Return NOTIMP on inverse queries

[NotBad4U]

Inverse queries

Inverse DNS Queries (Reverse DNS Queries) are used when the user wants to resolve the IP Address to a Fully Qualified Domain Name. Inverse queries are primarily useful for debugging and database maintenance activities.

Purpose

According to the rfc1034, the implementation of this service is optional in a name server, but all name servers must at least be able to understand an inverse query message and return a not-implemented error response.

What to do

For now, we'll not support inverse queries and just return RcodeNotImplemented to be compliant with the RFC 1034.