qpsmtpd/plugins/check_earlytalker

=head1 NAME

check_earlytalker - Check that the client doesn't talk before we send the SMTP banner

=head1 DESCRIPTION

Hooks connect, checks to see if the remote host starts talking before
we've issued a 2xx greeting.  If so, we're likely looking at a
direct-to-MX spam agent which pipelines its entire SMTP conversation,
and will happily dump an entire spam into our mail log even if later
tests deny acceptance.

Such clients gets a 450 error code.  

=head1 TODO

Make how long we wait before reading from the socket configurable
(currently 1 second)

Make the soft/hard response code configurable (currently DENYSOFT)

=cut

use IO::Select;

sub register {
  my ($self, $qp) = @_;
  $self->register_hook('connect', 'connect_handler');
}

sub connect_handler {
  my ($self, $transaction) = @_;
  my $in = new IO::Select;
  
  $in->add(\*STDIN) || return DECLINED;
  if ($in->can_read(1)) {
    $self->log(LOGDEBUG, "remote host started talking before we said hello");
    return (DENYSOFT, "Don't be rude and talk before I say hello!");
  }
  $self->log(LOGINFO,"remote host said nothing spontaneous, proceeding");
  return DECLINED;
}