loose access control that works for dynamic IP address

[Zhang Weiwu <zhangweiwu@realss.com>]

Hello.

I need rather loose security that the server daemon offer services on a
TCP port, allow/deny a client's tcp incoming connection based on a FQDN.
The problem being the ip address of the FQDN is a dynamic one of the
same host, changing once per three days.

I know both IP table and tcpd can manage allow/deny rule based on IP
addresses, but can they do so with a FQDN that maps to dynamic IP address?

Thanks in advance!

P.S. I am totally aware of the security risk of authenticating a client
based on its FQDN, including being aware of attacks based on DNS
spoofing. If you usually insist on either solid security or no security,
please kindly ignore this post.

Best.
Zhang Weiwu