#!/usr/bin/perl

# dhcphosts.pl - by dual
#
# Generates an /etc/hosts file for a
# box on a DHCP network
#
# - Simply call it in /etc/rc.local.
# - Depends on Nmap::Parser.
####################################


# Include Nmap::Parser
######################
use strict;
use Nmap::Parser;


# Declare and set variables
###########################
my $ip;
my $fqn;
my $dmain;
my $tld;
my $host;
my $path = '/usr/bin/nmap';
my $args = '-sP';
my @ips  = qw/192.168.1.100-109/;
my $ip_addr;
my $mac_addr;


# Obtain local info
###################
my @ifconfig = `/sbin/ifconfig eth1`;
foreach my $line (@ifconfig) {
  $ip = $1 if ($line =~ /inet addr:(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/);
}

open NETWK, "</etc/sysconfig/network" or die "Can't open network: $!";

while (<NETWK>) {
  $fqn = $1 if ($_ =~ /^HOSTNAME=(.+)$/);
}

close NETWK;

my @names = split (/\./, "$fqn");
$host  = $names[0];
$dmain = $names[1];
$tld   = $names[2];


# Clobber /etc/hosts
####################
open HOSTS, ">/etc/hosts" or die "Can't open hosts: $!";


# Print local info
##################
print HOSTS "# Generated by dhcphosts.pl\n\n";
print HOSTS "# Gotta have loopback\n";
print HOSTS "127.0.0.1\tlocalhost.localdomain\tlocalhost\n\n";
print HOSTS "# This box...\n";
print HOSTS "$ip\t$fqn\t$host\n\n";
print HOSTS "# Remaining network hosts\n";


# Scan, parse and print the remaining network
#############################################
my $nmap = new Nmap::Parser;
$nmap->parsescan ($path, $args, @ips);

for my $host ($nmap->all_hosts()) {
  $ip_addr  = $host->addr;
  $mac_addr = $host->mac_addr;
  if ($mac_addr =~ /.{2}:.{2}:.{2}:.{2}:.{2}:.{2}/) {
    # Fill in your MACs and hostnames here  
    if ($mac_addr =~ /XX:XX:XX:XX:XX:XX/) {
      print HOSTS "$ip_addr\thostname1.$dmain.$tld\thostname1\n";
    }
    elsif ($mac_addr =~ /XX:XX:XX:XX:XX:XX/) {
      print HOSTS "$ip_addr\thostname2.$dmain.$tld\thostname2\n";
    }
    elsif ($mac_addr =~ /XX:XX:XX:XX:XX:XX/) {
      print HOSTS "$ip_addr\thostname3.$dmain.$tld\thostname3\n";
    }
    elsif ($mac_addr =~ /XX:XX:XX:XX:XX:XX/) {
      print HOSTS "$ip_addr\thostname4.$dmain.$tld\thostname4\n";
    }
  }
}


# Clean up
##########
close HOSTS;