interface: support configuring RSS steering queues

This patch adds the RSS steering queues set interface, and it's
implementation in DPDK device:

/* Interface to set rss queues of the interface */
typedef clib_error_t *(vnet_interface_rss_queues_set_t)
  (struct vnet_main_t * vnm, struct vnet_hw_interface_t * hi,
   clib_bitmap_t *bitmap);

This patch also introduces a command line to set the RSS queues:
  set interface rss queues <interface> <list <queue-list>>
To display the rss queues, use "show hardware-interfaces"

Below is the example to configure rss queues for interface Gig0:
vpp# set interface rss queues Gig0 list 0,2,4-7
vpp# show hardware-interfaces brief
              Name                Idx   Link  Hardware
VirtualFunctionEthernet18/1/0      1    down  VirtualFunctionEthernet18/1/0
  Link speed: unknown
  RSS queues: 0 2 4 5 6 7
local0                             0    down  local0
  Link speed: unknown
vpp#

Users can also configure the rss queues on a dpdk interface in
startup.conf:
dpdk {
    dev 0000:18:01.0 {
        rss-queues 0,2,5-7
    }
}

Type: feature

Signed-off-by: Chenmin Sun <chenmin.sun@intel.com>
Change-Id: I1835595a1c54016a84eabee9fd62ce137935385d
diff --git a/src/vnet/interface.c b/src/vnet/interface.c
index 6d5b356..18c7696 100644
--- a/src/vnet/interface.c
+++ b/src/vnet/interface.c
@@ -1692,6 +1692,42 @@
     }
 }
 
+clib_error_t *
+vnet_hw_interface_set_rss_queues (vnet_main_t * vnm,
+				  vnet_hw_interface_t * hi,
+				  clib_bitmap_t * bitmap)
+{
+  clib_error_t *error = 0;
+  vnet_device_class_t *dev_class =
+    vnet_get_device_class (vnm, hi->dev_class_index);
+
+  if (dev_class->set_rss_queues_function)
+    {
+      if (clib_bitmap_count_set_bits (bitmap) == 0)
+	{
+	  error = clib_error_return (0,
+				     "must assign at least one valid rss queue");
+	  goto done;
+	}
+
+      error = dev_class->set_rss_queues_function (vnm, hi, bitmap);
+    }
+  else
+    {
+      error = clib_error_return (0,
+				 "setting rss queues is not supported on this interface");
+    }
+
+  if (!error)
+    {
+      clib_bitmap_free (hi->rss_queues);
+      hi->rss_queues = clib_bitmap_dup (bitmap);
+    }
+
+done:
+  return error;
+}
+
 int collect_detailed_interface_stats_flag = 0;
 
 void