plugin.md in the CoreDNS source tree has some pointers on what a plugin for CoreDNS
should have as minimum requirements. It basically boils down to: “it should add something unique and
useful to CoreDNS”. Further more documentation, tests and functionality should all be excellent.
It is easier to list when a plugin can be included in CoreDNS than to say it should stay external, so we will do that:
- First, the plugin should be useful for other people. “Useful” is a subjective term, but the plugin needs to fill a niche that appeals to more than one person.
- It should be sufficiently different from other plugins to warrant inclusion.
- Current internet standards need be supported: IPv4 and IPv6, so A and AAAA records should be handled (if your plugin is in the business of dealing with address records that is).
- It must have tests.
- It must have a README.md for documentation.
- Care must be taken to make it efficient in both memory and CPU.
Plugins for CoreDNS can easily live out-of-tree,
plugin.cfg defaults to CoreDNS' repo but other
repos work just as well.