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#!/usr/bin/perl
#
# Shows current leases.
#
# THIS SCRIPT IS PUBLIC DOMAIN, NO RIGHTS RESERVED!
#
# I've removed the email addresses of Christian and vom to avoid
# putting them on spam lists. If either of you would like to have
# your email in here please send mail to the DHCP bugs list at ISC.
#
# 2008-07-13, Christian Hammers
#
# 2009-06-?? - added loading progress counter, pulls hostname, adjusted formatting
# vom
#
# 2013-04-22 - added option to choose lease file, made manufacture information
# optional, sar
#
# 2016-01-19 - updated to better trim the manu string and output the hostnames, sar
#
# 2016-01-18 - Mainly cosmetics. Eliminated spurious output in "parsable" mode.
# Provided for the various conventional lease file locations. (cbp)
#
# 2019-06-20 - Updated OUI_URL location. -TS
use strict;
use warnings;
use POSIX qw(strftime);
my @LEASES = ('/var/db/dhcpd.leases', '/var/lib/dhcp/dhcpd.leases', '/var/lib/dhcp3/dhcpd.leases');
my @all_leases;
my @leases;
my @OUIS = ('/usr/share/misc/oui.txt', '/usr/local/etc/oui.txt');
my $OUI_URL = 'http://standards-oui.ieee.org/oui.txt';
my $oui;
my %data;
my $opt_format = 'human';
my $opt_keep = 'active';
our $total_leases = 0;
## Return manufactorer name for specified MAC address (aa:bb:cc:dd:ee:ff).
sub get_manufactorer_for_mac($) {
my $manu = "-NA-";
if (defined $oui) {
$manu = join('-', ($_[0] =~ /^(..):(..):(..):/));
$manu = `grep -i '$manu' $oui | cut -f3`;
$manu =~ s/^\s+|\s+$//g;
}
return $manu;
}
## Read oui.txt or print warning.
sub check_oui_file() {
for my $oui_cand (@OUIS) {
if ( -r $oui_cand) {
$oui = $oui_cand;
last;
}
}
if (not defined $oui) {
print(STDERR "To get manufacturer names please download $OUI_URL ");
print(STDERR "to /usr/local/etc/oui.txt\n");
}
}
## Read current leases file into array.
sub read_dhcpd_leases() {
my $db;
for my $db_cand (@LEASES) {
if ( -r $db_cand) {
$db = $db_cand;
last;
}
}
die("Cannot find leases db") unless defined $db;
open(F, $db) or die("Cannot open $db: $!");
print("Reading leases from $db\n") if $opt_format eq 'human';
my $content = join('', <F>);
close(F);
@all_leases = split(/lease/, $content);
foreach my $lease (@all_leases) {
if ($lease =~ /^\s+([\.\d]+)\s+{.*starts \d+ ([\/\d\ \:]+);.*ends \d+ ([\/\d\ \:]+);.*ethernet ([a-f0-9:]+);/s) {
++$total_leases;
}
}
}
## Add manufactor name and sort out obsolet assignements.
sub process_leases() {
my $gm_now = strftime("%Y/%m/%d %H:%M:%S", gmtime());
my %tmp_leases; # for sorting and filtering
my $counter = $opt_format eq 'human' ? 1 : 0;
# parse entries
foreach my $lease (@all_leases) {
# skip invalid lines
next if not ($lease =~ /^\s+([\.\d]+)\s+{.*starts \d+ ([\/\d\ \:]+);.*ends \d+ ([\/\d\ \:]+);.*ethernet ([a-f0-9:]+);(.*client-hostname \"(\S+)\";)*/s);
# skip outdated lines
next if ($opt_keep eq 'active' and $3 lt $gm_now);
if ($counter) {
my $percent = (($counter / $total_leases)*100);
printf "Processing: %2d%% complete\r", $percent;
++$counter;
}
my $hostname = "-NA-";
if ($6) {
$hostname = $6;
}
my $mac = $4;
my $date_end = $3;
my %entry = (
'ip' => $1,
'date_begin' => $2,
'date_end' => $date_end,
'mac' => $mac,
'hostname' => $hostname,
'manu' => get_manufactorer_for_mac($mac),
);
$entry{'date_begin'} =~ s#\/#-#g; # long live ISO 8601
$entry{'date_end'} =~ s#\/#-#g;
if ($opt_keep eq 'all') {
push(@leases, \%entry);
} elsif (not defined $tmp_leases{$mac} or $tmp_leases{$mac}{'date_end'} gt $date_end) {
$tmp_leases{$mac} = \%entry;
}
}
# In case we used the hash to filtered
if (%tmp_leases) {
foreach (sort keys %tmp_leases) {
my $h = $tmp_leases{$_};
push(@leases, $h);
}
}
# print "\n";
}
# Output all valid leases.
sub output_leases() {
if ($opt_format eq 'human') {
printf "%-19s%-16s%-15s%-20s%-20s\n","MAC","IP","hostname","valid until","manufacturer";
print("===============================================================================================\n");
}
foreach (@leases) {
if ($opt_format eq 'human') {
printf("%-19s%-16s%-14.14s %-20s%-20s\n",
$_->{'mac'}, # MAC
$_->{'ip'}, # IP address
$_->{'hostname'}, # hostname
$_->{'date_end'}, # Date
$_->{'manu'}); # manufactor name
} else {
printf("MAC %s IP %s HOSTNAME %s BEGIN %s END %s MANUFACTURER %s\n",
$_->{'mac'},
$_->{'ip'},
$_->{'hostname'},
$_->{'date_begin'},
$_->{'date_end'},
$_->{'manu'});
}
}
}
# Commandline Processing.
sub cli_processing() {
while (my $arg = shift(@ARGV)) {
if ($arg eq '--help') {
print(
"Prints active DHCP leases.\n\n".
"Usage: $0 [options]\n".
" --help shows this help\n".
" --parsable machine readable output with full dates\n".
" --last prints the last (even if end<now) entry for every MAC\n".
" --all prints all entries i.e. more than one per MAC\n".
" --lease uses the next argument as the name of the lease file\n".
" the default is to try /var/db/dhcpd.leases then\n".
" /var/lib/dhcp/dhcpd.leases then\n".
" /var/lib/dhcp3/dhcpd.leases\n".
"\n");
exit(0);
} elsif ($arg eq '--parsable') {
$opt_format = 'parsable';
} elsif ($arg eq '--last') {
$opt_keep = 'last';
} elsif ($arg eq '--all') {
$opt_keep = 'all';
} elsif ($arg eq '--lease') {
unshift @LEASES, shift(@ARGV);
} else {
die("Unknown option $arg");
}
}
}
#
# main()
#
cli_processing();
check_oui_file();
read_dhcpd_leases();
process_leases();
output_leases();
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