[...]

I'm pretty sure I misunderstood what you were going after with 
XDP_REDIRECT reserving the headroom.  Our use case (patches coming in a 
few weeks) will populate the headroom coming out of the driver to XDP, 
and then once the XDP program extracts whatever hints it wants via 
helpers, I fully expect that area in the headroom to get stomped by 
something else.  If we want to send any of that hint data up farther, 
we'll already have it extracted via the helpers, and the eBPF program 
can happily assign it to wherever in the outbound metadata area.

In case its not obvious with the latest xdp metadata patches the outbound
metadata can then be pushed into skb fields via a tc_cls program if needed.

.John

quoted

(There's also Jesper's series from today -- I've seen it but have not
had time to fully grok all of those changes.)

I'm also working through my inbox to get to that series.  I have some 
email to catch up on...

Thanks Andy,
-PJ