device: Add callback for set interface rx-mode

- When the interface rx-mode is changed via CLI, the corresponding device
may want to know about it and to reset the driver. This patch is to add
the callback.

- In the function vnet_hw_interface_set_rx_mode, it appears it is missing
a line
  hw->rx_mode_by_queue[queue_id] = mode

because the function is checking if the new mode is the same as
hw->rx_mode_by_queue which is initialized to POLLING. So if the function is
called to change the mode to interrupt, it just returns without doing
anything. This is the check that I am talking about in the same function.

  if (hw->rx_mode_by_queue[queue_id] == mode)
    return 0;

Change-Id: Iaca2651c43e0ae3fda6fd8dc128e247b0851cc65
Signed-off-by: Steven <sluong@cisco.com>
diff --git a/src/vnet/interface.h b/src/vnet/interface.h
index 2344348..1c98555 100644
--- a/src/vnet/interface.h
+++ b/src/vnet/interface.h
@@ -48,6 +48,15 @@
 struct vnet_sw_interface_t;
 struct ip46_address_t;
 
+typedef enum
+{
+  VNET_HW_INTERFACE_RX_MODE_UNKNOWN,
+  VNET_HW_INTERFACE_RX_MODE_POLLING,
+  VNET_HW_INTERFACE_RX_MODE_INTERRUPT,
+  VNET_HW_INTERFACE_RX_MODE_ADAPTIVE,
+  VNET_HW_INTERFACE_NUM_RX_MODES,
+} vnet_hw_interface_rx_mode;
+
 /* Interface up/down callback. */
 typedef clib_error_t *(vnet_interface_function_t)
   (struct vnet_main_t * vnm, u32 if_index, u32 flags);
@@ -61,6 +70,11 @@
 typedef clib_error_t *(vnet_interface_set_mac_address_function_t)
   (struct vnet_hw_interface_t * hi, char *address);
 
+/* Interface set rx mode callback. */
+typedef clib_error_t *(vnet_interface_set_rx_mode_function_t)
+  (struct vnet_main_t * vnm, u32 if_index, u32 queue_id,
+   vnet_hw_interface_rx_mode mode);
+
 typedef enum vnet_interface_function_priority_t_
 {
   VNET_ITF_FUNC_PRIORITY_LOW,
@@ -134,6 +148,9 @@
   /* Function to call when sub-interface is added/deleted */
   vnet_subif_add_del_function_t *subif_add_del_function;
 
+  /* Function to call interface rx mode is changed */
+  vnet_interface_set_rx_mode_function_t *rx_mode_change_function;
+
   /* Redistribute flag changes/existence of this interface class. */
   u32 redistribute;
 
@@ -492,15 +509,6 @@
   VNET_SW_INTERFACE_TYPE_SUB,
 } vnet_sw_interface_type_t;
 
-typedef enum
-{
-  VNET_HW_INTERFACE_RX_MODE_UNKNOWN,
-  VNET_HW_INTERFACE_RX_MODE_POLLING,
-  VNET_HW_INTERFACE_RX_MODE_INTERRUPT,
-  VNET_HW_INTERFACE_RX_MODE_ADAPTIVE,
-  VNET_HW_INTERFACE_NUM_RX_MODES,
-} vnet_hw_interface_rx_mode;
-
 typedef struct
 {
   /*