[dns-operations] check if a domain has been registered via DNS

[John Levine]

In article <96588FBC-7775-469A-B2DD-D4A4504D9B90 at dukhovni.org> you write:
>> What would work for your situation is to test for the presence of NS records at the registry level, and if they are absent to fall
>back to whois to confirm.
>
>Some subdomains of public suffix parent domains are CNAMEs, and only
>the target of the CNAME has NS records.

Um, other than the the very peculiar .NAME TLD, I'm reasonably sure
you're mistaken.

>;; QUESTION SECTION:
>;vwtelecom.eu.                  IN      NS

Let's try asking the .eu TLD servers:

$ dig @x.dns.eu. vwtelecom.eu. ns

; <<>> DiG 9.11.1 <<>> @x.dns.eu. vwtelecom.eu. ns
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32124
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 3
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;vwtelecom.eu.			IN	NS

;; AUTHORITY SECTION:
vwtelecom.eu.		86400	IN	NS	ns1.openprovider.nl.
vwtelecom.eu.		86400	IN	NS	ns2.openprovider.be.
vwtelecom.eu.		86400	IN	NS	ns3.openprovider.eu.

;; ADDITIONAL SECTION:
ns3.openprovider.eu.	86400	IN	A	37.230.96.155
ns3.openprovider.eu.	86400	IN	AAAA	2a02:348:8e:609b::155

R's,
John