[Nagiosplug-devel] [ nagiosplug-Bugs-1469472 ] check_ping dns lookup problem

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Bugs item #1469472, was opened at 2006-04-12 21:42
Message generated for change (Comment added) made by nsturm
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Category: General plugin execution
Group: Release (specify)
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: nsturm (nsturm)
Assigned to: Matthias Eble (psychotrahe)
Summary: check_ping dns lookup problem

Initial Comment:
This is on 1.4.2.

check_ping and maybe other plugins, first set their
SIGARLM timeout and then do an unconditional dns lookup
on the address provided, even if it is an IP.

Besides the dns lookup on the IP address is useless to
the best of my knowledge, it can timeout, which the code
does not handle.

If the dns lookup does time out, fileno(child_process)
in popen_timeout_alarm_handler() will segfault.

A simple workaround, which is BAD BAD BAD, is attached.
The proper solution would be to rewrite this piece of
code (and similar ones on other modules) to correctly
deal with the dns timeout.

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>Comment By: nsturm (nsturm)
Date: 2007-05-09 12:51

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It looks as if popen_timeout_alarm_handler() and check_ping.c were
rewritten to address these issues. From my point of view, the request
can be closed.

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Comment By: Matthias Eble (psychotrahe)
Date: 2007-05-09 12:18

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Hi all,

i have tried to reproduce this one wich cvs and 1.4.2 version, without
success.
I'm also not shure what you exactly mean, since no dns request is made by
check_ping itself (or at least i couldn't find it; doing so wouldn't make
sense to mee).
Check_ping is a wrapper for the ping command, which should make the dns
requests if needed.
It is likely that the ping command does a reverse lookup in your case,
although this should not happen since ping should have been called with the
-n argument. 

Does the problem persist?
Matthias

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Comment By: Peter Beckman (ooglek)
Date: 2006-08-08 20:25

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I agree, this isn't right, and it breaks all too often.

+1

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Comment By: Mark Hennessy (atxformfactor)
Date: 2006-07-12 20:56

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Why hasn't anyone picked this one up?
I have noticed this issue as well.

I get this message when DNS doesn't work due to a name
server connection issue on the machine performing the Nagios
checks:
popen timeout received, but no child process

All of my host entries are by IP, I don't see why check_ping
should need to look up DNS for IPs at all.  Someone should
at least add a commandline switch or something.  I may just
have to write a perl wrapper for my local system's ping if
nothing is done by anyone about this. :(

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