// Copyright (c) 2019 Intel Corporation. All rights reserved.
//
// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause

use super::Error as DeviceError;
use super::{DescriptorChain, DeviceEventT, Queue};
use net_util::{MacAddr, Tap, TapError};
use std::cmp;
use std::fs;
use std::io::{self, Write};
use std::mem;
use std::net::Ipv4Addr;
use std::os::unix::io::{AsRawFd, RawFd};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use virtio_bindings::bindings::virtio_net::*;
use vm_memory::{
    ByteValued, Bytes, GuestAddress, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryError,
    GuestMemoryMmap,
};
use vmm_sys_util::eventfd::EventFd;

type Result<T> = std::result::Result<T, Error>;

/// The maximum buffer size when segmentation offload is enabled. This
/// includes the 12-byte virtio net header.
/// http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.html#x1-1740003
const MAX_BUFFER_SIZE: usize = 65562;
const QUEUE_SIZE: usize = 256;

// The guest has made a buffer available to receive a frame into.
pub const RX_QUEUE_EVENT: DeviceEventT = 0;
// The transmit queue has a frame that is ready to send from the guest.
pub const TX_QUEUE_EVENT: DeviceEventT = 1;
// A frame is available for reading from the tap device to receive in the guest.
pub const RX_TAP_EVENT: DeviceEventT = 2;
// The device has been dropped.
pub const KILL_EVENT: DeviceEventT = 3;
// The device should be paused.
pub const PAUSE_EVENT: DeviceEventT = 4;
// Number of DeviceEventT events supported by this implementation.
pub const NET_EVENTS_COUNT: usize = 5;
// The device has been dropped.
const CTRL_QUEUE_EVENT: DeviceEventT = 0;
// Number of DeviceEventT events supported by this implementation.
const CTRL_EVENT_COUNT: usize = 3;

#[repr(C, packed)]
#[derive(Copy, Clone, Debug, Default)]
pub struct VirtioNetConfig {
    pub mac: [u8; 6],
    pub status: u16,
    pub max_virtqueue_pairs: u16,
    pub mtu: u16,
    pub speed: u32,
    pub duplex: u8,
}

// Safe because it only has data and has no implicit padding.
unsafe impl ByteValued for VirtioNetConfig {}

#[derive(Debug)]
pub enum Error {
    /// Failed to convert an hexadecimal string into an integer.
    ConvertHexStringToInt(std::num::ParseIntError),
    /// Read process MQ.
    FailedProcessMQ,
    /// Read queue failed.
    GuestMemory(GuestMemoryError),
    /// Invalid ctrl class
    InvalidCtlClass,
    /// Invalid ctrl command
    InvalidCtlCmd,
    /// Invalid descriptor
    InvalidDesc,
    /// Invalid queue pairs number
    InvalidQueuePairsNum,
    /// Error related to the multiqueue support.
    MultiQueueSupport(String),
    /// No memory passed in.
    NoMemory,
    /// No ueue pairs nummber.
    NoQueuePairsNum,
    /// Failed to read the TAP flags from sysfs.
    ReadSysfsTunFlags(io::Error),
    /// Open tap device failed.
    TapOpen(TapError),
    /// Setting tap IP failed.
    TapSetIp(TapError),
    /// Setting tap netmask failed.
    TapSetNetmask(TapError),
    /// Setting tap interface offload flags failed.
    TapSetOffload(TapError),
    /// Setting vnet header size failed.
    TapSetVnetHdrSize(TapError),
    /// Enabling tap interface failed.
    TapEnable(TapError),
}

pub struct CtrlVirtio {
    pub queue_evt: EventFd,
    pub queue: Queue,
}

impl std::clone::Clone for CtrlVirtio {
    fn clone(&self) -> Self {
        CtrlVirtio {
            queue_evt: self.queue_evt.try_clone().unwrap(),
            queue: self.queue.clone(),
        }
    }
}

impl CtrlVirtio {
    pub fn new(queue: Queue, queue_evt: EventFd) -> Self {
        CtrlVirtio { queue_evt, queue }
    }

    fn process_mq(&self, mem: &GuestMemoryMmap, avail_desc: DescriptorChain) -> Result<()> {
        let mq_desc = if avail_desc.has_next() {
            avail_desc.next_descriptor().unwrap()
        } else {
            return Err(Error::NoQueuePairsNum);
        };
        let queue_pairs = mem
            .read_obj::<u16>(mq_desc.addr)
            .map_err(Error::GuestMemory)?;
        if (queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN as u16)
            || (queue_pairs > VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX as u16)
        {
            return Err(Error::InvalidQueuePairsNum);
        }
        let status_desc = if mq_desc.has_next() {
            mq_desc.next_descriptor().unwrap()
        } else {
            return Err(Error::NoQueuePairsNum);
        };
        mem.write_obj::<u8>(0, status_desc.addr)
            .map_err(Error::GuestMemory)?;

        Ok(())
    }

    pub fn process_cvq(&mut self, mem: &GuestMemoryMmap) -> Result<()> {
        let mut used_desc_heads = [(0, 0); QUEUE_SIZE];
        let mut used_count = 0;
        if let Some(avail_desc) = self.queue.iter(&mem).next() {
            used_desc_heads[used_count] = (avail_desc.index, avail_desc.len);
            used_count += 1;
            let ctrl_hdr = mem
                .read_obj::<u16>(avail_desc.addr)
                .map_err(Error::GuestMemory)?;
            let ctrl_hdr_v = ctrl_hdr.as_slice();
            let class = ctrl_hdr_v[0];
            let cmd = ctrl_hdr_v[1];
            match u32::from(class) {
                VIRTIO_NET_CTRL_MQ => {
                    if u32::from(cmd) != VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET {
                        return Err(Error::InvalidCtlCmd);
                    }
                    if let Err(_e) = self.process_mq(&mem, avail_desc) {
                        return Err(Error::FailedProcessMQ);
                    }
                }
                _ => return Err(Error::InvalidCtlClass),
            }
        } else {
            return Err(Error::InvalidDesc);
        }
        for &(desc_index, len) in &used_desc_heads[..used_count] {
            self.queue.add_used(&mem, desc_index, len);
        }

        Ok(())
    }
}

pub fn register_listener(
    epoll_fd: RawFd,
    fd: RawFd,
    ev_type: epoll::Events,
    data: u64,
) -> std::result::Result<(), io::Error> {
    epoll::ctl(
        epoll_fd,
        epoll::ControlOptions::EPOLL_CTL_ADD,
        fd,
        epoll::Event::new(ev_type, data),
    )
}

pub fn unregister_listener(
    epoll_fd: RawFd,
    fd: RawFd,
    ev_type: epoll::Events,
    data: u64,
) -> std::result::Result<(), io::Error> {
    epoll::ctl(
        epoll_fd,
        epoll::ControlOptions::EPOLL_CTL_DEL,
        fd,
        epoll::Event::new(ev_type, data),
    )
}

pub struct NetCtrlEpollHandler {
    pub mem: GuestMemoryAtomic<GuestMemoryMmap>,
    pub kill_evt: EventFd,
    pub pause_evt: EventFd,
    pub ctrl_q: CtrlVirtio,
    pub epoll_fd: RawFd,
}

impl NetCtrlEpollHandler {
    pub fn run_ctrl(&mut self, paused: Arc<AtomicBool>) -> std::result::Result<(), DeviceError> {
        // Create the epoll file descriptor
        self.epoll_fd = epoll::create(true).map_err(DeviceError::EpollCreateFd)?;

        register_listener(
            self.epoll_fd,
            self.ctrl_q.queue_evt.as_raw_fd(),
            epoll::Events::EPOLLIN,
            u64::from(CTRL_QUEUE_EVENT),
        )
        .unwrap();
        register_listener(
            self.epoll_fd,
            self.kill_evt.as_raw_fd(),
            epoll::Events::EPOLLIN,
            u64::from(KILL_EVENT),
        )
        .unwrap();
        register_listener(
            self.epoll_fd,
            self.pause_evt.as_raw_fd(),
            epoll::Events::EPOLLIN,
            u64::from(PAUSE_EVENT),
        )
        .unwrap();

        let mut events = vec![epoll::Event::new(epoll::Events::empty(), 0); CTRL_EVENT_COUNT];

        'epoll: loop {
            let num_events = match epoll::wait(self.epoll_fd, -1, &mut events[..]) {
                Ok(res) => res,
                Err(e) => {
                    if e.kind() == std::io::ErrorKind::Interrupted {
                        continue;
                    }
                    return Err(DeviceError::EpollWait(e));
                }
            };

            for event in events.iter().take(num_events) {
                let ev_type = event.data as u16;

                match ev_type {
                    CTRL_QUEUE_EVENT => {
                        let mem = self.mem.memory();
                        if let Err(e) = self.ctrl_q.queue_evt.read() {
                            error!("failed to get ctl queue event: {:?}", e);
                        }
                        if let Err(e) = self.ctrl_q.process_cvq(&mem) {
                            error!("failed to process ctrl queue: {:?}", e);
                        }
                    }
                    KILL_EVENT => {
                        break 'epoll;
                    }
                    PAUSE_EVENT => {
                        debug!("PAUSE_EVENT received, pausing vhost-user epoll loop");
                        // We loop here to handle spurious park() returns.
                        // Until we have not resumed, the paused boolean will
                        // be true.
                        while paused.load(Ordering::SeqCst) {
                            std::thread::park();
                        }
                    }
                    _ => {
                        error!("Unknown event for virtio-net");
                    }
                }
            }
        }

        Ok(())
    }
}

#[derive(Clone)]
pub struct TxVirtio {
    pub iovec: Vec<(GuestAddress, usize)>,
    pub frame_buf: [u8; MAX_BUFFER_SIZE],
}

impl Default for TxVirtio {
    fn default() -> Self {
        Self::new()
    }
}

impl TxVirtio {
    pub fn new() -> Self {
        TxVirtio {
            iovec: Vec::new(),
            frame_buf: [0u8; MAX_BUFFER_SIZE],
        }
    }

    pub fn process_desc_chain(&mut self, mem: &GuestMemoryMmap, tap: &mut Tap, queue: &mut Queue) {
        while let Some(avail_desc) = queue.iter(&mem).next() {
            let head_index = avail_desc.index;
            let mut read_count = 0;
            let mut next_desc = Some(avail_desc);

            self.iovec.clear();
            while let Some(desc) = next_desc {
                if desc.is_write_only() {
                    break;
                }
                self.iovec.push((desc.addr, desc.len as usize));
                read_count += desc.len as usize;
                next_desc = desc.next_descriptor();
            }

            read_count = 0;
            // Copy buffer from across multiple descriptors.
            // TODO(performance - Issue #420): change this to use `writev()` instead of `write()`
            // and get rid of the intermediate buffer.
            for (desc_addr, desc_len) in self.iovec.drain(..) {
                let limit = cmp::min((read_count + desc_len) as usize, self.frame_buf.len());

                let read_result =
                    mem.read_slice(&mut self.frame_buf[read_count..limit as usize], desc_addr);
                match read_result {
                    Ok(_) => {
                        // Increment by number of bytes actually read
                        read_count += limit - read_count;
                    }
                    Err(e) => {
                        println!("Failed to read slice: {:?}", e);
                        break;
                    }
                }
            }

            let write_result = tap.write(&self.frame_buf[..read_count]);
            match write_result {
                Ok(_) => {}
                Err(e) => {
                    println!("net: tx: error failed to write to tap: {}", e);
                }
            };
            queue.add_used(&mem, head_index, 0);
        }
    }
}

#[derive(Clone)]
pub struct RxVirtio {
    pub deferred_frame: bool,
    pub deferred_irqs: bool,
    pub bytes_read: usize,
    pub frame_buf: [u8; MAX_BUFFER_SIZE],
}

impl Default for RxVirtio {
    fn default() -> Self {
        Self::new()
    }
}

impl RxVirtio {
    pub fn new() -> Self {
        RxVirtio {
            deferred_frame: false,
            deferred_irqs: false,
            bytes_read: 0,
            frame_buf: [0u8; MAX_BUFFER_SIZE],
        }
    }

    pub fn process_desc_chain(
        &mut self,
        mem: &GuestMemoryMmap,
        mut next_desc: Option<DescriptorChain>,
        queue: &mut Queue,
    ) -> bool {
        let head_index = next_desc.as_ref().unwrap().index;
        let mut write_count = 0;

        // Copy from frame into buffer, which may span multiple descriptors.
        loop {
            match next_desc {
                Some(desc) => {
                    if !desc.is_write_only() {
                        break;
                    }
                    let limit = cmp::min(write_count + desc.len as usize, self.bytes_read);
                    let source_slice = &self.frame_buf[write_count..limit];
                    let write_result = mem.write_slice(source_slice, desc.addr);

                    match write_result {
                        Ok(_) => {
                            write_count = limit;
                        }
                        Err(e) => {
                            error!("Failed to write slice: {:?}", e);
                            break;
                        }
                    };

                    if write_count >= self.bytes_read {
                        break;
                    }
                    next_desc = desc.next_descriptor();
                }
                None => {
                    warn!("Receiving buffer is too small to hold frame of current size");
                    break;
                }
            }
        }

        queue.add_used(&mem, head_index, write_count as u32);

        // Mark that we have at least one pending packet and we need to interrupt the guest.
        self.deferred_irqs = true;

        write_count >= self.bytes_read
    }
}

pub fn build_net_config_space(
    mut config: &mut VirtioNetConfig,
    mac: MacAddr,
    num_queues: usize,
    mut avail_features: &mut u64,
) {
    config.mac.copy_from_slice(mac.get_bytes());
    *avail_features |= 1 << VIRTIO_NET_F_MAC;

    build_net_config_space_with_mq(&mut config, num_queues, &mut avail_features);
}

pub fn build_net_config_space_with_mq(
    config: &mut VirtioNetConfig,
    num_queues: usize,
    avail_features: &mut u64,
) {
    let num_queue_pairs = (num_queues / 2) as u16;
    if (num_queue_pairs >= VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN as u16)
        && (num_queue_pairs <= VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX as u16)
    {
        config.max_virtqueue_pairs = num_queue_pairs;
        *avail_features |= 1 << VIRTIO_NET_F_MQ;
    }
}

fn vnet_hdr_len() -> usize {
    mem::size_of::<virtio_net_hdr_v1>()
}

fn check_mq_support(if_name: &Option<&str>, queue_pairs: usize) -> Result<()> {
    if let Some(tap_name) = if_name {
        let mq = queue_pairs > 1;
        let path = format!("/sys/class/net/{}/tun_flags", tap_name);
        let tun_flags_str = fs::read_to_string(path).map_err(Error::ReadSysfsTunFlags)?;
        let tun_flags = u32::from_str_radix(tun_flags_str.trim().trim_start_matches("0x"), 16)
            .map_err(Error::ConvertHexStringToInt)?;
        if (tun_flags & net_gen::IFF_MULTI_QUEUE != 0) && !mq {
            return Err(Error::MultiQueueSupport(String::from(
                "TAP interface supports MQ while device does not",
            )));
        } else if (tun_flags & net_gen::IFF_MULTI_QUEUE == 0) && mq {
            return Err(Error::MultiQueueSupport(String::from(
                "Device supports MQ while TAP interface does not",
            )));
        }
    }
    Ok(())
}

/// Create a new virtio network device with the given IP address and
/// netmask.
pub fn open_tap(
    if_name: Option<&str>,
    ip_addr: Option<Ipv4Addr>,
    netmask: Option<Ipv4Addr>,
    num_rx_q: usize,
) -> Result<Vec<Tap>> {
    let mut taps: Vec<Tap> = Vec::new();
    let mut ifname: String = String::new();
    let vnet_hdr_size = vnet_hdr_len() as i32;
    let flag = net_gen::TUN_F_CSUM | net_gen::TUN_F_UFO | net_gen::TUN_F_TSO4 | net_gen::TUN_F_TSO6;

    // In case the tap interface already exists, check if the number of
    // queues is appropriate. The tap might not support multiqueue while
    // the number of queues indicates the user expects multiple queues, or
    // on the contrary, the tap might support multiqueue while the number
    // of queues indicates the user doesn't expect multiple queues.
    check_mq_support(&if_name, num_rx_q)?;

    for i in 0..num_rx_q {
        let tap: Tap;
        if i == 0 {
            tap = match if_name {
                Some(name) => Tap::open_named(name, num_rx_q).map_err(Error::TapOpen)?,
                None => Tap::new(num_rx_q).map_err(Error::TapOpen)?,
            };
            if let Some(ip) = ip_addr {
                tap.set_ip_addr(ip).map_err(Error::TapSetIp)?;
            }
            if let Some(mask) = netmask {
                tap.set_netmask(mask).map_err(Error::TapSetNetmask)?;
            }
            tap.enable().map_err(Error::TapEnable)?;
            tap.set_offload(flag).map_err(Error::TapSetOffload)?;

            tap.set_vnet_hdr_size(vnet_hdr_size)
                .map_err(Error::TapSetVnetHdrSize)?;

            ifname = String::from_utf8(tap.get_if_name()).unwrap();
        } else {
            tap = Tap::open_named(ifname.as_str(), num_rx_q).map_err(Error::TapOpen)?;
            tap.set_offload(flag).map_err(Error::TapSetOffload)?;

            tap.set_vnet_hdr_size(vnet_hdr_size)
                .map_err(Error::TapSetVnetHdrSize)?;
        }
        taps.push(tap);
    }
    Ok(taps)
}