Re: Default number of dns retries doubled

["Carlos O'Donell" <carlos at redhat dot com>]

On 08/16/2013 05:02 PM, Ángel González wrote:
> On 16/08/13 20:34, Carlos O'Donell wrote:
>> You'll have to dig into the code to see why it's sending multiple requests.
>>
>> If you can put together a reproducer (usually a test program,
>> /etc/resolv.conf, and a bind config) that we can run on a single
>> system that would be great.
>>
>> Cheers,
>> Carlos.
> Ok, it turns out to be really silly.
> Checking the glibc functions, res_ninit() does indeed initialize retry to RES_DFLRETRY (2)
> but res_init() does its own initialization hardcoding a 4 on that field:
>> _res.retry = 4;
> 
> It seems to have been this way since b43b13ac25, which introduced the RES_DFLRETRY
> set to 2 while keeping the line hardcoding it to 4 (although moved from res_init.c
> to res_libc.c)
> 
> And that line goes back to the original 1995 commit 28f540f4.
> 
> 
> So I guess RES_DFLRETRY should be changed to 4 (and the 4 to the constant), to keep
> the historical behavior. It will be a change for programs calling res_ninit() directly, but
> less intrusive than changing the res_init() default used on almost every networked
> program (although I wonder how many systems out there work with 4 attempts but
> would fail with 2, probably few, but there's the possibility on systems with an high
> packet drop).
> 

Please file a bug for this and include as detailed a description
of the problem as you can provide.

I'd be happy to see a patch with rationale for the change, but keep
in mind that we are a conservative project. So we want to keep as
many existing programs working.

Cheers,
Carlos.