netdev-afxdp: add new netdev type for AF_XDP.

The patch introduces experimental AF_XDP support for OVS netdev.
AF_XDP, the Address Family of the eXpress Data Path, is a new Linux socket
type built upon the eBPF and XDP technology.  It is aims to have comparable
performance to DPDK but cooperate better with existing kernel's networking
stack.  An AF_XDP socket receives and sends packets from an eBPF/XDP program
attached to the netdev, by-passing a couple of Linux kernel's subsystems
As a result, AF_XDP socket shows much better performance than AF_PACKET
For more details about AF_XDP, please see linux kernel's
Documentation/networking/af_xdp.rst. Note that by default, this feature is
not compiled in.

Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>

Documentation/automake.mk

@@ -10,6 +10,7 @@ DOC_SOURCE = \
 	Documentation/intro/why-ovs.rst \
 	Documentation/intro/install/index.rst \
 	Documentation/intro/install/bash-completion.rst \
+	Documentation/intro/install/afxdp.rst \
 	Documentation/intro/install/debian.rst \
 	Documentation/intro/install/documentation.rst \
 	Documentation/intro/install/distributions.rst \

Documentation/index.rst

@@ -59,6 +59,7 @@ vSwitch? Start here.
   :doc:`intro/install/windows` |
   :doc:`intro/install/xenserver` |
   :doc:`intro/install/dpdk` |
+  :doc:`intro/install/afxdp` |
   :doc:`Installation FAQs <faq/releases>`
 
 - **Tutorials:** :doc:`tutorials/faucet` |