NDIS_RECEIVE_SCALE_PARAMETERS structure (ntddndis.h)
The NDIS_RECEIVE_SCALE_PARAMETERS structure specifies the Receive Side Scaling (RSS) parameters for a miniport adapter.
Version Information
Syntax
typedef struct _NDIS_RECEIVE_SCALE_PARAMETERS {
NDIS_OBJECT_HEADER Header;
USHORT Flags;
USHORT BaseCpuNumber;
ULONG HashInformation;
USHORT IndirectionTableSize;
ULONG IndirectionTableOffset;
USHORT HashSecretKeySize;
ULONG HashSecretKeyOffset;
ULONG ProcessorMasksOffset;
ULONG NumberOfProcessorMasks;
ULONG ProcessorMasksEntrySize;
PROCESSOR_NUMBER DefaultProcessorNumber;
} NDIS_RECEIVE_SCALE_PARAMETERS, *PNDIS_RECEIVE_SCALE_PARAMETERS;
Members
Header
The NDIS_OBJECT_HEADER structure for the NDIS_RECEIVE_SCALE_PARAMETERS structure. Set the Type member of the structure that Header specifies to NDIS_OBJECT_TYPE_RSS_PARAMETERS.
For NDIS 6.60 and later drivers, set the Revision member to NDIS_RECEIVE_SCALE_PARAMETERS_REVISION_3 and the Size member to NDIS_SIZEOF_RECEIVE_SCALE_PARAMETERS_REVISION_3.
For NDIS 6.20 and pre-NDIS 6.60 drivers, set the Revision member to NDIS_RECEIVE_SCALE_PARAMETERS_REVISION_2 and the Size member to NDIS_SIZEOF_RECEIVE_SCALE_PARAMETERS_REVISION_2.
For NDIS 6.0 drivers, set the Revision member to NDIS_RECEIVE_SCALE_PARAMETERS_REVISION_1 and the Size member to NDIS_SIZEOF_RECEIVE_SCALE_PARAMETERS_REVISION_1.
Flags
A USHORT value that indicates what the miniport driver should do with the receive-scale parameters. The driver can use these flags to quickly determine which parameters have changed and update the RSS settings accordingly.
Note
The flags which refer to unchanged RSS parameter information are for optimization purposes. If a flag is set, no change has been made to the corresponding parameter. If a flag is clear, the corresponding parameter may or may not have changed and miniport drivers must compare the new value of the parameter with the current value in order to determine a potential change in the parameter.
In a query request, set this member to zero.
In a set request, the flags are defined as follows:
| Value | Meaning |
|---|---|
| NDIS_RSS_PARAM_FLAG_BASE_CPU_UNCHANGED | The BaseCpuNumber member has not changed. |
| NDIS_RSS_PARAM_FLAG_HASH_INFO_UNCHANGED | The HashInformation member has not changed. The hash information includes the hash types and hash function. |
| NDIS_RSS_PARAM_FLAG_ITABLE_UNCHANGED | The indirection table and associated data members have not changed. |
| NDIS_RSS_PARAM_FLAG_HASH_KEY_UNCHANGED | The secret key and associated data members have not changed. |
| NDIS_RSS_PARAM_FLAG_DISABLE_RSS | If this flag is set, the miniport driver should ignore all of the other flags and settings and disable RSS on the NIC. |
| NDIS_RSS_PARAM_FLAG_DEFAULT_PROCESSOR_UNCHANGED | If this flag is set, the DefaultProcessorNumber has not changed. |
BaseCpuNumber
The lowest number CPU to use for RSS. Because this value is incorporated into the indirection table, set BaseCpuNumber to zero.
HashInformation
In a set request, this member is the hash type and hash function that the NIC should use to compute the hash values for the incoming packets. If the hash function that is specified within the HashInformation member is zero, RSS is disabled.
In a query request, this member is the hash type and hash function that the NIC is using.
Overlying drivers and NDIS can use the NDIS_RSS_HASH_INFO_FROM_TYPE_AND_FUNC macro to combine the hash type and hash function into hash information and set the HashInformation member.
Miniport drivers can use the NDIS_RSS_HASH_TYPE_FROM_HASH_INFO macro to get the hash type from HashInformation and the NDIS_RSS_HASH_FUNC_FROM_HASH_INFO macro to get the hash function.
IndirectionTableSize
The size of the indirection table, in bytes. The upper layer driver that sets the RSS parameters, must ensure that the number of entries in the indirection table is a power of 2.
IndirectionTableOffset
The offset of the indirection table from the beginning of the NDIS_RECEIVE_SCALE_PARAMETERS structure. Use this offset to get the indirection table.
HashSecretKeySize
The size of the secret key array of the hash function, in bytes. The size of the array is 40 bytes for NdisHashFunctionToeplitz.
HashSecretKeyOffset
The offset of the secret key array of the hash function from the beginning of the NDIS_RECEIVE_SCALE_PARAMETERS structure. Use this offset to get the 320-bit (40 bytes) secret key.
In a set request, the secret key can contain any data that the overlying driver chooses.
In a query request, the secret key contains the data that the NIC is using.
ProcessorMasksOffset
The offset of an array of processor masks from the beginning of the NDIS_RECEIVE_SCALE_PARAMETERS structure.
NumberOfProcessorMasks
The number of elements in an array of type GROUP_AFFINITY representing the processors used in the indirection table
ProcessorMasksEntrySize
The size, in bytes, of a processor mask array entry.
DefaultProcessorNumber
When RSS is enabled, specifies the processor that will receive packets where the hash cannot be calculated.
Remarks
The NDIS_RECEIVE_SCALE_PARAMETERS structure defines the Receive Side Scaling (RSS) parameters for the OID_GEN_RECEIVE_SCALE_PARAMETERS OID.
Note
The indirection table and secret key are appended after the NDIS_RECEIVE_SCALE_PARAMETERS structure members.
The indirection table has the following version-specific format:
| NDIS Version | Format |
|---|---|
| NDIS 6.20 and later versions | PROCESSOR_NUMBER IndirectionTable[IndirectionTableSize/sizeof(PROCESSOR_NUMBER)]; |
| Pre-NDIS 6.20 | CCHAR IndirectionTable[IndirectionTableSize] |
NDIS automatically translates the indirection table if there are older and newer drivers in a driver stack.
The miniport driver must examine the indirection table to determine the CPU numbers to associate with hardware queues. If the total number of different CPU numbers that appear in the indirection table is more than the number of hardware queues that the NIC supports, the miniport driver must pick a subset of the CPU numbers from the indirection table. The subset is equal in number to the number of hardware queues.
The miniport driver specified the number of receive queues value in response to OID_GEN_RECEIVE_SCALE_CAPABILITIES.
To clear the RSS parameters and disable RSS, NDIS sets the hash function that is specified within the HashInformation member is zero. NDIS can also disable RSS by setting the NDIS_RSS_PARAM_FLAG_DISABLE_RSS flag in the NDIS_RECEIVE_SCALE_PARAMETERS structure.
If RSS is disabled, the miniport driver should handle receive operations without performing RSS operations.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Supported in NDIS 6.0 and later. |
| Header | ntddndis.h (include Ndis.h) |
See also
NDIS_RSS_HASH_FUNC_FROM_HASH_INFO
NDIS_RSS_HASH_INFO_FROM_TYPE_AND_FUNC
NDIS_RSS_HASH_TYPE_FROM_HASH_INFO