rib: fix insertion in some cases

[ upstream commit e682b02 ]

According to GCC documentation for __builtin_clz:
Returns the number of leading 0-bits in x,
starting at the most significant bit position.
If x is 0, the result is undefined.
__builtin_clz will be called with 0 if the existing
prefix address matches the one we want to insert.

Fixes: 5a5793a ("rib: add RIB library")

Reported-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>

lib/librte_rib/rte_rib.c

@@ -301,7 +301,7 @@ rte_rib_insert(struct rte_rib *rib, uint32_t ip, uint8_t depth)
 	/* closest node found, new_node should be inserted in the middle */
 	common_depth = RTE_MIN(depth, (*tmp)->depth);
 	common_prefix = ip ^ (*tmp)->ip;
-	d = __builtin_clz(common_prefix);
+	d = (common_prefix == 0) ? 32 : __builtin_clz(common_prefix);
 
 	common_depth = RTE_MIN(d, common_depth);
 	common_prefix = ip & rte_rib_depth_to_mask(common_depth);