Cleanup leases?

[Gene Rackow]

Jeff, 
How often does this cleaning cause problems for you?
With many systems now running local firewalls, there is the
strong possibility that a machine can not be pinged.
The result is that your system is going to remove them from
the known leases and the IP is going to be up for re-use.
I suspect this is becoming a bigger problem now that the use
of host based firewalls is becoming an available free option.


"Jeff A. Earickson" made the following keystrokes:
 >On Wed, 27 Sep 2006, Glenn Satchell wrote:
 >
 >> Date: Wed, 27 Sep 2006 22:08:19 +1000 (EST)
 >> From: Glenn Satchell <Glenn.Satchell at uniq.com.au>
 >> Reply-To: dhcp-users at isc.org
 >> To: dhcp-users at isc.org
 >> Subject: RE: Cleanup leases?
 >> 
 >> The list software strips attachments. Jeff, you need to post the script
 >> in the body of the email.
 >>
 >> regards,
 >> -glenn
 >> --
 >> Glenn Satchell     mailto:glenn.satchell at uniq.com.au | Some days we are
 >> Uniq Advances Pty Ltd         http://www.uniq.com.au | the flies;  some
 >> PO Box 70 Paddington NSW Australia 2021              | days we  are the
 >> tel:0409-458-580  tel:02-9380-6360  fax:02-9380-6416 | windscreens...
 >>
 >>> From: "Atiqur Rahman Mohammed" <amohammed at velankani.com>
 >>>
 >>> Still did not find the attachment.
 >>>
 >>> Regards,
 >>>
 >>> Atiqur Rahman Mohammed
 >>> Software Engineer
 >
 >Glenn,
 >
 >I wondered what was going on...  Here it is (round 3):
 >
 >---snip---snip---snip
 >#!/usr/bin/perl
 >#
 >#---script to remove leases for a given subnet from your DHCP lease file.
 >#---Removes free leases only in default mode (not really useful), or
 >#---"force clean" mode (-f) which will clean every free AND active
 >#---lease in the subnet EXCEPT for machines which answer a ping.
 >
 >#--- Jeff Earickson, Colby College (jaearick at colby.edu), 6/18/2004
 >
 >use Getopt::Std;	# for command line parsing
 >use Net::Ping;		# for pinging hosts
 >
 >###################
 >###--- subroutines
 >###################
 >sub usage
 >{
 > 	print STDERR "Usage: clean_leases.pl [-f] -i input -o output string\n";
 > 	print STDERR "\t-f\tremove ALL leases in a subnet, active or not\n";
 > 	print STDERR "\t\tEXCEPT machines that can be pinged\n";
 > 	print STDERR "\n";
 > 	print STDERR "\t-N\tNuke ALL leases in a subnet, active or not\n";
 > 	print STDERR "\t\tno questions asked.\n";
 > 	print STDERR "\n";
 > 	print STDERR "\"input\" is the existing dhcpd.leases file\n";
 > 	print STDERR "\"output\" is the new (cleaned) dhcpd.leases file\n";
 > 	print STDERR "\"string\" is a IP number string, eg subnet, that\n";
 > 	print STDERR "\tyou want to clean up, like 137.146.209\n";
 > 	print STDERR "\n";
 > 	print STDERR "Stop dhcp, run this program on dhcpd.leases, copy the old\n";
 > 	print STDERR "lease file to dhcpd.leases.last, put the new (cleaned)\n";
 > 	print STDERR "lease file in place, restart dhcp.\n";
 > 	exit 1;
 >}
 >
 >###################
 >###--- main routine
 >###################
 >
 >#---parse the command-line
 >getopts('fi:No:') || &usage;
 >
 >#---input and output files
 >open(FOO,"< $opt_i") || die "cannot open $opt_i";
 >open(BAR,"> $opt_o");
 >
 >if($opt_f)
 >{
 > 	print "Force cleaning $ARGV[0].  This requires pinging every\n";
 > 	print "machine in $ARGV[0], which is slow, please be patient...\n";
 >}
 >
 >if($opt_N)
 >{
 > 	print "NUCLEAR cleaning $ARGV[0].  ALL leases in this subnet REMOVED.\n";
 >}
 >
 >$cleanit = 0;
 >$freestate = 0;
 >$ncleaned = 0;
 >$fcleaned = 0;
 >$nsaved = 0;
 >$nunmatched = 0;
 >$buf="";
 >$lease = "";
 >while(<FOO>)
 >{
 > 	#---found a match on the IP string
 > 	if ($_ =~ /^lease $ARGV[0]/)
 > 	{
 > 		$ipnumber = $1 if /^lease (\S+) {/;
 > 		$cleanit = 1;
 > 		$lease = $_;
 > 	}
 >
 > 	#---lease state is free
 > 	if ($_ =~ /  binding state free;/ )
 > 	{
 > 		$freestate = 1;
 > 	}
 >
 > 	#---append info to the buffer if not end-of-lease marker
 > 	if ($_ ne "}\n" )
 > 	{
 > 		$buf .= $_;
 > 	}
 > 	#---end of the lease info.  Write to output or ignore?
 > 	else
 > 	{
 > 		#---matches IP string we are interested in
 > 		if($cleanit == 1)
 > 		{
 > 			#---zap all leases, except machines that ping
 > 			if($opt_f)
 > 			{
 > 				#---ping with ping timeout of one second
 > 				$p = Net::Ping->new();
 > 				if($p->ping($ipnumber,1))
 > 				{
 > 					print "lease $ipnumber answered ping, leaving alone.\n";
 > 					print BAR $buf."}\n";
 > 					$nsaved++;
 > 				}
 > 				else
 > 				{
 > 					#print "force cleaning lease in $ARGV[0]\n";
 > 					$fcleaned++;
 > 				}
 > 				$p->close();
 > 			}
 > 			#--- Nuclear cleaning option, even live machines
 > 			elsif($opt_N)
 > 			{
 > 				#print "Nuclear cleaning lease in $ARGV[0]\n";
 > 				$fcleaned++;
 > 			}
 > 			#---only zap free leases (default)
 > 			else
 > 			{
 > 				#---free state so do NOT save the lease info
 > 				if($freestate == 1)
 > 				{
 > 					#print "cleaning free lease in $ARGV[0]\n";
 > 					$ncleaned++;
 > 				}
 > 				#---active lease: save info to output file
 > 				else
 > 				{
 > 					#print "saving active lease in $ARGV[0]\n";
 > 					print BAR $buf."}\n";
 > 					$nsaved++;
 > 				}
 > 			}
 > 		}
 > 		#---no match to IP string, save info to output file
 > 		else
 > 		{
 > 			print BAR $buf."}\n";
 > 			$buf="";
 > 			$nunmatched++;
 > 		}
 > 		$cleanit=0;
 > 		$freestate=0;
 > 		$buf="";
 > 		$lease = "";
 > 	}
 >}
 >if($fcleaned > 0)
 >{
 > 	print "force cleaned $fcleaned leases in $ARGV[0], $nsaved saved\n";
 >}
 >else
 >{
 > 	print "$ncleaned leases in $ARGV[0] cleaned, $nsaved saved\n";
 >}
 >print "$nunmatched leases unmatched\n";
 >---snip---snip---snip
 >
 >Jeff Earickson
 >Colby College
 >
 >