-int adns_callback(adns_state, fd_set readfds, fd_set writefds,
- fd_set exceptfds, int maxfd);
-/* For select-driven programs, this allows adns to know which fd's are relevant,
- * so that it doesn't need to make syscalls on others of its fd's. It's a kind
- * of limited flow-of-control allowance. It will return how many adns fd's were
- * in the set, so you can tell if your select handling code is missing things.
+void adns_interest(adns_state, int *maxfd_io, fd_set *readfds_io,
+ fd_set *writefds_io, fd_set *exceptfds_io,
+ struct timeval **tv_mod, struct timeval *tv_buf);
+/* Find out file descriptors adns is interested in, and when it
+ * would like the opportunity to time something out. If you do not plan to
+ * block then tv_mod may be 0. Otherwise, tv_mod may point to 0 meaning
+ * you have no timeout of your own, in which case tv_buf must be non-null and
+ * _interest may fill it in and set *tv_mod=tv_buf.
+ * readfds, writefds, exceptfds and maxfd may not be 0.