multi: only report usable ports in switch features

The abstraction layer does not expose any of the data structures
necessary for the user to determine whether or not a port is live or
not. The abstraciton layer therefore needs to make this determination
for the user by filtering ports in the initial feature request, and
surfacing events when ports come up or down.

Author: seliopou

async/Async_SDN.ml

@@ -55,28 +55,33 @@ let create ?max_pending_connections
 let listen_of0x01 (t : t) : Chunk_Controller.h Pipe.Writer.t * e Pipe.Reader.t =
   let module OF = OpenFlow0x01 in
   let recv, send = Pipe.create () in
-  let get_port pd = Int32.of_int_exn pd.OF.PortDescription.port_no in
+  let port_useable pd =
+    let open OF.PortDescription in
+    if pd.config.PortConfig.down
+      then false
+      else not (pd.state.PortState.down)
+  in
+  let get_port pd =
+    if port_useable pd
+      then Some(Int32.of_int_exn pd.OF.PortDescription.port_no)
+      else None
+  in
   send, Pipe.filter_map (OF0x01_Controller.listen_pipe t.sub_0x01 recv)
     ~f:(function
         | `Connect(sw_id, fs) ->
           let sdn_fs =
             { SDN.switch_id = sw_id
-            ; SDN.switch_ports = List.map fs.OF.SwitchFeatures.ports ~f:get_port }
+            ; SDN.switch_ports = List.filter_map fs.OF.SwitchFeatures.ports ~f:get_port }
           in
           Some(`Connect(sw_id, sdn_fs))
         | `Disconnect(sw_id, exn) ->
           Some(`Disconnect(sw_id, exn))
         | `Message(sw_id, (xid, OF.Message.PacketInMsg pi)) ->
           Some(`PacketIn(sw_id, SDN_OpenFlow0x01.to_packetIn pi))
         | `Message (sw_id, (xid, OF.Message.PortStatusMsg ps)) ->
-          let open OF.PortDescription in
           let open OF.PortStatus in
-          let useable =
-            if ps.desc.config.PortConfig.down
-              then false
-              else not (ps.desc.state.PortState.down)
-          in
-          begin match ps.reason, useable with
+          let open OF.PortDescription in
+          begin match ps.reason, port_useable ps.desc with
           | ChangeReason.Add, true
           | ChangeReason.Modify, true ->
             let pt_id = Int32.of_int_exn (ps.desc.port_no) in
@@ -92,28 +97,32 @@ let listen_of0x01 (t : t) : Chunk_Controller.h Pipe.Writer.t * e Pipe.Reader.t =
 
 let listen_of0x04 (t : t) : Chunk_Controller.h Pipe.Writer.t * e Pipe.Reader.t =
   let module OF = OpenFlow0x04 in
+  let open OpenFlow0x04_Core in
   let recv, send = Pipe.create () in
-  let get_port pd = pd.OpenFlow0x04_Core.port_no in
+  let port_useable (pd : portDesc) =
+    if pd.config.port_down
+      then false
+      else not (pd.state.link_down)
+  in
+  let get_port pd =
+    if port_useable pd
+      then Some(pd.port_no)
+      else None
+  in
   send, Pipe.filter_map (OF0x04_Controller.listen_pipe t.sub_0x04 recv)
     ~f:(function
         | `Connect(sw_id, (fs, ps)) ->
           let sdn_fs =
             { SDN.switch_id = sw_id
-            ; SDN.switch_ports = List.map ps ~f:get_port }
+            ; SDN.switch_ports = List.filter_map ps ~f:get_port }
           in
           Some(`Connect(sw_id, sdn_fs))
         | `Disconnect(sw_id, exn) ->
           Some(`Disconnect(sw_id, exn))
         | `Message(sw_id, (xid, OF.Message.PacketInMsg pi)) ->
           Some(`PacketIn(sw_id, SDN_OpenFlow0x04.to_packetIn pi))
         | `Message (sw_id, (xid, OF.Message.PortStatusMsg ps)) ->
-          let open OpenFlow0x04_Core in
-          let useable =
-            if ps.desc.config.port_down
-              then false
-              else not (ps.desc.state.link_down)
-          in
-          begin match ps.reason, useable with
+          begin match ps.reason, port_useable ps.desc with
           | PortAdd, true
           | PortModify, true ->
             Some(`PortUp(sw_id, ps.desc.port_no))