With a few bug fixes and general improvements, c-ares 1.6.0 was released just now with these new additions:
- support for the glibc “rotate” resolv.conf option (or ARES_OPT_ROTATE)
- ares_gethostbyname_file()
- ares_dup()
- ares_set_socket_callback()
(the man pages for the new functions are not yet available on the web site but I’m meaning to get to that soonish)