MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Driver.c

   1 /** @file
   2
   3 Copyright (c) 2006 - 2010, 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 to configure
 110   @param[in]  Context                The context to the function
 111
 112   @retval EFI_SUCCESS            The UDP IO is successfully configured.
 113   @retval Others                 Failed to configure the UDP child.
 114
 115 **/
 116 EFI_STATUS
 117 DhcpConfigUdpIo (
 118   IN UDP_IO                 *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->Protocol.Udp4->Configure (UdpIo->Protocol.Udp4, &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     UdpIoFreeIo (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 = UdpIoCreateIo (
 241                     Controller,
 242                     ImageHandle,
 243                     DhcpConfigUdpIo,
 244                     UDP_IO_UDP4_VERSION,
 245                     NULL
 246                     );
 247
 248   if (DhcpSb->UdpIo == NULL) {
 249     Status = EFI_OUT_OF_RESOURCES;
 250     goto ON_ERROR;
 251   }
 252
 253   DhcpSb->HwLen  = (UINT8) DhcpSb->UdpIo->SnpMode.HwAddressSize;
 254   DhcpSb->HwType = DhcpSb->UdpIo->SnpMode.IfType;
 255   CopyMem (&DhcpSb->Mac, &DhcpSb->UdpIo->SnpMode.CurrentAddress, sizeof (DhcpSb->Mac));
 256
 257   *Service       = DhcpSb;
 258   return EFI_SUCCESS;
 259
 260 ON_ERROR:
 261   Dhcp4CloseService (DhcpSb);
 262   FreePool (DhcpSb);
 263
 264   return Status;
 265 }
 266
 267
 268 /**
 269   Start this driver on ControllerHandle. This service is called by the
 270   EFI boot service ConnectController(). In order to make
 271   drivers as small as possible, there are a few calling restrictions for
 272   this service. ConnectController() must follow these
 273   calling restrictions. If any other agent wishes to call Start() it
 274   must also follow these calling restrictions.
 275
 276   @param[in]  This                 Protocol instance pointer.
 277   @param[in]  ControllerHandle     Handle of device to bind driver to
 278   @param[in]  RemainingDevicePath  Optional parameter use to pick a specific child
 279                                    device to start.
 280
 281   @retval EFI_SUCCESS          This driver is added to ControllerHandle
 282   @retval EFI_ALREADY_STARTED  This driver is already running on ControllerHandle
 283   @retval other                This driver does not support this device
 284
 285 **/
 286 EFI_STATUS
 287 EFIAPI
 288 Dhcp4DriverBindingStart (
 289   IN EFI_DRIVER_BINDING_PROTOCOL  *This,
 290   IN EFI_HANDLE                   ControllerHandle,
 291   IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath OPTIONAL
 292   )
 293 {
 294   DHCP_SERVICE              *DhcpSb;
 295   EFI_STATUS                Status;
 296
 297   //
 298   // First: test for the DHCP4 Protocol
 299   //
 300   Status = gBS->OpenProtocol (
 301                   ControllerHandle,
 302                   &gEfiDhcp4ServiceBindingProtocolGuid,
 303                   NULL,
 304                   This->DriverBindingHandle,
 305                   ControllerHandle,
 306                   EFI_OPEN_PROTOCOL_TEST_PROTOCOL
 307                   );
 308
 309   if (Status == EFI_SUCCESS) {
 310     return EFI_ALREADY_STARTED;
 311   }
 312
 313   Status = Dhcp4CreateService (ControllerHandle, This->DriverBindingHandle, &DhcpSb);
 314
 315   if (EFI_ERROR (Status)) {
 316     return Status;
 317   }
 318   ASSERT (DhcpSb != NULL);
 319
 320   //
 321   // Start the receiving
 322   //
 323   Status = UdpIoRecvDatagram (DhcpSb->UdpIo, DhcpInput, DhcpSb, 0);
 324
 325   if (EFI_ERROR (Status)) {
 326     goto ON_ERROR;
 327   }
 328   Status = gBS->SetTimer (DhcpSb->Timer, TimerPeriodic, TICKS_PER_SECOND);
 329
 330   if (EFI_ERROR (Status)) {
 331     goto ON_ERROR;
 332   }
 333
 334   //
 335   // Install the Dhcp4ServiceBinding Protocol onto ControlerHandle
 336   //
 337   Status = gBS->InstallMultipleProtocolInterfaces (
 338                   &ControllerHandle,
 339                   &gEfiDhcp4ServiceBindingProtocolGuid,
 340                   &DhcpSb->ServiceBinding,
 341                   NULL
 342                   );
 343
 344   if (EFI_ERROR (Status)) {
 345     goto ON_ERROR;
 346   }
 347
 348   return Status;
 349
 350 ON_ERROR:
 351   Dhcp4CloseService (DhcpSb);
 352   FreePool (DhcpSb);
 353   return Status;
 354 }
 355
 356
 357 /**
 358   Stop this driver on ControllerHandle. This service is called by the
 359   EFI boot service DisconnectController(). In order to
 360   make drivers as small as possible, there are a few calling
 361   restrictions for this service. DisconnectController()
 362   must follow these calling restrictions. If any other agent wishes
 363   to call Stop() it must also follow these calling restrictions.
 364
 365   @param[in]  This              Protocol instance pointer.
 366   @param[in]  ControllerHandle  Handle of device to stop driver on
 367   @param[in]  NumberOfChildren  Number of Handles in ChildHandleBuffer. If number of
 368                                 children is zero stop the entire bus driver.
 369   @param[in]  ChildHandleBuffer List of Child Handles to Stop.
 370
 371   @retval EFI_SUCCESS       This driver is removed ControllerHandle
 372   @retval other             This driver was not removed from this device
 373
 374 **/
 375 EFI_STATUS
 376 EFIAPI
 377 Dhcp4DriverBindingStop (
 378   IN  EFI_DRIVER_BINDING_PROTOCOL  *This,
 379   IN  EFI_HANDLE                   ControllerHandle,
 380   IN  UINTN                        NumberOfChildren,
 381   IN  EFI_HANDLE                   *ChildHandleBuffer
 382   )
 383 {
 384   EFI_SERVICE_BINDING_PROTOCOL  *ServiceBinding;
 385   DHCP_SERVICE                  *DhcpSb;
 386   DHCP_PROTOCOL                 *Instance;
 387   EFI_HANDLE                    NicHandle;
 388   EFI_STATUS                    Status;
 389   EFI_TPL                       OldTpl;
 390
 391   //
 392   // DHCP driver opens UDP child, So, the ControllerHandle is the
 393   // UDP child handle. locate the Nic handle first.
 394   //
 395   NicHandle = NetLibGetNicHandle (ControllerHandle, &gEfiUdp4ProtocolGuid);
 396
 397   if (NicHandle == NULL) {
 398     return EFI_DEVICE_ERROR;
 399   }
 400
 401    Status = gBS->OpenProtocol (
 402                   NicHandle,
 403                   &gEfiDhcp4ServiceBindingProtocolGuid,
 404                   (VOID **) &ServiceBinding,
 405                   This->DriverBindingHandle,
 406                   NicHandle,
 407                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
 408                   );
 409
 410   if (EFI_ERROR (Status)) {
 411     return EFI_DEVICE_ERROR;
 412   }
 413
 414   DhcpSb = DHCP_SERVICE_FROM_THIS (ServiceBinding);
 415
 416   if (DhcpSb->InDestory) {
 417     return EFI_SUCCESS;
 418   }
 419
 420   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 421
 422   if (NumberOfChildren == 0) {
 423
 424     DhcpSb->InDestory    = TRUE;
 425     DhcpSb->ServiceState = DHCP_DESTORY;
 426
 427     gBS->UninstallProtocolInterface (
 428            NicHandle,
 429            &gEfiDhcp4ServiceBindingProtocolGuid,
 430            ServiceBinding
 431            );
 432
 433     Dhcp4CloseService (DhcpSb);
 434
 435     FreePool (DhcpSb);
 436   } else {
 437     //
 438     // Don't use NET_LIST_FOR_EACH_SAFE here, Dhcp4ServiceBindingDestoryChild
 439     // may cause other child to be deleted.
 440     //
 441     while (!IsListEmpty (&DhcpSb->Children)) {
 442       Instance = NET_LIST_HEAD (&DhcpSb->Children, DHCP_PROTOCOL, Link);
 443       ServiceBinding->DestroyChild (ServiceBinding, Instance->Handle);
 444     }
 445
 446     if (DhcpSb->NumChildren != 0) {
 447       Status = EFI_DEVICE_ERROR;
 448     }
 449   }
 450
 451   gBS->RestoreTPL (OldTpl);
 452
 453   return Status;
 454 }
 455
 456
 457 /**
 458   Initialize a new DHCP instance.
 459
 460   @param  DhcpSb                 The dhcp service instance
 461   @param  Instance               The dhcp instance to initialize
 462
 463 **/
 464 VOID
 465 DhcpInitProtocol (
 466   IN     DHCP_SERVICE           *DhcpSb,
 467   IN OUT DHCP_PROTOCOL          *Instance
 468   )
 469 {
 470   Instance->Signature         = DHCP_PROTOCOL_SIGNATURE;
 471   CopyMem (&Instance->Dhcp4Protocol, &mDhcp4ProtocolTemplate, sizeof (Instance->Dhcp4Protocol));
 472   InitializeListHead (&Instance->Link);
 473   Instance->Handle            = NULL;
 474   Instance->Service           = DhcpSb;
 475   Instance->InDestory         = FALSE;
 476   Instance->CompletionEvent   = NULL;
 477   Instance->RenewRebindEvent  = NULL;
 478   Instance->Token             = NULL;
 479   Instance->UdpIo             = NULL;
 480   NetbufQueInit (&Instance->ResponseQueue);
 481 }
 482
 483
 484 /**
 485   Creates a child handle and installs a protocol.
 486
 487   The CreateChild() function installs a protocol on ChildHandle.
 488   If ChildHandle is a pointer to NULL, then a new handle is created and returned in ChildHandle.
 489   If ChildHandle is not a pointer to NULL, then the protocol installs on the existing ChildHandle.
 490
 491   @param  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
 492   @param  ChildHandle Pointer to the handle of the child to create. If it is NULL,
 493                       then a new handle is created. If it is a pointer to an existing UEFI handle,
 494                       then the protocol is added to the existing UEFI handle.
 495
 496   @retval EFI_SUCCES            The protocol was added to ChildHandle.
 497   @retval EFI_INVALID_PARAMETER ChildHandle is NULL.
 498   @retval EFI_OUT_OF_RESOURCES  There are not enough resources availabe to create
 499                                 the child
 500   @retval other                 The child handle was not created
 501
 502 **/
 503 EFI_STATUS
 504 EFIAPI
 505 Dhcp4ServiceBindingCreateChild (
 506   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
 507   IN EFI_HANDLE                    *ChildHandle
 508   )
 509 {
 510   DHCP_SERVICE              *DhcpSb;
 511   DHCP_PROTOCOL             *Instance;
 512   EFI_STATUS                Status;
 513   EFI_TPL                   OldTpl;
 514   VOID                      *Udp4;
 515
 516   if ((This == NULL) || (ChildHandle == NULL)) {
 517     return EFI_INVALID_PARAMETER;
 518   }
 519
 520   Instance = AllocatePool (sizeof (*Instance));
 521
 522   if (Instance == NULL) {
 523     return EFI_OUT_OF_RESOURCES;
 524   }
 525
 526   DhcpSb = DHCP_SERVICE_FROM_THIS (This);
 527   DhcpInitProtocol (DhcpSb, Instance);
 528
 529   //
 530   // Install DHCP4 onto ChildHandle
 531   //
 532   Status = gBS->InstallMultipleProtocolInterfaces (
 533                   ChildHandle,
 534                   &gEfiDhcp4ProtocolGuid,
 535                   &Instance->Dhcp4Protocol,
 536                   NULL
 537                   );
 538
 539   if (EFI_ERROR (Status)) {
 540     FreePool (Instance);
 541     return Status;
 542   }
 543
 544   Instance->Handle  = *ChildHandle;
 545
 546   //
 547   // Open the Udp4 protocol BY_CHILD.
 548   //
 549   Status = gBS->OpenProtocol (
 550                   DhcpSb->UdpIo->UdpHandle,
 551                   &gEfiUdp4ProtocolGuid,
 552                   (VOID **) &Udp4,
 553                   gDhcp4DriverBinding.DriverBindingHandle,
 554                   Instance->Handle,
 555                   EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
 556                   );
 557   if (EFI_ERROR (Status)) {
 558     gBS->UninstallMultipleProtocolInterfaces (
 559            Instance->Handle,
 560            &gEfiDhcp4ProtocolGuid,
 561            &Instance->Dhcp4Protocol,
 562            NULL
 563            );
 564
 565     FreePool (Instance);
 566     return Status;
 567   }
 568
 569   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 570
 571   InsertTailList (&DhcpSb->Children, &Instance->Link);
 572   DhcpSb->NumChildren++;
 573
 574   gBS->RestoreTPL (OldTpl);
 575
 576   return EFI_SUCCESS;
 577 }
 578
 579
 580 /**
 581   Destroys a child handle with a protocol installed on it.
 582
 583   The DestroyChild() function does the opposite of CreateChild(). It removes a protocol
 584   that was installed by CreateChild() from ChildHandle. If the removed protocol is the
 585   last protocol on ChildHandle, then ChildHandle is destroyed.
 586
 587   @param  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
 588   @param  ChildHandle Handle of the child to destroy
 589
 590   @retval EFI_SUCCES            The protocol was removed from ChildHandle.
 591   @retval EFI_UNSUPPORTED       ChildHandle does not support the protocol that is being removed.
 592   @retval EFI_INVALID_PARAMETER Child handle is not a valid UEFI Handle.
 593   @retval EFI_ACCESS_DENIED     The protocol could not be removed from the ChildHandle
 594                                 because its services are being used.
 595   @retval other                 The child handle was not destroyed
 596
 597 **/
 598 EFI_STATUS
 599 EFIAPI
 600 Dhcp4ServiceBindingDestroyChild (
 601   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
 602   IN EFI_HANDLE                    ChildHandle
 603   )
 604 {
 605   DHCP_SERVICE              *DhcpSb;
 606   DHCP_PROTOCOL             *Instance;
 607   EFI_DHCP4_PROTOCOL        *Dhcp;
 608   EFI_TPL                   OldTpl;
 609   EFI_STATUS                Status;
 610
 611   if ((This == NULL) || (ChildHandle == NULL)) {
 612     return EFI_INVALID_PARAMETER;
 613   }
 614
 615   //
 616   // Retrieve the private context data structures
 617   //
 618   Status = gBS->OpenProtocol (
 619                   ChildHandle,
 620                   &gEfiDhcp4ProtocolGuid,
 621                   (VOID **) &Dhcp,
 622                   gDhcp4DriverBinding.DriverBindingHandle,
 623                   ChildHandle,
 624                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
 625                   );
 626
 627   if (EFI_ERROR (Status)) {
 628     return EFI_UNSUPPORTED;
 629   }
 630
 631   Instance  = DHCP_INSTANCE_FROM_THIS (Dhcp);
 632   DhcpSb    = DHCP_SERVICE_FROM_THIS (This);
 633
 634   if (Instance->Service != DhcpSb) {
 635     return EFI_INVALID_PARAMETER;
 636   }
 637
 638   //
 639   // A child can be destroyed more than once. For example,
 640   // Dhcp4DriverBindingStop will destroy all of its children.
 641   // when caller driver is being stopped, it will destory the
 642   // dhcp child it opens.
 643   //
 644   if (Instance->InDestory) {
 645     return EFI_SUCCESS;
 646   }
 647
 648   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 649   Instance->InDestory = TRUE;
 650
 651   //
 652   // Close the Udp4 protocol.
 653   //
 654   gBS->CloseProtocol (
 655          DhcpSb->UdpIo->UdpHandle,
 656          &gEfiUdp4ProtocolGuid,
 657          gDhcp4DriverBinding.DriverBindingHandle,
 658          ChildHandle
 659          );
 660
 661   //
 662   // Uninstall the DHCP4 protocol first to enable a top down destruction.
 663   //
 664   Status = gBS->UninstallProtocolInterface (
 665                   ChildHandle,
 666                   &gEfiDhcp4ProtocolGuid,
 667                   Dhcp
 668                   );
 669
 670   if (EFI_ERROR (Status)) {
 671     Instance->InDestory = FALSE;
 672
 673     gBS->RestoreTPL (OldTpl);
 674     return Status;
 675   }
 676
 677   if (DhcpSb->ActiveChild == Instance) {
 678     DhcpYieldControl (DhcpSb);
 679   }
 680
 681   RemoveEntryList (&Instance->Link);
 682   DhcpSb->NumChildren--;
 683
 684   gBS->RestoreTPL (OldTpl);
 685
 686   FreePool (Instance);
 687   return EFI_SUCCESS;
 688 }