Fix getaddrinfo if dnspython is installed

If dnspython is present in the environment then eventlet
monkeypatches socket.getaddrinfo() with an implementation
which doesn't work for IPv6.

This patch has also been applied to other Openstack
projects such as nova (f2e49ad3) and keystone (3afd9791)
in order to work around the same problem and is
intended to be used in the same way.

Co-authored-by: Hui Xiang <hui.xiang@canonical.com>
Closes-Bug: 1331885
Change-Id: I795e004eac3f032217ff9cb0047f1976306fbb71

glance/cmd/__init__.py

@@ -13,6 +13,41 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import os
+import sys
+
+import oslo.utils.strutils as strutils
+
 from glance import i18n
 
+try:
+    import dns  # NOQA
+except ImportError:
+    dnspython_installed = False
+else:
+    dnspython_installed = True
+
+
+def fix_greendns_ipv6():
+    if dnspython_installed:
+        # All of this is because if dnspython is present in your environment
+        # then eventlet monkeypatches socket.getaddrinfo() with an
+        # implementation which doesn't work for IPv6. What we're checking here
+        # is that the magic environment variable was set when the import
+        # happened.
+        nogreendns = 'EVENTLET_NO_GREENDNS'
+        flag = os.environ.get(nogreendns, '')
+        if 'eventlet' in sys.modules and not strutils.bool_from_string(flag):
+            msg = i18n._("It appears that the eventlet module has been "
+                         "imported prior to setting %s='yes'. It is currently "
+                         "necessary to disable eventlet.greendns "
+                         "if using ipv6 since eventlet.greendns currently "
+                         "breaks with ipv6 addresses. Please ensure that "
+                         "eventlet is not imported prior to this being set.")
+            raise ImportError(msg % (nogreendns))
+
+        os.environ[nogreendns] = 'yes'
+
+
 i18n.enable_lazy()
+fix_greendns_ipv6()

glance/tests/__init__.py

@@ -13,6 +13,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import glance.cmd as glance_cmd
+
+
+glance_cmd.fix_greendns_ipv6()
+
 # See http://code.google.com/p/python-nose/issues/detail?id=373
 # The code below enables tests to work with i18n _() blocks
 import six.moves.builtins as __builtin__

glance/tests/unit/common/test_wsgi_ipv6.py

@@ -0,0 +1,74 @@
+# Copyright 2010-2014 OpenStack Foundation
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import subprocess
+
+from glance.tests import utils as test_utils
+
+
+script = """
+import os
+import sys
+# Spoof module installed
+sys.modules['%s'] = object
+%s
+os.environ['EVENTLET_NO_GREENDNS'] = '%s'
+if 'eventlet' %s in sys.modules:
+    sys.exit(2)
+try:
+    import glance.cmd
+except ImportError:
+    sys.exit(%d)
+else:
+    sys.exit(%d)
+"""
+
+eventlet_no_dns = script % ('fake', '', 'yes', '', 1, 0)
+
+no_eventlet_no_greendns = script % ('dns', '', 'yes', '', 1, 0)
+
+eventlet_no_greendns = script % ('dns', 'import eventlet', 'yes', 'not', 1, 0)
+
+no_eventlet_greendns = script % ('dns', '', 'no', '', 1, 0)
+
+eventlet_greendns = script % ('dns', 'import eventlet', 'no', 'not', 0, 1)
+
+
+class IPv6ServerTest(test_utils.BaseTestCase):
+
+    def test_evnetlet_no_dnspython(self):
+        """Test eventlet imported but dnspython not installed"""
+        rc = subprocess.call(['python', '-c', eventlet_no_dns])
+        self.assertEqual(0, rc)
+
+    def test_no_eventlet_no_greendns(self):
+        """Test eventlet not imported with EVENTLET_NO_GREENDNS='yes'"""
+        rc = subprocess.call(['python', '-c', no_eventlet_no_greendns])
+        self.assertEqual(0, rc)
+
+    def test_eventlet_no_greendns(self):
+        """Test eventlet pre-imported with EVENTLET_NO_GREENDNS='yes'"""
+        rc = subprocess.call(['python', '-c', eventlet_no_greendns])
+        self.assertEqual(0, rc)
+
+    def test_no_eventlet_w_greendns(self):
+        """Test eventlet not imported with EVENTLET_NO_GREENDNS='no'"""
+        rc = subprocess.call(['python', '-c', no_eventlet_greendns])
+        self.assertEqual(0, rc)
+
+    def test_eventlet_w_greendns(self):
+        """Test eventlet pre-imported with EVENTLET_NO_GREENDNS='no'"""
+        rc = subprocess.call(['python', '-c', eventlet_greendns])
+        self.assertEqual(0, rc)