#!/usr/bin/perl
#
# nscan
# 
##

use Getopt::Long;
use POSIX qw(strftime);
use Time::Local;
use FindBin qw[$Bin];

$host = "/usr/bin/host";

# the core of our program

sub domainlist {
   my $domain;
   my @presorted;
   my @output;
   my $pid;

   ($domain) = @_;   
   exitclean("Could not fork!:  $!") unless defined ($pid = open(HOSTPROC,"-|"));
   if ($pid) # parent process
   {
      while(<HOSTPROC>)
      {
         if (/(\w*\.$domain)/)
         {
            push @presorted,lc($1);
         }
      }
      close(HOSTPROC) or debugprint("Child process exited with:  $?");
   
   } else { # child process
      exec($host,"-l","-a",$domain) or exitclean("Could not execute $host: $!");
   }
   @presorted = sort @presorted;
   $prev='noprevyet';
   @output=grep($_ ne $prev && ($prev = $_),@presorted);
   return @output;
}

# signal catching
sub sig_catch {
   my $signame = shift;
   print "\nRecieved SIG$signame, exiting...\n";
   exit 2;
}

# our alternative to 'die'
sub exitclean {
   my ($msg) = @_;
   print "$msg\n";
   exit 2;
}

# show program usage
sub usage {

  print "Usage: $0 [options] -t <domain>\n";
  print "\noptions:\n";
  print "\t-t <target domain> -- the domain you want to scan.\n";
  print "\t-d [directory]     -- directory to put domain maps.\n";
  print "\t-debug             -- show debug information.\n";
  print "\n\n";
  exit 2;
}

sub debugprint {
  ($msg) = @_;
  print "[debug]  $msg\n" unless (!$debug);
}

#
# Start the main program
#

$SIG{INT}=\&sig_catch;
$start_time = time;
&GetOptions("debug", \$debug,
            "t:s",\$target,
            "d:s", \$directory);

# make sure all of our input is ok
if ($target eq "") { usage(); }

if ($directory eq "") {
   printf("No output directory defined, using '$Bin'!\n");
   $directory=$Bin;
} else {
  if (-d $directory) {
   printf("Using directory:  %s\n",$directory);
  } else {
   if (mkdir($directory,0755)) {
    printf("Created output directory:  %s\n",$directory);
   } else {
    exitclean("Could not create output directory!:  $!");
   }
  }
}

chdir($directory) || exitclean("Could not change to output directory:  $!");

%master = ();
$level++;
$count = 0;

$target = lc($target);

print "TARGET = $target.dom\n" unless -e "$target.dom";
if (-e "$target.dom") {
 printf("There is a domain file for the domain '%s'\n",$target);
 open(DOM,"<$target.dom") || exitclean("Could not open domain file:  $!");
  while($host=(<DOM>)) {
   chomp($host);
   push @targets,$host;
  }
 $master{$target} = @targets;
 close(DOM);
 printf("Loaded %d hosts from $target.dom\n",scalar(@targets));
 @targets = ();
} else {
 printf("Creating initial domain list for:  %s\n",$target);
 $master{$target} = [(domainlist($target))];

 @targets = ();
 @targets = @{$master{$target}};
 open (DOM,">>$target.dom") ||
 die ("Couldnt create domain map for top domain:  $!");
   foreach $t (@targets) {  print DOM "$t\n"; }
 close(DOM);
}

debugprint("[ -- starting recursive zone transfers -- ]");
$oldcount = 1;

while ($oldcount ne $count) {
 $oldcount = $count;
 foreach $key (keys(%master)) {
   @targets = ();
   @targets = @{$master{$key}};
   debugprint(scalar(@targets) . " targets in domain $key");
   foreach $t (@targets) {
    if ($master{$t} eq "") {
     debugprint("[$count] -- scanning $t");
     $master{$t} = [(domainlist($t))];
     $count++;

# save domain file
 @hosts = ();
 @hosts = @{$master{$t}};
 if (scalar(@hosts) != 0)
 {
   open (DOM,">>$t.dom") || die "Cant open $t.dom for writing: $!"; 
   debugprint("[$count] -- writing domain file for $t");
   foreach $host (@hosts)
   {
    print DOM "$host\n";
   }
   close(DOM);
  }
# end save domain file

    }
   }
 }
}

# create our domain maps

foreach $key (keys(%master)) {
  @targets = ();
  @targets = @{$master{$key}};
  if (scalar(@targets) != 0)
  {
   open(MAP,">>$key.dom") || 
   exitclean("Could not create output file '$key.dom':  $!");
   foreach $host (@targets) { print MAP "$host\n"; }
   close(MAP) || debugprint("Could not close file '$key.dom':  $!");
  }
}