VariableIP_FILTER_RDNS
Introduced Version1.37
DescriptionIP filter for filtering which IP addresses may be queried with the rdns function
Default 

An IP filter for filtering which IP addresses may be queried with the rdns function.

The syntax of these list is a sequence, seperated 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 we deny RDNS queries on the CIDR block 192.168.0.0/16 and allow all others:

ini files
IP_FILTER_RDNS=deny 192.168.0.0/16; allow all