#!/usr/local/perl5/bin/perl
use strict;
use diagnostics;
$|++;

$ENV{PATH} = "/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/
+sbin";

use CGI qw(:all delete_all escapeHTML);

if (my $session = param('session')) { # returning to pick up session d
+ata
  my $cache = get_cache_handle();
  my $data = $cache->get($session);
  unless ($data and ref $data eq "ARRAY") { # something is wrong
    show_form();
    exit 0;
  }
  print header;
  print start_html(-title => "Traceroute Results",
                   ($data->[0] ? () :
                   (-head => ["<meta http-equiv=refresh content=5>"]))
+);
  print h1("Traceroute Results");
  print pre(escapeHTML($data->[1]));
  print p(i("... working ...")) unless $data->[0];
  print end_html;
} elsif (my $host = param('host')) { # returning to select host
  if ($host =~ /^([a-zA-Z0-9.\-]{1,100})\z/) { # create a session
    $host = $1;                 # untainted now
    print h1("Yes");
    my $session = get_session_id();
    my $cache = get_cache_handle();
    $cache->set($session, [0, ""]); # no data yet
    if (my $pid = fork) {       # parent does
      delete_all();             # clear parameters
      param('session', $session);
      print redirect(self_url());
    } elsif (defined $pid) {    # child does
      close STDOUT;             # so parent can go on
      unless (open F, "-|") {
        open STDERR, ">&=1";
        exec "/usr/sbin/traceroute", $host;
        die "Cannot execute traceroute: $!";
      }
      my $buf = "";
      while (<F>) {
        $buf .= $_;
        $cache->set($session, [0, $buf]);
      }
      $cache->set($session, [1, $buf]);
      exit 0;
    } else {
      die "Cannot fork: $!";
    }
  } else {
    show_form();
  }
} else {                        # display form
  show_form();
}

exit 0;

sub show_form {
  print header, start_html("Traceroute"), h1("Traceroute");
  print start_form;
  print submit('traceroute to this host:'), " ", textfield('host');
  print end_form, end_html;
}

sub get_cache_handle {
  require Cache::FileCache;
  Cache::FileCache->new
      ({
        namespace => 'traceroute',
        username => 'nobody',
        default_expires_in => '30 minutes',
        auto_purge_interval => '4 hours',
       });
}

sub get_session_id {
    require Digest::MD5;
    Digest::MD5::md5_hex(Digest::MD5::md5_hex(time().{}.rand().$$));
}
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