manager: fix wrongly removing DNS configuration on shutdown

When NetworkManager exits, it must preserve the DNS configuration of
devices that are left up.

Fixes: 9498ea507e
(cherry picked from commit 2158d6a5a8)

src/devices/nm-device.c

@@ -2600,12 +2600,14 @@ nm_device_get_enslaved (NMDevice *self)
 /**
  * nm_device_removed:
  * @self: the #NMDevice
+ * @unconfigure_ip_config: whether to clear the IP config objects
+ *   of the device (provided, it is still not cleared at this point).
  *
  * Called by the manager when the device was removed. Releases the device from
  * the master in case it's enslaved.
  */
 void
-nm_device_removed (NMDevice *self)
+nm_device_removed (NMDevice *self, gboolean unconfigure_ip_config)
 {
 	NMDevicePrivate *priv;
 
@@ -2618,6 +2620,9 @@ nm_device_removed (NMDevice *self)
 		nm_device_master_release_one_slave (priv->master, self, FALSE, NM_DEVICE_STATE_REASON_CONNECTION_ASSUMED);
 	}
 
+	if (!unconfigure_ip_config)
+		return;
+
 	/* Clean up IP configs; this does not actually deconfigure the
 	 * interface, it just clears the configuration to which policy
 	 * is reacting via NM_DEVICE_IP4_CONFIG_CHANGED/NM_DEVICE_IP6_CONFIG_CHANGED

src/devices/nm-device.h

@@ -385,7 +385,7 @@ gboolean        nm_device_has_unmodified_applied_connection (NMDevice *self,
                                                              NMSettingCompareFlags compare_flags);
 NMSetting *     nm_device_get_applied_setting   (NMDevice *dev, GType setting_type);
 
-void            nm_device_removed               (NMDevice *dev);
+void            nm_device_removed               (NMDevice *self, gboolean unconfigure_ip_config);
 
 gboolean        nm_device_is_available          (NMDevice *dev, NMDeviceCheckDevAvailableFlags flags);
 gboolean        nm_device_has_carrier           (NMDevice *dev);

src/nm-manager.c

@@ -833,13 +833,13 @@ remove_device (NMManager *self,
                gboolean allow_unmanage)
 {
 	NMManagerPrivate *priv = NM_MANAGER_GET_PRIVATE (self);
+	gboolean unmanage = FALSE;
 
 	_LOGD (LOGD_DEVICE, "(%s): removing device (allow_unmanage %d, managed %d)",
 	       nm_device_get_iface (device), allow_unmanage, nm_device_get_managed (device, FALSE));
 
 	if (allow_unmanage && nm_device_get_managed (device, FALSE)) {
 		NMActRequest *req = nm_device_get_act_request (device);
-		gboolean unmanage = FALSE;
 
 		/* Leave activated interfaces up when quitting so their configuration
 		 * can be taken over when NM restarts.  This ensures connectivity while
@@ -869,7 +869,18 @@ remove_device (NMManager *self,
 	priv->devices = g_slist_remove (priv->devices, device);
 
 	if (nm_device_is_real (device)) {
-		nm_device_removed (device);
+		gboolean unconfigure_ip_config = !quitting || unmanage;
+
+		/* When we don't unmanage the device on shutdown, we want to preserve the DNS
+		 * configuration in resolv.conf. For that, we must leak the configuration
+		 * in NMPolicy/NMDnsManager. We do that, by emitting the device-removed signal
+		 * with device's ip-config object still uncleared. In that case, NMPolicy
+		 * never learns to unconfigure the ip-config objects and does not remove them
+		 * from DNS on shutdown (which is ugly, because we don't cleanup the memory
+		 * properly).
+		 *
+		 * Control that by passing @unconfigure_ip_config.  */
+		nm_device_removed (device, unconfigure_ip_config);
 
 		g_signal_emit (self, signals[DEVICE_REMOVED], 0, device);
 		_notify (self, PROP_DEVICES);