PD_BUFFER - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers 
// ndis.h

typedef struct _PD_BUFFER {
  struct _PD_BUFFER   *NextPDBuffer;
  struct _PD_BUFFER   *NextPartialPDBuffer;
  PVOID               PDClientReserved;
  PVOID               PDClientContext;
  PUCHAR              DataBufferVirtualAddress;
  DMA_LOGICAL_ADDRESS DataBufferDmaLogicalAddress;
  ULONG               DataBufferSize;
  USHORT              PDClientContextSize;
  USHORT              Attributes;
  USHORT              Flags;
  USHORT              DataStart;
  ULONG               DataLength;
  union {
    struct {
      union {
        ULONG64 RxFilterContext;
        ULONG64 GftFlowEntryId;
      };
      ULONG                         RxHashValue;
      union {
        struct {
          ULONG RxIPHeaderChecksumSucceeded : 1;
          ULONG RxTCPChecksumSucceeded : 1;
          ULONG RxUDPChecksumSucceeded : 1;
          ULONG RxIPHeaderChecksumFailed : 1;
          ULONG RxTCPChecksumFailed : 1;
          ULONG RxUDPChecksumFailed : 1;
          ULONG RxHashComputed : 1;
          ULONG RxHashWithL4PortNumbers : 1;
          ULONG RxGftDirectionIngress : 1;
          ULONG RxGftExceptionPacket : 1;
          ULONG RxGftCopyPacket : 1;
          ULONG RxGftSamplePacket : 1;
          ULONG RxReserved1 : 4;
          ULONG RxCoalescedSegCount : 16;
          ULONG RxRscTcpTimestampDelta;
        };
        ULONG RxOffloads[2];
      };
      union {
        struct {
          ULONG TxIsIPv4 : 1;
          ULONG TxIsIPv6 : 1;
          ULONG TxTransportHeaderOffset : 10;
          ULONG TxMSS : 20;
          ULONG TxComputeIPHeaderChecksum : 1;
          ULONG TxComputeTCPChecksum : 1;
          ULONG TxComputeUDPChecksum : 1;
          ULONG TxIsEncapsulatedPacket : 1;
          ULONG TxInnerPacketOffsetsValid : 1;
          ULONG TxReserved1 : 11;
          ULONG TxInnerFrameOffset : 8;
          ULONG TxInnerIpHeaderRelativeOffset : 6;
          ULONG TxInnerIsIPv6 : 1;
          ULONG TxInnerTcpOptionsPresent : 1;
        };
        ULONG TxOffloads[2];
      };
      PD_BUFFER_VIRTUAL_SUBNET_INFO VirtualSubnetInfo;
      PD_BUFFER_8021Q_INFO          Ieee8021qInfo;
      USHORT                        GftSourceVPortId;
      ULONG                         Reserved;
      UINT64                        ProviderScratch;
    } MetaDataV0;
  };
} PD_BUFFER;
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Windows Driver Kit DDI reference (ns-ndis-_pd_buffer)

_PD_BUFFER structure

Description

This structure represents a PacketDirect (PD) packet, or a portion of a PD packet in a queue.

Members

NextPDBuffer

A pointer to the next PD_BUFFER structure in the queue.

NextPartialPDBuffer

A pointer to the next partial PD_BUFFER structure in the queue.

PDClientReserved

Reserved for system use. Do not use.

PDClientContext

The client and the provider are not allowed to modify this field. If a client has allocated the PD_BUFFER with a non-zero value for ClientContextSize, then the PDClientContext refers to a buffer size of ClientContextSize. Otherwise, this field is NULL.

DataBufferVirtualAddress

This field represents the address that hosts and software can use to access/modify the packet contents. The actual packet data is always at DataBufferVirtualAddress+DataStart. The provider and the platform never modify the value of this field after the PD_BUFFER initialization.

DataBufferDmaLogicalAddress

This field represents the logical memory location used for storing the packet data. The provider must use for DMA. The actual packet data is always at DataBufferDmaLogicalAddress+DataStart. The provider and the platform must never modify the value of this field after the PD_BUFFER initialization.

DataBufferSize

This is the total size of the allocated data buffer. The provider and the platform must never modify the value of this field after the PD_BUFFER initialization. This data type is ULONG instead of USHORT because of large send offload.

PDClientContextSize

When this value is non-zero, it is the size of the buffer pointed to by PDClientContext. The value of this field must only be modified by the platform. The platform does not change the value of this field after the PD_BUFFER allocation.

Attributes

The attributes must never be modified by the provider. The table below lists attributes that this PD_BUFFER structure can have.

Attribute Description
PD_BUFFER_ATTR_BUILT_IN_DATA_BUFFER A PD_BUFFER allocated with its own accompanying data buffer will have this attribute set. The PD_BUFFER attributes must never be modified by clients or providers.

Flags

The following table lists flags that this PD_BUFFER structure can have.

Flag Description
PD_BUFFER_FLAG_PARTIAL_PACKET_HEAD Indicates that this buffer is the head of partial packets.

DataStart

This field denotes where the packet starts relative to the original starting address of the allocated data buffer. The provider must never modify this field. The provider adds this value to the DataBufferDmaLogicalAddress value to derive the actual target DMA address for packet reception/transmission. For example, the target DMA address value in the hardware receive/transmit descriptor must be set to DataBufferDmaLogicalAddress+DataStart when a PD_BUFFER is posted to a receive/transmit queue.

DataLength

The length of the packet or partial packet data.

MetaDataV0

MetaDataV0.RxFilterContext

The provider sets this to the filter context value obtained from the matched filter that steered the packet to the receive queue. Filter context values are specified by the clients when configuring filters.

MetaDataV0.GftFlowEntryId

If one of the RxGftExceptionPacket or RxGftCopyPacket or RxGftSamplePacket bits are set, the RxFilterContext value is overwritten with a GFT flow entry Id value.

MetaDataV0.RxHashValue

The hash value computed for the incoming packet that is steered to the receive queue using RSS.

MetaDataV0.RxIPHeaderChecksumSucceeded

A common RX offload field that indicates if the IP header checksum succeeded.

MetaDataV0.RxTCPChecksumSucceeded

A common RX offload field that indicates if the TCP checksum succeeded.

MetaDataV0.RxUDPChecksumSucceeded

A common RX offload field that indicates if the UDP checksum succeeded.

MetaDataV0.RxIPHeaderChecksumFailed

A common RX offload field that indicates if the IP header checksum failed.

MetaDataV0.RxTCPChecksumFailed

A common RX offload field that indicates if the TCP checksum failed.

MetaDataV0.RxUDPChecksumFailed

A common RX offload field that indicates if the UDP checksum failed.

MetaDataV0.RxHashComputed

A common RX offload field that indicates if the hash is computed.

MetaDataV0.RxHashWithL4PortNumbers

A common RX offload field that indicates the hash is computed with L4 port numbers.

MetaDataV0.RxGftDirectionIngress

MetaDataV0.RxGftExceptionPacket

A common RX offload field that indicates this is a GFT exception packet.

MetaDataV0.RxGftCopyPacket

A common RX offload field that indicates this is a GFT copy packet.

MetaDataV0.RxGftSamplePacket

A common RX offload field that indicates this is a GFT sample packet.

MetaDataV0.RxReserved1

Reserved.

MetaDataV0.RxCoalescedSegCount

A common RX offload field that contains the amount of coalesced segments.

MetaDataV0.RxRscTcpTimestampDelta

A common RX offload field that contains RSC and TCP timestamp difference.

MetaDataV0.RxOffloads

RX offloads for this buffer.

MetaDataV0.TxIsIPv4

A common TX offload field that indicates this packet is IPv4.

MetaDataV0.TxIsIPv6

A common TX offload field that indicates this packet is IPv6.

MetaDataV0.TxTransportHeaderOffset

A common TX offload field that contains the packet's header offset.

MetaDataV0.TxMSS

A common TX offload field that contains the maximum segment size of this packet.

MetaDataV0.TxComputeIPHeaderChecksum

A common TX offload field that indicates the IP header checksum is computed.

MetaDataV0.TxComputeTCPChecksum

A common TX offload field that indicates the TCP checksum is computed.

MetaDataV0.TxComputeUDPChecksum

A common TX offload field that indicates the UDP checksum is computed.

MetaDataV0.TxIsEncapsulatedPacket

A common TX offload field that indicates the packet is encapsulated.

MetaDataV0.TxInnerPacketOffsetsValid

A common TX offload field that indicates the inner packet offsets are valid.

MetaDataV0.TxReserved1

Reserved.

MetaDataV0.TxInnerFrameOffset

A common TX offload field that contains the inner frame offset.

MetaDataV0.TxInnerIpHeaderRelativeOffset

A common TX offload field that contains the inner IP header relative offset.

MetaDataV0.TxInnerIsIPv6

A common TX offload field that indicates the inner packet is IPv6.

MetaDataV0.TxInnerTcpOptionsPresent

A common TX offload field that indicates the inner TCP options are present.

MetaDataV0.TxOffloads

TX offloads for this buffer.

MetaDataV0.VirtualSubnetInfo

The virtual subnet information.

MetaDataV0.Ieee8021qInfo

The IEEE 802.1Q information.

MetaDataV0.GftSourceVPortId

The GFT source virtual port ID.

MetaDataV0.Reserved

Reserved for system use.

MetaDataV0.ProviderScratch

A scratch field that the PD provider can use for its own purposes while the PD_BUFFER is sitting in the provider queue (in other words, posted by the client but not yet drained back by the client). Once the PD_BUFFER is drained by the client, there is no guarantee that the contents of this field will be preserved.

Remarks

If an L2 packet is represented by multiple PD_BUFFER structures, the first PD_BUFFER must have the PD_BUFFER_ATTR_BUILT_IN_DATA_BUFFER flag set and the NextPartialPDBuffer field must point to the partial PD_BUFFER structures that constitute the whole packet. Each of the partial PD_BUFFER structures must point to the next partial PD_BUFFER by using the NextPartialPDBuffer as opposed to the NextPDBuffer field. The NextPDBuffer field must be NULL in all partial PD_BUFFER structures except for the head buffer. All partial PD_BUFFER structures except for the head buffer must have the PD_BUFFER_ATTR_BUILT_IN_DATA_BUFFER flag cleared. The last partial PD_BUFFER must have it's NextPartialPDBuffer field set to NULL. The total length of the L2 packet is the sum of DataLength fields from each partial PD_BUFFER. The head PD_BUFFER must contain up to and including the IP transport (TCP, UDP, SCTP, etc) header. In the case of encapsulation or double-encapsulation, the inner-most IP transport header must be contained in the head PD_BUFFER.

When posting PD_BUFFER structures to receive queues, DataLength is ignored by the provider (For more information see the ReceiveDataLength description in the NDIS_PD_QUEUE_PARAMETERS structure). When draining completed PD_BUFFER structures from receive queues, the provider stores the length of the received packet in the DataLength field. The length does not include FCS or any stripped 801Q headers. When posting PD_BUFFER structures to transmit queues, DataLength denotes the length of the packet to be sent. When draining completed PD_BUFFER structures from transmit queues, the provider leaves the DataLength field unmodified.

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