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#!/usr/bin/perl
=head1 NAME
check_loop - Detect mail loops
=head1 DESCRIPTION
This plugin detects loops by counting "Received" and "Delivered-To"
header lines. It's a kluge but it duplicates what qmail-smtpd does,
and it does at least prevent messages from looping forever.
=head1 CONFIGURATION
Takes one optional parameter, the maximum number of "hops" ("Received"
and lines plus "Delivered-To" lines) allowed. The default is 100, the
same as in qmail-smtpd.
=head1 AUTHOR
Written by Keith C. Ivey
=head1 LICENSE
Released to the public domain, 17 June 2005.
=cut
use Qpsmtpd::DSN;
sub init {
my ($self, $qp, @args) = @_;
$self->{_max_hops} = $args[0] || 100;
if ( $self->{_max_hops} !~ /^\d+$/ ) {
$self->log(LOGWARN, "Invalid max_hops value -- using default");
}
$self->log(LOGWARN, "Ignoring additional arguments") if @args > 1;
}
sub hook_data_post {
my ($self, $transaction) = @_;
my $hops = 0;
$hops++ for $transaction->header->get('Received'),
$transaction->header->get('Delivered-To');
if ( $hops >= $self->{_max_hops} ) {
# default of too_many_hops is DENY, see comment in POD of Qpsmtpd::DSN
return Qpsmtpd::DSN->too_many_hops();
}
return DECLINED;
}
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