netdev - Re: [PATCH net-next v2 0/5] bpf: BPF for lightweight tunnel encapsulation

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Message-ID: <CALx6S35_KTHV7Xam68hdj+VkkHz4TxqLL0sQvn_dvZSB8nm4rA@mail.gmail.com>
Date:   Wed, 2 Nov 2016 16:27:35 -0700
From:   Tom Herbert <tom@...bertland.com>
To:     Thomas Graf <tgraf@...g.ch>
Cc:     Hannes Frederic Sowa <hannes@...essinduktion.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        roopa <roopa@...ulusnetworks.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 0/5] bpf: BPF for lightweight tunnel encapsulation

On Wed, Nov 2, 2016 at 3:57 PM, Thomas Graf <tgraf@...g.ch> wrote:
> On 1 November 2016 at 17:07, Tom Herbert <tom@...bertland.com> wrote:
>> On the other hand, I'm not really sure how to implement for this level
>> of performance this in LWT+BPF either. It seems like one way to do
>> that would be to create a program each destination and set it each
>> host. As you point out would create a million different programs which
>> doesn't seem manageable. I don't think the BPF map works either since
>> that implies we need a lookup (?). It seems like what we need is one
>> program but allow it to be parameterized with per destination
>> information saved in the route (LWT structure).
>
> Attaching different BPF programs to millions of unique dsts doesn't
> make any sense. That will obivously will never scale and it's not
> supposed to scale. This is meant to be used for prefixes which
> represent a series of endpoints, f.e. all local containers, all
> non-internal traffic, all vpn traffic, etc. I'm also not sure why we
> are talking about ILA here, you have written a native implementation,
> why would you want to solve it with BPF again?
>
We are talking about ILA because you specifically mentioned that in
overview log as a use case: "ILA like uses cases where L3 addresses
are resolved and then routed".

Tom

> If you want to run a single program for all dsts, feel free to run the
> same BPF program for each dst. Nobody is forcing you to attach
> individual programs.