CoreDNS

CoreDNS is DNS server that started as a fork of Caddy. It has the same model: it chains middleware.

Status

Currently CoreDNS is able to:

• Serve zone data from a file, both DNSSEC (NSEC only atm) and DNS is supported.
• Retrieve zone data from primaries, i.e. act as a secondary server.
• Allow for zone transfers, i.e. act as a primary server.
• Use Etcd as a backend, i.e. a 90% replacement for SkyDNS.
• Serve as a proxy to forward queries to some other (recursive) nameserver.
• Rewrite queries (both qtype, qclass and qname).
• Provide metrics (by using Prometheus)
• Provide Logging.

There are corner cases not implemented and a few issues.

But all in all, CoreDNS should already be able to provide you with enough functionality to replace parts of BIND9, Knot, NSD or PowerDNS. However CoreDNS is still in the early stages of development and should not be used on production servers yet. For now most documentation is in the source and some blog articles can be found here. If you do want to use CoreDNS in production, please let us know and how we can help.

https://caddyserver.com/ is also full of examples on how to structure a Corefile (renamed from Caddyfile when I forked it).

Examples

Start a simple proxy:

Corefile contains:

.:1053 {
    proxy . 8.8.8.8:53
}

Just start CoreDNS: ./coredns. And then just query on that port (1053), the query should be forwarded to 8.8.8.8 and the response will be returned.

Serve the (NSEC) DNSSEC signed miek.nl on port 1053, errors and logging to stdout. Allow zone transfers to everybody.

miek.nl:1053 {
    file /var/lib/bind/miek.nl.signed {
        transfer to *
    }
    errors stdout
    log stdout
}

Serve miek.nl on port 1053, but forward everything that does not match miek.nl to a recursive nameserver and rewrite ANY queries to HINFO.

.:1053 {
    rewrite ANY HINFO

    proxy . 8.8.8.8:53

    file /var/lib/bind/miek.nl.signed miek.nl {
        transfer to *
    }
    errors stdout
    log stdout
}

All the above examples are possible with the current CoreDNS.

What remains to be done

• Website?
• Logo?
• Code simplifications/refactors.
• Optimizations.
• Load testing.
• All the issues.

Blog

https://miek.nl/tags/coredns/