Custom DNS Filtering Plugin in BIND 9

[Mónika Kiss]

Dear BIND Users,

    My name is Monika Kiss and I am currently working on a custom DNS
filtering plugin for BIND 9 and I would appreciate your guidance on a few
technical aspects. My goal is to intercept certain DNS queries and return a
custom IP address instead of forwarding them to an upstream resolver.

Context:

   - I am using BIND 9’s plugin system to implement DNS filtering. (BIND9
   version 9.20.6 on Ubuntu 22.04 )
   - In specific cases (e.g., for high-risk domains), I want to return a
   predefined IP address (e.g., 192.168.1.100) instead of resolving the query
   normally.
   - I have implemented a plugin, and I am hooking into
   NS_QUERY_START_BEGIN to analyze and potentially modify responses.

Challenges & Questions:

   - Properly constructing and returning a custom DNS response.
   - Plugin Development Guidance:
      - Are there official documentation or examples for writing custom
      BIND 9 plugins?
      - What are the recommended hook points for intercepting and modifying
      DNS responses?

    I would be very grateful for any insights, documentation, or example
implementations that could help me achieve this functionality. Thank you in
advance for your support!


*Best regards,*

Monika Kiss
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