ip-neighbor: ARP and ND stats per-interface.

Type: feature

stats of the like from:
  https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-arp-yang-model-03#section-4

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: Icb1bf4f6f7e6ccc2f44b0008d4774b61cae96184
diff --git a/src/vnet/ip6-nd/ip6_nd_inline.h b/src/vnet/ip6-nd/ip6_nd_inline.h
index ad0c3a3..5e8b9d6 100644
--- a/src/vnet/ip6-nd/ip6_nd_inline.h
+++ b/src/vnet/ip6-nd/ip6_nd_inline.h
@@ -22,6 +22,7 @@
 #include <vnet/ethernet/ethernet.h>
 #include <vnet/ip/icmp46_packet.h>
 #include <vnet/ip/ip6.h>
+#include <vnet/ip-neighbor/ip_neighbor_types.h>
 
 typedef enum
 {
@@ -88,6 +89,10 @@
   vnet_buffer (b)->sw_if_index[VLIB_TX] = sw_if_index0;
   vnet_buffer (b)->sw_if_index[VLIB_RX] =
     vnet_main.local_interface_sw_if_index;
+
+  vlib_increment_simple_counter (
+    &ip_neighbor_counters[AF_IP6].ipnc[VLIB_TX][IP_NEIGHBOR_CTR_REPLY],
+    vm->thread_index, sw_if_index0, 1);
 }
 
 #endif /* included_ip6_nd_inline_h */