[asterisk-dev] [Code Review] 4474: core: Add basic DNS API implementation

[Mark Michelson]

> On March 16, 2015, 2:55 p.m., Mark Michelson wrote:
> > /trunk/include/asterisk/dns_core.h, line 225
> > <https://reviewboard.asterisk.org/r/4474/diff/3/?file=72477#file72477line225>
> >
> >     First off, apologies for bringing this up now rather than earlier, but I did not think of this until over this past weekend.
> >     
> >     The main reason that ast_dns_resolve_async() returns an ast_dns_query is so that the query can be canceled by calling ast_dns_resolve_cancel(). The problem is that there is nothing that prevents the caller of ast_dns_resolve_async() from doing unwanted operations such as adding DNS results/records, or attempting to read results from the query while an async thread is currently writing them.
> >     
> >     What I propose here is returning something other than an ast_dns_query from this function. The structure returned from ast_dns_resolve_async() could be passed to ast_dns_resolve_cancel(), and that's it. This would be similar to how ast_dns_resolve_recurring() works.
> 
> Joshua Colp wrote:
>     I'm not sure how that would stop the reading of results though. We'd need to add a lock in, which is something I was trying to avoid for the core. How hard do we want to enforce things?

The only way that it would not prevent reading of results is if you included dns_internal.h in your source file. If you don't include dns_internal.h in your source, then you would essentially have an opaque handle that was returned by ast_dns_resolve_async() and could be passed to ast_dns_resolve_cancel().


- Mark


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On March 16, 2015, 3:26 p.m., Joshua Colp wrote:
> 
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> https://reviewboard.asterisk.org/r/4474/
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> 
> (Updated March 16, 2015, 3:26 p.m.)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Bugs: ASTERISK-24834
>     https://issues.asterisk.org/jira/browse/ASTERISK-24834
> 
> 
> Repository: Asterisk
> 
> 
> Description
> -------
> 
> This change implements the basic API as described on the DNS API wiki page. Minimal changes have been made as required based on real usage and getting a feel for it. As it is the core functionality is present. Resolvers can register, queries can be made (async / sync).
> 
> As the API was basically copy/pasted from the wiki page there still remain stubs to be filled in for higher level functionality (such as parsing and query sets).
> 
> 
> Diffs
> -----
> 
>   /trunk/main/dns_tlsa.c PRE-CREATION 
>   /trunk/main/dns_srv.c PRE-CREATION 
>   /trunk/main/dns_recurring.c PRE-CREATION 
>   /trunk/main/dns_query_set.c PRE-CREATION 
>   /trunk/main/dns_naptr.c PRE-CREATION 
>   /trunk/main/dns_core.c PRE-CREATION 
>   /trunk/include/asterisk/dns_tlsa.h PRE-CREATION 
>   /trunk/include/asterisk/dns_srv.h PRE-CREATION 
>   /trunk/include/asterisk/dns_resolver.h PRE-CREATION 
>   /trunk/include/asterisk/dns_recurring.h PRE-CREATION 
>   /trunk/include/asterisk/dns_query_set.h PRE-CREATION 
>   /trunk/include/asterisk/dns_naptr.h PRE-CREATION 
>   /trunk/include/asterisk/dns_internal.h PRE-CREATION 
>   /trunk/include/asterisk/dns_core.h PRE-CREATION 
> 
> Diff: https://reviewboard.asterisk.org/r/4474/diff/
> 
> 
> Testing
> -------
> 
> Ran DNS unit tests as done by Mark, they are happy.
> 
> 
> Thanks,
> 
> Joshua Colp
> 
>

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