@param base the evdns_base to which to apply this operation
@param in an IPv4 address
@param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query.
@param callback a callback function to invoke when the request is completed
@param ptr an argument to pass to the callback function
@return an evdns_request object if successful, or NULL if an error occurred.
@see evdns_resolve_reverse_ipv6(), evdns_cancel_request()
Lookup a PTR record for a given IP address.
@param base the evdns_base to which to apply this operation @param in an IPv4 address @param flags either 0, or DNS_QUERY_NO_SEARCH to disable searching for this query. @param callback a callback function to invoke when the request is completed @param ptr an argument to pass to the callback function @return an evdns_request object if successful, or NULL if an error occurred. @see evdns_resolve_reverse_ipv6(), evdns_cancel_request()