MINIPORT_SEND_NET_BUFFER_LISTS callback function (ndis.h)

Article
10/21/2021

NDIS calls the MiniportSendNetBufferLists function to transmit network data that is contained in a linked list of NET_BUFFER_LIST structures.

Note You must declare the function by using the MINIPORT_SEND_NET_BUFFER_LISTS type. For more information, see the following Examples section.

Syntax

MINIPORT_SEND_NET_BUFFER_LISTS MiniportSendNetBufferLists;

void MiniportSendNetBufferLists(
  [in] NDIS_HANDLE MiniportAdapterContext,
  [in] PNET_BUFFER_LIST NetBufferList,
  [in] NDIS_PORT_NUMBER PortNumber,
  [in] ULONG SendFlags
)
{...}

Parameters

[in] MiniportAdapterContext

A handle to a context area that the miniport driver allocated in its MiniportInitializeEx function. The miniport driver uses this context area to maintain state information about an adapter.

[in] NetBufferList

A pointer to the first NET_BUFFER_LIST structure in a linked list of NET_BUFFER_LIST structures. Each NET_BUFFER_LIST structure in the list describes a list of NET_BUFFER structures. Each NET_BUFFER structure in the list maps to a chain of MDLs. The MDLs contain the network data.

[in] PortNumber

A port number that identifies a miniport adapter port. To assign a miniport adapter port number, call the NdisMAllocatePort function. A zero value identifies the default port of a miniport adapter.

[in] SendFlags

Flags that define attributes for the send operation. The flags can be combined with an OR operation. To clear all the flags, set this member to zero. This function supports the following flags:

NDIS_SEND_FLAGS_DISPATCH_LEVEL

Specifies that the current IRQL is DISPATCH_LEVEL. For more information about this flag, see Dispatch IRQL Tracking.

NDIS_SEND_FLAGS_CHECK_FOR_LOOPBACK

Specifies that NDIS should check for loopback. By default, NDIS does not loop back data to the driver that submitted the send request. An overlying driver can override this behavior by setting this flag. When this flag is set, NDIS identifies all the NET_BUFFER structures that contain data that matches the receive criteria for the binding. NDIS indicates NET_BUFFER structures that match the criteria to the overlying driver. This flag has no affect on checking for loopback, or looping back, on other bindings.

Return value

None

Remarks

MiniportSendNetBufferLists is a required function for miniport drivers. When an overlying driver calls the NdisSendNetBufferLists function, NDIS calls the MiniportSendNetBufferLists function of the bound miniport driver.

When transmitting the network data that NDIS passes in the NetBufferLists parameter, the miniport driver must use the following guidelines:

The order of the NET_BUFFER structures in each NET_BUFFER_LIST structure must be preserved.
The order of the NET_BUFFER_LIST structures should be preserved if they are to be transmitted on the same connection.
If the NET_BUFFER_LIST structures are to be transmitted on different connections, they can be split into multiple transmit queues if the following features are in use. In this case, the order of the NET_BUFFER_LIST structures for each connection should be preserved.
- Receive side scaling (RSS) (The RSS hash value in the NET_BUFFER_LIST structure can be used as an index into the RSS indirection table.)
- Virtual Machine Queue (VMQ) (The queue identifier of the outgoing queue is set in the NetBufferListFilteringInfo OOB information. For more information, see VMQ Transmit Path.)
- IEEE 802.1 Data Center Bridging (DCB) (You can key off the Traffic Class (TC).)
- IEEE 802.1p (You can key off 802.1p tags without DCB.)

Miniport drivers accept all send requests that NDIS makes by calling the MiniportSendNetBufferLists function. If a miniport driver cannot complete a send request immediately, the driver must hold the request in a queue until it can complete the request. While a send request is pending, the miniport driver retains ownership of the NET_BUFFER_LIST structures and all the protocol-allocated resources associated with the NET_BUFFER_LIST structures.

The miniport driver must call the NdisMSendNetBufferListsComplete function to complete the send requests for all NET_BUFFER_LIST structures. To improve system performance, the driver can create a linked list that contains the NET_BUFFER_LIST structures from multiple send requests. The driver can then pass such a linked list in a single call to NdisMSendNetBufferListsComplete.NET_BUFFER_LIST structures and other associated resources should be treated as inaccessible by the miniport driver as soon as the driver calls NdisMSendNetBufferListsComplete.

The MiniportSendNetBufferLists function must synchronize access to its internal queues of network data with the driver's other MiniportXxx functions that access the same queues. A miniport driver can use spin locks to synchronize access to the queues.

Protocol drivers are responsible for determining what network data is required, based on the medium type that the bound miniport driver selected. However, a protocol driver can supply network data that specifies packets that are shorter than the minimum packet size for the selected medium. In this case, MiniportSendNetBufferLists must pad the packets with zeros if the selected medium imposes a minimum-length requirement on the transmit packet size.

If the miniport driver set the NDIS_MAC_OPTION_NO_LOOPBACK flag when NDIS queried the OID_GEN_MAC_OPTIONS OID, the miniport driver must not attempt to loop back any network data. NDIS provides software loopback support for such a driver.

NDIS calls MiniportSendNetBufferLists at IRQL<= DISPATCH_LEVEL.

Examples

To define a MiniportSendNetBufferLists function, you must first provide a function declaration that identifies the type of function you're defining. Windows provides a set of function types for drivers. Declaring a function using the function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it's a requirement for writing drivers for the Windows operating system.

For example, to define a MiniportSendNetBufferLists function that is named "MySendNetBufferLists", use the MINIPORT_SEND_NET_BUFFER_LISTS type as shown in this code example:

MINIPORT_SEND_NET_BUFFER_LISTS MySendNetBufferLists;

Then, implement your function as follows:

_Use_decl_annotations_
VOID
 MySendNetBufferLists(
    NDIS_HANDLE  MiniportAdapterContext,
    PNET_BUFFER_LIST  NetBufferList,
    NDIS_PORT_NUMBER  PortNumber,
    ULONG  SendFlags
    )
  {...}

The MINIPORT_SEND_NET_BUFFER_LISTS function type is defined in the Ndis.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the Use_decl_annotations annotation to your function definition. The Use_decl_annotations annotation ensures that the annotations that are applied to the MINIPORT_SEND_NET_BUFFER_LISTS function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for NDIS Drivers.

For information about Use_decl_annotations, see Annotating Function Behavior.

Requirements

Requirement	Value
Minimum supported client	Supported in NDIS 6.0 and later.
Target Platform	Windows
Header	ndis.h (include Ndis.h)
IRQL	<= DISPATCH_LEVEL
DDI compliance rules	NdisTimedDataHang, NdisTimedDataSend