Re: XDP_REDIRECT not working in XDP_DRV_MODE with Intel xgbe driver

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Sophia Yoo <sy6@princeton.edu> writes:

>> >> So this has nothing to do with the support in the driver; XDP is simply
>> >> not suitable for what you're trying to do. Why are you trying to do this
>> >> in the first place? I.e., what's the higher-level use case here?
>
>> > The higher-level design goal (simplified to what's relevant) is that I
>> > am trying to perform a TCP 3WHS between the kernel network stack and
>> > my xdp ingress/tc egress hooks, where some trigger on xdp ingress
>> > sends a SYN packet to the network stack, and when the network stack
>> > returns a SYN-ACK packet the egress program redirects the packet to
>> > the ingress interface, where the XDP program converts the packet to an
>> > ACK packet, then completing the handshake with the network stack.
>
>> It's trying to handshake with itself (on the same box)? Why? Is this a
>> real use case, or a test for something else? If the latter, have you
>> considered using a veth pair in going to a different namespace (that
>> gets the "direction" right)?
>
> This is a real use case as part of a larger design I am working on.
> However, given that redirect from TC egress to XDP_DRV_MODE ingress
> fundamentally doesn't work, I am rethinking other options to the
> design. Alternatively, it seems that support for XDP_REDIRECT from
> egress to ingress is currently in the works, although I don't believe
> the patch has yet been applied to the mainstream kernel.

Huh, really? Haven't seen that, got a link?

> So I will also try building the kernel myself with the patch and
> hopefully get the egress to ingress redirect working with 2 XDP
> programs attached in driver mode. Thank you very much for all your
> help!

You're welcome :)

-Toke