#!/usr/bin/perl
#
#  This code is intended to update the modules installed within each
# Xen guest domain to the named version.
#
#  It should be fairly safe, but I make no promises - hence why this
# is an example.
#
# Steve
# --
#

use strict;
use warnings;

use File::Path qw/ rmtree  /;
use File::Temp qw/ tempdir /;


my $modules = shift;
if ( ! defined( $modules ) )
{
    print <<EOF;

 Usage: $0 <modules>

  eg: $0 2.6.18.xx|/usr/lib/modules/nn.nn.nn-xen

EOF
  exit;
}


#
#  Make sure the path is fully qualified.
#
if ( $modules !~ /^[\/\\]/ )
{
    $modules = "/lib/modules/" . $modules;
}


#
#  Make sure the module directory exists.
#
if ( ! -d $modules )
{
    print "The modules directory $modules doesn't exist.\n";
    exit;
}


#
#  OK now we have the modules so we need to:
#
#  0.  Read our configuration file.
#  1.  Find each xen guest.
#  2.  Ensure it isn't running (TODO)
#  3.  Mount the disk image.
#  4.  Remove existing modules, and copy in the specified ones.
#
#


my %CONFIG;
readConfigurationFile( "/etc/xen-tools/xen-tools.conf" );


foreach my $guest ( findGuests() )
{
    print "Attempting to update guest: $guest\n";

    #
    #  Create a temporary directory to mount the disk upon.
    #
    my $tmp = tempdir( CLEANUP => 1 );

    #
    # Mount the disk.
    #
    if ( $CONFIG{'dir'} )
    {
        # The loopback image.
        my $img =  $CONFIG{'dir'} . "/domains/" . $guest . "/disk.img";
        system( "mount -o loop $img $tmp" );
    }
    elsif ( $CONFIG{'lvm'} )
    {
        # The LVM volume
        my $img = "/dev/" . $CONFIG{'lvm'} . "/$guest-disk";
        system( "mount $img $tmp" );
    }
    else
    {
        print "Unhandled disk format - can't mount\n";
        next;
    }


    #
    #  We've got it mounted.
    #
    print "\tMounted disk image.\n";

    # make sure we have a directory
    if ( ! -d $tmp . "/lib/modules" )
    {
        print "\tMissing modules.  Skipping\n";
        next;
    }
    #
    #  Remove the existing module directories.
    #
    `rm -rf  $tmp/lib/modules`;
    mkdir $tmp . "/lib/modules";
    print "\tRemoved existing modules\n";

    #
    #  Copy existing directory.
    #
    if ( -d $tmp . "/lib/modules" )
    {
        `cp -R $modules $tmp/lib/modules/`;
        print "\tCopied over $modules\n";
    }
    else
    {
        print "No module directory .. weirdness\n";
    }

    #
    #  Unmount
    #
    system( "umount $tmp" );
    print "\tUnmounted disk image.\n\n";
}




=begin doc

  Find each xen guest upon the system.

=end doc

=cut

sub findGuests
{
    my @results;

    #
    #  Assume xen-tools.
    #
    foreach my $file ( glob( "/etc/xen/*.cfg" ) )
    {
        #
        #  Find the name.
        #
        open( INPUT, "<" , $file );
        foreach my $line ( <INPUT> )
        {
            chomp( $line );
            if ( $line =~ /name\s*=\s*['"]([^'"]+)["']/ )
            {
                push @results, $1;
            }
        }
        close( INPUT );
    }
    return( sort( @results ) );
}




=begin doc

  Read the configuration file specified.

=end doc

=cut

sub readConfigurationFile
{
    my ($file) = ( @_ );

    open( FILE, "<", $file ) or die "Cannot read file '$file' - $!";

    my $line       = "";

    while (defined($line = <FILE>) )
    {
        chomp $line;
        if ($line =~ s/\\$//)
        {
            $line .= <FILE>;
            redo unless eof(FILE);
        }

        # Skip lines beginning with comments
        next if ( $line =~ /^([ \t]*)\#/ );

        # Skip blank lines
        next if ( length( $line ) < 1 );

        # Strip trailing comments.
        if ( $line =~ /(.*)\#(.*)/ )
        {
            $line = $1;
        }

        # Find variable settings
        if ( $line =~ /([^=]+)=([^\n]+)/ )
        {
            my $key = $1;
            my $val = $2;

            # Strip leading and trailing whitespace.
            $key =~ s/^\s+//;
            $key =~ s/\s+$//;
            $val =~ s/^\s+//;
            $val =~ s/\s+$//;

            # Store value.
            $CONFIG{ $key } = $val;
        }
    }

    close( FILE );
}