pt_prefix_cmp
int pt_prefix_cmp(const struct pt_entry *, const struct pt_entry *);
RB_PROTOTYPE(pt_tree, pt_entry, pt_e, pt_prefix_cmp);
RB_GENERATE(pt_tree, pt_entry, pt_e, pt_prefix_cmp);
return (pt_prefix_cmp(a->prefix, b->prefix));