NDIS_PACKET_EXTENSION_FROM_PACKET (Windows CE 5.0)
This macro returns a pointer to the NDIS_PACKET_EXTENSION structure associated with a packet descriptor.
PNDIS_PACKET_EXTENSION NDIS_PACKET_EXTENSION_FROM_PACKET(PNDIS_PACKET_P);
Parameters
- _P
Points to a packet descriptor.
Return Values
The return value is a pointer to the NDIS_PACKET_EXTENSION structure associated with the given packet descriptor. The return value is NULL if there is no per-packet information for the packet.
Remarks
The NDIS_PACKET_EXTENSION structure contains an array of PVOID, each of which either points to or contains a specific type of per-packet information. After obtaining the pointer to the NDIS_PACKET_EXTENSION structure, the driver can use the appropriate array index to access a particular type of per-packet information.
A protocol or miniport driver should call this macro when it needs to read and/or write more than one type of per-packet information associated with a packet descriptor. If the driver needs to access just one type of per-packet information, it should call the NDIS_PER_PACKET_INFO_FROM_PACKET macro.
After obtaining the pointer to the NDIS_PACKET_EXTENSION structure returned by NDIS_PACKET_EXTENSION_FROM_PACKET, a driver can use array indexes to access a particular type of per-packet information.
The following table shows the possible array indexes a driver can use.
| Array Index | Description |
|---|---|
| TcpIpChecksumPacketInfo | Indexes a pointer to an NDIS_TCP_IP_CHECKSUM_PACKET_INFO structure. |
| IpSecPacketInfo | Not supported in Windows CE. |
| TcpLargeSendPacketInfo | Indexes a pointer that contains a ULONG value. Before passing a large TCP packet to a miniport for segmentation, the TCP/IP transport writes this value with the maximum segment size (MSS), which is the current maximum transmission unit (MTU). Before completing the send of a large TCP packet that it has segmented into smaller packets, a miniport writes this value with the total number of user data bytes that it sent in the packets segmented from the large TCP packet. |
| ClassificationHandlePacketInfo | This is reserved. |
| ScatterGatherListPacketInfo | Not supported in Windows CE. |
| Ieee8021pPriority | Indexes a UINT, which specifies 802.1p priority information that is used to establish packet priority in shared-media 802 networks. The bits that are set to one in this UINT specify an 802.1p priority value.
Note Windows CE does not support 802.1p packet prioritization. |
| OriginalPacketInfo | Indexes a pointer to a NDIS_PACKET structure. This structure specifies a packet descriptor that contains original information that was previously received over the network and indicated up by the lowest-level driver in a stack of NDIS drivers. Each driver in the layered stack can access the out-of-band (OOB) data block that is associated with the packet that is received from the network without requiring that the packet be copied to each layer. |
The NDIS_PACKET_EXTENSION_FROM_PACKET macro is defined as follows.
#define NDIS_PACKET_EXTENSION_FROM_PACKET(_P) ((PNDIS_PACKET_EXTENSION)((PUCHAR)(_P) + (_P)->Private.NdisPacketOobOffset + sizeof(NDIS_PACKET_OOB_DATA)))
Requirements
OS Versions: Windows CE .NET 4.0 and later.
Header: Ndis.h.
See Also
NDIS_PACKET | NDIS_PER_PACKET_INFO_FROM_PACKET | NDIS_PACKET_EXTENSION | NdisIMCopySendCompletePerPacketInfo | NdisIMCopySendPerPacketInfo | NDIS_PACKET_OOB_DATA | NDIS_TCP_IP_CHECKSUM_PACKET_INFO
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