CNAMEs in in-addr.arpa delegation tree are not handled

[dupuy]

For example, https://gwhois.org/12.129.75.12+dns reports that "No PTR records found for 12.129.75.12 @dbru.br.ns.els-gms.att.net (68.94.156.134)" which is true:

$ dig +norec +nocmd +nostats -x 12.129.75.12 @dbru.br.ns.els-gms.att.net
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50745
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0

;; QUESTION SECTION:
;12.75.129.12.in-addr.arpa.	IN	PTR

;; ANSWER SECTION:
12.75.129.12.in-addr.arpa. 172800 IN	CNAME	12.0/27.75.129.12.in-addr.arpa.

;; AUTHORITY SECTION:
0/27.75.129.12.in-addr.arpa. 172800 IN	NS	ns-west.cerf.net.
0/27.75.129.12.in-addr.arpa. 172800 IN	NS	ns-east.cerf.net.

These kinds of CNAMEs are often used for CIDR non-byte delegation of in-addr.arpa subdomains (see https://tools.ietf.org/html/rfc2317—but there are also CNAMEs following other patterns, see http://www.he.net/adm/reverse.dns.html).

And in this case, if you ask one of the authorities, you get an answer:

$ dig +norec +nocmd +nostats PTR 12.0/27.75.129.12.in-addr.arpa. @ns-west.cerf.net.
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 56886
;; flags: qr aa; QUERY: 1, ANSWER: 3, AUTHORITY: 2, ADDITIONAL: 4

;; QUESTION SECTION:
;12.0/27.75.129.12.in-addr.arpa.	IN	PTR

;; ANSWER SECTION:
12.0/27.75.129.12.in-addr.arpa.	86400 IN PTR	trax.abxglobal.com.
12.0/27.75.129.12.in-addr.arpa.	86400 IN PTR	trax.abxlogistics.com.
12.0/27.75.129.12.in-addr.arpa.	86400 IN PTR	www.abxglobal.com.

;; AUTHORITY SECTION:
0/27.75.129.12.in-addr.arpa. 86400 IN	NS	ns-east.cerf.net.
0/27.75.129.12.in-addr.arpa. 86400 IN	NS	ns-west.cerf.net.

;; ADDITIONAL SECTION:
ns-west.cerf.net.	3600	IN	A	68.94.156.136
ns-east.cerf.net.	3600	IN	A	99.99.99.136
ns-west.cerf.net.	3600	IN	AAAA	2001:1890:1ff:9f0:68:94:156:136
ns-east.cerf.net.	3600	IN	AAAA	2001:1890:1ff:9f1:99:99:99:136