NetworkPkg/Dhcp6Dxe/Dhcp6Driver.c - third_party/edk2 - Git at Google

 /** @file
   Driver Binding functions and Service Binding functions
   implementationfor for Dhcp6 Driver.

   Copyright (c) 2009 - 2012, 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
   http://opensource.org/licenses/bsd-license.php.

   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

 **/

 #include "Dhcp6Impl.h"


 EFI_DRIVER_BINDING_PROTOCOL gDhcp6DriverBinding = {
   Dhcp6DriverBindingSupported,
   Dhcp6DriverBindingStart,
   Dhcp6DriverBindingStop,
   0xa,
   NULL,
   NULL
 };

 EFI_SERVICE_BINDING_PROTOCOL gDhcp6ServiceBindingTemplate = {
   Dhcp6ServiceBindingCreateChild,
   Dhcp6ServiceBindingDestroyChild
 };

 /**
   Configure the default Udp6Io to receive all the DHCP6 traffic
   on this network interface.

   @param[in]  UdpIo                  The pointer to Udp6Io to be configured.
   @param[in]  Context                The pointer to the context.

   @retval EFI_SUCCESS            The Udp6Io is successfully configured.
   @retval Others                 Failed to configure the Udp6Io.

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6ConfigureUdpIo (
   IN UDP_IO                 *UdpIo,
   IN VOID                   *Context
   )
 {
   EFI_UDP6_PROTOCOL         *Udp6;
   EFI_UDP6_CONFIG_DATA      *Config;

   Udp6   = UdpIo->Protocol.Udp6;
   Config = &(UdpIo->Config.Udp6);

   ZeroMem (Config, sizeof (EFI_UDP6_CONFIG_DATA));

   //
   // Set Udp6 configure data for the Dhcp6 instance.
   //
   Config->AcceptPromiscuous  = FALSE;
   Config->AcceptAnyPort      = FALSE;
   Config->AllowDuplicatePort = FALSE;
   Config->TrafficClass       = 0;
   Config->HopLimit           = 128;
   Config->ReceiveTimeout     = 0;
   Config->TransmitTimeout    = 0;

   //
   // Configure an endpoint of client(0, 546), server(0, 0), the addresses
   // will be overridden later. Note that we MUST not limit RemotePort.
   // More details, refer to RFC 3315 section 5.2.
   //
   Config->StationPort        = DHCP6_PORT_CLIENT;
   Config->RemotePort         = 0;

   return Udp6->Configure (Udp6, Config);;
 }


 /**
   Destroy the Dhcp6 service. The Dhcp6 service may be partly initialized,
   or partly destroyed. If a resource is destroyed, it is marked as such in
   case the destroy failed and being called again later.

   @param[in, out]  Service       The pointer to Dhcp6 service to be destroyed.

 **/
 VOID
 Dhcp6DestroyService (
   IN OUT DHCP6_SERVICE          *Service
   )
 {
   //
   // All children instances should have been already destroyed here.
   //
   ASSERT (Service->NumOfChild == 0);

   if (Service->ClientId != NULL) {
     FreePool (Service->ClientId);
   }

   if (Service->UdpIo != NULL) {
     UdpIoFreeIo (Service->UdpIo);
   }

   FreePool (Service);
 }


 /**
   Create a new Dhcp6 service for the Nic controller.

   @param[in]  Controller             The controller to be installed DHCP6 service
                                      binding protocol.
   @param[in]  ImageHandle            The image handle of the Dhcp6 driver.
   @param[out] Service                The return pointer of the new Dhcp6 service.

   @retval EFI_SUCCESS            The Dhcp6 service is created successfully.
   @retval EFI_DEVICE_ERROR       An unexpected system or network error occurred.
   @retval EFI_OUT_OF_RESOURCES   Failed to allocate resource.

 **/
 EFI_STATUS
 Dhcp6CreateService (
   IN  EFI_HANDLE            Controller,
   IN  EFI_HANDLE            ImageHandle,
   OUT DHCP6_SERVICE         **Service
   )
 {
   DHCP6_SERVICE             *Dhcp6Srv;
   EFI_STATUS                Status;

   *Service = NULL;
   Dhcp6Srv = AllocateZeroPool (sizeof (DHCP6_SERVICE));

   if (Dhcp6Srv == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }

   //
   // Open the SNP protocol to get mode data later.
   //
   Dhcp6Srv->Snp = NULL;
   NetLibGetSnpHandle (Controller, &Dhcp6Srv->Snp);
   if (Dhcp6Srv->Snp == NULL) {
     FreePool (Dhcp6Srv);
     return EFI_DEVICE_ERROR;
   }

   //
   // Initialize the fields of the new Dhcp6 service.
   //
   Dhcp6Srv->Signature       = DHCP6_SERVICE_SIGNATURE;
   Dhcp6Srv->Controller      = Controller;
   Dhcp6Srv->Image           = ImageHandle;
   Dhcp6Srv->Xid             = (0xffffff & NET_RANDOM (NetRandomInitSeed ()));

   CopyMem (
     &Dhcp6Srv->ServiceBinding,
     &gDhcp6ServiceBindingTemplate,
     sizeof (EFI_SERVICE_BINDING_PROTOCOL)
     );

   //
   // Locate Ip6->Ip6Config and store it for get IP6 Duplicate Address Detection transmits.
   //
   Status = gBS->HandleProtocol (
                   Controller,
                   &gEfiIp6ConfigProtocolGuid,
                   (VOID **) &Dhcp6Srv->Ip6Cfg
                   );
   if (EFI_ERROR (Status)) {
     FreePool (Dhcp6Srv);
     return Status;
   }

   //
   // Generate client Duid: If SMBIOS system UUID is located, generate DUID in DUID-UUID format.
   // Otherwise, in DUID-LLT format.
   //
   Dhcp6Srv->ClientId        = Dhcp6GenerateClientId (Dhcp6Srv->Snp->Mode);

   if (Dhcp6Srv->ClientId == NULL) {
     FreePool (Dhcp6Srv);
     return EFI_DEVICE_ERROR;
   }

   //
   // Create an Udp6Io for stateful transmit/receive of each Dhcp6 instance.
   //
   Dhcp6Srv->UdpIo = UdpIoCreateIo (
                       Controller,
                       ImageHandle,
                       Dhcp6ConfigureUdpIo,
                       UDP_IO_UDP6_VERSION,
                       NULL
                       );

   if (Dhcp6Srv->UdpIo == NULL) {
     FreePool (Dhcp6Srv->ClientId);
     FreePool (Dhcp6Srv);
     return EFI_DEVICE_ERROR;
   }

   InitializeListHead (&Dhcp6Srv->Child);

   *Service = Dhcp6Srv;

   return EFI_SUCCESS;
 }


 /**
   Destroy the Dhcp6 instance and recycle the resources.

   @param[in, out]  Instance        The pointer to the Dhcp6 instance.

 **/
 VOID
 Dhcp6DestroyInstance (
   IN OUT DHCP6_INSTANCE         *Instance
   )
 {
   //
   // Clean up the retry list first.
   //
   Dhcp6CleanupRetry (Instance, DHCP6_PACKET_ALL);
   gBS->CloseEvent (Instance->Timer);

   //
   // Clean up the current configure data.
   //
   if (Instance->Config != NULL) {
     Dhcp6CleanupConfigData (Instance->Config);
     FreePool (Instance->Config);
   }

   //
   // Clean up the current Ia.
   //
   if (Instance->IaCb.Ia != NULL) {
     if (Instance->IaCb.Ia->ReplyPacket != NULL) {
       FreePool (Instance->IaCb.Ia->ReplyPacket);
     }
     FreePool (Instance->IaCb.Ia);
   }

   if (Instance->Unicast != NULL) {
     FreePool (Instance->Unicast);
   }

   if (Instance->AdSelect != NULL) {
     FreePool (Instance->AdSelect);
   }

   FreePool (Instance);
 }


 /**
   Create the Dhcp6 instance and initialize it.

   @param[in]  Service              The pointer to the Dhcp6 service.
   @param[out] Instance             The pointer to the Dhcp6 instance.

   @retval EFI_SUCCESS            The Dhcp6 instance is created.
   @retval EFI_OUT_OF_RESOURCES   Failed to allocate resources.

 **/
 EFI_STATUS
 Dhcp6CreateInstance (
   IN  DHCP6_SERVICE         *Service,
   OUT DHCP6_INSTANCE        **Instance
   )
 {
   EFI_STATUS                Status;
   DHCP6_INSTANCE            *Dhcp6Ins;

   *Instance = NULL;
   Dhcp6Ins  = AllocateZeroPool (sizeof (DHCP6_INSTANCE));

   if (Dhcp6Ins == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }

   //
   // Initialize the fields of the new Dhcp6 instance.
   //
   Dhcp6Ins->Signature       = DHCP6_INSTANCE_SIGNATURE;
   Dhcp6Ins->UdpSts          = EFI_ALREADY_STARTED;
   Dhcp6Ins->Service         = Service;
   Dhcp6Ins->InDestroy       = FALSE;
   Dhcp6Ins->MediaPresent    = TRUE;

   CopyMem (
     &Dhcp6Ins->Dhcp6,
     &gDhcp6ProtocolTemplate,
     sizeof (EFI_DHCP6_PROTOCOL)
     );

   InitializeListHead (&Dhcp6Ins->TxList);
   InitializeListHead (&Dhcp6Ins->InfList);

   //
   // There is a timer for each Dhcp6 instance, which is used to track the
   // lease time of Ia and the retransmisson time of all sent packets.
   //
   Status = gBS->CreateEvent (
                   EVT_NOTIFY_SIGNAL | EVT_TIMER,
                   TPL_CALLBACK,
                   Dhcp6OnTimerTick,
                   Dhcp6Ins,
                   &Dhcp6Ins->Timer
                   );

   if (EFI_ERROR (Status)) {
     FreePool (Dhcp6Ins);
     return Status;
   }

   *Instance = Dhcp6Ins;

   return EFI_SUCCESS;
 }

 /**
   Callback function which provided by user to remove one node in NetDestroyLinkList process.

   @param[in]    Entry           The entry to be removed.
   @param[in]    Context         Pointer to the callback context corresponds to the Context in NetDestroyLinkList.

   @retval EFI_SUCCESS           The entry has been removed successfully.
   @retval Others                Fail to remove the entry.

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6DestroyChildEntry (
   IN LIST_ENTRY         *Entry,
   IN VOID               *Context
   )
 {
   DHCP6_INSTANCE                   *Instance;
   EFI_SERVICE_BINDING_PROTOCOL     *ServiceBinding;

   if (Entry == NULL || Context == NULL) {
     return EFI_INVALID_PARAMETER;
   }

   Instance = NET_LIST_USER_STRUCT_S (Entry, DHCP6_INSTANCE, Link, DHCP6_INSTANCE_SIGNATURE);
   ServiceBinding = (EFI_SERVICE_BINDING_PROTOCOL *) Context;

   return ServiceBinding->DestroyChild (ServiceBinding, Instance->Handle);
 }


 /**
   Entry point of the DHCP6 driver to install various protocols.

   @param[in]  ImageHandle           The handle of the UEFI image file.
   @param[in]  SystemTable           The pointer to the EFI System Table.

   @retval EFI_SUCCESS           The operation completed successfully.
   @retval Others                Unexpected error occurs.

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6DriverEntryPoint (
   IN EFI_HANDLE                   ImageHandle,
   IN EFI_SYSTEM_TABLE             *SystemTable
   )
 {
   return EfiLibInstallDriverBindingComponentName2 (
            ImageHandle,
            SystemTable,
            &gDhcp6DriverBinding,
            ImageHandle,
            &gDhcp6ComponentName,
            &gDhcp6ComponentName2
            );
 }


 /**
   Test to see if this driver supports ControllerHandle. This service
   is called by the EFI boot service ConnectController(). In
   order to make drivers as small as possible, there are a few calling
   restrictions for this service. ConnectController() must
   follow these calling restrictions. If any other agent wishes to call
   Supported() it must also follow these calling restrictions.

   @param[in]  This                The pointer to the driver binding protocol.
   @param[in]  ControllerHandle    The handle of device to be tested.
   @param[in]  RemainingDevicePath Optional parameter use to pick a specific child
                                   device to be started.

   @retval EFI_SUCCESS         This driver supports this device.
   @retval Others              This driver does not support this device.

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6DriverBindingSupported (
   IN EFI_DRIVER_BINDING_PROTOCOL  *This,
   IN EFI_HANDLE                   ControllerHandle,
   IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath OPTIONAL
   )
 {
   return gBS->OpenProtocol (
                 ControllerHandle,
                 &gEfiUdp6ServiceBindingProtocolGuid,
                 NULL,
                 This->DriverBindingHandle,
                 ControllerHandle,
                 EFI_OPEN_PROTOCOL_TEST_PROTOCOL
                 );
 }


 /**
   Start this driver on ControllerHandle. This service is called by the
   EFI boot service ConnectController(). In order to make
   drivers as small as possible, there are a few calling restrictions for
   this service. ConnectController() must follow these
   calling restrictions. If any other agent wishes to call Start() it
   must also follow these calling restrictions.

   @param[in]  This                 The pointer to the driver binding protocol.
   @param[in]  ControllerHandle     The handle of device to be started.
   @param[in]  RemainingDevicePath  Optional parameter use to pick a specific child
                                    device to be started.

   @retval EFI_SUCCESS          This driver is installed to ControllerHandle.
   @retval EFI_ALREADY_STARTED  This driver is already running on ControllerHandle.
   @retval other                This driver does not support this device.

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6DriverBindingStart (
   IN EFI_DRIVER_BINDING_PROTOCOL  *This,
   IN EFI_HANDLE                   ControllerHandle,
   IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath OPTIONAL
   )
 {
   EFI_STATUS                      Status;
   DHCP6_SERVICE                   *Service;

   //
   // Check the Dhcp6 serivce whether already started.
   //
   Status = gBS->OpenProtocol (
                   ControllerHandle,
                   &gEfiDhcp6ServiceBindingProtocolGuid,
                   NULL,
                   This->DriverBindingHandle,
                   ControllerHandle,
                   EFI_OPEN_PROTOCOL_TEST_PROTOCOL
                   );

   if (!EFI_ERROR (Status)) {
     return EFI_ALREADY_STARTED;
   }

   //
   // Create and initialize the Dhcp6 service.
   //
   Status = Dhcp6CreateService (
              ControllerHandle,
              This->DriverBindingHandle,
              &Service
              );

   if (EFI_ERROR (Status)) {
     return Status;
   }

   ASSERT (Service != NULL);

   Status = gBS->InstallMultipleProtocolInterfaces (
                   &ControllerHandle,
                   &gEfiDhcp6ServiceBindingProtocolGuid,
                   &Service->ServiceBinding,
                   NULL
                   );

   if (EFI_ERROR (Status)) {
     Dhcp6DestroyService (Service);
     return Status;
   }

   return EFI_SUCCESS;
 }


 /**
   Stop this driver on ControllerHandle. This service is called by the
   EFI boot service DisconnectController(). In order to
   make drivers as small as possible, there are a few calling
   restrictions for this service. DisconnectController()
   must follow these calling restrictions. If any other agent wishes
   to call Stop() it must also follow these calling restrictions.

   @param[in]  This              Protocol instance pointer.
   @param[in]  ControllerHandle  Handle of device to stop driver on
   @param[in]  NumberOfChildren  Number of Handles in ChildHandleBuffer. If number of
                                 children is zero stop the entire bus driver.
   @param[in]  ChildHandleBuffer List of Child Handles to Stop.

   @retval EFI_SUCCESS           This driver is removed ControllerHandle
   @retval EFI_DEVICE_ERROR      An unexpected system or network error occurred.
   @retval other                 This driver was not removed from this device

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6DriverBindingStop (
   IN  EFI_DRIVER_BINDING_PROTOCOL  *This,
   IN  EFI_HANDLE                   ControllerHandle,
   IN  UINTN                        NumberOfChildren,
   IN  EFI_HANDLE                   *ChildHandleBuffer   OPTIONAL
   )
 {
   EFI_STATUS                       Status;
   EFI_HANDLE                       NicHandle;
   EFI_SERVICE_BINDING_PROTOCOL     *ServiceBinding;
   DHCP6_SERVICE                    *Service;
   LIST_ENTRY                       *List;
   UINTN                            ListLength;

   //
   // Find and check the Nic handle by the controller handle.
   //
   NicHandle = NetLibGetNicHandle (ControllerHandle, &gEfiUdp6ProtocolGuid);

   if (NicHandle == NULL) {
     return EFI_SUCCESS;
   }

   Status = gBS->OpenProtocol (
                   NicHandle,
                   &gEfiDhcp6ServiceBindingProtocolGuid,
                   (VOID **) &ServiceBinding,
                   This->DriverBindingHandle,
                   NicHandle,
                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
                   );

   if (EFI_ERROR (Status)) {
     return Status;
   }

   Service = DHCP6_SERVICE_FROM_THIS (ServiceBinding);
   if (!IsListEmpty (&Service->Child)) {
     //
     // Destroy all the children instances before destory the service.
     //
     List = &Service->Child;
     Status = NetDestroyLinkList (
                List,
                Dhcp6DestroyChildEntry,
                ServiceBinding,
                &ListLength
                );
     if (EFI_ERROR (Status) || ListLength != 0) {
       Status = EFI_DEVICE_ERROR;
     }
   }

   if (NumberOfChildren == 0 && !IsListEmpty (&Service->Child)) {
     Status = EFI_DEVICE_ERROR;
   }

   if (NumberOfChildren == 0 && IsListEmpty (&Service->Child)) {
     //
     // Destroy the service itself if no child instance left.
     //
     Status = gBS->UninstallProtocolInterface (
                     NicHandle,
                     &gEfiDhcp6ServiceBindingProtocolGuid,
                     ServiceBinding
                     );
     if (EFI_ERROR (Status)) {
       goto ON_EXIT;
     }

     Dhcp6DestroyService (Service);
     Status = EFI_SUCCESS;
   }

 ON_EXIT:
   return Status;
 }


 /**
   Creates a child handle and installs a protocol.

   The CreateChild() function installs a protocol on ChildHandle.
   If ChildHandle is a pointer to NULL, then a new handle is created and returned in ChildHandle.
   If ChildHandle is not a pointer to NULL, then the protocol installs on the existing ChildHandle.

   @param[in]      This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
   @param[in, out] ChildHandle Pointer to the handle of the child to create. If it is NULL,
                               then a new handle is created. If it is a pointer to an existing
                               UEFI handle, then the protocol is added to the existing UEFI handle.

   @retval EFI_SUCCES            The protocol was added to ChildHandle.
   @retval EFI_INVALID_PARAMETER ChildHandle is NULL.
   @retval other                 The child handle was not created.

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6ServiceBindingCreateChild (
   IN     EFI_SERVICE_BINDING_PROTOCOL  *This,
   IN OUT EFI_HANDLE                    *ChildHandle
   )
 {
   EFI_STATUS                       Status;
   EFI_TPL                          OldTpl;
   DHCP6_SERVICE                    *Service;
   DHCP6_INSTANCE                   *Instance;
   VOID                             *Udp6;

   if (This == NULL || ChildHandle == NULL) {
     return EFI_INVALID_PARAMETER;
   }

   Service = DHCP6_SERVICE_FROM_THIS (This);

   Status  = Dhcp6CreateInstance (Service, &Instance);

   if (EFI_ERROR (Status)) {
     return Status;
   }

   ASSERT (Instance != NULL);

   //
   // Start the timer when the instance is ready to use.
   //
   Status = gBS->SetTimer (
                   Instance->Timer,
                   TimerPeriodic,
                   TICKS_PER_SECOND
                   );

   if (EFI_ERROR (Status)) {
     goto ON_ERROR;
   }

   //
   // Install the DHCP6 protocol onto ChildHandle.
   //
   Status = gBS->InstallMultipleProtocolInterfaces (
                   ChildHandle,
                   &gEfiDhcp6ProtocolGuid,
                   &Instance->Dhcp6,
                   NULL
                   );

   if (EFI_ERROR (Status)) {
     goto ON_ERROR;
   }

   Instance->Handle = *ChildHandle;

   //
   // Open the UDP6 protocol BY_CHILD.
   //
   Status = gBS->OpenProtocol (
                   Service->UdpIo->UdpHandle,
                   &gEfiUdp6ProtocolGuid,
                   (VOID **) &Udp6,
                   gDhcp6DriverBinding.DriverBindingHandle,
                   Instance->Handle,
                   EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
                   );

   if (EFI_ERROR (Status)) {

     gBS->UninstallMultipleProtocolInterfaces (
            Instance->Handle,
            &gEfiDhcp6ProtocolGuid,
            &Instance->Dhcp6,
            NULL
            );
     goto ON_ERROR;
   }

   //
   // Add into the children list of its parent service.
   //
   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);

   InsertTailList (&Service->Child, &Instance->Link);
   Service->NumOfChild++;

   gBS->RestoreTPL (OldTpl);
   return EFI_SUCCESS;

 ON_ERROR:

   Dhcp6DestroyInstance (Instance);
   return Status;
 }


 /**
   Destroys a child handle with a protocol installed on it.

   The DestroyChild() function does the opposite of CreateChild(). It removes a protocol
   that was installed by CreateChild() from ChildHandle. If the removed protocol is the
   last protocol on ChildHandle, then ChildHandle is destroyed.

   @param[in]  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
   @param[in]  ChildHandle Handle of the child to destroy

   @retval EFI_SUCCES            The protocol was removed from ChildHandle.
   @retval EFI_UNSUPPORTED       ChildHandle does not support the protocol that is being removed.
   @retval EFI_INVALID_PARAMETER Child handle is NULL.
   @retval EFI_ACCESS_DENIED     The protocol could not be removed from the ChildHandle
                                 because its services are being used.
   @retval other                 The child handle was not destroyed

 **/
 EFI_STATUS
 EFIAPI
 Dhcp6ServiceBindingDestroyChild (
   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
   IN EFI_HANDLE                    ChildHandle
   )
 {
   EFI_STATUS                       Status;
   EFI_TPL                          OldTpl;
   EFI_DHCP6_PROTOCOL               *Dhcp6;
   DHCP6_SERVICE                    *Service;
   DHCP6_INSTANCE                   *Instance;

   if (This == NULL || ChildHandle == NULL) {
     return EFI_INVALID_PARAMETER;
   }

   //
   // Retrieve the private context data structures
   //
   Status = gBS->OpenProtocol (
                   ChildHandle,
                   &gEfiDhcp6ProtocolGuid,
                   (VOID **) &Dhcp6,
                   gDhcp6DriverBinding.DriverBindingHandle,
                   ChildHandle,
                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
                   );

   if (EFI_ERROR (Status)) {
     return EFI_UNSUPPORTED;
   }

   Instance = DHCP6_INSTANCE_FROM_THIS (Dhcp6);
   Service  = DHCP6_SERVICE_FROM_THIS (This);

   if (Instance->Service != Service) {
     return EFI_INVALID_PARAMETER;
   }

   if (Instance->InDestroy) {
     return EFI_SUCCESS;
   }

   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);

   Instance->InDestroy = TRUE;

   Status = gBS->CloseProtocol (
                   Service->UdpIo->UdpHandle,
                   &gEfiUdp6ProtocolGuid,
                   gDhcp6DriverBinding.DriverBindingHandle,
                   ChildHandle
                   );

   if (EFI_ERROR (Status)) {
     Instance->InDestroy = FALSE;
     gBS->RestoreTPL (OldTpl);
     return Status;
   }

   //
   // Uninstall the MTFTP6 protocol first to enable a top down destruction.
   //
   gBS->RestoreTPL (OldTpl);
   Status = gBS->UninstallProtocolInterface (
                   ChildHandle,
                   &gEfiDhcp6ProtocolGuid,
                   Dhcp6
                   );
   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
   if (EFI_ERROR (Status)) {
     Instance->InDestroy = FALSE;
     gBS->RestoreTPL (OldTpl);
     return Status;
   }

   //
   // Remove it from the children list of its parent service.
   //
   RemoveEntryList (&Instance->Link);
   Service->NumOfChild--;

   gBS->RestoreTPL (OldTpl);

   Dhcp6DestroyInstance (Instance);
   return EFI_SUCCESS;
 }
	/** @file
	Driver Binding functions and Service Binding functions
	implementationfor for Dhcp6 Driver.

	Copyright (c) 2009 - 2012, 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
	http://opensource.org/licenses/bsd-license.php.

	THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
	WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

	**/

	#include "Dhcp6Impl.h"


	EFI_DRIVER_BINDING_PROTOCOL gDhcp6DriverBinding = {
	Dhcp6DriverBindingSupported,
	Dhcp6DriverBindingStart,
	Dhcp6DriverBindingStop,
	0xa,
	NULL,
	NULL
	};

	EFI_SERVICE_BINDING_PROTOCOL gDhcp6ServiceBindingTemplate = {
	Dhcp6ServiceBindingCreateChild,
	Dhcp6ServiceBindingDestroyChild
	};

	/**
	Configure the default Udp6Io to receive all the DHCP6 traffic
	on this network interface.

	@param[in] UdpIo The pointer to Udp6Io to be configured.
	@param[in] Context The pointer to the context.

	@retval EFI_SUCCESS The Udp6Io is successfully configured.
	@retval Others Failed to configure the Udp6Io.

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6ConfigureUdpIo (
	IN UDP_IO *UdpIo,
	IN VOID *Context
	)
	{
	EFI_UDP6_PROTOCOL *Udp6;
	EFI_UDP6_CONFIG_DATA *Config;

	Udp6 = UdpIo->Protocol.Udp6;
	Config = &(UdpIo->Config.Udp6);

	ZeroMem (Config, sizeof (EFI_UDP6_CONFIG_DATA));

	//
	// Set Udp6 configure data for the Dhcp6 instance.
	//
	Config->AcceptPromiscuous = FALSE;
	Config->AcceptAnyPort = FALSE;
	Config->AllowDuplicatePort = FALSE;
	Config->TrafficClass = 0;
	Config->HopLimit = 128;
	Config->ReceiveTimeout = 0;
	Config->TransmitTimeout = 0;

	//
	// Configure an endpoint of client(0, 546), server(0, 0), the addresses
	// will be overridden later. Note that we MUST not limit RemotePort.
	// More details, refer to RFC 3315 section 5.2.
	//
	Config->StationPort = DHCP6_PORT_CLIENT;
	Config->RemotePort = 0;

	return Udp6->Configure (Udp6, Config);;
	}


	/**
	Destroy the Dhcp6 service. The Dhcp6 service may be partly initialized,
	or partly destroyed. If a resource is destroyed, it is marked as such in
	case the destroy failed and being called again later.

	@param[in, out] Service The pointer to Dhcp6 service to be destroyed.

	**/
	VOID
	Dhcp6DestroyService (
	IN OUT DHCP6_SERVICE *Service
	)
	{
	//
	// All children instances should have been already destroyed here.
	//
	ASSERT (Service->NumOfChild == 0);

	if (Service->ClientId != NULL) {
	FreePool (Service->ClientId);
	}

	if (Service->UdpIo != NULL) {
	UdpIoFreeIo (Service->UdpIo);
	}

	FreePool (Service);
	}


	/**
	Create a new Dhcp6 service for the Nic controller.

	@param[in] Controller The controller to be installed DHCP6 service
	binding protocol.
	@param[in] ImageHandle The image handle of the Dhcp6 driver.
	@param[out] Service The return pointer of the new Dhcp6 service.

	@retval EFI_SUCCESS The Dhcp6 service is created successfully.
	@retval EFI_DEVICE_ERROR An unexpected system or network error occurred.
	@retval EFI_OUT_OF_RESOURCES Failed to allocate resource.

	**/
	EFI_STATUS
	Dhcp6CreateService (
	IN EFI_HANDLE Controller,
	IN EFI_HANDLE ImageHandle,
	OUT DHCP6_SERVICE **Service
	)
	{
	DHCP6_SERVICE *Dhcp6Srv;
	EFI_STATUS Status;

	*Service = NULL;
	Dhcp6Srv = AllocateZeroPool (sizeof (DHCP6_SERVICE));

	if (Dhcp6Srv == NULL) {
	return EFI_OUT_OF_RESOURCES;
	}

	//
	// Open the SNP protocol to get mode data later.
	//
	Dhcp6Srv->Snp = NULL;
	NetLibGetSnpHandle (Controller, &Dhcp6Srv->Snp);
	if (Dhcp6Srv->Snp == NULL) {
	FreePool (Dhcp6Srv);
	return EFI_DEVICE_ERROR;
	}

	//
	// Initialize the fields of the new Dhcp6 service.
	//
	Dhcp6Srv->Signature = DHCP6_SERVICE_SIGNATURE;
	Dhcp6Srv->Controller = Controller;
	Dhcp6Srv->Image = ImageHandle;
	Dhcp6Srv->Xid = (0xffffff & NET_RANDOM (NetRandomInitSeed ()));

	CopyMem (
	&Dhcp6Srv->ServiceBinding,
	&gDhcp6ServiceBindingTemplate,
	sizeof (EFI_SERVICE_BINDING_PROTOCOL)
	);

	//
	// Locate Ip6->Ip6Config and store it for get IP6 Duplicate Address Detection transmits.
	//
	Status = gBS->HandleProtocol (
	Controller,
	&gEfiIp6ConfigProtocolGuid,
	(VOID **) &Dhcp6Srv->Ip6Cfg
	);
	if (EFI_ERROR (Status)) {
	FreePool (Dhcp6Srv);
	return Status;
	}

	//
	// Generate client Duid: If SMBIOS system UUID is located, generate DUID in DUID-UUID format.
	// Otherwise, in DUID-LLT format.
	//
	Dhcp6Srv->ClientId = Dhcp6GenerateClientId (Dhcp6Srv->Snp->Mode);

	if (Dhcp6Srv->ClientId == NULL) {
	FreePool (Dhcp6Srv);
	return EFI_DEVICE_ERROR;
	}

	//
	// Create an Udp6Io for stateful transmit/receive of each Dhcp6 instance.
	//
	Dhcp6Srv->UdpIo = UdpIoCreateIo (
	Controller,
	ImageHandle,
	Dhcp6ConfigureUdpIo,
	UDP_IO_UDP6_VERSION,
	NULL
	);

	if (Dhcp6Srv->UdpIo == NULL) {
	FreePool (Dhcp6Srv->ClientId);
	FreePool (Dhcp6Srv);
	return EFI_DEVICE_ERROR;
	}

	InitializeListHead (&Dhcp6Srv->Child);

	*Service = Dhcp6Srv;

	return EFI_SUCCESS;
	}


	/**
	Destroy the Dhcp6 instance and recycle the resources.

	@param[in, out] Instance The pointer to the Dhcp6 instance.

	**/
	VOID
	Dhcp6DestroyInstance (
	IN OUT DHCP6_INSTANCE *Instance
	)
	{
	//
	// Clean up the retry list first.
	//
	Dhcp6CleanupRetry (Instance, DHCP6_PACKET_ALL);
	gBS->CloseEvent (Instance->Timer);

	//
	// Clean up the current configure data.
	//
	if (Instance->Config != NULL) {
	Dhcp6CleanupConfigData (Instance->Config);
	FreePool (Instance->Config);
	}

	//
	// Clean up the current Ia.
	//
	if (Instance->IaCb.Ia != NULL) {
	if (Instance->IaCb.Ia->ReplyPacket != NULL) {
	FreePool (Instance->IaCb.Ia->ReplyPacket);
	}
	FreePool (Instance->IaCb.Ia);
	}

	if (Instance->Unicast != NULL) {
	FreePool (Instance->Unicast);
	}

	if (Instance->AdSelect != NULL) {
	FreePool (Instance->AdSelect);
	}

	FreePool (Instance);
	}


	/**
	Create the Dhcp6 instance and initialize it.

	@param[in] Service The pointer to the Dhcp6 service.
	@param[out] Instance The pointer to the Dhcp6 instance.

	@retval EFI_SUCCESS The Dhcp6 instance is created.
	@retval EFI_OUT_OF_RESOURCES Failed to allocate resources.

	**/
	EFI_STATUS
	Dhcp6CreateInstance (
	IN DHCP6_SERVICE *Service,
	OUT DHCP6_INSTANCE **Instance
	)
	{
	EFI_STATUS Status;
	DHCP6_INSTANCE *Dhcp6Ins;

	*Instance = NULL;
	Dhcp6Ins = AllocateZeroPool (sizeof (DHCP6_INSTANCE));

	if (Dhcp6Ins == NULL) {
	return EFI_OUT_OF_RESOURCES;
	}

	//
	// Initialize the fields of the new Dhcp6 instance.
	//
	Dhcp6Ins->Signature = DHCP6_INSTANCE_SIGNATURE;
	Dhcp6Ins->UdpSts = EFI_ALREADY_STARTED;
	Dhcp6Ins->Service = Service;
	Dhcp6Ins->InDestroy = FALSE;
	Dhcp6Ins->MediaPresent = TRUE;

	CopyMem (
	&Dhcp6Ins->Dhcp6,
	&gDhcp6ProtocolTemplate,
	sizeof (EFI_DHCP6_PROTOCOL)
	);

	InitializeListHead (&Dhcp6Ins->TxList);
	InitializeListHead (&Dhcp6Ins->InfList);

	//
	// There is a timer for each Dhcp6 instance, which is used to track the
	// lease time of Ia and the retransmisson time of all sent packets.
	//
	Status = gBS->CreateEvent (
	EVT_NOTIFY_SIGNAL \| EVT_TIMER,
	TPL_CALLBACK,
	Dhcp6OnTimerTick,
	Dhcp6Ins,
	&Dhcp6Ins->Timer
	);

	if (EFI_ERROR (Status)) {
	FreePool (Dhcp6Ins);
	return Status;
	}

	*Instance = Dhcp6Ins;

	return EFI_SUCCESS;
	}

	/**
	Callback function which provided by user to remove one node in NetDestroyLinkList process.

	@param[in] Entry The entry to be removed.
	@param[in] Context Pointer to the callback context corresponds to the Context in NetDestroyLinkList.

	@retval EFI_SUCCESS The entry has been removed successfully.
	@retval Others Fail to remove the entry.

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6DestroyChildEntry (
	IN LIST_ENTRY *Entry,
	IN VOID *Context
	)
	{
	DHCP6_INSTANCE *Instance;
	EFI_SERVICE_BINDING_PROTOCOL *ServiceBinding;

	if (Entry == NULL \|\| Context == NULL) {
	return EFI_INVALID_PARAMETER;
	}

	Instance = NET_LIST_USER_STRUCT_S (Entry, DHCP6_INSTANCE, Link, DHCP6_INSTANCE_SIGNATURE);
	ServiceBinding = (EFI_SERVICE_BINDING_PROTOCOL *) Context;

	return ServiceBinding->DestroyChild (ServiceBinding, Instance->Handle);
	}


	/**
	Entry point of the DHCP6 driver to install various protocols.

	@param[in] ImageHandle The handle of the UEFI image file.
	@param[in] SystemTable The pointer to the EFI System Table.

	@retval EFI_SUCCESS The operation completed successfully.
	@retval Others Unexpected error occurs.

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6DriverEntryPoint (
	IN EFI_HANDLE ImageHandle,
	IN EFI_SYSTEM_TABLE *SystemTable
	)
	{
	return EfiLibInstallDriverBindingComponentName2 (
	ImageHandle,
	SystemTable,
	&gDhcp6DriverBinding,
	ImageHandle,
	&gDhcp6ComponentName,
	&gDhcp6ComponentName2
	);
	}


	/**
	Test to see if this driver supports ControllerHandle. This service
	is called by the EFI boot service ConnectController(). In
	order to make drivers as small as possible, there are a few calling
	restrictions for this service. ConnectController() must
	follow these calling restrictions. If any other agent wishes to call
	Supported() it must also follow these calling restrictions.

	@param[in] This The pointer to the driver binding protocol.
	@param[in] ControllerHandle The handle of device to be tested.
	@param[in] RemainingDevicePath Optional parameter use to pick a specific child
	device to be started.

	@retval EFI_SUCCESS This driver supports this device.
	@retval Others This driver does not support this device.

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6DriverBindingSupported (
	IN EFI_DRIVER_BINDING_PROTOCOL *This,
	IN EFI_HANDLE ControllerHandle,
	IN EFI_DEVICE_PATH_PROTOCOL *RemainingDevicePath OPTIONAL
	)
	{
	return gBS->OpenProtocol (
	ControllerHandle,
	&gEfiUdp6ServiceBindingProtocolGuid,
	NULL,
	This->DriverBindingHandle,
	ControllerHandle,
	EFI_OPEN_PROTOCOL_TEST_PROTOCOL
	);
	}


	/**
	Start this driver on ControllerHandle. This service is called by the
	EFI boot service ConnectController(). In order to make
	drivers as small as possible, there are a few calling restrictions for
	this service. ConnectController() must follow these
	calling restrictions. If any other agent wishes to call Start() it
	must also follow these calling restrictions.

	@param[in] This The pointer to the driver binding protocol.
	@param[in] ControllerHandle The handle of device to be started.
	@param[in] RemainingDevicePath Optional parameter use to pick a specific child
	device to be started.

	@retval EFI_SUCCESS This driver is installed to ControllerHandle.
	@retval EFI_ALREADY_STARTED This driver is already running on ControllerHandle.
	@retval other This driver does not support this device.

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6DriverBindingStart (
	IN EFI_DRIVER_BINDING_PROTOCOL *This,
	IN EFI_HANDLE ControllerHandle,
	IN EFI_DEVICE_PATH_PROTOCOL *RemainingDevicePath OPTIONAL
	)
	{
	EFI_STATUS Status;
	DHCP6_SERVICE *Service;

	//
	// Check the Dhcp6 serivce whether already started.
	//
	Status = gBS->OpenProtocol (
	ControllerHandle,
	&gEfiDhcp6ServiceBindingProtocolGuid,
	NULL,
	This->DriverBindingHandle,
	ControllerHandle,
	EFI_OPEN_PROTOCOL_TEST_PROTOCOL
	);

	if (!EFI_ERROR (Status)) {
	return EFI_ALREADY_STARTED;
	}

	//
	// Create and initialize the Dhcp6 service.
	//
	Status = Dhcp6CreateService (
	ControllerHandle,
	This->DriverBindingHandle,
	&Service
	);

	if (EFI_ERROR (Status)) {
	return Status;
	}

	ASSERT (Service != NULL);

	Status = gBS->InstallMultipleProtocolInterfaces (
	&ControllerHandle,
	&gEfiDhcp6ServiceBindingProtocolGuid,
	&Service->ServiceBinding,
	NULL
	);

	if (EFI_ERROR (Status)) {
	Dhcp6DestroyService (Service);
	return Status;
	}

	return EFI_SUCCESS;
	}


	/**
	Stop this driver on ControllerHandle. This service is called by the
	EFI boot service DisconnectController(). In order to
	make drivers as small as possible, there are a few calling
	restrictions for this service. DisconnectController()
	must follow these calling restrictions. If any other agent wishes
	to call Stop() it must also follow these calling restrictions.

	@param[in] This Protocol instance pointer.
	@param[in] ControllerHandle Handle of device to stop driver on
	@param[in] NumberOfChildren Number of Handles in ChildHandleBuffer. If number of
	children is zero stop the entire bus driver.
	@param[in] ChildHandleBuffer List of Child Handles to Stop.

	@retval EFI_SUCCESS This driver is removed ControllerHandle
	@retval EFI_DEVICE_ERROR An unexpected system or network error occurred.
	@retval other This driver was not removed from this device

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6DriverBindingStop (
	IN EFI_DRIVER_BINDING_PROTOCOL *This,
	IN EFI_HANDLE ControllerHandle,
	IN UINTN NumberOfChildren,
	IN EFI_HANDLE *ChildHandleBuffer OPTIONAL
	)
	{
	EFI_STATUS Status;
	EFI_HANDLE NicHandle;
	EFI_SERVICE_BINDING_PROTOCOL *ServiceBinding;
	DHCP6_SERVICE *Service;
	LIST_ENTRY *List;
	UINTN ListLength;

	//
	// Find and check the Nic handle by the controller handle.
	//
	NicHandle = NetLibGetNicHandle (ControllerHandle, &gEfiUdp6ProtocolGuid);

	if (NicHandle == NULL) {
	return EFI_SUCCESS;
	}

	Status = gBS->OpenProtocol (
	NicHandle,
	&gEfiDhcp6ServiceBindingProtocolGuid,
	(VOID **) &ServiceBinding,
	This->DriverBindingHandle,
	NicHandle,
	EFI_OPEN_PROTOCOL_GET_PROTOCOL
	);

	if (EFI_ERROR (Status)) {
	return Status;
	}

	Service = DHCP6_SERVICE_FROM_THIS (ServiceBinding);
	if (!IsListEmpty (&Service->Child)) {
	//
	// Destroy all the children instances before destory the service.
	//
	List = &Service->Child;
	Status = NetDestroyLinkList (
	List,
	Dhcp6DestroyChildEntry,
	ServiceBinding,
	&ListLength
	);
	if (EFI_ERROR (Status) \|\| ListLength != 0) {
	Status = EFI_DEVICE_ERROR;
	}
	}

	if (NumberOfChildren == 0 && !IsListEmpty (&Service->Child)) {
	Status = EFI_DEVICE_ERROR;
	}

	if (NumberOfChildren == 0 && IsListEmpty (&Service->Child)) {
	//
	// Destroy the service itself if no child instance left.
	//
	Status = gBS->UninstallProtocolInterface (
	NicHandle,
	&gEfiDhcp6ServiceBindingProtocolGuid,
	ServiceBinding
	);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	Dhcp6DestroyService (Service);
	Status = EFI_SUCCESS;
	}

	ON_EXIT:
	return Status;
	}


	/**
	Creates a child handle and installs a protocol.

	The CreateChild() function installs a protocol on ChildHandle.
	If ChildHandle is a pointer to NULL, then a new handle is created and returned in ChildHandle.
	If ChildHandle is not a pointer to NULL, then the protocol installs on the existing ChildHandle.

	@param[in] This Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
	@param[in, out] ChildHandle Pointer to the handle of the child to create. If it is NULL,
	then a new handle is created. If it is a pointer to an existing
	UEFI handle, then the protocol is added to the existing UEFI handle.

	@retval EFI_SUCCES The protocol was added to ChildHandle.
	@retval EFI_INVALID_PARAMETER ChildHandle is NULL.
	@retval other The child handle was not created.

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6ServiceBindingCreateChild (
	IN EFI_SERVICE_BINDING_PROTOCOL *This,
	IN OUT EFI_HANDLE *ChildHandle
	)
	{
	EFI_STATUS Status;
	EFI_TPL OldTpl;
	DHCP6_SERVICE *Service;
	DHCP6_INSTANCE *Instance;
	VOID *Udp6;

	if (This == NULL \|\| ChildHandle == NULL) {
	return EFI_INVALID_PARAMETER;
	}

	Service = DHCP6_SERVICE_FROM_THIS (This);

	Status = Dhcp6CreateInstance (Service, &Instance);

	if (EFI_ERROR (Status)) {
	return Status;
	}

	ASSERT (Instance != NULL);

	//
	// Start the timer when the instance is ready to use.
	//
	Status = gBS->SetTimer (
	Instance->Timer,
	TimerPeriodic,
	TICKS_PER_SECOND
	);

	if (EFI_ERROR (Status)) {
	goto ON_ERROR;
	}

	//
	// Install the DHCP6 protocol onto ChildHandle.
	//
	Status = gBS->InstallMultipleProtocolInterfaces (
	ChildHandle,
	&gEfiDhcp6ProtocolGuid,
	&Instance->Dhcp6,
	NULL
	);

	if (EFI_ERROR (Status)) {
	goto ON_ERROR;
	}

	Instance->Handle = *ChildHandle;

	//
	// Open the UDP6 protocol BY_CHILD.
	//
	Status = gBS->OpenProtocol (
	Service->UdpIo->UdpHandle,
	&gEfiUdp6ProtocolGuid,
	(VOID **) &Udp6,
	gDhcp6DriverBinding.DriverBindingHandle,
	Instance->Handle,
	EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
	);

	if (EFI_ERROR (Status)) {

	gBS->UninstallMultipleProtocolInterfaces (
	Instance->Handle,
	&gEfiDhcp6ProtocolGuid,
	&Instance->Dhcp6,
	NULL
	);
	goto ON_ERROR;
	}

	//
	// Add into the children list of its parent service.
	//
	OldTpl = gBS->RaiseTPL (TPL_CALLBACK);

	InsertTailList (&Service->Child, &Instance->Link);
	Service->NumOfChild++;

	gBS->RestoreTPL (OldTpl);
	return EFI_SUCCESS;

	ON_ERROR:

	Dhcp6DestroyInstance (Instance);
	return Status;
	}


	/**
	Destroys a child handle with a protocol installed on it.

	The DestroyChild() function does the opposite of CreateChild(). It removes a protocol
	that was installed by CreateChild() from ChildHandle. If the removed protocol is the
	last protocol on ChildHandle, then ChildHandle is destroyed.

	@param[in] This Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
	@param[in] ChildHandle Handle of the child to destroy

	@retval EFI_SUCCES The protocol was removed from ChildHandle.
	@retval EFI_UNSUPPORTED ChildHandle does not support the protocol that is being removed.
	@retval EFI_INVALID_PARAMETER Child handle is NULL.
	@retval EFI_ACCESS_DENIED The protocol could not be removed from the ChildHandle
	because its services are being used.
	@retval other The child handle was not destroyed

	**/
	EFI_STATUS
	EFIAPI
	Dhcp6ServiceBindingDestroyChild (
	IN EFI_SERVICE_BINDING_PROTOCOL *This,
	IN EFI_HANDLE ChildHandle
	)
	{
	EFI_STATUS Status;
	EFI_TPL OldTpl;
	EFI_DHCP6_PROTOCOL *Dhcp6;
	DHCP6_SERVICE *Service;
	DHCP6_INSTANCE *Instance;

	if (This == NULL \|\| ChildHandle == NULL) {
	return EFI_INVALID_PARAMETER;
	}

	//
	// Retrieve the private context data structures
	//
	Status = gBS->OpenProtocol (
	ChildHandle,
	&gEfiDhcp6ProtocolGuid,
	(VOID **) &Dhcp6,
	gDhcp6DriverBinding.DriverBindingHandle,
	ChildHandle,
	EFI_OPEN_PROTOCOL_GET_PROTOCOL
	);

	if (EFI_ERROR (Status)) {
	return EFI_UNSUPPORTED;
	}

	Instance = DHCP6_INSTANCE_FROM_THIS (Dhcp6);
	Service = DHCP6_SERVICE_FROM_THIS (This);

	if (Instance->Service != Service) {
	return EFI_INVALID_PARAMETER;
	}

	if (Instance->InDestroy) {
	return EFI_SUCCESS;
	}

	OldTpl = gBS->RaiseTPL (TPL_CALLBACK);

	Instance->InDestroy = TRUE;

	Status = gBS->CloseProtocol (
	Service->UdpIo->UdpHandle,
	&gEfiUdp6ProtocolGuid,
	gDhcp6DriverBinding.DriverBindingHandle,
	ChildHandle
	);

	if (EFI_ERROR (Status)) {
	Instance->InDestroy = FALSE;
	gBS->RestoreTPL (OldTpl);
	return Status;
	}

	//
	// Uninstall the MTFTP6 protocol first to enable a top down destruction.
	//
	gBS->RestoreTPL (OldTpl);
	Status = gBS->UninstallProtocolInterface (
	ChildHandle,
	&gEfiDhcp6ProtocolGuid,
	Dhcp6
	);
	OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
	if (EFI_ERROR (Status)) {
	Instance->InDestroy = FALSE;
	gBS->RestoreTPL (OldTpl);
	return Status;
	}

	//
	// Remove it from the children list of its parent service.
	//
	RemoveEntryList (&Instance->Link);
	Service->NumOfChild--;

	gBS->RestoreTPL (OldTpl);

	Dhcp6DestroyInstance (Instance);
	return EFI_SUCCESS;
	}