From patchwork Fri Nov 20 16:18:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 11921255 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=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, 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 F3A4CC64E69 for ; Fri, 20 Nov 2020 16:18:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D96B238E6 for ; Fri, 20 Nov 2020 16:18:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="doakTlYY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729074AbgKTQSV (ORCPT ); Fri, 20 Nov 2020 11:18:21 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:53137 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728980AbgKTQSU (ORCPT ); Fri, 20 Nov 2020 11:18:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605889099; 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; bh=8UefoEkZ47GijMZwhF+ShYGn0ymrq/7As4IgeH/Mu80=; b=doakTlYYjTfLMvgWeYJxyCUNMQ1UTBKdukwm45/j03RxpmALecnei8qDbulQDYzL1vOcyy AlvVw2G+A2IfDy0D39hj8v9atcZwF31rqTlz6uDD4B0UCajQNYuweZOJ/sd77q9WWlXOgD 1v0MFuuVrdKBRjKcOpIKGF/v9ziAn3g= 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-11-_iYWARPvOZmXdNLe0htCcg-1; Fri, 20 Nov 2020 11:18:16 -0500 X-MC-Unique: _iYWARPvOZmXdNLe0htCcg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4E3F8911ED; Fri, 20 Nov 2020 16:18:14 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2CE7760C05; Fri, 20 Nov 2020 16:18:08 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id CEFAE3213845D; Fri, 20 Nov 2020 17:18:06 +0100 (CET) Subject: [PATCH bpf-next V7 0/8] bpf: New approach for BPF MTU handling From: Jesper Dangaard Brouer To: bpf@vger.kernel.org Cc: Jesper Dangaard Brouer , 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 Date: Fri, 20 Nov 2020 17:18:06 +0100 Message-ID: <160588903254.2817268.4861837335793475314.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This patchset drops all the MTU checks in TC BPF-helpers that limits growing the packet size. This is done because these BPF-helpers doesn't take redirect into account, which can result in their MTU check being done against the wrong netdev. The new approach is to give BPF-programs knowledge about the MTU on a netdev (via ifindex) and fib route lookup level. Meaning some BPF-helpers are added and extended to make it possible to do MTU checks in the BPF-code. If BPF-prog doesn't comply with the MTU then the packet will eventually get dropped as some other layer. In some cases the existing kernel MTU checks will drop the packet, but there are also cases where BPF can bypass these checks. Specifically doing TC-redirect from ingress step (sch_handle_ingress) into egress code path (basically calling dev_queue_xmit()). It is left up to driver code to handle these kind of MTU violations. One advantage of this approach is that it ingress-to-egress BPF-prog can send information via packet data. With the MTU checks removed in the helpers, and also not done in skb_do_redirect() call, this allows for an ingress BPF-prog to communicate with an egress BPF-prog via packet data, as long as egress BPF-prog remove this prior to transmitting packet. This patchset is primarily focused on TC-BPF, but I've made sure that the MTU BPF-helpers also works for XDP BPF-programs. V2: Change BPF-helper API from lookup to check. V3: Drop enforcement of MTU in net-core, leave it to drivers. V4: Keep sanity limit + netdev "up" checks + rename BPF-helper. V5: Fix uninit variable + name struct output member mtu_result. V6: Use bpf_check_mtu() in selftest V7: Fix logic using tot_len and add another selftest --- Jesper Dangaard Brouer (8): bpf: Remove MTU check in __bpf_skb_max_len bpf: fix bpf_fib_lookup helper MTU check for SKB ctx bpf: bpf_fib_lookup return MTU value as output when looked up bpf: add BPF-helper for MTU checking bpf: drop MTU check when doing TC-BPF redirect to ingress bpf: make it possible to identify BPF redirected SKBs selftests/bpf: use bpf_check_mtu in selftest test_cls_redirect bpf/selftests: activating bpf_check_mtu BPF-helper include/linux/netdevice.h | 31 +++ include/uapi/linux/bpf.h | 78 ++++++++ net/core/dev.c | 21 -- net/core/filter.c | 184 ++++++++++++++++++-- net/sched/Kconfig | 1 tools/include/uapi/linux/bpf.h | 78 ++++++++ tools/testing/selftests/bpf/prog_tests/check_mtu.c | 37 ++++ tools/testing/selftests/bpf/progs/test_check_mtu.c | 33 ++++ .../selftests/bpf/progs/test_cls_redirect.c | 7 + 9 files changed, 427 insertions(+), 43 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/check_mtu.c create mode 100644 tools/testing/selftests/bpf/progs/test_check_mtu.c --