Re: [PATCH RFC 1/3] xdp: Infrastructure to generalize XDP

On 09/21/16 at 07:19am, Tom Herbert wrote:

certain design that because of constraints on one kernel interface. As
a kernel developer I want flexibility on how we design and implement
things!

Perfectly valid argument. I reviewed your ILA changes and did not
object to them.

I think there are two questions that this patch set poses for the
community wrt XDP:

#1: Should we allow alternate code to run in XDP other than BPF?
#2: If #1 is true what is the best way to implement that?

If the answer to #1 is "no" then the answer to #2 is irrelevant. So
with this RFC I'm hoping we can come the agreement on questions #1.

I'm not opposed to running non-BPF code at XDP. I'm against adding
a linked list of hook consumers.

Would anyone require to run XDP-BPF in combination ILA? Or XDP-BPF
in combination with a potential XDP-nftables? We don't know yet I
guess.

Maybe exclusive access to the hook for one consumer as selected by
the user is good enough.

If that is not good enough: BPF (and potentially nftables in the
future) could provide means to perform a selection process where a
helper call can run another XDP prog or return a verdict to trigger
another XDP prog. Definitely more flexible and faster than a linear
list doing  if, else if, else if, else if, ...