send_and_recv_msg
err = send_and_recv_msg(sockfd, CMD_GET_XDP_CAP, &advertised_feature,
err = send_and_recv_msg(sockfd, CMD_START, NULL, 0);
err = send_and_recv_msg(sockfd, CMD_GET_STATS, &stats, sizeof(stats));
err = send_and_recv_msg(sockfd, CMD_STOP, NULL, 0);