Query Offload Sequence

  • Article

[The TCP chimney offload feature is deprecated and should not be used.]

After the host stack sends a query request to NDIS, NDIS calls the offload target's MiniportQueryOffload function. The MiniportQueryOffload function inputs the following parameters:

  • A handle in the MiniportAdapterContext parameter that references the adapter instance.

  • A pointer in the OffloadBlockList parameter that points to an NDIS_MINIPORT_OFFLOAD_BLOCK_LIST structure. This structure can be a stand-alone structure or the root of a linked list of NDIS_MINIPORT_OFFLOAD_BLOCK_LIST structures that form the framework of an offload state tree

The MiniportQueryOffload function stores the pointer that is in OffloadBlockList and then returns. The offload target always completes the query operation asynchronously by calling NdisMQueryOffloadStateComplete.

The following figure shows the call sequence of a query offload operation.

diagram illustrating a call sequence of a query offload operation

The offload target's internal query function, which is labeled "NicQuery" in the preceding figure, queries the state that is specified in the state tree. After the internal query operation is complete, the offload target writes completion status to each NDIS_MINIPORT_OFFLOAD_BLOCK_LIST structure in the state tree and calls the NdisMQueryOffloadStateComplete function. The offload target returns the state tree to the host stack by passing to NdisMQueryOffloadStateComplete function the same pointer in OffloadBlockList that NDIS passed to the offload target's MiniportQueryOffload function.

Note that the host stack can query a state object while a query of that state object is in progress.