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

use super::{
    DescriptorChain, EpollHelper, EpollHelperError, EpollHelperHandler, Queue,
    EPOLL_HELPER_EVENT_LAST,
};
use net_util::MacAddr;
use serde::ser::{Serialize, SerializeStruct, Serializer};
use std::os::unix::io::{AsRawFd, RawFd};
use std::sync::atomic::AtomicBool;
use std::sync::{Arc, Barrier};
use virtio_bindings::bindings::virtio_net::*;
use vm_memory::{
    ByteValued, Bytes, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryError, GuestMemoryMmap,
};
use vmm_sys_util::eventfd::EventFd;

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

const QUEUE_SIZE: usize = 256;

// Event available on the control queue.
const CTRL_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 1;

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

// We must explicitly implement Serialize since the structure is packed and
// it's unsafe to borrow from a packed structure. And by default, if we derive
// Serialize from serde, it will borrow the values from the structure.
// That's why this implementation copies each field separately before it
// serializes the entire structure field by field.
impl Serialize for VirtioNetConfig {
    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        let mac = self.mac;
        let status = self.status;
        let max_virtqueue_pairs = self.max_virtqueue_pairs;
        let mtu = self.mtu;
        let speed = self.speed;
        let duplex = self.duplex;

        let mut virtio_net_config = serializer.serialize_struct("VirtioNetConfig", 17)?;
        virtio_net_config.serialize_field("mac", &mac)?;
        virtio_net_config.serialize_field("status", &status)?;
        virtio_net_config.serialize_field("max_virtqueue_pairs", &max_virtqueue_pairs)?;
        virtio_net_config.serialize_field("mtu", &mtu)?;
        virtio_net_config.serialize_field("speed", &speed)?;
        virtio_net_config.serialize_field("duplex", &duplex)?;
        virtio_net_config.end()
    }
}

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

#[derive(Debug)]
pub enum Error {
    /// 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,
    /// No memory passed in.
    NoMemory,
    /// No ueue pairs number.
    NoQueuePairsNum,
}

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);
            self.queue.update_avail_event(&mem);
        }

        Ok(())
    }
}

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>,
        paused_sync: Arc<Barrier>,
    ) -> std::result::Result<(), EpollHelperError> {
        let mut helper = EpollHelper::new(&self.kill_evt, &self.pause_evt)?;
        helper.add_event(self.ctrl_q.queue_evt.as_raw_fd(), CTRL_QUEUE_EVENT)?;
        helper.run(paused, paused_sync, self)?;

        Ok(())
    }
}

impl EpollHelperHandler for NetCtrlEpollHandler {
    fn handle_event(&mut self, _helper: &mut EpollHelper, event: &epoll::Event) -> bool {
        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);
                    return true;
                }
                if let Err(e) = self.ctrl_q.process_cvq(&mem) {
                    error!("failed to process ctrl queue: {:?}", e);
                    return true;
                }
            }
            _ => {
                error!("Unknown event for virtio-net");
                return true;
            }
        }

        false
    }
}

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;
    }
}