Add root access check to cns server.

media/tools/constrained_network_server/traffic_control.py

Index: media/tools/constrained_network_server/traffic_control.py
diff --git a/media/tools/constrained_network_server/traffic_control.py b/media/tools/constrained_network_server/traffic_control.py
index c27a255365b766cdd68ade24204916fc9d02285d..342b01d8e4c3beb6bbbddca73d1995790db4e682 100755
--- a/media/tools/constrained_network_server/traffic_control.py
+++ b/media/tools/constrained_network_server/traffic_control.py
@@ -9,6 +9,7 @@ Traffic to the constrained port is forwarded to a specified server port.
 """
 
 import logging
+import os
 import re
 import subprocess
 
@@ -37,6 +38,18 @@ class TrafficControlError(BaseException):
     self.error = error
 
 
+def CheckRequirements():
+  """Checks if permissions are available to run traffic control commands.
+
+  Raises:
+    TrafficControlError: If permissions to run traffic control commands are not
+    available.
+  """
+  if not os.geteuid() == 0:

[DaleCurtis, 2012/01/10 00:17:59]

Use != 0.

[shadi, 2012/01/10 00:36:39]

I thought (from previous CL) 'not' is preferred over '!='
On 2012/01/10 00:17:59, DaleCurtis wrote:

[DaleCurtis, 2012/01/10 00:40:01]

For objects and boolean statements, but usually not for a primitive type
comparison.

+    _Exec(['sudo', '-n', 'tc'], msg=('Cannot run traffic control commands. '

[DaleCurtis, 2012/01/10 00:17:59]

Add -help just to be sure.

Where is the iptables check? Should have a ['sudo', '-n', 'iptables', '--help'].
You need both tc and iptables.

[shadi, 2012/01/10 00:36:39]

My bad. I thought the purpose was to check if sudo -n works. I forgot this
checks if the commands exists as well :)
On 2012/01/10 00:17:59, DaleCurtis wrote:

+                                     'Please check that you have root access.'))
+
+
 def CreateConstrainedPort(config):
   """Creates a new constrained port.