Re: [Patch V2] NetworkPkg: Addressing TCP Window Retraction when window scale factor is used.

["Ye, Ting" <ting.ye@intel.com>]

Reviewed-by: Ye Ting <ting.ye@intel.com>


-----Original Message-----
From: Fu, Siyuan 
Sent: Friday, May 05, 2017 9:56 AM
To: edk2-devel@lists.01.org
Cc: Wu, Jiaxin <jiaxin.wu@intel.com>; Andrey Tepin <atepin@kraftway.ru>; Ye, Ting <ting.ye@intel.com>
Subject: [Patch V2] NetworkPkg: Addressing TCP Window Retraction when window scale factor is used.

The RFC1323 which defines the TCP window scale option has been obsoleted by RFC7323.
This patch is to follow the RFC7323 to address the TCP window retraction problem when a non-zero scale factor is used.
The changes has been test in high packet loss rate network by using HTTP boot and iSCSI file read/write.

Cc: Wu Jiaxin <jiaxin.wu@intel.com>
Cc: Andrey Tepin <atepin@kraftway.ru>
Cc: Ye Ting <ting.ye@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
---
 NetworkPkg/TcpDxe/TcpMisc.c   |  3 ++-
 NetworkPkg/TcpDxe/TcpOutput.c | 33 ++++++++++++++++++++++++++++-----  NetworkPkg/TcpDxe/TcpProto.h  |  8 +++++++-
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/NetworkPkg/TcpDxe/TcpMisc.c b/NetworkPkg/TcpDxe/TcpMisc.c index a8592c9..4435036 100644
--- a/NetworkPkg/TcpDxe/TcpMisc.c
+++ b/NetworkPkg/TcpDxe/TcpMisc.c
@@ -2,7 +2,7 @@
   Misc support routines for TCP driver.
 
   (C) Copyright 2014 Hewlett-Packard Development Company, L.P.<BR>
-  Copyright (c) 2009 - 2016, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2017, Intel Corporation. All rights 
+ reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License @@ -86,6 +86,7 @@ TcpInitTcbLocal (
   // First window size is never scaled
   //
   Tcb->RcvWndScale  = 0;
+  Tcb->RetxmitSeqMax = 0;
 
   Tcb->ProbeTimerOn = FALSE;
 }
diff --git a/NetworkPkg/TcpDxe/TcpOutput.c b/NetworkPkg/TcpDxe/TcpOutput.c index a46cb60..f3dacf3 100644
--- a/NetworkPkg/TcpDxe/TcpOutput.c
+++ b/NetworkPkg/TcpDxe/TcpOutput.c
@@ -1,7 +1,7 @@
 /** @file
   TCP output process routines.
 
-  Copyright (c) 2009 - 2016, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2017, Intel Corporation. All rights 
+ reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License @@ -664,7 +664,27 @@ TcpRetransmit (
   // 2. Must in the current send window
   // 3. Will not change the boundaries of queued segments.
   //
-  if (TCP_SEQ_LT (Tcb->SndWl2 + Tcb->SndWnd, Seq)) {
+  
+  if ((Tcb->SndWndScale != 0) &&
+      (TCP_SEQ_GT (Seq, Tcb->RetxmitSeqMax) || TCP_SEQ_GT (Tcb->SndWl2 + Tcb->SndWnd + (1 << Tcb->SndWndScale), Seq))) {
+    //
+    // Handle the Window Retraction if TCP window scale is enabled according to RFC7323:
+    //   On first retransmission, or if the sequence number is out of
+    //   window by less than 2^Rcv.Wind.Shift, then do normal
+    //   retransmission(s) without regard to the receiver window as long
+    //   as the original segment was in window when it was sent.
+    //
+    Len = TCP_SUB_SEQ (Tcb->SndNxt, Seq);
+    DEBUG (
+      (EFI_D_WARN,
+      "TcpRetransmit: retransmission without regard to the receiver window for TCB %p\n",
+      Tcb)
+      );
+    
+  } else if (TCP_SEQ_GEQ (Tcb->SndWl2 + Tcb->SndWnd, Seq)) {
+    Len = TCP_SUB_SEQ (Tcb->SndWl2 + Tcb->SndWnd, Seq);
+    
+  } else {
     DEBUG (
       (EFI_D_WARN,
       "TcpRetransmit: retransmission cancelled because send window too small for TCB %p\n", @@ -674,10 +694,9 @@ TcpRetransmit (
     return 0;
   }
 
-  Len   = TCP_SUB_SEQ (Tcb->SndWl2 + Tcb->SndWnd, Seq);
-  Len   = MIN (Len, Tcb->SndMss);
+  Len = MIN (Len, Tcb->SndMss);
 
-  Nbuf  = TcpGetSegmentSndQue (Tcb, Seq, Len);
+  Nbuf = TcpGetSegmentSndQue (Tcb, Seq, Len);
   if (Nbuf == NULL) {
     return -1;
   }
@@ -688,6 +707,10 @@ TcpRetransmit (
     goto OnError;
   }
 
+  if (TCP_SEQ_GT (Seq, Tcb->RetxmitSeqMax)) {
+    Tcb->RetxmitSeqMax = Seq;
+  }
+
   //
   // The retransmitted buffer may be on the SndQue,
   // trim TCP head because all the buffers on SndQue diff --git a/NetworkPkg/TcpDxe/TcpProto.h b/NetworkPkg/TcpDxe/TcpProto.h index ee35134..81397d7 100644
--- a/NetworkPkg/TcpDxe/TcpProto.h
+++ b/NetworkPkg/TcpDxe/TcpProto.h
@@ -1,7 +1,7 @@
 /** @file
   TCP protocol header file.
 
-  Copyright (c) 2009 - 2012, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2017, Intel Corporation. All rights 
+ reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License @@ -316,6 +316,12 @@ struct _TCP_CONTROL_BLOCK {
   TCP_SEQNO         LossRecover;  ///< Recover point for retxmit.
 
   //
+  // RFC7323
+  // Addressing Window Retraction for TCP Window Scale Option.
+  //
+  TCP_SEQNO         RetxmitSeqMax;       ///< Max Seq number in previous retransmission.
+
+  //
   // configuration parameters, for EFI_TCP4_PROTOCOL specification
   //
   UINT32            KeepAliveIdle;   ///< Idle time before sending first probe.
--
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