/** @file

Copyright (c) 2006 - 2007, Intel Corporation
All rights reserved. This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

Module Name:

  Udp4Impl.c

Abstract:

  The implementation of the Udp4 protocol.


**/


#include "Udp4Impl.h"

UINT16  mUdp4RandomPort;

STATIC
VOID
EFIAPI
Udp4CheckTimeout (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  );

STATIC
BOOLEAN
Udp4FindInstanceByPort (
  IN LIST_ENTRY        *InstanceList,
  IN EFI_IPv4_ADDRESS  *Address,
  IN UINT16            Port
  );

STATIC
VOID
Udp4DgramSent (
  IN EFI_STATUS  Status,
  IN VOID        *Context,
  IN VOID        *Sender,
  IN VOID        *NotifyData
  );

STATIC
VOID
Udp4DgramRcvd (
  IN EFI_STATUS            Status,
  IN ICMP_ERROR            IcmpError,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN NET_BUF               *Packet,
  IN VOID                  *Context
  );

STATIC
EFI_STATUS
Udp4CancelTokens (
  IN NET_MAP       *Map,
  IN NET_MAP_ITEM  *Item,
  IN VOID          *Arg OPTIONAL
  );

STATIC
BOOLEAN
Udp4MatchDgram (
  IN UDP4_INSTANCE_DATA     *Instance,
  IN EFI_UDP4_SESSION_DATA  *Udp4Session
  );

STATIC
VOID
EFIAPI
Udp4RecycleRxDataWrap (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  );

STATIC
UDP4_RXDATA_WRAP *
Udp4WrapRxData (
  IN UDP4_INSTANCE_DATA     *Instance,
  IN NET_BUF                *Packet,
  IN EFI_UDP4_RECEIVE_DATA  *RxData
  );

STATIC
UINTN
Udp4EnqueueDgram (
  IN UDP4_SERVICE_DATA      *Udp4Service,
  IN NET_BUF                *Packet,
  IN EFI_UDP4_RECEIVE_DATA  *RxData
  );

STATIC
VOID
Udp4DeliverDgram (
  IN UDP4_SERVICE_DATA  *Udp4Service
  );

STATIC
VOID
Udp4Demultiplex (
  IN UDP4_SERVICE_DATA     *Udp4Service,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN NET_BUF               *Packet
  );

STATIC
VOID
Udp4IcmpHandler (
  IN UDP4_SERVICE_DATA     *Udp4Service,
  IN ICMP_ERROR            IcmpError,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN NET_BUF               *Packet
  );

STATIC
VOID
Udp4SendPortUnreach (
  IN IP_IO                 *IpIo,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN VOID                  *Udp4Header
  );


/**
  Create the Udp service context data.

  @param  Udp4Service            Pointer to the UDP4_SERVICE_DATA.
  @param  ImageHandle            The image handle of this udp4 driver.
  @param  ControllerHandle       The controller handle this udp4 driver binds on.

  @retval EFI_SUCCESS            The udp4 service context data is created and
                                 initialized.
  @retval EFI_OUT_OF_RESOURCES   Cannot allocate memory.

**/
EFI_STATUS
Udp4CreateService (
  IN UDP4_SERVICE_DATA  *Udp4Service,
  IN EFI_HANDLE         ImageHandle,
  IN EFI_HANDLE         ControllerHandle
  )
{
  EFI_STATUS       Status;
  IP_IO_OPEN_DATA  OpenData;

  ZeroMem (Udp4Service, sizeof (UDP4_SERVICE_DATA));

  Udp4Service->Signature        = UDP4_SERVICE_DATA_SIGNATURE;
  Udp4Service->ServiceBinding   = mUdp4ServiceBinding;
  Udp4Service->ImageHandle      = ImageHandle;
  Udp4Service->ControllerHandle = ControllerHandle;
  Udp4Service->ChildrenNumber   = 0;

  InitializeListHead (&Udp4Service->ChildrenList);

  //
  // Create the IpIo for this service context.
  //
  Udp4Service->IpIo = IpIoCreate (ImageHandle, ControllerHandle);
  if (Udp4Service->IpIo == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // Set the OpenData used to open the IpIo.
  //
  CopyMem (&OpenData.IpConfigData, &mIpIoDefaultIpConfigData, sizeof (OpenData.IpConfigData));
  OpenData.IpConfigData.AcceptBroadcast = TRUE;
  OpenData.RcvdContext                  = (VOID *) Udp4Service;
  OpenData.SndContext                   = NULL;
  OpenData.PktRcvdNotify                = Udp4DgramRcvd;
  OpenData.PktSentNotify                = Udp4DgramSent;

  //
  // Configure and start the IpIo.
  //
  Status = IpIoOpen (Udp4Service->IpIo, &OpenData);
  if (EFI_ERROR (Status)) {
    goto ON_ERROR;
  }

  //
  // Create the event for Udp timeout checking.
  //
  Status = gBS->CreateEvent (
                  EVT_TIMER | EVT_NOTIFY_SIGNAL,
                  TPL_CALLBACK,
                  Udp4CheckTimeout,
                  Udp4Service,
                  &Udp4Service->TimeoutEvent
                  );
  if (EFI_ERROR (Status)) {
    goto ON_ERROR;
  }

  //
  // Start the timeout timer event.
  //
  Status = gBS->SetTimer (
                  Udp4Service->TimeoutEvent,
                  TimerPeriodic,
                  UDP4_TIMEOUT_INTERVAL
                  );
  if (EFI_ERROR (Status)) {
    goto ON_ERROR;
  }

  return EFI_SUCCESS;

ON_ERROR:

  if (Udp4Service->TimeoutEvent != NULL) {
    gBS->CloseEvent (Udp4Service->TimeoutEvent);
  }

  IpIoDestroy (Udp4Service->IpIo);

  return Status;
}


/**
  Clean the Udp service context data.

  @param  Udp4Service            Pointer to the UDP4_SERVICE_DATA.

  @return None.

**/
VOID
Udp4CleanService (
  IN UDP4_SERVICE_DATA  *Udp4Service
  )
{
  //
  // Cancel the TimeoutEvent timer.
  //
  gBS->SetTimer (Udp4Service->TimeoutEvent, TimerCancel, 0);

  //
  // Close the TimeoutEvent timer.
  //
  gBS->CloseEvent (Udp4Service->TimeoutEvent);

  //
  // Destroy the IpIo.
  //
  IpIoDestroy (Udp4Service->IpIo);
}


/**
  This function checks and timeouts the I/O datagrams holding by the corresponding
  service context.

  @param  Event                  The event this function registered to.
  @param  Conext                 The context data registered during the creation of
                                 the Event.

  @return None.

**/
STATIC
VOID
EFIAPI
Udp4CheckTimeout (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
  UDP4_SERVICE_DATA   *Udp4Service;
  LIST_ENTRY          *Entry;
  UDP4_INSTANCE_DATA  *Instance;
  LIST_ENTRY          *WrapEntry;
  LIST_ENTRY          *NextEntry;
  UDP4_RXDATA_WRAP    *Wrap;

  Udp4Service = (UDP4_SERVICE_DATA *) Context;
  NET_CHECK_SIGNATURE (Udp4Service, UDP4_SERVICE_DATA_SIGNATURE);

  NET_LIST_FOR_EACH (Entry, &Udp4Service->ChildrenList) {
    //
    // Iterate all the instances belonging to this service context.
    //
    Instance = NET_LIST_USER_STRUCT (Entry, UDP4_INSTANCE_DATA, Link);
    NET_CHECK_SIGNATURE (Instance, UDP4_INSTANCE_DATA_SIGNATURE);

    if (!Instance->Configured || (Instance->ConfigData.ReceiveTimeout == 0)) {
      //
      // Skip this instance if it's not configured or no receive timeout.
      //
      continue;
    }

    NET_LIST_FOR_EACH_SAFE (WrapEntry, NextEntry, &Instance->RcvdDgramQue) {
      //
      // Iterate all the rxdatas belonging to this udp instance.
      //
      Wrap = NET_LIST_USER_STRUCT (Entry, UDP4_RXDATA_WRAP, Link);

      if (Wrap->TimeoutTick <= UDP4_TIMEOUT_INTERVAL / 1000) {
        //
        // Remove this RxData if it timeouts.
        //
        Udp4RecycleRxDataWrap (NULL, (VOID *) Wrap);
      } else {
        Wrap->TimeoutTick -= UDP4_TIMEOUT_INTERVAL / 1000;
      }
    }
  }
}


/**
  This function intializes the new created udp instance.

  @param  Udp4Service            Pointer to the UDP4_SERVICE_DATA.
  @param  Instance               Pointer to the un-initialized UDP4_INSTANCE_DATA.

  @return None.

**/
VOID
Udp4InitInstance (
  IN UDP4_SERVICE_DATA   *Udp4Service,
  IN UDP4_INSTANCE_DATA  *Instance
  )
{
  //
  // Set the signature.
  //
  Instance->Signature = UDP4_INSTANCE_DATA_SIGNATURE;

  //
  // Init the lists.
  //
  InitializeListHead (&Instance->Link);
  InitializeListHead (&Instance->RcvdDgramQue);
  InitializeListHead (&Instance->DeliveredDgramQue);

  //
  // Init the NET_MAPs.
  //
  NetMapInit (&Instance->TxTokens);
  NetMapInit (&Instance->RxTokens);
  NetMapInit (&Instance->McastIps);

  //
  // Save the pointer to the UDP4_SERVICE_DATA, and initialize other members.
  //
  Instance->Udp4Service = Udp4Service;
  CopyMem (&Instance->Udp4Proto, &mUdp4Protocol, sizeof (Instance->Udp4Proto));
  Instance->IcmpError   = EFI_SUCCESS;
  Instance->Configured  = FALSE;
  Instance->IsNoMapping = FALSE;
  Instance->Destroyed   = FALSE;
}


/**
  This function cleans the udp instance.

  @param  Instance               Pointer to the UDP4_INSTANCE_DATA to clean.

  @return None.

**/
VOID
Udp4CleanInstance (
  IN UDP4_INSTANCE_DATA  *Instance
  )
{
  NetMapClean (&Instance->McastIps);
  NetMapClean (&Instance->RxTokens);
  NetMapClean (&Instance->TxTokens);
}


/**
  This function finds the udp instance by the specified <Address, Port> pair.

  @param  InstanceList           Pointer to the head of the list linking the udp
                                 instances.
  @param  Address                Pointer to the specified IPv4 address.
  @param  Port                   The udp port number.

  @return Is the specified <Address, Port> pair found or not.

**/
STATIC
BOOLEAN
Udp4FindInstanceByPort (
  IN LIST_ENTRY        *InstanceList,
  IN EFI_IPv4_ADDRESS  *Address,
  IN UINT16            Port
  )
{
  LIST_ENTRY            *Entry;
  UDP4_INSTANCE_DATA    *Instance;
  EFI_UDP4_CONFIG_DATA  *ConfigData;

  NET_LIST_FOR_EACH (Entry, InstanceList) {
    //
    // Iterate all the udp instances.
    //
    Instance   = NET_LIST_USER_STRUCT (Entry, UDP4_INSTANCE_DATA, Link);
    ConfigData = &Instance->ConfigData;

    if (!Instance->Configured || ConfigData->AcceptAnyPort) {
      //
      // If the instance is not configured or the configdata of the instance indicates
      // this instance accepts any port, skip it.
      //
      continue;
    }

    if (EFI_IP4_EQUAL (&ConfigData->StationAddress, Address) &&
      (ConfigData->StationPort == Port)) {
      //
      // if both the address and the port are the same, return TRUE.
      //
      return TRUE;
    }
  }

  //
  // return FALSE when matching fails.
  //
  return FALSE;
}


/**
  This function tries to bind the udp instance according to the configured port
  allocation stragety.

  @param  InstanceList           Pointer to the head of the list linking the udp
                                 instances.
  @param  ConfigData             Pointer to the ConfigData of the instance to be
                                 bound.

  @retval EFI_SUCCESS            The bound operation is completed successfully.
  @retval EFI_ACCESS_DENIED      The <Address, Port> specified by the ConfigData is
                                 already used by other instance.
  @retval EFI_OUT_OF_RESOURCES   No available port resources.

**/
EFI_STATUS
Udp4Bind (
  IN LIST_ENTRY            *InstanceList,
  IN EFI_UDP4_CONFIG_DATA  *ConfigData
  )
{
  EFI_IPv4_ADDRESS  *StationAddress;
  UINT16            StartPort;

  if (ConfigData->AcceptAnyPort) {
    return EFI_SUCCESS;
  }

  StationAddress = &ConfigData->StationAddress;

  if (ConfigData->StationPort != 0) {

    if (!ConfigData->AllowDuplicatePort &&
      Udp4FindInstanceByPort (InstanceList, StationAddress, ConfigData->StationPort)) {
      //
      // Do not allow duplicate port and the port is already used by other instance.
      //
      return EFI_ACCESS_DENIED;
    }
  } else {
    //
    // select a random port for this instance;
    //

    if (ConfigData->AllowDuplicatePort) {
      //
      // Just pick up the random port if the instance allows duplicate port.
      //
      ConfigData->StationPort = mUdp4RandomPort;
    } else {

      StartPort = mUdp4RandomPort;

      while (Udp4FindInstanceByPort(InstanceList, StationAddress, mUdp4RandomPort)) {

        mUdp4RandomPort++;
        if (mUdp4RandomPort == 0) {
          mUdp4RandomPort = UDP4_PORT_KNOWN;
        }

        if (mUdp4RandomPort == StartPort) {
          //
          // No available port.
          //
          return EFI_OUT_OF_RESOURCES;
        }
      }

      ConfigData->StationPort = mUdp4RandomPort;
    }

    mUdp4RandomPort++;
    if (mUdp4RandomPort == 0) {
      mUdp4RandomPort = UDP4_PORT_KNOWN;
    }
  }

  return EFI_SUCCESS;
}


/**
  This function is used to check whether the NewConfigData has any un-reconfigurable
  parameters changed compared to the OldConfigData.

  @param  OldConfigData          Pointer to the current ConfigData the udp instance
                                 uses.
  @param  NewConfigData          Pointer to the new ConfigData.

  @return The instance is reconfigurable or not according to the NewConfigData.

**/
BOOLEAN
Udp4IsReconfigurable (
  IN EFI_UDP4_CONFIG_DATA  *OldConfigData,
  IN EFI_UDP4_CONFIG_DATA  *NewConfigData
  )
{
  if ((NewConfigData->AcceptAnyPort != OldConfigData->AcceptAnyPort) ||
    (NewConfigData->AcceptBroadcast != OldConfigData->AcceptBroadcast) ||
    (NewConfigData->AcceptPromiscuous != OldConfigData->AcceptPromiscuous) ||
    (NewConfigData->AllowDuplicatePort != OldConfigData->AllowDuplicatePort)) {
    //
    // The receiving filter parameters cannot be changed.
    //
    return FALSE;
  }

  if ((!NewConfigData->AcceptAnyPort) &&
    (NewConfigData->StationPort != OldConfigData->StationPort)) {
    //
    // The port is not changeable.
    //
    return FALSE;
  }

  if (!NewConfigData->AcceptPromiscuous) {

    if (NewConfigData->UseDefaultAddress != OldConfigData->UseDefaultAddress) {
      //
      // The NewConfigData differs to the old one on the UseDefaultAddress.
      //
      return FALSE;
    }

    if (!NewConfigData->UseDefaultAddress &&
      (!EFI_IP4_EQUAL (&NewConfigData->StationAddress, &OldConfigData->StationAddress) ||
      !EFI_IP4_EQUAL (&NewConfigData->SubnetMask, &OldConfigData->SubnetMask))) {
      //
      // If the instance doesn't use the default address, and the new address or
      // new subnet mask is different from the old values.
      //
      return FALSE;
    }
  }

  if (!EFI_IP4_EQUAL (&NewConfigData->RemoteAddress, &OldConfigData->RemoteAddress)) {
    //
    // The remoteaddress is not the same.
    //
    return FALSE;
  }

  if (!EFI_IP4_EQUAL (&NewConfigData->RemoteAddress, &mZeroIp4Addr) && (NewConfigData->RemotePort != OldConfigData->RemotePort)) {
    //
    // The RemotePort differs if it's designated in the configdata.
    //
    return FALSE;
  }

  //
  // All checks pass, return TRUE.
  //
  return TRUE;
}


/**
  This function builds the Ip4 configdata from the Udp4ConfigData.

  @param  Udp4ConfigData         Pointer to the EFI_UDP4_CONFIG_DATA.
  @param  Ip4ConfigData          Pointer to the EFI_IP4_CONFIG_DATA.

  @return None.

**/
VOID
Udp4BuildIp4ConfigData (
  IN EFI_UDP4_CONFIG_DATA  *Udp4ConfigData,
  IN EFI_IP4_CONFIG_DATA   *Ip4ConfigData
  )
{
  CopyMem (Ip4ConfigData, &mIpIoDefaultIpConfigData, sizeof (*Ip4ConfigData));

  Ip4ConfigData->DefaultProtocol   = EFI_IP_PROTO_UDP;
  Ip4ConfigData->AcceptBroadcast   = Udp4ConfigData->AcceptBroadcast;
  Ip4ConfigData->AcceptPromiscuous = Udp4ConfigData->AcceptPromiscuous;
  Ip4ConfigData->UseDefaultAddress = Udp4ConfigData->UseDefaultAddress;
  CopyMem (&Ip4ConfigData->StationAddress, &Udp4ConfigData->StationAddress, sizeof (EFI_IPv4_ADDRESS));
  CopyMem (&Ip4ConfigData->SubnetMask, &Udp4ConfigData->SubnetMask, sizeof (EFI_IPv4_ADDRESS));

  //
  // use the -1 magic number to disable the receiving process of the ip instance.
  //
  Ip4ConfigData->ReceiveTimeout    = (UINT32) (-1);
}


/**
  This function validates the TxToken, it returns the error code according to the spec.

  @param  Instance               Pointer to the udp instance context data.
  @param  TxToken                Pointer to the token to be checked.

  @retval EFI_SUCCESS            The TxToken is valid.
  @retval EFI_INVALID_PARAMETER  One or more of the following are TRUE: This is
                                 NULL. Token is NULL. Token.Event is NULL.
                                 Token.Packet.TxData is NULL.
                                 Token.Packet.TxData.FragmentCount is zero.
                                 Token.Packet.TxData.DataLength is not equal to the
                                 sum of fragment lengths. One or more of the
                                 Token.Packet.TxData.FragmentTable[].
                                 FragmentLength fields is zero. One or more of the
                                 Token.Packet.TxData.FragmentTable[].
                                 FragmentBuffer fields is NULL.
                                 Token.Packet.TxData. GatewayAddress is not a
                                 unicast IPv4 address if it is not NULL. One or
                                 more IPv4 addresses in Token.Packet.TxData.
                                 UdpSessionData are not valid unicast IPv4
                                 addresses if the UdpSessionData is not NULL.
  @retval EFI_BAD_BUFFER_SIZE    The data length is greater than the maximum UDP
                                 packet size.

**/
EFI_STATUS
Udp4ValidateTxToken (
  IN UDP4_INSTANCE_DATA         *Instance,
  IN EFI_UDP4_COMPLETION_TOKEN  *TxToken
  )
{
  EFI_UDP4_TRANSMIT_DATA  *TxData;
  UINT32                  Index;
  UINT32                  TotalLen;
  EFI_UDP4_CONFIG_DATA    *ConfigData;
  EFI_UDP4_SESSION_DATA   *UdpSessionData;
  IP4_ADDR                SourceAddress;
  IP4_ADDR                GatewayAddress;

  if (TxToken->Event == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  TxData = TxToken->Packet.TxData;

  if ((TxData == NULL) || (TxData->FragmentCount == 0)) {
    return EFI_INVALID_PARAMETER;
  }

  TotalLen = 0;
  for (Index = 0; Index < TxData->FragmentCount; Index++) {

    if ((TxData->FragmentTable[Index].FragmentBuffer == NULL) ||
      (TxData->FragmentTable[Index].FragmentLength == 0)) {
      //
      // if the FragmentBuffer is NULL or the FragmentLeng is zero.
      //
      return EFI_INVALID_PARAMETER;
    }

    TotalLen += TxData->FragmentTable[Index].FragmentLength;
  }

  if (TotalLen != TxData->DataLength) {
    //
    // The TotalLen calculated by adding all the FragmentLeng doesn't equal to the
    // DataLength.
    //
    return EFI_INVALID_PARAMETER;
  }

  if (TxData->GatewayAddress != NULL) {
    CopyMem (&GatewayAddress, TxData->GatewayAddress, sizeof (IP4_ADDR));

    if (!Ip4IsUnicast (NTOHL (GatewayAddress), 0)) {
      //
      // The specified GatewayAddress is not a unicast IPv4 address while it's not 0.
      //
      return EFI_INVALID_PARAMETER;
    }
  }

  ConfigData     = &Instance->ConfigData;
  UdpSessionData = TxData->UdpSessionData;

  if (UdpSessionData != NULL) {

    CopyMem (&SourceAddress, &UdpSessionData->SourceAddress, sizeof (IP4_ADDR));

    if ((SourceAddress != 0) && !Ip4IsUnicast (HTONL (SourceAddress), 0)) {
      //
      // Check whether SourceAddress is a valid IPv4 address in case it's not zero.
      // The configured station address is used if SourceAddress is zero.
      //
      return EFI_INVALID_PARAMETER;
    }

    if ((UdpSessionData->DestinationPort == 0) && (ConfigData->RemotePort == 0)) {
      //
      // Ambiguous, no avalaible DestinationPort for this token.
      //
      return EFI_INVALID_PARAMETER;
    }

    if (EFI_IP4_EQUAL (&UdpSessionData->DestinationAddress, &mZeroIp4Addr)) {
      //
      // The DestinationAddress specified in the UdpSessionData is 0.
      //
      return EFI_INVALID_PARAMETER;
    }
  } else if (EFI_IP4_EQUAL (&ConfigData->RemoteAddress, &mZeroIp4Addr)) {
    //
    // the configured RemoteAddress is all zero, and the user doens't override the
    // destination address.
    //
    return EFI_INVALID_PARAMETER;
  }

  if (TxData->DataLength > UDP4_MAX_DATA_SIZE) {
    return EFI_BAD_BUFFER_SIZE;
  }

  return EFI_SUCCESS;
}


/**
  This function checks whether the specified Token duplicates with the one in the Map.

  @param  Map                    Pointer to the NET_MAP.
  @param  Item                   Pointer to the NET_MAP_ITEM contain the pointer to
                                 the Token.
  @param  Context                Pointer to the Token to be checked.

  @retval EFI_SUCCESS            The Token specified by Context differs from the
                                 one in the Item.
  @retval EFI_ACCESS_DENIED      The Token duplicates with the one in the Item.

**/
EFI_STATUS
Udp4TokenExist (
  IN NET_MAP       *Map,
  IN NET_MAP_ITEM  *Item,
  IN VOID          *Context
  )
{
  EFI_UDP4_COMPLETION_TOKEN  *Token;
  EFI_UDP4_COMPLETION_TOKEN  *TokenInItem;

  Token       = (EFI_UDP4_COMPLETION_TOKEN*) Context;
  TokenInItem = (EFI_UDP4_COMPLETION_TOKEN*) Item->Key;

  if ((Token == TokenInItem) || (Token->Event == TokenInItem->Event)) {
    //
    // The Token duplicates with the TokenInItem in case either the two pointers are the
    // same or the Events of these two tokens are the same.
    //
    return EFI_ACCESS_DENIED;
  }

  return EFI_SUCCESS;
}


/**
  This function calculates the checksum for the Packet, utilizing the pre-calculated
  pseudo HeadSum to reduce some overhead.

  @param  Packet                 Pointer to the NET_BUF contains the udp datagram.
  @param  HeadSum                Checksum of the pseudo header execpt the length
                                 field.

  @return The 16-bit checksum of this udp datagram.

**/
UINT16
Udp4Checksum (
  IN NET_BUF *Packet,
  IN UINT16  HeadSum
  )
{
  UINT16  Checksum;

  Checksum  = NetbufChecksum (Packet);
  Checksum  = NetAddChecksum (Checksum, HeadSum);

  Checksum  = NetAddChecksum (Checksum, HTONS ((UINT16) Packet->TotalSize));

  return (UINT16) ~Checksum;
}


/**
  This function removes the specified Token from the TokenMap.

  @param  TokenMap               Pointer to the NET_MAP containing the tokens.
  @param  Token                  Pointer to the Token to be removed.

  @retval EFI_SUCCESS            The specified Token is removed from the TokenMap.
  @retval EFI_NOT_FOUND          The specified Token is not found in the TokenMap.

**/
EFI_STATUS
Udp4RemoveToken (
  IN NET_MAP                    *TokenMap,
  IN EFI_UDP4_COMPLETION_TOKEN  *Token
  )
{
  NET_MAP_ITEM  *Item;

  //
  // Find the Token first.
  //
  Item = NetMapFindKey (TokenMap, (VOID *) Token);

  if (Item != NULL) {
    //
    // Remove the token if it's found in the map.
    //
    NetMapRemoveItem (TokenMap, Item, NULL);

    return EFI_SUCCESS;
  }

  return EFI_NOT_FOUND;
}


/**
  This function is the packet transmitting notify function registered to the IpIo
  interface. It's called to signal the udp TxToken when IpIo layer completes the
  transmitting of the udp datagram.

  @param  Status                 The completion status of the output udp datagram.
  @param  Context                Pointer to the context data.
  @param  Sender                 Pointer to the Ip sender of the udp datagram.
  @param  NotifyData             Pointer to the notify data.

  @return None.

**/
STATIC
VOID
Udp4DgramSent (
  IN EFI_STATUS  Status,
  IN VOID        *Context,
  IN VOID        *Sender,
  IN VOID        *NotifyData
  )
{
  UDP4_INSTANCE_DATA         *Instance;
  EFI_UDP4_COMPLETION_TOKEN  *Token;

  Instance = (UDP4_INSTANCE_DATA *) Context;
  Token    = (EFI_UDP4_COMPLETION_TOKEN *) NotifyData;

  if (Udp4RemoveToken (&Instance->TxTokens, Token) == EFI_SUCCESS) {
    //
    // The token may be cancelled. Only signal it if the remove operation succeeds.
    //
    Token->Status = Status;
    gBS->SignalEvent (Token->Event);
    NetLibDispatchDpc ();
  }
}


/**
  This function processes the received datagram passed up by the IpIo layer.

  @param  Status                 The status of this udp datagram.
  @param  IcmpError              The IcmpError code, only available when Status is
                                 EFI_ICMP_ERROR.
  @param  NetSession             Pointer to the EFI_NET_SESSION_DATA.
  @param  Packet                 Pointer to the NET_BUF containing the received udp
                                 datagram.
  @param  Context                Pointer to the context data.

  @return None.

**/
STATIC
VOID
Udp4DgramRcvd (
  IN EFI_STATUS            Status,
  IN ICMP_ERROR            IcmpError,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN NET_BUF               *Packet,
  IN VOID                  *Context
  )
{
  NET_CHECK_SIGNATURE (Packet, NET_BUF_SIGNATURE);

  //
  // IpIo only passes received packets with Status EFI_SUCCESS or EFI_ICMP_ERROR.
  //
  if (Status == EFI_SUCCESS) {
    //
    // Demultiplex the received datagram.
    //
    Udp4Demultiplex ((UDP4_SERVICE_DATA *) Context, NetSession, Packet);
  } else {
    //
    // Handle the ICMP_ERROR packet.
    //
    Udp4IcmpHandler ((UDP4_SERVICE_DATA *) Context, IcmpError, NetSession, Packet);
  }

  //
  // Dispatch the DPC queued by the NotifyFunction of the rx token's events
  // which are signaled with received data.
  //
  NetLibDispatchDpc ();
}


/**
  This function removes the multicast group specified by Arg from the Map.

  @param  Map                    Pointer to the NET_MAP.
  @param  Item                   Pointer to the NET_MAP_ITEM.
  @param  Arg                    Pointer to the Arg, it's the pointer to a
                                 multicast IPv4 Address.

  @retval EFI_SUCCESS            The multicast address is removed.
  @retval EFI_ABORTED            The specified multicast address is removed and the
                                 Arg is not NULL.

**/
EFI_STATUS
Udp4LeaveGroup (
  IN NET_MAP       *Map,
  IN NET_MAP_ITEM  *Item,
  IN VOID          *Arg OPTIONAL
  )
{
  EFI_IPv4_ADDRESS  *McastIp;

  McastIp = Arg;

  if ((McastIp != NULL) && (!EFI_IP4_EQUAL (McastIp, &(Item->Key)))) {
    //
    // McastIp is not NULL and the multicast address contained in the Item
    // is not the same as McastIp.
    //
    return EFI_SUCCESS;
  }

  //
  // Remove this Item.
  //
  NetMapRemoveItem (Map, Item, NULL);

  if (McastIp != NULL) {
    //
    // Return EFI_ABORTED in case McastIp is not NULL to terminate the iteration.
    //
    return EFI_ABORTED;
  }

  return EFI_SUCCESS;
}


/**
  This function cancle the token specified by Arg in the Map.

  @param  Map                    Pointer to the NET_MAP.
  @param  Item                   Pointer to the NET_MAP_ITEM.
  @param  Arg                    Pointer to the token to be cancelled, if NULL, all
                                 the tokens in this Map will be cancelled.

  @retval EFI_SUCCESS            The token is cancelled if Arg is NULL or the token
                                 is not the same as that in the Item if Arg is not
                                 NULL.
  @retval EFI_ABORTED            Arg is not NULL, and the token specified by Arg is
                                 cancelled.

**/
STATIC
EFI_STATUS
Udp4CancelTokens (
  IN NET_MAP       *Map,
  IN NET_MAP_ITEM  *Item,
  IN VOID          *Arg OPTIONAL
  )
{
  EFI_UDP4_COMPLETION_TOKEN  *TokenToCancel;
  NET_BUF                    *Packet;
  IP_IO                      *IpIo;

  if ((Arg != NULL) && (Item->Key != Arg)) {
    return EFI_SUCCESS;
  }

  if (Item->Value != NULL) {
    //
    // If the token is a transmit token, the corresponding Packet is recorded in
    // Item->Value, invoke IpIo to cancel this packet first. The IpIoCancelTxToken
    // will invoke Udp4DgramSent, the token will be signaled and this Item will
    // be removed from the Map there.
    //
    Packet = (NET_BUF *) (Item->Value);
    IpIo   = (IP_IO *) (*((UINTN *) &Packet->ProtoData[0]));

    IpIoCancelTxToken (IpIo, Packet);
  } else {
    //
    // The token is a receive token. Abort it and remove it from the Map.
    //
    TokenToCancel = (EFI_UDP4_COMPLETION_TOKEN *) Item->Key;
    NetMapRemoveItem (Map, Item, NULL);

    TokenToCancel->Status = EFI_ABORTED;
    gBS->SignalEvent (TokenToCancel->Event);
  }

  if (Arg != NULL) {
    return EFI_ABORTED;
  }

  return EFI_SUCCESS;
}


/**
  This function removes all the Wrap datas in the RcvdDgramQue.

  @param  RcvdDgramQue           Pointer to the list containing all the Wrap datas.

  @return None.

**/
VOID
Udp4FlushRcvdDgram (
  IN UDP4_INSTANCE_DATA  *Instance
  )
{
  UDP4_RXDATA_WRAP  *Wrap;

  while (!IsListEmpty (&Instance->RcvdDgramQue)) {
    //
    // Iterate all the Wraps in the RcvdDgramQue.
    //
    Wrap = NET_LIST_HEAD (&Instance->RcvdDgramQue, UDP4_RXDATA_WRAP, Link);

    //
    // The Wrap will be removed from the RcvdDgramQue by this function call.
    //
    Udp4RecycleRxDataWrap (NULL, (VOID *) Wrap);
  }
}



/**

  @param  Instance               Pointer to the udp instance context data.
  @param  Token                  Pointer to the token to be canceled, if NULL, all
                                 tokens in this instance will be cancelled.

  @retval EFI_SUCCESS            The Token is cancelled.
  @retval EFI_NOT_FOUND          The Token is not found.

**/
EFI_STATUS
Udp4InstanceCancelToken (
  IN UDP4_INSTANCE_DATA         *Instance,
  IN EFI_UDP4_COMPLETION_TOKEN  *Token OPTIONAL
  )
{
  EFI_STATUS  Status;

  //
  // Cancle this token from the TxTokens map.
  //
  Status = NetMapIterate (&Instance->TxTokens, Udp4CancelTokens, Token);

  if ((Token != NULL) && (Status == EFI_ABORTED)) {
    //
    // If Token isn't NULL and Status is EFI_ABORTED, the token is cancelled from
    // the TxTokens, just return success.
    //
    return EFI_SUCCESS;
  }

  //
  // Try to cancel this token from the RxTokens map in condition either the Token
  // is NULL or the specified Token is not in TxTokens.
  //
  Status = NetMapIterate (&Instance->RxTokens, Udp4CancelTokens, Token);

  if ((Token != NULL) && (Status == EFI_SUCCESS)) {
    //
    // If Token isn't NULL and Status is EFI_SUCCESS, the token is neither in the
    // TxTokens nor the RxTokens, or say, it's not found.
    //
    return EFI_NOT_FOUND;
  }

  ASSERT ((Token != NULL) || ((0 == NetMapGetCount (&Instance->TxTokens))
    && (0 == NetMapGetCount (&Instance->RxTokens))));

  return EFI_SUCCESS;
}


/**
  This function matches the received udp datagram with the Instance.

  @param  Instance               Pointer to the udp instance context data.
  @param  Udp4Session            Pointer to the EFI_UDP4_SESSION_DATA abstracted
                                 from the received udp datagram.

  @return The udp datagram matches the receiving requirments of the Instance or not.

**/
STATIC
BOOLEAN
Udp4MatchDgram (
  IN UDP4_INSTANCE_DATA     *Instance,
  IN EFI_UDP4_SESSION_DATA  *Udp4Session
  )
{
  EFI_UDP4_CONFIG_DATA  *ConfigData;
  IP4_ADDR              Destination;

  ConfigData = &Instance->ConfigData;

  if (ConfigData->AcceptPromiscuous) {
    //
    // Always matches if this instance is in the promiscuous state.
    //
    return TRUE;
  }

  if ((!ConfigData->AcceptAnyPort && (Udp4Session->DestinationPort != ConfigData->StationPort)) ||
    ((ConfigData->RemotePort != 0) && (Udp4Session->SourcePort != ConfigData->RemotePort))) {
    //
    // The local port or the remote port doesn't match.
    //
    return FALSE;
  }

  if (!EFI_IP4_EQUAL (&ConfigData->RemoteAddress, &mZeroIp4Addr) &&
    !EFI_IP4_EQUAL (&ConfigData->RemoteAddress, &Udp4Session->SourceAddress)) {
    //
    // This datagram doesn't come from the instance's specified sender.
    //
    return FALSE;
  }

  if (EFI_IP4_EQUAL (&ConfigData->StationAddress, &mZeroIp4Addr) ||
    EFI_IP4_EQUAL (&Udp4Session->DestinationAddress, &ConfigData->StationAddress)) {
    //
    // The instance is configured to receive datagrams destinated to any station IP or
    // the destination address of this datagram matches the configured station IP.
    //
    return TRUE;
  }

  CopyMem (&Destination, &Udp4Session->DestinationAddress, sizeof (IP4_ADDR));

  if (IP4_IS_LOCAL_BROADCAST (Destination) && ConfigData->AcceptBroadcast) {
    //
    // The instance is configured to receive broadcast and this is a broadcast packet.
    //
    return TRUE;
  }

  if (IP4_IS_MULTICAST (NTOHL (Destination)) &&
    (NULL != NetMapFindKey (&Instance->McastIps, (VOID *) (UINTN) Destination))) {
    //
    // It's a multicast packet and the multicast address is accepted by this instance.
    //
    return TRUE;
  }

  return FALSE;
}


/**
  This function removes the Wrap specified by Context and release relevant resources.

  @param  Event                  The Event this notify function registered to.
  @param  Context                Pointer to the context data.

  @return None.

**/
STATIC
VOID
EFIAPI
Udp4RecycleRxDataWrap (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
  UDP4_RXDATA_WRAP  *Wrap;

  Wrap = (UDP4_RXDATA_WRAP *) Context;

  //
  // Remove the Wrap from the list it belongs to.
  //
  RemoveEntryList (&Wrap->Link);

  //
  // Free the Packet associated with this Wrap.
  //
  NetbufFree (Wrap->Packet);

  //
  // Close the event.
  //
  gBS->CloseEvent (Wrap->RxData.RecycleSignal);

  gBS->FreePool (Wrap);
}


/**
  This function wraps the Packet and the RxData.

  @param  Instance               Pointer to the instance context data.
  @param  Packet                 Pointer to the buffer containing the received
                                 datagram.
  @param  RxData                 Pointer to the EFI_UDP4_RECEIVE_DATA of this
                                 datagram.

  @return Pointer to the structure wrapping the RxData and the Packet.

**/
STATIC
UDP4_RXDATA_WRAP *
Udp4WrapRxData (
  IN UDP4_INSTANCE_DATA     *Instance,
  IN NET_BUF                *Packet,
  IN EFI_UDP4_RECEIVE_DATA  *RxData
  )
{
  EFI_STATUS            Status;
  UDP4_RXDATA_WRAP      *Wrap;

  //
  // Allocate buffer for the Wrap.
  //
  Wrap = AllocatePool (sizeof (UDP4_RXDATA_WRAP) +
         (Packet->BlockOpNum - 1) * sizeof (EFI_UDP4_FRAGMENT_DATA));
  if (Wrap == NULL) {
    return NULL;
  }

  InitializeListHead (&Wrap->Link);

  CopyMem (&Wrap->RxData, RxData, sizeof (Wrap->RxData));

  //
  // Create the Recycle event.
  //
  Status = gBS->CreateEvent (
                  EVT_NOTIFY_SIGNAL,
                  TPL_NOTIFY,
                  Udp4RecycleRxDataWrap,
                  Wrap,
                  &Wrap->RxData.RecycleSignal
                  );
  if (EFI_ERROR (Status)) {
    gBS->FreePool (Wrap);
    return NULL;
  }

  Wrap->Packet      = Packet;
  Wrap->TimeoutTick = Instance->ConfigData.ReceiveTimeout;

  return Wrap;
}


/**
  This function enqueues the received datagram into the instances' receiving queues.

  @param  Udp4Service            Pointer to the udp service context data.
  @param  Packet                 Pointer to the buffer containing the received
                                 datagram.
  @param  RxData                 Pointer to the EFI_UDP4_RECEIVE_DATA of this
                                 datagram.

  @return The times this datagram is enqueued.

**/
STATIC
UINTN
Udp4EnqueueDgram (
  IN UDP4_SERVICE_DATA      *Udp4Service,
  IN NET_BUF                *Packet,
  IN EFI_UDP4_RECEIVE_DATA  *RxData
  )
{
  LIST_ENTRY          *Entry;
  UDP4_INSTANCE_DATA  *Instance;
  UDP4_RXDATA_WRAP    *Wrap;
  UINTN               Enqueued;

  Enqueued = 0;

  NET_LIST_FOR_EACH (Entry, &Udp4Service->ChildrenList) {
    //
    // Iterate the instances.
    //
    Instance = NET_LIST_USER_STRUCT (Entry, UDP4_INSTANCE_DATA, Link);

    if (!Instance->Configured) {
      continue;
    }

    if (Udp4MatchDgram (Instance, &RxData->UdpSession)) {
      //
      // Wrap the RxData and put this Wrap into the instances RcvdDgramQue.
      //
      Wrap = Udp4WrapRxData (Instance, Packet, RxData);
      if (Wrap == NULL) {
        continue;
      }

      NET_GET_REF (Packet);

      InsertTailList (&Instance->RcvdDgramQue, &Wrap->Link);

      Enqueued++;
    }
  }

  return Enqueued;
}


/**
  This function delivers the received datagrams for the specified instance.

  @param  Instance               Pointer to the instance context data.

  @return None.

**/
VOID
Udp4InstanceDeliverDgram (
  IN UDP4_INSTANCE_DATA  *Instance
  )
{
  UDP4_RXDATA_WRAP           *Wrap;
  EFI_UDP4_COMPLETION_TOKEN  *Token;
  NET_BUF                    *Dup;
  EFI_UDP4_RECEIVE_DATA      *RxData;
  EFI_TPL                    OldTpl;

  if (!IsListEmpty (&Instance->RcvdDgramQue) &&
    !NetMapIsEmpty (&Instance->RxTokens)) {

    Wrap = NET_LIST_HEAD (&Instance->RcvdDgramQue, UDP4_RXDATA_WRAP, Link);

    if (NET_BUF_SHARED (Wrap->Packet)) {
      //
      // Duplicate the Packet if it is shared between instances.
      //
      Dup = NetbufDuplicate (Wrap->Packet, NULL, 0);
      if (Dup == NULL) {
        return;
      }

      NetbufFree (Wrap->Packet);

      Wrap->Packet = Dup;
    } 

    NetListRemoveHead (&Instance->RcvdDgramQue);

    Token = (EFI_UDP4_COMPLETION_TOKEN *) NetMapRemoveHead (&Instance->RxTokens, NULL);

    //
    // Build the FragmentTable and set the FragmentCount in RxData.
    //
    RxData                = &Wrap->RxData;
    RxData->FragmentCount = Wrap->Packet->BlockOpNum;

    NetbufBuildExt (
      Wrap->Packet,
      (NET_FRAGMENT *) RxData->FragmentTable,
      &RxData->FragmentCount
      );

    Token->Status        = EFI_SUCCESS;
    Token->Packet.RxData = &Wrap->RxData;

    OldTpl = gBS->RaiseTPL (TPL_NOTIFY);
    InsertTailList (&Instance->DeliveredDgramQue, &Wrap->Link);
    gBS->RestoreTPL (OldTpl);

    gBS->SignalEvent (Token->Event);
  }
}


/**
  This function delivers the datagrams enqueued in the instances.

  @param  Udp4Service            Pointer to the udp service context data.

  @return None.

**/
STATIC
VOID
Udp4DeliverDgram (
  IN UDP4_SERVICE_DATA  *Udp4Service
  )
{
  LIST_ENTRY          *Entry;
  UDP4_INSTANCE_DATA  *Instance;

  NET_LIST_FOR_EACH (Entry, &Udp4Service->ChildrenList) {
    //
    // Iterate the instances.
    //
    Instance = NET_LIST_USER_STRUCT (Entry, UDP4_INSTANCE_DATA, Link);

    if (!Instance->Configured) {
      continue;
    }

    //
    // Deliver the datagrams of this instance.
    //
    Udp4InstanceDeliverDgram (Instance);
  }
}


/**
  This function demultiplexes the received udp datagram to the apropriate instances.

  @param  Udp4Service            Pointer to the udp service context data.
  @param  NetSession             Pointer to the EFI_NET_SESSION_DATA abstrated from
                                 the received datagram.
  @param  Packet                 Pointer to the buffer containing the received udp
                                 datagram.

  @return None.

**/
STATIC
VOID
Udp4Demultiplex (
  IN UDP4_SERVICE_DATA     *Udp4Service,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN NET_BUF               *Packet
  )
{
  EFI_UDP4_HEADER        *Udp4Header;
  UINT16                 HeadSum;
  EFI_UDP4_RECEIVE_DATA  RxData;
  EFI_UDP4_SESSION_DATA  *Udp4Session;
  UINTN                  Enqueued;

  //
  // Get the datagram header from the packet buffer.
  //
  Udp4Header = (EFI_UDP4_HEADER *) NetbufGetByte (Packet, 0, NULL);

  if (Udp4Header->Checksum != 0) {
    //
    // check the checksum.
    //
    HeadSum = NetPseudoHeadChecksum (
                NetSession->Source,
                NetSession->Dest,
                EFI_IP_PROTO_UDP,
                0
                );

    if (Udp4Checksum (Packet, HeadSum) != 0) {
      //
      // Wrong checksum.
      //
      return;
    }
  }

  gRT->GetTime (&RxData.TimeStamp, NULL);

  Udp4Session                  = &RxData.UdpSession;
  Udp4Session->SourcePort      = NTOHS (Udp4Header->SrcPort);
  Udp4Session->DestinationPort = NTOHS (Udp4Header->DstPort);

  CopyMem (&Udp4Session->SourceAddress, &NetSession->Source, sizeof (EFI_IPv4_ADDRESS));
  CopyMem (&Udp4Session->DestinationAddress, &NetSession->Dest, sizeof (EFI_IPv4_ADDRESS));

  //
  // Trim the UDP header.
  //
  NetbufTrim (Packet, UDP4_HEADER_SIZE, TRUE);

  RxData.DataLength = (UINT32) Packet->TotalSize;

  //
  // Try to enqueue this datagram into the instances.
  //
  Enqueued = Udp4EnqueueDgram (Udp4Service, Packet, &RxData);

  if (Enqueued == 0) {
    //
    // Send the port unreachable ICMP packet before we free this NET_BUF
    //
    Udp4SendPortUnreach (Udp4Service->IpIo, NetSession, Udp4Header);
  }

  //
  // Try to free the packet before deliver it.
  //
  NetbufFree (Packet);

  if (Enqueued > 0) {
    //
    // Deliver the datagram.
    //
    Udp4DeliverDgram (Udp4Service);
  }
}


/**
  This function builds and sends out a icmp port unreachable message.

  @param  IpIo                   Pointer to the IP_IO instance.
  @param  NetSession             Pointer to the EFI_NET_SESSION_DATA of the packet
                                 causes this icmp error message.
  @param  Udp4Header             Pointer to the udp header of the datagram causes
                                 this icmp error message.

  @return None.

**/
STATIC
VOID
Udp4SendPortUnreach (
  IN IP_IO                 *IpIo,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN VOID                  *Udp4Header
  )
{
  NET_BUF              *Packet;
  UINT32               Len;
  IP4_ICMP_ERROR_HEAD  *IcmpErrHdr;
  EFI_IP4_HEADER       *IpHdr;
  UINT8                *Ptr;
  IP_IO_OVERRIDE       Override;
  IP_IO_IP_INFO        *IpSender;

  IpSender = IpIoFindSender (&IpIo, NetSession->Dest);
  if (IpSender == NULL) {
    //
    // No apropriate sender, since we cannot send out the ICMP message through
    // the default zero station address IP instance, abort.
    //
    return;
  }

  IpHdr = NetSession->IpHdr;

  //
  // Calculate the requried length of the icmp error message.
  //
  Len = sizeof (IP4_ICMP_ERROR_HEAD) + (EFI_IP4_HEADER_LEN (IpHdr) -
        sizeof (IP4_HEAD)) + ICMP_ERROR_PACKET_LENGTH;

  //
  // Allocate buffer for the icmp error message.
  //
  Packet = NetbufAlloc (Len);
  if (Packet == NULL) {
    return;
  }

  //
  // Allocate space for the IP4_ICMP_ERROR_HEAD.
  //
  IcmpErrHdr = (IP4_ICMP_ERROR_HEAD *) NetbufAllocSpace (Packet, Len, FALSE);

  //
  // Set the required fields for the icmp port unreachable message.
  //
  IcmpErrHdr->Head.Type     = ICMP_TYPE_UNREACH;
  IcmpErrHdr->Head.Code     = ICMP_CODE_UNREACH_PORT;
  IcmpErrHdr->Head.Checksum = 0;
  IcmpErrHdr->Fourth        = 0;

  //
  // Copy the IP header of the datagram tragged the error.
  //
  CopyMem (&IcmpErrHdr->IpHead, IpHdr, EFI_IP4_HEADER_LEN (IpHdr));

  //
  // Copy the UDP header.
  //
  Ptr = (UINT8 *) &IcmpErrHdr->IpHead + EFI_IP4_HEADER_LEN (IpHdr);
  CopyMem (Ptr, Udp4Header, ICMP_ERROR_PACKET_LENGTH);

  //
  // Calculate the checksum.
  //
  IcmpErrHdr->Head.Checksum = (UINT16) ~(NetbufChecksum (Packet));

  //
  // Fill the override data.
  //
  Override.DoNotFragment = FALSE;
  Override.TypeOfService = 0;
  Override.TimeToLive    = 255;
  Override.Protocol      = EFI_IP_PROTO_ICMP;

  CopyMem (&Override.SourceAddress, &NetSession->Dest, sizeof (EFI_IPv4_ADDRESS));
  ZeroMem (&Override.GatewayAddress, sizeof (EFI_IPv4_ADDRESS));

  //
  // Send out this icmp packet.
  //
  IpIoSend (IpIo, Packet, IpSender, NULL, NULL, NetSession->Source, &Override);

  NetbufFree (Packet);
}


/**
  This function handles the received Icmp Error message and demultiplexes it to the
  instance.

  @param  Udp4Service            Pointer to the udp service context data.
  @param  IcmpError              The icmp error code.
  @param  NetSession             Pointer to the EFI_NET_SESSION_DATA abstracted
                                 from the received Icmp Error packet.
  @param  Packet                 Pointer to the Icmp Error packet.

  @return None.

**/
STATIC
VOID
Udp4IcmpHandler (
  IN UDP4_SERVICE_DATA     *Udp4Service,
  IN ICMP_ERROR            IcmpError,
  IN EFI_NET_SESSION_DATA  *NetSession,
  IN NET_BUF               *Packet
  )
{
  EFI_UDP4_HEADER        *Udp4Header;
  EFI_UDP4_SESSION_DATA  Udp4Session;
  LIST_ENTRY             *Entry;
  UDP4_INSTANCE_DATA     *Instance;

  Udp4Header = (EFI_UDP4_HEADER *) NetbufGetByte (Packet, 0, NULL);

  CopyMem (&Udp4Session.SourceAddress, &NetSession->Source, sizeof (EFI_IPv4_ADDRESS));
  CopyMem (&Udp4Session.DestinationAddress, &NetSession->Dest, sizeof (EFI_IPv4_ADDRESS));

  Udp4Session.SourcePort      = NTOHS (Udp4Header->DstPort);
  Udp4Session.DestinationPort = NTOHS (Udp4Header->SrcPort);

  NET_LIST_FOR_EACH (Entry, &Udp4Service->ChildrenList) {
    //
    // Iterate all the instances.
    //
    Instance = NET_LIST_USER_STRUCT (Entry, UDP4_INSTANCE_DATA, Link);

    if (!Instance->Configured ||
      Instance->ConfigData.AcceptPromiscuous ||
      Instance->ConfigData.AcceptAnyPort ||
      EFI_IP4_EQUAL (&Instance->ConfigData.StationAddress, &mZeroIp4Addr)) {
      //
      // Don't try to deliver the ICMP error to this instance if it is not configured,
      // or it's configured to be promiscuous or accept any port or accept all the
      // datagrams.
      //
      continue;
    }

    if (Udp4MatchDgram (Instance, &Udp4Session)) {
      //
      // Translate the Icmp Error code according to the udp spec.
      //
      Instance->IcmpError = IpIoGetIcmpErrStatus (IcmpError, NULL, NULL);

      if (IcmpError > ICMP_ERR_UNREACH_PORT) {
        Instance->IcmpError = EFI_ICMP_ERROR;
      }

      //
      // Notify the instance with the received Icmp Error.
      //
      Udp4ReportIcmpError (Instance);

      break;
    }
  }

  NetbufFree (Packet);
}


/**
  This function reports the received ICMP error.

  @param  Instance               Pointer to the udp instance context data.

  @return None.

**/
VOID
Udp4ReportIcmpError (
  IN UDP4_INSTANCE_DATA  *Instance
  )
{
  EFI_UDP4_COMPLETION_TOKEN  *Token;

  if (NetMapIsEmpty (&Instance->RxTokens)) {
    //
    // There are no receive tokens to deliver the ICMP error.
    //
    return;
  }

  if (EFI_ERROR (Instance->IcmpError)) {
    //
    // Try to get a RxToken from the RxTokens map.
    //
    Token = (EFI_UDP4_COMPLETION_TOKEN *) NetMapRemoveHead (&Instance->RxTokens, NULL);

    if (Token != NULL) {
      //
      // Report the error through the Token.
      //
      Token->Status = Instance->IcmpError;
      gBS->SignalEvent (Token->Event);

      //
      // Clear the IcmpError.
      //
      Instance->IcmpError = EFI_SUCCESS;
    }
  }
}


/**
  This function is a dummy ext-free function for the NET_BUF created for the output
  udp datagram.

  @param  Context                Pointer to the context data.

  @return None.

**/
VOID
Udp4NetVectorExtFree (
  VOID  *Context
  )
{
}


/**
  Set the Udp4 variable data.

  @param  Udp4Service            Udp4 service data.

  @retval EFI_OUT_OF_RESOURCES   There are not enough resources to set the
                                 variable.
  @retval other                  Set variable failed.

**/
EFI_STATUS
Udp4SetVariableData (
  IN UDP4_SERVICE_DATA  *Udp4Service
  )
{
  UINT32                  NumConfiguredInstance;
  LIST_ENTRY              *Entry;
  UINTN                   VariableDataSize;
  EFI_UDP4_VARIABLE_DATA  *Udp4VariableData;
  EFI_UDP4_SERVICE_POINT  *Udp4ServicePoint;
  UDP4_INSTANCE_DATA      *Udp4Instance;
  CHAR16                  *NewMacString;
  EFI_STATUS              Status;

  NumConfiguredInstance = 0;

  //
  // Go through the children list to count the configured children.
  //
  NET_LIST_FOR_EACH (Entry, &Udp4Service->ChildrenList) {
    Udp4Instance = NET_LIST_USER_STRUCT_S (
                     Entry,
                     UDP4_INSTANCE_DATA,
                     Link,
                     UDP4_INSTANCE_DATA_SIGNATURE
                     );

    if (Udp4Instance->Configured) {
      NumConfiguredInstance++;
    }
  }

  //
  // Calculate the size of the Udp4VariableData. As there may be no Udp4 child,
  // we should add extra buffer for the service points only if the number of configured
  // children is more than 1.
  //
  VariableDataSize = sizeof (EFI_UDP4_VARIABLE_DATA);

  if (NumConfiguredInstance > 1) {
    VariableDataSize += sizeof (EFI_UDP4_SERVICE_POINT) * (NumConfiguredInstance - 1);
  }

  Udp4VariableData = AllocatePool (VariableDataSize);
  if (Udp4VariableData == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  Udp4VariableData->DriverHandle = Udp4Service->ImageHandle;
  Udp4VariableData->ServiceCount = NumConfiguredInstance;

  Udp4ServicePoint = &Udp4VariableData->Services[0];

  //
  // Go through the children list to fill the configured children's address pairs.
  //
  NET_LIST_FOR_EACH (Entry, &Udp4Service->ChildrenList) {
    Udp4Instance = NET_LIST_USER_STRUCT_S (
                     Entry,
                     UDP4_INSTANCE_DATA,
                     Link,
                     UDP4_INSTANCE_DATA_SIGNATURE
                     );

    if (Udp4Instance->Configured) {
      Udp4ServicePoint->InstanceHandle = Udp4Instance->ChildHandle;
      Udp4ServicePoint->LocalAddress   = Udp4Instance->ConfigData.StationAddress;
      Udp4ServicePoint->LocalPort      = Udp4Instance->ConfigData.StationPort;
      Udp4ServicePoint->RemoteAddress  = Udp4Instance->ConfigData.RemoteAddress;
      Udp4ServicePoint->RemotePort     = Udp4Instance->ConfigData.RemotePort;

      Udp4ServicePoint++;
    }
  }

  //
  // Get the mac string.
  //
  Status = NetLibGetMacString (
             Udp4Service->ControllerHandle,
             Udp4Service->ImageHandle,
             &NewMacString
             );
  if (EFI_ERROR (Status)) {
    goto ON_ERROR;
  }

  if (Udp4Service->MacString != NULL) {
    //
    // The variable is set already, we're going to update it.
    //
    if (StrCmp (Udp4Service->MacString, NewMacString) != 0) {
      //
      // The mac address is changed, delete the previous variable first.
      //
      gRT->SetVariable (
             Udp4Service->MacString,
             &gEfiUdp4ServiceBindingProtocolGuid,
             EFI_VARIABLE_BOOTSERVICE_ACCESS,
             0,
             NULL
             );
    }

    gBS->FreePool (Udp4Service->MacString);
  }

  Udp4Service->MacString = NewMacString;

  Status = gRT->SetVariable (
                  Udp4Service->MacString,
                  &gEfiUdp4ServiceBindingProtocolGuid,
                  EFI_VARIABLE_BOOTSERVICE_ACCESS,
                  VariableDataSize,
                  (VOID *) Udp4VariableData
                  );

ON_ERROR:

  gBS->FreePool (Udp4VariableData);

  return Status;
}


/**
  Clear the variable and free the resource.

  @param  Udp4Service            Udp4 service data.

  @return None.

**/
VOID
Udp4ClearVariableData (
  IN UDP4_SERVICE_DATA  *Udp4Service
  )
{
  ASSERT (Udp4Service->MacString != NULL);

  gRT->SetVariable (
         Udp4Service->MacString,
         &gEfiUdp4ServiceBindingProtocolGuid,
         EFI_VARIABLE_BOOTSERVICE_ACCESS,
         0,
         NULL
         );

  gBS->FreePool (Udp4Service->MacString);
  Udp4Service->MacString = NULL;
}