net: macvtap driver

In order to use macvlan with qemu and other tools that require
a tap file descriptor, the macvtap driver adds a small backend
with a character device with the same interface as the tun
driver, with a minimum set of features.

Macvtap interfaces are created in the same way as macvlan
interfaces using ip link, but the netif is just used as a
handle for configuration and accounting, while the data
goes through the chardev. Each macvtap interface has its
own character device, simplifying permission management
significantly over the generic tun/tap driver.

Cc: Patrick McHardy <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: David S. Miller" <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Or Gerlitz <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

drivers/net/Kconfig

@@ -90,6 +90,18 @@ config MACVLAN
  To compile this driver as a module, choose M here: the module
  will be called macvlan.
 
+config MACVTAP
+ tristate "MAC-VLAN based tap driver (EXPERIMENTAL)"
+ depends on MACVLAN
+ help
+ This adds a specialized tap character device driver that is based
+ on the MAC-VLAN network interface, called macvtap. A macvtap device
+ can be added in the same way as a macvlan device, using 'type
+ macvlan', and then be accessed through the tap user space interface.
+
+ To compile this driver as a module, choose M here: the module
+ will be called macvtap.
+
 config EQUALIZER
  tristate "EQL (serial line load balancing) support"
  ---help---

drivers/net/Makefile

@@ -169,6 +169,7 @@ obj-$(CONFIG_XEN_NETDEV_FRONTEND) += xen-netfront.o
 obj-$(CONFIG_DUMMY) += dummy.o
 obj-$(CONFIG_IFB) += ifb.o
 obj-$(CONFIG_MACVLAN) += macvlan.o
+obj-$(CONFIG_MACVTAP) += macvtap.o
 obj-$(CONFIG_DE600) += de600.o
 obj-$(CONFIG_DE620) += de620.o
 obj-$(CONFIG_LANCE) += lance.o