// Copyright © 2022 Intel Corporation

//

// SPDX-License-Identifier: Apache-2.0

#![no_main]

use std::fs::File;

use std::io::{Read, Write};

use std::os::unix::io::{AsRawFd, FromRawFd};

use std::sync::Arc;

use libfuzzer_sys::{fuzz_target, Corpus};

use seccompiler::SeccompAction;

use virtio_devices::{VirtioDevice, VirtioInterrupt, VirtioInterruptType};

use virtio_queue::{Queue, QueueT};

use vm_memory::bitmap::AtomicBitmap;

use vm_memory::{Bytes, GuestAddress, GuestMemoryAtomic};

use vmm::EpollContext;

use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK};

type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;

macro_rules! align {

    ($n:expr, $align:expr) => {{

        $n.div_ceil($align) * $align

    }};

}

const TAP_INPUT_SIZE: usize = 128;

const QUEUE_DATA_SIZE: usize = 4;

const MEM_SIZE: usize = 32 * 1024 * 1024;

// Guest memory gap

const GUEST_MEM_GAP: u64 = 1 * 1024 * 1024;

// Guest physical address for the first virt queue

const BASE_VIRT_QUEUE_ADDR: u64 = MEM_SIZE as u64 + GUEST_MEM_GAP;

// Number of queues

const QUEUE_NUM: usize = 2;

// Max entries in the queue.

const QUEUE_SIZE: u16 = 256;

// Descriptor table alignment

const DESC_TABLE_ALIGN_SIZE: u64 = 16;

// Used ring alignment

const USED_RING_ALIGN_SIZE: u64 = 4;

// Descriptor table size

const DESC_TABLE_SIZE: u64 = 16_u64 * QUEUE_SIZE as u64;

// Available ring size

const AVAIL_RING_SIZE: u64 = 6_u64 + 2 * QUEUE_SIZE as u64;

// Padding size before used ring

const PADDING_SIZE: u64 = align!(AVAIL_RING_SIZE, USED_RING_ALIGN_SIZE) - AVAIL_RING_SIZE;

// Used ring size

const USED_RING_SIZE: u64 = 6_u64 + 8 * QUEUE_SIZE as u64;

// Virtio-queue size in bytes

const QUEUE_BYTES_SIZE: usize = align!(

    DESC_TABLE_SIZE + AVAIL_RING_SIZE + PADDING_SIZE + USED_RING_SIZE,

    DESC_TABLE_ALIGN_SIZE

) as usize;

fuzz_target!(|bytes: &[u8]| -> Corpus {

    if bytes.len() < TAP_INPUT_SIZE + (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM

        || bytes.len()

            > TAP_INPUT_SIZE + (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM + MEM_SIZE

    {

        return Corpus::Reject;

    }

    let (dummy_tap_frontend, dummy_tap_backend) = create_socketpair().unwrap();

    let if_name = "fuzzer_tap_name".as_bytes().to_vec();

    let tap = net_util::Tap::new_for_fuzzing(dummy_tap_frontend, if_name);

    let mut net = virtio_devices::Net::new_with_tap(

        "fuzzer_net".to_owned(),

        vec![tap],

        None,  // guest_mac

        false, // iommu

        QUEUE_NUM,

        QUEUE_SIZE,

        SeccompAction::Allow,

        None,

        EventFd::new(EFD_NONBLOCK).unwrap(),

        None,

        true,

        true,

        true,

    )

    .unwrap();

    let tap_input_bytes = &bytes[..TAP_INPUT_SIZE];

    let queue_data = &bytes[TAP_INPUT_SIZE..TAP_INPUT_SIZE + QUEUE_DATA_SIZE * QUEUE_NUM];

    let queue_bytes = &bytes[TAP_INPUT_SIZE + QUEUE_DATA_SIZE * QUEUE_NUM

        ..TAP_INPUT_SIZE + (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM];

    let mem_bytes = &bytes[TAP_INPUT_SIZE + (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) * QUEUE_NUM..];

    // Setup the virt queues with the input bytes

    let mut queues = setup_virt_queues(

        &[

            &queue_data[..QUEUE_DATA_SIZE].try_into().unwrap(),

            &queue_data[QUEUE_DATA_SIZE..QUEUE_DATA_SIZE * 2]

                .try_into()

                .unwrap(),

        ],

        BASE_VIRT_QUEUE_ADDR,

    );

    // Setup the guest memory with the input bytes

    let mem = GuestMemoryMmap::from_ranges(&[

        (GuestAddress(0), MEM_SIZE),

        (GuestAddress(BASE_VIRT_QUEUE_ADDR), queue_bytes.len()),

    ])

    .unwrap();

    if mem

        .write_slice(queue_bytes, GuestAddress(BASE_VIRT_QUEUE_ADDR))

        .is_err()

    {

        return Corpus::Reject;

    }

    if mem.write_slice(mem_bytes, GuestAddress(0 as u64)).is_err() {

        return Corpus::Reject;

    }

    let guest_memory = GuestMemoryAtomic::new(mem);

    let input_queue = queues.remove(0);

    let input_evt = EventFd::new(0).unwrap();

    let input_queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(input_evt.as_raw_fd())) };

    let output_queue = queues.remove(0);

    let output_evt = EventFd::new(0).unwrap();

    let output_queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(output_evt.as_raw_fd())) };

    // Start the thread of dummy tap backend to handle the rx and tx from the virtio-net

    let exit_evt = EventFd::new(libc::EFD_NONBLOCK).unwrap();

    let tap_backend_thread = {

        let dummy_tap_backend = dummy_tap_backend.try_clone().unwrap();

        let tap_input_bytes: [u8; TAP_INPUT_SIZE] = tap_input_bytes[..].try_into().unwrap();

        let exit_evt = exit_evt.try_clone().unwrap();

        std::thread::Builder::new()

            .name("dummy_tap_backend".to_string())

            .spawn(move || {

                tap_backend_stub(dummy_tap_backend, &tap_input_bytes, exit_evt);

            })

            .unwrap()

    };

    // Kick the 'queue' events and endpoint event before activate the net device

    input_queue_evt.write(1).unwrap();

    output_queue_evt.write(1).unwrap();

    net.activate(

        guest_memory,

        Arc::new(NoopVirtioInterrupt {}),

        vec![(0, input_queue, input_evt), (1, output_queue, output_evt)],

    )

    .unwrap();

    // Wait for the events to finish and net device worker thread to return

    net.wait_for_epoll_threads();

    // Terminate the thread for the dummy tap backend

    exit_evt.write(1).ok();

    tap_backend_thread.join().unwrap();

    return Corpus::Keep;

});

pub struct NoopVirtioInterrupt {}

impl VirtioInterrupt for NoopVirtioInterrupt {

    fn trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error> {

        Ok(())

    }

}

fn setup_virt_queues(bytes: &[&[u8; QUEUE_DATA_SIZE]], base_addr: u64) -> Vec<Queue> {

    let mut queues = Vec::new();

    for (i, b) in bytes.iter().enumerate() {

        let mut q = Queue::new(QUEUE_SIZE).unwrap();

        let desc_table_addr = base_addr + (QUEUE_BYTES_SIZE * i) as u64;

        let avail_ring_addr = desc_table_addr + DESC_TABLE_SIZE;

        let used_ring_addr = avail_ring_addr + PADDING_SIZE + AVAIL_RING_SIZE;

        q.try_set_desc_table_address(GuestAddress(desc_table_addr))

            .unwrap();

        q.try_set_avail_ring_address(GuestAddress(avail_ring_addr))

            .unwrap();

        q.try_set_used_ring_address(GuestAddress(used_ring_addr))

            .unwrap();

        q.set_next_avail(b[0] as u16); // 'u8' is enough given the 'QUEUE_SIZE' is small

        q.set_next_used(b[1] as u16);

        q.set_event_idx(b[2] % 2 != 0);

        q.set_size(b[3] as u16 % QUEUE_SIZE);

        q.set_ready(true);

        queues.push(q);

    }

    queues

}

fn create_socketpair() -> Result<(File, File), std::io::Error> {

    let mut fds = [-1, -1];

    unsafe {

        let ret = libc::socketpair(

            libc::AF_UNIX,

            libc::SOCK_STREAM | libc::SOCK_NONBLOCK,

            0,

            fds.as_mut_ptr(),

        );

        if ret == -1 {

            return Err(std::io::Error::last_os_error());

        }

    }

    let socket1 = unsafe { File::from_raw_fd(fds[0]) };

    let socket2 = unsafe { File::from_raw_fd(fds[1]) };

    Ok((socket1, socket2))

}

enum EpollEvent {

    Exit = 0,

    Rx = 1,

    Tx = 2,

    Unknown,

}

impl From<u64> for EpollEvent {

    fn from(v: u64) -> Self {

        use EpollEvent::*;

        match v {

            0 => Exit,

            1 => Rx,

            2 => Tx,

            _ => Unknown,

        }

    }

}

// Handle the rx and tx requests from the virtio-net device

fn tap_backend_stub(

    mut dummy_tap: File,

    tap_input_bytes: &[u8; TAP_INPUT_SIZE],

    exit_evt: EventFd,

) {

    let mut epoll = EpollContext::new().unwrap();

    epoll

        .add_event_custom(&exit_evt, EpollEvent::Exit as u64, epoll::Events::EPOLLIN)

        .unwrap();

    let dummy_tap_write = dummy_tap.try_clone().unwrap();

    epoll

        .add_event_custom(

            &dummy_tap_write,

            EpollEvent::Rx as u64,

            epoll::Events::EPOLLOUT,

        )

        .unwrap();

    epoll

        .add_event_custom(&dummy_tap, EpollEvent::Tx as u64, epoll::Events::EPOLLIN)

        .unwrap();

    let epoll_fd = epoll.as_raw_fd();

    let mut events = vec![epoll::Event::new(epoll::Events::empty(), 0); 3];

    loop {

        let num_events = match epoll::wait(epoll_fd, -1, &mut events[..]) {

            Ok(num_events) => num_events,

            Err(e) => match e.raw_os_error() {

                Some(libc::EAGAIN) | Some(libc::EINTR) => continue,

                _ => panic!("Unexpected epoll::wait error!"),

            },

        };

        for event in events.iter().take(num_events) {

            let dispatch_event: EpollEvent = event.data.into();

            match dispatch_event {

                EpollEvent::Exit => {

                    return;

                }

                EpollEvent::Rx => {

                    dummy_tap.write_all(tap_input_bytes).unwrap();

                    break;

                }

                EpollEvent::Tx => {

                    let mut buffer = Vec::new();

                    dummy_tap.read_to_end(&mut buffer).ok();

                    break;

                }

                _ => {

                    panic!("Unexpected Epoll event");

                }

            }

        }

    }

}