From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH bpf-next 2/3] bpf: btf: add btf json print functionality Date: Wed, 27 Jun 2018 14:56:49 +0200 Message-ID: <0360a47f-1056-3117-31ec-7c3f5d6dbccb@iogearbox.net> References: <20180622205535.c6vjhdwt5er4wc32@kafai-mbp.dhcp.thefacebook.com> <20180622142743.2b890d0f@cakuba.netronome.com> <20180622225408.jor7lpvsksnwiiec@kafai-mbp.dhcp.thefacebook.com> <20180622163200.20564ec4@cakuba.netronome.com> <20180623002639.h4qxy7aakypi6t7b@kafai-mbp.dhcp.thefacebook.com> <20180626164820.GA12981@w1t1fb> <20180626133133.618af1d3@cakuba.netronome.com> <20180626222709.fsznwqauxojhhx7v@kafai-mbp.dhcp.thefacebook.com> <20180626153559.0511f709@cakuba.netronome.com> <23968d53-2895-f0bc-a38c-5bc99e1846ab@iogearbox.net> <20180627114737.GA1580@w1t1fb> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Jakub Kicinski , Martin KaFai Lau , Alexei Starovoitov , Yonghong Song , Quentin Monnet , "David S. Miller" , netdev@vger.kernel.org, kernel-team@fb.com, linux-kernel@vger.kernel.org To: Okash Khawaja Return-path: In-Reply-To: <20180627114737.GA1580@w1t1fb> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 06/27/2018 01:47 PM, Okash Khawaja wrote: > On Wed, Jun 27, 2018 at 12:34:35PM +0200, Daniel Borkmann wrote: >> On 06/27/2018 12:35 AM, Jakub Kicinski wrote: >>> On Tue, 26 Jun 2018 15:27:09 -0700, Martin KaFai Lau wrote: >>>> On Tue, Jun 26, 2018 at 01:31:33PM -0700, Jakub Kicinski wrote: >> [...] >>>>> Implementing both outputs in one series will help you structure your >>>>> code to best suit both of the formats up front. >>>> hex and "formatted" are the only things missing? As always, things >>>> can be refactored when new use case comes up. Lets wait for >>>> Okash input. >>>> >>>> Regardless, plaintext is our current use case. Having the current >>>> patchset in does not stop us or others from contributing other use >>>> cases (json, "bpftool map find"...etc), and IMO it is actually >>>> the opposite. Others may help us get there faster than us alone. >>>> We should not stop making forward progress and take this patch >>>> as hostage because "abc" and "xyz" are not done together. >>> >>> Parity between JSON and plain text output is non negotiable. >> >> Longish discussion and some confusion in this thread. :-) First of all >> thanks a lot for working on it, very useful! > Thanks :) > >> My $0.02 on it is that so far >> great care has been taken in bpftool to indeed have feature parity between >> JSON and plain text, so it would be highly desirable to keep continuing >> this practice if the consensus is that it indeed is feasible and makes >> sense wrt BTF data. There has been mentioned that given BTF data can be >> dynamic depending on what the user loads via bpf(2) so a potential JSON >> output may look different/break each time anyway. This however could all be >> embedded under a container object that has a fixed key like 'formatted' >> where tools like jq(1) can query into it. I think this would be fine since >> the rest of the (non-dynamic) output is still retained as-is and then >> wouldn't confuse or collide with existing users, and anyone programmatically >> parsing deeper into the BTF data under such JSON container object needs >> to have awareness of what specific data it wants to query from it; so >> there's no conflict wrt breaking anything here. Imho, both outputs would >> be very valuable. > Okay I can add "formatted" object under json output. > > One thing to note here is that the fixed output will change if the map > itself changes. So someone writing a program that consumes that fixed > output will have to account for his program breaking in future, thus Yes, that aspect is fine though, any program/script parsing this would need to be aware of the underlying map type to make sense of it (e.g. per-cpu vs non per-cpu maps to name one). But that info it could query/verify already beforehand via bpftool as well (via normal map info dump for a given id). > breaking backward compatibility anyway as far as the developer is > concerned :) > > I will go ahead with work on "formatted" object. Cool, thanks, Daniel