Zone cut NS RRs returned as authoritative records

[Siva Kesava R Kakarla]

Hi again,

Similar to #1272, the issue exists with child NS records also. Consider the same zone file,

example.com.	60480	SOA	ns1.outside.com. root.example.com. 3 604800 86400 2419200 604800
example.com.	60480	NS	ns1.outside.com.
b.g.example.com.	60480	NS	n.b.g.example.com.
n.b.g.example.com.	60480	A	1.1.1.1

For the query <b.g.example.com. , NS>, the TrustDns server returns the following response:

          "rcode NOERROR",
          "flags QR AA",
          ";QUESTION",
          "b.g.example.com. IN NS",
          ";ANSWER",
          "b.g.example.com. 60480 IN NS n.b.g.example.com.",
          ";AUTHORITY",
          "example.com. 60480 IN NS ns1.outside.edu.",
          ";ADDITIONAL",
          "n.b.g.example.com. 60480 IN A 1.1.1.1"

Expected behavior
The AA bit is set in the response, which should not be as this is a child NS record, and the parent is not authoritative of the record. The server should return an empty answer but place <b.g.example.com, NS> in the authority section and the glue record in the additional section as per RFC 6672, Section 3.2, Point 3B. The <example.com, NS> is generally not returned.

System:

• OS: Ubuntu
• Architecture: x86_64
• Version: 18
• rustc version: cargo 1.47.0