CAN, GPIO, RNG vhost-devices for virtio-loopback [v6]quillback_16.92.0quillback/16.92.016.92.0

This patch adds key components of the viritio-loopback architecture:
- kernel-module-virtio-loopback: the virtio loopback kernel driver
- CAN, GPIO and RNG vhost-user devices from meta-virtualization (commit a215d8320edee0a317a6511e7e2efa5bba867486)

Notes:
- libgpiod, comes from meta-openembedded commit 3029554ceb0b0bb52a8d8ec3f0a75c5113662fe6
- cleaned eg-virt from unused drivers (kernel-module-virtio-video)

Bug-AGL: SPEC-4834

V2 changes:
- related meta-virtualization commit message added in the cover letter
- updated libgpio recipe to v2.1
- SPEC reference added in cover letter

v3
- add vhost-device-can preliminary version. This is placed here with
  the objective to share the link when proposing the new device to
  the rust-vmm/vhost-device community
- remove cargo-update-recipe-crates includes in bb file because it is
  not supported by the rust mixin layer
- vhost-device folder README changes

v4
- fixed libgpiod required version
- tested ref hw and qemu x86/64 builds
- vsock, scsi and i2c rust devices removed from the build as they
  are not yet integrated in virtiod-loopback
- cleaned-up kernel modules kernel-module-virtio-video and
  gstreamer1.0-plugins-bad
- virtio-loopback-driver set to 2-or-later

v5
- Merge with Jan-Simon version v4:
   - remove broken kernel-module-virtio-video
   - use FEATURE_PACKAGES instead of IMAGE_INSTALL:append
   - rename virtio-loopback-driver.bb to
     kernel-module-virtio-loopback_git.bb for consistency

v6
- adding version in the title
- removing MODULE_GIT_REPOSITORY in kernel-modules

Change-Id: Id6cc58e777b9edad03b6c50d0dddaac8601edeaf
Signed-off-by: Michele Paolino <m.paolino@virtualopensystems.com>
Signed-off-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>

4 files changed, 1192 insertions, 0 deletions

diff --git a/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/backend.rs b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/backend.rs
new file mode 100644
index 00000000..177c76cc
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/backend.rs
@@ -0,0 +1,170 @@
+// VIRTIO CAN Emulation via vhost-user
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use log::{error, info, warn};
+use std::process::exit;
+use std::sync::{Arc, RwLock};
+use std::thread::{spawn, JoinHandle};
+
+use clap::Parser;
+use thiserror::Error as ThisError;
+use vhost::{vhost_user, vhost_user::Listener};
+use vhost_user_backend::VhostUserDaemon;
+use vm_memory::{GuestMemoryAtomic, GuestMemoryMmap};
+
+use crate::can::{CanController};
+use crate::vhu_can::VhostUserCanBackend;
+
+pub(crate) type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug, ThisError)]
+/// Errors related to low level CAN helpers
+pub(crate) enum Error {
+    #[error("Invalid socket count: {0}")]
+    SocketCountInvalid(usize),
+    #[error("Failed to join threads")]
+    FailedJoiningThreads,
+    #[error("Could not create can controller: {0}")]
+    CouldNotCreateCanController(crate::can::Error),
+    #[error("Could not create can backend: {0}")]
+    CouldNotCreateBackend(crate::vhu_can::Error),
+    #[error("Could not create daemon: {0}")]
+    CouldNotCreateDaemon(vhost_user_backend::Error),
+}
+
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+struct CanArgs {
+    /// Location of vhost-user Unix domain socket. This is suffixed by 0,1,2..socket_count-1.
+    #[clap(short, long)]
+    socket_path: String,
+
+    /// A can device name to be used for reading (ex. vcan, can0, can1, ... etc.)
+    #[clap(short = 'i', long)]
+    can_in: String,
+
+    /// A can device name to be used for writing (ex. vcan, can0, can1, ... etc.)
+    #[clap(short = 'o', long)]
+    can_out: String,
+
+    /// Number of guests (sockets) to connect to.
+    #[clap(short = 'c', long, default_value_t = 1)]
+    socket_count: u32,
+}
+
+#[derive(PartialEq, Debug)]
+struct CanConfiguration {
+    socket_path: String,
+    socket_count: u32,
+    can_in: String,
+    can_out: String,
+}
+
+impl TryFrom<CanArgs> for CanConfiguration {
+    type Error = Error;
+
+    fn try_from(args: CanArgs) -> Result<Self> {
+
+        if args.socket_count == 0 {
+            return Err(Error::SocketCountInvalid(0));
+        }
+
+		let can_in = args.can_in.trim().to_string();
+		let can_out = args.can_out.trim().to_string();
+
+        Ok(CanConfiguration {
+            socket_path: args.socket_path,
+			socket_count: args.socket_count,
+            can_in,
+            can_out,
+        })
+    }
+}
+
+fn start_backend(args: CanArgs) -> Result<()> {
+
+	println!("start_backend function!\n");
+
+    let config = CanConfiguration::try_from(args).unwrap();
+    let mut handles = Vec::new();
+
+    for _ in 0..config.socket_count {
+        let socket = config.socket_path.to_owned();
+        let can_in = config.can_in.to_owned();
+        let can_out = config.can_out.to_owned();
+
+        let handle: JoinHandle<Result<()>> = spawn(move || loop {
+            // A separate thread is spawned for each socket and can connect to a separate guest.
+            // These are run in an infinite loop to not require the daemon to be restarted once a
+            // guest exits.
+            //
+            // There isn't much value in complicating code here to return an error from the
+            // threads, and so the code uses unwrap() instead. The panic on a thread won't cause
+            // trouble to other threads/guests or the main() function and should be safe for the
+            // daemon.
+
+            let controller =
+                CanController::new(can_in.clone(), can_out.clone()).map_err(Error::CouldNotCreateCanController)?;
+			let shared_controller_1 =  Arc::new(RwLock::new(controller));
+			let shared_controller_2 =  shared_controller_1.clone();
+            let vu_can_backend = Arc::new(RwLock::new(
+                VhostUserCanBackend::new(shared_controller_1).map_err(Error::CouldNotCreateBackend)?,
+            ));
+			let _read_hanlde = CanController::start_read_thread(shared_controller_2);
+
+            let mut daemon = VhostUserDaemon::new(
+                String::from("vhost-device-can-backend"),
+                vu_can_backend.clone(),
+                GuestMemoryAtomic::new(GuestMemoryMmap::new()),
+            )
+            .map_err(Error::CouldNotCreateDaemon)?;
+
+			/* Start the read thread -- need to handle it after termination */
+			let vring_workers = daemon.get_epoll_handlers();
+			vu_can_backend.read()
+						  .unwrap()
+						  .set_vring_worker(&vring_workers[0]);
+
+            let listener = Listener::new(socket.clone(), true).unwrap();
+            daemon.start(listener).unwrap();
+
+            match daemon.wait() {
+                Ok(()) => {
+                    info!("Stopping cleanly.");
+                }
+                Err(vhost_user_backend::Error::HandleRequest(
+                    vhost_user::Error::PartialMessage | vhost_user::Error::Disconnected,
+                )) => {
+                    info!("vhost-user connection closed with partial message. If the VM is shutting down, this is expected behavior; otherwise, it might be a bug.");
+                }
+                Err(e) => {
+                    warn!("Error running daemon: {:?}", e);
+                }
+            }
+
+            // No matter the result, we need to shut down the worker thread.
+            vu_can_backend.read().unwrap().exit_event.write(1).unwrap();
+        });
+
+        handles.push(handle);
+    }
+
+    for handle in handles {
+        handle.join().map_err(|_| Error::FailedJoiningThreads)??;
+    }
+
+    Ok(())
+}
+
+pub(crate) fn can_init() {
+    env_logger::init();
+	println!("Can_init function!");
+    if let Err(e) = start_backend(CanArgs::parse()) {
+        error!("{e}");
+        exit(1);
+    }
+}
diff --git a/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/can.rs b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/can.rs
new file mode 100644
index 00000000..228266f6
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/can.rs
@@ -0,0 +1,264 @@
+// CAN backend device
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use log::{warn, error};
+use std::sync::{Arc, RwLock};
+
+use thiserror::Error as ThisError;
+use vm_memory::{ByteValued, Le16};
+
+extern crate socketcan;
+use socketcan::{
+	CanFdSocket, CanFdFrame, CanAnyFrame, EmbeddedFrame, Socket,
+	Frame, StandardId,
+};
+
+use std::thread::{JoinHandle, spawn};
+use vmm_sys_util::eventfd::{EFD_NONBLOCK, EventFd};
+
+extern crate queues;
+use queues::*;
+
+use crate::vhu_can::{VirtioCanFrame, VIRTIO_CAN_STATUS_OK};
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Copy, Clone, Debug, PartialEq, ThisError)]
+/// Errors related to low level gpio helpers
+pub(crate) enum Error {
+    //#[error("Can not enabled yet")]
+    //CanNotEnabled,
+    #[error("Can open socket operation failed")]
+    CanSocketFailed,
+    #[error("Can write socket operation failed")]
+    CanSocketWriteFailed,
+    #[error("Can read socket operation failed")]
+    CanSocketReadFailed,
+    #[error("Pop can element operation failed")]
+    CanPopFailed,
+    #[error("Creating Eventfd for CAN events failed")]
+	CanEventFdFailed,
+    #[error("CanQueueFailed")]
+    CanQueueFailed,
+}
+
+/* CAN flags to determine type of CAN Id */
+pub(crate) const VIRTIO_CAN_FLAGS_EXTENDED: u32 = 0x8000;
+pub(crate) const VIRTIO_CAN_FLAGS_FD: u32 = 0x4000;
+pub(crate) const VIRTIO_CAN_FLAGS_RTR: u32 = 0x2000;
+
+pub(crate) const VIRTIO_CAN_TX: u16 = 0x0001;
+pub(crate) const VIRTIO_CAN_RX: u16 = 0x0101;
+
+pub(crate) const CAN_EFF_FLAG: u32 = 0x80000000; /* EFF/SFF is set in the MSB */
+pub(crate) const CAN_RTR_FLAG: u32 = 0x40000000; /* remote transmission request */
+pub(crate) const CAN_ERR_FLAG: u32 = 0x20000000; /* error message frame */
+
+pub(crate) const CAN_SFF_MASK: u32 = 0x000007FF; /* standard frame format (SFF) */
+pub(crate) const CAN_EFF_MASK: u32 = 0x1FFFFFFF; /* extended frame format (EFF) */
+
+//pub(crate) const CAN_FRMF_BRS: u32 = 0x01; /* bit rate switch (2nd bitrate for data) */
+//pub(crate) const CAN_FRMF_ESI: u32 = 0x02; /* error state ind. of transmitting node */
+pub(crate) const CAN_FRMF_TYPE_FD: u32 = 0x10; /* internal bit ind. of CAN FD frame */
+pub(crate) const CAN_ERR_BUSOFF: u32 = 0x00000040; /* bus off */
+
+/// Virtio Can Configuration
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
+#[repr(C)]
+pub(crate) struct VirtioCanConfig {
+	/* CAN controller status */
+    pub(crate) status: Le16,
+}
+
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioCanConfig {}
+
+#[derive(Debug)]
+pub(crate) struct CanController {
+    config: VirtioCanConfig,
+    pub can_in_name: String,
+    pub can_out_name: String,
+	can_out_socket: CanFdSocket,
+	pub rx_event_fd: EventFd,
+	rx_fifo: Queue<VirtioCanFrame>,
+}
+
+impl CanController {
+    // Creates a new controller corresponding to `device`.
+    pub(crate) fn new(can_in_name: String, can_out_name: String) -> Result<CanController> {
+
+        let can_in_name = can_in_name.to_owned();
+		println!("can_in_name: {:?}", can_in_name);
+
+        let can_out_name = can_out_name.to_owned();
+		println!("can_out_name: {:?}", can_out_name);
+
+		let can_out_socket = Self::open_can_sockets(can_out_name.clone());
+
+		let rx_fifo = Queue::new();
+
+		let rx_efd = EventFd::new(EFD_NONBLOCK).map_err(|_| Error::CanEventFdFailed)?;
+
+        Ok(CanController {
+            config: VirtioCanConfig {
+                status: 0x0.into(),
+            },
+            can_in_name,
+            can_out_name,
+			can_out_socket,
+			rx_event_fd: rx_efd,
+			rx_fifo
+        })
+    }
+
+	pub fn print_can_frame (canframe: VirtioCanFrame) {
+		println!("canframe.msg_type 0x{:x}", canframe.msg_type.to_native());
+        println!("canframe.can_id 0x{:x}", canframe.can_id.to_native());
+        println!("canframe.length {}", canframe.length.to_native());
+        println!("canframe.flags 0x{:x}", canframe.flags.to_native());
+		if canframe.length.to_native() == 0 {
+			println!("[]");
+			return;
+		}
+        print!("[");
+        let last_elem = canframe.length.to_native() as usize - 1;
+        for (index, sdu) in canframe.sdu.iter().enumerate() {
+            print!("0x{:x}, ", sdu);
+          if index == last_elem {
+              print!("0x{:x}", sdu);
+			  break;
+          }
+        }
+        println!("]");
+	}
+
+	/* FIXME: This thread is not handle after termination */
+	pub fn start_read_thread (controller: Arc<RwLock<CanController>>) -> JoinHandle<Result<()>> {
+		spawn(move || {
+				CanController::read_can_socket(controller)
+			}
+		)
+	}
+
+    pub fn push(&mut self, rx_elem: VirtioCanFrame) -> Result<()> {
+		match self.rx_fifo.add(rx_elem) {
+			Ok(_) => Ok(()), // Successfully added, so return Ok(())
+			_ => Err(Error::CanQueueFailed), // Handle other errors
+		}
+    }
+
+    pub fn pop(&mut self) -> Result<VirtioCanFrame> {
+		match self.rx_fifo.remove() {
+    	    Ok(item) => Ok(item),
+    	    _ => Err(Error::CanPopFailed),
+    	}
+    }
+
+	fn open_can_sockets (can_out_name: String) -> CanFdSocket {
+	    let can_out_socket = match CanFdSocket::open(&can_out_name) {
+			Ok(socket) => socket,
+	        Err(_) => {
+	            warn!("Error opening CAN socket");
+	            panic!("Failed to open CAN socket.");
+				//return Err(Error::CanSocketFailed);
+	        }
+	    };
+
+		can_out_socket
+	}
+
+	pub fn read_can_socket (controller: Arc<RwLock<CanController>>) -> Result<()> {
+		let can_in_name = &controller.read().unwrap().can_in_name.clone();
+		dbg!("Start reading from {} socket!", &can_in_name);
+	    let socket = match CanFdSocket::open(&can_in_name) {
+			Ok(socket) => socket,
+	        Err(_) => {
+	            warn!("Error opening CAN socket");
+				return Err(Error::CanSocketFailed);
+	        }
+	    };
+
+		// Receive CAN messages
+	    loop {
+			if let Ok(frame) = socket.read_frame() {
+
+				let mut controller = controller.write().unwrap();
+			    match frame {
+					CanAnyFrame::Normal(frame) => {
+        			    // Regular CAN frame
+        			    println!("Received CAN message: {:?}", frame);
+        			}
+        			CanAnyFrame::Fd(frame) => {
+        			    // CAN FD frame
+        			    println!("Received CAN FD message: {:?}", frame);
+
+						let read_can_frame = VirtioCanFrame {
+							msg_type: VIRTIO_CAN_RX.into(),
+							can_id: frame.raw_id().into(),
+							length:	(frame.data().len() as u16).into(),
+							reserved: 0.into(),
+							flags: frame.id_flags().bits().into(),
+							sdu: {
+								let mut sdu_data: [u8; 64] = [0; 64];
+								for i in 0..frame.data().len() {
+								    sdu_data[i] = frame.data()[i];
+								}
+							    sdu_data
+							},
+						};
+
+						match controller.push(read_can_frame) {
+							Ok(_) => warn!("New Can frame was received"),
+	    				    Err(_) => {
+	    				        warn!("Error read/push CAN frame");
+								return Err(Error::CanSocketReadFailed);
+	    				    }
+	    				}
+        			}
+        			CanAnyFrame::Remote(frame) => {
+        			    // Remote CAN frame
+        			    println!("Received Remote CAN message: {:?}", frame);
+        			}
+        			CanAnyFrame::Error(frame) => {
+        			    // Error frame
+        			    println!("Received Error frame: {:?}", frame);
+        			}
+			    }
+
+				controller.rx_event_fd.write(1).unwrap();
+	        }
+	    }
+	}
+
+    pub(crate) fn config(&self) -> &VirtioCanConfig {
+		log::trace!("Get config\n");
+        &self.config
+    }
+
+    pub(crate) fn operation(&self, tx_request: VirtioCanFrame) -> Result<u8> {
+		log::trace!("Can operation\n");
+
+	    // Create a CAN frame with a specific CAN-ID and the data buffer
+		let can_id = StandardId::new(tx_request.can_id.to_native().try_into().unwrap()).unwrap();
+		let data_len = tx_request.length.to_native() as usize;
+
+		let data: Vec<u8> = tx_request.sdu.iter().cloned().take(data_len).collect();
+	    let frame = CanFdFrame::new(can_id, &data).unwrap();
+
+	    // Send the CAN frame
+	    let write_result = self.can_out_socket.write_frame(&frame); 
+	    match write_result {
+			Ok(_) => Ok(VIRTIO_CAN_STATUS_OK),
+	        Err(_) => {
+	            warn!("Error write CAN socket");
+				Err(Error::CanSocketWriteFailed)
+	        }
+	    }
+    }
+}
+
diff --git a/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/main.rs b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/main.rs
new file mode 100644
index 00000000..e89934ea
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/main.rs
@@ -0,0 +1,26 @@
+// VIRTIO CAN Emulation via vhost-user
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+#[cfg(target_env = "gnu")]
+mod backend;
+#[cfg(target_env = "gnu")]
+mod can;
+#[cfg(target_env = "gnu")]
+mod vhu_can;
+
+#[cfg(target_env = "gnu")]
+fn main() {
+	println!("Hello to main vhost-user-can");
+    backend::can_init()
+}
+
+// Rust vmm container (https://github.com/rust-vmm/rust-vmm-container) doesn't
+// have tools to do a musl build at the moment, and adding that support is
+// tricky as well to the container. Skip musl builds until the time pre-built
+// libgpiod library is available for musl.
+#[cfg(target_env = "musl")]
+fn main() {}
diff --git a/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/vhu_can.rs b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/vhu_can.rs
new file mode 100644
index 00000000..6aa12488
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-can/vhost-device-can-0.1.0/src/vhu_can.rs
@@ -0,0 +1,732 @@
+// vhost device can
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use log::{warn, error};
+use std::mem::size_of;
+use std::slice::from_raw_parts;
+use std::sync::{Arc, RwLock};
+use std::{
+    convert,
+    io::{self, Result as IoResult},
+};
+use std::os::fd::AsRawFd;
+use thiserror::Error as ThisError;
+use vhost::vhost_user::message::{VhostUserProtocolFeatures, VhostUserVirtioFeatures};
+use vhost_user_backend::{VhostUserBackendMut, VringRwLock, VringT};
+use virtio_bindings::bindings::virtio_config::{VIRTIO_F_NOTIFY_ON_EMPTY, VIRTIO_F_VERSION_1};
+use virtio_bindings::bindings::virtio_ring::{
+    VIRTIO_RING_F_EVENT_IDX, VIRTIO_RING_F_INDIRECT_DESC,
+};
+use virtio_queue::{DescriptorChain, QueueOwnedT};
+use vm_memory::{
+    ByteValued, Bytes, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryLoadGuard,
+    GuestMemoryMmap, Le16, Le32,
+};
+use vmm_sys_util::epoll::EventSet;
+use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK};
+use crate::can::{
+	CanController, CAN_EFF_FLAG, CAN_RTR_FLAG, CAN_ERR_FLAG, CAN_SFF_MASK,
+	CAN_EFF_MASK, VIRTIO_CAN_FLAGS_FD, VIRTIO_CAN_FLAGS_RTR,
+	VIRTIO_CAN_FLAGS_EXTENDED, VIRTIO_CAN_TX, VIRTIO_CAN_RX,
+	CAN_FRMF_TYPE_FD, CAN_ERR_BUSOFF,
+};
+use vhost_user_backend::VringEpollHandler;
+
+/// Feature bit numbers
+pub const VIRTIO_CAN_F_CAN_CLASSIC: u16 = 0;
+pub const VIRTIO_CAN_F_CAN_FD: u16 = 1;
+//pub const VIRTIO_CAN_F_LATE_TX_ACK: u16 = 2;
+pub const VIRTIO_CAN_F_RTR_FRAMES: u16 = 3;
+
+/// Possible values of the status field
+pub const VIRTIO_CAN_STATUS_OK: u8 = 0x0;
+pub const VIRTIO_CAN_STATUS_ERR: u8 = 0x1;
+
+/// CAN Control messages
+const VIRTIO_CAN_SET_CTRL_MODE_START: u16 = 0x0201;
+const VIRTIO_CAN_SET_CTRL_MODE_STOP: u16 = 0x0202;
+
+/// Virtio configuration
+const QUEUE_SIZE: usize = 64;
+const NUM_QUEUES: usize = 3;
+
+/// Queues
+const TX_QUEUE: u16 = 0;
+const RX_QUEUE: u16 = 1;
+const CTRL_QUEUE: u16 = 2;
+const BACKEND_EFD: u16 = 4;
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Copy, Clone, Debug, PartialEq, ThisError)]
+/// Errors related to vhost-device-gpio-daemon.
+pub(crate) enum Error {
+    #[error("Failed to handle event, didn't match EPOLLIN")]
+    HandleEventNotEpollIn,
+    #[error("Failed to handle unknown event")]
+    HandleEventUnknown,
+    #[error("Received unexpected write only descriptor at index {0}")]
+    UnexpectedWriteOnlyDescriptor(usize),
+    #[error("Received unexpected readable descriptor at index {0}")]
+    UnexpectedReadableDescriptor(usize),
+    #[error("Invalid descriptor count {0}")]
+    UnexpectedDescriptorCount(usize),
+    #[error("Invalid descriptor size, expected: {0}, found: {1}")]
+    UnexpectedDescriptorSize(usize, u32),
+    #[error("Descriptor not found")]
+    DescriptorNotFound,
+    #[error("Descriptor read failed")]
+    DescriptorReadFailed,
+    #[error("Descriptor write failed")]
+    DescriptorWriteFailed,
+    #[error("Failed to send notification")]
+    NotificationFailed,
+    #[error("Failed to create new EventFd")]
+    EventFdFailed,
+    #[error("Unknown can message type: {0}")]
+	UnexpectedCanMsgType(u16),
+    #[error("RTR frames not negotiated")]
+	UnexpectedRtrFlag,
+    #[error("Can FD frames not negotiated")]
+	UnexpectedFdFlag,
+    #[error("Classic CAN frames not negotiated")]
+	UnexpectedClassicFlag,
+}
+
+impl convert::From<Error> for io::Error {
+    fn from(e: Error) -> Self {
+        io::Error::new(io::ErrorKind::Other, e)
+    }
+}
+
+/// Virtio CAN Request / Response messages
+///
+/// The response message is a stream of bytes, where first byte represents the
+/// status, and rest is message specific data.
+
+#[derive(Copy, Clone, Default)]
+#[repr(C)]
+struct VirtioCanTxResponse {
+    result: i8,
+}
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioCanTxResponse {}
+
+#[derive(Copy, Clone, Debug)]
+#[repr(C)]
+pub struct VirtioCanFrame {
+	pub msg_type: Le16,
+    pub length: Le16,   /* 0..8 CC, 0..64 CAN­FD, 0..2048 CAN­XL, 12 bits */
+	pub reserved: Le32, /* May be needed in part for CAN XL priority */
+    pub flags: Le32,
+    pub can_id: Le32,
+    pub sdu: [u8; 64],
+}
+
+impl Default for VirtioCanFrame {
+    fn default() -> Self {
+        VirtioCanFrame {
+            msg_type: Le16::default(),
+            length: Le16::default(),
+            reserved: Le32::default(),
+            flags: Le32::default(),
+            can_id: Le32::default(),
+            sdu: [0; 64], // Initialize "asd" with default value (0 in this case)
+        }
+    }
+}
+
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioCanFrame {}
+
+#[derive(Copy, Clone, Default)]
+#[repr(C)]
+struct VirtioCanCtrlRequest {
+	msg_type: Le16,
+}
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioCanCtrlRequest {}
+
+#[derive(Copy, Clone, Default)]
+#[repr(C)]
+struct VirtioCanCtrlResponse {
+    result: i8,
+}
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioCanCtrlResponse {}
+
+pub(crate) struct VhostUserCanBackend {
+    controller: Arc<RwLock<CanController>>,
+	acked_features: u64,
+    event_idx: bool,
+    pub(crate) exit_event: EventFd,
+    mem: Option<GuestMemoryAtomic<GuestMemoryMmap>>,
+}
+
+type CanDescriptorChain = DescriptorChain<GuestMemoryLoadGuard<GuestMemoryMmap<()>>>;
+
+impl VhostUserCanBackend {
+    pub(crate) fn new(controller: Arc<RwLock<CanController>>) -> Result<Self> {
+        Ok(VhostUserCanBackend {
+            controller: controller,
+            event_idx: false,
+			acked_features: 0x0,
+            exit_event: EventFd::new(EFD_NONBLOCK).map_err(|_| Error::EventFdFailed)?,
+            mem: None,
+        })
+    }
+
+	fn check_features (&self, features: u16) -> bool {
+		(self.acked_features & (1 << features)) != 0
+	}
+
+    fn process_ctrl_requests(
+		&self,
+		requests: Vec<CanDescriptorChain>,
+		vring: &VringRwLock
+	) -> Result<bool> {
+		dbg!("process_ctrl_requests");
+
+        if requests.is_empty() {
+            return Ok(true);
+        }
+
+        for desc_chain in requests {
+			let descriptors: Vec<_> = desc_chain.clone().collect();
+
+            if descriptors.len() < 1 {
+				warn!("Error::UnexpectedDescriptorCount");
+                return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+            }
+
+			println!("descriptors.len(): {:?}", descriptors.len());
+
+            let desc_request = descriptors[0];
+            if desc_request.is_write_only() {
+				warn!("Error::UnexpectedWriteOnlyDescriptor");
+                return Err(Error::UnexpectedWriteOnlyDescriptor(0));
+            }
+
+            if desc_request.len() as usize != size_of::<VirtioCanCtrlRequest>() {
+				println!("UnexpectedDescriptorSize, len = {:?}", desc_request.len());
+                return Err(Error::UnexpectedDescriptorSize(
+                    size_of::<VirtioCanCtrlRequest>(),
+                    desc_request.len(),
+                ));
+            }
+
+            let request = desc_chain
+                .memory()
+                .read_obj::<VirtioCanCtrlRequest>(desc_request.addr())
+                .map_err(|_| Error::DescriptorReadFailed)?;
+
+
+           match request.msg_type.into() {
+				VIRTIO_CAN_SET_CTRL_MODE_START => {
+					println!("VIRTIO_CAN_SET_CTRL_MODE_START");
+					//vcan->busoff = false;
+					Ok(())
+				}
+				VIRTIO_CAN_SET_CTRL_MODE_STOP => {
+					println!("VIRTIO_CAN_SET_CTRL_MODE_STOP");
+	            	//vcan->busoff = false;
+					Ok(())
+				}
+				_ => {
+					println!("Ctrl queue: msg type 0x{:?} unknown", request.msg_type);
+					return Err(Error::HandleEventUnknown.into())
+				},
+			}?;
+
+            let desc_response = descriptors[1];
+            if !desc_response.is_write_only() {
+				println!("This is not wirtable");
+                return Err(Error::UnexpectedReadableDescriptor(1));
+            }
+
+			let response = VIRTIO_CAN_STATUS_OK;
+
+            desc_chain
+                .memory()
+                .write_slice(response.as_slice(), desc_response.addr())
+                .map_err(|_| Error::DescriptorWriteFailed)?;
+
+            if vring.add_used(desc_chain.head_index(), desc_response.len()).is_err() {
+                println!("Couldn't return used descriptors to the ring");
+                warn!("Couldn't return used descriptors to the ring");
+            }
+        }
+
+        Ok(true)
+    }
+
+    fn process_tx_requests(
+		&self,
+		requests: Vec<CanDescriptorChain>,
+		vring: &VringRwLock
+	) -> Result<bool> {
+		dbg!("process_tx_requests");
+
+        if requests.is_empty() {
+            return Ok(true);
+        }
+
+		println!("requests.len: {:?}", requests.len());
+        for desc_chain in requests {
+            let descriptors: Vec<_> = desc_chain.clone().collect();
+
+            if descriptors.len() != 2 {
+				println!("Error::UnexpectedDescriptorCount");
+                return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+            }
+
+            let desc_request = descriptors[0];
+            if desc_request.is_write_only() {
+				println!("Error::UnexpectedReadOnlyDescriptor");
+                return Err(Error::UnexpectedWriteOnlyDescriptor(0));
+			}
+
+            if desc_request.len() as usize != size_of::<VirtioCanFrame>() {
+			    println!("Tx UnexpectedDescriptorSize, len = {:?}", desc_request.len());
+                //return Err(Error::UnexpectedDescriptorSize(
+                //    size_of::<VirtioCanFrame>(),
+                //    desc_request.len(),
+                //));
+            }
+
+            let request = desc_chain
+                .memory()
+                .read_obj::<VirtioCanFrame>(desc_request.addr())
+                .map_err(|_| Error::DescriptorReadFailed)?;
+
+			CanController::print_can_frame(request);
+
+			let msg_type = request.msg_type.to_native();
+			let mut can_id = request.can_id.to_native();
+			let mut flags = request.flags.to_native();
+			let mut length = request.length.to_native();
+
+	        if msg_type != VIRTIO_CAN_TX {
+	            warn!("TX: Message type 0x{:x} unknown\n", msg_type);
+                return Err(Error::UnexpectedCanMsgType(msg_type));
+	        }
+
+	        if (flags & VIRTIO_CAN_FLAGS_FD) != 0 {
+	            if length > 64 {
+	                println!("Cut sdu_len from {:?} to 64\n", request.length);
+	                length = 64;
+	            }
+	        } else {
+	            if length > 8 {
+	                println!("Cut sdu_len from {:?} to 8\n", request.length);
+	                length = 8;
+	            }
+	        }
+
+	        /*
+	         * Copy Virtio frame structure to qemu frame structure and
+	         * check while doing this whether the frame type was negotiated
+	         */
+	        if (flags & VIRTIO_CAN_FLAGS_EXTENDED) != 0 {
+	            flags &= CAN_EFF_MASK;
+	            flags |= CAN_EFF_FLAG;
+	        } else {
+	            flags &= CAN_SFF_MASK;
+	        }
+
+	        if (flags & VIRTIO_CAN_FLAGS_RTR) != 0 {
+	            if !self.check_features(VIRTIO_CAN_F_CAN_CLASSIC) ||
+	                !self.check_features(VIRTIO_CAN_F_RTR_FRAMES) {
+	                warn!("TX: RTR frames not negotiated");
+					return Err(Error::UnexpectedRtrFlag);
+	            }
+	            can_id |= flags | CAN_RTR_FLAG;
+	        }
+
+	        if (flags & VIRTIO_CAN_FLAGS_FD) != 0 {
+	            if !self.check_features(VIRTIO_CAN_F_CAN_FD) {
+	                warn!("TX: FD frames not negotiated\n");
+					return Err(Error::UnexpectedFdFlag);
+	            }
+	            flags |= CAN_FRMF_TYPE_FD;
+	        } else {
+	            if !self.check_features(VIRTIO_CAN_F_CAN_CLASSIC) {
+	                warn!("TX: Classic frames not negotiated\n");
+					return Err(Error::UnexpectedClassicFlag);
+	            }
+	            flags = 0;
+	        }
+
+	        let mut corrected_request = VirtioCanFrame::default();
+			corrected_request.msg_type = msg_type.into();
+			corrected_request.can_id = can_id.into();
+			corrected_request.flags = flags.into();
+			corrected_request.length = length.into();
+			corrected_request.sdu.copy_from_slice(&request.sdu[0..64]);
+
+            let desc_response = descriptors[1];
+            if !desc_response.is_write_only() {
+				println!("Error::UnexpectedWriteOnlyDescriptor");
+                return Err(Error::UnexpectedReadableDescriptor(1));
+            }
+
+			let response = match self.controller.write().unwrap().operation(corrected_request) {
+				Ok(result) => {
+					result
+    			}
+    			Err(_) => {
+    			    warn!("We got an error from controller send func");
+					VIRTIO_CAN_STATUS_ERR
+    			}
+			};
+
+            desc_chain
+                .memory()
+                .write_slice(response.as_slice(), desc_response.addr())
+                .map_err(|_| Error::DescriptorWriteFailed)?;
+
+            if vring.add_used(desc_chain.head_index(), desc_response.len()).is_err() {
+                println!("Couldn't return used descriptors to the ring");
+                warn!("Couldn't return used descriptors to the ring");
+            }
+        }
+
+        Ok(true)
+    }
+
+    fn process_rx_requests(
+		&mut self,
+		requests: Vec<CanDescriptorChain>,
+		vring: &VringRwLock
+	) -> Result<bool> {
+		dbg!("process_rx_requests");
+
+        if requests.is_empty() {
+            return Ok(true);
+        }
+
+        let desc_chain = &requests[0];
+        let descriptors: Vec<_> = desc_chain.clone().collect();
+
+        if descriptors.len() != 1 {
+			println!("Error::UnexpectedDescriptorCount");
+            return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+        }
+
+        let desc_response = descriptors[0];
+        if !desc_response.is_write_only() {
+            return Err(Error::UnexpectedReadableDescriptor(1));
+        }
+
+		let mut response = match self.controller.write().unwrap().pop() {
+		    Ok(item) => item,
+		    Err(_) => return Err(Error::HandleEventUnknown),
+		};
+
+		CanController::print_can_frame(response);
+
+        if (response.can_id.to_native() & CAN_ERR_FLAG) != 0 {
+            if (response.can_id.to_native() & CAN_ERR_BUSOFF) != 0 {
+                warn!("Got BusOff error frame, device does a local bus off\n");
+                //vcan->busoff = true;
+            } else {
+                println!("Dropping error frame 0x{:x}\n", response.can_id.to_native());
+            }
+            return Ok(true);
+        }
+
+		let mut can_rx = VirtioCanFrame::default();
+		can_rx.msg_type = VIRTIO_CAN_RX.into();
+		can_rx.can_id = response.can_id;
+		can_rx.length = response.length;
+		can_rx.flags = (can_rx.flags.to_native() | VIRTIO_CAN_FLAGS_FD).into();
+
+        if (response.flags.to_native() & CAN_FRMF_TYPE_FD) != 0 {
+            if !self.check_features(VIRTIO_CAN_F_CAN_FD) {
+				warn!("Drop non-supported CAN FD frame");
+				return Err(Error::UnexpectedFdFlag);
+            }
+        } else {
+            if !self.check_features(VIRTIO_CAN_F_CAN_CLASSIC) {
+				warn!("Drop non-supported CAN classic frame");
+				return Err(Error::UnexpectedClassicFlag);
+            }
+        }
+        if (response.can_id.to_native() & CAN_RTR_FLAG) != 0 &&
+			!self.check_features(VIRTIO_CAN_F_RTR_FRAMES) {
+				warn!("Drop non-supported RTR frame");
+				return Err(Error::UnexpectedRtrFlag);
+        }
+
+		if (response.can_id.to_native() & CAN_EFF_FLAG) != 0 {
+		    can_rx.flags = VIRTIO_CAN_FLAGS_EXTENDED.into();
+		    can_rx.can_id = (response.can_id.to_native() & CAN_EFF_MASK).into();
+		} else {
+		    can_rx.can_id = (response.can_id.to_native() & CAN_SFF_MASK).into();
+		}
+		if (response.can_id.to_native() & CAN_RTR_FLAG) != 0 {
+		    can_rx.flags = (can_rx.flags.to_native() & VIRTIO_CAN_FLAGS_RTR).into();
+		}
+
+		// HACK AHEAD: Vcan can not be comfigured as CANFD interface, but possible
+		// to configure its MTU to 64 bytes. So if a messages bigger than 8 bytes
+		// is being received we consider it as CANFD message.
+		let can_in_name = self.controller.read().unwrap().can_in_name.clone();
+	    if self.check_features(VIRTIO_CAN_F_CAN_FD) &&
+		   response.length.to_native() > 8 && can_in_name == "vcan0" {
+			response.flags = (response.flags.to_native() | CAN_FRMF_TYPE_FD).into();
+			warn!("\n\n\nCANFD VCAN0\n\n");
+		}
+
+		if (response.flags.to_native() & CAN_FRMF_TYPE_FD) != 0 {
+		    can_rx.flags = (can_rx.flags.to_native() | VIRTIO_CAN_FLAGS_FD).into();
+		    if response.length.to_native() > 64 {
+		        warn!("%s(): Cut length from {} to 64\n", response.length.to_native());
+		        can_rx.length = 64.into();
+		    }
+		} else {
+		    if response.length.to_native() > 8 {
+		        warn!("%s(): Cut length from {} to 8\n", response.length.to_native());
+		        can_rx.length = 8.into();
+		    }
+		}
+
+		can_rx.sdu.copy_from_slice(&response.sdu[0..64]);
+		CanController::print_can_frame(can_rx);
+
+        desc_chain
+            .memory()
+            .write_slice(can_rx.as_slice(), desc_response.addr())
+            .map_err(|_| Error::DescriptorWriteFailed)?;
+
+        if vring.add_used(desc_chain.head_index(), desc_response.len()).is_err() {
+            warn!("Couldn't return used descriptors to the ring");
+        }
+
+        Ok(true)
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_ctrl_queue(&mut self, vring: &VringRwLock) -> Result<()> {
+		dbg!("process_ctrl_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_ctrl_requests(requests, vring)? {
+            // Send notification once all the requests are processed
+            vring
+                .signal_used_queue()
+                .map_err(|_| Error::NotificationFailed)?;
+        }
+		Ok(())
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_tx_queue(&self, vring: &VringRwLock) -> Result<()> {
+		dbg!("process_tx_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_tx_requests(requests, vring)? {
+            // Send notification once all the requests are processed
+            vring
+                .signal_used_queue()
+                .map_err(|_| {
+					println!("signal_used_queue error");
+					Error::NotificationFailed
+				})?;
+        }
+
+        Ok(())
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_rx_queue(&mut self, vring: &VringRwLock) -> Result<()> {
+		dbg!("process_rx_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_rx_requests(requests, vring)? {
+            // Send notification once all the requests are processed
+            vring
+                .signal_used_queue()
+                .map_err(|_| {
+					println!("NotificationFailed");
+					Error::NotificationFailed
+				})?;
+        }
+		Ok(())
+    }
+
+    fn process_rx_queue_dump(&mut self, _vring: &VringRwLock) -> Result<()> {
+		dbg!("Do nothing, if you reach that point!");
+		Ok(())
+    }
+
+    /// Set self's VringWorker.
+    pub(crate) fn set_vring_worker(
+		&self,
+        vring_worker: &Arc<VringEpollHandler<Arc<RwLock<VhostUserCanBackend>>, VringRwLock, ()>>,
+    ) {
+		let rx_event_fd = self.controller.read().unwrap().rx_event_fd.as_raw_fd();
+		vring_worker
+            .register_listener(
+				rx_event_fd,
+				EventSet::IN,
+				//u64::from(BACKEND_EFD))
+				4u64  as u64)
+            .unwrap();
+    }
+}
+
+/// VhostUserBackendMut trait methods
+impl VhostUserBackendMut<VringRwLock, ()>
+    for VhostUserCanBackend
+{
+    fn num_queues(&self) -> usize {
+		println!("num_queues: {:?}", NUM_QUEUES);
+        NUM_QUEUES
+    }
+
+    fn max_queue_size(&self) -> usize {
+		println!("max_queue_size: {:?}", QUEUE_SIZE);
+        QUEUE_SIZE
+    }
+
+    fn features(&self) -> u64 {
+        // this matches the current libvhost defaults except VHOST_F_LOG_ALL
+        let features = 1 << VIRTIO_F_VERSION_1
+            | 1 << VIRTIO_F_NOTIFY_ON_EMPTY
+            | 1 << VIRTIO_RING_F_EVENT_IDX
+			| 1 << VIRTIO_CAN_F_CAN_CLASSIC
+			| 1 << VIRTIO_CAN_F_CAN_FD
+            | 1 << VIRTIO_RING_F_INDIRECT_DESC
+            | VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits();
+
+		println!("vhu_can->features: {:x}", features);
+		features
+    }
+
+	fn acked_features(&mut self, _features: u64) {
+		println!("\nacked_features: 0x{:x}\n", _features);
+		self.acked_features = _features;
+	}
+
+    fn protocol_features(&self) -> VhostUserProtocolFeatures {
+        let protocol_features = VhostUserProtocolFeatures::MQ
+            | VhostUserProtocolFeatures::CONFIG
+            | VhostUserProtocolFeatures::REPLY_ACK;
+            //| VhostUserProtocolFeatures::STATUS
+
+		println!("protocol_features: {:x}", protocol_features);
+		protocol_features
+    }
+
+    fn get_config(&self, offset: u32, size: u32) -> Vec<u8> {
+        // SAFETY: The layout of the structure is fixed and can be initialized by
+        // reading its content from byte array.
+		dbg!("vhu_can->get_config");
+        unsafe {
+            from_raw_parts(
+                self.controller.write().unwrap()
+                    .config()
+                    .as_slice()
+                    .as_ptr()
+                    .offset(offset as isize) as *const _ as *const _,
+                size as usize,
+            )
+            .to_vec()
+        }
+    }
+
+    fn set_event_idx(&mut self, enabled: bool) {
+        dbg!(self.event_idx = enabled);
+    }
+
+    fn update_memory(&mut self, mem: GuestMemoryAtomic<GuestMemoryMmap>) -> IoResult<()> {
+		dbg!("update_memory\n");
+        self.mem = Some(mem);
+        Ok(())
+    }
+
+    fn handle_event(
+        &mut self,
+        device_event: u16,
+        evset: EventSet,
+        vrings: &[VringRwLock],
+        _thread_id: usize,
+    ) -> IoResult<bool> {
+		dbg!("\nhandle_event:");
+
+        if evset != EventSet::IN {
+            return Err(Error::HandleEventNotEpollIn.into());
+        }
+		if device_event == RX_QUEUE {
+			println!("RX_QUEUE\n");
+			return Ok(false);
+		};
+		let vring = if device_event != BACKEND_EFD {
+			&vrings[device_event as usize]
+		} else {
+			println!("BACKEND_EFD\n");
+			let _ = self.controller.write().unwrap().rx_event_fd.read();
+			&vrings[RX_QUEUE as usize]
+		};
+        if self.event_idx {
+            // vm-virtio's Queue implementation only checks avail_index
+            // once, so to properly support EVENT_IDX we need to keep
+            // calling process_request_queue() until it stops finding
+            // new requests on the queue.
+            loop {
+                vring.disable_notification().unwrap();
+                //match queue_idx {
+                match device_event {
+                    CTRL_QUEUE => self.process_ctrl_queue(vring),
+                    TX_QUEUE => self.process_tx_queue(vring),
+                    RX_QUEUE => self.process_rx_queue_dump(vring),
+                    BACKEND_EFD => self.process_rx_queue(vring),
+                    _ => Err(Error::HandleEventUnknown.into()),
+                }?;
+                if !vring.enable_notification().unwrap() {
+                    break;
+                }
+            }
+        } else {
+            // Without EVENT_IDX, a single call is enough.
+            match device_event {
+                CTRL_QUEUE => self.process_ctrl_queue(vring),
+                TX_QUEUE => self.process_tx_queue(vring),
+                RX_QUEUE => self.process_rx_queue_dump(vring),
+                BACKEND_EFD => self.process_rx_queue(vring),
+                _ => Err(Error::HandleEventUnknown.into()),
+            }?;
+        }
+        Ok(false)
+    }
+
+    fn exit_event(&self, _thread_index: usize) -> Option<EventFd> {
+		dbg!("exit_event\n");
+        self.exit_event.try_clone().ok()
+    }
+}
+