ofproto_protocol: provide a class to describe an openflow version

currently OFP classes takes the Datapath object, which is too complex
for this purpose.  this class, ProtocolDesc, is intended to be
a simpler replacement for that.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Reviewed-by: Satoshi Kobayashi <satoshi-k@stratosphere.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/ofproto/ofproto_protocol.py

@@ -0,0 +1,56 @@
+# Copyright (C) 2014 Nippon Telegraph and Telephone Corporation.
+# Copyright (C) 2014 YAMAMOTO Takashi <yamamoto at valinux co jp>
+#
+# 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.
+
+from . import ofproto_v1_0
+from . import ofproto_v1_0_parser
+from . import ofproto_v1_2
+from . import ofproto_v1_2_parser
+from . import ofproto_v1_3
+from . import ofproto_v1_3_parser
+from . import ofproto_v1_4
+from . import ofproto_v1_4_parser
+
+
+_versions = {
+    ofproto_v1_0.OFP_VERSION: (ofproto_v1_0, ofproto_v1_0_parser),
+    ofproto_v1_2.OFP_VERSION: (ofproto_v1_2, ofproto_v1_2_parser),
+    ofproto_v1_3.OFP_VERSION: (ofproto_v1_3, ofproto_v1_3_parser),
+    ofproto_v1_4.OFP_VERSION: (ofproto_v1_4, ofproto_v1_4_parser),
+}
+
+
+# OF versions supported by every apps in this process (intersection)
+_supported_versions = set(_versions.keys())
+
+
+def set_app_supported_versions(vers):
+    _versions &= set(vers)
+    assert _versions, 'No OpenFlow version is available'
+
+
+class ProtocolDesc(object):
+    """
+    OpenFlow protocol version flavor descriptor
+    """
+
+    def __init__(self, version=None):
+        if version is None:
+            version = max(_supported_versions)
+        self.set_version(version)
+
+    def set_version(self, version):
+        assert version in _supported_versions
+        (self.ofproto, self.ofproto_parser) = _versions[version]