Data element for aggressive negative caching. The tree of these elements acts as an index onto the rrset cache. It shows the NSEC records that (may) exist and are (possibly) secure. The rbtree allows for logN search for a covering NSEC record. To make tree insertion and deletion logN too, all the parent (one label less than the name) data elements are also in the rbtree, with a usage count for every data element. There is no actual data stored in this data element, if it is in_use, then the data can (possibly) be found in the rrset cache.
Definition at line 142 of file val_neg.h.