function downstream_import_filter(int ASN) {
    if !is_valid() then return false;
    if delete(bgp_path, DOWNSTREAM_ASN).len != 0 then return false;
    pub_add_communities(ASN, 20);
    pub_preprocess_communities();
    bgp_local_pref = 500 - bgp_path.len * 10;
    pub_route_controller_specific();
    return true;
}

function downstream_export_filter(int ASN) {
    pub_process_path();
    if !is_valid() then return false;
    pub_add_communities(ASN, 30);
    if pub_process_communities(ASN, 20) then return true;
    else return false;
}