package Foo::FloodBlocker;

use strict;
use warnings;

use Apache2::Connection;
use Apache2::Const -compile => qw/FORBIDDEN OK/;
use IPC::Shareable ':all';

use constant { FILTERGLUE  => 'PIFt',
               FILTERSHMEM => 1048576
             };

sub handler {
   my $c = shift;
   return Apache2::Const::OK if $c->keepalives;

   my $ip = $c->remote_ip;
   my $time = time;

   no warnings 'untie';
   my ($shmem, %hash);
   $shmem = tie %hash, 'IPC::Shareable', FILTERGLUE, {  
                                  create => 0, mode => 0666, 
                                  size => FILTERSHMEM,
                                  exclusive => 0, 
                                  destroy => 0
                                                     }; 
   $ip =~ s/\./_/g;
   my $block;
   $shmem->shlock(LOCK_EX);
   if (exists $hash{$ip}) {
      if ($hash{$ip} < $time) {
         delete $hash{$ip};
      }
      else {
         $block = 1;
      }   
   }
   else {
      $hash{$ip} = $time;
   }
   $shmem->shunlock;
   untie %hash;
   undef $shmem;
   
   return Apache2::Const::FORBIDDEN if $block;
   
   Apache2::Const::OK;
}