#!/usr/bin/perl -w
#
# Module: vyatta_update_resolv.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) 2007 Vyatta, Inc.
# All Rights Reserved.
#
# Author: Marat Nepomnyashy
# Date: December 2007
# Description: Script to update '/etc/resolv.conf' on commit of 'system domain-search domain' config.
#
# **** End License ****
#

use strict;
use lib "/opt/vyatta/share/perl5/";


use Getopt::Long;
my $dhclient_script = 0;
GetOptions("dhclient-script=i" => \$dhclient_script);

use Vyatta::Config;
my $vc = new Vyatta::Config();

$vc->setLevel('system');
my @domains;
my $domain_name = undef;

if ($dhclient_script == 1) {
   @domains = $vc->returnOrigValues('domain-search domain');
   $domain_name = $vc->returnOrigValue('domain-name');
} else {
   @domains = $vc->returnValues('domain-search domain');
   $domain_name = $vc->returnValue('domain-name');
}

if ($dhclient_script == 0 && @domains > 0 && $domain_name && length($domain_name) > 0) {
	print STDERR "System configuration error.  Both \'domain-name\' and \'domain-search\' are specified, but only one of these mutually exclusive parameters is allowed.\n";
	print STDERR "System configuration commit aborted due to error(s).\n";
	exit(1);
}

my $doms = '';
foreach my $domain (@domains) {
	if (length($doms) > 0) {
		$doms .= ' ';
	}
	$doms .= $domain;
}

# add domain names received from dhcp client to domain search in /etc/resolv.conf if domain-name not set in CLI
if (!defined($domain_name)) {
  my @dhcp_interfaces_resolv_files = `ls /etc/ | grep resolv.conf.dhclient-new`;
  if ($#dhcp_interfaces_resolv_files >= 0) {
    for my $each_file (@dhcp_interfaces_resolv_files) {
       chomp $each_file;
       my $find_search = `grep "^search" /etc/$each_file 2> /dev/null | wc -l`;
       if ($find_search == 1) {
            my $search_string = `grep "^search" /etc/$each_file`;
            my @dhcp_domains = split(/\s+/, $search_string, 2);
            my $dhcp_domain = $dhcp_domains[1];
            chomp $dhcp_domain;
            $doms .= ' ' . $dhcp_domain;
       }
    }
  }
}

my $search = '';
if (length($doms) > 0) {
	$search = "search\t\t$doms\t\t#line generated by $0\n";
}

my $domain = '';
if ($domain_name && length($domain_name) > 0) {
	$domain = "domain\t\t$domain_name\t\t#line generated by $0\n";
}

# update /etc/resolv.conf for name-servers received from dhcp client, only done when dhclient-script calls this script
if ($dhclient_script == 1) {
  my @current_dhcp_nameservers;
  my $restart_ntp = 0;

  # code below to add new name-servers received from dhcp client

  my @dhcp_interfaces_resolv_files = `ls /etc/ | grep resolv.conf.dhclient-new`;
  if ($#dhcp_interfaces_resolv_files >= 0) {
    my $ns_count = 0;
    for my $each_file (@dhcp_interfaces_resolv_files) {
       chomp $each_file;
       my $find_nameserver = `grep nameserver /etc/$each_file 2> /dev/null | wc -l`;
       if ($find_nameserver > 0) {
            my @nameservers = `grep nameserver /etc/$each_file`;
            for my $each_nameserver (@nameservers) {
               my @nameserver = split(/ /, $each_nameserver, 2);
               my $ns = $nameserver[1];
               chomp $ns;
               $current_dhcp_nameservers[$ns_count] = $ns;
               $ns_count++;
               my @search_ns_in_resolvconf = `grep $ns /etc/resolv.conf`;
               my $ns_in_resolvconf = 0;
               if (@search_ns_in_resolvconf > 0) {
                  foreach my $ns_resolvconf (@search_ns_in_resolvconf) {
                       my @resolv_ns = split(/\s+/, $ns_resolvconf);
                       my $final_ns = $resolv_ns[1];
                       chomp $final_ns;
                       if ($final_ns eq $ns) {
                           $ns_in_resolvconf = 1;
                       }
                  }
               }
               if ($ns_in_resolvconf == 0) {
		   open (my $rf, '>>', '/etc/resolv.conf')
		       or die "$! error trying to overwrite";
		   print $rf "nameserver\t$ns\t\t#nameserver written by $0\n";
		   close $rf;
		   $restart_ntp = 1;
               }
            }
       }
    }
  }

  # code below to remove old name-servers from /etc/resolv.conf that were not received in this response from dhcp-server

  my @nameservers_dhcp_in_resolvconf = `grep 'nameserver written' /etc/resolv.conf`;
  my @dhcp_nameservers_in_resolvconf;
  my $count_nameservers_in_resolvconf = 0;
  for my $count_dhcp_nameserver (@nameservers_dhcp_in_resolvconf) {
     my @dhcp_nameserver = split(/\t/, $count_dhcp_nameserver, 3);
     $dhcp_nameservers_in_resolvconf[$count_nameservers_in_resolvconf] = $dhcp_nameserver[1];
     $count_nameservers_in_resolvconf++;
  }
  if ($#current_dhcp_nameservers < 0) {
    for my $dhcpnameserver (@dhcp_nameservers_in_resolvconf) {
        my $cmd = "sed -i '/$dhcpnameserver\t/d' /etc/resolv.conf";
        system($cmd);
        $restart_ntp = 1;
    }
  } else {
         for my $dhcpnameserver (@dhcp_nameservers_in_resolvconf) {
            my $found = 0;
            for my $currentnameserver (@current_dhcp_nameservers) {
               if ($dhcpnameserver eq $currentnameserver){
                  $found = 1;
               }
            }
            if ($found == 0) {
              my $cmd = "sed -i '/$dhcpnameserver\t/d' /etc/resolv.conf";
              system($cmd);
              $restart_ntp = 1;
            }

        }
   }
 if ($restart_ntp == 1) {
     # this corresponds to what is done in name-server/node.def as a fix for bug 1300
     my $cmd_ntp_restart = "if [ -f /etc/ntp.conf ] && grep -q '^server' /etc/ntp.conf; then /usr/sbin/invoke-rc.d ntp restart >&/dev/null; fi &";
     system($cmd_ntp_restart);
 }
}


# The following will re-write '/etc/resolv.conf' line by line,
# replacing the 'search' specifier with the latest values,
# or replacing the 'domain' specifier with the latest value.

my @resolv;
if (-e '/etc/resolv.conf') {
    open (my $f, '<', '/etc/resolv.conf')
	or die("$0:  Error!  Unable to open '/etc/resolv.conf' for input: $!\n");
    @resolv = <$f>;
    close ($f);
}


my $foundSearch = 0;
my $foundDomain = 0;

open (my $r, '>', '/etc/resolv.conf')
    or die("$0:  Error!  Unable to open '/etc/resolv.conf' for output: $!\n");

foreach my $line (@resolv) {
	if ($line =~ /^search\s/) {
		$foundSearch = 1;
		if (length($search) > 0) {
			print $r $search;
		}
	} elsif ($line =~ /^domain\s/) {
		$foundDomain = 1;
		if (length($domain) > 0) {
			print $r $domain;
		}
	} else {
		print $r $line;
	}
}
if ($foundSearch == 0 && length($search) > 0) {
	print $r $search;
}
if ($foundDomain == 0 && length($domain) > 0) {
	print $r $domain;
}

close ($r);