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Re: (ITS#7027) [PATCH] Implement priority/weigh for DNS SRV records
- To: openldap-its@OpenLDAP.org
- Subject: Re: (ITS#7027) [PATCH] Implement priority/weigh for DNS SRV records
- From: firstname.lastname@example.org
- Date: Tue, 22 Jul 2014 06:13:15 GMT
- Auto-submitted: auto-generated (OpenLDAP-ITS)
Taking a look again as it was recently called to our attention in
>> In addition, random seed has to be initialized, otherwise the behavior
>> is predictable.
> I didn't think it too big of a deal, since it doesn't have to be
> cryptographically random. I can submit a patch to call srandom()
>> On the other side, I do not think that calling srand()
>> in libldap is a good idea. The client application should do that. Or
>> is there any other option?
Agreed, calling srand() inside libldap would probably be a bad idea. Nor does
it seem critical to use any particularly high quality PRNG here. I've added a
commonly used LCG instead, seeded by time().
> The function ldap_domain2hostlist returns a list of strings, there
> isn't any weight/prio information for the client to act
> on. Furthermore the weight prio section was commented out, I figured
> the library was the right place to do it.
> The algo specified in rfc2782 is detailed, and specifies a random
> number should be generated., I didn't want to implement it because it
> results in sorting once by prio, once by weight instead of one sort
> that does both.
You cannot shuffle inside quicksort, its behavior is undefined if the compare
function isn't consistent/transitive. There's a good illustration of one
problem with that here http://bost.ocks.org/mike/algorithms/#shuffling
I've simplified the qsort comparator and added the explicit shuffle step.
This is now fixed in git master.
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/