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

[Maayan Kashani <mkashani@nvidia.com>]

++@Gregory Etelson

Regards,
Maayan Kashani

> -----Original Message-----
> From: László Molnár <laszlo.molnar@ericsson.com>
> Sent: Wednesday, 8 May 2024 18:24
> To: users@dpdk.org
> Subject: mlx5: is GTP encapsulation possible using the rte_flow api?
> 
> 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?
> 
> 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 ipv4,
> 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.
> 
> 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.
> 
> 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