diff --git a/eventlet/support/greendns.py b/eventlet/support/greendns.py
index b6358af..bbb8484 100644
--- a/eventlet/support/greendns.py
+++ b/eventlet/support/greendns.py
@@ -91,6 +91,9 @@ class ResolverProxy(object):
             self._resolver.cache = dns.resolver.Cache()
 
         query = args[0]
+        if query is None:
+            args = list(args)
+            query = args[0] = '0.0.0.0'
         if self._hosts and self._hosts.get(query):
             answer = FakeAnswer()
             record = FakeRecord()
@@ -199,7 +202,11 @@ def getnameinfo(sockaddr, flags):
 
     Currently only supports IPv4.
     """
-    host, port = sockaddr
+    try:
+        host, port = sockaddr
+    except ValueError:
+        # must be ipv6 sockaddr, pretending we don't know how to resolve it
+        raise socket.gaierror(-2, 'name or service not known')
 
     if (flags & socket.NI_NAMEREQD) and (flags & socket.NI_NUMERICHOST):
         # Conflicting flags.  Punt.
@@ -245,7 +252,7 @@ def is_ipv4_addr(host):
     """
     try:
         d1, d2, d3, d4 = map(int, host.split('.'))
-    except ValueError:
+    except (ValueError, AttributeError):
         return False
 
     if 0 <= d1 <= 255 and 0 <= d2 <= 255 and 0 <= d3 <= 255 and 0 <= d4 <= 255:
diff --git a/tests/mock.py b/tests/mock.py
old mode 100755
new mode 100644