#4712 [BIND DNS] Update reverse records not working if a reverse record is present
I've noticed that webmin isn't creating reverse PTR records when adding an A record to a DNS zone if another PTR with the same address already exists.
Picking the "Yes, and replace existing" option when creating the A record will work.
Editing an existing A record and filling in the "update reverse: yes" option doesn't work either.
This has worked in past versions of webmin, pre-1.780.
Setup:
BIND DNS server bind-9.8.2-0.37.rc1.el6_7.6 (running in a chroot)
CentOS 6.7
webmin-1.780-1
2 DNS zones configured: forwardzone.pt and 10.in-addr.arpa
view "public" {
match-clients { any; };
allow-query { any; };
recursion no;
zone "forwardzone.pt" {
type master;
file "master/forwardzone.pt.public";
};
zone "10.in-addr.arpa" {
type master;
file "master/10.0.0.0_8.public.rev";
};
};
Steps to reproduce:
1. open webmin, go to BIND DNS Server -> forwardzone.pt -> Address
2. add record: www1; 10.2.3.1; update reverse = Yes
3. add record: www2; 10.2.3.1; update reverse = Yes
4. add record: www3; 10.2.3.3; update reverse = Yes
5. add record: www4; 10.2.3.3; update reverse = Yes (and replace existing)
6. Check reverse records added
Expected:
1.3.2.10.in-addr.arpa. IN PTR www1.forwardzone.pt. 1.3.2.10.in-addr.arpa. IN PTR www2.forwardzone.pt. 3.3.2.10.in-addr.arpa. IN PTR www4.forwardzone.pt.
Actual result:
1.3.2.10.in-addr.arpa. IN PTR www1.forwardzone.pt. 3.3.2.10.in-addr.arpa. IN PTR www4.forwardzone.pt.
One would expect to add a second PTR record for the 1.3.2.10.in-addr.arpa. address, but webmin silently fails.
The zone files (after the tests):
;;; /var/named/master/forwardzone.pt.public
$ttl 38400
forwardzone.pt. IN SOA lolcathost. dnsadmin.forwardzone.pt (
2015070111
10800
3600
604800
38400 )
forwardzone.pt. IN NS lolcathost.
www1 IN A 10.2.3.1
www2 IN A 10.2.3.1
www3 IN A 10.2.3.3
www4 IN A 10.2.3.3
;;; /var/named/master/10.0.0.0_8.public.rev
$TTL 86400
@ IN SOA . dnsadmin.forwardzone.pt. (
2016021110
10800
3600
604800
86400 )
IN NS lolcathost.
1.3.2.10.in-addr.arpa. IN PTR www1.forwardzone.pt.
3.3.2.10.in-addr.arpa. IN PTR www4.forwardzone.pt.
That is actually expected - you can't have two PTR records for the same IP (as far as I know)
We can have multiple PTR records for the same address, it's just not recommended. We have a working setup where a few hosts have multiple reverse records.
If webmin won't add a second PTR, can it at least output some message stating that a reverse record already exists?
Out of interest, in what situation is having multiple PTR records for the same IP useful?
When you have multiple websites hosted behind the same IP address, for example.
If you have www.example1.com, www.example2.com, www.example3.com pointing to 11.22.33.44, it'd be useful to reverse-lookup that IP address to find all the names pointing to it.
Ok, I will look into supporting multiple PTR records for the same IP in Webmin / Virtualmin.