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 EFIAPI
 118 DhcpConfigUdpIo (
 119   IN UDP_IO                 *UdpIo,
 120   IN VOID                   *Context
 121   )
 122 {
 123   EFI_UDP4_CONFIG_DATA      UdpConfigData;
 124
 125   UdpConfigData.AcceptBroadcast           = TRUE;
 126   UdpConfigData.AcceptPromiscuous         = FALSE;
 127   UdpConfigData.AcceptAnyPort             = FALSE;
 128   UdpConfigData.AllowDuplicatePort        = TRUE;
 129   UdpConfigData.TypeOfService             = 0;
 130   UdpConfigData.TimeToLive                = 64;
 131   UdpConfigData.DoNotFragment             = FALSE;
 132   UdpConfigData.ReceiveTimeout            = 0;
 133   UdpConfigData.TransmitTimeout           = 0;
 134
 135   UdpConfigData.UseDefaultAddress         = FALSE;
 136   UdpConfigData.StationPort               = DHCP_CLIENT_PORT;
 137   UdpConfigData.RemotePort                = DHCP_SERVER_PORT;
 138
 139   ZeroMem (&UdpConfigData.StationAddress, sizeof (EFI_IPv4_ADDRESS));
 140   ZeroMem (&UdpConfigData.SubnetMask, sizeof (EFI_IPv4_ADDRESS));
 141   ZeroMem (&UdpConfigData.RemoteAddress, sizeof (EFI_IPv4_ADDRESS));
 142
 143   return UdpIo->Protocol.Udp4->Configure (UdpIo->Protocol.Udp4, &UdpConfigData);;
 144 }
 145
 146
 147
 148 /**
 149   Destory the DHCP service. The Dhcp4 service may be partly initialized,
 150   or partly destroyed. If a resource is destroyed, it is marked as so in
 151   case the destroy failed and being called again later.
 152
 153   @param[in]  DhcpSb                 The DHCP service instance to destory.
 154
 155   @retval EFI_SUCCESS            Always return success.
 156
 157 **/
 158 EFI_STATUS
 159 Dhcp4CloseService (
 160   IN DHCP_SERVICE           *DhcpSb
 161   )
 162 {
 163   DhcpCleanLease (DhcpSb);
 164
 165   if (DhcpSb->UdpIo != NULL) {
 166     UdpIoFreeIo (DhcpSb->UdpIo);
 167     DhcpSb->UdpIo = NULL;
 168   }
 169
 170   if (DhcpSb->Timer != NULL) {
 171     gBS->SetTimer (DhcpSb->Timer, TimerCancel, 0);
 172     gBS->CloseEvent (DhcpSb->Timer);
 173
 174     DhcpSb->Timer = NULL;
 175   }
 176
 177   return EFI_SUCCESS;
 178 }
 179
 180
 181
 182 /**
 183   Create a new DHCP service binding instance for the controller.
 184
 185   @param[in]  Controller             The controller to install DHCP service binding
 186                                      protocol onto
 187   @param[in]  ImageHandle            The driver's image handle
 188   @param[out] Service                The variable to receive the created DHCP service
 189                                      instance.
 190
 191   @retval EFI_OUT_OF_RESOURCES   Failed to allocate resource .
 192   @retval EFI_SUCCESS            The DHCP service instance is created.
 193   @retval other                  Other error occurs.
 194
 195 **/
 196 EFI_STATUS
 197 Dhcp4CreateService (
 198   IN  EFI_HANDLE            Controller,
 199   IN  EFI_HANDLE            ImageHandle,
 200   OUT DHCP_SERVICE          **Service
 201   )
 202 {
 203   DHCP_SERVICE              *DhcpSb;
 204   EFI_STATUS                Status;
 205
 206   *Service  = NULL;
 207   DhcpSb    = AllocateZeroPool (sizeof (DHCP_SERVICE));
 208
 209   if (DhcpSb == NULL) {
 210     return EFI_OUT_OF_RESOURCES;
 211   }
 212
 213   DhcpSb->Signature       = DHCP_SERVICE_SIGNATURE;
 214   DhcpSb->ServiceState    = DHCP_UNCONFIGED;
 215   DhcpSb->InDestory       = FALSE;
 216   DhcpSb->Controller      = Controller;
 217   DhcpSb->Image           = ImageHandle;
 218   InitializeListHead (&DhcpSb->Children);
 219   DhcpSb->DhcpState       = Dhcp4Stopped;
 220   DhcpSb->Xid             = NET_RANDOM (NetRandomInitSeed ());
 221   CopyMem (
 222     &DhcpSb->ServiceBinding,
 223     &mDhcp4ServiceBindingTemplate,
 224     sizeof (EFI_SERVICE_BINDING_PROTOCOL)
 225     );
 226   //
 227   // Create various resources, UdpIo, Timer, and get Mac address
 228   //
 229   Status = gBS->CreateEvent (
 230                   EVT_NOTIFY_SIGNAL | EVT_TIMER,
 231                   TPL_CALLBACK,
 232                   DhcpOnTimerTick,
 233                   DhcpSb,
 234                   &DhcpSb->Timer
 235                   );
 236
 237   if (EFI_ERROR (Status)) {
 238     goto ON_ERROR;
 239   }
 240
 241   DhcpSb->UdpIo = UdpIoCreateIo (
 242                     Controller,
 243                     ImageHandle,
 244                     DhcpConfigUdpIo,
 245                     UDP_IO_UDP4_VERSION,
 246                     NULL
 247                     );
 248
 249   if (DhcpSb->UdpIo == NULL) {
 250     Status = EFI_OUT_OF_RESOURCES;
 251     goto ON_ERROR;
 252   }
 253
 254   DhcpSb->HwLen  = (UINT8) DhcpSb->UdpIo->SnpMode.HwAddressSize;
 255   DhcpSb->HwType = DhcpSb->UdpIo->SnpMode.IfType;
 256   CopyMem (&DhcpSb->Mac, &DhcpSb->UdpIo->SnpMode.CurrentAddress, sizeof (DhcpSb->Mac));
 257
 258   *Service       = DhcpSb;
 259   return EFI_SUCCESS;
 260
 261 ON_ERROR:
 262   Dhcp4CloseService (DhcpSb);
 263   FreePool (DhcpSb);
 264
 265   return Status;
 266 }
 267
 268
 269 /**
 270   Start this driver on ControllerHandle. This service is called by the
 271   EFI boot service ConnectController(). In order to make
 272   drivers as small as possible, there are a few calling restrictions for
 273   this service. ConnectController() must follow these
 274   calling restrictions. If any other agent wishes to call Start() it
 275   must also follow these calling restrictions.
 276
 277   @param[in]  This                 Protocol instance pointer.
 278   @param[in]  ControllerHandle     Handle of device to bind driver to
 279   @param[in]  RemainingDevicePath  Optional parameter use to pick a specific child
 280                                    device to start.
 281
 282   @retval EFI_SUCCESS          This driver is added to ControllerHandle
 283   @retval EFI_ALREADY_STARTED  This driver is already running on ControllerHandle
 284   @retval other                This driver does not support this device
 285
 286 **/
 287 EFI_STATUS
 288 EFIAPI
 289 Dhcp4DriverBindingStart (
 290   IN EFI_DRIVER_BINDING_PROTOCOL  *This,
 291   IN EFI_HANDLE                   ControllerHandle,
 292   IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath OPTIONAL
 293   )
 294 {
 295   DHCP_SERVICE              *DhcpSb;
 296   EFI_STATUS                Status;
 297
 298   //
 299   // First: test for the DHCP4 Protocol
 300   //
 301   Status = gBS->OpenProtocol (
 302                   ControllerHandle,
 303                   &gEfiDhcp4ServiceBindingProtocolGuid,
 304                   NULL,
 305                   This->DriverBindingHandle,
 306                   ControllerHandle,
 307                   EFI_OPEN_PROTOCOL_TEST_PROTOCOL
 308                   );
 309
 310   if (Status == EFI_SUCCESS) {
 311     return EFI_ALREADY_STARTED;
 312   }
 313
 314   Status = Dhcp4CreateService (ControllerHandle, This->DriverBindingHandle, &DhcpSb);
 315
 316   if (EFI_ERROR (Status)) {
 317     return Status;
 318   }
 319   ASSERT (DhcpSb != NULL);
 320
 321   //
 322   // Start the receiving
 323   //
 324   Status = UdpIoRecvDatagram (DhcpSb->UdpIo, DhcpInput, DhcpSb, 0);
 325
 326   if (EFI_ERROR (Status)) {
 327     goto ON_ERROR;
 328   }
 329   Status = gBS->SetTimer (DhcpSb->Timer, TimerPeriodic, TICKS_PER_SECOND);
 330
 331   if (EFI_ERROR (Status)) {
 332     goto ON_ERROR;
 333   }
 334
 335   //
 336   // Install the Dhcp4ServiceBinding Protocol onto ControlerHandle
 337   //
 338   Status = gBS->InstallMultipleProtocolInterfaces (
 339                   &ControllerHandle,
 340                   &gEfiDhcp4ServiceBindingProtocolGuid,
 341                   &DhcpSb->ServiceBinding,
 342                   NULL
 343                   );
 344
 345   if (EFI_ERROR (Status)) {
 346     goto ON_ERROR;
 347   }
 348
 349   return Status;
 350
 351 ON_ERROR:
 352   Dhcp4CloseService (DhcpSb);
 353   FreePool (DhcpSb);
 354   return Status;
 355 }
 356
 357
 358 /**
 359   Stop this driver on ControllerHandle. This service is called by the
 360   EFI boot service DisconnectController(). In order to
 361   make drivers as small as possible, there are a few calling
 362   restrictions for this service. DisconnectController()
 363   must follow these calling restrictions. If any other agent wishes
 364   to call Stop() it must also follow these calling restrictions.
 365
 366   @param[in]  This              Protocol instance pointer.
 367   @param[in]  ControllerHandle  Handle of device to stop driver on
 368   @param[in]  NumberOfChildren  Number of Handles in ChildHandleBuffer. If number of
 369                                 children is zero stop the entire bus driver.
 370   @param[in]  ChildHandleBuffer List of Child Handles to Stop.
 371
 372   @retval EFI_SUCCESS       This driver is removed ControllerHandle
 373   @retval other             This driver was not removed from this device
 374
 375 **/
 376 EFI_STATUS
 377 EFIAPI
 378 Dhcp4DriverBindingStop (
 379   IN  EFI_DRIVER_BINDING_PROTOCOL  *This,
 380   IN  EFI_HANDLE                   ControllerHandle,
 381   IN  UINTN                        NumberOfChildren,
 382   IN  EFI_HANDLE                   *ChildHandleBuffer
 383   )
 384 {
 385   EFI_SERVICE_BINDING_PROTOCOL  *ServiceBinding;
 386   DHCP_SERVICE                  *DhcpSb;
 387   DHCP_PROTOCOL                 *Instance;
 388   EFI_HANDLE                    NicHandle;
 389   EFI_STATUS                    Status;
 390   EFI_TPL                       OldTpl;
 391
 392   //
 393   // DHCP driver opens UDP child, So, the ControllerHandle is the
 394   // UDP child handle. locate the Nic handle first.
 395   //
 396   NicHandle = NetLibGetNicHandle (ControllerHandle, &gEfiUdp4ProtocolGuid);
 397
 398   if (NicHandle == NULL) {
 399     return EFI_DEVICE_ERROR;
 400   }
 401
 402    Status = gBS->OpenProtocol (
 403                   NicHandle,
 404                   &gEfiDhcp4ServiceBindingProtocolGuid,
 405                   (VOID **) &ServiceBinding,
 406                   This->DriverBindingHandle,
 407                   NicHandle,
 408                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
 409                   );
 410
 411   if (EFI_ERROR (Status)) {
 412     return EFI_DEVICE_ERROR;
 413   }
 414
 415   DhcpSb = DHCP_SERVICE_FROM_THIS (ServiceBinding);
 416
 417   if (DhcpSb->InDestory) {
 418     return EFI_SUCCESS;
 419   }
 420
 421   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 422
 423   if (NumberOfChildren == 0) {
 424
 425     DhcpSb->InDestory    = TRUE;
 426     DhcpSb->ServiceState = DHCP_DESTORY;
 427
 428     gBS->UninstallProtocolInterface (
 429            NicHandle,
 430            &gEfiDhcp4ServiceBindingProtocolGuid,
 431            ServiceBinding
 432            );
 433
 434     Dhcp4CloseService (DhcpSb);
 435
 436     FreePool (DhcpSb);
 437   } else {
 438     //
 439     // Don't use NET_LIST_FOR_EACH_SAFE here, Dhcp4ServiceBindingDestoryChild
 440     // may cause other child to be deleted.
 441     //
 442     while (!IsListEmpty (&DhcpSb->Children)) {
 443       Instance = NET_LIST_HEAD (&DhcpSb->Children, DHCP_PROTOCOL, Link);
 444       ServiceBinding->DestroyChild (ServiceBinding, Instance->Handle);
 445     }
 446
 447     if (DhcpSb->NumChildren != 0) {
 448       Status = EFI_DEVICE_ERROR;
 449     }
 450   }
 451
 452   gBS->RestoreTPL (OldTpl);
 453
 454   return Status;
 455 }
 456
 457
 458 /**
 459   Initialize a new DHCP instance.
 460
 461   @param  DhcpSb                 The dhcp service instance
 462   @param  Instance               The dhcp instance to initialize
 463
 464 **/
 465 VOID
 466 DhcpInitProtocol (
 467   IN     DHCP_SERVICE           *DhcpSb,
 468   IN OUT DHCP_PROTOCOL          *Instance
 469   )
 470 {
 471   Instance->Signature         = DHCP_PROTOCOL_SIGNATURE;
 472   CopyMem (&Instance->Dhcp4Protocol, &mDhcp4ProtocolTemplate, sizeof (Instance->Dhcp4Protocol));
 473   InitializeListHead (&Instance->Link);
 474   Instance->Handle            = NULL;
 475   Instance->Service           = DhcpSb;
 476   Instance->InDestory         = FALSE;
 477   Instance->CompletionEvent   = NULL;
 478   Instance->RenewRebindEvent  = NULL;
 479   Instance->Token             = NULL;
 480   Instance->UdpIo             = NULL;
 481   NetbufQueInit (&Instance->ResponseQueue);
 482 }
 483
 484
 485 /**
 486   Creates a child handle and installs a protocol.
 487
 488   The CreateChild() function installs a protocol on ChildHandle.
 489   If ChildHandle is a pointer to NULL, then a new handle is created and returned in ChildHandle.
 490   If ChildHandle is not a pointer to NULL, then the protocol installs on the existing ChildHandle.
 491
 492   @param  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
 493   @param  ChildHandle Pointer to the handle of the child to create. If it is NULL,
 494                       then a new handle is created. If it is a pointer to an existing UEFI handle,
 495                       then the protocol is added to the existing UEFI handle.
 496
 497   @retval EFI_SUCCES            The protocol was added to ChildHandle.
 498   @retval EFI_INVALID_PARAMETER ChildHandle is NULL.
 499   @retval EFI_OUT_OF_RESOURCES  There are not enough resources availabe to create
 500                                 the child
 501   @retval other                 The child handle was not created
 502
 503 **/
 504 EFI_STATUS
 505 EFIAPI
 506 Dhcp4ServiceBindingCreateChild (
 507   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
 508   IN EFI_HANDLE                    *ChildHandle
 509   )
 510 {
 511   DHCP_SERVICE              *DhcpSb;
 512   DHCP_PROTOCOL             *Instance;
 513   EFI_STATUS                Status;
 514   EFI_TPL                   OldTpl;
 515   VOID                      *Udp4;
 516
 517   if ((This == NULL) || (ChildHandle == NULL)) {
 518     return EFI_INVALID_PARAMETER;
 519   }
 520
 521   Instance = AllocatePool (sizeof (*Instance));
 522
 523   if (Instance == NULL) {
 524     return EFI_OUT_OF_RESOURCES;
 525   }
 526
 527   DhcpSb = DHCP_SERVICE_FROM_THIS (This);
 528   DhcpInitProtocol (DhcpSb, Instance);
 529
 530   //
 531   // Install DHCP4 onto ChildHandle
 532   //
 533   Status = gBS->InstallMultipleProtocolInterfaces (
 534                   ChildHandle,
 535                   &gEfiDhcp4ProtocolGuid,
 536                   &Instance->Dhcp4Protocol,
 537                   NULL
 538                   );
 539
 540   if (EFI_ERROR (Status)) {
 541     FreePool (Instance);
 542     return Status;
 543   }
 544
 545   Instance->Handle  = *ChildHandle;
 546
 547   //
 548   // Open the Udp4 protocol BY_CHILD.
 549   //
 550   Status = gBS->OpenProtocol (
 551                   DhcpSb->UdpIo->UdpHandle,
 552                   &gEfiUdp4ProtocolGuid,
 553                   (VOID **) &Udp4,
 554                   gDhcp4DriverBinding.DriverBindingHandle,
 555                   Instance->Handle,
 556                   EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
 557                   );
 558   if (EFI_ERROR (Status)) {
 559     gBS->UninstallMultipleProtocolInterfaces (
 560            Instance->Handle,
 561            &gEfiDhcp4ProtocolGuid,
 562            &Instance->Dhcp4Protocol,
 563            NULL
 564            );
 565
 566     FreePool (Instance);
 567     return Status;
 568   }
 569
 570   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 571
 572   InsertTailList (&DhcpSb->Children, &Instance->Link);
 573   DhcpSb->NumChildren++;
 574
 575   gBS->RestoreTPL (OldTpl);
 576
 577   return EFI_SUCCESS;
 578 }
 579
 580
 581 /**
 582   Destroys a child handle with a protocol installed on it.
 583
 584   The DestroyChild() function does the opposite of CreateChild(). It removes a protocol
 585   that was installed by CreateChild() from ChildHandle. If the removed protocol is the
 586   last protocol on ChildHandle, then ChildHandle is destroyed.
 587
 588   @param  This        Pointer to the EFI_SERVICE_BINDING_PROTOCOL instance.
 589   @param  ChildHandle Handle of the child to destroy
 590
 591   @retval EFI_SUCCES            The protocol was removed from ChildHandle.
 592   @retval EFI_UNSUPPORTED       ChildHandle does not support the protocol that is being removed.
 593   @retval EFI_INVALID_PARAMETER Child handle is not a valid UEFI Handle.
 594   @retval EFI_ACCESS_DENIED     The protocol could not be removed from the ChildHandle
 595                                 because its services are being used.
 596   @retval other                 The child handle was not destroyed
 597
 598 **/
 599 EFI_STATUS
 600 EFIAPI
 601 Dhcp4ServiceBindingDestroyChild (
 602   IN EFI_SERVICE_BINDING_PROTOCOL  *This,
 603   IN EFI_HANDLE                    ChildHandle
 604   )
 605 {
 606   DHCP_SERVICE              *DhcpSb;
 607   DHCP_PROTOCOL             *Instance;
 608   EFI_DHCP4_PROTOCOL        *Dhcp;
 609   EFI_TPL                   OldTpl;
 610   EFI_STATUS                Status;
 611
 612   if ((This == NULL) || (ChildHandle == NULL)) {
 613     return EFI_INVALID_PARAMETER;
 614   }
 615
 616   //
 617   // Retrieve the private context data structures
 618   //
 619   Status = gBS->OpenProtocol (
 620                   ChildHandle,
 621                   &gEfiDhcp4ProtocolGuid,
 622                   (VOID **) &Dhcp,
 623                   gDhcp4DriverBinding.DriverBindingHandle,
 624                   ChildHandle,
 625                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
 626                   );
 627
 628   if (EFI_ERROR (Status)) {
 629     return EFI_UNSUPPORTED;
 630   }
 631
 632   Instance  = DHCP_INSTANCE_FROM_THIS (Dhcp);
 633   DhcpSb    = DHCP_SERVICE_FROM_THIS (This);
 634
 635   if (Instance->Service != DhcpSb) {
 636     return EFI_INVALID_PARAMETER;
 637   }
 638
 639   //
 640   // A child can be destroyed more than once. For example,
 641   // Dhcp4DriverBindingStop will destroy all of its children.
 642   // when caller driver is being stopped, it will destory the
 643   // dhcp child it opens.
 644   //
 645   if (Instance->InDestory) {
 646     return EFI_SUCCESS;
 647   }
 648
 649   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
 650   Instance->InDestory = TRUE;
 651
 652   //
 653   // Close the Udp4 protocol.
 654   //
 655   gBS->CloseProtocol (
 656          DhcpSb->UdpIo->UdpHandle,
 657          &gEfiUdp4ProtocolGuid,
 658          gDhcp4DriverBinding.DriverBindingHandle,
 659          ChildHandle
 660          );
 661
 662   //
 663   // Uninstall the DHCP4 protocol first to enable a top down destruction.
 664   //
 665   Status = gBS->UninstallProtocolInterface (
 666                   ChildHandle,
 667                   &gEfiDhcp4ProtocolGuid,
 668                   Dhcp
 669                   );
 670
 671   if (EFI_ERROR (Status)) {
 672     Instance->InDestory = FALSE;
 673
 674     gBS->RestoreTPL (OldTpl);
 675     return Status;
 676   }
 677
 678   if (DhcpSb->ActiveChild == Instance) {
 679     DhcpYieldControl (DhcpSb);
 680   }
 681
 682   RemoveEntryList (&Instance->Link);
 683   DhcpSb->NumChildren--;
 684
 685   gBS->RestoreTPL (OldTpl);
 686
 687   FreePool (Instance);
 688   return EFI_SUCCESS;
 689 }