devices/virtio/vhost_user_backend/connection/sys/linux/
listener.rs

1// Copyright 2024 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
5use std::pin::Pin;
6
7use anyhow::Context;
8use base::AsRawDescriptor;
9use base::RawDescriptor;
10use cros_async::AsyncWrapper;
11use cros_async::Executor;
12use futures::Future;
13use futures::FutureExt;
14use vmm_vhost::connection::Listener;
15use vmm_vhost::unix::SocketListener;
16use vmm_vhost::BackendServer;
17
18use crate::virtio::vhost_user_backend::connection::VhostUserConnectionTrait;
19use crate::virtio::vhost_user_backend::handler::sys::linux::run_handler;
20
21/// On Unix we can listen to a socket.
22pub struct VhostUserListener(SocketListener);
23
24impl VhostUserListener {
25    /// Create a vhost-user listener from a UNIX domain socket path.
26    pub fn new(path: &str) -> anyhow::Result<Self> {
27        let listener = SocketListener::new(path, true)?;
28
29        Ok(VhostUserListener(listener))
30    }
31}
32
33impl AsRawDescriptor for VhostUserListener {
34    fn as_raw_descriptor(&self) -> RawDescriptor {
35        self.0.as_raw_descriptor()
36    }
37}
38
39/// Attaches to an already bound socket via `listener` and handles incoming messages from the
40/// VMM, which are dispatched to the device backend via the `VhostUserDevice` trait methods.
41async fn run_with_handler(
42    mut listener: SocketListener,
43    handler: Box<dyn vmm_vhost::Backend>,
44    ex: &Executor,
45) -> anyhow::Result<()> {
46    listener.set_nonblocking(true)?;
47
48    loop {
49        // If the listener is not ready on the first call to `accept` and returns `None`, we
50        // temporarily convert it into an async I/O source and yield until it signals there is
51        // input data awaiting, before trying again.
52        match listener
53            .accept()
54            .context("failed to accept an incoming connection")?
55        {
56            Some(connection) => {
57                let req_handler = BackendServer::new(connection, handler);
58                return run_handler(req_handler, ex).await;
59            }
60            None => {
61                // Nobody is on the other end yet, wait until we get a connection.
62                let async_waiter = ex
63                    .async_from(AsyncWrapper::new(listener))
64                    .context("failed to create async waiter")?;
65                async_waiter.wait_readable().await?;
66
67                // Retrieve the listener back so we can use it again.
68                listener = async_waiter.into_source().into_inner();
69            }
70        }
71    }
72}
73
74impl VhostUserConnectionTrait for VhostUserListener {
75    fn run_req_handler<'e>(
76        self,
77        handler: Box<dyn vmm_vhost::Backend>,
78        ex: &'e Executor,
79    ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + 'e>> {
80        async { run_with_handler(self.0, handler, ex).await }.boxed_local()
81    }
82
83    fn take_parent_process_resources(&mut self) -> Option<Box<dyn std::any::Any>> {
84        self.0.take_resources_for_parent()
85    }
86}
devices/virtio/vhost_user_backend/connection/sys/linux/listener.rs

devices/virtio/vhost_user_backend/connection/sys/linux/
listener.rs
