[Kea-users] DDNS subsequent failure after successful CHG_ADD

MRob mrobti at insiberia.net
Wed Feb 6 20:26:12 UTC 2019


On 2019-02-06 20:02, Jason Guy wrote:
> The override-* options are more about honoring the client's wishes in
> terms of DDNS, as explained in this section of the docs [3].

I understand the docs, but due to the error I showed, my question was, 
maybe client is not requesting DNS update but my override settings force 
the DNS update anyway which cause the error. Though I think probably it 
is not this and Kea DDNS server is making the duplicate DNSUPDATE 
request which is failing (cuz it already exists?). I'm looking for 
advice if I should ignore the error or if it's caused by my settings or 
if it's a Kea bug.


>> kea-dhcp4 follows the behavior prescribed for DHCP servers in RFC
>> 4702 [1]. It is important to keep in mind that kea-dhcp4 provides
>> the initial decision making of when and what to update and forwards
>> that information to D2 in the form of NCRs. Carrying out the actual
>> DNS updates and dealing with such things as conflict resolution are
>> within the purview of D2 itself (Chapter 12, _The DHCP-DDNS Server_
>> [2]). This section describes when kea-dhcp4 will generate NCRs and
>> the configuration parameters that can be used to influence this
>> decision. It assumes that the ENABLE-UPDATES parameter is true.
> 
>> ...the DHCP client states that it intends to do the forward DNS
>> updates and the server should do the reverse updates. By default,
>> kea-dhcp4 will honor the client's wishes and generate a DDNS request
>> to the D2 server to update only reverse DNS data.
> 
>> - The parameter OVERRIDE-CLIENT-UPDATE can be used to instruct the
>> server to override client delegation requests. When this parameter
>> is true, kea-dhcp4 will disregard requests for client delegation and
>> generate a DDNS request to update both forward and reverse DNS data.
> 
>> - The parameter, OVERRIDE-NO-UPDATE, can be used to instruct the
>> server to disregard the client's wishes.  When this parameter is
>> true, kea-dhcp4 will generate DDNS update requests to kea-dhcp-ddns
>> even if the client requests that no updates be done.
> 
> Hope this is more clear,
> Jason
> 
> On Wed, Feb 6, 2019 at 12:14 PM MRob <mrobti at insiberia.net> wrote:
> 
>>> I just commented on your other thread.
>> 
>> Thank you, our version of pdns is quite old (from repo) so I hope
>> upgrading it is the solution. I will report back.
>> 
>>> Does the PDNS record you are
>>> trying to update already exist, and does the DHCID record match
>> the
>>> one in the PDNS records?
>> 
>> Yes, the first CHG_ADD has populated DHCID and correct forward and
>> reverse entries. Thats why I ask, maybe I can ignore this error. I
>> wasn't sure if setting override-*-update was too aggressive
>> 
>>>> Initial forward and reverse DNSUPDATE commands succeed:
>>>> 
>>>> DHCP_DDNS_ADD_SUCCEEDED DHCP_DDNS Request ID xxx: successfully
>> added
>>>> the
>>>> DNS mapping addition for this request: Type: 0 (CHG_ADD)
>>>> 
>>>> But Kea does another CHG_ADD only a minute later and it fails:
>>>> 
>>>> DHCP_DDNS_FORWARD_REPLACE_REJECTED DNS Request ID yyy: Server,
>>>> 10.10.1.254 port:5353, rejected a DNS update request to replace
>> the
>>>> address mapping for FQDN, wkst7.lan., with an RCODE: 8
>>>> DHCP_DDNS_ADD_FAILED DHCP_DDNS Request ID yyy: Transaction
>> outcome
>>>> Status: Failed, Event: UPDATE_FAILED_EVT,  Forward change:
>> failed,
>>>> Reverse change: failed,  request: Type: 0 (CHG_ADD)
>>>> 
>>>> Is this a problem or can it be ignored? Is it due to setting
>>>> "override-no-update": true and "override-client-update": true?
>>>> _______________________________________________
>>>> Kea-users mailing list
>>>> Kea-users at lists.isc.org
>>>> https://lists.isc.org/mailman/listinfo/kea-users
>> _______________________________________________
>> Kea-users mailing list
>> Kea-users at lists.isc.org
>> https://lists.isc.org/mailman/listinfo/kea-users
> 
> 
> Links:
> ------
> [1] http://tools.ietf.org/html/rfc4702
> [2] 
> https://ftp.isc.org/isc/kea/1.5.0/doc/kea-guide.html#dhcp-ddns-server
> [3] 
> https://ftp.isc.org/isc/kea/1.5.0/doc/kea-guide.html#dhcp4-ddns-config


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