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NdisAllocateNetBuffer function (ndis/nblapi.h)

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Call the NdisAllocateNetBuffer function to allocate and initialize a NET_BUFFER structure from a NET_BUFFER structure pool.

Syntax

NDIS_EXPORTED_ROUTINE NET_BUFFER * NdisAllocateNetBuffer(
  [in]           NDIS_HANDLE PoolHandle,
  [in, optional] MDL         *MdlChain,
  [in]           ULONG       DataOffset,
  [in]           SIZE_T      DataLength
);

Parameters

[in] PoolHandle

A NET_BUFFER structure pool handle that was previously returned from a call to NdisAllocateNetBufferPool.

[in, optional] MdlChain

A pointer to an MDL chain that NDIS uses to initialize the new NET_BUFFER structure. MdlChain can be NULL.

[in] DataOffset

The initial offset, in bytes, from the start of the buffer to the start of the used data space in the MDL chain. Data space ahead of this offset is unused data space. Therefore, this value also represents the initial amount of available backfill space in the MDL chain. If MdlChain is NULL, DataOffset must be 0.

[in] DataLength

The length of the used data space, in bytes, in the MDL chain. If MdlChain is NULL, DataLength must be 0.

Return value

NdisAllocateNetBuffer returns a pointer to the NET_BUFFER structure that NDIS allocated. If the allocation was unsuccessful, this pointer is NULL.

Remarks

Call NdisFreeNetBuffer to free a NET_BUFFER structure that was allocated from a NET_BUFFER structure pool.

Note  NET_BUFFER and NET_BUFFER_LIST structures must be allocated from an NDIS buffer pool. A driver must not allocate and initialize a NET_BUFFER or NET_BUFFER_LIST structure from its private memory pool or the stack.
 
The preallocated NET_BUFFER can be reused by reinitializing it with another MDL chain when it owns NET_BUFFER, but the DataOffset, DataLength, CurrentMdl, and CurrentMdlOffset fields in NET_BUFFER must be consistent with the new MDL chain.

For example, if the original MDL chain contains X DataLength and Y DataOffset, and CurrentMdl starts with the second MDL (M) in the original MDL chain, CurrentMdlOffset is Z. The MdlChain field in NET_BUFFER_DATA then needs to point to a new MDL chain that contains X' DataLength and Y' DataOffset. If CurrentMdl starts with the third MDL (M') in the new MDL chain, CurrentMdlOffset is Z', and the following macros need to be used to set fields in NET_BUFFER:

NET_BUFFER_FIRST_MDL(_NB) = New MDL chain;
NET_BUFFER_DATA_LENGTH(_NB) = X';
NET_BUFFER_DATA_OFFSET(_NB) = Y';
NET_BUFFER_CURRENT_MDL(_NB) = M';
NET_BUFFER_CURRENT_MDL_OFFSET(_NB) = Z';

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), NdisAllocateNetBuffer(ndis)

See also

NET_BUFFER

NET_BUFFER_LIST

NdisAllocateNetBufferPool

NdisFreeNetBuffer