NetworkPkg/IpSecDxe: Generate SPI randomly and correct IKE_SPI_BASE value

This path made the following update:
* Generate SPI randomly.
* Correct IKE_SPI_BASE value according RFC 4302/4303.

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

NetworkPkg/IpSecDxe/IkeCommon.h

@@ -1,7 +1,7 @@
 /** @file
   Common operation of the IKE.
 
-  Copyright (c) 2010 - 2015, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2010 - 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
@@ -39,7 +39,7 @@
 #define IKE_DEFAULT_TIMEOUT_INTERVAL  10000 // 10s
 #define IKE_NONCE_SIZE                16
 #define IKE_MAX_RETRY                 4
-#define IKE_SPI_BASE                  0x10000
+#define IKE_SPI_BASE                  0x100
 #define IKE_PAYLOAD_SIGNATURE         SIGNATURE_32('I','K','E','P')
 #define IKE_PAYLOAD_BY_PACKET(a)      CR(a,IKE_PAYLOAD,ByPacket,IKE_PAYLOAD_SIGNATURE)
 
@@ -130,14 +130,20 @@ IkePayloadFree (
   );
 
 /**
-  Generate an unused SPI
-
-  @return a SPI in 4 bytes.
+  Generate an new SPI.
+  
+  @param[in]      IkeSaSession   Pointer to IKEV2_SA_SESSION related to this Child SA 
+                                 Session.
+  @param[in out]  SpiValue       Pointer to the new generated SPI value. 
+                              
+  @retval EFI_SUCCESS         The operation performs successfully.
+  @retval Otherwise           The operation is failed.
 
 **/
-UINT32
+EFI_STATUS
 IkeGenerateSpi (
-  VOID
+  IN  IKEV2_SA_SESSION         *IkeSaSession,
+  OUT UINT32                   *SpiValue
   );
 
 /**