[Freeipa-devel] host-del & client uninstall: additional discussion related to DNS needed

[Petr Spacek]

On 3.3.2016 18:15, Martin Basti wrote:
> 
> 
> On 03.03.2016 17:36, Petr Vobornik wrote:
>> On 03/03/2016 03:52 PM, Martin Basti wrote:
>>> Hello all,
>>>
>>> related tickets:
>>> https://fedorahosted.org/freeipa/ticket/5676
>>> https://fedorahosted.org/freeipa/ticket/5675
>>> https://fedorahosted.org/freeipa/ticket/5715
>>>
>>> I'm trying to implement both tickets, but I don't like the way we
>>> decided on devel meeting anymore.
>>>
>>> https://fedorahosted.org/freeipa/ticket/5676#comment:1
>>>
>>> 1)
>>> ipa host-del --updatedns
>>>
>>> I propose to only delete A, AAAA and related PTR records (SSHFP records
>>> explained later). The record are somehow managed by IPA
>>>
>>> I don't like the idea of having an extra option to specify record types
>>> that should be removed or a flag that will remove DNS entry completely.
>>> IMO that is duplication of dnsrecord-mod/del functionality, host-del
>>> should not be used for managing DNS. If somebody wants better
>>> granularity, the one should use 'dnsrecord-mod zone rec --type-rec=' or
>>> 'dnsrecord-del --del-all'
>>
>> AFAIK the proposal on devel meeting was:
>>
>> --update-dns will delete A, AAAA, SSHFP
>> --update-dns=all will delete the whole DNS record LDAP entry
>>
>> there was also a proposal for granularity, e.g., --update-dns=a,aaaa.
> Yes this looks for me like doing an alias for dnsrecord-del command
> 
>>
>> Then it was agreed that --update-dns won't search for SRV records (not
>> mentioned here, so OK).
>>
>> PTR records weren't discussed or decision was not recorded.
> When we remove A/AAAA, then we should remove PTR as well
>>
>> The proposal above keeps backwards compatibility though it may not be
>> possible to do with current framework. Or do we have support for multivalued
>> enum with default value(s) which acts as a flag?
> It needs big hacks in framework, to support is as Flag for old client and Enum
> for new clients
>>
>> If the new option type is too complicated to introduce, then I would prefer
>> to keep current option(flag) with behavior matching proposal for
>> --update-dns or --update-dns=all.
> To use "--update-dns will delete A, AAAA, SSHFP" only was proposed by me here.
> 
>>
>> Definitely big +1 on not introducing a new option.
>>
>> No need to over-engineer it.
>>
>> Not sure about PTR records.
>>
>>>
>>> Note: due backward compatibility --updatedns cannot be migrated to ENUM,
>>> new option needed
>>
>>>
>>> 2)
>>> SSHFP records and host-del (https://fedorahosted.org/freeipa/ticket/5715)
>>>
>>> host-del removes SSH keys from LDAP, thus there is no reason to keep
>>> SSHFP record in DNS, thus SSHFP records should be removed always (even
>>> without --updatedns option)
>>
>> ACK
>>
>>>
>>> 3)
>>> ipa-client-install --uninstall
>>>
>>> SSHFP record are always added via nsupdate to DNS, IMO during client
>>> uninstall all SSHFP record related to client should be removed via
>>> nsupdate too.
>>
>> IMHO not necessary will be solved either by #5676 and/or #5715(currently
>> uninstall indirectly calls ipa-host-disable)
> However host-disable does not do nsupdate, so it will work only for IPA DNS.
> So if nsupdate set SSHPF on non-IPA server, we do not have reverse operation
> in uninstall for that.
> 
>>
>>>
>>> 4)
>>> https://fedorahosted.org/freeipa/ticket/5676
>>>
>>> ipa-client-install --uninstall --delete-host    #suggestions how to name
>>> option for removing host entry for ldap welcome
>>>
>>> Should this option call 'host-del' or 'host-del --updatedns'?
>>>
>>> I would like to avoid additional DNS related option to be added to
>>> ipa-client-install
>>>
>>> Also do we really want to implement this ticket? What is the gain there?
>>
>> The devel discussions which is recorded in
>> https://fedorahosted.org/freeipa/ticket/5676#comment:1
>>
>> Suggests to change default behavior in ipa-client-install --uninstall so
>> that it will call:
>>
>> `ipa host-del --update-dns` instead of `ipa-join --unenroll`. So it will
>> also do #3.
>>
>> Further proposal in #5676 is to introduce a new option(--keephost ??) to
>> keep the host records, i.e., the old behavior.
>>
>> But comment:
>> """
>> simo: maybe keeping backward compatibility is more important, discuss later
>> if --remove option would be better
>> """
>> suggest that further discussion is needed
> 
> I agree with backward compatibility here. A current user may be very surprised
> that all DNS records of the host disappear.

The general problem is that installation process (aka ipa-client-install) is a
mess without documented design (at least when it comes to DNS parts) so it is
quite hard to do the reverse on --uninstall.

Given that were planning to implement integration with external DNS in future
we might want to postpone ipa-client-install changes related to DNS and do
overhaul at once.

For example host plugin will need changes as many assumptions about DNS usage
are oversimplified or simply wrong so delaying changes might save some
headache caused by two behavior changes in two subsequent releases.

-- 
Petr^2 Spacek