Openvswitch uses function from NET_IPGRE_DEMUX module.
Add Kconfig dependency to fix following compilation errors:
http://marc.info/?l=linux-netdev&m=137244035226634

CC: Jesse Gross <jesse@nicira.com>
Reported-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NPravin Shelar <pshelar@nicira.com>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Acked-by: NJesse Gross <jesse@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add gre vport implementation.  Most of gre protocol processing
is pushed to gre module. It make use of gre demultiplexer
therefore it can co-exist with linux device based gre tunnels.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Acked-by: NJesse Gross <jesse@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Open vSwitch is a multilayer Ethernet switch targeted at virtualized
environments.  In addition to supporting a variety of features
expected in a traditional hardware switch, it enables fine-grained
programmatic extension and flow-based control of the network.
This control is useful in a wide variety of applications but is
particularly important in multi-server virtualization deployments,
which are often characterized by highly dynamic endpoints and the need
to maintain logical abstractions for multiple tenants.

The Open vSwitch datapath provides an in-kernel fast path for packet
forwarding.  It is complemented by a userspace daemon, ovs-vswitchd,
which is able to accept configuration from a variety of sources and
translate it into packet processing rules.

See http://openvswitch.org for more information and userspace
utilities.
Signed-off-by: NJesse Gross <jesse@nicira.com>