fib: format deleted LB

This patch allows the formatting of deleted Load-balancer
objects. This is needed in the case a trace references a DPO
that went away in the interim.

Type: improvement

Change-Id: I6d67519b8d62f69aafde3c8fe3065bc85a7adbde
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
diff --git a/src/vnet/dpo/load_balance.h b/src/vnet/dpo/load_balance.h
index 3605d82..eee073f 100644
--- a/src/vnet/dpo/load_balance.h
+++ b/src/vnet/dpo/load_balance.h
@@ -232,6 +232,14 @@
     return (pool_elt_at_index(load_balance_pool, lbi));
 }
 
+static inline load_balance_t *
+load_balance_get_or_null (index_t lbi)
+{
+  if (pool_is_free_index (load_balance_pool, lbi))
+    return 0;
+  return (pool_elt_at_index (load_balance_pool, lbi));
+}
+
 #define LB_HAS_INLINE_BUCKETS(_lb)		\
     ((_lb)->lb_n_buckets <= LB_NUM_INLINE_BUCKETS)