VariableIP_FILTER_RDNS
Introduced Version1.37
DescriptionIP_FILTER_RDNS Environment Variable
Default 

IP_FILTER_RDNS

A 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