How to configure CoreDNS to resolve CNAME records using foreign resolver

Question

I am looking for an example configuration in which CoreDNS will read the CNAME record from the file (file plugin) and then resolve it using a custom resolver (forward plugin?). A client should not get CNAME record but only A records.

For example:

• if the client ask the CoreDNS for test.r1.svc
• then the CoreDNS get the CNAME record test IN CNAME test.r2.svc.
• then ask the foreign resolver 10.11.12.13:53 for test.r2.svc
• and response to the client with the A records

Is it possible?

This config is not working for me:

Corefile

# root
. {
  log
  errors
}

r1.svc {
  file r1.svc
  forward r2.svc 10.11.12.13:53
  log
  errors
}

r1.svc file

$ORIGIN r1.svc.
@ 3600 IN SOA sns.dns.icann.org. noc.dns.icann.org. (
    202211241713 ; serial
    7200         ; refresh (2 hours)
    3600         ; retry (1 hour)
    1209600      ; expire (2 weeks)
    3600         ; minimum (1 hour)
)
3600 IN NS a.iana-servers.net.
3600 IN NS b.iana-servers.net.
test IN CNAME test.r2.svc.

Answer 1

I might be mistaken, but the forward r2.svc 10.11.12.13:53 is in the r1.svc block so it will never get called.

Client asks for test.r1.svc
Server responds that it's a CNAME for test.r2.svc
Client asks for test.r2.svc
Server doesn't know how to process the answer

Moving the forward r2.svc 10.11.12.13:53 line to the . block should allow it to process the second request.

Answer 2

I wrote plugin for CoreDNS to do it: https://github.com/kinjelom/coredns-recursor