Re: [PATCH 4/6] MdeModulePkg/DxeNetLib: Rewrite NetblockChecksum function logic

["Fu, Siyuan" <siyuan.fu@intel.com>]

Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>


-----Original Message-----
From: Wu, Hao A 
Sent: 2016年12月14日 19:27
To: edk2-devel@lists.01.org
Cc: Wu, Hao A <hao.a.wu@intel.com>; Fu, Siyuan <siyuan.fu@intel.com>; Ye, Ting <ting.ye@intel.com>; Wu, Jiaxin <jiaxin.wu@intel.com>
Subject: [PATCH 4/6] MdeModulePkg/DxeNetLib: Rewrite NetblockChecksum function logic

This commit rewrites the logic for NetblockChecksum. It processes the checksum of the left-over byte first to prevent possible mis-reports by static code checkers.

Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Ye Ting <ting.ye@intel.com>
Cc: Wu Jiaxin <jiaxin.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Library/DxeNetLib/NetBuffer.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/MdeModulePkg/Library/DxeNetLib/NetBuffer.c b/MdeModulePkg/Library/DxeNetLib/NetBuffer.c
index bbbdbc0..95cb717 100644
--- a/MdeModulePkg/Library/DxeNetLib/NetBuffer.c
+++ b/MdeModulePkg/Library/DxeNetLib/NetBuffer.c
@@ -1,7 +1,7 @@
 /** @file
   Network library functions providing net buffer operation support.
 
-Copyright (c) 2005 - 2010, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2005 - 2016, 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 @@ -1661,6 +1661,13 @@ NetblockChecksum (
 
   Sum = 0;
 
+  //
+  // Add left-over byte, if any
+  //
+  if (Len % 2 != 0) {
+    Sum += *(Bulk + Len - 1);
+  }
+
   while (Len > 1) {
     Sum += *(UINT16 *) Bulk;
     Bulk += 2;
@@ -1668,13 +1675,6 @@ NetblockChecksum (
   }
 
   //
-  // Add left-over byte, if any
-  //
-  if (Len > 0) {
-    Sum += *(UINT8 *) Bulk;
-  }
-
-  //
   // Fold 32-bit sum to 16 bits
   //
   while ((Sum >> 16) != 0) {
--
1.9.5.msysgit.0