From patchwork Mon Feb 1 10:52:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 374526 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=-16.1 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 AE33EC433DB for ; Mon, 1 Feb 2021 10:55:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B2E964E56 for ; Mon, 1 Feb 2021 10:55:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233214AbhBAKyw (ORCPT ); Mon, 1 Feb 2021 05:54:52 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44866 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233140AbhBAKxy (ORCPT ); Mon, 1 Feb 2021 05:53:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612176747; 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=vpMAGKN1ZW+XTmIlso+xtUb7GLhtgn5xVtFzaXOfeeY=; b=LkJ+T6KkBKbWSEX/CGMow9pcX/Q0QP2J00BVluwm/AfmNoSqUHLPcYKotAZSXKcmedwBcC JmrT37iWtj4ScNJ1L+/QojfswcvCJSxNzg7pIP2J2EO3BbvcIxpIi+gXEACTl846CJdvQS ux/RGtQ/I9+csSgWlsh+O1zA0z8GehA= 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-455-h_bAwWGXNieuSSKyklpFng-1; Mon, 01 Feb 2021 05:52:23 -0500 X-MC-Unique: h_bAwWGXNieuSSKyklpFng-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 78341107ACE6; Mon, 1 Feb 2021 10:52:21 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7E70160C64; Mon, 1 Feb 2021 10:52:17 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id 8492F30736C73; Mon, 1 Feb 2021 11:52:16 +0100 (CET) Subject: [PATCH bpf-next V14 2/7] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx 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: Mon, 01 Feb 2021 11:52:16 +0100 Message-ID: <161217673648.494501.14458670792610885379.stgit@firesoul> In-Reply-To: <161217668357.494501.557971074995969677.stgit@firesoul> References: <161217668357.494501.557971074995969677.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: netdev@vger.kernel.org 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() that checks against netdev MTU). Fix this by using fib_params 'tot_len' for MTU check. If not provided (e.g. zero) then keep existing TC behaviour intact. Notice that 'tot_len' for MTU check is done like XDP code-path, which checks against FIB-dst MTU. V13: - Only do ifindex lookup one time, calling dev_get_by_index_rcu(). V10: - Use same method as XDP for 'tot_len' MTU check Fixes: 4c79579b44b1 ("bpf: Change bpf_fib_lookup to return lookup status") Reported-by: Carlo Carraro Signed-off-by: Jesper Dangaard Brouer Acked-by: John Fastabend --- net/core/filter.c | 50 ++++++++++++++++++++++++++++---------------------- 1 file changed, 28 insertions(+), 22 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 5beadd659091..252fbb294001 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5301,22 +5301,18 @@ static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, #endif #if IS_ENABLED(CONFIG_INET) -static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, +static int bpf_ipv4_fib_lookup(struct net *net, struct net_device *dev, + struct bpf_fib_lookup *params, u32 flags, bool check_mtu) { struct fib_nh_common *nhc; struct in_device *in_dev; struct neighbour *neigh; - struct net_device *dev; struct fib_result res; struct flowi4 fl4; int err; u32 mtu; - dev = dev_get_by_index_rcu(net, params->ifindex); - if (unlikely(!dev)) - return -ENODEV; - /* verify forwarding is enabled on this interface */ in_dev = __in_dev_get_rcu(dev); if (unlikely(!in_dev || !IN_DEV_FORWARD(in_dev))) @@ -5418,14 +5414,14 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, #endif #if IS_ENABLED(CONFIG_IPV6) -static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, +static int bpf_ipv6_fib_lookup(struct net *net, struct net_device *dev, + struct bpf_fib_lookup *params, u32 flags, bool check_mtu) { struct in6_addr *src = (struct in6_addr *) params->ipv6_src; struct in6_addr *dst = (struct in6_addr *) params->ipv6_dst; struct fib6_result res = {}; struct neighbour *neigh; - struct net_device *dev; struct inet6_dev *idev; struct flowi6 fl6; int strict = 0; @@ -5436,10 +5432,6 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (rt6_need_strict(dst) || rt6_need_strict(src)) return BPF_FIB_LKUP_RET_NOT_FWDED; - dev = dev_get_by_index_rcu(net, params->ifindex); - if (unlikely(!dev)) - return -ENODEV; - idev = __in6_dev_get_safely(dev); if (unlikely(!idev || !idev->cnf.forwarding)) return BPF_FIB_LKUP_RET_FWD_DISABLED; @@ -5533,22 +5525,27 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx, struct bpf_fib_lookup *, params, int, plen, u32, flags) { + struct net *net = dev_net(ctx->rxq->dev); + struct net_device *dev; + if (plen < sizeof(*params)) return -EINVAL; if (flags & ~(BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT)) return -EINVAL; + dev = dev_get_by_index_rcu(net, params->ifindex); + if (unlikely(!dev)) + return -ENODEV; + switch (params->family) { #if IS_ENABLED(CONFIG_INET) case AF_INET: - return bpf_ipv4_fib_lookup(dev_net(ctx->rxq->dev), params, - flags, true); + return bpf_ipv4_fib_lookup(net, dev, params, flags, true); #endif #if IS_ENABLED(CONFIG_IPV6) case AF_INET6: - return bpf_ipv6_fib_lookup(dev_net(ctx->rxq->dev), params, - flags, true); + return bpf_ipv6_fib_lookup(net, dev, params, flags, true); #endif } return -EAFNOSUPPORT; @@ -5568,7 +5565,9 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, struct bpf_fib_lookup *, params, int, plen, u32, flags) { struct net *net = dev_net(skb->dev); + struct net_device *dev; int rc = -EAFNOSUPPORT; + bool check_mtu = false; if (plen < sizeof(*params)) return -EINVAL; @@ -5576,23 +5575,30 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, if (flags & ~(BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT)) return -EINVAL; + dev = dev_get_by_index_rcu(net, params->ifindex); + if (unlikely(!dev)) + return -ENODEV; + + if (params->tot_len) + check_mtu = true; + switch (params->family) { #if IS_ENABLED(CONFIG_INET) case AF_INET: - rc = bpf_ipv4_fib_lookup(net, params, flags, false); + rc = bpf_ipv4_fib_lookup(net, dev, params, flags, check_mtu); break; #endif #if IS_ENABLED(CONFIG_IPV6) case AF_INET6: - rc = bpf_ipv6_fib_lookup(net, params, flags, false); + rc = bpf_ipv6_fib_lookup(net, dev, params, flags, check_mtu); break; #endif } - if (!rc) { - struct net_device *dev; - - dev = dev_get_by_index_rcu(net, params->ifindex); + if (rc == BPF_FIB_LKUP_RET_SUCCESS && !check_mtu) { + /* When tot_len isn't provided by user, + * check skb against net_device MTU + */ if (!is_skb_forwardable(dev, skb)) rc = BPF_FIB_LKUP_RET_FRAG_NEEDED; }