netdev - Re: [RFC PATCH v2 1/5] bpf: add PHYS_DEV prog type for early driver filter

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Message-ID: <57091FCE.50104@mojatatu.com>
Date:	Sat, 9 Apr 2016 11:29:18 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Tom Herbert <tom@...bertland.com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Jesper Dangaard Brouer <brouer@...hat.com>,
	Brenden Blanco <bblanco@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Edward Cree <ecree@...arflare.com>,
	john fastabend <john.fastabend@...il.com>,
	Thomas Graf <tgraf@...g.ch>,
	Johannes Berg <johannes@...solutions.net>,
	eranlinuxmellanox@...il.com, Lorenzo Colitti <lorenzo@...gle.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v2 1/5] bpf: add PHYS_DEV prog type for early driver
 filter

On 16-04-09 07:29 AM, Tom Herbert wrote:

> +1. Forwarding which will be a common application almost always
> requires modification (decrement TTL), and header data split has
> always been a weak feature since the device has to have some arbitrary
> rules about what headers needs to be split out (either implements
> protocol specific parsing or some fixed length).

Then this is sensible. I was cruising the threads and
confused by your earlier emails Tom because you talked
about XPS etc. It sounded like the idea evolved into putting
the whole freaking stack on bpf.
If this is _forwarding only_ it maybe useful to look at
Alexey's old code in particular the DMA bits;
he built his own lookup algorithm but sounds like bpf is
a much better fit today.

cheers,
jamal