netdev - Re: [PATCH bpf-next 2/2] bpftool: support loading flow dissector

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Date:   Wed, 7 Nov 2018 12:32:31 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Quentin Monnet <quentin.monnet@...ronome.com>
Cc:     Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        linux-kselftest@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, shuah@...nel.org, guro@...com,
        jiong.wang@...ronome.com, bhole_prashant_q7@....ntt.co.jp,
        john.fastabend@...il.com, jbenc@...hat.com,
        treeze.taeung@...il.com, yhs@...com, osk@...com,
        sandipan@...ux.vnet.ibm.com
Subject: Re: [PATCH bpf-next 2/2] bpftool: support loading flow dissector

On Wed, 7 Nov 2018 20:08:53 +0000, Quentin Monnet wrote:
> > +		err = bpf_obj_pin(bpf_program__fd(prog), pinfile);
> > +		if (err) {
> > +			p_err("failed to pin program %s",
> > +			      bpf_program__title(prog, false));
> > +			goto err_close_obj;
> > +		}  
> 
> I don't have the same opinion as Jakub for pinning :). I was hoping we
> could also load additional programs (for tail calls) for
> non-flow_dissector programs. Could this be an occasion to update the
> code in that direction?

Do you mean having the bpftool construct an array for tail calling
automatically when loading an object?  Or do a "mass pin" of all
programs in an object file?

I'm not convinced about this strategy of auto assembling a tail call
array by assuming that a flow dissector object carries programs for
protocols in order (apart from the main program which doesn't have to
be first, for some reason).