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From: Jakub Sitnicki <jakub@cloudflare.com>
To: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org, kernel-team@cloudflare.com,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Marek Majkowski <marek@cloudflare.com>
Subject: Re: [PATCH bpf-next v3 04/16] inet: Run SK_LOOKUP BPF program on socket lookup
Date: Mon, 06 Jul 2020 14:06:52 +0200	[thread overview]
Message-ID: <87h7ukj19f.fsf@cloudflare.com> (raw)
In-Reply-To: <20200702092416.11961-5-jakub@cloudflare.com>

On Thu, Jul 02, 2020 at 11:24 AM CEST, Jakub Sitnicki wrote:
> Run a BPF program before looking up a listening socket on the receive path.
> Program selects a listening socket to yield as result of socket lookup by
> calling bpf_sk_assign() helper and returning BPF_REDIRECT (7) code.
>
> Alternatively, program can also fail the lookup by returning with
> BPF_DROP (1), or let the lookup continue as usual with BPF_OK (0) on
> return. Other return values are treated the same as BPF_OK.
>
> This lets the user match packets with listening sockets freely at the last
> possible point on the receive path, where we know that packets are destined
> for local delivery after undergoing policing, filtering, and routing.
>
> With BPF code selecting the socket, directing packets destined to an IP
> range or to a port range to a single socket becomes possible.
>
> In case multiple programs are attached, they are run in series in the order
> in which they were attached. The end result gets determined from return
> code from each program according to following rules.
>
>  1. If any program returned BPF_REDIRECT and selected a valid socket, this
>     socket will be used as result of the lookup.
>  2. If more than one program returned BPF_REDIRECT and selected a socket,
>     last selection takes effect.
>  3. If any program returned BPF_DROP and none returned BPF_REDIRECT, the
>     socket lookup will fail with -ECONNREFUSED.
>  4. If no program returned neither BPF_DROP nor BPF_REDIRECT, socket lookup
>     continues to htable-based lookup.

Lorenz suggested that we cut down the allowed return values to just
BPF_OK (pass) or BPF_DROP, and get rid of BPF_REDIRECT.

Instead of returning BPF_REDIRECT, BPF program will select a socket with
bpf_sk_assign() and return BPF_OK.

Also, program will be able to discard the socket is has selected by
passing NULL to bpf_sk_assign(). This requires a slight change to
verifier in order to support an argument type that is a pointer to full
socket or NULL.

These simplified semantics seem very attractive. They make the the new
type of behave like a filter that can simply pass / drop connection
requests in its basic form. And with a key ability to select an
alternative socket to handle the connection request when bpf_sk_assign()
gets called.

It is also closer to how redirection in TC BPF, SK_SKB and SK_REUSEPORT
programs work. There is no REDIRECT return code expectation there.

We can even go a step further and adopt SK_PASS / SK_DROP as return
values, instead of BPF_OK / BPF_DROP, as they are already in use by
SK_SKB and SK_REUSEPORT programs.

[...]

  parent reply	other threads:[~2020-07-06 12:06 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-02  9:24 [PATCH bpf-next v3 00/16] Run a BPF program on socket lookup Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 01/16] bpf, netns: Handle multiple link attachments Jakub Sitnicki
2020-07-09  3:44   ` Andrii Nakryiko
2020-07-09 12:49     ` Jakub Sitnicki
2020-07-09 22:02       ` Andrii Nakryiko
2020-07-10 19:23         ` Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 02/16] bpf: Introduce SK_LOOKUP program type with a dedicated attach point Jakub Sitnicki
2020-07-04 18:42   ` Yonghong Song
2020-07-06 11:44     ` Jakub Sitnicki
2020-07-05  9:20   ` kernel test robot
2020-07-05  9:20   ` [RFC PATCH] bpf: sk_lookup_prog_ops can be static kernel test robot
2020-07-07  9:21   ` [PATCH bpf-next v3 02/16] bpf: Introduce SK_LOOKUP program type with a dedicated attach point Jakub Sitnicki
2020-07-09  4:08   ` Andrii Nakryiko
2020-07-09 13:25     ` Jakub Sitnicki
2020-07-09 23:09       ` Andrii Nakryiko
2020-07-10  8:55         ` Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 03/16] inet: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 04/16] inet: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-02 10:27   ` Lorenz Bauer
2020-07-02 12:46     ` Jakub Sitnicki
2020-07-02 13:19       ` Lorenz Bauer
2020-07-06 11:24         ` Jakub Sitnicki
2020-07-06 12:06   ` Jakub Sitnicki [this message]
2020-07-02  9:24 ` [PATCH bpf-next v3 05/16] inet6: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 06/16] inet6: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 07/16] udp: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 08/16] udp: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 09/16] udp6: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 10/16] udp6: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-07-02 14:51   ` kernel test robot
2020-07-03 13:04     ` Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 11/16] bpf: Sync linux/bpf.h to tools/ Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 12/16] libbpf: Add support for SK_LOOKUP program type Jakub Sitnicki
2020-07-09  4:23   ` Andrii Nakryiko
2020-07-09 15:51     ` Jakub Sitnicki
2020-07-09 23:13       ` Andrii Nakryiko
2020-07-10  8:37         ` Jakub Sitnicki
2020-07-10 18:55           ` Andrii Nakryiko
2020-07-10 19:24             ` Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 13/16] tools/bpftool: Add name mappings for SK_LOOKUP prog and attach type Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 14/16] selftests/bpf: Add verifier tests for bpf_sk_lookup context access Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 15/16] selftests/bpf: Rename test_sk_lookup_kern.c to test_ref_track_kern.c Jakub Sitnicki
2020-07-02  9:24 ` [PATCH bpf-next v3 16/16] selftests/bpf: Tests for BPF_SK_LOOKUP attach point Jakub Sitnicki
2020-07-02 11:01   ` Lorenz Bauer
2020-07-02 12:59     ` Jakub Sitnicki
2020-07-09  4:28       ` Andrii Nakryiko
2020-07-09 15:54         ` Jakub Sitnicki
2020-07-02 11:05 ` [PATCH bpf-next v3 00/16] Run a BPF program on socket lookup Lorenz Bauer

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