PxeDhcpIsValid function (wdspxe.h)

Article
10/13/2021

Validates that a packet is a DHCP packet.

Syntax

DWORD PXEAPI PxeDhcpIsValid(
  [in]  PVOID pPacket,
  [in]  ULONG uPacketLen,
  [in]  BOOL  bRequestPacket,
  [out] PBOOL pbPxeOptionPresent
);

Parameters

[in] pPacket

Pointer to a reply packet allocated with the PxePacketAllocate function.

[in] uPacketLen

Length of the packet pointed to by the pPacket parameter.

[in] bRequestPacket

Indicates whether the packet is a request packet. The following table lists the possible values.

Value	Meaning
TRUE 1	Packet to be validated is a request packet from the client.
FALSE 0	Packet to be validated is a packet generated by the server.

[out] pbPxeOptionPresent

Address of a BOOL that is set to TRUE if the packet is a valid DHCP packet that contains the Vendor Class Identifier option (60) with the value set to "PXEClient".

Return value

If the function succeeds, the return value is ERROR_SUCCESS.

Remarks

Providers use this function when the filter set with the PxeProviderSetAttribute function is set to receive all packets to determine if a specified packet is a valid DHCP packet. Providers can also use this function to validate reply packets; typically this is done only for debug or test builds of the provider.

The validation tests include the following tests.

DHCP field	Initialized value
Operation (op)	If the bClientRequest parameter is TRUE, this field must be 1 (BOOTP Request), otherwise this field must be 2 (BOOTP Reply).
Hardware Address Length (hlen)	Must be less than or equal to 16.
Host Name (sname)	Must be NULL terminated.
Boot file name (file)	Must be NULL terminated.
Magic Cookie (first 4 octets of vend)	Must contain valid DHCP Magic Cookie (99 130 83 99).
Option Length	All options must have a valid length and do not overrun the packet.
DHCP Message Type (53)	Must be present.
End Option (255)	Packet must end with DHCP End Option. Due to minimum packet lengths, the packet may be larger but no options may follow the End Option.

Requirements

Requirement	Value
Minimum supported client	None supported
Minimum supported server	Windows Server 2008, Windows Server 2003 with SP2 [desktop apps only]
Target Platform	Windows
Header	wdspxe.h
Library	WdsPxe.lib
DLL	WdsPxe.dll