2,7 @@
 # Makefile for the L2TP.
 #
 
-obj-$(CONFIG_PPPOL2TP) += pppol2tp.o
+obj-$(CONFIG_L2TP) += l2tp_core.o
+
+# Build l2tp as modules if L2TP is M
+obj-$(subst y,$(CONFIG_L2TP),$(CONFIG_PPPOL2TP)) += l2tp_ppp.o