netdev - XDP seeking input from NIC hardware vendors

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Date:	Thu, 7 Jul 2016 12:42:45 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	"iovisor-dev@...ts.iovisor.org" <iovisor-dev@...ts.iovisor.org>
Cc:	brouer@...hat.com, Brenden Blanco <bblanco@...mgrid.com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Rana Shahout <ranas@...lanox.com>, Ari Saha <as754m@....com>,
	Tariq Toukan <tariqt@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Simon Horman <horms@...ge.net.au>,
	Simon Horman <simon.horman@...ronome.com>,
	Jakub Kicinski <jakub.kicinski@...ronome.com>,
	Edward Cree <ecree@...arflare.com>,
	John Fastabend <john.r.fastabend@...el.com>
Subject: XDP seeking input from NIC hardware vendors

Would it make sense from a hardware point of view, to split the XDP
eBPF program into two stages.

 Stage-1: Filter (restricted eBPF / no-helper calls)
 Stage-2: Program

Then the HW can choose to offload stage-1 "filter", and keep the
likely more advanced stage-2 on the kernel side.  Do HW vendors see a
benefit of this approach?

The generic problem I'm trying to solve is parsing. E.g. that the
first step in every XDP program will be to parse the packet-data,
in-order to determine if this is a packet the XDP program should
process.

Actions from stage-1 "filter" program:
 - DROP (like XDP_DROP, early drop)
 - PASS (like XDP_PASS, normal netstack)
 - MATCH (call stage-2, likely carry-over opaque return code)

The MATCH action should likely carry-over an opaque return code, that
makes sense for the stage-2 program. E.g. proto id and/or data offset.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer