[Nagiosplug-devel] check_by_ssh feature proposal

Dirk Räbiger dirk at mti.ag
Tue Jan 31 06:22:03 CET 2006


= Goal =
An option to turn off host-lookups for a given host in check_by_ssh.

= Motivation =
We're using Nagios to supervise our network, using a master-Nagios "ANU"
and two slave-Nagii :) on hosts located overseas ("UK", "US"). In order
to check wether the master-Nagios is still running, we'd like to use
check_by_ssh e.g. on host US.

Unfortunately, our master-Nagios is behind our firewall host "FW". Thus,
FW will forward a port (e.g. 2222) to port 22 (ssh) of ANU. That way we
can establish a ssh-connection from US to ANU by targeting FW, port
2222. On the other hand, the target-hostname should remain "ANU",
because we do not want to mess with our ssh-hostkeys! No problem, we
just configure ssh on US that way:

Host ANU
  port 2222

The only remaining problem was that "check_by_ssh -H ANU" tried to
double-check the host ANU by calling getaddrinfo() and it isn't able to
resolve that host, because it is hidden behind our firewall FW.

= Proposal =
I think the call to getaddrinfo() isn't necessary, and we could just
drop it without loosing functionality.

On the other hand, I understand that it improves the user interface, and
that our needs are somewhat special. So I'd like to propose an option to
turn it off.

= Patch =
Attached to this mail, you'll find a patch to the current version 1.36
of "check_by_ssh" that implements my proposal. It features an
command-line option "-g" in order not to call getaddrinfo() for the
given hostname.

We really hope to see that switch in the official branch.

Thanks alot,
Dirk Räbiger

Modern Technologies Inc.
John Henry Building
St. John's
Antigua & Barbuda
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