trying to filter internal subdirs

after.out

vagrant@saio:~$ curl -s "http://saio:8090/v1/AUTH_test/?format=json&prefix=nul&delimiter=l" -H 'x-allow-null-byte: true' | python -m json.tool
[
    {
        "internal": true,
        "subdir": "null"
    }
]
vagrant@saio:~$ curl -s "http://saio:8090/v1/AUTH_test/?format=json&prefix=nul&delimiter=l" | python -m json.tool
[]

before.out

vagrant@saio:~$ curl -s "http://saio:8090/v1/AUTH_test/?format=json&prefix=nul" -H 'x-allow-null-byte: true' | python -m json.tool
[
    {
        "bytes": 0,
        "count": 0,
        "last_modified": "2019-09-27T18:36:42.938450",
        "name": "null\u0000bad"
    },
    {
        "bytes": 0,
        "count": 0,
        "last_modified": "2019-09-27T18:48:02.888630",
        "name": "null\u0000test"
    }
]
vagrant@saio:~$ curl -s "http://saio:8090/v1/AUTH_test/?format=json&prefix=nul&delimiter=l" | python -m json.tool
[
    {
        "subdir": "null"
    }
]

internal_subdir.patch

diff --git a/swift/account/backend.py b/swift/account/backend.py
index dddcbce6e..c02ce95aa 100644
--- a/swift/account/backend.py
+++ b/swift/account/backend.py
@@ -464,7 +464,10 @@ class AccountBroker(DatabaseBroker):
                             delim_force_gte = True
                         dir_name = name[:end + 1]
                         if dir_name != orig_marker:
-                            results.append([dir_name, 0, 0, '0', 1])
+                            if '\x00' in name:
+                                results.append([dir_name, 0, 0, '0', 2])
+                            else:
+                                results.append([dir_name, 0, 0, '0', 1])
                         curs.close()
                         break
                     results.append(row)
diff --git a/swift/account/utils.py b/swift/account/utils.py
index 4e5ebe1ad..af438325a 100644
--- a/swift/account/utils.py
+++ b/swift/account/utils.py
@@ -85,7 +85,10 @@ def account_listing_response(account, req, response_content_type, broker=None,
             in account_list:
         name_ = name.decode('utf8') if six.PY2 else name
         if is_subdir:
-            data.append({'subdir': name_})
+            value = {'subdir': name_}
+            if is_subdir > 1:
+                value['internal'] = True
+            data.append(value)
         else:
             data.append(
                 {'name': name_, 'count': object_count, 'bytes': bytes_used,
diff --git a/swift/common/middleware/listing_formats.py b/swift/common/middleware/listing_formats.py
index a8ca813a1..9814be6cd 100644
--- a/swift/common/middleware/listing_formats.py
+++ b/swift/common/middleware/listing_formats.py
@@ -126,7 +126,7 @@ class ListingFilter(object):
         new_listing = []
         for entry in list(listing):
             name_value = entry.get('name', entry.get('subdir', ''))
-            if '\x00' in name_value:
+            if '\x00' in name_value or entry.get('internal'):
                 if container:
                     self.app.logger.warning(
                         'Container listing for %s/%s had null entry %r',