+#define vnet_buffer2(b) ((vnet_buffer_opaque2_t *) (b)->opaque2)
+
+/*
+ * The opaque2 field of the vlib_buffer_t is intepreted as a
+ * vnet_buffer_opaque2_t. Hence it should be big enough to accommodate one.
+ */
+STATIC_ASSERT (sizeof (vnet_buffer_opaque2_t) <=
+ STRUCT_SIZE_OF (vlib_buffer_t, opaque2),
+ "VNET buffer opaque2 meta-data too large for vlib_buffer");