netdev - Re: [RFC PATCH v2 bpf-next 00/15] xdp

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Message-ID: <87zhhmrz7w.fsf@toke.dk>
Date:   Sun, 27 Oct 2019 16:21:23 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Toshiaki Makita <toshiaki.makita1@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Pravin B Shelar <pshelar@....org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        William Tu <u9012063@...il.com>,
        Stanislav Fomichev <sdf@...ichev.me>
Subject: Re: [RFC PATCH v2 bpf-next 00/15] xdp_flow: Flow offload to XDP

Toshiaki Makita <toshiaki.makita1@...il.com> writes:

>> Yeah, you are right that it's something we're thinking about. I'm not
>> sure we'll actually have the bandwidth to implement a complete solution
>> ourselves, but we are very much interested in helping others do this,
>> including smoothing out any rough edges (or adding missing features) in
>> the core XDP feature set that is needed to achieve this :)
>
> I'm very interested in general usability solutions.
> I'd appreciate if you could join the discussion.
>
> Here the basic idea of my approach is to reuse HW-offload infrastructure 
> in kernel.
> Typical networking features in kernel have offload mechanism (TC flower, 
> nftables, bridge, routing, and so on).
> In general these are what users want to accelerate, so easy XDP use also 
> should support these features IMO. With this idea, reusing existing 
> HW-offload mechanism is a natural way to me. OVS uses TC to offload 
> flows, then use TC for XDP as well...

I agree that XDP should be able to accelerate existing kernel
functionality. However, this does not necessarily mean that the kernel
has to generate an XDP program and install it, like your patch does.
Rather, what we should be doing is exposing the functionality through
helpers so XDP can hook into the data structures already present in the
kernel and make decisions based on what is contained there. We already
have that for routing; L2 bridging, and some kind of connection
tracking, are obvious contenders for similar additions.

-Toke