Re: mlx5: is GTP encapsulation possible using the rte_flow api?

[Raslan Darawsheh <rasland@nvidia.com>]

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Hello,

> Hi All,

>I wonder whether it would be possible to implement HW accelerated GTP
>encapsulation (as a first step) functionality using a Bluefield 2 NIC
>and the rte_flow API?

yes should be supported.

>The encapsulation would need to work between different ports using
>hairpin queues.

>Let's say I already have the rules in dpdk-testpmd that remove the
>original ETH header using raw_decap, and add the new ETH/IP/UDP/GTP
>using raw_encap.

>Now I would need to update some header fields (payload length for
>pv4, udp, gtp). I would use "modify_field op add", but I found no way
>I can access the payload length field for UDP and GTP.

These are usually calculated by the NIC on ecnap so you don't need to set these fields or modify them.

>For example, when I try to access the UDP payload length field by using
>"dst_type udp_port_src dst_offset 32" in the "modify_field" action,
>I get a "destination offset is too big: Invalid argument" error.

In general and in MLX5 we don’t support changing the length field of the packet

>This seems to be caused by a check in the mlx5 driver, which is a bit
>surprising as the documentation in rte_flow.rst (DPDK version 24.03)
>says that:

   >``offset`` allows going past the specified packet field boundary to
   >copy a field to an arbitrary place in a packet,

>Is this just a driver limitation or an HW limitation? Or could a flex
>item solve this?

>Thanks, Laszlo

Kindest regards
Raslan Darawsheh

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