#!/usr/local/bin/perl 
# 
# Bryan's cheesy-ass pinger script for monitoring the status of machines 
# we all know and love.  I fully realize this script is completely worthless 
# and unnecessary, but you must admit that it's handy having a seemingly 
# reliable machine like tep12 monitoring the stability of other machines 
# is pretty darn cool. 
# 
# Important note: this script needs to be run as root in order for the ICMP 
# ping to work.  Only root has the access necessary to create an ICMP ping 
# object.  You can, however, use an echo ping instead if you don't want 
# to or cannot run this as root.  See down below for further details. 
# 
# Other important notice: hosts to be pinged reside in an external 
# configuration file, which is specified on the command line.  Its contents 
# should look something like this: 
# 
#            host1.some.com:0 
#            host2.some.other.com:0 
#            host3.yet.another.org:0 
# 
# Basically, one line for each host to be monitored.  Don't try putting 
# comments or blank lines in the file or anything like that.  No extraneous 
# spaces either.  At the end of the host name, place a colon, and then the 
# number zero.  The pinger script will interpret a zero as an "unpingable" 
# host, and replace it with a number one if the host was pingable and then 
# notify whoever should be notified that it changed.  You could enter a one 
# instead of a zero, but if you put in a zero it'll mail you the first time 
# the script is run (assuming it can ping those hosts) so you'll see that 
# the script is working. 

# Needed includes to make this thing work. 
use Net::Ping; # Make sure you have this installed; if not, head over to 
               # http://www.cpan.org/ and get the latest version of the Net 
               # library, it should have Net::Ping in it. 

# Variable initialization.  Probably excessive in some cases. 
# 
# $timeout --- time (in seconds) it will wait before timing out on a ping. 
#              This variable can be increased or decreased to compensate for 
#              network stupidity.  If pinging across a WAN, a longer ping 
#              time is good.  In a LAN, short ping times are best.  Keep in 
#              mind that pinging hosts across a WAN isn't a reliable way of 
#              keeping in touch with them, since things like ICMP filtering 
#              and general network slowness can give false results. 
# 
# $target --- used for indicating which host it is going to ping.  This did 
#             not need to be set, I only have it in there out of habit from 
#             programming C code. 
# 
# $oldstate --- If this had been C code, I would have made these two 
# $newstate --- variables into macros instead.  But, it's Perl, so I 
#               used variables.  They're just values indicating different 
#               elements in the array and what those elements mean.  Nothing 
#               special or terribly important.  I did it this way for 
#               clarity. 
# 
# $notify --- who gets e-mailed when the script detects a change in the 
#             pingability of a host.  Set this to reflect the proper 
#             recipient for your implementation.  Multiple recipients can be 
#             specified in normal e-mail fashion with a comma seperating 
#             each recipient.  And be sure to put a backslash in front of 
#             each @ symbol... Perl 5 needs it there. 
# 
# $whosend --- set this to whoever the generated e-mail should be from. 
#              Normally I would say that the recipient should also be used 
#              as the sender.  I had to make two variables in case there are 
#              going to be multiple recipients since there can only be one 
#              sender. 
# 
# $sendmail --- the full path to the sendmail executable.  This can vary 
#               from platform to platform.  In the case of SGI and Sun as 
#               well (I think) it's /usr/lib/sendmail but with things like 
#               FreeBSD and Linux it seems to be /usr/sbin/sendmail most of 
#               the time.  Be sure to leave the -t option in there. 
$timeout = 120; 
$target = 0; 
$oldstate = 1; 
$newstate = 2; 
$notify = "bryan\@badideas.webicommerce.com"; 
$whosend = "bryan\@badideas.webicommerce.com"; 
$sendmail = "/usr/sbin/sendmail -t"; 

# Set this to one if you want debugging mode on. 
#$debug = 1; 
  

# This block reads in the configuration file.  The configuration file should 
# have been specified on the command line. 
open(CONFFILE, "$ARGV[0]") or die "$0: error during open(): $!\n"; 
while (<CONFFILE>) 
{ 
        ($hostname[$whichhost][$target], $hostname[$whichhost][$oldstate]) = split(/:/, $_); 
        if ($debug) # If debugging is on, read what it interprets the 
                    # previous host statuses to be. 
        { 
                print "$hostname[$whichhost][$target]:  host last marked as "; 
                if ($hostname[$whichhost][$oldstate] == 1) {print "up.\n";} 
                else {print "down.\n";} 
        } 
        ++$whichhost; 
} 
close(CONFFILE); 
  

# This creates a ping object so we can actually do pinging.  Again, you 
# have to be root to use ICMP pings.  Change the word "icmp" to "tcp" if 
# you want to do echo pinging instead, but make sure the host to be echo 
# pinged is able to echo.  This is specified in /etc/inetd.conf and carried 
# on port 7 for both TCP and UDP.  For an easy way to check, telnet to port 
# 7 on any given host and start typing at it.  It should echo what you type 
# back at you. 
# 
# You can also do UDP echo pinging instead of TCP if you want.  Just change 
# the "icmp" to "udp" instead of "tcp" and it should work, assuming UDP 
# echoing is enabled. 
$p = Net::Ping->new("icmp", $timeout); 

# Begin the actual pinging process, set the state according to the result. 
while ($whichhost) 
{ 
        --$whichhost; 
        if ($debug) {print "Pinging host $hostname[$whichhost][$target].\n";} 
        if ($p->ping($hostname[$whichhost][$target])) 
        { 
                if ($debug) {print "Host is up.\n";} 
                $hostname[$whichhost][$newstate] = 1; 
                if ($hostname[$whichhost][$newstate] != $hostname[$whichhost][$oldstate]) {$statechange = 1;} 
        } 
        else 
        { 
                if ($debug) {print "Host is down.\n";} 
                $hostname[$whichhost][$newstate] = 0; 
                if ($hostname[$whichhost][$newstate] != $hostname[$whichhost][$oldstate]) {$statechange = 1;} 
        } 
} 
  

# Now write back out the new version of the conf file, include 
# the new status values. 
open(CONFFILE, ">$ARGV[0]"); 
while ($whichhost <= $#hostname) 
{ 
        if ($debug) {print "$hostname[$whichhost][$target]:$hostname[$whichhost][$newstate]\n";} 
        print CONFFILE "$hostname[$whichhost][$target]:$hostname[$whichhost][$newstate]\n"; 
        ++$whichhost; 
} 
close(CONFFILE); 
  

# Notify the individual(s) specified in the $notify variable if the 
# states of the target hosts have changed. 
if ($statechange) 
{ 
        open(SENDMAIL, "|$sendmail") || die "$0: unable to open sendmail: $!\n"; 
        select(SENDMAIL); 
        print "To: $notify\n"; 
        print "From: System Monitoring Script <$whosend>\n"; 
        print "Subject: Network host status change.\n\n"; 
        while ($whichhost) 
        { 
                --$whichhost; 
                if ($hostname[$whichhost][$newstate] != $hostname[$whichhost][$oldstate]) 
                { 
                        if ($hostname[$whichhost][$newstate]) {print "Host $hostname[$whichhost][$target] is up.\n"} 
                        else {print "Host $hostname[$whichhost][$target] is down.\n"} 
                } 
        } 
        print "\n.\n"; 
        select(STDOUT); 
}