From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
John Fastabend <john.fastabend@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
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>, Andrii Nakryiko <andriin@fb.com>,
"David S. Miller" <davem@davemloft.net>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Lorenz Bauer <lmb@cloudflare.com>, Andrey Ignatov <rdna@fb.com>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next 1/4] xdp: Support specifying expected existing program when attaching XDP
Date: Wed, 25 Mar 2020 11:42:57 +0100 [thread overview]
Message-ID: <87wo78pvf2.fsf@toke.dk> (raw)
In-Reply-To: <20200325013631.vuncsvkivexdb3fr@ast-mbp>
Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
> On Tue, Mar 24, 2020 at 12:22:47PM -0700, John Fastabend wrote:
>> >
>> > Well, I wasn't talking about any of those subsystems, I was talking
>> > about networking :)
>>
>> My experience has been that networking in the strict sense of XDP no
>> longer exists on its own without cgroups, flow dissector, sockops,
>> sockmap, tracing, etc. All of these pieces are built, patched, loaded,
>> pinned and otherwise managed and manipulated as BPF objects via libbpf.
>>
>> Because I have all this infra in place for other items its a bit odd
>> imo to drop out of BPF apis to then swap a program differently in the
>> XDP case from how I would swap a program in any other place. I'm
>> assuming ability to swap links will be enabled at some point.
>>
>> Granted it just means I have some extra functions on the side to manage
>> the swap similar to how 'qdisc' would be handled today but still not as
>> nice an experience in my case as if it was handled natively.
>>
>> Anyways the netlink API is going to have to call into the BPF infra
>> on the kernel side for verification, etc so its already not pure
>> networking.
>>
>> >
>> > In particular, networking already has a consistent and fairly
>> > well-designed configuration mechanism (i.e., netlink) that we are
>> > generally trying to move more functionality *towards* not *away from*
>> > (see, e.g., converting ethtool to use netlink).
>>
>> True. But BPF programs are going to exist and interop with other
>> programs not exactly in the networking space. Actually library calls
>> might be used in tracing, cgroups, and XDP side. It gets a bit more
>> interesting if the "same" object file (with some patching) runs in both
>> XDP and sockops land for example.
>
> Thanks John for summarizing it very well.
> It looks to me that netlink proponents fail to realize that "bpf for
> networking" goes way beyond what netlink is doing and capable of doing in the
> future. BPF_*_INET_* progs do core networking without any smell of netlink
> anywhere. "But, but, but, netlink is the way to configure networking"... is
> simply not true.
That was not what I was saying. Obviously there are other components to
the networking stack than netlink.
What I'm saying is that netlink is the interface the kernel uses to
*configure network devices*. And that attaching an XDP program is a
network device configuration operation. I mean, it:
- Relies on the RTNL lock for synchronisation
- Fundamentally alters the flow of network packets on the device
- Potentially has side effects like link up/down, HWQ reconfig etc
I'm wondering if there's a way to reconcile these views? Maybe making
the bpf_link attachment work by passing the link fd to the netlink API?
That would keep the network interface configuration over netlink, but
would still allow a BPF application to swap out "its" programs via the
bpf_link APIs?
-Toke
next prev parent reply other threads:[~2020-03-25 10:43 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-19 13:13 [PATCH bpf-next 0/4] XDP: Support atomic replacement of XDP interface attachments Toke Høiland-Jørgensen
2020-03-19 13:13 ` [PATCH bpf-next 1/4] xdp: Support specifying expected existing program when attaching XDP Toke Høiland-Jørgensen
2020-03-19 22:52 ` Jakub Kicinski
2020-03-20 8:48 ` Toke Høiland-Jørgensen
2020-03-20 17:35 ` Jakub Kicinski
2020-03-20 18:17 ` Toke Høiland-Jørgensen
2020-03-20 18:35 ` Jakub Kicinski
2020-03-20 18:30 ` John Fastabend
2020-03-20 20:24 ` Andrii Nakryiko
2020-03-23 11:24 ` Toke Høiland-Jørgensen
2020-03-23 16:54 ` Jakub Kicinski
2020-03-23 18:14 ` Andrii Nakryiko
2020-03-23 19:23 ` Toke Høiland-Jørgensen
2020-03-24 1:01 ` David Ahern
2020-03-24 4:53 ` Andrii Nakryiko
2020-03-24 20:55 ` David Ahern
2020-03-24 22:56 ` Andrii Nakryiko
2020-03-24 5:00 ` Andrii Nakryiko
2020-03-24 10:57 ` Toke Høiland-Jørgensen
2020-03-24 18:53 ` Jakub Kicinski
2020-03-24 22:30 ` Andrii Nakryiko
2020-03-25 1:25 ` Jakub Kicinski
2020-03-24 19:22 ` John Fastabend
2020-03-25 1:36 ` Alexei Starovoitov
2020-03-25 2:15 ` Jakub Kicinski
2020-03-25 18:06 ` Alexei Starovoitov
2020-03-25 18:20 ` Jakub Kicinski
2020-03-25 19:14 ` Alexei Starovoitov
2020-03-25 10:42 ` Toke Høiland-Jørgensen [this message]
2020-03-25 18:11 ` Alexei Starovoitov
2020-03-25 10:30 ` Toke Høiland-Jørgensen
2020-03-25 17:56 ` Alexei Starovoitov
2020-03-24 22:25 ` Andrii Nakryiko
2020-03-25 9:38 ` Toke Høiland-Jørgensen
2020-03-25 17:55 ` Alexei Starovoitov
2020-03-26 0:16 ` Andrii Nakryiko
2020-03-26 5:13 ` Jakub Kicinski
2020-03-26 18:09 ` Andrii Nakryiko
2020-03-26 19:40 ` Alexei Starovoitov
2020-03-26 20:05 ` Edward Cree
2020-03-27 11:09 ` Lorenz Bauer
2020-03-27 23:11 ` Alexei Starovoitov
2020-03-26 10:04 ` Lorenz Bauer
2020-03-26 17:47 ` Jakub Kicinski
2020-03-26 19:45 ` Alexei Starovoitov
2020-03-26 18:18 ` Andrii Nakryiko
2020-03-26 19:53 ` Alexei Starovoitov
2020-03-27 11:11 ` Toke Høiland-Jørgensen
2020-04-02 20:21 ` bpf: ability to attach freplace to multiple parents Alexei Starovoitov
2020-04-02 21:23 ` Toke Høiland-Jørgensen
2020-04-02 21:54 ` Alexei Starovoitov
2020-04-03 8:38 ` Toke Høiland-Jørgensen
2020-04-07 1:44 ` Alexei Starovoitov
2020-04-07 9:20 ` Toke Høiland-Jørgensen
2020-05-12 8:34 ` Toke Høiland-Jørgensen
2020-05-12 9:53 ` Alan Maguire
2020-05-12 13:02 ` Toke Høiland-Jørgensen
2020-05-12 23:18 ` Alexei Starovoitov
2020-05-12 23:06 ` Alexei Starovoitov
2020-05-13 10:25 ` Toke Høiland-Jørgensen
2020-04-02 21:24 ` Andrey Ignatov
2020-04-02 22:01 ` Alexei Starovoitov
2020-03-26 12:35 ` [PATCH bpf-next 1/4] xdp: Support specifying expected existing program when attaching XDP Toke Høiland-Jørgensen
2020-03-26 19:06 ` Andrii Nakryiko
2020-03-27 11:06 ` Lorenz Bauer
2020-03-27 16:12 ` David Ahern
2020-03-27 20:10 ` Andrii Nakryiko
2020-03-27 23:02 ` Alexei Starovoitov
2020-03-30 15:25 ` Edward Cree
2020-03-31 3:43 ` Alexei Starovoitov
2020-03-31 22:05 ` Edward Cree
2020-03-31 22:16 ` Alexei Starovoitov
2020-03-27 19:42 ` Andrii Nakryiko
2020-03-27 19:45 ` Andrii Nakryiko
2020-03-27 23:09 ` Alexei Starovoitov
2020-03-27 11:46 ` Toke Høiland-Jørgensen
2020-03-27 20:07 ` Andrii Nakryiko
2020-03-27 22:16 ` Toke Høiland-Jørgensen
2020-03-27 22:54 ` Andrii Nakryiko
2020-03-28 1:09 ` Toke Høiland-Jørgensen
2020-03-28 1:44 ` Andrii Nakryiko
2020-03-28 19:43 ` Toke Høiland-Jørgensen
2020-03-26 19:58 ` Alexei Starovoitov
2020-03-27 12:06 ` Toke Høiland-Jørgensen
2020-03-27 23:00 ` Alexei Starovoitov
2020-03-28 1:43 ` Toke Høiland-Jørgensen
2020-03-28 2:26 ` Alexei Starovoitov
2020-03-28 19:34 ` Toke Høiland-Jørgensen
2020-03-28 23:35 ` Alexei Starovoitov
2020-03-29 10:39 ` Toke Høiland-Jørgensen
2020-03-29 19:26 ` Alexei Starovoitov
2020-03-30 10:19 ` Toke Høiland-Jørgensen
2020-03-29 20:23 ` Andrii Nakryiko
2020-03-30 13:53 ` Toke Høiland-Jørgensen
2020-03-30 20:17 ` Andrii Nakryiko
2020-03-31 10:13 ` Toke Høiland-Jørgensen
2020-03-31 13:48 ` Daniel Borkmann
2020-03-31 15:00 ` Toke Høiland-Jørgensen
2020-03-31 20:19 ` Andrii Nakryiko
2020-03-31 20:15 ` Andrii Nakryiko
2020-03-30 15:41 ` Edward Cree
2020-03-30 19:13 ` Jakub Kicinski
2020-03-31 4:01 ` Alexei Starovoitov
2020-03-31 11:34 ` Toke Høiland-Jørgensen
2020-03-31 18:52 ` Alexei Starovoitov
2020-03-20 20:30 ` Daniel Borkmann
2020-03-20 20:40 ` Daniel Borkmann
2020-03-20 21:30 ` Jakub Kicinski
2020-03-20 21:55 ` Daniel Borkmann
2020-03-20 23:35 ` Jakub Kicinski
2020-03-20 20:39 ` Andrii Nakryiko
2020-03-23 11:25 ` Toke Høiland-Jørgensen
2020-03-23 18:07 ` Andrii Nakryiko
2020-03-23 23:54 ` Andrey Ignatov
2020-03-24 10:16 ` Toke Høiland-Jørgensen
2020-03-20 2:13 ` Yonghong Song
2020-03-20 8:48 ` Toke Høiland-Jørgensen
2020-03-19 13:13 ` [PATCH bpf-next 2/4] tools: Add EXPECTED_FD-related definitions in if_link.h Toke Høiland-Jørgensen
2020-03-19 13:13 ` [PATCH bpf-next 3/4] libbpf: Add function to set link XDP fd while specifying old fd Toke Høiland-Jørgensen
2020-03-19 13:13 ` [PATCH bpf-next 4/4] selftests/bpf: Add tests for attaching XDP programs Toke Høiland-Jørgensen
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