You can use the following command to cause the FortiGate to apply strict header checking to verify that a packet is part of a session that should be processed. Strict header checking includes verifying the layer-4 protocol header length, the IP header length, the IP version, the IP checksum, IP options, and verifying that ESP packets have the correct sequence number, SPI, and data length.If the packet fails header checking it is dropped by the FortiGate unit.
config system global
set check-protocol-header strict
Enabling strict header checking disables all hardware acceleration. This includes NP, SP, and CP processing.