devices interface tests: vhosst GSO support

Add gso option in create vhost interface to support gso and checksum
offload.

Tested with the following startup options in qemu:
csum=on,gso=on,guest_csum=on,guest_tso4=on,guest_tso6=on,guest_ufo=on,
host_tso4=on,host_tso6=on,host_ufo=on

Type: feature

Change-Id: I9ba1ee33677a694c4a0dfe66e745b098995902b8
Signed-off-by: Steven Luong <sluong@cisco.com>
diff --git a/src/vnet/devices/virtio/vhost_user.api b/src/vnet/devices/virtio/vhost_user.api
index c745b3d..e08c735 100644
--- a/src/vnet/devices/virtio/vhost_user.api
+++ b/src/vnet/devices/virtio/vhost_user.api
@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-option version = "2.0.0";
+option version = "3.0.0";
 
 /** \brief vhost-user interface create request
     @param client_index - opaque cookie to identify the sender
@@ -22,6 +22,7 @@
     @param use_custom_mac - enable or disable the use of the provided hardware address
     @param disable_mrg_rxbuf - disable the use of merge receive buffers
     @param disable_indirect_desc - disable the use of indirect descriptors which driver can use
+    @param enable_gso - enable gso support (default 0)
     @param mac_address - hardware address to use if 'use_custom_mac' is set
 */
 define create_vhost_user_if
@@ -33,6 +34,7 @@
   u8 renumber;
   u8 disable_mrg_rxbuf;
   u8 disable_indirect_desc;
+  u8 enable_gso;
   u32 custom_dev_instance;
   u8 use_custom_mac;
   u8 mac_address[6];
@@ -55,6 +57,7 @@
     @param client_index - opaque cookie to identify the sender
     @param is_server - our side is socket server
     @param sock_filename - unix socket filename, used to speak with frontend
+    @param enable_gso - enable gso support (default 0)
 */
 autoreply define modify_vhost_user_if
 {
@@ -64,6 +67,7 @@
   u8 is_server;
   u8 sock_filename[256];
   u8 renumber;
+  u8 enable_gso;
   u32 custom_dev_instance;
 };