[asterisk-dev] DNS Support in Asterisk

Mark Michelson mmichelson at digium.com
Mon Feb 9 12:10:11 CST 2015

Your opinions pretty much mimic mine.

1) Don't write a DNS library. It's been done many times before by 
others, so just use those.
2) Don't jostle things where it is unnecessary.

As far as implementation details, it's far too early to be criticizing 
those, so I just barely skimmed to make sure they made some amount of 
sense. I imagine as things get more nitty-gritty, you'll come up with a 
more detailed plan with structures, API calls, etc.

With regards to the two third-party libraries you presented, my initial 
impression is that I like c-ares better. Honestly, I find the on-site 
documentation for both libraries to be pretty bad, but c-ares is the 
better of the two. I also like that c-ares has functions for parsing 
different DNS record types. I also like that c-ares is hosted on github. 
Other things that would influence me on this decision:

1) Size: I'd prefer something small to something large, especially if 
the "something large" is a lot of unnecessary utilities that we aren't 
going to use.

2) Activity: I would prefer using a library where, if we wanted to make 
a contribution, we would have some assurance that the change would 
actually be seen by someone and actually merged in.

3) Threading Model: This doesn't is not documented clearly on either the 
c-ares or libunbound sites.

On 02/09/2015 11:19 AM, Joshua Colp wrote:
> Greetings All,
> One topic that came up at AstriDevCon this year (my my, how time has 
> flown by) was DNS support[1]. This included both that provided by 
> PJSIP and DNS support in Asterisk in general. I've created a wiki 
> page[2] which covers a bit of how DNS in Asterisk has evolved, 
> shortcomings core usage has as well as PJSIP, how modules use DNS, and 
> potential ways to improve things going forward. While I've proposed 
> the solution I think strikes the best balance between concerns I'd 
> like to hear more thoughts and discuss what we think is the best 
> option for the project going forward. Thoughts?
> Cheers,
> [1] https://wiki.asterisk.org/wiki/display/AST/AstriDevCon+2014
> [2] https://wiki.asterisk.org/wiki/display/~jcolp/DNS+Support+in+Asterisk

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