Example to do reverse lookups on IP addresses using the RESOLVER::name_lookup command, which replaces the deprecated RESOLV::lookup.

resolver_demo.tcl

#####################################################
### Required net resolver - example configuration ###
#####################################################
 
#net dns-resolver r1 {
#    forward-zones {
#        . {
#            nameservers {
#                8.8.8.8:domain { }
#                9.9.9.9:domain { }
#            }
#        }
#    }
#    route-domain 0
#}
 
# Proc to reverse the IP octets to build the ptr record format
# Downwards compatibility to 8.4: https://wiki.tcl-lang.org/page/lreverse
proc lreverse list {
  set res {}
  set i [llength $list]
  while {$i} {
    lappend res [lindex $list [incr i -1]]
  }
  set res
}
 
when CLIENT_ACCEPTED {
  set tst_ip 54.230.18.2
  # Format the ptr record so the RESOLVER::name_lookup will work properly for a ptr lookup
  set ptr [join [call lreverse [split $tst_ip .]] .].in-addr.arpa
  set result [RESOLVER::name_lookup "/Common/r1" $ptr ptr]
  foreach rr [RESOLVER::summarize $result] {
    log local0.debug [lindex $rr 4]
  }
}
 
# Result:
# Nov 17 22:59:01 ltm3 debug tmm1[88844]: Rule /Common/resolver_demo <CLIENT_ACCEPTED>: server-54-230-18-2.ord51.r.cloudfront.net