Re: Mon and Heatbeat - Dhcpd

[David M Nolan]

On Mon, 10 Feb 2003, Diallo Moussa wrote:

> So i eard that i could use Mon. But with i didn't find a script to check
> a DHCP service....

I wrote a script for monitoring DHCP servers.  I'm attaching it to this
message.  It uses the Net::DHCP::Watch perl module, which you can get from
CPAN, to send DHCP INFORM messages to each server given on the command
line.

A few things to note are:
It uses ifconfig to determine the monitoring host's IP address and
Ethernet address.  If you aren't running on a Linux machine, you may wish
to change that.

And if the monitoring host isn't listed in the DHCP
server's configuration, I don't know what will happen.

With ISC's DHCPD, during periods of high load the dhcp server may not
respond within the 30 second timeout.  So you will want to have an
alertafter configuration specified, so that you won't get false alerts.

Since the script just does an INFORM transaction, this won't detect a case
where a pool of dynamic addresses is fully utilized.  Actually detecting
that would require significantly more work.

-David Nolan
 Network Software Developer
 Carnegie Mellon University
 Computing Services
#!/usr/bin/perl -w 

# verify that a DHCP server is operating.
#
# usage: dhcp.monitor [host ...]
#
# Uses Net::DHCP::Watch to send a DHCP inform message to each of the servers
# listed on the command line, and then waits up to 30 seconds for a response.
#

# Copyright (c) 2000-2002 Carnegie Mellon University. All rights reserved.
# Redistribution and use in source and binary forms, with or without
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#
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#    documentation and/or other materials provided with the distribution.
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# PERFORMANCE OF THIS SOFTWARE.



use Net::DHCP::Watch;

$Client = qx[ /sbin/ifconfig eth0 | /bin/sed 's/:/ /' | /bin/grep "inet addr" | 
/bin/awk '{print \$3}' ];
chomp($Client);
$Ether  = qx[ /sbin/ifconfig eth0 | /bin/grep HWaddr | /bin/awk '{print \$5}'];
chomp($Ether);


foreach $host (@ARGV) {

    eval {
        my $dhcpw = new Net::DHCP::Watch({
                                          client => $Client,
                                          server => $host,
                                          ether  => $Ether,
                                          timeout => 30,
                                         });
        
        $dhcpw->watch();

        my $s = $dhcpw->status();

        if (!$s->{Ok}) {
            push @failures, $host;
            push @longerr, "$host: DHCP INFORM request failed";
        }
    };

    if ($EVAL_ERROR && ($EVAL_ERROR =~ /Timeout/ )) {
        push @failures, $host;
        push @longerr, "$host: Request timed out.";
    } elsif ($EVAL_ERROR) {
        push @longerr, "$host: $EVAL_ERROR";
        push @failures, $host;
    }
}

if (!@failures) {
    exit 0;
}

print join(" ", @failures),"\n";
print join("\n", @longerr), "\n";
exit scalar @failures;