netdev - Re: [PATCH RFC 0/4] net: add bpfilter

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Message-ID: <20180219145935.GE6333@breakpoint.cc>
Date:   Mon, 19 Feb 2018 15:59:35 +0100
From:   Florian Westphal <fw@...len.de>
To:     David Miller <davem@...emloft.net>
Cc:     daniel@...earbox.net, laforge@...monks.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH RFC 0/4] net: add bpfilter

David Miller <davem@...emloft.net> wrote:
> From: Daniel Borkmann <daniel@...earbox.net>
> Date: Mon, 19 Feb 2018 13:03:17 +0100
> 
> > Thought was that it would be more suitable to push all the complexity of
> > such translation into user space which brings couple of additional advantages
> > as well: the translation can become very complex and thus it would contain
> > all of it behind syscall boundary where natural path of loading programs
> > would go via verifier. Given the tool would reside in user space, it would
> > also allow to ease development and testing can happen w/o recompiling the
> > kernel. It would allow for all the clang sanitizers to run there and for
> > having a comprehensive test suite to verify and dry test translations against
> > traffic test patterns (e.g. bpf infra would provide possibilities on this
> > w/o complex setup). Given normal user mode helpers make this rather painful
> > since they need to be shipped as extra package by the various distros, the
> > idea was that the module loader back end could treat umh similarly as kernel
> > modules and hook them in through request_module() approach while still
> > operating out of user space. In any case, I could image this approach might
> > be interesting and useful in general also for other subsystems requiring
> > umh in one way or another.
> 
> Yes, this is a very powerful new facility.
> 
> It also means that the scope of developers who can contribute and work
> on the translater is much larger.

How so?  Translator is in userspace in nftables case too?