vhost_user_net: Allow user to set MTU

Adding the support for the user to set the MTU for the vhost-user-net
backend, which allows the integration test to be extended with the test
of the MTU parameter.

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

tests/integration.rs

@@ -202,23 +202,25 @@ fn prepare_vhost_user_net_daemon(
     tmp_dir: &TempDir,
     ip: &str,
     tap: Option<&str>,
+    mtu: Option<u16>,
     num_queues: usize,
     client_mode: bool,
 ) -> (std::process::Command, String) {
     let vunet_socket_path = String::from(tmp_dir.as_path().join("vunet.sock").to_str().unwrap());
 
     // Start the daemon
-    let net_params = if let Some(tap_str) = tap {
-        format!(
-            "tap={},ip={},mask=255.255.255.0,socket={},num_queues={},queue_size=1024,client={}",
-            tap_str, ip, vunet_socket_path, num_queues, client_mode
-        )
-    } else {
-        format!(
-            "ip={},mask=255.255.255.0,socket={},num_queues={},queue_size=1024,client={}",
-            ip, vunet_socket_path, num_queues, client_mode
-        )
-    };
+    let mut net_params = format!(
+        "ip={},mask=255.255.255.0,socket={},num_queues={},queue_size=1024,client={}",
+        ip, vunet_socket_path, num_queues, client_mode
+    );
+
+    if let Some(tap) = tap {
+        net_params.push_str(format!(",tap={}", tap).as_str());
+    }
+
+    if let Some(mtu) = mtu {
+        net_params.push_str(format!(",mtu={}", mtu).as_str());
+    }
 
     let mut command = Command::new(clh_command("vhost_user_net"));
     command.args(["--net-backend", net_params.as_str()]);
@@ -757,8 +759,14 @@ fn _test_power_button(acpi: bool) {
     handle_child_output(r, &output);
 }
 
-type PrepareNetDaemon =
-    dyn Fn(&TempDir, &str, Option<&str>, usize, bool) -> (std::process::Command, String);
+type PrepareNetDaemon = dyn Fn(
+    &TempDir,
+    &str,
+    Option<&str>,
+    Option<u16>,
+    usize,
+    bool,
+) -> (std::process::Command, String);
 
 fn test_vhost_user_net(
     tap: Option<&str>,
@@ -779,16 +787,19 @@ fn test_vhost_user_net(
         None
     };
 
+    let mtu = Some(3000);
+
     let (mut daemon_command, vunet_socket_path) = prepare_daemon(
         &guest.tmp_dir,
         &guest.network.host_ip,
         tap,
+        mtu,
         num_queues,
         client_mode_daemon,
     );
 
     let net_params = format!(
-        "vhost_user=true,mac={},socket={},num_queues={},queue_size=1024{},vhost_mode={}",
+        "vhost_user=true,mac={},socket={},num_queues={},queue_size=1024{},vhost_mode={},mtu=3000",
         guest.network.guest_mac,
         vunet_socket_path,
         num_queues,
@@ -843,6 +854,19 @@ fn test_vhost_user_net(
             assert_eq!(String::from_utf8_lossy(&mac_count.stdout).trim(), "1");
         }
 
+        #[cfg(target_arch = "aarch64")]
+        let iface = "enp0s4";
+        #[cfg(target_arch = "x86_64")]
+        let iface = "ens4";
+
+        assert_eq!(
+            guest
+                .ssh_command(format!("cat /sys/class/net/{}/mtu", iface).as_str())
+                .unwrap()
+                .trim(),
+            "3000"
+        );
+
         // 1 network interface + default localhost ==> 2 interfaces
         // It's important to note that this test is fully exercising the
         // vhost-user-net implementation and the associated backend since

vhost_user_net/src/lib.rs

@@ -119,10 +119,12 @@ pub struct VhostUserNetBackend {
 }
 
 impl VhostUserNetBackend {
+    #[allow(clippy::too_many_arguments)]
     fn new(
         ip_addr: Ipv4Addr,
         host_mac: MacAddr,
         netmask: Ipv4Addr,
+        mtu: Option<u16>,
         num_queues: usize,
         queue_size: u16,
         ifname: Option<&str>,
@@ -133,7 +135,7 @@ impl VhostUserNetBackend {
             Some(ip_addr),
             Some(netmask),
             &mut Some(host_mac),
-            None,
+            mtu,
             num_queues / 2,
             None,
         )
@@ -182,6 +184,7 @@ impl VhostUserBackendMut<VringRwLock<GuestMemoryAtomic<GuestMemoryMmap>>, Atomic
             | 1 << VIRTIO_NET_F_CTRL_VQ
             | 1 << VIRTIO_NET_F_MQ
             | 1 << VIRTIO_NET_F_MAC
+            | 1 << VIRTIO_NET_F_MTU
             | 1 << VIRTIO_F_NOTIFY_ON_EMPTY
             | 1 << VIRTIO_F_VERSION_1
             | VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits()
@@ -273,6 +276,7 @@ pub struct VhostUserNetBackendConfig {
     pub ip: Ipv4Addr,
     pub host_mac: MacAddr,
     pub mask: Ipv4Addr,
+    pub mtu: Option<u16>,
     pub socket: String,
     pub num_queues: usize,
     pub queue_size: u16,
@@ -289,6 +293,7 @@ impl VhostUserNetBackendConfig {
             .add("ip")
             .add("host_mac")
             .add("mask")
+            .add("mtu")
             .add("queue_size")
             .add("num_queues")
             .add("socket")
@@ -309,6 +314,7 @@ impl VhostUserNetBackendConfig {
             .convert("mask")
             .map_err(Error::FailedConfigParse)?
             .unwrap_or_else(|| Ipv4Addr::new(255, 255, 255, 0));
+        let mtu = parser.convert("mtu").map_err(Error::FailedConfigParse)?;
         let queue_size = parser
             .convert("queue_size")
             .map_err(Error::FailedConfigParse)?
@@ -328,6 +334,7 @@ impl VhostUserNetBackendConfig {
             ip,
             host_mac,
             mask,
+            mtu,
             socket,
             num_queues,
             queue_size,
@@ -355,6 +362,7 @@ pub fn start_net_backend(backend_command: &str) {
             backend_config.ip,
             backend_config.host_mac,
             backend_config.mask,
+            backend_config.mtu,
             backend_config.num_queues,
             backend_config.queue_size,
             tap,

vmm/src/config.rs

@@ -1366,9 +1366,7 @@ impl NetConfig {
             .map_err(Error::ParseNetwork)?
             .unwrap_or_else(default_netconfig_mac);
         let host_mac = parser.convert("host_mac").map_err(Error::ParseNetwork)?;
-        let mtu = parser
-            .convert("mtu")
-            .map_err(Error::ParseNetwork)?;
+        let mtu = parser.convert("mtu").map_err(Error::ParseNetwork)?;
         let iommu = parser
             .convert::<Toggle>("iommu")
             .map_err(Error::ParseNetwork)?