问Linux，理解setsockopt() PACKET_FANOUT用于网络扩展

EN

void start_af_packet_capture(std::string interface_name, int fanout_group_id) {

    // setup_socket() calls socket() (using SOCK_RAW) to created the socketFD,
    // setsockopt() to enable promisc mode on the NIC,
    // bind() to bind the socketFD to NIC,
    // and setsockopt() again to set PACKET_FANOUT + PACKET_FANOUT_CPU
    int packet_socket = setup_socket(interface_name, fanout_group_id); 

    if (packet_socket == -1) {
        printf("Can't create socket\n");
        return;
    }

    unsigned int capture_length = 1500;
    char buffer[capture_length];

    while (true) {
        received_packets++;

        int readed_bytes = read(packet_socket, buffer, capture_length); 

        // printf("Got %d bytes from interface\n", readed_bytes);

        consume_pkt((u_char*)buffer, readed_bytes);

        if (readed_bytes < 0) {
            break;
        }
    }
} 

...

bool use_multiple_fanout_processes = true;

// Could get some speed up on NUMA servers
bool execute_strict_cpu_affinity = false;

int main() {
     boost::thread speed_printer_thread( speed_printer );

    int fanout_group_id = getpid() & 0xffff;

    if (use_multiple_fanout_processes) {
        boost::thread_group packet_receiver_thread_group;

        unsigned int num_cpus = 8;
        for (int cpu = 0; cpu < num_cpus; cpu++) {
            boost::thread::attributes thread_attrs;

            if (execute_strict_cpu_affinity) {
                cpu_set_t current_cpu_set;

                int cpu_to_bind = cpu % num_cpus;
                CPU_ZERO(&current_cpu_set);
                // We count cpus from zero
                CPU_SET(cpu_to_bind, &current_cpu_set);

                int set_affinity_result = pthread_attr_setaffinity_np(thread_attrs.native_handle(), sizeof(cpu_set_t), &current_cpu_set);

                if (set_affinity_result != 0) {
                    printf("Can't set CPU affinity for thread\n");
                } 
            }

            packet_receiver_thread_group.add_thread(
                new boost::thread(thread_attrs, boost::bind(start_af_packet_capture, "eth6", fanout_group_id))
            );
        }

        // Wait all processes for finish
        packet_receiver_thread_group.join_all();
    } else {
        start_af_packet_capture("eth6", 0);
    }

    speed_printer_thread.join();
}