Make sudo check in ip_lib.IpNetnsCommand.execute optional

If the process runs as root the root_helper and sudo check
are not required.

Closes-Bug: #1393184
Change-Id: I7876ca7e4652f8152d1a8a0015cc897b09b31899

neutron/agent/linux/ip_lib.py

@@ -13,6 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import os
+
 import netaddr
 from oslo.config import cfg
 
@@ -60,10 +62,13 @@ class SubProcessBase(object):
             return self._execute(options, command, args,
                                  log_fail_as_error=self.log_fail_as_error)
 
-    def _as_root(self, options, command, args, use_root_namespace=False):
-        if not self.root_helper:
+    def enforce_root_helper(self):
+        if not self.root_helper and os.geteuid() != 0:
             raise exceptions.SudoRequired()
 
+    def _as_root(self, options, command, args, use_root_namespace=False):
+        self.enforce_root_helper()
+
         namespace = self.namespace if not use_root_namespace else None
 
         return self._execute(options,
@@ -536,8 +541,7 @@ class IpNetnsCommand(IpCommandBase):
                 extra_ok_codes=None):
         ns_params = []
         if self._parent.namespace:
-            if not self._parent.root_helper:
-                raise exceptions.SudoRequired()
+            self._parent.enforce_root_helper()
             ns_params = ['ip', 'netns', 'exec', self._parent.namespace]
 
         env_params = []

neutron/tests/unit/test_linux_ip_lib.py

@@ -13,6 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import os
+
 import mock
 
 from neutron.agent.linux import ip_lib
@@ -191,11 +193,29 @@ class TestSubProcessBase(base.BaseTestCase):
                                              root_helper='sudo',
                                              log_fail_as_error=True)
 
-    def test_as_root_no_root_helper(self):
+    def test_enforce_root_helper_no_root_helper(self):
         base = ip_lib.SubProcessBase()
+        not_root = 42
+        with mock.patch.object(os, 'geteuid', return_value=not_root):
             self.assertRaises(exceptions.SudoRequired,
-                          base._as_root,
-                          [], 'link', ('list',))
+                              base.enforce_root_helper)
+
+    def test_enforce_root_helper_with_root_helper_supplied(self):
+        base = ip_lib.SubProcessBase('sudo')
+        try:
+            base.enforce_root_helper()
+        except exceptions.SudoRequired:
+            self.fail('enforce_root_helper should not raise SudoRequired '
+                      'when a root_helper is supplied.')
+
+    def test_enforce_root_helper_with_no_root_helper_but_root(self):
+        base = ip_lib.SubProcessBase()
+        with mock.patch.object(os, 'geteuid', return_value=0):
+            try:
+                base.enforce_root_helper()
+            except exceptions.SudoRequired:
+                self.fail('enforce_root_helper should not require a root '
+                          'helper when run as root.')
 
 
 class TestIpWrapper(base.BaseTestCase):