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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 3050CC5519F for ; Fri, 20 Nov 2020 08:26:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B934420888 for ; Fri, 20 Nov 2020 08:26:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Js2zSvs3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726826AbgKTI0y (ORCPT ); Fri, 20 Nov 2020 03:26:54 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:27738 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbgKTI0x (ORCPT ); Fri, 20 Nov 2020 03:26:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605860812; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=U2YimWpDUws6BcP/KA0i+1IY7B/VrO0r4M6jQRKX2a0=; b=Js2zSvs312gkLv1XKF02qhYE4RC9JB9oX5+eeqrTre8PehE1/t6yAhxO0NIehAphrUn4ow MQF+Ml1aIOM7nPF/crVTOJCuQXJBYdUEZuFNk5X5uYeggbM/gf3AgkeGJhUuScweVVsvcT 6Ya6/Ebcj2zsaEuSyy6+l9663zz5SS8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-564-2R1Y9FVCO6Owey6T2y9aKQ-1; Fri, 20 Nov 2020 03:26:50 -0500 X-MC-Unique: 2R1Y9FVCO6Owey6T2y9aKQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 17F7C1005D69; Fri, 20 Nov 2020 08:26:48 +0000 (UTC) Received: from carbon (unknown [10.36.110.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id C5AA91002393; Fri, 20 Nov 2020 08:26:39 +0000 (UTC) Date: Fri, 20 Nov 2020 09:26:38 +0100 From: Jesper Dangaard Brouer To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , maze@google.com, lmb@cloudflare.com, shaun@tigera.io, Lorenzo Bianconi , marek@cloudflare.com, John Fastabend , Jakub Kicinski , eyal.birger@gmail.com, colrack@gmail.com, brouer@redhat.com Subject: Re: [PATCH bpf-next V6 2/7] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx Message-ID: <20201120092638.14e09025@carbon> In-Reply-To: <160571337537.2801246.15228178384451037535.stgit@firesoul> References: <160571331409.2801246.11527010115263068327.stgit@firesoul> <160571337537.2801246.15228178384451037535.stgit@firesoul> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 18 Nov 2020 16:29:35 +0100 Jesper Dangaard Brouer wrote: > BPF end-user on Cilium slack-channel (Carlo Carraro) wants to use > bpf_fib_lookup for doing MTU-check, but *prior* to extending packet size, > by adjusting fib_params 'tot_len' with the packet length plus the > expected encap size. (Just like the bpf_check_mtu helper supports). He > discovered that for SKB ctx the param->tot_len was not used, instead > skb->len was used (via MTU check in is_skb_forwardable()). > > Fix this by using fib_params 'tot_len' for MTU check. If not provided > (e.g. zero) then keep existing behaviour intact. Carlo pointed out (in slack) that the logic is not correctly implemented in this patch. I will send a V7. > Fixes: 4c79579b44b1 ("bpf: Change bpf_fib_lookup to return lookup status") > Reported-by: Carlo Carraro > Signed-off-by: Jesper Dangaard Brouer > --- > net/core/filter.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/net/core/filter.c b/net/core/filter.c > index 1ee97fdeea64..ae1fe8e6069a 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -5567,10 +5567,20 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, > > if (!rc) { > struct net_device *dev; > + u32 mtu; > > dev = dev_get_by_index_rcu(net, params->ifindex); > - if (!is_skb_forwardable(dev, skb)) > + mtu = dev->mtu; > + > + /* Using tot_len for L3 MTU check if provided by user. Notice at > + * this TC cls_bpf level skb->len contains L2 size, but > + * is_skb_forwardable takes that into account. > + */ > + if (params->tot_len > mtu) { > rc = BPF_FIB_LKUP_RET_FRAG_NEEDED; > + } else if (!is_skb_forwardable(dev, skb)) { > + rc = BPF_FIB_LKUP_RET_FRAG_NEEDED; > + } > } > > return rc; -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer