# net.rs - source
Source of the Rust file `/home/runner/.cargo/git/checkouts/virtio-drivers-4fdfaa862bcdc399/f30d426/src/net.rs`.
Keywords: rust, rustlang, rust-lang

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    use core::mem::{size_of, MaybeUninit};

    use super::*;
    use bitflags::*;
    use core::hint::spin_loop;
    use log::*;
    use volatile::{ReadOnly, Volatile};

    /// The virtio network device is a virtual ethernet card.
    ///
    /// It has enhanced rapidly and demonstrates clearly how support for new
    /// features are added to an existing device.
    /// Empty buffers are placed in one virtqueue for receiving packets, and
    /// outgoing packets are enqueued into another for transmission in that order.
    /// A third command queue is used to control advanced filtering features.
    pub struct VirtIONet<'a> {
        header: &'static mut VirtIOHeader,
        mac: EthernetAddress,
        recv_queue: VirtQueue<'a>,
        send_queue: VirtQueue<'a>,
    }

    impl VirtIONet<'_> {
        /// Create a new VirtIO-Net driver.
        pub fn new(header: &'static mut VirtIOHeader) -> Result<Self> {
            header.begin_init(|features| {
                let features = Features::from_bits_truncate(features);
                info!("Device features {:?}", features);
                let supported_features = Features::MAC | Features::STATUS;
                (features & supported_features).bits()
            });
            // read configuration space
            let config = unsafe { &mut *(header.config_space() as *mut Config) };
            let mac = config.mac.read();
            debug!("Got MAC={:?}, status={:?}", mac, config.status.read());

            let queue_num = 2; // for simplicity
            let recv_queue = VirtQueue::new(header, QUEUE_RECEIVE, queue_num)?;
            let send_queue = VirtQueue::new(header, QUEUE_TRANSMIT, queue_num)?;

            header.finish_init();

            Ok(VirtIONet {
                header,
                mac,
                recv_queue,
                send_queue,
            })
        }

        /// Acknowledge interrupt.
        pub fn ack_interrupt(&mut self) -> bool {
            self.header.ack_interrupt()
        }

        /// Get MAC address.
        pub fn mac(&self) -> EthernetAddress {
            self.mac
        }

        /// Whether can send packet.
        pub fn can_send(&self) -> bool {
            self.send_queue.available_desc() >= 2
        }

        /// Whether can receive packet.
        pub fn can_recv(&self) -> bool {
            self.recv_queue.can_pop()
        }

        /// Receive a packet.
        pub fn recv(&mut self, buf: &mut [u8]) -> Result<usize> {
            let mut header = MaybeUninit::<Header>::uninit();
            let header_buf = unsafe { (*header.as_mut_ptr()).as_buf_mut() };
            self.recv_queue.add(&[], &[header_buf, buf])?;
            self.header.notify(QUEUE_RECEIVE as u32);
            while !self.recv_queue.can_pop() {
                spin_loop();
            }

            let (_, len) = self.recv_queue.pop_used()?;
            // let header = unsafe { header.assume_init() };
            Ok(len as usize - size_of::<Header>())
        }

        /// Send a packet.
        pub fn send(&mut self, buf: &[u8]) -> Result {
            let header = unsafe { MaybeUninit::<Header>::zeroed().assume_init() };
            self.send_queue.add(&[header.as_buf(), buf], &[])?;
            self.header.notify(QUEUE_TRANSMIT as u32);
            while !self.send_queue.can_pop() {
                spin_loop();
            }
            self.send_queue.pop_used()?;
            Ok(())
        }
    }

    bitflags! {
        struct Features: u64 {
            /// Device handles packets with partial checksum.
            /// This "checksum offload" is a common feature on modern network cards.
            const CSUM = 1 << 0;
            /// Driver handles packets with partial checksum.
            const GUEST_CSUM = 1 << 1;
            /// Control channel offloads reconfiguration support.
            const CTRL_GUEST_OFFLOADS = 1 << 2;
            /// Device maximum MTU reporting is supported.
            ///
            /// If offered by the device, device advises driver about the value of
            /// its maximum MTU. If negotiated, the driver uses mtu as the maximum
            /// MTU value.
            const MTU = 1 << 3;
            /// Device has given MAC address.
            const MAC = 1 << 5;
            /// Device handles packets with any GSO type. (legacy)
            const GSO = 1 << 6;
            /// Driver can receive TSOv4.
            const GUEST_TSO4 = 1 << 7;
            /// Driver can receive TSOv6.
            const GUEST_TSO6 = 1 << 8;
            /// Driver can receive TSO with ECN.
            const GUEST_ECN = 1 << 9;
            /// Driver can receive UFO.
            const GUEST_UFO = 1 << 10;
            /// Device can receive TSOv4.
            const HOST_TSO4 = 1 << 11;
            /// Device can receive TSOv6.
            const HOST_TSO6 = 1 << 12;
            /// Device can receive TSO with ECN.
            const HOST_ECN = 1 << 13;
            /// Device can receive UFO.
            const HOST_UFO = 1 << 14;
            /// Driver can merge receive buffers.
            const MRG_RXBUF = 1 << 15;
            /// Configuration status field is available.
            const STATUS = 1 << 16;
            /// Control channel is available.
            const CTRL_VQ = 1 << 17;
            /// Control channel RX mode support.
            const CTRL_RX = 1 << 18;
            /// Control channel VLAN filtering.
            const CTRL_VLAN = 1 << 19;
            ///
            const CTRL_RX_EXTRA = 1 << 20;
            /// Driver can send gratuitous packets.
            const GUEST_ANNOUNCE = 1 << 21;
            /// Device supports multiqueue with automatic receive steering.
            const MQ = 1 << 22;
            /// Set MAC address through control channel.
            const CTL_MAC_ADDR = 1 << 23;

            // device independent
            const RING_INDIRECT_DESC = 1 << 28;
            const RING_EVENT_IDX = 1 << 29;
            const VERSION_1 = 1 << 32; // legacy
        }
    }

    bitflags! {
        struct Status: u16 {
            const LINK_UP = 1;
            const ANNOUNCE = 2;
        }
    }

    bitflags! {
        struct InterruptStatus : u32 {
            const USED_RING_UPDATE = 1 << 0;
            const CONFIGURATION_CHANGE = 1 << 1;
        }
    }

    #[repr(C)]
    #[derive(Debug)]
    struct Config {
        mac: ReadOnly<EthernetAddress>,
        status: ReadOnly<Status>,
    }

    type EthernetAddress = [u8; 6];

    // virtio 5.1.6 Device Operation
    #[repr(C)]
    #[derive(Debug)]
    struct Header {
        flags: Volatile<Flags>,
        gso_type: Volatile<GsoType>,
        hdr_len: Volatile<u16>, // cannot rely on this
        gso_size: Volatile<u16>,
        csum_start: Volatile<u16>,
        csum_offset: Volatile<u16>,
        // payload starts from here
    }

    unsafe impl AsBuf for Header {}

    bitflags! {
        struct Flags: u8 {
            const NEEDS_CSUM = 1;
            const DATA_VALID = 2;
            const RSC_INFO   = 4;
        }
    }

    #[repr(u8)]
    #[derive(Debug, Copy, Clone, Eq, PartialEq)]
    enum GsoType {
        NONE = 0,
        TCPV4 = 1,
        UDP = 3,
        TCPV6 = 4,
        ECN = 0x80,
    }

    const QUEUE_RECEIVE: usize = 0;
    const QUEUE_TRANSMIT: usize = 1;