netdev - Re: [flamebait] xdp Was: Re: bpf bounded loops. Was: [flamebait] xdp

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Date:   Mon, 5 Dec 2016 22:04:59 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Tom Herbert <tom@...bertland.com>
Cc:     Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Thomas Graf <tgraf@...g.ch>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [flamebait] xdp Was: Re: bpf bounded loops. Was: [flamebait] xdp

On Mon, Dec 05, 2016 at 09:08:36PM -0800, Tom Herbert wrote:
> On Mon, Dec 5, 2016 at 7:05 PM, Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> > On Sun, Dec 04, 2016 at 05:05:28PM +0100, Hannes Frederic Sowa wrote:
> >>
> >> If one of those eBPF verifiers only accepts a certain number of INSN, as
> >> fundamental as backwards jumps, we might end up with two compiler?
> >
> > two compilers? We already have five. There is gcc bpf backend (unmaintained)
> > and now lua, python and ply project can generate bpf code without llvm.
> > The kernel verifier has to become smarter. Right now it understands
> > only certain instruction patterns which caused all five bpf generators to
> > do extra work to satisfy the verifier. The solution is to do
> > data flow analysis using proper compiler techniques.
> >
> >> program thinks). Ergo, more complexity. What do you do when one of those
> >> two systems fail? What is the reference data? What do you do if on a
> >> highly busy box during DoS constant reloading of your vmalloc happens (I
> >> don't know if it is a problem under DoS)?
> >
> > ddos is one of the key use cases for xdp. If the system is about to oom
> > during ddos, it has to be fixed. The faster we move with xdp development
> > the sooner we will find and fix those issues.
> > And xdp being a core component of the linux kernel we will fix ddos
> > for the whole internet. Anyone going dpdk route are simply in
> > business of selling ddos protection with proprietary solutions.
> >
> Hi Alexei,
> 
> I am wondering exactly how XDP fixes DDOS in a non-proprietary
> fashion. While the XDP infrastructure is part of the core kernel, the
> programs are not part of the kernel as you mention below. So what will
> a DDOS solution based on XDP for the whole Internet look like? Do you
> envision a set of "blessed" DDOS programs that various sites can use
> and configure (maybe some maintained open source repository), or will
> each site need to come up with their own XDP programs for DDOS?

At some point we would need a repository of these 'blessed' programs.
Some of them will not be programs, but program generators
similar to existing Cloudflare bpf setup:
https://github.com/cloudflare/bpftools
and instead of doing things like:
https://github.com/cloudflare/lua-aho-corasick
and reimplementing them in proprietary c++,
the dfa/aho-corasick will be implemented as a kernel helper.
That's what I was alluding to in
https://github.com/iovisor/bcc/issues/471
Then all of the research in that area like:
https://ir.nctu.edu.tw/bitstream/11536/26033/1/000288319400006.pdf
will be applicable and researchers will be sharing
these detector programs.
Of course, not everyone will open up their secret sauce,
but a lot of folks will do and it will drive the innovation.