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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 6DA21C433ED for ; Thu, 22 Apr 2021 18:28:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2340161422 for ; Thu, 22 Apr 2021 18:28:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238607AbhDVS3Z (ORCPT ); Thu, 22 Apr 2021 14:29:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238463AbhDVS3Y (ORCPT ); Thu, 22 Apr 2021 14:29:24 -0400 Received: from mail-yb1-xb34.google.com (mail-yb1-xb34.google.com [IPv6:2607:f8b0:4864:20::b34]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F010C06174A; Thu, 22 Apr 2021 11:28:48 -0700 (PDT) Received: by mail-yb1-xb34.google.com with SMTP id p202so8979724ybg.8; Thu, 22 Apr 2021 11:28:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kccFp5PkD2OzEdY3szoFVg5JbDJwnPZzgBEkYQnfrB0=; b=qXj5xLHlA+PIZD3iIGirCpXXZIvXbVtVMWheYsd+G8D9o89UERWqfqtyEsRRISxqdc 2HZ9jZUwwF0RsCNtGQxOAJxV9mjI86yftTWNF9KfefdNbc4hsbucDKjAZxOct4boNHCW KBxdYbHYOd1iUy9iE7Gf3+uSjNLpZzEQ4YCxMtjAuYSdbK2Dg9xsTjZf7iqI7v+N1Hoi HG4LNU6TtpS4bYVXG7CLty1cF3AuWdMa/ljUXrrsUTvYWLQw8syH9o5Ii3ZPHK7z5FdZ yUI0XHlF17QPsFJG977zyu4m3V5mzdbyb5maq+InHwWY0MDQg0/+JcYxnB6Kcr4LU0pe 07kw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=kccFp5PkD2OzEdY3szoFVg5JbDJwnPZzgBEkYQnfrB0=; b=YSYDIYdj0VEIDjVhFwkyUpq2gD9EAepKUY4ul6Mle9zRVW0YnTMYcy+sgBR+wMYy7O Z8+ce9CNNmfo+oZ4azWwDKA6o4ojSnnKscJEWx3gyB/7Y4l91dVOY0oW+RZHR1tJGs2l NHuTdzsY351hR0TxMdn5oHIU0B0Kvb4Z/g8gGEtkIp+syL6tbU72gylbdjffGbfo5Xba +9JuKQ8IQrGb6q3kcIvLvWT6z4NSk7n6Gt5234znjfqzZeRrv4muFO4epIyv4HcpSJwM JKntKN8Mzuqf/OS8U23Uz7IK6Y+pixJGfhcOXE3Bv9SrCEOTE697torIhfatBrvAsb1w aPIQ== X-Gm-Message-State: AOAM5300xL53qzqz5splEBQIM2VQaa2jWs/OboqH1LECw85XxPielOn5 wNtIIUg8Mf918rhKBUr3tLGtFBE8fyVw2ZFr9Go= X-Google-Smtp-Source: ABdhPJz12k0vgb/zprEdY0F4pPYSCC55kx1TKYoUV9kTG7E5cLCUbaE9B9FsmmM3VIPwttxF7VgnzuPXumDdogUKDx0= X-Received: by 2002:a25:d70f:: with SMTP id o15mr6398881ybg.403.1619116127605; Thu, 22 Apr 2021 11:28:47 -0700 (PDT) MIME-Version: 1.0 References: <20210420193740.124285-1-memxor@gmail.com> <20210420193740.124285-3-memxor@gmail.com> <9b0aab2c-9b92-0bcb-2064-f66dd39e7552@iogearbox.net> In-Reply-To: From: Andrii Nakryiko Date: Thu, 22 Apr 2021 11:28:36 -0700 Message-ID: Subject: Re: [PATCH bpf-next v3 2/3] libbpf: add low level TC-BPF API To: Daniel Borkmann Cc: Kumar Kartikeya Dwivedi , bpf , =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Networking Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Apr 22, 2021 at 8:35 AM Daniel Borkmann wrote: > > On 4/22/21 5:43 AM, Andrii Nakryiko wrote: > > On Wed, Apr 21, 2021 at 3:59 PM Daniel Borkmann wrote: > >> On 4/20/21 9:37 PM, Kumar Kartikeya Dwivedi wrote: > >> [...] > >>> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h > >>> index bec4e6a6e31d..b4ed6a41ea70 100644 > >>> --- a/tools/lib/bpf/libbpf.h > >>> +++ b/tools/lib/bpf/libbpf.h > >>> @@ -16,6 +16,8 @@ > >>> #include > >>> #include // for size_t > >>> #include > >>> +#include > >>> +#include > >>> > >>> #include "libbpf_common.h" > >>> > >>> @@ -775,6 +777,48 @@ LIBBPF_API int bpf_linker__add_file(struct bpf_linker *linker, const char *filen > >>> LIBBPF_API int bpf_linker__finalize(struct bpf_linker *linker); > >>> LIBBPF_API void bpf_linker__free(struct bpf_linker *linker); > >>> > >>> +/* Convenience macros for the clsact attach hooks */ > >>> +#define BPF_TC_CLSACT_INGRESS TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_INGRESS) > >>> +#define BPF_TC_CLSACT_EGRESS TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS) > >> > >> I would abstract those away into an enum, plus avoid having to pull in > >> linux/pkt_sched.h and linux/tc_act/tc_bpf.h from main libbpf.h header. > >> > >> Just add a enum { BPF_TC_DIR_INGRESS, BPF_TC_DIR_EGRESS, } and then the > >> concrete tc bits (TC_H_MAKE()) can be translated internally. > >> > >>> +struct bpf_tc_opts { > >>> + size_t sz; > >> > >> Is this set anywhere? > >> > >>> + __u32 handle; > >>> + __u32 class_id; > >> > >> I'd remove class_id from here as well given in direct-action a BPF prog can > >> set it if needed. > >> > >>> + __u16 priority; > >>> + bool replace; > >>> + size_t :0; > >> > >> What's the rationale for this padding? > >> > >>> +}; > >>> + > >>> +#define bpf_tc_opts__last_field replace > >>> + > >>> +/* Acts as a handle for an attached filter */ > >>> +struct bpf_tc_attach_id { > >> > >> nit: maybe bpf_tc_ctx > > > > ok, so wait. It seems like apart from INGRESS|EGRESS enum and ifindex, > > everything else is optional and/or has some sane defaults, right? So > > this bpf_tc_attach_id or bpf_tc_ctx seems a bit artificial construct > > and it will cause problems for extending this. > > > > So if my understanding is correct, I'd get rid of it completely. As I > > said previously, opts allow returning parameters back, so if user > > didn't specify handle and priority and kernel picks values on user's > > behalf, we can return them in the same opts fields. > > > > For detach, again, ifindex and INGRESS|EGRESS is sufficient, but if > > user want to provide more detailed parameters, we should do that > > through extensible opts. That way we can keep growing this easily, > > plus simple cases will remain simple. > > > > Similarly bpf_tc_info below, there is no need to have struct > > bpf_tc_attach_id id; field, just have handle and priority right there. > > And bpf_tc_info should use OPTS framework for extensibility (though > > opts name doesn't fit it very well, but it is still nice for > > extensibility and for doing optional input/output params). > > > > Does this make sense? Am I missing something crucial here? > > I would probably keep the handle + priority in there; maybe if both are 0, > we could fix it to some default value internally, but without those it might > be a bit hard if people want to build a 'pipeline' of cls_bpf progs if they > need/want to. Oh, I'm not proposing to drop support for specifying handle and prio. I'm just saying having a fixed UAPI struct bpf_tc_attach_id as an "ID" is problematic from API stability point of view. So instead of pretending we know what "ID" will always be like, pass any extra non-default fields in OPTS struct. And if those are not specified by user (either opts is NULL or handle/prio is 0), use sane defaults, as you are proposing. > > Potentially, one could fixate the handle itself, and then allow to specify > different priorities for it such that when a BPF prog returns a TC_ACT_UNSPEC, > it will exec the next one inside that cls_bpf instance, every other TC_ACT_* > opcode will terminate the processing. Technically, only priority would really > be needed (unless you combine multiple different classifiers from tc side on > the ingress/egress hook which is not great to begin with, tbh). > > > The general rule with any new structs added to libbpf APIs is to > > either be 100% (ok, 99.99%) sure that they will never be changed, or > > do forward/backward compatible OPTS. Any other thing is pain and calls > > for symbol versioning, which we are trying really hard to avoid. > > > >>> + __u32 handle; > >>> + __u16 priority; > >>> +}; > >>> + > >>> +struct bpf_tc_info { > >>> + struct bpf_tc_attach_id id; > >>> + __u16 protocol; > >>> + __u32 chain_index; > >>> + __u32 prog_id; > >>> + __u8 tag[BPF_TAG_SIZE]; > >>> + __u32 class_id; > >>> + __u32 bpf_flags; > >>> + __u32 bpf_flags_gen; > >> > >> Given we do not yet have any setters e.g. for offload, etc, the one thing > >> I'd see useful and crucial initially is prog_id. > >> > >> The protocol, chain_index, and I would also include tag should be dropped. > >> Similarly class_id given my earlier statement, and flags I would extend once > >> this lib API would support offloading progs. > >> > >>> +}; > >>> + > >>> +/* id is out parameter that will be written to, it must not be NULL */ > >>> +LIBBPF_API int bpf_tc_attach(int fd, __u32 ifindex, __u32 parent_id, > >>> + const struct bpf_tc_opts *opts, > >>> + struct bpf_tc_attach_id *id); > >>> +LIBBPF_API int bpf_tc_detach(__u32 ifindex, __u32 parent_id, > >>> + const struct bpf_tc_attach_id *id); > >>> +LIBBPF_API int bpf_tc_get_info(__u32 ifindex, __u32 parent_id, > >>> + const struct bpf_tc_attach_id *id, > >>> + struct bpf_tc_info *info); > >> > >> As per above, for parent_id I'd replace with dir enum. > >> > >>> + > >>> #ifdef __cplusplus > >>> } /* extern "C" */ > >>> #endif >