/** @file

  Implementation of the SNP.Receive() function and its private helpers if any.

  Copyright (C) 2013, Red Hat, Inc.
  Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>

  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.

**/

#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/UefiBootServicesTableLib.h>

#include "VirtioNet.h"

/**
  Receives a packet from a network interface.

  @param  This       The protocol instance pointer.
  @param  HeaderSize The size, in bytes, of the media header received on the
                     network interface. If this parameter is NULL, then the
                     media header size will not be returned.
  @param  BufferSize On entry, the size, in bytes, of Buffer. On exit, the
                     size, in bytes, of the packet that was received on the
                     network interface.
  @param  Buffer     A pointer to the data buffer to receive both the media
                     header and the data.
  @param  SrcAddr    The source HW MAC address. If this parameter is NULL, the
                     HW MAC source address will not be extracted from the media
                     header.
  @param  DestAddr   The destination HW MAC address. If this parameter is NULL,
                     the HW MAC destination address will not be extracted from
                     the media header.
  @param  Protocol   The media header type. If this parameter is NULL, then the
                     protocol will not be extracted from the media header. See
                     RFC 1700 section "Ether Types" for examples.

  @retval  EFI_SUCCESS           The received data was stored in Buffer, and
                                 BufferSize has been updated to the number of
                                 bytes received.
  @retval  EFI_NOT_STARTED       The network interface has not been started.
  @retval  EFI_NOT_READY         The network interface is too busy to accept
                                 this transmit request.
  @retval  EFI_BUFFER_TOO_SMALL  The BufferSize parameter is too small.
  @retval  EFI_INVALID_PARAMETER One or more of the parameters has an
                                 unsupported value.
  @retval  EFI_DEVICE_ERROR      The command could not be sent to the network
                                 interface.
  @retval  EFI_UNSUPPORTED       This function is not supported by the network
                                 interface.

**/

EFI_STATUS
EFIAPI
VirtioNetReceive (
  IN EFI_SIMPLE_NETWORK_PROTOCOL *This,
  OUT UINTN                      *HeaderSize OPTIONAL,
  IN OUT UINTN                   *BufferSize,
  OUT VOID                       *Buffer,
  OUT EFI_MAC_ADDRESS            *SrcAddr    OPTIONAL,
  OUT EFI_MAC_ADDRESS            *DestAddr   OPTIONAL,
  OUT UINT16                     *Protocol   OPTIONAL
  )
{
  VNET_DEV   *Dev;
  EFI_TPL    OldTpl;
  EFI_STATUS Status;
  UINT16     RxCurUsed;
  UINT16     UsedElemIdx;
  UINT32     DescIdx;
  UINT32     RxLen;
  UINTN      OrigBufferSize;
  UINT8      *RxPtr;
  UINT16     AvailIdx;
  EFI_STATUS NotifyStatus;

  if (This == NULL || BufferSize == NULL || Buffer == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  Dev = VIRTIO_NET_FROM_SNP (This);
  OldTpl = gBS->RaiseTPL (TPL_CALLBACK);
  switch (Dev->Snm.State) {
  case EfiSimpleNetworkStopped:
    Status = EFI_NOT_STARTED;
    goto Exit;
  case EfiSimpleNetworkStarted:
    Status = EFI_DEVICE_ERROR;
    goto Exit;
  default:
    break;
  }

  //
  // virtio-0.9.5, 2.4.2 Receiving Used Buffers From the Device
  //
  MemoryFence ();
  RxCurUsed = *Dev->RxRing.Used.Idx;
  MemoryFence ();

  if (Dev->RxLastUsed == RxCurUsed) {
    Status = EFI_NOT_READY;
    goto Exit;
  }

  UsedElemIdx = Dev->RxLastUsed % Dev->RxRing.QueueSize;
  DescIdx = Dev->RxRing.Used.UsedElem[UsedElemIdx].Id;
  RxLen   = Dev->RxRing.Used.UsedElem[UsedElemIdx].Len;

  //
  // the virtio-net request header must be complete; we skip it
  //
  ASSERT (RxLen >= Dev->RxRing.Desc[DescIdx].Len);
  RxLen -= Dev->RxRing.Desc[DescIdx].Len;
  //
  // the host must not have filled in more data than requested
  //
  ASSERT (RxLen <= Dev->RxRing.Desc[DescIdx + 1].Len);

  OrigBufferSize = *BufferSize;
  *BufferSize = RxLen;

  if (OrigBufferSize < RxLen) {
    Status = EFI_BUFFER_TOO_SMALL;
    goto Exit; // keep the packet
  }

  if (RxLen < Dev->Snm.MediaHeaderSize) {
    Status = EFI_DEVICE_ERROR;
    goto RecycleDesc; // drop useless short packet
  }

  if (HeaderSize != NULL) {
    *HeaderSize = Dev->Snm.MediaHeaderSize;
  }

  RxPtr = (UINT8 *)(UINTN) Dev->RxRing.Desc[DescIdx + 1].Addr;
  CopyMem (Buffer, RxPtr, RxLen);

  if (DestAddr != NULL) {
    CopyMem (DestAddr, RxPtr, SIZE_OF_VNET (VhdrMac));
  }
  RxPtr += SIZE_OF_VNET (VhdrMac);

  if (SrcAddr != NULL) {
    CopyMem (SrcAddr, RxPtr, SIZE_OF_VNET (VhdrMac));
  }
  RxPtr += SIZE_OF_VNET (VhdrMac);

  if (Protocol != NULL) {
    *Protocol = (UINT16) ((RxPtr[0] << 8) | RxPtr[1]);
  }
  RxPtr += sizeof (UINT16);

  Status = EFI_SUCCESS;

RecycleDesc:
  ++Dev->RxLastUsed;

  //
  // virtio-0.9.5, 2.4.1 Supplying Buffers to The Device
  //
  AvailIdx = *Dev->RxRing.Avail.Idx;
  Dev->RxRing.Avail.Ring[AvailIdx++ % Dev->RxRing.QueueSize] =
    (UINT16) DescIdx;

  MemoryFence ();
  *Dev->RxRing.Avail.Idx = AvailIdx;

  MemoryFence ();
  NotifyStatus = VIRTIO_CFG_WRITE (Dev, Generic.VhdrQueueNotify,
                   VIRTIO_NET_Q_RX);

  if (!EFI_ERROR (Status)) { // earlier error takes precedence
    Status = NotifyStatus;
  }

Exit:
  gBS->RestoreTPL (OldTpl);
  return Status;
}