devices/virtio/vhost_user_backend/
connection.rs

1// Copyright 2022 The ChromiumOS Authors
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5pub mod sys;
6use std::any::Any;
7use std::pin::Pin;
8
9use cros_async::Executor;
10use futures::Future;
11
12use crate::virtio::vhost_user_backend::handler::DeviceRequestHandler;
13use crate::virtio::vhost_user_backend::handler::VhostUserDevice;
14use crate::virtio::vhost_user_backend::VhostUserDeviceBuilder;
15use crate::virtio::vhost_user_backend::VhostUserListener;
16use crate::virtio::vhost_user_backend::VhostUserStream;
17
18pub enum BackendConnection {
19    Listener(VhostUserListener),
20    Stream(VhostUserStream),
21}
22
23/// Trait that the platform-specific type `VhostUserConnection` needs to implement. It contains all
24/// the methods that are ok to call from non-platform specific code.
25pub trait VhostUserConnectionTrait {
26    /// Take and return resources owned by the parent process in case of a incoming fork.
27    ///
28    /// This method needs to be called only if you are going to use the connection in a jailed child
29    /// process. In this case, the connection will belong to the child and the parent will drop it,
30    /// but the child may lack the rights to drop some resources created at construction time. One
31    /// such example is the socket file of a regular vhost-user device, that cannot be dropped by
32    /// the child unless it gets extra permissions.
33    ///
34    /// This method returns an opaque object that, upon being dropped, will free these resources.
35    /// That way, the child process does not need extra rights to clear them, and the parent can
36    /// drop the connection after forking and just need to keep that object alive until the child
37    /// exits to do housekeeping properly.
38    ///
39    /// The default implementation returns nothing as that's what most connection would need anyway.
40    fn take_parent_process_resources(&mut self) -> Option<Box<dyn Any>> {
41        None
42    }
43
44    /// Returns a `Future` that processes requests for `handler`. The future exits when the
45    /// front-end side disconnects or an error occurs.
46    fn run_req_handler<'e>(
47        self,
48        handler: Box<dyn vmm_vhost::Backend>,
49        ex: &'e Executor,
50    ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + 'e>>;
51
52    /// Returns a `Future` that will process requests from `backend` when polled. The future exits
53    /// when the front-end side disconnects or an error occurs.
54    ///
55    /// This is a legacy way to run devices - prefer `run_device`.
56    fn run_backend<'e>(
57        self,
58        backend: impl VhostUserDevice + 'static,
59        ex: &'e Executor,
60    ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + 'e>>
61    where
62        Self: Sized,
63    {
64        self.run_req_handler(Box::new(DeviceRequestHandler::new(backend)), ex)
65    }
66
67    /// Start processing requests for a `VhostUserDevice` on `connection`. Returns when the
68    /// front-end side disconnects or an error occurs.
69    fn run_device(self, ex: Executor, device: Box<dyn VhostUserDeviceBuilder>) -> anyhow::Result<()>
70    where
71        Self: Sized,
72    {
73        ex.run_until(self.run_req_handler(device.build(&ex).unwrap(), &ex))?
74    }
75}
devices/virtio/vhost_user_backend/connection.rs

devices/virtio/vhost_user_backend/
connection.rs
