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..8de3ef0034c43ae104ef28cb18756b6055edd946 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 +38,22 @@ 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 os.geteuid() != 0:
+    _Exec(['sudo', '-n', 'tc', '-help'],
+          msg=('Cannot run traffic control \'tc\' command. '

[DaleCurtis, 2012/01/10 21:35:08]

Better written as "Cannot run 'tc' command. Traffic Control must be run as root
or have password-less sudo access to this command."

+              'Please check that you have root access.'))
+    _Exec(['sudo', '-n', 'iptables', '-help'],
+          msg=('Cannot run traffic control \'iptables\' command. '
+               'Please check that you have root access.'))
+
+
 def CreateConstrainedPort(config):
   """Creates a new constrained port.