NET_BUFFER - NtDoc
Native API online documentation, based on the System Informer
(formerly Process Hacker) phnt
headers
// nbl.h
typedef struct _NET_BUFFER {
union {
struct {
NET_BUFFER *Next;
MDL *CurrentMdl;
ULONG CurrentMdlOffset;
union {
ULONG DataLength;
SIZE_T stDataLength;
};
MDL *MdlChain;
ULONG DataOffset;
};
SLIST_HEADER Link;
NET_BUFFER_HEADER NetBufferHeader;
};
USHORT ChecksumBias;
USHORT Reserved;
NDIS_HANDLE NdisPoolHandle;
PVOID NdisReserved[2];
PVOID ProtocolReserved[6];
PVOID MiniportReserved[4];
PHYSICAL_ADDRESS DataPhysicalAddress;
union {
NET_BUFFER_SHARED_MEMORY *SharedMemoryInfo;
SCATTER_GATHER_LIST *ScatterGatherList;
};
} NET_BUFFER, *PNET_BUFFER;
View the official Windows Driver Kit DDI referenceNo description available.
The NET_BUFFER structure specifies data that is transmitted or received over the network.
NextA pointer to the next NET_BUFFER structure in a linked list of NET_BUFFER structures. If this structure is the last NET_BUFFER structure in the list, this member is NULL.
CurrentMdlA pointer to the first MDL that the current driver is using. This member provides an optimization that improves performance by skipping over any MDLs that the current driver is not using.
CurrentMdlOffsetThe offset, in bytes, to the beginning of the used data space in the MDL that is specified by the CurrentMdl member.
DataLengthThe length, in bytes, of the used data space in the MDL chain. The maximum length is 0xFFFFFFFF bytes.
stDataLengthThe length, in bytes, of the used data space in the MDL chain. The maximum length is 0xFFFFFFFF bytes. This member is the same as DataLength, but its type is SIZE_T instead of ULONG.
MdlChainA pointer to a linked list of MDLs that map a data buffer. The data buffer stores the network data.
DataOffsetThe offset, in bytes, from the beginning of the MDL chain to the beginning of the network data in the MDL chain. This offset is also the size, in bytes, of the unused data space.
LinkReserved for NDIS.
NetBufferHeaderA NET_BUFFER_HEADER structure. This is a duplicate of the above union, for compatibility reasons.
ChecksumBiasThe number of bytes to skip over from the beginning of the data buffer when computing a checksum. This member is used by the TCP/IP protocol.
ReservedReserved for future use.
NdisPoolHandleA pool handle that identifies the NET_BUFFER pool from which the NET_BUFFER structure was allocated.
NdisReservedReserved for NDIS.
ProtocolReservedReserved for use by protocol drivers. Protocol drivers and NDIS intermediate drivers can use this area for their own purposes. Intermediate drivers can use this member only if it is not already in use.
MiniportReservedReserved for use by miniport drivers. Miniport drivers and NDIS intermediate drivers can use this area for their own purposes.
DataPhysicalAddressNote The name of this member is NdisReserved1 for NDIS 6.0 drivers and is DataPhysicalAddress for NDIS 6.1 and later drivers. For NDIS 6.0 drivers, this member is reserved for NDIS.
The physical address of the data portion of a frame. This member should be to zero if the driver that allocated NET_BUFFER does not specify the address. This member is valid only if the NDIS_NBL_FLAGS_SPLIT_AT_UPPER_LAYER_PROTOCOL_HEADER or NDIS_NBL_FLAGS_SPLIT_AT_UPPER_LAYER_PROTOCOL_PAYLOAD flag is set in the NblFlags member of the NET_BUFFER_LIST structure that is associated with the NET_BUFFER.
Note A miniport driver can set the DataPhysicalAddress member of the NET_BUFFER structure, even if the structure is not associated with a split frame. In this case, DataPhysicalAddress contains the physical address of the header MDL.
SharedMemoryInfoA pointer to an NET_BUFFER_SHARED_MEMORY structure.
ScatterGatherListThe SCATTER_GATHER_LIST structure describes a scatter/gather list for DMA.
NDIS drivers can call the following functions to allocate and initialize a NET_BUFFER structure:
NDIS drivers can call the NdisAllocateNetBufferListPool function and then set the fAllocateNetBuffer member of the NET_BUFFER_LIST_POOL_PARAMETERS structure to TRUE when allocating a NET_BUFFER_LIST structure pool. In this case, a NET_BUFFER structure is preallocated with each NET_BUFFER_LIST structure that the driver allocates from the pool.
Chained to each NET_BUFFER structure are one or more buffer descriptors that map buffers that contain network packet data. These buffer descriptors are specified as an MDL chain in the NetBufferHeader member. Such network packet data either was received or will be transmitted.
To access additional data space in the MDL chain, NDIS drivers can call the following functions:
NDIS drivers typically use the MiniportReserved or ProtocolReserved members of the NET_BUFFER structure to maintain NET_BUFFER structure context information.
Note Only one driver can use MiniportReserved or ProtocolReserved members. Therefore, if another driver has used either of these members, an intermediate driver cannot use them.
To access members of the NET_BUFFER structure, use the following macros and functions:
For more information on how to use net buffers, see NET_BUFFER Architecture.
NET_BUFFER_LIST_POOL_PARAMETERS
NdisAllocateNetBufferAndNetBufferList
NdisMSendNetBufferListsComplete
NdisRetreatNetBufferListDataStart