https://ml-archives.squid-cache.org/squid-users/2020-May/022122.html
[squid-users] Client IP PTR lookup on connect
ptr lookupsquidusersclientip
https://ptrdb.com/
IP segment Ptr query | Ptr query C segment | Ptr website query IP reverse | lookup Ptr query
Query the Ptr on the specified iP address segment and provide iP reverse lookup Ptr query data
ipsegmentptrqueryc