DDNS client: Multiple zone entries

[nsvora]

Hi All,

While testing the DDNS server configuration with proprietory client, I
noticed a strange thing. I need your help to understand this.


Pre-condition:
-----------------------
DHCP and DDNS server are running on a single Red Hat LINUX machine.
The DHCP server was able to generate the dynamic IP Address as
specified in the dhcpd.conf.
DDNS server was able to add the entries in the forward and reverse zone
files eg : testdns.com and 1.168.192.in-addr.arpa


Test Condition:
--------------------------
I modified the host name and restarted the named service so that
changes are reflected in the zone files. The forward zone file was
expected to be updated with the modified host name.

Results:
------------

Forward zone had two entries viz; one with old host name and other with
new host name.

Analysis:
-------------

I have found that this is happening because in DDNS client code,
before updating the server database with modified host name, client is
checking whether a record with "new" host name exists.

And server replies in negative for this ( which is correct ) and  we
add a new record for the new host name. But previous entry with the old
host name is never deleted from the server.

This check is done via "Prerequisite" record sent by the DDNS
client. Since the prerequisite check fails, client doesn't send
request for deletion of the "old" host name entry.

Forward zone file : /var/named/chroot/var/named/example.com.zone


Could you kindly let me know if this behavior is correct to have
multiple entries in the forward zone on change of host name.

( Similar would be observed for reverse zone on change of IP Address
i.e multiple IP point to same name. )

Thanks in advance,

With Regards,
Nirav