#!perl -Tw

=head1 NAME

noop_counter - disconnect after too many consecutive NOOPs, example plugin for the hook_noop()

=head1 DESCRIPTION

The B<noop_counter> counts the number of consecutive C<NOOP> commands given
by a client and disconnects after a given number. 

Any other command than a C<NOOP> resets the counter.

One argument may be given: the number of C<NOOP>s after which the client will
be disconnected.

=head1 NOTE

This plugin should be loaded early to be able to reset the counter on any other
command.

=cut

sub register {
    my ($self, $qp, @args) = @_;
    $self->{_noop_count} = 0;
    $self->{_max_noop}   = 3;
    if ($args[0] && $args[0] =~ /^\d+$/) {
        $self->{_max_noop} = shift @args;
    }
}

sub hook_noop {
    my ($self, $transaction, @args) = @_;
    ++$self->{_noop_count};
    ### the following block is not used, RFC 2821 says we SHOULD ignore 
    ### any arguments... so we MAY return an error if we want to :-) 
    # return (DENY, "Syntax error, NOOP does not take any arguments")
    #   if $args[0];
    
    if ($self->{_noop_count} >= $self->{_max_noop}) {
        return (DENY_DISCONNECT, 
		"Stop wasting my time, too many consecutive NOOPs");
    }
    return (DECLINED);
}

sub reset_noop_counter {
   $_[0]->{_noop_count} = 0;
   return (DECLINED);
}

# and bind the counter reset to the hooks, QUIT not useful here:
*hook_helo = *hook_ehlo =       # HELO / EHLO
    *hook_mail =                # MAIL FROM: 
    *hook_rcpt =                # RCPT TO:
    *hook_data =                # DATA
    *hook_reset_transaction =   # RSET
    *hook_vrfy =                # VRFY
    *hook_help =                # HELP
        \&reset_noop_counter;