#!/usr/bin/perl
#
# Copyright (c) 2011 Mathieu Roy <yeupou@gnu.org>
#
#   This program is free software; you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 2 of the License, or
#   (at your option) any later version.
#
#   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.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
#   USA
#
# The original idea was to come up with a script that mounts NFS shares
# when on the relevant network.
# 
# NetworkManager crappy handling of /etc/dhcp/dhclient-*-hooks makes it
# impossible to rely on these hooks like in the past, to keep the stuff
# portable.
# 
# In /etc/network/if-up.d/, in Debian, there's already a mountnfs script
# shipped by the initscripts package.
# Instead of reinventing this, we'll just remove "noauto" option from NFS
# shares listed in /etc/fstab for the current network.

use strict;
use Socket;   

my $debug = 0;


## 
## Quickly check whether there are NFS shares listed in fstab that we may 
## want to work with: must contain nfs as filesystem and noauto option.
## 
open(FSTAB, "< /etc/fstab");
my $count = 0;
my %hosts;
while (<FSTAB>) {
    next if /^#/;
    next unless /\w/;
    next unless /\snfs/;
    next unless /noauto/;
    $count++;

    # identify the NFS host
    my $this_host = $1 if /^([^\:]*)\:/;
    $hosts{$this_host} = 1
	unless $hosts{$this_host};
}
close(FSTAB);

print "DBG: $count noauto NFS share(s) listed in /etc/fstab\n" if $debug;
exit if $count < 1;


## 
## Check whether the NFS servers mentioned resolves with a local network IP
## (I guess this script could be used to mount NFS shares over internet,
## but for security issues, I would not do such thing automatically, so I
## bother about it)
##  192.168. or 10.

$count = 0;
while (my ($this_host,) = each(%hosts)) {
    my $packed_ip = gethostbyname($this_host);
    next unless defined $packed_ip,
    my $ip = inet_ntoa($packed_ip);
    next unless $ip =~ /^192\.168\./ or $ip =~ /^10\./;
    print "DBG: $this_host DNS record exists and points to LAN $ip\n" if $debug;

    # now set this host value to 2 as valid host
    $hosts{$this_host} = 2;
    $count++;
}
    
print "DBG: $count host(s) listed in /etc/fstab available\n" if $debug;
exit if $count < 1;


##
## Now edit /etc/fstab so available NFS shares no longer get the noauto
## option.
## Mark the original lines so changes are easily reverted back.
###

use File::Copy;
use File::Temp qw(tempfile tempdir); 

$count = 0;

# Create a (secure) temporary file
my ($tempfilefh, $tempfile) = tempfile(UNLINK => 1);

open(FSTAB, "< /etc/fstab");
while (<FSTAB>) {
    # copy current fstab while removing noauto for each host
    while (my ($this_host,$is_active) = each(%hosts)) {
	next unless $is_active eq 2;
	if (/^$this_host\:/) {
	    # back up the change
	    print $tempfilefh "#CLEVERNFSS###$_" if /\,?noauto/;
	    # squish the noauto
	    $count++ if s/\,?noauto//g;
	}
    }
    print $tempfilefh $_;
}
close(FSTAB);
close($tempfilefh);

print "DBG: $count line(s) modified in /etc/fstab\n" if $debug;
exit if $count < 1;

# replace fstab with the (readable to everybody) temporary file
# (obviously, must be root to do so)
system("chmod", "a+r", $tempfile);
move($tempfile, "/etc/fstab")
    or die "unable to overwrite /etc/fstab, are you root? Exit";
print "DBG: /etc/fstab overwrote by $tempfile\n" if $debug;


# Now /etc/network/if-up.d/mountnfs should do its magic

# EOF