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If there are no ready segments, leave the tx window alone
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Before, we set it to size zero, preventing us from sending any further
data. See: mirage#140
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@talex5
talex5 committed Jun 5, 2015
1 parent 36edd11 commit 18f4946
Showing 1 changed file with 3 additions and 3 deletions.
6 changes: 3 additions & 3 deletions tcp/segment.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -97,9 +97,9 @@ module Rx(Time:V1_LWT.TIME) = struct
with Not_found -> false *)

(* Determine the transmit window, from the last segment *)
let window q =
let window ~default q =
try (S.max_elt q).window
with Not_found -> 0
with Not_found -> default

let is_empty q = S.is_empty q.segs

Expand Down Expand Up @@ -140,7 +140,7 @@ module Rx(Time:V1_LWT.TIME) = struct
let tx_ack =
if seg.ack then begin
StateTick.tick q.state (State.Recv_ack seg.ack_number);
let win = window ready in
let win = window ~default:(Window.ack_win q.wnd) ready in
let data_in_flight = Window.tx_inflight q.wnd in
let seq_has_changed = (Window.ack_seq q.wnd) <> seg.ack_number in
let win_has_changed = (Window.ack_win q.wnd) <> win in
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2 comments on commit 18f4946

@yomimono
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In context, I think ready in window ready refers to received segments, which doesn't seem like a great place to get our advertised receive window from (since our ability to process the incoming data should inform this, rather than the remote end's ability to process incoming data).

@talex5
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@talex5 talex5 commented on 18f4946 Jun 6, 2015

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Now I'm confused. ready is the received segment, but I thought win was being used to set our transmit window? The code just below does:

       let win_has_changed = (Window.ack_win q.wnd) <> win in
       ...
       Lwt_mvar.put q.tx_ack (seg.ack_number, win)

Window.tx_ack does:

(* An ACK was received - use it to adjust cwnd *)
let tx_ack t r win =
  set_tx_wnd t win;
  ...

Window.tx_ack is called from Segment.Tx.rto_t, which gets win as:

let win = Window.ack_win q.wnd in

So what's the difference between ack_win and tx_win?

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