Return UnknownFrameReceived when appropriate

Author: Lukasa

h2/connection.py

@@ -23,7 +23,7 @@
 from .events import (
     WindowUpdated, RemoteSettingsChanged, PingAcknowledged,
     SettingsAcknowledged, ConnectionTerminated, PriorityUpdated,
-    AlternativeServiceAvailable,
+    AlternativeServiceAvailable, UnknownFrameReceived
 )
 from .exceptions import (
     ProtocolError, NoSuchStreamError, FlowControlError, FrameTooLargeError,
@@ -1934,13 +1934,15 @@ def _receive_unknown_frame(self, frame):
         sure.
 
         RFC 7540 § 5.5 says that we MUST ignore unknown frame types: so we
-        do.
+        do. We do notify the user that we received one, however.
         """
         # All we do here is log.
         self.config.logger.debug(
             "Received unknown extension frame (ID 0x%x)", frame.stream_id
         )
-        return [], []
+        event = UnknownFrameReceived()
+        event.frame = frame
+        return [], [event]
 
     def _local_settings_acked(self):
         """

test/test_basic_logic.py

@@ -1574,8 +1574,10 @@ def test_unknown_frames_are_ignored(self, frame_factory, frame_id):
         f.type = frame_id
 
         events = c.receive_data(f.serialize())
-        assert not events
         assert not c.data_to_send()
+        assert len(events) == 1
+        assert isinstance(events[0], h2.events.UnknownFrameReceived)
+        assert isinstance(events[0].frame, hyperframe.frame.ExtensionFrame)
 
     def test_can_send_goaway_repeatedly(self, frame_factory):
         """