ovs: set the MTU in ovsdb when changing platform MTU of ovs-interfacebg/ovs-interface-mtu-rh1808124

If we change the the MTU of an ovs interface only through netlink, the
change could be overridden by ovs-vswitchd at any time when other
interfaces change. Set the MTU also in the ovsdb to prevent such
changes.

Note that if the MTU comes from the connection, we already set the
ovsdb MTU at creation time and so this other update becomes
useless. But it is needed when changing the MTU at runtime (reapply)
or when the MTU comes from a different source (e.g. DHCP).

3 files changed, 54 insertions, 4 deletions

diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c
index 3a63af5847..c3483e4db7 100644
--- a/src/devices/nm-device.c
+++ b/src/devices/nm-device.c
@@ -9739,6 +9739,17 @@ _set_mtu (NMDevice *self, guint32 mtu)
 	}
 }
 
+static gboolean
+set_platform_mtu (NMDevice *self, guint32 mtu)
+{
+	int r;
+
+	r = nm_platform_link_set_mtu (nm_device_get_platform (self),
+	                              nm_device_get_ip_ifindex (self),
+	                              mtu);
+	return (r != -NME_PL_CANT_SET_MTU);
+}
+
 static void
 _commit_mtu (NMDevice *self, const NMIP4Config *config)
 {
@@ -9898,10 +9909,7 @@ _commit_mtu (NMDevice *self, const NMIP4Config *config)
 		}
 
 		if (mtu_desired && mtu_desired != mtu_plat) {
-			int r;
-
-			r = nm_platform_link_set_mtu (nm_device_get_platform (self), ifindex, mtu_desired);
-			if (r == -NME_PL_CANT_SET_MTU) {
+			if (!NM_DEVICE_GET_CLASS (self)->set_platform_mtu (self, mtu_desired)) {
 				anticipated_failure = TRUE;
 				success = FALSE;
 				_LOGW (LOGD_DEVICE, "mtu: failure to set MTU. %s",
@@ -17691,6 +17699,7 @@ nm_device_class_init (NMDeviceClass *klass)
 	klass->parent_changed_notify = parent_changed_notify;
 	klass->can_reapply_change = can_reapply_change;
 	klass->reapply_connection = reapply_connection;
+	klass->set_platform_mtu = set_platform_mtu;
 
 	obj_properties[PROP_UDI] =
 	    g_param_spec_string (NM_DEVICE_UDI, "", "",
diff --git a/src/devices/nm-device.h b/src/devices/nm-device.h
index 28f86e825e..c18301b275 100644
--- a/src/devices/nm-device.h
+++ b/src/devices/nm-device.h
@@ -444,6 +444,8 @@ typedef struct _NMDeviceClass {
 
 	gboolean        (* can_update_from_platform_link) (NMDevice *self, const NMPlatformLink *plink);
 
+	gboolean        (* set_platform_mtu) (NMDevice *self, guint32 mtu);
+
 	/* Controls, whether to call act_stage2_config() callback also for assuming
 	 * a device or for external activations. In this case, act_stage2_config() must
 	 * take care not to touch the device's configuration. */
diff --git a/src/devices/ovs/nm-device-ovs-interface.c b/src/devices/ovs/nm-device-ovs-interface.c
index 2868dee093..951b578892 100644
--- a/src/devices/ovs/nm-device-ovs-interface.c
+++ b/src/devices/ovs/nm-device-ovs-interface.c
@@ -121,6 +121,43 @@ _is_internal_interface (NMDevice *device)
 	return nm_streq (nm_setting_ovs_interface_get_interface_type (s_ovs_iface), "internal");
 }
 
+static void
+set_platform_mtu_cb (GError *error, gpointer user_data)
+{
+	NMDevice *device = user_data;
+	NMDeviceOvsInterface *self = NM_DEVICE_OVS_INTERFACE (device);
+
+	if (   error
+	    && !g_error_matches (error, NM_UTILS_ERROR, NM_UTILS_ERROR_CANCELLED_DISPOSING)) {
+		_LOGW (LOGD_DEVICE, "could not change mtu of '%s': %s",
+		       nm_device_get_iface (device), error->message);
+	}
+
+	g_object_unref (device);
+}
+
+static gboolean
+set_platform_mtu (NMDevice *device, guint32 mtu)
+{
+	/*
+	 * If the MTU is not set in ovsdb, Open vSwitch will change
+	 * the MTU of an internal interface to match the minimum of
+	 * the other interfaces in the bridge.
+	 */
+	/* FIXME(shutdown): the function should become cancellable so
+	 * that it doesn't need to hold a reference to the device, and
+	 * it can be stopped during shutdown.
+	 */
+	if (_is_internal_interface (device)) {
+		nm_ovsdb_set_interface_mtu (nm_ovsdb_get (),
+		                            nm_device_get_ip_iface (device),
+		                            mtu, set_platform_mtu_cb,
+		                            g_object_ref (device));
+	}
+
+	return NM_DEVICE_CLASS (nm_device_ovs_interface_parent_class)->set_platform_mtu (device, mtu);
+}
+
 static NMActStageReturn
 act_stage3_ip_config_start (NMDevice *device,
                             int addr_family,
@@ -351,4 +388,6 @@ nm_device_ovs_interface_class_init (NMDeviceOvsInterfaceClass *klass)
 	device_class->link_changed = link_changed;
 	device_class->act_stage3_ip_config_start = act_stage3_ip_config_start;
 	device_class->can_unmanaged_external_down = can_unmanaged_external_down;
+	device_class->set_platform_mtu = set_platform_mtu;
+	device_class->get_configured_mtu = nm_device_get_configured_mtu_for_wired;
 }