Don't delegate valid_frame_rsv to extensions; it's a weird interface and we can figure it out from the extension metadata.

README.md

@@ -281,32 +281,8 @@ their use of RSV bits are not activated.
 #### *Session*
 
 The *Session* API must be implemented by both client and server sessions. It
-contains three methods: `valid_frame_rsv(frame)`,
-`process_incoming_message(message)` and `process_outgoing_message(message)`.
-
-```rb
-session.valid_frame_rsv(frame)
-```
-
-This takes a *Frame* as defined above, and returns a response indicating which
-RSV bits are allowed to be set on the frame. (If a session is having this method
-called, the session is active and should its bits can be used.) For example, the
-`permessage-deflate` extension allows the RSV1 bit to be set on `text` and
-`binary` frames, and implements this method like this:
-
-```rb
-def valid_frame_rsv(frame)
-  if [1, 2].include?(frame.opcode)
-    {:rsv1 => true, :rsv2 => false, :rsv3 => false}
-  else
-    {:rsv1 => false, :rsv2 => false, :rsv3 => false}
-  end
-end
-```
-
-Note that returning `false` for an `rsvX` field does not mean the session is
-forbidding its use; the framework assumes all RSV bits are banned unless a
-session indicates otherwise.
+contains three methods: `process_incoming_message(message)` and
+`process_outgoing_message(message)`.
 
 ```rb
 message = session.process_incoming_message(message)

lib/websocket/extensions.rb

@@ -5,6 +5,8 @@ module WebSocket
 
     ExtensionError = Class.new(ArgumentError)
 
+    MESSAGE_OPCODES = [1, 2]
+
     def initialize
       @rsv1 = @rsv2 = @rsv3 = nil
 
@@ -118,11 +120,12 @@ module WebSocket
     def valid_frame_rsv(frame)
       allowed = {:rsv1 => false, :rsv2 => false, :rsv3 => false}
 
-      @sessions.each do |ext, session|
-        policy = session.valid_frame_rsv(frame)
-        allowed[:rsv1] ||= policy[:rsv1]
-        allowed[:rsv2] ||= policy[:rsv2]
-        allowed[:rsv3] ||= policy[:rsv3]
+      if MESSAGE_OPCODES.include?(frame.opcode)
+        @sessions.each do |ext, session|
+          allowed[:rsv1] ||= ext.rsv1
+          allowed[:rsv2] ||= ext.rsv2
+          allowed[:rsv3] ||= ext.rsv3
+        end
       end
 
       (allowed[:rsv1] || !frame.rsv1) &&