can-gw: add netlink based CAN routing

This patch adds a CAN Gateway/Router to route (and modify) CAN frames.

It is based on the PF_CAN core infrastructure for msg filtering and msg
sending and can optionally modify routed CAN frames on the fly.
CAN frames can *only* be routed between CAN network interfaces (one hop).
They can be modified with AND/OR/XOR/SET operations as configured by the
netlink configuration interface known e.g. from iptables. From the netlink
view this can-gw implements RTM_{NEW|DEL|GET}ROUTE for PF_CAN.

The CAN specific userspace tool to manage CAN routing entries can be found in
the CAN utils http://svn.berlios.de/wsvn/socketcan/trunk/can-utils/cangw.c
at the SocketCAN SVN on BerliOS.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/can/Kconfig

@@ -40,5 +40,16 @@ config CAN_BCM
 	  CAN messages are used on the bus (e.g. in automotive environments).
 	  To use the Broadcast Manager, use AF_CAN with protocol CAN_BCM.
 
+config CAN_GW
+	tristate "CAN Gateway/Router (with netlink configuration)"
+	depends on CAN
+	default N
+	---help---
+	  The CAN Gateway/Router is used to route (and modify) CAN frames.
+	  It is based on the PF_CAN core infrastructure for msg filtering and
+	  msg sending and can optionally modify routed CAN frames on the fly.
+	  CAN frames can be routed between CAN network interfaces (one hop).
+	  They can be modified with AND/OR/XOR/SET operations as configured
+	  by the netlink configuration interface known e.g. from iptables.
 
 source "drivers/net/can/Kconfig"

net/can/Makefile

@@ -10,3 +10,6 @@ can-raw-y		:= raw.o
 
 obj-$(CONFIG_CAN_BCM)	+= can-bcm.o
 can-bcm-y		:= bcm.o
+
+obj-$(CONFIG_CAN_GW)	+= can-gw.o
+can-gw-y		:= gw.o