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

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

   Copyright (c) 2009 - 2018, Intel Corporation. All rights reserved.<BR>
   Copyright (c) Microsoft Corporation
   SPDX-License-Identifier: BSD-2-Clause-Patent

 **/

 #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;
   UINT32         Random;

   Status = PseudoRandomU32 (&Random);
   if (EFI_ERROR (Status)) {
     DEBUG ((DEBUG_ERROR, "%a failed to generate random number: %r\n", __func__, Status));
     return 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 & Random);

   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 retransmission 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 service 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 destroy 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_SUCCESS           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_SUCCESS           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
	implementation for Dhcp6 Driver.

	Copyright (c) 2009 - 2018, Intel Corporation. All rights reserved.<BR>
	Copyright (c) Microsoft Corporation
	SPDX-License-Identifier: BSD-2-Clause-Patent

	**/

	#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;
	UINT32 Random;

	Status = PseudoRandomU32 (&Random);
	if (EFI_ERROR (Status)) {
	DEBUG ((DEBUG_ERROR, "%a failed to generate random number: %r\n", __func__, Status));
	return 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 & Random);

	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 retransmission 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 service 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 destroy 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_SUCCESS 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_SUCCESS 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;
	}