IP directed broadcast

with ip direct broadcast enable a packet to the interface's
subnet broadcast address with be sent L2 broadcast on the
interface. dissabled, it will be dropped. it is disabled by
default, which preserves current behaviour

Change-Id: If154cb92e64834e97a541b32624354348a0eafb3
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/adj/adj.c b/src/vnet/adj/adj.c
index 0de3fc8..80a5d05 100644
--- a/src/vnet/adj/adj.c
+++ b/src/vnet/adj/adj.c
@@ -35,6 +35,13 @@
  */
 int adj_per_adj_counters;
 
+const ip46_address_t ADJ_BCAST_ADDR = {
+    .ip6 = {
+        .as_u64[0] = 0xffffffffffffffff,
+        .as_u64[1] = 0xffffffffffffffff,
+    },
+};
+
 always_inline void
 adj_poison (ip_adjacency_t * adj)
 {
@@ -172,6 +179,7 @@
         /* FALL THROUGH */
     case IP_LOOKUP_NEXT_ARP:
     case IP_LOOKUP_NEXT_REWRITE:
+    case IP_LOOKUP_NEXT_BCAST:
 	/*
 	 * complete and incomplete nbr adjs
 	 */