dnstap: Support for logging query and response messages in AUTH_RESPONSE
The dnstap protocol supports logging both the original query message as well as the response message together inside a single dnstap AUTH_RESPONSE type message. I came up with a use case for this (also see #762 (closed)) where a dnstap-based tool could process a stream of AUTH_RESPONSE log payloads from a DNS server, extract the query_message field, send this DNS query to a second DNS server (and optionally prepend a PROXY v2 header using the query_address and query_port dnstap fields), receive a response back from the second DNS server, and then compare the new response to the originally logged response from the first DNS server in the dnstap response_message field. Any discrepancies between the first and second DNS servers would be logged.
Attached is a patch which adds a new responses-with-queries boolean configuration option to the dnstap module to support this functionality.
Thanks for considering!