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

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Message-ID: <6628387d-cf89-573f-7b9c-2d49ef19634e@netronome.com>
Date:   Wed, 7 Nov 2018 21:34:58 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Jakub Kicinski <jakub.kicinski@...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

2018-11-07 12:32 UTC-0800 ~ Jakub Kicinski <jakub.kicinski@...ronome.com>
> 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).

Not constructing the prog array, I don't think this should be the role 
of bpftool either. Much more a "mass pin", so that you have a link to 
each program loaded from the object file and can later add them to a 
prog array map with subsequent calls to bpftool.