[Freeipa-devel] [PATCH 0064-0065] ipa-dns-install offers IP addresses from resolv.conf as default forwarder

[Petr Spacek]

On 11.11.2015 09:36, Martin Babinsky wrote:
> On 11/11/2015 09:32 AM, Jan Cholasta wrote:
>> On 11.11.2015 09:27, Martin Babinsky wrote:
>>> On 11/11/2015 08:12 AM, Jan Cholasta wrote:
>>>> On 10.11.2015 16:58, Petr Spacek wrote:
>>>>> Hello,
>>>>>
>>>>> Patch 64:
>>>>> ipa-dns-install offer IP addresses from resolv.conf as default
>>>>> forwarders
>>>>>
>>>>> In non-interactive more option --auto-forwarders can be used to do the
>>>>> same. --forward option can be used to supply additional IP addresses.
>>>>>
>>>>> https://fedorahosted.org/freeipa/ticket/5438
>>>>
>>>> IMO it's perverse to add option which effectively means "use default
>>>> value" instead of actually using the value as default. This is
>>>> inconsistent with every other option and I don't see what makes
>>>> forwarders so special to require this.
>>>>
>>>> NACK unless you have a strong justification for this.

Motivation:
/etc/resolv.conf holds nearest DNS servers. On the other hand, you want to
have backup forwarder which may not be local but could work even if local ones
fail.

Option --default-forwarders reads list of "local" servers from resolv.conf and
--forwarder option allows you to add additional IP addresses to it.

So your Ansible script can contain call like:
ipa-server-install --setup-dns --default-forwarder
--forwarder=<company-wide-fallback>
and you do not need to worry about mapping sites to nearest servers etc.

>>> Is it possible to use default_getter decorator to fetch defaults for the
>>> 'forwarders' knob from the resolver if it is avaliable like so (warning:
>>> untested and possibly wrong)?
>>
>> Yes, this is exactly how it should be used (although the exception
>> handling could be better).
>>
> That was just a quick example off the top of my head without much thought
> going into it.
> 
> Anyway, when running in interactive mode the installer can inform the user
> that he found these forwarders as defaults and prompt whether they shoud be used.

After discussion in person we decided to not use default_getter decorator
because that would change current behavior in an unexpected way.

Original option --auto-forwarders was renamed to --default-forwarders because
it sounds nicer :-D

>>>>> Patch 65:
>>>>> Remove global variable dns_forwarders from ipaserver.install.dns
>>>>> It seems to me that the global thingy is not necessary, so I've ripped
>>>>> it out.
>>>>
>>>> ACK.

Rebased version of patch 65 is attached.

-- 
Petr^2 Spacek
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