netdev: Custom statistics.

- New get_custom_stats interface function is added to netdev. It
  allows particular netdev implementation to expose custom
  counters in dictionary format (counter name/counter value).
- New statistics are retrieved using experimenter code and
  are printed as a result to ofctl dump-ports.
- New counters are available for OpenFlow 1.4+.
- New statistics are printed to output via ofctl only if those
  are present in reply message.
- New statistics definition is added to include/openflow/intel-ext.h.
- Custom statistics are implemented only for dpdk-physical
  port type.
- DPDK-physical implementation uses xstats to collect statistics.
  Only dropped and error counters are exposed.

Co-authored-by: Ben Pfaff <blp@ovn.org>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Signed-off-by: Michal Weglicki <michalx.weglicki@intel.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

lib/netdev.c

@@ -1421,6 +1421,21 @@ netdev_get_stats(const struct netdev *netdev, struct netdev_stats *stats)
     return error;
 }
 
+/* Retrieves current device custom stats for 'netdev'. */
+int
+netdev_get_custom_stats(const struct netdev *netdev,
+                        struct netdev_custom_stats *custom_stats)
+{
+    int error;
+    memset(custom_stats, 0, sizeof *custom_stats);
+    error = (netdev->netdev_class->get_custom_stats
+             ? netdev->netdev_class->get_custom_stats(netdev, custom_stats)
+             : EOPNOTSUPP);
+
+    return error;
+}
+
+
 /* Attempts to set input rate limiting (policing) policy, such that up to
  * 'kbits_rate' kbps of traffic is accepted, with a maximum accumulative burst
  * size of 'kbits' kb. */
@@ -2376,6 +2391,18 @@ netdev_ports_flow_get(const struct dpif_class *dpif_class, struct match *match,
     return ENOENT;
 }
 
+void
+netdev_free_custom_stats_counters(struct netdev_custom_stats *custom_stats)
+{
+    if (custom_stats) {
+        if (custom_stats->counters) {
+            free(custom_stats->counters);
+            custom_stats->counters = NULL;
+            custom_stats->size = 0;
+        }
+    }
+}
+
 #ifdef __linux__
 static void
 netdev_ports_flow_init(void)