vhost-net: add control socket basic support

Add a pair of control socket for vhost net. This pair can be
used for the vhost-net device model to control and
communicate with its activate thread.

BUG=None
TEST=cargo test -p devices

Change-Id: I8bacdb9132787dc499ef00eea1df26ff3b35028d
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2046450
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>

3 files changed, 53 insertions, 0 deletions

diff --git a/devices/src/virtio/vhost/control_socket.rs b/devices/src/virtio/vhost/control_socket.rs
new file mode 100644
index 0000000..a1ccfaf
--- /dev/null
+++ b/devices/src/virtio/vhost/control_socket.rs
@@ -0,0 +1,36 @@
+// Copyright 2020 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 LICENSE file.
+
+use msg_socket::{MsgOnSocket, MsgSocket};
+use sys_util::Error as SysError;
+
+#[derive(MsgOnSocket, Debug)]
+pub enum VhostDevRequest {
+    /// Mask or unmask all the MSI entries for a Virtio Vhost device.
+    MsixChanged,
+    /// Mask or unmask a MSI entry for a Virtio Vhost device.
+    MsixEntryChanged(usize),
+}
+
+#[derive(MsgOnSocket, Debug)]
+pub enum VhostDevResponse {
+    Ok,
+    Err(SysError),
+}
+
+pub type VhostDevRequestSocket = MsgSocket<VhostDevRequest, VhostDevResponse>;
+pub type VhostDevResponseSocket = MsgSocket<VhostDevResponse, VhostDevRequest>;
+
+/// Create control socket pair. This pair is used to communicate with the
+/// virtio device process.
+/// Mainly between the virtio and activate thread.
+pub fn create_control_sockets() -> (
+    Option<VhostDevRequestSocket>,
+    Option<VhostDevResponseSocket>,
+) {
+    match msg_socket::pair::<VhostDevRequest, VhostDevResponse>() {
+        Ok((request, response)) => (Some(request), Some(response)),
+        _ => (None, None),
+    }
+}
diff --git a/devices/src/virtio/vhost/mod.rs b/devices/src/virtio/vhost/mod.rs
index 66c62d0..86ed81e 100644
--- a/devices/src/virtio/vhost/mod.rs
+++ b/devices/src/virtio/vhost/mod.rs
@@ -12,10 +12,12 @@ use remain::sorted;
 use sys_util::Error as SysError;
 use vhost::Error as VhostError;
 
+mod control_socket;
 mod net;
 mod vsock;
 mod worker;
 
+pub use self::control_socket::*;
 pub use self::net::Net;
 pub use self::vsock::Vsock;
 
diff --git a/devices/src/virtio/vhost/net.rs b/devices/src/virtio/vhost/net.rs
index ff72970..21f1587 100644
--- a/devices/src/virtio/vhost/net.rs
+++ b/devices/src/virtio/vhost/net.rs
@@ -14,6 +14,7 @@ use sys_util::{error, warn, EventFd, GuestMemory};
 use vhost::NetT as VhostNetT;
 use virtio_sys::virtio_net;
 
+use super::control_socket::*;
 use super::worker::Worker;
 use super::{Error, Result};
 use crate::virtio::{Interrupt, Queue, VirtioDevice, TYPE_NET};
@@ -31,6 +32,8 @@ pub struct Net<T: TapT, U: VhostNetT<T>> {
     vhost_interrupt: Option<Vec<EventFd>>,
     avail_features: u64,
     acked_features: u64,
+    request_socket: Option<VhostDevRequestSocket>,
+    response_socket: Option<VhostDevResponseSocket>,
 }
 
 impl<T, U> Net<T, U>
@@ -85,6 +88,8 @@ where
             vhost_interrupt.push(EventFd::new().map_err(Error::VhostIrqCreate)?);
         }
 
+        let (request_socket, response_socket) = create_control_sockets();
+
         Ok(Net {
             workers_kill_evt: Some(kill_evt.try_clone().map_err(Error::CloneKillEventFd)?),
             kill_evt,
@@ -94,6 +99,8 @@ where
             vhost_interrupt: Some(vhost_interrupt),
             avail_features,
             acked_features: 0u64,
+            request_socket,
+            response_socket,
         })
     }
 }
@@ -143,6 +150,14 @@ where
         }
         keep_fds.push(self.kill_evt.as_raw_fd());
 
+        if let Some(request_socket) = &self.request_socket {
+            keep_fds.push(request_socket.as_raw_fd());
+        }
+
+        if let Some(response_socket) = &self.response_socket {
+            keep_fds.push(response_socket.as_raw_fd());
+        }
+
         keep_fds
     }