[PATCH v2 4/6] MdeModulePkg/DxeNetLib: Rewrite NetblockChecksum function logic

[Hao Wu <hao.a.wu@intel.com>]

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.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
Reviewed-by: Wu Jiaxin <jiaxin.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