netdev - Re: [PATCH iproute2 -next] tc, bpf: finalize eBPF support for cls and act front-end

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Message-Id: <1427933636.1888890.248325033.0A76BE0D@webmail.messagingengine.com>
Date:	Thu, 02 Apr 2015 02:13:56 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Daniel Borkmann <daniel@...earbox.net>, stephen@...workplumber.org
Cc:	ast@...mgrid.com, jiri@...nulli.us, tgraf@...g.ch,
	netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH iproute2 -next] tc,
 bpf: finalize eBPF support for cls and act front-end

Hi Daniel,

On Tue, Mar 31, 2015, at 00:35, Daniel Borkmann wrote:
> This work finalizes both eBPF front-ends for the classifier and action
> part in tc, it allows for custom ELF section selection, a simplified tc
> command frontend (while keeping compat), reusing of common maps between
> classifier and actions residing in the same object file, and exporting
> of all map fds to an eBPF agent for handing off further control in user
> space.
> 
> It also adds an extensive example of how eBPF can be used, and a minimal
> self-contained example agent that dumps map data. The example is well
> documented and hopefully provides a good starting point into programming
> cls_bpf and act_bpf.
> 
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Jiri Pirko <jiri@...nulli.us>
> Cc: Jamal Hadi Salim <jhs@...atatu.com>

(I talked to Daniel about this already but maybe just to get more people
involved on how to handle maps in future, my yet unfinished proposal)

I think this is going into the right direction.

In the end I would also love to see a way to interactively query/update
the bpf maps. I think not a lot would be needed to do that:

Maybe a small utility programs like:

bpf (--lookup|--update|--delete|--get-next-key) -fd
filedescriptor-number (type conversion parameters here) key [value]

So it can be easily used by shell scripts.

For that the filedescriptor numbers would need to be exported (already
opened) into a spawned shell and the numbers could be specified either
in environment or just by printing text which can be sourced by shells
(we already talked about the maybe exec 5</proc/pid/fd/1234 idea). Seems
this can be just build ontop this current patch by extending the
bpf-agent you already build, no?

Otherwise, may I suggest to give C-files which should be used by llvm
--emit bpf another file extension, like .ebpf (or put together some
initials :) )?

Nice work! Thanks!
Hannes
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