network: Add method to re-activate connections after an update

- When a connection is updated with newer settings, the changes don't reflect
  unless the connection is deactivated and reactivated. Add a convenience method
  to achieve this.

- Don't perform any operation if the connection is not active.

- Wait until connection is deactivated before reactivating

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/network.py

@@ -22,6 +22,7 @@ import collections
 import logging
 import socket
 import struct
+import time
 import uuid
 
 from django.utils.translation import ugettext_lazy as _
@@ -515,6 +516,33 @@ def deactivate_connection(connection_uuid):
     return active_connection
 
 
+def reactivate_connection(connection_uuid):
+    """Find and re-activate a network connection to reflect new changes.
+
+    If connection was not active to begin with, do nothing.
+
+    """
+    try:
+        deactivate_connection(connection_uuid)
+    except ConnectionNotFound:
+        return  # Connection was not active to start with
+
+    # deactivate_connection() is a synchronous call. However, it returns before
+    # the connection is fully deactivated. When re-activating such connections,
+    # sometimes, we get a "Authorization request cancelled" error. So, wait
+    # until the connection is fully deactivated. XXX: Perform proper
+    # asynchronous waiting instead of polling. Also find a way to avoid the
+    # problem altogether.
+    for index in range(10):  # pylint: disable=unused-variable
+        try:
+            get_active_connection(connection_uuid)
+            time.sleep(0.1)
+        except ConnectionNotFound:
+            break
+
+    activate_connection(connection_uuid)
+
+
 def delete_connection(connection_uuid):
     """Delete an exiting connection from network manager.