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NDIS_TASK_OFFLOAD (Windows Embedded CE 6.0)

  • Article

1/6/2010

When a miniport supplies the structure in response to OID_TCP_TASK_OFFLOAD, this structure specifies a NIC's capabilities for performing a particular type of task offloaded from the TCP/IP transport. This structure specifies an offload task that the TCP/IP transport is enabling.

Syntax

typedef struct _NDIS_TASK_OFFLOAD {
  ULONG Version;
  ULONG Size;
  NDIS_TASK Task;
  ULONG OffsetNextTask;
  ULONG TaskBufferLength;
  UCHAR TaskBuffer[1];
} NDIS_TASK_OFFLOAD, *PNDIS_TASK_OFFLOAD;

Members

  • Version
    Version number of this task-offload capability. If the miniport's NIC supports more than one version of a particular task-offload capability, each version of the capability should be indicated with a separate NDIS_TASK_OFFLOAD structure. The TCP/IP transport chooses the most suitable version to enable.
  • Size
    Specifies the size, in bytes, of the NDIS_TASK_OFFLOAD structure. Size is set to sizeof(NDIS_TASK_OFFLOAD) and is used to determine the version of the NDIS_TASK_OFFLOAD structure.

  • Task
    Specifies the type of offload task as one of the following values.

    Value Description

    TcpIpChecksumNdisTask

    Checksum offload. TaskBuffer contains an NDIS_TASK_TCP_IP_CHECKSUM structure.

    IpSecNdisTask

    Not supported.

    TcpLargeSendNdisTask

    Segmentation offload. TaskBuffer contains an NDIS_TASK_TCP_LARGE_SEND structure.
  • OffsetNextTask
    Specifies, in bytes, the offset from the beginning of this NDIS_TASK_OFFLOAD structure to the next NDIS_TASK_OFFLOAD structure. If this NDIS_TASK_OFFLOAD structure is the last one in the buffer, OffsetNextTask is set to 0.
  • TaskBufferLength
    Specifies the size, in bytes, of the structure at TaskBuffer.
  • TaskBuffer
    Specifies a variable-length array that contains information specific to the offload task indicated by Task. The contents of TaskBuffer vary according to the task type.

Remarks

If a NIC has the appropriate capabilities, the Microsoft TCP/IP transport can offload one or more of the following tasks to a NIC:

  • Calculation and/or validation of IP or TCP checksums
  • IP security processing
  • Segmentation of large TCP packets into smaller TCP packets

The TCP/IP transport determines a NIC's task-offload capabilities by querying OID_TCP_TASK_OFFLOAD. In response, a miniport returns in the InformationBuffer member of the NDIS_REQUEST structure an NDIS_TASK_OFFLOAD_HEADER structure followed by one or more NDIS_TASK_OFFLOAD structures. The TaskBuffer member of each NDIS_TASK_OFFLOAD structure contains a task-specific structure (NDIS_TASK_TCP_IP_CHECKSUM or NDIS_TASK_TCP_LARGE_SEND) that specifies a particular task-offload capability supported by the miniport's NIC. If the miniport's NIC supports multiple versions of a particular task-offload capability, it returns one NDIS_TASK_OFFLOAD structure for each version.

After querying a NIC's task-offload capabilities, the TCP/IP transport enables a NIC's task-offload capabilities by setting OID_TCP_TASK_OFFLOAD. In this set operation, the TCP/IP transport supplies in InformationBuffer an NDIS_TASK_OFFLOAD_HEADER structure followed by an NDIS_TASK_OFFLOAD structure for each offload task that it is enabling. The miniport must examine each NDIS_TASK_OFFLOAD structure to determine which offload tasks are being enabled. The miniport must also examine the task-specific structure in TaskBuffer of each NDIS_TASK_OFFLOAD structure to determine which specific capabilities for a particular offload task are being enabled.

Requirements

Header ndis.h
Windows Embedded CE Windows CE .NET 4.0 and later

See Also

Reference

NDIS Structures
NDIS_TASK_OFFLOAD_HEADER
NDIS_REQUEST
NDIS_TASK_TCP_LARGE_SEND
NDIS_TASK_TCP_IP_CHECKSUM
OID_TCP_TASK_OFFLOAD