The Dhcp4.TransmitReceive() API should be able to use at any time
according to UEFI spec. While in classless addressing network, the
netmask must be explicitly provided together with the station address.
But if the DHCP instance haven't be configured with a valid netmask,
we need compute it according to the classful addressing rule. In such
case, if the user configures with class E IP address, ASSERT will
happen, we need to handle this case and return error status code.

Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wang Fan <fan.wang@intel.com>
---
 MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Impl.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Impl.c b/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Impl.c
index 1db4c66..65ea64e 100644
--- a/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Impl.c
+++ b/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Impl.c
@@ -1173,12 +1173,14 @@ EfiDhcp4Build (
   Callback by UdpIoCreatePort() when creating UdpIo for this Dhcp4 instance.
 
   @param[in] UdpIo      The UdpIo being created.
   @param[in] Context    Dhcp4 instance.
 
-  @retval EFI_SUCCESS   UdpIo is configured successfully.
-  @retval other         Other error occurs.
+  @retval EFI_SUCCESS            UdpIo is configured successfully.
+  @retval EFI_INVALID_PARAMETER  Class E IP address is not supported or other parameters
+                                 are not valid.
+  @retval other                  Other error occurs.
 **/
 EFI_STATUS
 EFIAPI
 Dhcp4InstanceConfigUdpIo (
   IN UDP_IO       *UdpIo,
@@ -1216,11 +1218,25 @@ Dhcp4InstanceConfigUdpIo (
     // provided together with the station address.
     // If the DHCP instance haven't be configured with a valid netmask, we could only
     // compute it according to the classful addressing rule.
     //
     Class = NetGetIpClass (ClientAddr);
+
+    //
+    //  IP4_ADDR_CLASSA       1     // Deprecated
+    //  IP4_ADDR_CLASSB       2     // Deprecated
+    //  IP4_ADDR_CLASSC       3     // Deprecated
+    //  IP4_ADDR_CLASSD       4
+    //  IP4_ADDR_CLASSE       5
+    //
+    //  Class E IP address is not supported here!
+    //
     ASSERT (Class < IP4_ADDR_CLASSE);
+    if (Class == IP4_ADDR_CLASSE) {
+      return EFI_INVALID_PARAMETER;
+    }
+
     SubnetMask = gIp4AllMasks[Class << 3];
   } else {
     SubnetMask = DhcpSb->Netmask;
   }
 
-- 
1.9.5.msysgit.1

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