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Date:      Mon, 3 Jun 2013 23:39:31 -0400
From:      staticsafe <me@staticsafe.ca>
To:        freebsd-questions@freebsd.org
Subject:   Re: System Calls that do DNS
Message-ID:  <20130604033930.GA10393@uriel.asininetech.com>
In-Reply-To: <F5EBDC53-CBA3-415D-B7CD-1EC873692348@lafn.org>
References:  <F5EBDC53-CBA3-415D-B7CD-1EC873692348@lafn.org>

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On Mon, Jun 03, 2013 at 07:57:07PM -0700, Doug Hardie wrote:
> I have an unusual situation.  A program is doing a DNS lookup and often the IP address has no reverse DNS entries.  As a result the program hangs for several timeouts.  The call is not being made directly in its code, but is occurring in a system call.  There are no specific calls to DNS, its something else doing it.  I have been trying to track down which system call is doing it, but without success so far.  I have tried syslog calls around each of the system calls I thought might be the culprit, but my guessing is not very good.  How can I identify the system call that is calling DNS?  If I can find it, I hopefully can find another way to do whatever it does that does not involve a reverse DNS lookup.
> 
> 

Use truss:
http://www.freebsd.org/cgi/man.cgi?query=truss

The truss utility traces the system calls called by the specified
process or program.
-- 
staticsafe
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