* Patching VM kernel to use ASF fastpath

  Virtio-IPsec-LA uses fastpath software in the guest kernel which can handle forwarding
  and IPsec functions.  To enable offloading these functions, it inserts the following hooks
  in Linux
    - To capture RX packets and TX packets sent directly to the driver, 2 hooks are inserted in
	  virtio-net driver
	- To offload allowed flows and learn applicable route info and SAs, hooks are inserted in
      Linux iptables, conntrack, ip_route and xfrm.

  To add these hooks, apply the patch (g_ipsec_la/src/guest/kernel/as-fastpath.patch) to the kernel
  tree.  This patch is derived from linux version 4.1.8.  It may be necessary to apply this patch
  manually.
  
  After applying the patch, enable the following options in Linux configuration using menuconfig
    - Device Drivers / Network device support / Application Specific FastPath

  Rebuild kernel
 
* Build procedure

  # Edit g_ipsec_la/build.sh to enter your build env and arch
    - Define ARCH - not required if building natively
    - Define CROSS_COMPILE with the prefix for cross-build tools
    - Update PATH to point to cross-build tools
    -# Define KERNEL_PATH for the target kernel header files

  # To build the guest kernel modules, use the following command
    - ./build.sh

  # Modules generated (in the loading order)
    - g_ipsec_la/bin/virtio_ipsec.ko            look-aside virtio-ipsec driver
    - g_ipsec_la/bin/min/asf.ko                 port-2-port forwarding driver
    - g_ipsec_la/bin/min/asfctrl.ko             linux interface for port-2-port forward
    - g_ipsec_la/bin/min/asfipsec.ko            ipsec driver
    - g_ipsec_la/bin/min/asfipsec_ctrl.ko       linux interface for ipsec driver

  # To clean the workspace, use the following command
    - ./build.sh clean