XN Tracking: Fragment handling IPv4

[KrisNey-MSFT]

Related information

Scope - P4 DASH pipeline. Requires extending the conntrack table key with Frag ID and using it instead of L4 ports.

[yusefMS06]

What can we do to assist in unblocking this?

Issue has been here for some months now @venkat-pullela-keys

[KrisNey-MSFT]

Handle via behavior of the NIC; frag handling s/be handled by the NIC with the pipeline to see the full packet. Frag packet incoming, we do not have a method to obtain the correct hash, b/c the L4 header isn't present. K to close

[KrisNey-MSFT]

IP fragmentation; (jumbo for example) if split into 2, the 2nd fragmented packet will not have the header (L4 info) in order to perform the 5-tuple hash / steering to the correct queue.
Could do virtual reassembly? Possible but complicated. Packets may not work as expected.
DPU contains functionality of NIC, s/be able to handle. NIC is doing reassembly prior to the hash, although buffer would be needed.
Will this happen prior to the pipeline? May be vendor independent.

Reassemble then go to pipeline? Or reassemble through pipeline? In Clouds, the MTU may be set to transit the network seamlessly. If a specific application scenario requires it, we may need to take IP fragmentation into consideration.

If he has time, @r12f might be able to research / confirm the IP fragmentation requirement.