MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Driver.c

   1 /** @file
   2
   3 Copyright (c) 2006 - 2008, Intel Corporation.<BR>
   4 All rights reserved. This program and the accompanying materials
   5 are licensed and made available under the terms and conditions of the BSD License
   6 which accompanies this distribution.  The full text of the license may be found at
   7 http://opensource.org/licenses/bsd-license.php
   8
   9 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11
  12 **/
  13
  14 #include "Dhcp4Impl.h"
  15 #include "Dhcp4Driver.h"
  16
  17 EFI_DRIVER_BINDING_PROTOCOL gDhcp4DriverBinding = {
  18   Dhcp4DriverBindingSupported,
  19   Dhcp4DriverBindingStart,
  20   Dhcp4DriverBindingStop,
  21   0xa,
  22   NULL,
  23   NULL
  24 };
  25
  26 EFI_SERVICE_BINDING_PROTOCOL mDhcp4ServiceBindingTemplate = {
  27   Dhcp4ServiceBindingCreateChild,
  28   Dhcp4ServiceBindingDestroyChild
  29 };
  30
  31 /**
  32   This is the declaration of an EFI image entry point. This entry point is
  33   the same for UEFI Applications, UEFI OS Loaders, and UEFI Drivers including
  34   both device drivers and bus drivers.
  35
  36   Entry point of the DHCP driver to install various protocols.
  37
  38   @param[in]  ImageHandle           The firmware allocated handle for the UEFI image.
  39   @param[in]  SystemTable           A pointer to the EFI System Table.
  40
  41   @retval EFI_SUCCESS           The operation completed successfully.
  42   @retval EFI_OUT_OF_RESOURCES  The request could not be completed due to a lack of resources.
  43
  44 **/
  45 EFI_STATUS
  46 EFIAPI
  47 Dhcp4DriverEntryPoint (
  48   IN EFI_HANDLE             ImageHandle,
  49   IN EFI_SYSTEM_TABLE       *SystemTable
  50   )
  51 {
  52   return EfiLibInstallDriverBindingComponentName2 (
  53            ImageHandle,
  54            SystemTable,
  55            &gDhcp4DriverBinding,
  56            ImageHandle,
  57            &gDhcp4ComponentName,
  58            &gDhcp4ComponentName2
  59            );
  60 }
  61
  62
  63 /**
  64   Test to see if this driver supports ControllerHandle. This service
  65   is called by the EFI boot service ConnectController(). In
  66   order to make drivers as small as possible, there are a few calling
  67   restrictions for this service. ConnectController() must
  68   follow these calling restrictions. If any other agent wishes to call
  69   Supported() it must also follow these calling restrictions.
  70
  71   @param[in]  This                Protocol instance pointer.
  72   @param[in]  ControllerHandle    Handle of device to test
  73   @param[in]  RemainingDevicePath Optional parameter use to pick a specific child
  74                                   device to start.
  75
  76   @retval EFI_SUCCESS         This driver supports this device
  77   @retval EFI_ALREADY_STARTED This driver is already running on this device
  78   @retval other               This driver does not support this device
  79
  80 **/
  81 EFI_STATUS
  82 EFIAPI
  83 Dhcp4DriverBindingSupported (
  84   IN EFI_DRIVER_BINDING_PROTOCOL  *This,
  85   IN EFI_HANDLE                   ControllerHandle,
  86   IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath OPTIONAL
  87   )
  88 {
  89   EFI_STATUS  Status;
  90
  91   Status = gBS->OpenProtocol (
  92                   ControllerHandle,
  93                   &gEfiUdp4ServiceBindingProtocolGuid,
  94                   NULL,
  95                   This->DriverBindingHandle,
  96                   ControllerHandle,
  97                   EFI_OPEN_PROTOCOL_TEST_PROTOCOL
  98                   );
  99
 100   return Status;
 101 }
 102
 103
 104
 105 /**
 106   Configure the default UDP child to receive all the DHCP traffics
 107   on this network interface.
 108
 109   @param[in]  UdpIo                  The UDP IO port to configure
 110   @param[in]  Context                The context to the function
 111
 112   @retval EFI_SUCCESS            The UDP IO port is successfully configured.
 113   @retval Others                 Failed to configure the UDP child.
 114
 115 **/
 116 EFI_STATUS
 117 DhcpConfigUdpIo (
 118   IN UDP_IO_PORT            *UdpIo,
 119   IN VOID                   *Context
 120   )
 121 {
 122   EFI_UDP4_CONFIG_DATA      UdpConfigData;
 123
 124   UdpConfigData.AcceptBroadcast           = TRUE;
 125   UdpConfigData.AcceptPromiscuous         = FALSE;
 126   UdpConfigData.AcceptAnyPort             = FALSE;
 127   UdpConfigData.AllowDuplicatePort        = TRUE;
 128   UdpConfigData.TypeOfService             = 0;
 129   UdpConfigData.TimeToLive                = 64;
 130   UdpConfigData.DoNotFragment             = FALSE;
 131   UdpConfigData.ReceiveTimeout            = 0;
 132   UdpConfigData.TransmitTimeout           = 0;
 133
 134   UdpConfigData.UseDefaultAddress         = FALSE;
 135   UdpConfigData.StationPort               = DHCP_CLIENT_PORT;
 136   UdpConfigData.RemotePort                = DHCP_SERVER_PORT;
 137
 138   ZeroMem (&UdpConfigData.StationAddress, sizeof (EFI_IPv4_ADDRESS));
 139   ZeroMem (&UdpConfigData.SubnetMask, sizeof (EFI_IPv4_ADDRESS));
 140   ZeroMem (&UdpConfigData.RemoteAddress, sizeof (EFI_IPv4_ADDRESS));
 141
 142   return UdpIo->Udp->Configure (UdpIo->Udp, &UdpConfigData);;
 143 }
 144
 145
 146
 147 /**
 148   Destory the DHCP service. The Dhcp4 service may be partly initialized,
 149   or partly destroyed. If a resource is destroyed, it is marked as so in
 150   case the destroy failed and being called again later.
 151
 152   @param[in]  DhcpSb                 The DHCP service instance to destory.
 153
 154   @retval EFI_SUCCESS            Always return success.
 155
 156 **/
 157 EFI_STATUS
 158 Dhcp4CloseService (
 159   IN DHCP_SERVICE           *DhcpSb
 160   )
 161 {
 162   DhcpCleanLease (DhcpSb);
 163
 164   if (DhcpSb->UdpIo != NULL) {
 165     UdpIoFreePort (DhcpSb->UdpIo);
 166     DhcpSb->UdpIo = NULL;
 167   }
 168
 169   if (DhcpSb->Timer != NULL) {
 170     gBS->SetTimer (DhcpSb->Timer, TimerCancel, 0);
 171     gBS->CloseEvent (DhcpSb->Timer);
 172
 173     DhcpSb->Timer = NULL;
 174   }
 175
 176   return EFI_SUCCESS;
 177 }
 178
 179
 180
 181 /**
 182   Create a new DHCP service binding instance for the controller.
 183
 184   @param[in]  Controller             The controller to install DHCP service binding
 185                                      protocol onto
 186   @param[in]  ImageHandle            The driver's image handle
 187   @param[out] Service                The variable to receive the created DHCP service
 188                                      instance.
 189
 190   @retval EFI_OUT_OF_RESOURCES   Failed to allocate resource .
 191   @retval EFI_SUCCESS            The DHCP service instance is created.
 192   @retval other                  Other error occurs.
 193
 194 **/
 195 EFI_STATUS
 196 Dhcp4CreateService (
 197   IN  EFI_HANDLE            Controller,
 198   IN  EFI_HANDLE            ImageHandle,
 199   OUT DHCP_SERVICE          **Service
 200   )
 201 {
 202   DHCP_SERVICE              *DhcpSb;
 203   EFI_STATUS                Status;
 204
 205   *Service  = NULL;
 206   DhcpSb    = AllocateZeroPool (sizeof (DHCP_SERVICE));
 207
 208   if (DhcpSb == NULL) {
 209     return EFI_OUT_OF_RESOURCES;
 210   }
 211
 212   DhcpSb->Signature       = DHCP_SERVICE_SIGNATURE;
 213   DhcpSb->ServiceState    = DHCP_UNCONFIGED;
 214   DhcpSb->InDestory       = FALSE;
 215   DhcpSb->Controller      = Controller;
 216   DhcpSb->Image           = ImageHandle;
 217   InitializeListHead (&DhcpSb->Children);
 218   DhcpSb->DhcpState       = Dhcp4Stopped;
 219   DhcpSb->Xid             = NET_RANDOM (NetRandomInitSeed ());
 220   CopyMem (
 221     &DhcpSb->ServiceBinding,
 222     &mDhcp4ServiceBindingTemplate,
 223     sizeof (EFI_SERVICE_BINDING_PROTOCOL)
 224     );
 225   //
 226   // Create various resources, UdpIo, Timer, and get Mac address
 227   //
 228   Status = gBS->CreateEvent (
 229                   EVT_NOTIFY_SIGNAL | EVT_TIMER,
 230                   TPL_CALLBACK,
 231                   DhcpOnTimerTick,
 232                   DhcpSb,
 233                   &DhcpSb->Timer
 234                   );
 235
 236   if (EFI_ERROR (Status)) {
 237     goto ON_ERROR;
 238   }
 239
 240   DhcpSb->UdpIo = UdpIoCreatePort (Controller, ImageHandle, DhcpConfigUdpIo, NULL);
 241
 242   if (DhcpSb->UdpIo == NULL) {
 243     Status = EFI_OUT_OF_RESOURCES;
 244     goto ON_ERROR;
 245   }
 246
 247   DhcpSb->HwLen  = (UINT8) DhcpSb->UdpIo->SnpMode.HwAddressSize;
 248   DhcpSb->HwType = DhcpSb->UdpIo->SnpMode.IfType;
 249   CopyMem (&DhcpSb->Mac, &DhcpSb->UdpIo->SnpMode.CurrentAddress, sizeof (DhcpSb->Mac));
 250
 251   *Service       = DhcpSb;
 252   return EFI_SUCCESS;
 253
 254 ON_ERROR:
 255   Dhcp4CloseService (DhcpSb);
 256   FreePool (DhcpSb);
 257
 258   return Status;
 259 }
 260
 261
 262 /**
 263   Start this driver on ControllerHandle. This service is called by the
 264   EFI boot service ConnectController(). In order to make
 265   drivers as small as possible, there are a few calling restrictions for
 266   this service. ConnectController() must follow these
 267   calling restrictions. If any other agent wishes to call Start() it
 268   must also follow these calling restrictions.
 269
 270   @param[in]  This                 Protocol instance pointer.
 271   @param[in]  ControllerHandle     Handle of device to bind driver to
 272   @param[in]  RemainingDevicePath  Optional parameter use to pick a specific child
 273                                    device to start.
 274
 275   @retval EFI_SUCCESS          This driver is added to ControllerHandle
 276   @retval EFI_ALREADY_STARTED  This driver is already running on ControllerHandle
 277   @retval other                This driver does not support this device
 278
 279 **/
 280 EFI_STATUS
 281 EFIAPI
 282 Dhcp4DriverBindingStart (
 283   IN EFI_DRIVER_BINDING_PROTOCOL  *This,
 284   IN EFI_HANDLE                   ControllerHandle,
 285   IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath OPTIONAL
 286   )
 287 {
 288   DHCP_SERVICE              *DhcpSb;
 289   EFI_STATUS                Status;
 290
 291   //
 292   // First: test for the DHCP4 Protocol
 293   //
 294   Status = gBS->OpenProtocol (
 295                   ControllerHandle,
 296                   &gEfiDhcp4ServiceBindingProtocolGuid,
 297                   NULL,
 298                   This->DriverBindingHandle,
 299                   ControllerHandle,
 300                   EFI_OPEN_PROTOCOL_TEST_PROTOCOL
 301                   );
 302
 303   if (Status == EFI_SUCCESS) {
 304     return EFI_ALREADY_STARTED;
 305   }
 306
 307   Status = Dhcp4CreateService (ControllerHandle, This->DriverBindingHandle, &DhcpSb);
 308
 309   if (EFI_ERROR (Status)) {
 310     return Status;
 311   }
 312
 313   Status = gBS->SetTimer (DhcpSb->Timer, TimerPeriodic, TICKS_PER_SECOND);
 314
 315   if (EFI_ERROR (Status)) {
 316     goto ON_ERROR;
 317   }
 318
 319   //
 320   // Install the Dhcp4ServiceBinding Protocol onto ControlerHandle
 321   //
 322   Status = gBS->InstallMultipleProtocolInterfaces (
 323                   &ControllerHandle,
 324                   &gEfiDhcp4ServiceBindingProtocolGuid,
 325                   &DhcpSb->ServiceBinding,
 326                   NULL
 327                   );
 328
 329   if (EFI_ERROR (Status)) {
 330     goto ON_ERROR;
 331   }
 332
 333   return Status;
 334
 335 ON_ERROR:
 336   Dhcp4CloseService (DhcpSb);
 337   FreePool (DhcpSb);
 338   return Status;
 339 }
 340
 341
 342 /**
 343   Stop this driver on ControllerHandle. This service is called by the
 344   EFI boot service DisconnectController(). In order to
 345   make drivers as small as possible, there are a few calling
 346   restrictions for this service. DisconnectController()
 347   must follow these calling restrictions. If any other agent wishes
 348   to call Stop() it must also follow these calling restrictions.
 349
 350   @param[in]  This              Protocol instance pointer.
 351   @param[in]  ControllerHandle  Handle of device to stop driver on
 352   @param[in]  NumberOfChildren  Number of Handles in ChildHandleBuffer. If number of
 353                                 children is zero stop the entire bus driver.
 354   @param[in]  ChildHandleBuffer List of Child Handles to Stop.
 355
 356   @retval EFI_SUCCESS       This driver is removed ControllerHandle
 357   @retval other             This driver was not removed from this device
 358
 359 **/
 360 EFI_STATUS
 361 EFIAPI
 362 Dhcp4DriverBindingStop (
 363   IN  EFI_DRIVER_BINDING_PROTOCOL  *This,
 364   IN  EFI_HANDLE                   ControllerHandle,
 365   IN  UINTN                        NumberOfChildren,
 366   IN  EFI_HANDLE                   *ChildHandleBuffer
 367   )
 368 {
 369   EFI_SERVICE_BINDING_PROTOCOL  *ServiceBinding;
 370   DHCP_SERVICE                  *DhcpSb;
 371   DHCP_PROTOCOL                 *Instance;
 372   EFI_HANDLE                    NicHandle;
 373   EFI_STATUS                    Status;
 374   EFI_TPL                       OldTpl;
 375
 376   //
 377   // DHCP driver opens UDP child, So, the ControllerHandle is the
 378   // UDP child handle. locate the Nic handle first.
 379   //
 380   NicHandle = NetLibGetNicHandle (ControllerHandle, &gEfiUdp4ProtocolGuid);
 381
 382   if (NicHandle == NULL) {
 383     return EFI_DEVICE_ERROR;
 384   }
 385
 386    Status = gBS->OpenProtocol (
 387                   NicHandle,
 388                   &gEfiDhcp4ServiceBindingProtocolGuid,
 389                   (VOID **) &ServiceBinding,
 390                   This->DriverBindingHandle,
 391                   NicHandle,
 392                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
 393                   );
 394
 395   if (EFI_ERROR (Status)) {
 396     return EFI_DEVICE_ERROR;
 397   }
 398
 399   DhcpSb = DHCP_SERVICE_FROM_THIS (ServiceBinding);
 400
 401   if (DhcpSb->InDestory) {
 402     return EFI_SUCCESS;
 403   }
 404
 405   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 406
 407   if (NumberOfChildren == 0) {
 408
 409     DhcpSb->InDestory    = TRUE;
 410     DhcpSb->ServiceState = DHCP_DESTORY;
 411
 412     gBS->UninstallProtocolInterface (
 413            NicHandle,
 414            &gEfiDhcp4ServiceBindingProtocolGuid,
 415            ServiceBinding
 416            );
 417
 418     Dhcp4CloseService (DhcpSb);
 419
 420     FreePool (DhcpSb);
 421   } else {
 422     //
 423     // Don't use NET_LIST_FOR_EACH_SAFE here, Dhcp4ServiceBindingDestoryChild
 424     // may cause other child to be deleted.
 425     //
 426     while (!IsListEmpty (&DhcpSb->Children)) {
 427       Instance = NET_LIST_HEAD (&DhcpSb->Children, DHCP_PROTOCOL, Link);
 428       ServiceBinding->DestroyChild (ServiceBinding, Instance->Handle);
 429     }
 430
 431     if (DhcpSb->NumChildren != 0) {
 432       Status = EFI_DEVICE_ERROR;
 433     }
 434   }
 435
 436   gBS->RestoreTPL (OldTpl);
 437
 438   return Status;
 439 }
 440
 441
 442 /**
 443   Initialize a new DHCP instance.
 444
 445   @param  DhcpSb                 The dhcp service instance
 446   @param  Instance               The dhcp instance to initialize
 447
 448 **/
 449 VOID
 450 DhcpInitProtocol (
 451   IN     DHCP_SERVICE           *DhcpSb,
 452   IN OUT DHCP_PROTOCOL          *Instance
 453   )
 454 {
 455   Instance->Signature         = DHCP_PROTOCOL_SIGNATURE;
 456   CopyMem (&Instance->Dhcp4Protocol, &mDhcp4ProtocolTemplate, sizeof (Instance->Dhcp4Protocol));
 457   InitializeListHead (&Instance->Link);
 458   Instance->Handle            = NULL;
 459   Instance->Service           = DhcpSb;
 460   Instance->InDestory         = FALSE;
 461   Instance->CompletionEvent   = NULL;
 462   Instance->RenewRebindEvent  = NULL;
 463   Instance->Token             = NULL;
 464   Instance->UdpIo             = NULL;
 465   NetbufQueInit (&Instance->ResponseQueue);
 466 }
 467
 468
 469 /**
 470   Creates a child handle and installs a protocol.
 471
 472   The CreateChild() function installs a protocol on ChildHandle.
 473   If ChildHandle is a pointer to NULL, then a new handle is created and returned in ChildHandle.
 474   If ChildHandle is not a pointer to NULL, then the protocol installs on the existing ChildHandle.
 475
 476   @param  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
 477   @param  ChildHandle Pointer to the handle of the child to create. If it is NULL,
 478                       then a new handle is created. If it is a pointer to an existing UEFI handle,
 479                       then the protocol is added to the existing UEFI handle.
 480
 481   @retval EFI_SUCCES            The protocol was added to ChildHandle.
 482   @retval EFI_INVALID_PARAMETER ChildHandle is NULL.
 483   @retval EFI_OUT_OF_RESOURCES  There are not enough resources availabe to create
 484                                 the child
 485   @retval other                 The child handle was not created
 486
 487 **/
 488 EFI_STATUS
 489 EFIAPI
 490 Dhcp4ServiceBindingCreateChild (
 491   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
 492   IN EFI_HANDLE                    *ChildHandle
 493   )
 494 {
 495   DHCP_SERVICE              *DhcpSb;
 496   DHCP_PROTOCOL             *Instance;
 497   EFI_STATUS                Status;
 498   EFI_TPL                   OldTpl;
 499   VOID                      *Udp4;
 500
 501   if ((This == NULL) || (ChildHandle == NULL)) {
 502     return EFI_INVALID_PARAMETER;
 503   }
 504
 505   Instance = AllocatePool (sizeof (*Instance));
 506
 507   if (Instance == NULL) {
 508     return EFI_OUT_OF_RESOURCES;
 509   }
 510
 511   DhcpSb = DHCP_SERVICE_FROM_THIS (This);
 512   DhcpInitProtocol (DhcpSb, Instance);
 513
 514   //
 515   // Install DHCP4 onto ChildHandle
 516   //
 517   Status = gBS->InstallMultipleProtocolInterfaces (
 518                   ChildHandle,
 519                   &gEfiDhcp4ProtocolGuid,
 520                   &Instance->Dhcp4Protocol,
 521                   NULL
 522                   );
 523
 524   if (EFI_ERROR (Status)) {
 525     FreePool (Instance);
 526     return Status;
 527   }
 528
 529   Instance->Handle  = *ChildHandle;
 530
 531   //
 532   // Open the Udp4 protocol BY_CHILD.
 533   //
 534   Status = gBS->OpenProtocol (
 535                   DhcpSb->UdpIo->UdpHandle,
 536                   &gEfiUdp4ProtocolGuid,
 537                   (VOID **) &Udp4,
 538                   gDhcp4DriverBinding.DriverBindingHandle,
 539                   Instance->Handle,
 540                   EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
 541                   );
 542   if (EFI_ERROR (Status)) {
 543     gBS->UninstallMultipleProtocolInterfaces (
 544            Instance->Handle,
 545            &gEfiDhcp4ProtocolGuid,
 546            &Instance->Dhcp4Protocol,
 547            NULL
 548            );
 549
 550     FreePool (Instance);
 551     return Status;
 552   }
 553
 554   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 555
 556   InsertTailList (&DhcpSb->Children, &Instance->Link);
 557   DhcpSb->NumChildren++;
 558
 559   gBS->RestoreTPL (OldTpl);
 560
 561   return EFI_SUCCESS;
 562 }
 563
 564
 565 /**
 566   Destroys a child handle with a protocol installed on it.
 567
 568   The DestroyChild() function does the opposite of CreateChild(). It removes a protocol
 569   that was installed by CreateChild() from ChildHandle. If the removed protocol is the
 570   last protocol on ChildHandle, then ChildHandle is destroyed.
 571
 572   @param  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
 573   @param  ChildHandle Handle of the child to destroy
 574
 575   @retval EFI_SUCCES            The protocol was removed from ChildHandle.
 576   @retval EFI_UNSUPPORTED       ChildHandle does not support the protocol that is being removed.
 577   @retval EFI_INVALID_PARAMETER Child handle is not a valid UEFI Handle.
 578   @retval EFI_ACCESS_DENIED     The protocol could not be removed from the ChildHandle
 579                                 because its services are being used.
 580   @retval other                 The child handle was not destroyed
 581
 582 **/
 583 EFI_STATUS
 584 EFIAPI
 585 Dhcp4ServiceBindingDestroyChild (
 586   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
 587   IN EFI_HANDLE                    ChildHandle
 588   )
 589 {
 590   DHCP_SERVICE              *DhcpSb;
 591   DHCP_PROTOCOL             *Instance;
 592   EFI_DHCP4_PROTOCOL        *Dhcp;
 593   EFI_TPL                   OldTpl;
 594   EFI_STATUS                Status;
 595
 596   if ((This == NULL) || (ChildHandle == NULL)) {
 597     return EFI_INVALID_PARAMETER;
 598   }
 599
 600   //
 601   // Retrieve the private context data structures
 602   //
 603   Status = gBS->OpenProtocol (
 604                   ChildHandle,
 605                   &gEfiDhcp4ProtocolGuid,
 606                   (VOID **) &Dhcp,
 607                   gDhcp4DriverBinding.DriverBindingHandle,
 608                   ChildHandle,
 609                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
 610                   );
 611
 612   if (EFI_ERROR (Status)) {
 613     return EFI_UNSUPPORTED;
 614   }
 615
 616   Instance  = DHCP_INSTANCE_FROM_THIS (Dhcp);
 617   DhcpSb    = DHCP_SERVICE_FROM_THIS (This);
 618
 619   if (Instance->Service != DhcpSb) {
 620     return EFI_INVALID_PARAMETER;
 621   }
 622
 623   //
 624   // A child can be destroyed more than once. For example,
 625   // Dhcp4DriverBindingStop will destroy all of its children.
 626   // when caller driver is being stopped, it will destory the
 627   // dhcp child it opens.
 628   //
 629   if (Instance->InDestory) {
 630     return EFI_SUCCESS;
 631   }
 632
 633   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 634   Instance->InDestory = TRUE;
 635
 636   //
 637   // Close the Udp4 protocol.
 638   //
 639   gBS->CloseProtocol (
 640          DhcpSb->UdpIo->UdpHandle,
 641          &gEfiUdp4ProtocolGuid,
 642          gDhcp4DriverBinding.DriverBindingHandle,
 643          ChildHandle
 644          );
 645
 646   //
 647   // Uninstall the DHCP4 protocol first to enable a top down destruction.
 648   //
 649   Status = gBS->UninstallProtocolInterface (
 650                   ChildHandle,
 651                   &gEfiDhcp4ProtocolGuid,
 652                   Dhcp
 653                   );
 654
 655   if (EFI_ERROR (Status)) {
 656     Instance->InDestory = FALSE;
 657
 658     gBS->RestoreTPL (OldTpl);
 659     return Status;
 660   }
 661
 662   if (DhcpSb->ActiveChild == Instance) {
 663     DhcpYieldControl (DhcpSb);
 664   }
 665
 666   RemoveEntryList (&Instance->Link);
 667   DhcpSb->NumChildren--;
 668
 669   gBS->RestoreTPL (OldTpl);
 670
 671   FreePool (Instance);
 672   return EFI_SUCCESS;
 673 }