OptionIP_FILTER_RDNS
Description IP filter for filtering which IP addresses may be queried with the rdns() function or reverseDns() function.
Introduced Version1.37

IP filter for filtering which IP addresses may be queried with the rdns() function or reverseDns() function.

The syntax of the IP address list is a sequence, separated by newlines or ;, of allow or deny actions, along with a CIDR block or all. An IP address is allowed or denied by finding the first match and applying the corresponding action. The all value matches any IP-address (i.e., IPv4 or IPv6).

For example, here LogScale denies RDNS queries on the CIDR block 192.168.0.0/16 and allows all others:

ini
IP_FILTER_RDNS=deny 192.168.0.0/16; allow all

RDNS defaults to denying lookups of reserved IP ranges. The filter also denies additional reserved IP ranges, as specified by the IANA, by default. Self-hosted administrators can specify their own filters by using the environment variables IP_FILTER_IDP, IP_FILTER_RDNS, and IP_FILTER_RDNS_SERVER respectively.