You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/kerla/exts/virtio_net
    
    the code of the file until where you have to start completion: //! A virtio-net device driver.
#![no_std]

extern crate alloc;

#[macro_use]
extern crate kerla_api;

use alloc::boxed::Box;
use alloc::sync::Arc;
use core::mem::size_of;
use kerla_api::driver::register_driver_prober;
use kerla_api::net::receive_ethernet_frame;
use memoffset::offset_of;

use virtio::device::{IsrStatus, Virtio, VirtqDescBuffer, VirtqUsedChain};
use virtio::transports::{
    virtio_mmio::VirtioMmio, virtio_pci_legacy::VirtioLegacyPci,
    virtio_pci_modern::VirtioModernPci, VirtioAttachError, VirtioTransport,
};

use kerla_api::address::VAddr;
use kerla_api::arch::PAGE_SIZE;
use kerla_api::driver::{
    attach_irq,
    net::{register_ethernet_driver, EthernetDriver, MacAddress},
    DeviceProber, Driver,
};
use kerla_api::driver::{pci::PciDevice, VirtioMmioDevice};
use kerla_api::mm::{alloc_pages, AllocPageFlags};
use kerla_api::sync::SpinLock;
use kerla_utils::alignment::align_up;

const VIRTIO_NET_F_MAC: u64 = 1 << 5;

const VIRTIO_NET_QUEUE_RX: u16 = 0;
const
    
    pub fn new(transport: Arc<dyn VirtioTransport>) -> Result<VirtioNet, VirtioAttachError> {
        let mut virtio = Virtio::new(transport);
        virtio.initialize(VIRTIO_NET_F_MAC, 2 /* RX and TX queues. */)?;

        // Read the MAC address.
        let mut mac_addr = [0; 6];
        for (i, byte) in mac_addr.iter_mut().enumerate() {
            *byte = virtio.read_device_config8((offset_of!(VirtioNetConfig, mac) + i) as u16);
        }
        info!(
            "virtio-net: MAC address is {:02x}:{:02x}:{:02x}:{:02x}:{:02x}:{:02x}",
            mac_addr[0], mac_addr[1], mac_addr[2], mac_addr[3], mac_addr[4], mac_addr[5],
        );

        let tx_ring_len = virtio.virtq(VIRTIO_NET_QUEUE_RX).num_descs() as usize;
        let rx_ring_len = virtio.virtq(VIRTIO_NET_QUEUE_TX).num_descs() as usize;
        let tx_buffer = alloc_pages(
            (align_up(PACKET_LEN_MAX * tx_ring_len, PAGE_SIZE)) / PAGE_SIZE,
            AllocPageFlags::KERNEL,
        )
        .unwrap()
        .as_vaddr();
        let rx_buffer = alloc_pages(
            (align_up(PACKET_LEN_MAX * rx_ring_len, PAGE_SIZE)) / PAGE_SIZE,
            AllocPageFlags::KERNEL,
        )
        .unwrap()
        .as_vaddr();

        let rx_virtq = virtio.virtq_mut(VIRTIO_NET_QUEUE_RX);
        for i in 0..rx_ring_len {
            rx_virtq.enqueue(&[VirtqDescBuffer::WritableFromDevice {
                addr: rx_buffer.add(i * PACKET_LEN_MAX).as_paddr(),
                len: PACKET_LEN_MAX,
            }])
        }

        Ok(VirtioNet {
            mac_addr: MacAddress::new(mac_addr),
            virtio,
            tx_buffer,
            _rx_buffer: rx_buffer,
            tx_ring_len,
            tx_ring_index: 0,
        })
    }