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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_PASS,USER_AGENT_NEOMUTT 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 E71EAC4360F for ; Wed, 27 Mar 2019 01:41:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9FD12082F for ; Wed, 27 Mar 2019 01:41:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="iFkCV0bF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732447AbfC0Bl1 (ORCPT ); Tue, 26 Mar 2019 21:41:27 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:32938 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727500AbfC0Bl1 (ORCPT ); Tue, 26 Mar 2019 21:41:27 -0400 Received: by mail-pf1-f194.google.com with SMTP id i19so288543pfd.0; Tue, 26 Mar 2019 18:41:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=cSLpheXXbH8xheIDLfPAeNGZDwyrQAw9ZNkh9ZwjcuE=; b=iFkCV0bFXZkrehbPR2cvj+vtHL/AUj4hwoDwRUBCtu5VhCLuDMZYuA4yKpRgEL0yyh N8rkv8c5j5U/Knscj6dlN8ELQwmwS44kchKJmHzUMbYL/LmEBfZhO/wwIXC/cLT1YINe N842jOss8/q84y0MEMJ6J4tNWc4CAqu5Jvw9beiQ1fUsdnLyDzdb3t3gTtNTnIDU4ME0 qwKWhK0w1YP835/TM7MhXCbC3hwKH+ZINcm6T3xLhFB69ZpVHFx+owU7gK6DKfD8YMmR SPNKlVtJ/kiskdLf6Vc7YGI0ucwHBQiXMj29lByxTOAOgfWIJ7KcsTNWDSR7RlBPjLYz YZUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=cSLpheXXbH8xheIDLfPAeNGZDwyrQAw9ZNkh9ZwjcuE=; b=Z9kCVWS85Wniuh5iSoBCCSjz1N09BaJ5j+kHoVx+ICR2lPWOpyJWBTXKpz1BHUIne+ ioDRPx2+9Ac0JM+Z8fgPWy9pZrO3qTFqCPc0XnMTtx2dRkGwUxROTVpkIk2lCZq1F59N rdP9ONIyoFVWqR71V3i9AJkTVS//H3h62mp2NlQ8RK1BgnllqVzlcJSVeKCUNJBW+l+M c6Nn6M0bJZgpUFcKkjcDncWW9aHeCEZXrgE7Bm+w3cAQMUrgjpOOVET2W2DmDBreQAxy l3eucjzY++KfFEFmNfx9dklB3QJo63dAFnVLV4eSe6yjjNe94gQswSNUciPBBiBmnHjd d5qg== X-Gm-Message-State: APjAAAUNH+32zxZNVxyfFKz10/SrComQkA2qjYhe0h66z2XUAgrdMx4P X2D4LuGnp5QS8cVmJ3tQi8o= X-Google-Smtp-Source: APXvYqzIPLPBx6QmDbzMcpWNbBTgKNfTK3lx6oXn1b50pdWu+u4nhRHbEMzmnBQ4G4LPpzL4XrDIDw== X-Received: by 2002:a62:3849:: with SMTP id f70mr29536775pfa.46.1553650885846; Tue, 26 Mar 2019 18:41:25 -0700 (PDT) Received: from ast-mbp ([2620:10d:c090:200::1:f1fc]) by smtp.gmail.com with ESMTPSA id e1sm25614441pfn.73.2019.03.26.18.41.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Mar 2019 18:41:25 -0700 (PDT) Date: Tue, 26 Mar 2019 18:41:23 -0700 From: Alexei Starovoitov To: Stanislav Fomichev Cc: Willem de Bruijn , Stanislav Fomichev , Network Development , bpf , David Miller , Alexei Starovoitov , Daniel Borkmann , Simon Horman , Willem de Bruijn , Petar Penkov Subject: Re: [RFC bpf-next v3 6/8] flow_dissector: handle no-skb use case Message-ID: <20190327014121.p45cblrgqgdyiu6z@ast-mbp> References: <20190323014101.mxeey4tw3gt7o4yi@ast-mbp.dhcp.thefacebook.com> <20190323160531.GZ7431@mini-arch.hsd1.ca.comcast.net> <20190326003517.fuqb4mqsbqq4mtk5@ast-mbp> <20190326164529.GB7431@mini-arch.hsd1.ca.comcast.net> <20190326174802.jnhvtdephykfj6ku@ast-mbp> <20190326181719.GC7431@mini-arch.hsd1.ca.comcast.net> <20190326183011.jly4j3s332yohrj5@ast-mbp> <20190326185456.GD7431@mini-arch.hsd1.ca.comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190326185456.GD7431@mini-arch.hsd1.ca.comcast.net> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Mar 26, 2019 at 11:54:56AM -0700, Stanislav Fomichev wrote: > On 03/26, Alexei Starovoitov wrote: > > On Tue, Mar 26, 2019 at 11:17:19AM -0700, Stanislav Fomichev wrote: > > > On 03/26, Alexei Starovoitov wrote: > > > > On Tue, Mar 26, 2019 at 10:52 AM Willem de Bruijn > > > > wrote: > > > > > The BPF flow dissector should work the same. It is fine to pass the > > > > > data including ethernet header, but parsing can start at nhoff with > > > > > proto explicitly passed. > > > > > > > > > > We should not assume Ethernet link layer. > > > > > > > > then skb-less dissector has to be different program type > > > > because semantics are different. > > > The semantics are the same as for c-based __skb_flow_dissect. > > > We just need to pass nhoff and proto that has been passed to > > > __skb_flow_dissect to the bpf program. In case of with-skb, > > > take this initial data from skb, like __skb_flow_dissect does (and don't > > > ask BPF program to do it essentially): > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/tree/net/core/flow_dissector.c#n763 > > > > > > I was thinking of passing proto as flow_keys->n_proto and we already > > > pass flow_keys->nhoff, so no need to do anything for it. With that, > > > BPF program doesn't need to look into skb and can parse optional vlan > > > and L3+ headers. The same way __skb_flow_dissect does that. > > > > makes sense. then I'd also prefer for proto to be in flow_keys to > > high light this difference. > Maybe rename existing flow_keys->n_proto to flow_keys->proto? > That would match __skb_flow_dissect and remove ambiguity with both proto > and n_proto in flow_keys. disabling useless fields in ctx is one thing, since probability of breaking users is low, but renaming n_proto is imo too much. > > may be add vlan_proto/present/tci there as well? > > At least on the kernel side ctx rewriter will be the same for w/ & w/o skb cases. > Why do you think we need them? My understanding was that when > skb_vlan_tag_present(skb) (or skb->vlan_present) returns true, that means > that vlan info has been already parsed out of the packet and stored in > the vlan_tci/vlan_proto (where vlan_proto is 8021Q/8021AD); skb data > points to proper L3 header. > > If that's correct, BPF flow dissector should not care about that. For > example, look at how C-based flow dissector does that: > > https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/tree/net/core/flow_dissector.c#n944 > > If skb_vlan_tag_present(skb) returns true, we set proto to skb->protocol > and move on. > > But, we would need vlan_proto/present/tci in the flow_keys in the future. > We don't currently return parsed vlan data from the BPF flow dissector. > But it feels like it's getting into bpf-next territory :-) Whether ctx->data points to L2 or L3 is uapi regardless whether progs/bpf_flow.c is relying on that or not. So far I think you're saying that in all three cases: no-skb, skb befor rfs, skb after rfs ctx->data points to L2, right? This has to be preserved. Only now after reading bpf_flow.c for Nth time I realized what semantics you gave to skb->vlan* and skb->protocol fields. All of them have to be kept as-is. For no-skb cases all of them should be available with the same logic and it has to documented, since it's different from other bpf progs that access these fields.