net186-config/lib/10-community-transit.conf

function pub_add_communities(int ASN; int PeerType) {
    # DIRECT PEER
    if (PeerType=0) then {
        bgp_large_community.add((LOCAL_ASN, 110, 0));
        bgp_large_community.add((LOCAL_ASN, 110, 2));

    # PEER via IX
    } else if (PeerType=1) then {
        bgp_large_community.add((LOCAL_ASN, 110, 0));
        bgp_large_community.add((LOCAL_ASN, 110, 1));

    # UPSTREAM
    }else if (PeerType=10) then {
        bgp_large_community.add((LOCAL_ASN, 110, 10));

    # DOWNSTREAM
    } else if (PeerType=20) then {
        bgp_large_community.add((LOCAL_ASN, 110, 20));
    }

    # Finished (LOCAL_ASN, 110, *);

    if (LOCAL_ASN, 120, POP) ~ bgp_large_community then bgp_large_community.add((LOCAL_ASN, 120, POP));
    if (LOCAL_ASN, 121, REGION) ~ bgp_large_community then bgp_large_community.add((LOCAL_ASN, 121, REGION));

    # Finished (LOCAL_ASN, 120~130, *);
}

function pub_preprocess_communities() {
    if (LOCAL_ASN, 115, 1) ~ bgp_large_community then bgp_path.prepend(bgp_path.last);
    if (LOCAL_ASN, 115, 3) ~ bgp_large_community then {
        bgp_path.prepend(bgp_path.last);
        bgp_path.prepend(bgp_path.last);
        bgp_path.prepend(bgp_path.last);
    }
    if (LOCAL_ASN, 115, 5) ~ bgp_large_community then {
        bgp_path.prepend(bgp_path.last);
        bgp_path.prepend(bgp_path.last);
        bgp_path.prepend(bgp_path.last);
        bgp_path.prepend(bgp_path.last);
        bgp_path.prepend(bgp_path.last);
    }
    # Finished (LOCAL_ASN, 115, *);
}

function pub_process_communities(int ASN; int PeerType) {

    if (LOCAL_ASN, 125, POP) ~ bgp_large_community then {
        bgp_community.add((65535, 65282));
    }

    if (LOCAL_ASN, 126, REGION) ~ bgp_large_community then {
        bgp_community.add((65535, 65283));
    }

    if (65535, 65281) ~ bgp_community then return false;
    if (65535, 65282) ~ bgp_community then return false;
    if (65535, 65283) ~ bgp_community then return false;
    
    if (LOCAL_ASN, 2, ASN) ~ bgp_large_community then return false;

    # PEER
    if (PeerType<10) then {
        if (LOCAL_ASN, 1, 1) ~ bgp_large_community then return false;

    # UPSTREAM
    } else if (PeerType=10) then {
        if (LOCAL_ASN, 1, 0) ~ bgp_large_community then return false;

    # DOWNSTREAM
    } else if (PeerType=20) then {
        if (LOCAL_ASN, 1, 2) ~ bgp_large_community then return false;
    }

}

function transit_import_filter(int ASN) {
    if !is_valid() then return false;
    pub_add_communities(ASN, 10);
    pub_preprocess_communities();
    return true;
}

function transit_export_filter(int ASN) {
    if !is_valid() then return false;
    # Delete Self eBGP Confed Path.
    bgp_path.delete([4200000000..4225479999]);
    pub_process_communities(ASN, 10);
    if bgp_path.last !~ DOWNSTREAM_ASN then return false;
    return true;
}