From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E26DC4361B for ; Wed, 9 Dec 2020 08:29:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 239AF23B87 for ; Wed, 9 Dec 2020 08:29:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726560AbgLII3s (ORCPT ); Wed, 9 Dec 2020 03:29:48 -0500 Received: from www62.your-server.de ([213.133.104.62]:53596 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725765AbgLII3s (ORCPT ); Wed, 9 Dec 2020 03:29:48 -0500 Received: from sslproxy02.your-server.de ([78.47.166.47]) by www62.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1kmuqQ-000GRk-8o; Wed, 09 Dec 2020 09:29:06 +0100 Received: from [85.7.101.30] (helo=pc-9.home) by sslproxy02.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kmuqQ-000MlV-2N; Wed, 09 Dec 2020 09:29:06 +0100 Subject: Re: [PATCH bpf-next v2 1/3] bpf: Expose bpf_get_socket_cookie to tracing programs To: Florent Revest , bpf@vger.kernel.org Cc: ast@kernel.org, andrii@kernel.org, kpsingh@chromium.org, revest@google.com, linux-kernel@vger.kernel.org References: <20201203213330.1657666-1-revest@google.com> <7c70a64f-1aba-0e11-983d-9338f25a367e@iogearbox.net> <61135b81892e029d293b1baa3345ba78f1e848c7.camel@chromium.org> From: Daniel Borkmann Message-ID: Date: Wed, 9 Dec 2020 09:29:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <61135b81892e029d293b1baa3345ba78f1e848c7.camel@chromium.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.4/26012/Tue Dec 8 15:38:50 2020) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/8/20 8:30 PM, Florent Revest wrote: > On Fri, 2020-12-04 at 20:03 +0100, Daniel Borkmann wrote: >> On 12/4/20 7:56 PM, Daniel Borkmann wrote: >>> On 12/3/20 10:33 PM, Florent Revest wrote: >>>> This creates a new helper proto because the existing >>>> bpf_get_socket_cookie_sock_proto has a ARG_PTR_TO_CTX argument >>>> and only >>>> works for BPF programs where the context is a sock. >>>> >>>> This helper could also be useful to other BPF program types such >>>> as LSM. >>>> >>>> Signed-off-by: Florent Revest >>>> --- >>>> include/uapi/linux/bpf.h | 7 +++++++ >>>> kernel/trace/bpf_trace.c | 4 ++++ >>>> net/core/filter.c | 7 +++++++ >>>> tools/include/uapi/linux/bpf.h | 7 +++++++ >>>> 4 files changed, 25 insertions(+) >>>> >>>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h >>>> index c3458ec1f30a..3e0e33c43998 100644 >>>> --- a/include/uapi/linux/bpf.h >>>> +++ b/include/uapi/linux/bpf.h >>>> @@ -1662,6 +1662,13 @@ union bpf_attr { >>>> * Return >>>> * A 8-byte long non-decreasing number. >>>> * >>>> + * u64 bpf_get_socket_cookie(void *sk) >>>> + * Description >>>> + * Equivalent to **bpf_get_socket_cookie**\ () helper >>>> that accepts >>>> + * *sk*, but gets socket from a BTF **struct sock**. >>>> + * Return >>>> + * A 8-byte long non-decreasing number. >>> >>> I would not mention this here since it's not fully correct and we >>> should avoid users taking non-decreasing granted in their progs. >>> The only assumption you can make is that it can be considered a >>> unique number. See also [0] with reverse counter.. >>> >>> [0] >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=92acdc58ab11af66fcaef485433fde61b5e32fac > > Ah this is a good point, thank you! I will send a v3 with an extra > patch that s/non-decreasing/unique/ in the other descriptions. I had > not given it any extra thought, I just stupidly copied/pasted existing > descriptions. :) > >> One more thought, in case you plan to use this from sleepable >> context, you would need to use sock_gen_cookie() variant in the BPF >> helper instead. > > Out of curiosity, why don't we just always call sock_gen_cookie? Is it > to avoid the performance impact of increasing the preempt counter and > introducing a memory barriers ? Yes, all the other contexts where the existing helpers are used already have preemption disabled, so the extra preempt_{disable,enable}() is unnecessary overhead given we want the cookie generation be efficient. Thanks, Daniel