// Copyright 2019 Intel Corporation. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//
// Portions Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//
// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the THIRD-PARTY file.

mod csm;
mod device;
mod packet;
mod unix;

pub use self::device::Vsock;
pub use self::unix::VsockUnixBackend;
pub use self::unix::VsockUnixError;

use std::os::unix::io::RawFd;

use packet::VsockPacket;

mod defs {

    /// Max vsock packet data/buffer size.
    pub const MAX_PKT_BUF_SIZE: usize = 64 * 1024;

    pub mod uapi {

        /// Vsock packet operation IDs.
        /// Defined in `/include/uapi/linux/virtio_vsock.h`.
        ///
        /// Connection request.
        pub const VSOCK_OP_REQUEST: u16 = 1;
        /// Connection response.
        pub const VSOCK_OP_RESPONSE: u16 = 2;
        /// Connection reset.
        pub const VSOCK_OP_RST: u16 = 3;
        /// Connection clean shutdown.
        pub const VSOCK_OP_SHUTDOWN: u16 = 4;
        /// Connection data (read/write).
        pub const VSOCK_OP_RW: u16 = 5;
        /// Flow control credit update.
        pub const VSOCK_OP_CREDIT_UPDATE: u16 = 6;
        /// Flow control credit update request.
        pub const VSOCK_OP_CREDIT_REQUEST: u16 = 7;

        /// Vsock packet flags.
        /// Defined in `/include/uapi/linux/virtio_vsock.h`.
        ///
        /// Valid with a VSOCK_OP_SHUTDOWN packet: the packet sender will receive no more data.
        pub const VSOCK_FLAGS_SHUTDOWN_RCV: u32 = 1;
        /// Valid with a VSOCK_OP_SHUTDOWN packet: the packet sender will send no more data.
        pub const VSOCK_FLAGS_SHUTDOWN_SEND: u32 = 2;

        /// Vsock packet type.
        /// Defined in `/include/uapi/linux/virtio_vsock.h`.
        ///
        /// Stream / connection-oriented packet (the only currently valid type).
        pub const VSOCK_TYPE_STREAM: u16 = 1;

        pub const VSOCK_HOST_CID: u64 = 2;
    }
}

#[derive(Debug)]
pub enum VsockError {
    /// The vsock data/buffer virtio descriptor length is smaller than expected.
    BufDescTooSmall,
    /// The vsock data/buffer virtio descriptor is expected, but missing.
    BufDescMissing,
    /// Chained GuestMemory error.
    GuestMemory,
    /// Bounds check failed on guest memory pointer.
    GuestMemoryBounds,
    /// The vsock header descriptor length is too small.
    HdrDescTooSmall(u32),
    /// The vsock header `len` field holds an invalid value.
    InvalidPktLen(u32),
    /// A data fetch was attempted when no data was available.
    NoData,
    /// A data buffer was expected for the provided packet, but it is missing.
    PktBufMissing,
    /// Encountered an unexpected write-only virtio descriptor.
    UnreadableDescriptor,
    /// Encountered an unexpected read-only virtio descriptor.
    UnwritableDescriptor,
}
type Result<T> = std::result::Result<T, VsockError>;

/// A passive, event-driven object, that needs to be notified whenever an epoll-able event occurs.
/// An event-polling control loop will use `get_polled_fd()` and `get_polled_evset()` to query
/// the listener for the file descriptor and the set of events it's interested in. When such an
/// event occurs, the control loop will route the event to the listener via `notify()`.
///
pub trait VsockEpollListener {
    /// Get the file descriptor the listener needs polled.
    fn get_polled_fd(&self) -> RawFd;

    /// Get the set of events for which the listener wants to be notified.
    fn get_polled_evset(&self) -> epoll::Events;

    /// Notify the listener that one ore more events have occurred.
    fn notify(&mut self, evset: epoll::Events);
}

/// Any channel that handles vsock packet traffic: sending and receiving packets. Since we're
/// implementing the device model here, our responsibility is to always process the sending of
/// packets (i.e. the TX queue). So, any locally generated data, addressed to the driver (e.g.
/// a connection response or RST), will have to be queued, until we get to processing the RX queue.
///
/// Note: `recv_pkt()` and `send_pkt()` are named analogous to `Read::read()` and `Write::write()`,
///       respectively. I.e.
///       - `recv_pkt(&mut pkt)` will read data from the channel, and place it into `pkt`; and
///       - `send_pkt(&pkt)` will fetch data from `pkt`, and place it into the channel.
pub trait VsockChannel {
    /// Read/receive an incoming packet from the channel.
    fn recv_pkt(&mut self, pkt: &mut VsockPacket) -> Result<()>;

    /// Write/send a packet through the channel.
    fn send_pkt(&mut self, pkt: &VsockPacket) -> Result<()>;

    /// Checks whether there is pending incoming data inside the channel, meaning that a subsequent
    /// call to `recv_pkt()` won't fail.
    fn has_pending_rx(&self) -> bool;
}

/// The vsock backend, which is basically an epoll-event-driven vsock channel, that needs to be
/// sendable through a mpsc channel (the latter due to how `vmm::EpollContext` works).
/// Currently, the only implementation we have is `crate::virtio::unix::muxer::VsockMuxer`, which
/// translates guest-side vsock connections to host-side Unix domain socket connections.
pub trait VsockBackend: VsockChannel + VsockEpollListener + Send {}