check_icmp wish list (was: [Nagiosplug-devel] check_ping and check_icmp confusion)

[Marc Haber]

On Wed, Feb 22, 2006 at 06:36:03PM +0100, Andreas Ericsson wrote:
> check_icmp had some problems on systems with 32-bit process id's in the 
> early days (causing it to mark the packets wrong and then not 
> recognizing them when they returned). It also used to calculate timings 
> slightly wrong. Both those problems are solved long since, however. Now 
> there are no real reasons to use check_ping instead of check_icmp.

While we're at it: I have recently come across some systems which have
ICMP echo request filtered, but send "host unreachable, administrative
prohibition" back. It would be great if check_icmp could would have a
command line option listing which ICMP packet types are considered a
valid response.

Additionally, it would be good to be able to specify a TTL value so
that one could force a remote host to issue a "TTL exceeded" packet
just in case that "host unreachable" is not configured as well.

for example, 195.20.247.162, the last hop before the monitored host
nechayev.zugschlus.de, is configured to show up in a traceroute, but
doesn't answer to pings at all. That one could be monitored by sending
a ping with the appropriate ttl to the actual host being monitored,
forcing the otherwise silent gateway to answer with "Time to live
exceeded":

$ ping -c 1 -w 10 195.20.247.162
PING 195.20.247.162 (195.20.247.162) 56(84) bytes of data.
--- 195.20.247.162 ping statistics ---
10 packets transmitted, 0 received, 100% packet loss, time 9030ms
$ ping -c 1 -t 8 nechayev.zugschlus.de
PING nechayev.zugschlus.de (217.160.109.85) 56(84) bytes of data.
>From gw-prtr-a.ds.ka.schlund.net (195.20.247.162) icmp_seq=1 Time to live exceeded
--- nechayev.zugschlus.de ping statistics ---
1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
$

This allows host failures to be distinguished from network outages
even in uncooperative networks, which is a nice thing to have and
could be implemented easily in the existing check_icmp code.

Greetings
Marc

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