NdisAllocateNetBufferListContext function (ndis/nblapi.h)

Article
02/22/2024

Call the NdisAllocateNetBufferListContext function to allocate more context space in the NET_BUFFER_LIST_CONTEXT structure of a

NET_BUFFER_LIST structure.

Syntax

NDIS_EXPORTED_ROUTINE NDIS_STATUS NdisAllocateNetBufferListContext(
  [in] NET_BUFFER_LIST *NetBufferList,
  [in] USHORT          ContextSize,
  [in] USHORT          ContextBackFill,
  [in] ULONG           PoolTag
);

Parameters

[in] NetBufferList

A pointer to a previously allocated NET_BUFFER_LIST structure.

[in] ContextSize

The amount of context space to allocate in the NET_BUFFER_LIST_CONTEXT structure. This amount must be a multiple of the value defined by sizeof(void*).

[in] ContextBackFill

The amount of memory, in addition to the value of ContextSize, to allocate if NDIS must allocate memory to satisfy the request. This amount must be a multiple of the value defined by sizeof(void*).

[in] PoolTag

A kernel pool tag that NDIS uses to allocate the memory for the NET_BUFFER_LIST_CONTEXT structure, if allocation is required. The tag is a string, delimited by single quotation marks, with up to four characters, usually specified in reversed order. The kernel pool tag helps NDIS to identify the owner of the memory.

Return value

NdisAllocateNetBufferListContext returns one of the following:

Return code	Description
NDIS_STATUS_SUCCESS	NdisAllocateNetBufferListContext successfully allocated context space either by reducing the value of the Offset member of the NET_BUFFER_LIST_CONTEXT structure or by allocating new memory.
NDIS_STATUS_RESOURCES	NdisAllocateNetBufferListContext failed due to insufficient resources.
NDIS_STATUS_FAILURE	NdisAllocateNetBufferListContext failed for reasons other than insufficient resources.

Remarks

If there is enough unused context space available in the NET_BUFFER_LIST_CONTEXT structure to satisfy the request, NdisAllocateNetBufferListContext simply reduces the value of the Offset member in the NET_BUFFER_LIST_CONTEXT structure. Otherwise, NDIS allocates new memory for context space. You can specify ContextBackFill to allocate extra memory so that the next call to NdisAllocateNetBufferListContext does not have to allocate memory.

Note The context space is always aligned to `sizeof(void*)`. This is adequate alignment for all natural types, but it is not adequate for datatypes with unusual alignment requirements, like SLIST_ENTRY.

Call the NdisFreeNetBufferListContext function to release the context space in the NET_BUFFER_LIST_CONTEXT structure that was allocated with NdisAllocateNetBufferListContext.

Requirements

Requirement	Value
Minimum supported client	Supported in NDIS 6.0 and later.
Target Platform	Universal
Header	ndis/nblapi.h (include ndis.h)
Library	Ndis.lib
IRQL	<= DISPATCH_LEVEL
DDI compliance rules	Irql_NetBuffer_Function(ndis)