From patchwork Fri Nov 27 18:06:17 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: 11937041 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 8CE78C64E7A for ; Fri, 27 Nov 2020 18:06:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 52C7822210 for ; Fri, 27 Nov 2020 18:06:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SbK+bKWo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732479AbgK0SG2 (ORCPT ); Fri, 27 Nov 2020 13:06:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23631 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732020AbgK0SG2 (ORCPT ); Fri, 27 Nov 2020 13:06:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606500386; 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=/5rl1vKmU5BfrP5W4yGSe4C/fK750/Dlz037Ebxqyw8=; b=SbK+bKWowt3tBaTdLiMMsBAJcCaCx39Y/kIZACMLsvsWGDmQvjfJP4E3d5HZT1izCoGM0c ERMGACwJda3XAuqQrWXGHiwv9NN9XChv+Nqr42biqrQl58K4cMk/Ai51G6JJy1zzdlmrMk rNMoWH0TfroA5IbXpjsuPC4xpLgyx38= 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-487-I16DNoxpP2yYrcKIjcNYsg-1; Fri, 27 Nov 2020 13:06:24 -0500 X-MC-Unique: I16DNoxpP2yYrcKIjcNYsg-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 5B399100C604; Fri, 27 Nov 2020 18:06:22 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id BDCC31001281; Fri, 27 Nov 2020 18:06:18 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id 9186132138453; Fri, 27 Nov 2020 19:06:17 +0100 (CET) Subject: [PATCH bpf-next V8 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, 27 Nov 2020 19:06:17 +0100 Message-ID: <160650034591.2890576.1092952641487480652.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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 V8: Add better selftests for BPF-helper bpf_check_mtu --- 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: tests using 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 | 204 ++++++++++++++++++++ tools/testing/selftests/bpf/progs/test_check_mtu.c | 196 +++++++++++++++++++ .../selftests/bpf/progs/test_cls_redirect.c | 7 + 9 files changed, 757 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 --