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Miller" , Eric Dumazet , Gerrit Renker , Jakub Kicinski , Andrii Nakryiko , Marek Majkowski , Lorenz Bauer Subject: Re: [PATCH bpf-next v2 02/17] bpf: Introduce SK_LOOKUP program type with a dedicated attach point Message-ID: <20200513181020.dmj3fg3dbvuzl626@kafai-mbp.dhcp.thefacebook.com> References: <20200511185218.1422406-1-jakub@cloudflare.com> <20200511185218.1422406-3-jakub@cloudflare.com> <20200513054121.qztevjyfkc2ltcvp@kafai-mbp.dhcp.thefacebook.com> <87wo5fucnu.fsf@cloudflare.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wo5fucnu.fsf@cloudflare.com> User-Agent: NeoMutt/20180716 X-ClientProxiedBy: BYAPR11CA0037.namprd11.prod.outlook.com (2603:10b6:a03:80::14) To BY5PR15MB3571.namprd15.prod.outlook.com (2603:10b6:a03:1f6::32) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp.dhcp.thefacebook.com (2620:10d:c090:400::5:64df) by BYAPR11CA0037.namprd11.prod.outlook.com (2603:10b6:a03:80::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3000.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: iYQkyGS+IqoQED4CeFHQcl469VTCmK+zi55yL6mfJ5CR8+zPmMsrBj8kOTnnsN7iZCrZkEWu4pPIKWgdnal4hJmJPpyrxX8LbEv3Fcc/AqlDMGw1/Th8p/hVPLg+1aJTY7bGcbKIkDWeD8A4axM6MqTgLCvyK8s5Fvz/rjfMtzQ7Mv+L61fcUfVnrlcid/JCeSYyBDyX6NRIsxpBI0ZWpwziuSrKqgiYBD5MbPEJrJB0S20xWx5jSTEX75Ae/sErxVfVk3IjkI5LGSfwhNPkbtr+QDpx3NYLk1j8JoFpX1jMSS/ykx9MacHulQo4y2rodApwmiEj/PTOwkAOPgCW5QgYMpQEZcddJetebXOjVMxfbGTgkuf/jwUHSYczSeYq5jHJ5BweQBBhnUucQMqlRJ2J2uYO/7BwXSyMM/qHJs/pAlREPv0rtisVh3vIDkpicqXaO09OhLXedhlzIk83JyAV+vh6LLXBTy+1ZFRIhS+hAgey43vMy61rDsQAc9EaUfK+CLWquOVe6/Wzsw6W6A== X-MS-Exchange-CrossTenant-Network-Message-Id: 1e347cef-9301-442b-2520-08d7f768e714 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 May 2020 18:10:22.5229 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ZIOa3NsIC7qyfzNiThyAtBN7U/JnsRPzthNRhLZnuDUJDE2Mk2C6HpnW+El1Q7F8 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR15MB3668 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-13_08:2020-05-13,2020-05-13 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 phishscore=0 cotscore=-2147483648 lowpriorityscore=0 spamscore=0 adultscore=0 impostorscore=0 mlxlogscore=981 priorityscore=1501 bulkscore=0 clxscore=1015 malwarescore=0 mlxscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005130154 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, May 13, 2020 at 04:34:13PM +0200, Jakub Sitnicki wrote: > 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. Thanks for the explanation. > > 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? Sure, it is hard to comment which use case is more common than another to take the default ;) I think there are use caes for both, so no strong opinion on this ;)