1. Introduce PcdTftpBlockSize to let platform DSC customize block size.

2. Roll back the default block size to handle all link layers.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10803 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Universal/Network/UefiPxeBcDxe/PxeBcImpl.c

@@ -347,7 +347,19 @@ EfiPxeBcStart (
     return Status;
   }
 
-  Private->BlockSize   = 0x8000;
+
+  //
+  // Configure block size for TFTP as a default value to handle all link layers.
+  // 
+  Private->BlockSize   = (UINTN) (MIN (Private->Ip4MaxPacketSize, PXEBC_DEFAULT_PACKET_SIZE) - 
+                           PXEBC_DEFAULT_UDP_OVERHEAD_SIZE - PXEBC_DEFAULT_TFTP_OVERHEAD_SIZE);
+  //
+  // If PcdTftpBlockSize is set to non-zero, override the default value.
+  //
+  if (PcdGet64 (PcdTftpBlockSize) != 0) {
+    Private->BlockSize   = (UINTN) PcdGet64 (PcdTftpBlockSize);
+  }
+  
   Private->AddressIsOk = FALSE;
 
   ZeroMem (Mode, sizeof (EFI_PXE_BASE_CODE_MODE));

MdeModulePkg/Universal/Network/UefiPxeBcDxe/PxeBcImpl.h

@@ -40,6 +40,7 @@ typedef struct _PXEBC_PRIVATE_DATA  PXEBC_PRIVATE_DATA;
 #include <Library/BaseLib.h>
 #include <Library/NetLib.h>
 #include <Library/DpcLib.h>
+#include <Library/PcdLib.h>
 
 #include "PxeBcDriver.h"
 #include "PxeBcDhcp.h"

MdeModulePkg/Universal/Network/UefiPxeBcDxe/UefiPxeBcDxe.inf

@@ -64,6 +64,7 @@
   DebugLib
   NetLib
   DpcLib
+  PcdLib
 
 [Guids]
   gEfiSmbiosTableGuid                              # ALWAYS_CONSUMED
@@ -83,3 +84,6 @@
   gEfiNetworkInterfaceIdentifierProtocolGuid_31    ## SOMETIMES_CONSUMES
   gEfiIp4ServiceBindingProtocolGuid                # PROTOCOL ALWAYS_CONSUMED
   gEfiIp4ProtocolGuid                              # PROTOCOL ALWAYS_CONSUMED
+
+[Pcd]  
+  gEfiMdeModulePkgTokenSpaceGuid.PcdTftpBlockSize     ## CONSUMES