Update DNS plug-in on network change

Restart the DNS plug-in when the primary network changes network
changes. This makes sure any potential host OS DNS configuration
changes get picked up by the DNS plug-in as well.

supervisor/host/network.py

@@ -10,7 +10,9 @@
 from ..dbus.const import (
     DBUS_ATTR_CONNECTION_ENABLED,
     DBUS_ATTR_CONNECTIVITY,
+    DBUS_ATTR_PRIMARY_CONNECTION,
     DBUS_IFACE_NM,
+    DBUS_OBJECT_BASE,
     DBUS_SIGNAL_NM_CONNECTION_ACTIVE_CHANGED,
     ConnectionStateType,
     ConnectivityState,
@@ -148,6 +150,15 @@ async def _check_connectivity_changed(
         connectivity_check: bool | None = changed.get(DBUS_ATTR_CONNECTION_ENABLED)
         connectivity: bool | None = changed.get(DBUS_ATTR_CONNECTIVITY)
 
+        # This potentially updated the DNS configuration. Make sure the DNS plug-in
+        # picks up the latest settings.
+        if (
+            DBUS_ATTR_PRIMARY_CONNECTION in changed
+            and changed[DBUS_ATTR_PRIMARY_CONNECTION]
+            and changed[DBUS_ATTR_PRIMARY_CONNECTION] != DBUS_OBJECT_BASE
+        ):
+            await self.sys_plugins.dns.restart()
+
         if (
             connectivity_check is True
             or DBUS_ATTR_CONNECTION_ENABLED in invalidated