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From: Jakub Sitnicki <jakub@cloudflare.com>
To: Martin KaFai Lau <kafai@fb.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	dccp@vger.kernel.org, kernel-team@cloudflare.com,
	Alexei Starovoitov <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Gerrit Renker <gerrit@erg.abdn.ac.uk>,
	Jakub Kicinski <kuba@kernel.org>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Marek Majkowski <marek@cloudflare.com>,
	"Lorenz Bauer" <lmb@cloudflare.com>
Subject: Re: [PATCH bpf-next v2 02/17] bpf: Introduce SK_LOOKUP program type with a dedicated attach point
Date: Wed, 13 May 2020 16:34:13 +0200	[thread overview]
Message-ID: <87wo5fucnu.fsf@cloudflare.com> (raw)
In-Reply-To: <20200513054121.qztevjyfkc2ltcvp@kafai-mbp.dhcp.thefacebook.com>

On Wed, May 13, 2020 at 07:41 AM CEST, Martin KaFai Lau wrote:
> On Mon, May 11, 2020 at 08:52:03PM +0200, Jakub Sitnicki wrote:
>
> [ ... ]
>
>> +BPF_CALL_3(bpf_sk_lookup_assign, struct bpf_sk_lookup_kern *, ctx,
>> +	   struct sock *, sk, u64, flags)
> The SK_LOOKUP bpf_prog may have already selected the proper reuseport sk.
> It is possible by looking up sk from sock_map.
>
> Thus, it is not always desired to do lookup_reuseport() after sk_assign()
> in patch 5.  e.g. reuseport_select_sock() just uses a normal hash if
> there is no reuse->prog.
>
> A flag (e.g. "BPF_F_REUSEPORT_SELECT") can be added here to
> specifically do the reuseport_select_sock() after sk_assign().
> If not set, reuseport_select_sock() should not be called.

That's true that in addition to steering connections to different
services with SK_LOOKUP, you could also, in the same program,
load-balance among sockets belonging to one service.

So skipping the reuseport socket selection, if sk_lookup already did
load-balancing sounds useful.

Thinking about our use-case, I think we would always pass
BPF_F_REUSEPORT_SELECT to sk_assign() because we either (i) know that
application is using reuseport and want it manage the load-balancing
socket group by itself, or (ii) don't know if application is using
reuseport and don't want to break expected behavior.

IOW, we'd like reuseport selection to run by default because application
expects it to happen if it was set up. OTOH, the application doesn't
have to be aware that there is sk_lookup attached (we can put one of its
sockets in sk_lookup SOCKMAP when systemd activates it).

Beacuse of that I'd be in favor of having a flag for sk_assign() that
disables reuseport selection on demand.

WDYT?

WARNING: multiple messages have this Message-ID (diff)
From: Jakub Sitnicki <jakub@cloudflare.com>
To: dccp@vger.kernel.org
Subject: Re: [PATCH bpf-next v2 02/17] bpf: Introduce SK_LOOKUP program type with a dedicated attach point
Date: Wed, 13 May 2020 14:34:13 +0000	[thread overview]
Message-ID: <87wo5fucnu.fsf@cloudflare.com> (raw)
In-Reply-To: <20200511185218.1422406-3-jakub@cloudflare.com>

On Wed, May 13, 2020 at 07:41 AM CEST, Martin KaFai Lau wrote:
> On Mon, May 11, 2020 at 08:52:03PM +0200, Jakub Sitnicki wrote:
>
> [ ... ]
>
>> +BPF_CALL_3(bpf_sk_lookup_assign, struct bpf_sk_lookup_kern *, ctx,
>> +	   struct sock *, sk, u64, flags)
> The SK_LOOKUP bpf_prog may have already selected the proper reuseport sk.
> It is possible by looking up sk from sock_map.
>
> Thus, it is not always desired to do lookup_reuseport() after sk_assign()
> in patch 5.  e.g. reuseport_select_sock() just uses a normal hash if
> there is no reuse->prog.
>
> A flag (e.g. "BPF_F_REUSEPORT_SELECT") can be added here to
> specifically do the reuseport_select_sock() after sk_assign().
> If not set, reuseport_select_sock() should not be called.

That's true that in addition to steering connections to different
services with SK_LOOKUP, you could also, in the same program,
load-balance among sockets belonging to one service.

So skipping the reuseport socket selection, if sk_lookup already did
load-balancing sounds useful.

Thinking about our use-case, I think we would always pass
BPF_F_REUSEPORT_SELECT to sk_assign() because we either (i) know that
application is using reuseport and want it manage the load-balancing
socket group by itself, or (ii) don't know if application is using
reuseport and don't want to break expected behavior.

IOW, we'd like reuseport selection to run by default because application
expects it to happen if it was set up. OTOH, the application doesn't
have to be aware that there is sk_lookup attached (we can put one of its
sockets in sk_lookup SOCKMAP when systemd activates it).

Beacuse of that I'd be in favor of having a flag for sk_assign() that
disables reuseport selection on demand.

WDYT?

  reply	other threads:[~2020-05-13 14:34 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-11 18:52 [PATCH bpf-next v2 00/17] Run a BPF program on socket lookup Jakub Sitnicki
2020-05-11 18:52 ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 01/17] flow_dissector: Extract attach/detach/query helpers Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 02/17] bpf: Introduce SK_LOOKUP program type with a dedicated attach point Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 19:06   ` Jakub Sitnicki
2020-05-11 19:06     ` Jakub Sitnicki
2020-05-13  5:41   ` Martin KaFai Lau
2020-05-13  5:41     ` Martin KaFai Lau
2020-05-13 14:34     ` Jakub Sitnicki [this message]
2020-05-13 14:34       ` Jakub Sitnicki
2020-05-13 18:10       ` Martin KaFai Lau
2020-05-13 18:10         ` Martin KaFai Lau
2020-05-11 18:52 ` [PATCH bpf-next v2 03/17] inet: Store layer 4 protocol in inet_hashinfo Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 04/17] inet: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 05/17] inet: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 20:44   ` Alexei Starovoitov
2020-05-11 20:44     ` Alexei Starovoitov
2020-05-12 13:52     ` Jakub Sitnicki
2020-05-12 13:52       ` Jakub Sitnicki
2020-05-12 23:58       ` Alexei Starovoitov
2020-05-12 23:58         ` Alexei Starovoitov
2020-05-13 13:55         ` Jakub Sitnicki
2020-05-13 13:55           ` Jakub Sitnicki
2020-05-13 14:21       ` Lorenz Bauer
2020-05-13 14:21         ` Lorenz Bauer
2020-05-13 14:50         ` Jakub Sitnicki
2020-05-13 14:50           ` Jakub Sitnicki
2020-05-15 12:28     ` Jakub Sitnicki
2020-05-15 12:28       ` Jakub Sitnicki
2020-05-15 15:07       ` Alexei Starovoitov
2020-05-15 15:07         ` Alexei Starovoitov
2020-05-11 18:52 ` [PATCH bpf-next v2 06/17] inet6: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 07/17] inet6: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 08/17] udp: Store layer 4 protocol in udp_table Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 09/17] udp: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 10/17] udp: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 11/17] udp6: Extract helper for selecting socket from reuseport group Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 12/17] udp6: Run SK_LOOKUP BPF program on socket lookup Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 13/17] bpf: Sync linux/bpf.h to tools/ Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 14/17] libbpf: Add support for SK_LOOKUP program type Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 15/17] selftests/bpf: Add verifier tests for bpf_sk_lookup context access Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 16/17] selftests/bpf: Rename test_sk_lookup_kern.c to test_ref_track_kern.c Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 18:52 ` [PATCH bpf-next v2 17/17] selftests/bpf: Tests for BPF_SK_LOOKUP attach point Jakub Sitnicki
2020-05-11 18:52   ` Jakub Sitnicki
2020-05-11 19:45 ` [PATCH bpf-next v2 00/17] Run a BPF program on socket lookup Martin KaFai Lau
2020-05-11 19:45   ` Martin KaFai Lau
2020-05-12 11:57   ` Jakub Sitnicki
2020-05-12 11:57     ` Jakub Sitnicki
2020-05-12 16:34     ` Martin KaFai Lau
2020-05-12 16:34       ` Martin KaFai Lau
2020-05-13 17:54       ` Jakub Sitnicki
2020-05-13 17:54         ` Jakub Sitnicki

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