From ca12a0c83b7b889fc807cb2dd47356f0fd1253d6 Mon Sep 17 00:00:00 2001
From: Fu Siyuan <siyuan.fu@intel.com>
Date: Wed, 3 May 2017 15:22:08 +0800
Subject: [PATCH] MdeModulePkg: 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.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
---
 .../Universal/Network/Tcp4Dxe/Tcp4Misc.c      |  5 ++-
 .../Universal/Network/Tcp4Dxe/Tcp4Output.c    | 42 +++++++++++++++----
 .../Universal/Network/Tcp4Dxe/Tcp4Proto.h     |  8 +++-
 3 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Misc.c b/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Misc.c
index 1a7c41aa0b..892d19b072 100644
--- a/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Misc.c
+++ b/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Misc.c
@@ -1,7 +1,7 @@
 /** @file
   Misc support routines for tcp.
 
-Copyright (c) 2005 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2005 - 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
 which accompanies this distribution.  The full text of the license may be found at
@@ -78,7 +78,8 @@ TcpInitTcbLocal (
   // First window size is never scaled
   //
   Tcb->RcvWndScale  = 0;
-
+  Tcb->RetxmitSeqMax = 0;
+  
   Tcb->ProbeTimerOn = FALSE;
 }
 
diff --git a/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Output.c b/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Output.c
index 0eec8f07b9..5a3d837e1d 100644
--- a/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Output.c
+++ b/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Output.c
@@ -1,7 +1,7 @@
 /** @file
   TCP output process routines.
     
-Copyright (c) 2005 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2005 - 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
 which accompanies this distribution.  The full text of the license may be found at
@@ -671,17 +671,39 @@ 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)) {
-    DEBUG ((EFI_D_WARN, "TcpRetransmit: retransmission cancelled "
-      "because send window too small for TCB %p\n", Tcb));
+
+  //
+  // 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.
+  //
+  if ((Tcb->SndWndScale != 0) &&
+      (TCP_SEQ_GT (Seq, Tcb->RetxmitSeqMax) || TCP_SEQ_BETWEEN (Tcb->SndWl2 + Tcb->SndWnd, Seq, Tcb->SndWl2 + Tcb->SndWnd + (1 << Tcb->SndWndScale)))) {
+    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",
+      Tcb)
+      );
 
     return 0;
   }
+  
+  Len = MIN (Len, Tcb->SndMss);
 
-  Len   = TCP_SUB_SEQ (Tcb->SndWl2 + Tcb->SndWnd, Seq);
-  Len   = MIN (Len, Tcb->SndMss);
-
-  Nbuf  = TcpGetSegmentSndQue (Tcb, Seq, Len);
+  Nbuf = TcpGetSegmentSndQue (Tcb, Seq, Len);
   if (Nbuf == NULL) {
     return -1;
   }
@@ -691,6 +713,10 @@ TcpRetransmit (
   if (TcpTransmitSegment (Tcb, Nbuf) != 0) {
     goto OnError;
   }
+  
+  if (TCP_SEQ_GT (Seq, Tcb->RetxmitSeqMax)) {
+    Tcb->RetxmitSeqMax = Seq;
+  }
 
   //
   // The retransmitted buffer may be on the SndQue,
diff --git a/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Proto.h b/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Proto.h
index 01d6034b13..49d8a1da3b 100644
--- a/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Proto.h
+++ b/MdeModulePkg/Universal/Network/Tcp4Dxe/Tcp4Proto.h
@@ -1,7 +1,7 @@
 /** @file
   Tcp Protocol header file.
 
-Copyright (c) 2005 - 2010, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2005 - 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
 which accompanies this distribution.  The full text of the license may be found at
@@ -250,6 +250,12 @@ struct _TCP_CB {
   UINT32            TimeWaitTimeout; ///< The TIME_WAIT time out
   UINT32            ConnectTimeout;  ///< The connect establishment time out
 
+  //
+  // RFC7323
+  // Addressing Window Retraction for TCP Window Scale Option.
+  //
+  TCP_SEQNO         RetxmitSeqMax;       ///< Max Seq number in previous retransmission.
+
   //
   // configuration for tcp provided by user
   //