[Nagiosplug-devel] check_ping resolving error

[Thomas Guyot-Sionnest]

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On 10/12/08 07:35 AM, Yaron Meiry wrote:
> Thanks everyone for the comments. No more top posting!
> 
> On Wed, Dec 10, 2008 at 1:52 PM, Holger Weiss <holger at cis.fu-berlin.de
> <mailto:holger at cis.fu-berlin.de>> wrote:
> 
> 
>     If you add "-vvv" to the check_ping command line arguments, check_ping
>     will spit out the exact ping(1) command line it's executing.  Does that
>     ping(1) command line work if you execute it manually?  If so, could you
>     post the complete "check_ping -vvv" output?
> 
> 
> /[root at machine libexec]# ./check_ping -H domain.tld -w 3000.0,80% -c
> 5000.0,100% -p 5 -vvv
> CMD: /bin/ping6 -n -U -w 30 -c 5 domain.tld
> Output: PING domain.tld(::ffff:xx.xx.xxx.12) 56 data bytes
> Output:
> Output: --- domain.tld ping statistics ---
> Output: 30 packets transmitted, 0 received, 100% packet loss, time 29010ms
> Output:
> Got stderr: ping: sendmsg: Network is unreachable
> CRITICAL - Network Unreachable (domain.tld)/
> 
> This is interesting. It's running /bin/ping6 instead of /bin/ping. Here

Yes. we enable IPv6 whenever possible and your host advertise an IPv6
address (AAAA record). It looks like check_ping is trying to use ipv6...
you should be able to reproduce it with this hostname as well (both IPv4
and IPv6 connectivity): ipv6.he.net

Now I need to figure out in which cases check_ping try to use IPv6... it
does not happen on my production servers but kernel support for IPv6 is
disabled on them. In an ideal world it should probably use IPv6 only if
there's at least one global address, however it might be hard to make
that portable... So It might never get fixed.

You can disable IPv6 at compile time with this configure argument:

- --without-ipv6

 > I've checked another domain and it checks it with /bin/ping. So
> apparently the problem is that it thinks it should check it with
> /bin/ping6. Question is, why? I haven't checked the sources. I'm gonna
> look into them meanwhile.

Simply because there's an IPv6 address record on your domain. Compare
the DNS queries below for ipv6.he.net and slackware.com:

$ nslookup ipv6.he.net
Server:		127.0.0.1
Address:	127.0.0.1#53

Non-authoritative answer:
Name:	ipv6.he.net
Address: 64.62.200.2

$ nslookup -type=AAAA ipv6.he.net
Server:		127.0.0.1
Address:	127.0.0.1#53

Non-authoritative answer:
ipv6.he.net	has AAAA address 2001:470:0:64::2

Authoritative answers can be found from:

$ nslookup slackware.com
Server:		127.0.0.1
Address:	127.0.0.1#53

Non-authoritative answer:
Name:	slackware.com
Address: 64.57.102.34

$ nslookup -type=AAAA slackware.com
Server:		127.0.0.1
Address:	127.0.0.1#53

Non-authoritative answer:
*** Can't find slackware.com: No answer

Authoritative answers can be found from:

$

Regards,

- --
Thomas
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