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From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: Toshiaki Makita <toshiaki.makita1@gmail.com>
Cc: Stanislav Fomichev <sdf@fomichev.me>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Jiri Pirko <jiri@resnulli.us>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	William Tu <u9012063@gmail.com>
Subject: Re: [RFC PATCH bpf-next 00/14] xdp_flow: Flow offload to XDP
Date: Fri, 16 Aug 2019 11:52:24 -0700
Message-ID: <20190816115224.6aafd4ee@cakuba.netronome.com> (raw)
In-Reply-To: <da840b14-ab5b-91f1-df2f-6bdd0ed41173@gmail.com>

On Fri, 16 Aug 2019 10:28:10 +0900, Toshiaki Makita wrote:
> On 2019/08/16 4:22, Jakub Kicinski wrote:
> > There's a certain allure in bringing the in-kernel BPF translation
> > infrastructure forward. OTOH from system architecture perspective IMHO
> > it does seem like a task best handed in user space. bpfilter can replace
> > iptables completely, here we're looking at an acceleration relatively
> > loosely coupled with flower.  
> 
> I don't think it's loosely coupled. Emulating TC behavior in userspace
> is not so easy.
> 
> Think about recent multi-mask support in flower. Previously userspace could
> assume there is one mask and hash table for each preference in TC. After the
> change TC accepts different masks with the same pref. Such a change tends to
> break userspace emulation. It may ignore masks passed from flow insertion
> and use the mask remembered when the first flow of the pref is inserted. It
> may override the mask of all existing flows with the pref. It may fail to
> insert such flows. Any of them would result in unexpected wrong datapath
> handling which is critical.
> I think such an emulation layer needs to be updated in sync with TC.

Oh, so you're saying that if xdp_flow is merged all patches to
cls_flower and netfilter which affect flow offload will be required 
to update xdp_flow as well?

That's a question of policy. Technically the implementation in user
space is equivalent.

The advantage of user space implementation is that you can add more
to it and explore use cases which do not fit in the flow offload API,
but are trivial for BPF. Not to mention the obvious advantage of
decoupling the upgrade path.


Personally I'm not happy with the way this patch set messes with the
flow infrastructure. You should use the indirect callback
infrastructure instead, and that way you can build the whole thing
touching none of the flow offload core.

  reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-13 12:05 Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 01/14] xdp_flow: Add skeleton of XDP based TC offload driver Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 02/14] xdp_flow: Add skeleton bpf program for XDP Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 03/14] bpf: Add API to get program from id Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 04/14] xdp_flow: Attach bpf prog to XDP in kernel after UMH loaded program Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 05/14] xdp_flow: Prepare flow tables in bpf Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 06/14] xdp_flow: Add flow entry insertion/deletion logic in UMH Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 07/14] xdp_flow: Add flow handling and basic actions in bpf prog Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 08/14] xdp_flow: Implement flow replacement/deletion logic in xdp_flow kmod Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 09/14] xdp_flow: Add netdev feature for enabling TC flower offload to XDP Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 10/14] xdp_flow: Implement redirect action Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 11/14] xdp_flow: Implement vlan_push action Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 12/14] bpf, selftest: Add test for xdp_flow Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 13/14] i40e: prefetch xdp->data before running XDP prog Toshiaki Makita
2019-08-13 12:05 ` [RFC PATCH bpf-next 14/14] bpf, hashtab: Compare keys in long Toshiaki Makita
2019-08-14  1:44 ` [RFC PATCH bpf-next 00/14] xdp_flow: Flow offload to XDP Alexei Starovoitov
2019-08-14  7:33   ` Toshiaki Makita
2019-08-15 10:59     ` Toshiaki Makita
2019-08-14 17:07 ` Stanislav Fomichev
2019-08-15 10:26   ` Toshiaki Makita
2019-08-15 15:21     ` Stanislav Fomichev
2019-08-15 19:22       ` Jakub Kicinski
2019-08-16  1:28         ` Toshiaki Makita
2019-08-16 18:52           ` Jakub Kicinski [this message]
2019-08-17 14:01             ` Toshiaki Makita
2019-08-19 18:15               ` Jakub Kicinski
2019-08-21  8:49                 ` Toshiaki Makita
2019-08-21 18:38                   ` Jakub Kicinski
2019-08-16 15:59         ` Stanislav Fomichev
2019-08-16 16:20           ` Stanislav Fomichev
2019-08-16  1:09       ` Toshiaki Makita
2019-08-16 15:35         ` Stanislav Fomichev
2019-08-17 14:10           ` Toshiaki Makita
2019-08-15 15:46 ` William Tu
2019-08-16  1:38   ` Toshiaki Makita

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