From: Jesper Dangaard Brouer <brouer@redhat.com>
To: "Maciej Żenczykowski" <maze@google.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
Linux NetDev <netdev@vger.kernel.org>,
Daniel Borkmann <borkmann@iogearbox.net>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Lorenz Bauer <lmb@cloudflare.com>,
Shaun Crampton <shaun@tigera.io>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Marek Majkowski <marek@cloudflare.com>,
John Fastabend <john.fastabend@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
Eyal Birger <eyal.birger@gmail.com>,
brouer@redhat.com
Subject: Re: [PATCH bpf-next V3 4/6] bpf: make it possible to identify BPF redirected SKBs
Date: Sat, 10 Oct 2020 13:09:38 +0200 [thread overview]
Message-ID: <20201010130938.138c80d9@carbon> (raw)
In-Reply-To: <CANP3RGesHkCNTWsWDoU2uJsFjZ4dgnEpp+F-iEmhb9U0-rcT_w@mail.gmail.com>
On Fri, 9 Oct 2020 11:33:33 -0700
Maciej Żenczykowski <maze@google.com> wrote:
> > > This change makes it possible to identify SKBs that have been redirected
> > > by TC-BPF (cls_act). This is needed for a number of cases.
> > >
> > > (1) For collaborating with driver ifb net_devices.
> > > (2) For avoiding starting generic-XDP prog on TC ingress redirect.
> > >
> > > Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> >
> > Not sure if anyone actually cares about ifb devices, but my worry is that the
> > generic XDP vs tc interaction has been as-is for quite some time so this change
> > in behavior could break in the wild.
No, I believe this happened as recent at kernel v5.2, when Stephen
Hemminger changed this in commit 458bf2f224f0 ("net: core: support XDP
generic on stacked devices."). And for the record I think that
patch/change was a mistake, as people should not use generic-XDP for
these kind of stacked devices (they should really use TC-BPF as that is
the right tool for the job).
> I'm not at all sure of the interactions/implications here.
> But I do have a request to enable ifb on Android for ingress rate
> limiting and separately we're trying to make XDP work...
> So we might at some point end up with cellular interfaces with xdp
> ebpf (redirect for forwarding/nat/tethering) + ifb + tc ebpf (for
> device local stuff).
To me I was very surprised when I discovered tc-redirect didn't work
with ifb driver. And it sounds like you have an actual use-case for
this on Android.
> But this is still all very vague and 'ideas only' level.
> (and in general I think I'd like to get rid of the redirect in tc
> ebpf, and leave only xlat64 translation for to-the-device traffic in
> there, so maybe there's no problem anyway??)
I know it sounds strange coming from me "Mr.XDP", but I actaully think
that in many cases you will be better off with using TC-BPF.
Especially on Android, as it will be very hard to get native-XDP
implemented in all these different drivers. (And you don't want to use
generic-XDP, because there is a high chance it causes a reallocation of
the SKB, which is a huge performance hit).
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2020-10-10 22:55 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 14:08 [PATCH bpf-next V3 0/6] bpf: New approach for BPF MTU handling Jesper Dangaard Brouer
2020-10-08 14:09 ` [PATCH bpf-next V3 1/6] bpf: Remove MTU check in __bpf_skb_max_len Jesper Dangaard Brouer
2020-10-09 16:12 ` Daniel Borkmann
2020-10-09 18:26 ` Maciej Żenczykowski
2020-10-10 10:25 ` Jesper Dangaard Brouer
2020-10-08 14:09 ` [PATCH bpf-next V3 2/6] bpf: bpf_fib_lookup return MTU value as output when looked up Jesper Dangaard Brouer
2020-10-09 4:05 ` David Ahern
2020-10-08 14:09 ` [PATCH bpf-next V3 3/6] bpf: add BPF-helper for MTU checking Jesper Dangaard Brouer
2020-10-09 23:29 ` Maciej Żenczykowski
2020-10-21 11:32 ` Jesper Dangaard Brouer
2020-10-12 15:54 ` Lorenz Bauer
2020-10-08 14:09 ` [PATCH bpf-next V3 4/6] bpf: make it possible to identify BPF redirected SKBs Jesper Dangaard Brouer
2020-10-09 16:47 ` Daniel Borkmann
2020-10-09 18:33 ` Maciej Żenczykowski
2020-10-10 11:09 ` Jesper Dangaard Brouer [this message]
2020-10-12 21:04 ` Maciej Żenczykowski
2020-10-08 14:09 ` [PATCH bpf-next V3 5/6] bpf: drop MTU check when doing TC-BPF redirect to ingress Jesper Dangaard Brouer
2020-10-09 23:17 ` Maciej Żenczykowski
2020-10-08 14:09 ` [PATCH bpf-next V3 6/6] net: inline and splitup is_skb_forwardable Jesper Dangaard Brouer
2020-10-09 16:33 ` [PATCH bpf-next V3 0/6] bpf: New approach for BPF MTU handling Jakub Kicinski
2020-10-09 20:49 ` John Fastabend
2020-10-09 21:07 ` Alexei Starovoitov
2020-10-09 21:57 ` Maciej Żenczykowski
2020-10-09 23:00 ` Jakub Kicinski
2020-10-10 10:44 ` Jesper Dangaard Brouer
2020-10-10 16:32 ` Jakub Kicinski
2020-10-10 23:52 ` John Fastabend
2020-10-11 23:30 ` Jakub Kicinski
2020-10-13 20:40 ` Jesper Dangaard Brouer
2020-10-13 23:07 ` Jakub Kicinski
2020-10-13 23:37 ` Alexei Starovoitov
2020-10-13 23:54 ` Maciej Żenczykowski
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