#!/usr/bin/perl
#
# Module: vyatta-dns-forwarding.pl
#
# **** License ****
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# This code was originally developed by Vyatta, Inc.
# Portions created by Vyatta are Copyright (C) 2008 Vyatta, Inc.
# All Rights Reserved.
#
# Author: Mohit Mehta
# Date: August 2008
# Description: Script to glue Vyatta CLI to dnsmasq daemon
#
# **** End License ****
#

use lib "/opt/vyatta/share/perl5/";
use VyattaConfig;
use VyattaMisc;
use Getopt::Long;

use strict;
use warnings;

my $dnsforwarding_init = '/etc/init.d/dnsmasq';
my $dnsforwarding_conf = '/etc/dnsmasq.conf';


sub dnsforwarding_restart {
    system("$dnsforwarding_init restart >&/dev/null");
    print "Setting up DNS forwarding.\n";
}

sub dnsforwarding_stop {
    system("$dnsforwarding_init stop >&/dev/null");
    print "Stopping DNS forwarding.\n";
}

sub dnsforwarding_get_constants {
    my $output;

    my $date = `date`;
    chomp $date;
    $output  = "#\n# autogenerated by vyatta-dns-forwarding.pl on $date\n#\n";
    $output .= "domain-needed\nbogus-priv\n";
    return $output;
}

sub dnsforwarding_get_values {
    my $output = '';
    my $config = new VyattaConfig;
    my $use_dnsmasq_conf = 0;

    $config->setLevel("service dns forwarding");

    my @ignore_interfaces = $config->returnValues("ignore-interface");
    if ($#ignore_interfaces >= 0) {
       foreach my $interface (@ignore_interfaces) {
          $output .= "except-interface=$interface\n";
       }
    }

    my $cache_size = $config->returnValue("cache-size");
    if (defined $cache_size) {
        $output .= "cache-size=$cache_size\n";
    }

    my @use_nameservers = $config->returnValues("name-server");
    if (@use_nameservers != 0){
        $use_dnsmasq_conf = 1;
        foreach my $cli_nameserver (@use_nameservers) {
                   $output .= "server=$cli_nameserver\n";
           }
    }

    my $use_system_nameservers = $config->exists("system");
    if (defined($use_system_nameservers)) {
	$use_dnsmasq_conf = 1;
        my $sys_config = new VyattaConfig;
        $sys_config->setLevel("system");
        my @system_nameservers = $sys_config->returnValues("name-server");
        if (@system_nameservers > 0) {
           foreach my $system_nameserver (@system_nameservers) {
                   $output .= "server=$system_nameserver\n";
           }     
        }
    }

    my @use_dhcp_nameservers = $config->returnValues("dhcp");
    if (@use_dhcp_nameservers != 0) {
	$use_dnsmasq_conf = 1;
        foreach my $interface (@use_dhcp_nameservers) {
           my $dhcp_nameserver_count=`grep nameserver /etc/resolv.conf.dhclient-new-$interface | wc -l`;
           if ($dhcp_nameserver_count > 0) {
	       my @dhcp_nameservers = `grep nameserver /etc/resolv.conf.dhclient-new-$interface`;
	       for my $each_nameserver (@dhcp_nameservers) {
	          my @nameserver = split(/ /, $each_nameserver, 2);
                  my $ns = $nameserver[1];
                  chomp $ns;
                  $output .= "server=$ns\n";
               }
           } 
        }
    }

    if ($use_dnsmasq_conf == 1) {
        $output .= "resolv-file=/etc/dnsmasq.conf\n";
    }

    return $output;
}

sub dnsforwarding_write_file {
    my ($config) = @_;

    open(my $fh, '>', $dnsforwarding_conf) || die "Couldn't open $dnsforwarding_conf - $!";
    print $fh $config;
    close $fh;
}

sub check_nameserver {

    my $cmd = `grep nameserver /etc/resolv.conf|wc -l`;
    return $cmd;
}

sub check_system_nameserver {

    my $config = new VyattaConfig;
    $config->setLevel("system");
    my @system_nameservers = $config->returnValues("name-server");
    return(@system_nameservers);

}

sub check_dhcp_nameserver {

    my $intf = shift;
    my $cmd = `grep nameserver /etc/resolv.conf.dhclient-new-$intf|wc -l`;
    return $cmd;
}

sub is_dhcp_enabled {
    my $intf = shift;

    my $config = new VyattaConfig;

    if ($intf =~ m/^eth/) {
        if ($intf =~ m/(\w+)\.(\d+)/) {
            $config->setLevel("interfaces ethernet $1 vif $2");
        } else {
            $config->setLevel("interfaces ethernet $intf");
        }
    } elsif ($intf =~ m/^br/) {
        $config->setLevel("interfaces bridge $intf");
    } else {
        #
        # currently we only support dhcp on ethernet
        # and bridge interfaces.
        #
        return 0;
    }
    my @addrs = $config->returnOrigValues("address");
    foreach my $addr (@addrs) {
        if (defined $addr && $addr eq "dhcp") {
            return 1;
        }
    }
    return 0;
}

sub check_dhcp_interface {

    my $interface = shift;

    if (!is_dhcp_enabled($interface)) {
       print "$interface is not using DHCP to get an IP address\n";
       return 0;
    }

    if (-e "/var/run/vyatta/dhclient/dhclient_release_$interface") {
       # dhcp released for the interface
       print "DHCP lease for $interface has been released.\n";
       print "Renew lease for $interface before setting this parameter.\n";
       return 0;
    }

    return 1;
}


#
# main
#

my ($update_dnsforwarding, $stop_dnsforwarding, $system_nameserver, $dhcp_interface, $dhcp_interface_nameserver);

GetOptions("update-dnsforwarding!"         => \$update_dnsforwarding,
           "stop-dnsforwarding!"           => \$stop_dnsforwarding,
           "system-nameserver!"            => \$system_nameserver,
           "dhcp-interface-nameserver=s"   => \$dhcp_interface_nameserver,
           "dhcp-interface=s"              => \$dhcp_interface);

if (defined $system_nameserver) {
    my $system_nameserver_exists = check_system_nameserver();
    if ($system_nameserver_exists < 1){
       print "Warning: No DNS servers set in system to forward queries.\n";
    }
}

if (defined $dhcp_interface_nameserver) {
    my $dhcp_interface_nameserver_exists = check_dhcp_nameserver($dhcp_interface_nameserver);
    if ($dhcp_interface_nameserver_exists < 1){
	print "Warning: No DNS servers received from DHCP server for $dhcp_interface_nameserver.\n";
    }
}

if (defined $dhcp_interface) {
    if (!check_dhcp_interface($dhcp_interface)){
        exit 1;
    }
}

if (defined $update_dnsforwarding) {
    my $config;
    my $vyatta_config = new VyattaConfig;

    $vyatta_config->setLevel("service dns forwarding");
    my $use_system_nameservers = $vyatta_config->exists("system");
    my @use_dhcp_nameservers = $vyatta_config->returnValues("dhcp");
    my @use_nameservers = $vyatta_config->returnValues("name-server");

    if (!(defined $use_system_nameservers) && (@use_dhcp_nameservers == 0) && (@use_nameservers == 0)) {
       my $nameserver_exists = check_nameserver();
       if ($nameserver_exists < 1){
           print "Warning: No DNS servers ('system set' or 'dhcp received') to forward queries.\n";
       }
    }    

    $config  = dnsforwarding_get_constants();
    $config .= dnsforwarding_get_values();
    dnsforwarding_write_file($config);
    dnsforwarding_restart();
}

if (defined $stop_dnsforwarding) {
    dnsforwarding_stop();
}

exit 0;

# end of file