DuplicateCNAME returns true if r already exists in records.

ExtractAddressFromReverse turns a standard PTR reverse record name into an IP address.

IsReverse returns 0 is name is not in a reverse zone.

Join joins labels to form a fully qualified domain name.

MinimalTTL scans the message returns the lowest TTL found taking into the response.Type of the message.

ParseHostPort will check if the host part is a valid IP address, if the IP address is valid, but no port is found, defaultPort is added.

ParseHostPortOrFile parses the strings in s, each string can either be a address, address:port or a filename.

TrimZone removes the zone component from q.

IP4arpa is the reverse tree suffix for v4 IP addresses.

IP6arpa is the reverse tree suffix for v6 IP addresses.

MaximumDefaulTTL is the maximum TTL was use on RRsets in CoreDNS.

MinimalDefaultTTL is the absolute lowest TTL we use in CoreDNS.