Use the ACK module to send the challenge ACK

Author: Lucas Pluvinage

src/tcp/flow.ml

@@ -23,9 +23,9 @@ module Log = (val Logs.src_log src : Logs.LOG)
 module Make(Ip: Tcpip.Ip.S)(Time:Mirage_time.S)(Clock:Mirage_clock.MCLOCK)(Random:Mirage_random.S) =
 struct
 
-  module RXS = Segment.Rx(Time)
-  module TXS = Segment.Tx(Time)(Clock)
   module ACK = Ack.Immediate
+  module RXS = Segment.Rx(Time)(ACK)
+  module TXS = Segment.Tx(Time)(Clock)
   module UTX = User_buffer.Tx(Time)(Clock)
   module WIRE = Wire.Make(Ip)
   module STATE = State.Make(Time)
@@ -358,11 +358,11 @@ struct
     let txq, _tx_t =
       TXS.create ~xmit:(Tx.xmit_pcb t.ip id) ~wnd ~state ~rx_ack ~tx_ack ~tx_wnd_update
     in
-    (* The user application transmit buffer *)
-    let utx = UTX.create ~wnd ~txq ~max_size:16384l in
-    let rxq = RXS.create ~rx_data ~send_ack ~wnd ~state ~tx_ack in
     (* Set up ACK module *)
     let ack = ACK.t ~send_ack ~last:(Sequence.succ rx_isn) in
+    (* The user application transmit buffer *)
+    let utx = UTX.create ~wnd ~txq ~max_size:16384l in
+    let rxq = RXS.create ~rx_data ~ack ~wnd ~state ~tx_ack in
     (* Set up the keepalive state if requested *)
     let keepalive = match keepalive with
       | None -> None

src/tcp/segment.ml

@@ -55,7 +55,7 @@ let rec reset_seq segs =
    It also looks for control messages and dispatches them to
    the Rtx queue to ack messages or close channels.
 *)
-module Rx(Time:Mirage_time.S) = struct
+module Rx(Time:Mirage_time.S)(ACK: Ack.M) = struct
   open Tcp_packet
   module StateTick = State.Make(Time)
 
@@ -84,15 +84,15 @@ module Rx(Time:Mirage_time.S) = struct
   type t = {
     mutable segs: S.t;
     rx_data: (Cstruct.t list option * Sequence.t option) Lwt_mvar.t; (* User receive channel *)
-    send_ack: Sequence.t Lwt_mvar.t;
+    ack: ACK.t;
     tx_ack: (Sequence.t * int) Lwt_mvar.t; (* Acks of our transmitted segs *)
     wnd: Window.t;
     state: State.t;
   }
 
-  let create ~rx_data ~send_ack ~wnd ~state ~tx_ack =
+  let create ~rx_data ~ack ~wnd ~state ~tx_ack =
     let segs = S.empty in
-    { segs; rx_data; send_ack; tx_ack; wnd; state }
+    { segs; rx_data; ack; tx_ack; wnd; state }
 
   let pp fmt t =
     let pp_v fmt seg =
@@ -136,9 +136,7 @@ module Rx(Time:Mirage_time.S) = struct
 
   let send_challenge_ack q =
     (* TODO:  rfc5961 ACK Throttling *)
-    if Lwt_mvar.is_empty q.send_ack
-      then Lwt_mvar.put q.send_ack Sequence.zero
-      else Lwt.return_unit
+    ACK.pushack q.ack Sequence.zero
 
   (* Given an input segment, the window information, and a receive
      queue, update the window, extract any ready segments into the

src/tcp/segment.mli

@@ -24,7 +24,7 @@
     the Rtx queue to ack messages or close channels.
 *)
 
-module Rx (T:Mirage_time.S) : sig
+module Rx (T:Mirage_time.S)(ACK:Ack.M) : sig
 
   type segment = { header: Tcp_packet.t; payload: Cstruct.t }
   (** Individual received TCP segment *)
@@ -38,7 +38,7 @@ module Rx (T:Mirage_time.S) : sig
 
   val create:
     rx_data:(Cstruct.t list option * Sequence.t option) Lwt_mvar.t ->
-    send_ack:Sequence.t Lwt_mvar.t ->
+    ack:ACK.t ->
     wnd:Window.t ->
     state:State.t ->
     tx_ack:(Sequence.t * int) Lwt_mvar.t ->