Apex SOA/NS not included in answers after CNAME aliasing

[EchoStone1101]

What happened:

When the query is aliased to the zone origin after hitting a CNAME, the apex SOA/NS records are not included in the ANSWER section, if the query type is SOA/NS.

How to reproduce it (as minimally and precisely as possible):

Using the following zone file (b.a.txt):

b.a.		500 IN SOA	mname.com. rname.com. 3 604800 86400 2419200 604800
b.a.		500 IN NS	h.b.a.
b.a.        500 IN A    1.1.1.1
d.b.a.		500 IN CNAME	b.a.
h.b.a.		500 IN A	100.235.151.110

and this Corefile:

b.a.:1053 {
    header {
        response set ra
    }
    file b.a.txt
}

Response for querying <d.b.a., SOA> (output beautified):

root@e10adfbeed3f:/v# dig @127.0.0.1 -p 1053 d.b.a. SOA

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25994
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;d.b.a.                         IN      SOA

;; ANSWER SECTION:
d.b.a.                  500     IN      CNAME   b.a.

;; AUTHORITY SECTION:
b.a.                    500     IN      NS      h.b.a.

What you expected to happen:

The ANSWER section should also include the b.a. SOA record because it matches the CNAME target and the query type.

Anything else we need to know?:

Environment:

• the version of CoreDNS: CoreDNS-1.11.1, linux/arm64, go1.21.5, 45923b6e
• Corefile: given above.
• OS: this uses the docker environment from "Compilation with Docker".
• Others:

This issue is more intricate than it appears: if the b.a. A record is removed, then the query d.b.a. SOA does return the SOA record in the ANSWER section!

For more related test results:

• Querying for b.a. SOA directly works as intended (SOA included in ANSWER).
• The same issue also applies to apex NS records (change every query type above into NS and the behavior is the same).
• Finally, bind9 handles this correctly under the same setup.

[shiv-tyagi]

Hi @EchoStone1101! I'm new here. I tried coredns recently and I love it. I would like to contribute to the project. I have gone through the basic documentation. I would like to try working on this issue.