behavior for cpfoo.com/NS query

[Felipe Gasper via Unbound-users]

Hello,

        I’ve noticed that unbound (1.9.3, built from source) indicates SERVFAIL 
in response to a cpfoo.com/NS query. (unbound-host -t NS cpfoo.com)

        This same query returns a result from `dig +trace`.

        Apparently unbound is doing:

./NS           - to the root servers
com./A         - to the root servers
cpfoo.com./A   - to *.gtld-servers.net
cpfoo.com./NS  - to cpfoo.com -> SERVFAIL

        Putting aside why cpfoo.com is giving SERVFAIL, why does unbound ask 
the server itself what its authoritative nameserver is? Wouldn’t 
*.gtld-servers.net be where that query should go?

        Thank you!

-Felipe Gasper
Mississauga, Ontario