sub post_auth {
        my $gn = $RAD_REQUEST{'User-Name'};
        if ($RAD_REQUEST{'User-Name'} =~ /^[Gg][Aa][Ss][Tt][0-9]+$/) {
                my $filename = "/usr/local/etc/raddb/guests/guest_$gn.txt";
                my $currtime = time();
                my $maxtime = $currtime + 3600 * 8; # 8 hours
                if (open (my $fh, '<:encoding(UTF-8)', $filename)) {
                        while (my $row = <$fh>) {
                                chomp($row);
                                $maxtime = $row;
                        }
                        close $fh;
                } else {
                        &radiusd::radlog(L_AUTH, "New guest user $gn");
                        open (my $wfh, '>:encoding(UTF-8)', $filename) or
                                die ("Unable to write to $filename");
                        print $wfh $maxtime;
                        close $wfh;
                }
                if ($maxtime > time()) {
                        &radiusd::radlog(L_AUTH, "Accepting guest user $gn due $maxtime > $currtime");
                        return RLM_MODULE_OK;
                } else {
                        &radiusd::radlog(L_AUTH, "Rejecting guest user $gn due $maxtime < $currtime");
                        return RLM_MODULE_REJECT;
                }
                #$RAD_REPLY{'Tunnel-Medium-Type'} = "IEEE-802";
        } else {
                &radiusd::radlog(L_AUTH, "User $gn is not a guest user. Allowing.");
        }

        return RLM_MODULE_OK;
}