Allow messages inside messages

Bundle Add Message and Request Forward Message, which is part of OpenFlow
1.4, encapsulates an OpenFlow message in side an OpenFlow message.

This patch prepares for this by adding a MsgInMsgBase class, a subclass of
MsgBase which allows its subclasses to include subclasses of either
MsgInMsgBase or MsgBase when when parsing classes from JSON: The MsgBase
class does not allow this.

This change has three parts:
* Remove the assertion in
  ofproto_parser.py:StringifyMixin::cls_from_jsondict_key()
  that cls is not a subclass of MsgBase.

* Pass **additional_args to various stringify.py:StringifyMixin decoder
  methods to make the datapath available when instantiating
  MsgBase subclasses.

* Override _decode_value() in MsgInMsgBase to pass **additional_args
  to decoder. The method in the parent class, StringifyMixin,
  does not pass **additional_args.

  The effect is to pass a datapath argument if
  the class is a subclass of MsgInMsgBase but not if the
  class is a direct subclass of MsgBase.

  By only making messages which allow messages inside them
  subclasses of MsgInMsgBase this allows the datapath
  argument to be passed to the decoder if and only if needed.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/lib/stringify.py

@@ -216,11 +216,11 @@ class StringifyMixin(object):
         return getattr(mod, k)
 
     @classmethod
-    def obj_from_jsondict(cls, jsondict):
+    def obj_from_jsondict(cls, jsondict, **additional_args):
         assert len(jsondict) == 1
         for k, v in jsondict.iteritems():
             obj_cls = cls.cls_from_jsondict_key(k)
-            return obj_cls.from_jsondict(v)
+            return obj_cls.from_jsondict(v, **additional_args)
 
     @classmethod
     def _get_decoder(cls, k, decode_string):
@@ -230,19 +230,20 @@ class StringifyMixin(object):
         return cls._get_default_decoder(decode_string)
 
     @classmethod
-    def _decode_value(cls, k, json_value, decode_string=base64.b64decode):
+    def _decode_value(cls, k, json_value, decode_string=base64.b64decode,
+                      **additional_args):
         return cls._get_decoder(k, decode_string)(json_value)
 
     @classmethod
     def _get_default_decoder(cls, decode_string):
-        def _decode(json_value):
+        def _decode(json_value, **additional_args):
             if isinstance(json_value, (bytes, unicode)):
                 v = decode_string(json_value)
             elif isinstance(json_value, list):
                 v = map(_decode, json_value)
             elif isinstance(json_value, dict):
                 if cls._is_class(json_value):
-                    v = cls.obj_from_jsondict(json_value)
+                    v = cls.obj_from_jsondict(json_value, **additional_args)
                 else:
                     v = _mapdict(_decode, json_value)
                     # XXXhack
@@ -287,7 +288,8 @@ class StringifyMixin(object):
         additional_args (Optional) Additional kwargs for constructor.
         =============== =====================================================
         """
-        decode = lambda k, x: cls._decode_value(k, x, decode_string)
+        decode = lambda k, x: cls._decode_value(k, x, decode_string,
+                                                **additional_args)
         kwargs = cls._restore_args(_mapdict_kv(decode, dict_))
         try:
             return cls(**dict(kwargs, **additional_args))

ryu/ofproto/ofproto_parser.py

@@ -14,6 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import base64
 import collections
 import logging
 import struct
@@ -115,7 +116,6 @@ class StringifyMixin(stringify.StringifyMixin):
     @classmethod
     def cls_from_jsondict_key(cls, k):
         obj_cls = super(StringifyMixin, cls).cls_from_jsondict_key(k)
-        assert not issubclass(obj_cls, MsgBase)
         return obj_cls
 
 
@@ -204,6 +204,14 @@ class MsgBase(StringifyMixin):
         self._serialize_header()
 
 
+class MsgInMsgBase(MsgBase):
+    @classmethod
+    def _decode_value(cls, k, json_value, decode_string=base64.b64decode,
+                      **additional_args):
+        return cls._get_decoder(k, decode_string)(json_value,
+                                                  **additional_args)
+
+
 def msg_pack_into(fmt, buf, offset, *args):
     if len(buf) < offset:
         buf += bytearray(offset - len(buf))