[asterisk-dev] [Code Review] 3343: res_pjsip: Enable DNS support.

[Joshua Colp]

Olle E. Johansson wrote:
>
> On 13 Mar 2014, at 11:42, Joshua Colp <reviewboard at asterisk.org
> <mailto:reviewboard at asterisk.org>> wrote:
>
>> In case others are wondering as Olle was:
>>
>> PJLIB-Util (part of pjproject) provides a DNS client which can
>> optionally (but is highly suggested) to be used with PJSIP. It
>> provides asynchronous DNS, SRV lookups, multiple record support,
>> etc. Right now this isn't enabled so we are simply doing A/AAAA
>> record lookups. The reason it's not enabled is that explicit
>> nameservers *must* be provided to it when enabling it. It will not
>> use the system ones by itself. The change up on reviewboard enables
>> it by default using the system nameservers it finds, but with the
>> ability to override or completely disable it if a user wants. The
>> reason I also provide reload functionality is that people in
>> #asterisk-dev expressed a concern that users may change nameservers
>> but don't want to restart Asterisk, which is understandable.
>
> Interesting to get answer in another channel... For both of us.
>
> My question still stands - why would anyone want one part of Asterisk
>  use other DNS servers than the rest of Asterisk and the rest of the
>  system? If there is something wrong with the system resolver, that
> needs to be fixed.
>
> I do not see the need for us to have a configuration option here.
> Someone else may have a good reason for it.

I can't guarantee that the code which automatically determines and gets 
the nameservers from the system will work on all platforms. It's using 
res_init / res_ninit which, depending on the implementation, parses 
resolv.conf and stores the information. I think it *should* work but for 
cases where it won't the ability to manually set them is there. For most 
people you don't even need to know it exists or set it.

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US
Check us out at: www.digium.com & www.asterisk.org