virtio-devices, vmm: vhost: net: Add client mode support

Adding the support for an OVS vhost-user backend to connect as the
vhost-user client. This means we introduce with this patch a new
option to our `--net` parameter. This option is called 'server' in order
to ask the VMM to run as the server for the vhost-user socket.

Fixes #1745

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtio-devices/src/vhost_user/mod.rs

@@ -24,10 +24,14 @@ pub use self::vu_common_ctrl::VhostUserConfig;
 
 #[derive(Debug)]
 pub enum Error {
+    /// Failed accepting connection.
+    AcceptConnection(io::Error),
     /// Invalid available address.
     AvailAddress,
     /// Queue number  is not correct
     BadQueueNum,
+    /// Failed binding vhost-user socket.
+    BindSocket(io::Error),
     /// Creating kill eventfd failed.
     CreateKillEventFd(io::Error),
     /// Cloning kill eventfd failed.

virtio-devices/src/vhost_user/net.rs

@@ -16,6 +16,7 @@ use net_util::MacAddr;
 use seccomp::{SeccompAction, SeccompFilter};
 use std::ops::Deref;
 use std::os::unix::io::AsRawFd;
+use std::os::unix::net::UnixListener;
 use std::result;
 use std::sync::{Arc, Barrier};
 use std::thread;
@@ -46,6 +47,7 @@ pub struct Net {
     seccomp_action: SeccompAction,
     guest_memory: Option<GuestMemoryAtomic<GuestMemoryMmap>>,
     acked_protocol_features: u64,
+    socket_path: Option<String>,
 }
 
 impl Net {
@@ -56,9 +58,23 @@ impl Net {
         mac_addr: MacAddr,
         vu_cfg: VhostUserConfig,
         seccomp_action: SeccompAction,
+        server: bool,
     ) -> Result<Net> {
-        let mut vhost_user_net = Master::connect(&vu_cfg.socket, vu_cfg.num_queues as u64)
-            .map_err(Error::VhostUserCreateMaster)?;
+        let mut socket_path: Option<String> = None;
+
+        let mut vhost_user_net = if server {
+            info!("Binding vhost-user-net listener...");
+            let listener = UnixListener::bind(&vu_cfg.socket).map_err(Error::BindSocket)?;
+            info!("Waiting for incoming vhost-user-net connection...");
+            let (stream, _) = listener.accept().map_err(Error::AcceptConnection)?;
+
+            socket_path = Some(vu_cfg.socket.clone());
+
+            Master::from_stream(stream, vu_cfg.num_queues as u64)
+        } else {
+            Master::connect(&vu_cfg.socket, vu_cfg.num_queues as u64)
+                .map_err(Error::VhostUserCreateMaster)?
+        };
 
         // Filling device and vring features VMM supports.
         let mut avail_features = 1 << virtio_net::VIRTIO_NET_F_GUEST_CSUM
@@ -166,6 +182,7 @@ impl Net {
             seccomp_action,
             guest_memory: None,
             acked_protocol_features,
+            socket_path,
         })
     }
 }
@@ -368,6 +385,11 @@ impl VirtioDevice for Net {
 
     fn shutdown(&mut self) {
         let _ = unsafe { libc::close(self.vhost_user_net.as_raw_fd()) };
+
+        // Remove socket path if needed
+        if let Some(socket_path) = &self.socket_path {
+            let _ = std::fs::remove_file(socket_path);
+        }
     }
 
     fn add_memory_region(

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -712,6 +712,9 @@ components:
           default: false
         vhost_socket:
           type: string
+        vhost_mode:
+          type: string
+          default: "client"
         id:
           type: string
         fd:

vmm/src/config.rs

@@ -878,6 +878,35 @@ impl DiskConfig {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
+pub enum VhostMode {
+    Client,
+    Server,
+}
+
+impl Default for VhostMode {
+    fn default() -> Self {
+        VhostMode::Client
+    }
+}
+
+#[derive(Debug)]
+pub enum ParseVhostModeError {
+    InvalidValue(String),
+}
+
+impl FromStr for VhostMode {
+    type Err = ParseVhostModeError;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "client" => Ok(VhostMode::Client),
+            "server" => Ok(VhostMode::Server),
+            _ => Err(ParseVhostModeError::InvalidValue(s.to_owned())),
+        }
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
 pub struct NetConfig {
     #[serde(default = "default_netconfig_tap")]
@@ -900,6 +929,8 @@ pub struct NetConfig {
     pub vhost_user: bool,
     pub vhost_socket: Option<String>,
     #[serde(default)]
+    pub vhost_mode: VhostMode,
+    #[serde(default)]
     pub id: Option<String>,
     #[serde(default)]
     pub fds: Option<Vec<i32>>,
@@ -944,6 +975,7 @@ impl Default for NetConfig {
             queue_size: default_netconfig_queue_size(),
             vhost_user: false,
             vhost_socket: None,
+            vhost_mode: VhostMode::Client,
             id: None,
             fds: None,
             rate_limiter_config: None,
@@ -954,8 +986,8 @@ impl Default for NetConfig {
 impl NetConfig {
     pub const SYNTAX: &'static str = "Network parameters \
     \"tap=<if_name>,ip=<ip_addr>,mask=<net_mask>,mac=<mac_addr>,fd=<fd1:fd2...>,iommu=on|off,\
-    num_queues=<number_of_queues>,queue_size=<size_of_each_queue>,\
-    vhost_user=<vhost_user_enable>,socket=<vhost_user_socket_path>,id=<device_id>,\
+    num_queues=<number_of_queues>,queue_size=<size_of_each_queue>,id=<device_id>,\
+    vhost_user=<vhost_user_enable>,socket=<vhost_user_socket_path>,vhost_mode=client|server,\
     bw_size=<bytes>,bw_one_time_burst=<bytes>,bw_refill_time=<ms>,\
     ops_size=<io_ops>,ops_one_time_burst=<io_ops>,ops_refill_time=<ms>\"";
 
@@ -973,6 +1005,7 @@ impl NetConfig {
             .add("num_queues")
             .add("vhost_user")
             .add("socket")
+            .add("vhost_mode")
             .add("id")
             .add("fd")
             .add("bw_size")
@@ -1016,6 +1049,10 @@ impl NetConfig {
             .unwrap_or(Toggle(false))
             .0;
         let vhost_socket = parser.get("socket");
+        let vhost_mode = parser
+            .convert("vhost_mode")
+            .map_err(Error::ParseNetwork)?
+            .unwrap_or_default();
         let id = parser.get("id");
         let fds = parser
             .convert::<IntegerList>("fd")
@@ -1084,6 +1121,7 @@ impl NetConfig {
             queue_size,
             vhost_user,
             vhost_socket,
+            vhost_mode,
             id,
             fds,
             rate_limiter_config,

vmm/src/device_manager.rs

@@ -9,9 +9,10 @@
 // SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
 //
 
-use crate::config::ConsoleOutputMode;
-use crate::config::DeviceConfig;
-use crate::config::{DiskConfig, FsConfig, NetConfig, PmemConfig, VmConfig, VsockConfig};
+use crate::config::{
+    ConsoleOutputMode, DeviceConfig, DiskConfig, FsConfig, NetConfig, PmemConfig, VhostMode,
+    VmConfig, VsockConfig,
+};
 use crate::device_tree::{DeviceNode, DeviceTree};
 #[cfg(feature = "kvm")]
 use crate::interrupt::kvm::KvmMsiInterruptManager as MsiInterruptManager;
@@ -2035,12 +2036,17 @@ impl DeviceManager {
                 num_queues: net_cfg.num_queues,
                 queue_size: net_cfg.queue_size,
             };
+            let server = match net_cfg.vhost_mode {
+                VhostMode::Client => false,
+                VhostMode::Server => true,
+            };
             let vhost_user_net_device = Arc::new(Mutex::new(
                 match virtio_devices::vhost_user::Net::new(
                     id.clone(),
                     net_cfg.mac,
                     vu_cfg,
                     self.seccomp_action.clone(),
+                    server,
                 ) {
                     Ok(vun_device) => vun_device,
                     Err(e) => {