May 26, 2018
Convert an IPv4/IPv6 address to an in-addr.arpa/ip6.int PTR value
Convert valid IPv6 addresses to ip6.int PTR values. Convert valid IPv4 addresses to in-addr.arpa PTR values. Anything not valid is simply printed as is. Handles notation and embedded IPv4 addresses. If the address is followed by /n, the PTR is truncated to n bits.