NetworkPkg/DnsDxe/DnsDhcp.c - third_party/edk2 - Git at Google

 /** @file
 Functions implementation related with DHCPv4/v6 for DNS driver.

 Copyright (c) 2015 - 2018, Intel Corporation. All rights reserved.<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent

 **/

 #include "DnsImpl.h"

 /**
   This function initialize the DHCP4 message instance.

   This function will pad each item of dhcp4 message packet.

   @param  Seed             Pointer to the message instance of the DHCP4 packet.
   @param  InterfaceInfo    Pointer to the EFI_IP4_CONFIG2_INTERFACE_INFO instance.

 **/
 VOID
 DnsInitSeedPacket (
   OUT EFI_DHCP4_PACKET               *Seed,
   IN  EFI_IP4_CONFIG2_INTERFACE_INFO *InterfaceInfo
   )
 {
   EFI_DHCP4_HEADER           *Header;

   //
   // Get IfType and HwAddressSize from SNP mode data.
   //
   Seed->Size            = sizeof (EFI_DHCP4_PACKET);
   Seed->Length          = sizeof (Seed->Dhcp4);
   Header                = &Seed->Dhcp4.Header;
   ZeroMem (Header, sizeof (EFI_DHCP4_HEADER));
   Header->OpCode        = DHCP4_OPCODE_REQUEST;
   Header->HwType        = InterfaceInfo->IfType;
   Header->HwAddrLen     = (UINT8) InterfaceInfo->HwAddressSize;
   CopyMem (Header->ClientHwAddr, &(InterfaceInfo->HwAddress), Header->HwAddrLen);

   Seed->Dhcp4.Magik     = DHCP4_MAGIC;
   Seed->Dhcp4.Option[0] = DHCP4_TAG_EOP;
 }

 /**
   The common notify function.

   @param[in]  Event   The event signaled.
   @param[in]  Context The context.

 **/
 VOID
 EFIAPI
 DhcpCommonNotify (
   IN EFI_EVENT  Event,
   IN VOID       *Context
   )
 {
   if ((Event == NULL) || (Context == NULL)) {
     return ;
   }

   *((BOOLEAN *) Context) = TRUE;
 }

 /**
   Parse the ACK to get required information

   @param  Dhcp4            The DHCP4 protocol.
   @param  Packet           Packet waiting for parse.
   @param  DnsServerInfor   The required Dns4 server information.

   @retval EFI_SUCCESS           The DNS information is got from the DHCP ACK.
   @retval EFI_NO_MAPPING        DHCP failed to acquire address and other information.
   @retval EFI_DEVICE_ERROR      Other errors as indicated.
   @retval EFI_OUT_OF_RESOURCES  Failed to allocate memory.

 **/
 EFI_STATUS
 ParseDhcp4Ack (
   IN EFI_DHCP4_PROTOCOL         *Dhcp4,
   IN EFI_DHCP4_PACKET           *Packet,
   IN DNS4_SERVER_INFOR          *DnsServerInfor
   )
 {
   EFI_STATUS              Status;
   UINT32                  OptionCount;
   EFI_DHCP4_PACKET_OPTION **OptionList;
   UINT32                  ServerCount;
   EFI_IPv4_ADDRESS        *ServerList;
   UINT32                  Index;
   UINT32                  Count;

   ServerCount = 0;
   ServerList = NULL;

   OptionCount = 0;
   OptionList  = NULL;

   Status      = Dhcp4->Parse (Dhcp4, Packet, &OptionCount, OptionList);
   if (Status != EFI_BUFFER_TOO_SMALL) {
     return EFI_DEVICE_ERROR;
   }

   OptionList = AllocatePool (OptionCount * sizeof (EFI_DHCP4_PACKET_OPTION *));
   if (OptionList == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }

   Status = Dhcp4->Parse (Dhcp4, Packet, &OptionCount, OptionList);
   if (EFI_ERROR (Status)) {
     gBS->FreePool (OptionList);
     return EFI_DEVICE_ERROR;
   }

   Status = EFI_NOT_FOUND;

   for (Index = 0; Index < OptionCount; Index++) {
     //
     // Get DNS server addresses
     //
     if (OptionList[Index]->OpCode == DHCP4_TAG_DNS_SERVER) {

       if (((OptionList[Index]->Length & 0x3) != 0) || (OptionList[Index]->Length == 0)) {
         Status = EFI_DEVICE_ERROR;
         break;
       }

       ServerCount = OptionList[Index]->Length/4;
       ServerList = AllocatePool (ServerCount * sizeof (EFI_IPv4_ADDRESS));
       if (ServerList == NULL) {
         return EFI_OUT_OF_RESOURCES;
       }

       for (Count=0; Count < ServerCount; Count++) {
         CopyMem (ServerList + Count, &OptionList[Index]->Data[4 * Count], sizeof (EFI_IPv4_ADDRESS));
       }

       *(DnsServerInfor->ServerCount) = ServerCount;
       DnsServerInfor->ServerList     = ServerList;

       Status = EFI_SUCCESS;
     }
   }

   gBS->FreePool (OptionList);

   return Status;
 }

 /**
   EFI_DHCP6_INFO_CALLBACK is provided by the consumer of the EFI DHCPv6 Protocol
   instance to intercept events that occurs in the DHCPv6 Information Request
   exchange process.

   @param  This                  Pointer to the EFI_DHCP6_PROTOCOL instance that
                                 is used to configure this  callback function.
   @param  Context               Pointer to the context that is initialized in
                                 the EFI_DHCP6_PROTOCOL.InfoRequest().
   @param  Packet                Pointer to Reply packet that has been received.
                                 The EFI DHCPv6 Protocol instance is responsible
                                 for freeing the buffer.

   @retval EFI_SUCCESS           The DNS information is got from the DHCP ACK.
   @retval EFI_DEVICE_ERROR      Other errors as indicated.
   @retval EFI_OUT_OF_RESOURCES  Failed to allocate memory.
 **/
 EFI_STATUS
 EFIAPI
 ParseDhcp6Ack (
   IN EFI_DHCP6_PROTOCOL          *This,
   IN VOID                        *Context,
   IN EFI_DHCP6_PACKET            *Packet
   )
 {
   EFI_STATUS                  Status;
   UINT32                      OptionCount;
   EFI_DHCP6_PACKET_OPTION     **OptionList;
   DNS6_SERVER_INFOR           *DnsServerInfor;
   UINT32                      ServerCount;
   EFI_IPv6_ADDRESS            *ServerList;
   UINT32                      Index;
   UINT32                      Count;

   OptionCount = 0;
   ServerCount = 0;
   ServerList  = NULL;

   Status      = This->Parse (This, Packet, &OptionCount, NULL);
   if (Status != EFI_BUFFER_TOO_SMALL) {
     return EFI_DEVICE_ERROR;
   }

   OptionList = AllocateZeroPool (OptionCount * sizeof (EFI_DHCP6_PACKET_OPTION *));
   if (OptionList == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }

   Status = This->Parse (This, Packet, &OptionCount, OptionList);
   if (EFI_ERROR (Status)) {
     gBS->FreePool (OptionList);
     return EFI_DEVICE_ERROR;
   }

   DnsServerInfor = (DNS6_SERVER_INFOR *) Context;

   for (Index = 0; Index < OptionCount; Index++) {
     OptionList[Index]->OpCode = NTOHS (OptionList[Index]->OpCode);
     OptionList[Index]->OpLen  = NTOHS (OptionList[Index]->OpLen);

     //
     // Get DNS server addresses from this reply packet.
     //
     if (OptionList[Index]->OpCode == DHCP6_TAG_DNS_SERVER) {

       if (((OptionList[Index]->OpLen & 0xf) != 0) || (OptionList[Index]->OpLen == 0)) {
         Status = EFI_DEVICE_ERROR;
         gBS->FreePool (OptionList);
         return Status;
       }

       ServerCount = OptionList[Index]->OpLen/16;
       ServerList = AllocatePool (ServerCount * sizeof (EFI_IPv6_ADDRESS));
       if (ServerList == NULL) {
         gBS->FreePool (OptionList);
         return EFI_OUT_OF_RESOURCES;
       }

       for (Count=0; Count < ServerCount; Count++) {
         CopyMem (ServerList + Count, &OptionList[Index]->Data[16 * Count], sizeof (EFI_IPv6_ADDRESS));
       }

       *(DnsServerInfor->ServerCount) = ServerCount;
       DnsServerInfor->ServerList     = ServerList;
     }
   }

   gBS->FreePool (OptionList);

   return Status;

 }

 /**
   Parse the DHCP ACK to get Dns4 server information.

   @param  Instance         The DNS instance.
   @param  DnsServerCount   Retrieved Dns4 server Ip count.
   @param  DnsServerList    Retrieved Dns4 server Ip list.

   @retval EFI_SUCCESS           The Dns4 information is got from the DHCP ACK.
   @retval EFI_OUT_OF_RESOURCES  Failed to allocate memory.
   @retval EFI_NO_MEDIA          There was a media error.
   @retval Others                Other errors as indicated.

 **/
 EFI_STATUS
 GetDns4ServerFromDhcp4 (
   IN  DNS_INSTANCE               *Instance,
   OUT UINT32                     *DnsServerCount,
   OUT EFI_IPv4_ADDRESS           **DnsServerList
   )
 {
   EFI_STATUS                          Status;
   EFI_HANDLE                          Image;
   EFI_HANDLE                          Controller;
   EFI_STATUS                          MediaStatus;
   EFI_HANDLE                          MnpChildHandle;
   EFI_MANAGED_NETWORK_PROTOCOL        *Mnp;
   EFI_MANAGED_NETWORK_CONFIG_DATA     MnpConfigData;
   EFI_HANDLE                          Dhcp4Handle;
   EFI_DHCP4_PROTOCOL                  *Dhcp4;
   EFI_IP4_CONFIG2_PROTOCOL            *Ip4Config2;
   UINTN                               DataSize;
   VOID                                *Data;
   EFI_IP4_CONFIG2_INTERFACE_INFO      *InterfaceInfo;
   EFI_DHCP4_PACKET                    SeedPacket;
   EFI_DHCP4_PACKET_OPTION             *ParaList[2];
   DNS4_SERVER_INFOR                   DnsServerInfor;

   EFI_DHCP4_TRANSMIT_RECEIVE_TOKEN    Token;
   BOOLEAN                             IsDone;
   UINTN                               Index;

   Image                      = Instance->Service->ImageHandle;
   Controller                 = Instance->Service->ControllerHandle;

   MnpChildHandle             = NULL;
   Mnp                        = NULL;

   Dhcp4Handle                = NULL;
   Dhcp4                      = NULL;

   Ip4Config2                 = NULL;
   DataSize                   = 0;
   Data                       = NULL;
   InterfaceInfo              = NULL;

   ZeroMem ((UINT8 *) ParaList, sizeof (ParaList));

   ZeroMem (&MnpConfigData, sizeof (EFI_MANAGED_NETWORK_CONFIG_DATA));

   ZeroMem (&DnsServerInfor, sizeof (DNS4_SERVER_INFOR));

   ZeroMem (&Token, sizeof (EFI_DHCP4_TRANSMIT_RECEIVE_TOKEN));

   DnsServerInfor.ServerCount = DnsServerCount;

   IsDone = FALSE;

   //
   // Check media.
   //
   MediaStatus = EFI_SUCCESS;
   NetLibDetectMediaWaitTimeout (Controller, DNS_CHECK_MEDIA_GET_DHCP_WAITING_TIME, &MediaStatus);
   if (MediaStatus != EFI_SUCCESS) {
     return EFI_NO_MEDIA;
   }

   //
   // Create a Mnp child instance, get the protocol and config for it.
   //
   Status = NetLibCreateServiceChild (
              Controller,
              Image,
              &gEfiManagedNetworkServiceBindingProtocolGuid,
              &MnpChildHandle
              );
   if (EFI_ERROR (Status)) {
     return Status;
   }

   Status = gBS->OpenProtocol (
                   MnpChildHandle,
                   &gEfiManagedNetworkProtocolGuid,
                   (VOID **) &Mnp,
                   Image,
                   Controller,
                   EFI_OPEN_PROTOCOL_BY_DRIVER
                   );
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   MnpConfigData.ReceivedQueueTimeoutValue = 0;
   MnpConfigData.TransmitQueueTimeoutValue = 0;
   MnpConfigData.ProtocolTypeFilter        = IP4_ETHER_PROTO;
   MnpConfigData.EnableUnicastReceive      = TRUE;
   MnpConfigData.EnableMulticastReceive    = TRUE;
   MnpConfigData.EnableBroadcastReceive    = TRUE;
   MnpConfigData.EnablePromiscuousReceive  = FALSE;
   MnpConfigData.FlushQueuesOnReset        = TRUE;
   MnpConfigData.EnableReceiveTimestamps   = FALSE;
   MnpConfigData.DisableBackgroundPolling  = FALSE;

   Status = Mnp->Configure(Mnp, &MnpConfigData);
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   //
   // Create a DHCP4 child instance and get the protocol.
   //
   Status = NetLibCreateServiceChild (
              Controller,
              Image,
              &gEfiDhcp4ServiceBindingProtocolGuid,
              &Dhcp4Handle
              );
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   Status = gBS->OpenProtocol (
                   Dhcp4Handle,
                   &gEfiDhcp4ProtocolGuid,
                   (VOID **) &Dhcp4,
                   Image,
                   Controller,
                   EFI_OPEN_PROTOCOL_BY_DRIVER
                   );
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   //
   // Get Ip4Config2 instance info.
   //
   Status = gBS->HandleProtocol (Controller, &gEfiIp4Config2ProtocolGuid, (VOID **) &Ip4Config2);
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   Status = Ip4Config2->GetData (Ip4Config2, Ip4Config2DataTypeInterfaceInfo, &DataSize, Data);
   if (EFI_ERROR (Status) && Status != EFI_BUFFER_TOO_SMALL) {
     goto ON_EXIT;
   }

   Data = AllocateZeroPool (DataSize);
   if (Data == NULL) {
     Status = EFI_OUT_OF_RESOURCES;
     goto ON_EXIT;
   }

   Status = Ip4Config2->GetData (Ip4Config2, Ip4Config2DataTypeInterfaceInfo, &DataSize, Data);
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   InterfaceInfo = (EFI_IP4_CONFIG2_INTERFACE_INFO *)Data;

   //
   // Build required Token.
   //
   Status = gBS->CreateEvent (
                   EVT_NOTIFY_SIGNAL,
                   TPL_NOTIFY,
                   DhcpCommonNotify,
                   &IsDone,
                   &Token.CompletionEvent
                   );
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   SetMem (&Token.RemoteAddress, sizeof (EFI_IPv4_ADDRESS), 0xff);

   Token.RemotePort = 67;

   Token.ListenPointCount = 1;

   Token.ListenPoints = AllocateZeroPool (Token.ListenPointCount * sizeof (EFI_DHCP4_LISTEN_POINT));
   if (Token.ListenPoints == NULL) {
     Status = EFI_OUT_OF_RESOURCES;
     goto ON_EXIT;
   }

   if (Instance->Dns4CfgData.UseDefaultSetting) {
     CopyMem (&(Token.ListenPoints[0].ListenAddress), &(InterfaceInfo->StationAddress), sizeof (EFI_IPv4_ADDRESS));
     CopyMem (&(Token.ListenPoints[0].SubnetMask), &(InterfaceInfo->SubnetMask), sizeof (EFI_IPv4_ADDRESS));
   } else {
     CopyMem (&(Token.ListenPoints[0].ListenAddress), &(Instance->Dns4CfgData.StationIp), sizeof (EFI_IPv4_ADDRESS));
     CopyMem (&(Token.ListenPoints[0].SubnetMask), &(Instance->Dns4CfgData.SubnetMask), sizeof (EFI_IPv4_ADDRESS));
   }

   Token.ListenPoints[0].ListenPort = 68;

   Token.TimeoutValue = DNS_TIME_TO_GETMAP;

   DnsInitSeedPacket (&SeedPacket, InterfaceInfo);

   ParaList[0] = AllocateZeroPool (sizeof (EFI_DHCP4_PACKET_OPTION));
   if (ParaList[0] == NULL) {
     Status = EFI_OUT_OF_RESOURCES;
     goto ON_EXIT;
   }

   ParaList[0]->OpCode  = DHCP4_TAG_TYPE;
   ParaList[0]->Length  = 1;
   ParaList[0]->Data[0] = DHCP4_MSG_REQUEST;

   ParaList[1] = AllocateZeroPool (sizeof (EFI_DHCP4_PACKET_OPTION));
   if (ParaList[1] == NULL) {
     Status = EFI_OUT_OF_RESOURCES;
     goto ON_EXIT;
   }

   ParaList[1]->OpCode  = DHCP4_TAG_PARA_LIST;
   ParaList[1]->Length  = 1;
   ParaList[1]->Data[0] = DHCP4_TAG_DNS_SERVER;

   Status = Dhcp4->Build (Dhcp4, &SeedPacket, 0, NULL, 2, ParaList, &Token.Packet);

   Token.Packet->Dhcp4.Header.Xid      = HTONL(NET_RANDOM (NetRandomInitSeed ()));

   Token.Packet->Dhcp4.Header.Reserved = HTONS ((UINT16)0x8000);

   if (Instance->Dns4CfgData.UseDefaultSetting) {
     CopyMem (&(Token.Packet->Dhcp4.Header.ClientAddr), &(InterfaceInfo->StationAddress), sizeof (EFI_IPv4_ADDRESS));
   } else {
     CopyMem (&(Token.Packet->Dhcp4.Header.ClientAddr), &(Instance->Dns4CfgData.StationIp), sizeof (EFI_IPv4_ADDRESS));
   }

   CopyMem (Token.Packet->Dhcp4.Header.ClientHwAddr, &(InterfaceInfo->HwAddress), InterfaceInfo->HwAddressSize);

   Token.Packet->Dhcp4.Header.HwAddrLen = (UINT8)(InterfaceInfo->HwAddressSize);

   //
   // TransmitReceive Token
   //
   Status = Dhcp4->TransmitReceive (Dhcp4, &Token);
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   //
   // Poll the packet
   //
   do {
     Status = Mnp->Poll (Mnp);
   } while (!IsDone);

   //
   // Parse the ACK to get required information if received done.
   //
   if (IsDone && !EFI_ERROR (Token.Status)) {
     for (Index = 0; Index < Token.ResponseCount; Index++) {
       Status = ParseDhcp4Ack (Dhcp4, &Token.ResponseList[Index], &DnsServerInfor);
       if (!EFI_ERROR (Status)) {
         break;
       }
     }

     *DnsServerList = DnsServerInfor.ServerList;
   } else {
     Status = Token.Status;
   }

 ON_EXIT:

   if (Data != NULL) {
     FreePool (Data);
   }

   for (Index = 0; Index < 2; Index++) {
     if (ParaList[Index] != NULL) {
       FreePool (ParaList[Index]);
     }
   }

   if (Token.ListenPoints) {
     FreePool (Token.ListenPoints);
   }

   if (Token.Packet) {
     FreePool (Token.Packet);
   }

   if (Token.ResponseList != NULL) {
     FreePool (Token.ResponseList);
   }

   if (Token.CompletionEvent != NULL) {
     gBS->CloseEvent (Token.CompletionEvent);
   }

   if (Dhcp4 != NULL) {
     Dhcp4->Stop (Dhcp4);
     Dhcp4->Configure (Dhcp4, NULL);

     gBS->CloseProtocol (
            Dhcp4Handle,
            &gEfiDhcp4ProtocolGuid,
            Image,
            Controller
            );
   }

   if (Dhcp4Handle != NULL) {
     NetLibDestroyServiceChild (
       Controller,
       Image,
       &gEfiDhcp4ServiceBindingProtocolGuid,
       Dhcp4Handle
       );
   }

   if (Mnp != NULL) {
     Mnp->Configure (Mnp, NULL);

     gBS->CloseProtocol (
            MnpChildHandle,
            &gEfiManagedNetworkProtocolGuid,
            Image,
            Controller
            );
   }

   NetLibDestroyServiceChild (
     Controller,
     Image,
     &gEfiManagedNetworkServiceBindingProtocolGuid,
     MnpChildHandle
     );

   return Status;
 }

 /**
   Parse the DHCP ACK to get Dns6 server information.

   @param  Image            The handle of the driver image.
   @param  Controller       The handle of the controller.
   @param  DnsServerCount   Retrieved Dns6 server Ip count.
   @param  DnsServerList    Retrieved Dns6 server Ip list.

   @retval EFI_SUCCESS           The Dns6 information is got from the DHCP ACK.
   @retval EFI_OUT_OF_RESOURCES  Failed to allocate memory.
   @retval EFI_NO_MEDIA          There was a media error.
   @retval Others                Other errors as indicated.

 **/
 EFI_STATUS
 GetDns6ServerFromDhcp6 (
   IN  EFI_HANDLE                 Image,
   IN  EFI_HANDLE                 Controller,
   OUT UINT32                     *DnsServerCount,
   OUT EFI_IPv6_ADDRESS           **DnsServerList
   )
 {
   EFI_HANDLE                Dhcp6Handle;
   EFI_DHCP6_PROTOCOL        *Dhcp6;
   EFI_STATUS                Status;
   EFI_STATUS                TimerStatus;
   EFI_DHCP6_PACKET_OPTION   *Oro;
   EFI_DHCP6_RETRANSMISSION  InfoReqReXmit;
   EFI_EVENT                 Timer;
   EFI_STATUS                MediaStatus;
   DNS6_SERVER_INFOR         DnsServerInfor;

   Dhcp6Handle = NULL;
   Dhcp6       = NULL;
   Oro         = NULL;
   Timer       = NULL;

   ZeroMem (&DnsServerInfor, sizeof (DNS6_SERVER_INFOR));

   DnsServerInfor.ServerCount = DnsServerCount;

   //
   // Check media status before doing DHCP.
   //
   MediaStatus = EFI_SUCCESS;
   NetLibDetectMediaWaitTimeout (Controller, DNS_CHECK_MEDIA_GET_DHCP_WAITING_TIME, &MediaStatus);
   if (MediaStatus != EFI_SUCCESS) {
     return EFI_NO_MEDIA;
   }

   //
   // Create a DHCP6 child instance and get the protocol.
   //
   Status = NetLibCreateServiceChild (
              Controller,
              Image,
              &gEfiDhcp6ServiceBindingProtocolGuid,
              &Dhcp6Handle
              );
   if (EFI_ERROR (Status)) {
     return Status;
   }

   Status = gBS->OpenProtocol (
                   Dhcp6Handle,
                   &gEfiDhcp6ProtocolGuid,
                   (VOID **) &Dhcp6,
                   Image,
                   Controller,
                   EFI_OPEN_PROTOCOL_BY_DRIVER
                   );
   if (EFI_ERROR (Status)) {
     goto ON_EXIT;
   }

   Oro = AllocateZeroPool (sizeof (EFI_DHCP6_PACKET_OPTION) + 1);
   if (Oro == NULL) {
     Status = EFI_OUT_OF_RESOURCES;
     goto ON_EXIT;
   }

   //
   // Ask the server to reply with DNS options.
   // All members in EFI_DHCP6_PACKET_OPTION are in network order.
   //
   Oro->OpCode  = HTONS (DHCP6_TAG_DNS_REQUEST);
   Oro->OpLen   = HTONS (2);
   Oro->Data[1] = DHCP6_TAG_DNS_SERVER;

   InfoReqReXmit.Irt = 4;
   InfoReqReXmit.Mrc = 1;
   InfoReqReXmit.Mrt = 10;
   InfoReqReXmit.Mrd = 30;

   Status = Dhcp6->InfoRequest (
                     Dhcp6,
                     TRUE,
                     Oro,
                     0,
                     NULL,
                     &InfoReqReXmit,
                     NULL,
                     ParseDhcp6Ack,
                     &DnsServerInfor
                     );
   if (Status == EFI_NO_MAPPING) {
     Status = gBS->CreateEvent (EVT_TIMER, TPL_CALLBACK, NULL, NULL, &Timer);
     if (EFI_ERROR (Status)) {
       goto ON_EXIT;
     }

     Status = gBS->SetTimer (
                     Timer,
                     TimerRelative,
                     DNS_TIME_TO_GETMAP * TICKS_PER_SECOND
                     );

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

     do {
       TimerStatus = gBS->CheckEvent (Timer);
       if (!EFI_ERROR (TimerStatus)) {
         Status = Dhcp6->InfoRequest (
                           Dhcp6,
                           TRUE,
                           Oro,
                           0,
                           NULL,
                           &InfoReqReXmit,
                           NULL,
                           ParseDhcp6Ack,
                           &DnsServerInfor
                           );
       }
     } while (TimerStatus == EFI_NOT_READY);
   }

   *DnsServerList  = DnsServerInfor.ServerList;

 ON_EXIT:

   if (Oro != NULL) {
     FreePool (Oro);
   }

   if (Timer != NULL) {
     gBS->CloseEvent (Timer);
   }

   if (Dhcp6 != NULL) {
     gBS->CloseProtocol (
            Dhcp6Handle,
            &gEfiDhcp6ProtocolGuid,
            Image,
            Controller
            );
   }

   NetLibDestroyServiceChild (
     Controller,
     Image,
     &gEfiDhcp6ServiceBindingProtocolGuid,
     Dhcp6Handle
     );

   return Status;

 }
	/** @file
	Functions implementation related with DHCPv4/v6 for DNS driver.

	Copyright (c) 2015 - 2018, Intel Corporation. All rights reserved.<BR>
	SPDX-License-Identifier: BSD-2-Clause-Patent

	**/

	#include "DnsImpl.h"

	/**
	This function initialize the DHCP4 message instance.

	This function will pad each item of dhcp4 message packet.

	@param Seed Pointer to the message instance of the DHCP4 packet.
	@param InterfaceInfo Pointer to the EFI_IP4_CONFIG2_INTERFACE_INFO instance.

	**/
	VOID
	DnsInitSeedPacket (
	OUT EFI_DHCP4_PACKET *Seed,
	IN EFI_IP4_CONFIG2_INTERFACE_INFO *InterfaceInfo
	)
	{
	EFI_DHCP4_HEADER *Header;

	//
	// Get IfType and HwAddressSize from SNP mode data.
	//
	Seed->Size = sizeof (EFI_DHCP4_PACKET);
	Seed->Length = sizeof (Seed->Dhcp4);
	Header = &Seed->Dhcp4.Header;
	ZeroMem (Header, sizeof (EFI_DHCP4_HEADER));
	Header->OpCode = DHCP4_OPCODE_REQUEST;
	Header->HwType = InterfaceInfo->IfType;
	Header->HwAddrLen = (UINT8) InterfaceInfo->HwAddressSize;
	CopyMem (Header->ClientHwAddr, &(InterfaceInfo->HwAddress), Header->HwAddrLen);

	Seed->Dhcp4.Magik = DHCP4_MAGIC;
	Seed->Dhcp4.Option[0] = DHCP4_TAG_EOP;
	}

	/**
	The common notify function.

	@param[in] Event The event signaled.
	@param[in] Context The context.

	**/
	VOID
	EFIAPI
	DhcpCommonNotify (
	IN EFI_EVENT Event,
	IN VOID *Context
	)
	{
	if ((Event == NULL) \|\| (Context == NULL)) {
	return ;
	}

	((BOOLEAN ) Context) = TRUE;
	}

	/**
	Parse the ACK to get required information

	@param Dhcp4 The DHCP4 protocol.
	@param Packet Packet waiting for parse.
	@param DnsServerInfor The required Dns4 server information.

	@retval EFI_SUCCESS The DNS information is got from the DHCP ACK.
	@retval EFI_NO_MAPPING DHCP failed to acquire address and other information.
	@retval EFI_DEVICE_ERROR Other errors as indicated.
	@retval EFI_OUT_OF_RESOURCES Failed to allocate memory.

	**/
	EFI_STATUS
	ParseDhcp4Ack (
	IN EFI_DHCP4_PROTOCOL *Dhcp4,
	IN EFI_DHCP4_PACKET *Packet,
	IN DNS4_SERVER_INFOR *DnsServerInfor
	)
	{
	EFI_STATUS Status;
	UINT32 OptionCount;
	EFI_DHCP4_PACKET_OPTION **OptionList;
	UINT32 ServerCount;
	EFI_IPv4_ADDRESS *ServerList;
	UINT32 Index;
	UINT32 Count;

	ServerCount = 0;
	ServerList = NULL;

	OptionCount = 0;
	OptionList = NULL;

	Status = Dhcp4->Parse (Dhcp4, Packet, &OptionCount, OptionList);
	if (Status != EFI_BUFFER_TOO_SMALL) {
	return EFI_DEVICE_ERROR;
	}

	OptionList = AllocatePool (OptionCount * sizeof (EFI_DHCP4_PACKET_OPTION *));
	if (OptionList == NULL) {
	return EFI_OUT_OF_RESOURCES;
	}

	Status = Dhcp4->Parse (Dhcp4, Packet, &OptionCount, OptionList);
	if (EFI_ERROR (Status)) {
	gBS->FreePool (OptionList);
	return EFI_DEVICE_ERROR;
	}

	Status = EFI_NOT_FOUND;

	for (Index = 0; Index < OptionCount; Index++) {
	//
	// Get DNS server addresses
	//
	if (OptionList[Index]->OpCode == DHCP4_TAG_DNS_SERVER) {

	if (((OptionList[Index]->Length & 0x3) != 0) \|\| (OptionList[Index]->Length == 0)) {
	Status = EFI_DEVICE_ERROR;
	break;
	}

	ServerCount = OptionList[Index]->Length/4;
	ServerList = AllocatePool (ServerCount * sizeof (EFI_IPv4_ADDRESS));
	if (ServerList == NULL) {
	return EFI_OUT_OF_RESOURCES;
	}

	for (Count=0; Count < ServerCount; Count++) {
	CopyMem (ServerList + Count, &OptionList[Index]->Data[4 * Count], sizeof (EFI_IPv4_ADDRESS));
	}

	*(DnsServerInfor->ServerCount) = ServerCount;
	DnsServerInfor->ServerList = ServerList;

	Status = EFI_SUCCESS;
	}
	}

	gBS->FreePool (OptionList);

	return Status;
	}

	/**
	EFI_DHCP6_INFO_CALLBACK is provided by the consumer of the EFI DHCPv6 Protocol
	instance to intercept events that occurs in the DHCPv6 Information Request
	exchange process.

	@param This Pointer to the EFI_DHCP6_PROTOCOL instance that
	is used to configure this callback function.
	@param Context Pointer to the context that is initialized in
	the EFI_DHCP6_PROTOCOL.InfoRequest().
	@param Packet Pointer to Reply packet that has been received.
	The EFI DHCPv6 Protocol instance is responsible
	for freeing the buffer.

	@retval EFI_SUCCESS The DNS information is got from the DHCP ACK.
	@retval EFI_DEVICE_ERROR Other errors as indicated.
	@retval EFI_OUT_OF_RESOURCES Failed to allocate memory.
	**/
	EFI_STATUS
	EFIAPI
	ParseDhcp6Ack (
	IN EFI_DHCP6_PROTOCOL *This,
	IN VOID *Context,
	IN EFI_DHCP6_PACKET *Packet
	)
	{
	EFI_STATUS Status;
	UINT32 OptionCount;
	EFI_DHCP6_PACKET_OPTION **OptionList;
	DNS6_SERVER_INFOR *DnsServerInfor;
	UINT32 ServerCount;
	EFI_IPv6_ADDRESS *ServerList;
	UINT32 Index;
	UINT32 Count;

	OptionCount = 0;
	ServerCount = 0;
	ServerList = NULL;

	Status = This->Parse (This, Packet, &OptionCount, NULL);
	if (Status != EFI_BUFFER_TOO_SMALL) {
	return EFI_DEVICE_ERROR;
	}

	OptionList = AllocateZeroPool (OptionCount * sizeof (EFI_DHCP6_PACKET_OPTION *));
	if (OptionList == NULL) {
	return EFI_OUT_OF_RESOURCES;
	}

	Status = This->Parse (This, Packet, &OptionCount, OptionList);
	if (EFI_ERROR (Status)) {
	gBS->FreePool (OptionList);
	return EFI_DEVICE_ERROR;
	}

	DnsServerInfor = (DNS6_SERVER_INFOR *) Context;

	for (Index = 0; Index < OptionCount; Index++) {
	OptionList[Index]->OpCode = NTOHS (OptionList[Index]->OpCode);
	OptionList[Index]->OpLen = NTOHS (OptionList[Index]->OpLen);

	//
	// Get DNS server addresses from this reply packet.
	//
	if (OptionList[Index]->OpCode == DHCP6_TAG_DNS_SERVER) {

	if (((OptionList[Index]->OpLen & 0xf) != 0) \|\| (OptionList[Index]->OpLen == 0)) {
	Status = EFI_DEVICE_ERROR;
	gBS->FreePool (OptionList);
	return Status;
	}

	ServerCount = OptionList[Index]->OpLen/16;
	ServerList = AllocatePool (ServerCount * sizeof (EFI_IPv6_ADDRESS));
	if (ServerList == NULL) {
	gBS->FreePool (OptionList);
	return EFI_OUT_OF_RESOURCES;
	}

	for (Count=0; Count < ServerCount; Count++) {
	CopyMem (ServerList + Count, &OptionList[Index]->Data[16 * Count], sizeof (EFI_IPv6_ADDRESS));
	}

	*(DnsServerInfor->ServerCount) = ServerCount;
	DnsServerInfor->ServerList = ServerList;
	}
	}

	gBS->FreePool (OptionList);

	return Status;

	}

	/**
	Parse the DHCP ACK to get Dns4 server information.

	@param Instance The DNS instance.
	@param DnsServerCount Retrieved Dns4 server Ip count.
	@param DnsServerList Retrieved Dns4 server Ip list.

	@retval EFI_SUCCESS The Dns4 information is got from the DHCP ACK.
	@retval EFI_OUT_OF_RESOURCES Failed to allocate memory.
	@retval EFI_NO_MEDIA There was a media error.
	@retval Others Other errors as indicated.

	**/
	EFI_STATUS
	GetDns4ServerFromDhcp4 (
	IN DNS_INSTANCE *Instance,
	OUT UINT32 *DnsServerCount,
	OUT EFI_IPv4_ADDRESS **DnsServerList
	)
	{
	EFI_STATUS Status;
	EFI_HANDLE Image;
	EFI_HANDLE Controller;
	EFI_STATUS MediaStatus;
	EFI_HANDLE MnpChildHandle;
	EFI_MANAGED_NETWORK_PROTOCOL *Mnp;
	EFI_MANAGED_NETWORK_CONFIG_DATA MnpConfigData;
	EFI_HANDLE Dhcp4Handle;
	EFI_DHCP4_PROTOCOL *Dhcp4;
	EFI_IP4_CONFIG2_PROTOCOL *Ip4Config2;
	UINTN DataSize;
	VOID *Data;
	EFI_IP4_CONFIG2_INTERFACE_INFO *InterfaceInfo;
	EFI_DHCP4_PACKET SeedPacket;
	EFI_DHCP4_PACKET_OPTION *ParaList[2];
	DNS4_SERVER_INFOR DnsServerInfor;

	EFI_DHCP4_TRANSMIT_RECEIVE_TOKEN Token;
	BOOLEAN IsDone;
	UINTN Index;

	Image = Instance->Service->ImageHandle;
	Controller = Instance->Service->ControllerHandle;

	MnpChildHandle = NULL;
	Mnp = NULL;

	Dhcp4Handle = NULL;
	Dhcp4 = NULL;

	Ip4Config2 = NULL;
	DataSize = 0;
	Data = NULL;
	InterfaceInfo = NULL;

	ZeroMem ((UINT8 *) ParaList, sizeof (ParaList));

	ZeroMem (&MnpConfigData, sizeof (EFI_MANAGED_NETWORK_CONFIG_DATA));

	ZeroMem (&DnsServerInfor, sizeof (DNS4_SERVER_INFOR));

	ZeroMem (&Token, sizeof (EFI_DHCP4_TRANSMIT_RECEIVE_TOKEN));

	DnsServerInfor.ServerCount = DnsServerCount;

	IsDone = FALSE;

	//
	// Check media.
	//
	MediaStatus = EFI_SUCCESS;
	NetLibDetectMediaWaitTimeout (Controller, DNS_CHECK_MEDIA_GET_DHCP_WAITING_TIME, &MediaStatus);
	if (MediaStatus != EFI_SUCCESS) {
	return EFI_NO_MEDIA;
	}

	//
	// Create a Mnp child instance, get the protocol and config for it.
	//
	Status = NetLibCreateServiceChild (
	Controller,
	Image,
	&gEfiManagedNetworkServiceBindingProtocolGuid,
	&MnpChildHandle
	);
	if (EFI_ERROR (Status)) {
	return Status;
	}

	Status = gBS->OpenProtocol (
	MnpChildHandle,
	&gEfiManagedNetworkProtocolGuid,
	(VOID **) &Mnp,
	Image,
	Controller,
	EFI_OPEN_PROTOCOL_BY_DRIVER
	);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	MnpConfigData.ReceivedQueueTimeoutValue = 0;
	MnpConfigData.TransmitQueueTimeoutValue = 0;
	MnpConfigData.ProtocolTypeFilter = IP4_ETHER_PROTO;
	MnpConfigData.EnableUnicastReceive = TRUE;
	MnpConfigData.EnableMulticastReceive = TRUE;
	MnpConfigData.EnableBroadcastReceive = TRUE;
	MnpConfigData.EnablePromiscuousReceive = FALSE;
	MnpConfigData.FlushQueuesOnReset = TRUE;
	MnpConfigData.EnableReceiveTimestamps = FALSE;
	MnpConfigData.DisableBackgroundPolling = FALSE;

	Status = Mnp->Configure(Mnp, &MnpConfigData);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	//
	// Create a DHCP4 child instance and get the protocol.
	//
	Status = NetLibCreateServiceChild (
	Controller,
	Image,
	&gEfiDhcp4ServiceBindingProtocolGuid,
	&Dhcp4Handle
	);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	Status = gBS->OpenProtocol (
	Dhcp4Handle,
	&gEfiDhcp4ProtocolGuid,
	(VOID **) &Dhcp4,
	Image,
	Controller,
	EFI_OPEN_PROTOCOL_BY_DRIVER
	);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	//
	// Get Ip4Config2 instance info.
	//
	Status = gBS->HandleProtocol (Controller, &gEfiIp4Config2ProtocolGuid, (VOID **) &Ip4Config2);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	Status = Ip4Config2->GetData (Ip4Config2, Ip4Config2DataTypeInterfaceInfo, &DataSize, Data);
	if (EFI_ERROR (Status) && Status != EFI_BUFFER_TOO_SMALL) {
	goto ON_EXIT;
	}

	Data = AllocateZeroPool (DataSize);
	if (Data == NULL) {
	Status = EFI_OUT_OF_RESOURCES;
	goto ON_EXIT;
	}

	Status = Ip4Config2->GetData (Ip4Config2, Ip4Config2DataTypeInterfaceInfo, &DataSize, Data);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	InterfaceInfo = (EFI_IP4_CONFIG2_INTERFACE_INFO *)Data;

	//
	// Build required Token.
	//
	Status = gBS->CreateEvent (
	EVT_NOTIFY_SIGNAL,
	TPL_NOTIFY,
	DhcpCommonNotify,
	&IsDone,
	&Token.CompletionEvent
	);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	SetMem (&Token.RemoteAddress, sizeof (EFI_IPv4_ADDRESS), 0xff);

	Token.RemotePort = 67;

	Token.ListenPointCount = 1;

	Token.ListenPoints = AllocateZeroPool (Token.ListenPointCount * sizeof (EFI_DHCP4_LISTEN_POINT));
	if (Token.ListenPoints == NULL) {
	Status = EFI_OUT_OF_RESOURCES;
	goto ON_EXIT;
	}

	if (Instance->Dns4CfgData.UseDefaultSetting) {
	CopyMem (&(Token.ListenPoints[0].ListenAddress), &(InterfaceInfo->StationAddress), sizeof (EFI_IPv4_ADDRESS));
	CopyMem (&(Token.ListenPoints[0].SubnetMask), &(InterfaceInfo->SubnetMask), sizeof (EFI_IPv4_ADDRESS));
	} else {
	CopyMem (&(Token.ListenPoints[0].ListenAddress), &(Instance->Dns4CfgData.StationIp), sizeof (EFI_IPv4_ADDRESS));
	CopyMem (&(Token.ListenPoints[0].SubnetMask), &(Instance->Dns4CfgData.SubnetMask), sizeof (EFI_IPv4_ADDRESS));
	}

	Token.ListenPoints[0].ListenPort = 68;

	Token.TimeoutValue = DNS_TIME_TO_GETMAP;

	DnsInitSeedPacket (&SeedPacket, InterfaceInfo);

	ParaList[0] = AllocateZeroPool (sizeof (EFI_DHCP4_PACKET_OPTION));
	if (ParaList[0] == NULL) {
	Status = EFI_OUT_OF_RESOURCES;
	goto ON_EXIT;
	}

	ParaList[0]->OpCode = DHCP4_TAG_TYPE;
	ParaList[0]->Length = 1;
	ParaList[0]->Data[0] = DHCP4_MSG_REQUEST;

	ParaList[1] = AllocateZeroPool (sizeof (EFI_DHCP4_PACKET_OPTION));
	if (ParaList[1] == NULL) {
	Status = EFI_OUT_OF_RESOURCES;
	goto ON_EXIT;
	}

	ParaList[1]->OpCode = DHCP4_TAG_PARA_LIST;
	ParaList[1]->Length = 1;
	ParaList[1]->Data[0] = DHCP4_TAG_DNS_SERVER;

	Status = Dhcp4->Build (Dhcp4, &SeedPacket, 0, NULL, 2, ParaList, &Token.Packet);

	Token.Packet->Dhcp4.Header.Xid = HTONL(NET_RANDOM (NetRandomInitSeed ()));

	Token.Packet->Dhcp4.Header.Reserved = HTONS ((UINT16)0x8000);

	if (Instance->Dns4CfgData.UseDefaultSetting) {
	CopyMem (&(Token.Packet->Dhcp4.Header.ClientAddr), &(InterfaceInfo->StationAddress), sizeof (EFI_IPv4_ADDRESS));
	} else {
	CopyMem (&(Token.Packet->Dhcp4.Header.ClientAddr), &(Instance->Dns4CfgData.StationIp), sizeof (EFI_IPv4_ADDRESS));
	}

	CopyMem (Token.Packet->Dhcp4.Header.ClientHwAddr, &(InterfaceInfo->HwAddress), InterfaceInfo->HwAddressSize);

	Token.Packet->Dhcp4.Header.HwAddrLen = (UINT8)(InterfaceInfo->HwAddressSize);

	//
	// TransmitReceive Token
	//
	Status = Dhcp4->TransmitReceive (Dhcp4, &Token);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	//
	// Poll the packet
	//
	do {
	Status = Mnp->Poll (Mnp);
	} while (!IsDone);

	//
	// Parse the ACK to get required information if received done.
	//
	if (IsDone && !EFI_ERROR (Token.Status)) {
	for (Index = 0; Index < Token.ResponseCount; Index++) {
	Status = ParseDhcp4Ack (Dhcp4, &Token.ResponseList[Index], &DnsServerInfor);
	if (!EFI_ERROR (Status)) {
	break;
	}
	}

	*DnsServerList = DnsServerInfor.ServerList;
	} else {
	Status = Token.Status;
	}

	ON_EXIT:

	if (Data != NULL) {
	FreePool (Data);
	}

	for (Index = 0; Index < 2; Index++) {
	if (ParaList[Index] != NULL) {
	FreePool (ParaList[Index]);
	}
	}

	if (Token.ListenPoints) {
	FreePool (Token.ListenPoints);
	}

	if (Token.Packet) {
	FreePool (Token.Packet);
	}

	if (Token.ResponseList != NULL) {
	FreePool (Token.ResponseList);
	}

	if (Token.CompletionEvent != NULL) {
	gBS->CloseEvent (Token.CompletionEvent);
	}

	if (Dhcp4 != NULL) {
	Dhcp4->Stop (Dhcp4);
	Dhcp4->Configure (Dhcp4, NULL);

	gBS->CloseProtocol (
	Dhcp4Handle,
	&gEfiDhcp4ProtocolGuid,
	Image,
	Controller
	);
	}

	if (Dhcp4Handle != NULL) {
	NetLibDestroyServiceChild (
	Controller,
	Image,
	&gEfiDhcp4ServiceBindingProtocolGuid,
	Dhcp4Handle
	);
	}

	if (Mnp != NULL) {
	Mnp->Configure (Mnp, NULL);

	gBS->CloseProtocol (
	MnpChildHandle,
	&gEfiManagedNetworkProtocolGuid,
	Image,
	Controller
	);
	}

	NetLibDestroyServiceChild (
	Controller,
	Image,
	&gEfiManagedNetworkServiceBindingProtocolGuid,
	MnpChildHandle
	);

	return Status;
	}

	/**
	Parse the DHCP ACK to get Dns6 server information.

	@param Image The handle of the driver image.
	@param Controller The handle of the controller.
	@param DnsServerCount Retrieved Dns6 server Ip count.
	@param DnsServerList Retrieved Dns6 server Ip list.

	@retval EFI_SUCCESS The Dns6 information is got from the DHCP ACK.
	@retval EFI_OUT_OF_RESOURCES Failed to allocate memory.
	@retval EFI_NO_MEDIA There was a media error.
	@retval Others Other errors as indicated.

	**/
	EFI_STATUS
	GetDns6ServerFromDhcp6 (
	IN EFI_HANDLE Image,
	IN EFI_HANDLE Controller,
	OUT UINT32 *DnsServerCount,
	OUT EFI_IPv6_ADDRESS **DnsServerList
	)
	{
	EFI_HANDLE Dhcp6Handle;
	EFI_DHCP6_PROTOCOL *Dhcp6;
	EFI_STATUS Status;
	EFI_STATUS TimerStatus;
	EFI_DHCP6_PACKET_OPTION *Oro;
	EFI_DHCP6_RETRANSMISSION InfoReqReXmit;
	EFI_EVENT Timer;
	EFI_STATUS MediaStatus;
	DNS6_SERVER_INFOR DnsServerInfor;

	Dhcp6Handle = NULL;
	Dhcp6 = NULL;
	Oro = NULL;
	Timer = NULL;

	ZeroMem (&DnsServerInfor, sizeof (DNS6_SERVER_INFOR));

	DnsServerInfor.ServerCount = DnsServerCount;

	//
	// Check media status before doing DHCP.
	//
	MediaStatus = EFI_SUCCESS;
	NetLibDetectMediaWaitTimeout (Controller, DNS_CHECK_MEDIA_GET_DHCP_WAITING_TIME, &MediaStatus);
	if (MediaStatus != EFI_SUCCESS) {
	return EFI_NO_MEDIA;
	}

	//
	// Create a DHCP6 child instance and get the protocol.
	//
	Status = NetLibCreateServiceChild (
	Controller,
	Image,
	&gEfiDhcp6ServiceBindingProtocolGuid,
	&Dhcp6Handle
	);
	if (EFI_ERROR (Status)) {
	return Status;
	}

	Status = gBS->OpenProtocol (
	Dhcp6Handle,
	&gEfiDhcp6ProtocolGuid,
	(VOID **) &Dhcp6,
	Image,
	Controller,
	EFI_OPEN_PROTOCOL_BY_DRIVER
	);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	Oro = AllocateZeroPool (sizeof (EFI_DHCP6_PACKET_OPTION) + 1);
	if (Oro == NULL) {
	Status = EFI_OUT_OF_RESOURCES;
	goto ON_EXIT;
	}

	//
	// Ask the server to reply with DNS options.
	// All members in EFI_DHCP6_PACKET_OPTION are in network order.
	//
	Oro->OpCode = HTONS (DHCP6_TAG_DNS_REQUEST);
	Oro->OpLen = HTONS (2);
	Oro->Data[1] = DHCP6_TAG_DNS_SERVER;

	InfoReqReXmit.Irt = 4;
	InfoReqReXmit.Mrc = 1;
	InfoReqReXmit.Mrt = 10;
	InfoReqReXmit.Mrd = 30;

	Status = Dhcp6->InfoRequest (
	Dhcp6,
	TRUE,
	Oro,
	0,
	NULL,
	&InfoReqReXmit,
	NULL,
	ParseDhcp6Ack,
	&DnsServerInfor
	);
	if (Status == EFI_NO_MAPPING) {
	Status = gBS->CreateEvent (EVT_TIMER, TPL_CALLBACK, NULL, NULL, &Timer);
	if (EFI_ERROR (Status)) {
	goto ON_EXIT;
	}

	Status = gBS->SetTimer (
	Timer,
	TimerRelative,
	DNS_TIME_TO_GETMAP * TICKS_PER_SECOND
	);

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

	do {
	TimerStatus = gBS->CheckEvent (Timer);
	if (!EFI_ERROR (TimerStatus)) {
	Status = Dhcp6->InfoRequest (
	Dhcp6,
	TRUE,
	Oro,
	0,
	NULL,
	&InfoReqReXmit,
	NULL,
	ParseDhcp6Ack,
	&DnsServerInfor
	);
	}
	} while (TimerStatus == EFI_NOT_READY);
	}

	*DnsServerList = DnsServerInfor.ServerList;

	ON_EXIT:

	if (Oro != NULL) {
	FreePool (Oro);
	}

	if (Timer != NULL) {
	gBS->CloseEvent (Timer);
	}

	if (Dhcp6 != NULL) {
	gBS->CloseProtocol (
	Dhcp6Handle,
	&gEfiDhcp6ProtocolGuid,
	Image,
	Controller
	);
	}

	NetLibDestroyServiceChild (
	Controller,
	Image,
	&gEfiDhcp6ServiceBindingProtocolGuid,
	Dhcp6Handle
	);

	return Status;

	}