recipes-connectivity/nftables-rules/nftables-gbmc-rules/99-gbmc.rules

table inet filter {
    map port_to_chain_map {
        type inet_service : verdict
    }
    chain output {
        type filter hook output priority filter; policy accept;
        tcp flags & (syn|ack) == (syn|ack) tcp sport vmap @port_to_chain_map
    }
}