NET_BUFFER_LIST structure (ndis/nbl.h)

Article
09/01/2022

The NET_BUFFER_LIST structure specifies a linked list of NET_BUFFER structures.

Syntax

typedef struct _NET_BUFFER_LIST {
  union {
    struct {
      NET_BUFFER_LIST *Next;
      NET_BUFFER      *FirstNetBuffer;
    };
    SLIST_HEADER           Link;
    NET_BUFFER_LIST_HEADER NetBufferListHeader;
  };
  NET_BUFFER_LIST_CONTEXT *Context;
  NET_BUFFER_LIST         *ParentNetBufferList;
  NDIS_HANDLE             NdisPoolHandle;
  PVOID                   NdisReserved[2];
  PVOID                   ProtocolReserved[4];
  PVOID                   MiniportReserved[2];
  PVOID                   Scratch;
  NDIS_HANDLE             SourceHandle;
  ULONG                   NblFlags;
  LONG                    ChildRefCount;
  ULONG                   Flags;
  union {
    NDIS_STATUS Status;
    ULONG       NdisReserved2;
  };
  PVOID                   NetBufferListInfo[MaxNetBufferListInfo];
} NET_BUFFER_LIST, *PNET_BUFFER_LIST;

Members

Next

The next NET_BUFFER_LIST structure in the chain.

Drivers should not access this member directly. Instead, they should call the NET_BUFFER_LIST_NEXT_NBL macro.

FirstNetBuffer

The first NET_BUFFER on this NET_BUFFER_LIST.

Drivers should not access this member directly. Instead, they should call the NET_BUFFER_LIST_FIRST_NB macro.

Link

Reserved for NDIS.

NetBufferListHeader

A NET_BUFFER_LIST_HEADER structure.

Context

A pointer to a NET_BUFFER_LIST_CONTEXT structure. Protocol and miniport drivers use this structure to store information about the NET_BUFFER_LIST structure. Information stored in the NET_BUFFER_LIST_CONTEXT structure is opaque to NDIS and other drivers in the stack.

Use the following functions and macros to access data in the NET_BUFFER_LIST_CONTEXT structure:

NdisAllocateNetBufferListContext NdisFreeNetBufferListContext NET_BUFFER_LIST_CONTEXT_DATA_START NET_BUFFER_LIST_CONTEXT_DATA_SIZE

ParentNetBufferList

If this NET_BUFFER_LIST structure is a clone of another NET_BUFFER_LIST structure, this member specifies a pointer to the parent NET_BUFFER_LIST structure. Otherwise, this parameter is NULL. A driver uses the NdisAllocateCloneNetBufferList function to create a clone.

NdisPoolHandle

A pool handle that identifies the NET_BUFFER_LIST pool from which the NET_BUFFER_LIST structure was allocated.

NdisReserved[2]

Reserved for use by NDIS.

ProtocolReserved[4]

Reserved for use by protocol drivers.

MiniportReserved[2]

Reserved for use by miniport drivers.

Scratch

Data that is defined by the current owner of the NET_BUFFER_LIST structure. The current owner, either NDIS or an NDIS driver, can use this member for their own purposes. When the NET_BUFFER_LIST structure is initially allocated, this member is NULL. After the current owner relinquishes ownership, NDIS or another driver can overwrite this member.

SourceHandle

A handle that NDIS provided to the driver in a binding or attaching operation by using one of the following driver-supplied routines:

NDIS uses SourceHandle to return the NET_BUFFER_LIST structure to the driver that sent the NET_BUFFER_LIST structure.

NblFlags

This member contains flags that can be combined with a bitwise OR operation.

Use the NdisTestNblFlag, NdisTestNblFlags, NdisSetNblFlag, and NdisClearNblFlag macros to access the flags.

Intermediate drivers and filter drivers can set the following flags if they do not modify data that is associated with a NET_BUFFER_LIST. For example, if the data did not change, NDIS might reuse the original information from which the NET_BUFFER_LIST was created.

NDIS_NBL_FLAGS_SEND_READ_ONLY

If set, the NET_BUFFER_LIST structure and its data are read-only for send operations.

NDIS_NBL_FLAGS_RECV_READ_ONLY

If set, the NET_BUFFER_LIST structure and its data are read-only for receive operations.

A driver can set the following flags even if it does not split the associated Ethernet frame:

NDIS_NBL_FLAGS_IS_IPV4

All of the Ethernet frames in this NET_BUFFER_LIST structure are IPv4 frames. If this flag is set, the header-data split provider must not set the NDIS_NBL_FLAGS_IS_IPV6 flag.

NDIS_NBL_FLAGS_IS_IPV6

All of the Ethernet frames in this NET_BUFFER_LIST structure are IPv6 frames. If this flag is set, the header-data split provider must not set the NDIS_NBL_FLAGS_IS_IPV4 flag.

NDIS_NBL_FLAGS_IS_TCP

All of the Ethernet frames in this NET_BUFFER_LIST structure are TCP frames. If this flag is set, the header-data split provider must not set the NDIS_NBL_FLAGS_IS_UDP flag, and the provider must set the NDIS_NBL_FLAGS_IS_IPV4 flag or the NDIS_NBL_FLAGS_IS_IPV6 flag.

NDIS_NBL_FLAGS_IS_UDP

All of the Ethernet frames in this NET_BUFFER_LIST structure are UDP frames. If this flag is set, the header-data split provider must not set the NDIS_NBL_FLAGS_IS_TCP flag, and the provider must set the NDIS_NBL_FLAGS_IS_IPV4 flag or the NDIS_NBL_FLAGS_IS_IPV6 flag.

NDIS_NBL_FLAGS_IS_LOOPBACK_PACKET

All of the packets that are associated with this NET_BUFFER_LIST structure are loopback packets.

If the header-data split provider does not split the associated Ethernet frame, the miniport driver must indicate the NET_BUFFER_LIST structure with the following flags cleared:

NDIS_NBL_FLAGS_HD_SPLIT

The header and data are split in all of the Ethernet frames that are associated with this NET_BUFFER_LIST structure.

NDIS_NBL_FLAGS_SPLIT_AT_UPPER_LAYER_PROTOCOL_HEADER

All of the Ethernet frames in this NET_BUFFER_LIST are split at the beginning of the upper layer protocol header. If this flag is set, the header-data split provider must set the NDIS_NBL_FLAGS_IS_IPV4 flag or the NDIS_NBL_FLAGS_IS_IPV6 flag. Also, the provider can set the NDIS_NBL_FLAGS_IS_TCP flag or the NDIS_NBL_FLAGS_IS_UDP flag, but the provider must not set the NDIS_NBL_FLAGS_SPLIT_AT_UPPER_LAYER_PROTOCOL_PAYLOAD flag.

NDIS_NBL_FLAGS_SPLIT_AT_UPPER_LAYER_PROTOCOL_PAYLOAD

All of the Ethernet frames in this NET_BUFFER_LIST structure are split at the beginning of the TCP or UDP payload. If this flag is set, the header-data split provider must set the NDIS_NBL_FLAGS_IS_IPV4 flag or the NDIS_NBL_FLAGS_IS_IPV6 flag. Also, the provider must set the NDIS_NBL_FLAGS_IS_TCP flag or the NDIS_NBL_FLAGS_IS_UDP flag, but the provider must not set the NDIS_NBL_FLAGS_SPLIT_AT_UPPER_LAYER_PROTOCOL_HEADER flag.

ChildRefCount

If this NET_BUFFER_LIST structure has clones (is a parent), this member specifies the number of outstanding clones. Otherwise, this member is zero.

Flags

Attributes of the NET_BUFFER_LIST structure. The following definitions specify a bit mask for a set of flags:

NBL_FLAGS_PROTOCOL_RESERVED

This set is reserved for protocol drivers.

Note Starting with NDIS 6.30, two additional bits are available for protocol use: 0x00000003. A NDIS 6.30 protocol may use these bits if and only if NdisGetVersion returns a value greater than or equal to NDIS_RUNTIME_VERSION_630. Protocols must not use these bits on earlier versions of NDIS, because prior to 6.30, NDIS uses them internally.

NBL_FLAGS_MINIPORT_RESERVED

This set is reserved for miniport drivers.

NBL_FLAGS_SCRATCH

The current owner of the NET_BUFFER_LIST structure, either NDIS or an NDIS driver, can use this set. When the current owner relinquishes ownership, NDIS or another driver can overwrite these flags.

NBL_FLAGS_NDIS_RESERVED

This set is reserved for NDIS.

Status

The final completion status of a network data operation on this NET_BUFFER_LIST structure. Miniport drivers write this value before calling the NdisMSendNetBufferListsComplete function. Miniport drivers specify one of the following values:

NDIS_STATUS_SUCCESS

All the network data described by NET_BUFFER structures associated with this NET_BUFFER_LIST structure was successfully transmitted over the network.

NDIS_STATUS_INVALID_LENGTH

The size of the data in some NET_BUFFER structures associated with this NET_BUFFER_LIST structure was too large for the underlying NIC.

NDIS_STATUS_RESOURCES

The send request for this NET_BUFFER_LIST structure failed due to insufficient resources.

NDIS_STATUS_FAILURE

This send request for this NET_BUFFER_LIST structure failed due to some reason other than those stated in the previous three values.

NDIS_STATUS_SEND_ABORTED

NDIS called the MiniportCancelSend function to cancel the send operation for this NET_BUFFER_LIST structure.

NDIS_STATUS_RESET_IN_PROGRESS

The miniport driver aborted the send request due to a reset.

NDIS_STATUS_PAUSED

If a driver must reject send requests because it is paused, it sets the complete status in each affected NET_BUFFER_LIST to NDIS_STATUS_PAUSED.

NdisReserved2

Reserved for NDIS.

NetBufferListInfo[MaxNetBufferListInfo]

An array of values containing information that is common to all NET_BUFFER structures in the list. This information is often referred to as "out-of-band (OOB) data."

Use the NDIS_NET_BUFFER_LIST_INFO enumeration values with the NET_BUFFER_LIST_INFO macro to set and get values in the NetBufferListInfo array.

Remarks

NDIS drivers can call any of the following functions to allocate and initialize a NET_BUFFER_LIST structure:

NdisAllocateNetBufferList

NdisAllocateNetBufferAndNetBufferList NdisAllocateCloneNetBufferList NdisAllocateFragmentNetBufferList NdisAllocateReassembledNetBufferList

All NET_BUFFER structures associated with a NET_BUFFER_LIST structure have the attributes that are specified by the NetBufferListInfo and Context members.

When a driver calls the NdisSendNetBufferLists or NdisFSendNetBufferLists function, it loses ownership of:

The specified NET_BUFFER_LIST structure.
The attached NET_BUFFER structures and MDLs.
Any attached NDIS_REQUEST_CONTROLs.
All NetBufferListInfo data that is associated with the NET_BUFFER_LIST structure.

The current owner of a list of NET_BUFFER_LIST structures can move a NET_BUFFER_LIST structure to another list. However, all NET_BUFFER structures associated with a NET_BUFFER_LIST structure should stay with the same NET_BUFFER_LIST structure. Only the driver that created the NET_BUFFER structures can move them to a different NET_BUFFER_LIST structure. The current owner cannot modify a NET_BUFFER structure's Next member.

A list of NET_BUFFER_LIST structures is a simple singly linked and NULL-terminated list. To move a NET_BUFFER_LIST structure to a different list, make appropriate updates to the Next members in both the source and destination lists.

To access members of the NET_BUFFER_LIST structure, use the following macros and functions:

NET_BUFFER_LIST_NEXT_NBL

NET_BUFFER_LIST_FIRST_NB

NET_BUFFER_LIST_FLAGS

NET_BUFFER_LIST_MINIPORT_RESERVED NET_BUFFER_LIST_CONTEXT_DATA_START NET_BUFFER_LIST_CONTEXT_DATA_SIZE

NET_BUFFER_LIST_INFO

NET_BUFFER_LIST_STATUS

NET_BUFFER_LIST_PROTOCOL_RESERVED NdisGetPoolFromNetBufferList

For more information on how to use net buffers, see NET_BUFFER Architecture.

Requirements

Requirement	Value
Minimum supported client	Supported in NDIS 6.0 and later.
Header	ndis/nbl.h (include ndis.h)