# Functions
CopyDNSClient performs a deep copy of dnsClient, changing the network to TCP.
ExchangeTKEY exchanges TKEY records with the given host using the given key name, algorithm, mode, and lifetime with the provided input payload.
# Constants
TkeyModeDelete is used for key deletion.
TkeyModeDH is used for Diffie-Hellman exchanged keying.
TkeyModeGSS is used for GSS-API establishment.
TkeyModeResolver is used for resolver assigned keying.
TkeyModeServer is used for server assigned keying.
# Interfaces
Exchanger is the interface a DNS client is expected to implement.