From patchwork Tue Feb 2 16:26:56 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: 12062273 X-Patchwork-Delegate: bpf@iogearbox.net 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, URIBL_BLOCKED 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 BBF5DC433E9 for ; Tue, 2 Feb 2021 16:44:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B85364F76 for ; Tue, 2 Feb 2021 16:44:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236122AbhBBQoK (ORCPT ); Tue, 2 Feb 2021 11:44:10 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:30514 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236342AbhBBQcB (ORCPT ); Tue, 2 Feb 2021 11:32:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612283434; 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=GlWyJZFPLvZd2uOv7XebixcLIn4+3bgaof6lmFszE7I=; b=dRh8tM8iIIT4WKYRUl8EOSxGZrLVAHSbswBa0AiQKK3IxqJ+wbTjMmIfWpavdVKch9eilu kWKdjSkFpQb+51IFwVsV0vayh+N4/dRaEnb688OUnmnARIfnbO57oFYPe703QwXLYSj3To UK3Sp89M8PBy9epYzphFE5mkIUv4co8= 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-206-zz5-B5VeOGWGwcDMaPabIw-1; Tue, 02 Feb 2021 11:27:04 -0500 X-MC-Unique: zz5-B5VeOGWGwcDMaPabIw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 81218DF8A9; Tue, 2 Feb 2021 16:27:01 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id D9A215C224; Tue, 2 Feb 2021 16:26:57 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id DCEE730736C74; Tue, 2 Feb 2021 17:26:56 +0100 (CET) Subject: [PATCH bpf-next V15 3/7] bpf: bpf_fib_lookup return MTU value as output when looked up 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: Tue, 02 Feb 2021 17:26:56 +0100 Message-ID: <161228321684.576669.10873647164254991996.stgit@firesoul> In-Reply-To: <161228314075.576669.15427172810948915572.stgit@firesoul> References: <161228314075.576669.15427172810948915572.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The BPF-helpers for FIB lookup (bpf_xdp_fib_lookup and bpf_skb_fib_lookup) can perform MTU check and return BPF_FIB_LKUP_RET_FRAG_NEEDED. The BPF-prog don't know the MTU value that caused this rejection. If the BPF-prog wants to implement PMTU (Path MTU Discovery) (rfc1191) it need to know this MTU value for the ICMP packet. Patch change lookup and result struct bpf_fib_lookup, to contain this MTU value as output via a union with 'tot_len' as this is the value used for the MTU lookup. V5: - Fixed uninit value spotted by Dan Carpenter. - Name struct output member mtu_result Reported-by: kernel test robot Reported-by: Dan Carpenter Signed-off-by: Jesper Dangaard Brouer Acked-by: John Fastabend --- include/uapi/linux/bpf.h | 11 +++++++++-- net/core/filter.c | 22 +++++++++++++++------- tools/include/uapi/linux/bpf.h | 11 +++++++++-- 3 files changed, 33 insertions(+), 11 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index c001766adcbc..05bfc8c843dc 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2231,6 +2231,9 @@ union bpf_attr { * * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the * packet is not forwarded or needs assist from full stack * + * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU + * was exceeded and output params->mtu_result contains the MTU. + * * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags) * Description * Add an entry to, or update a sockhash *map* referencing sockets. @@ -4981,9 +4984,13 @@ struct bpf_fib_lookup { __be16 sport; __be16 dport; - /* total length of packet from network header - used for MTU check */ - __u16 tot_len; + union { /* used for MTU check */ + /* input to lookup */ + __u16 tot_len; /* L3 length from network hdr (iph->tot_len) */ + /* output: MTU value */ + __u16 mtu_result; + }; /* input: L3 device index for lookup * output: device index from FIB lookup */ diff --git a/net/core/filter.c b/net/core/filter.c index 252fbb294001..7b1b9baaabd5 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5289,12 +5289,14 @@ static const struct bpf_func_proto bpf_skb_get_xfrm_state_proto = { #if IS_ENABLED(CONFIG_INET) || IS_ENABLED(CONFIG_IPV6) static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, const struct neighbour *neigh, - const struct net_device *dev) + const struct net_device *dev, u32 mtu) { memcpy(params->dmac, neigh->ha, ETH_ALEN); memcpy(params->smac, dev->dev_addr, ETH_ALEN); params->h_vlan_TCI = 0; params->h_vlan_proto = 0; + if (mtu) + params->mtu_result = mtu; /* union with tot_len */ return 0; } @@ -5310,8 +5312,8 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct net_device *dev, struct neighbour *neigh; struct fib_result res; struct flowi4 fl4; + u32 mtu = 0; int err; - u32 mtu; /* verify forwarding is enabled on this interface */ in_dev = __in_dev_get_rcu(dev); @@ -5374,8 +5376,10 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct net_device *dev, if (check_mtu) { mtu = ip_mtu_from_fib_result(&res, params->ipv4_dst); - if (params->tot_len > mtu) + if (params->tot_len > mtu) { + params->mtu_result = mtu; /* union with tot_len */ return BPF_FIB_LKUP_RET_FRAG_NEEDED; + } } nhc = res.nhc; @@ -5409,7 +5413,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct net_device *dev, if (!neigh) return BPF_FIB_LKUP_RET_NO_NEIGH; - return bpf_fib_set_fwd_params(params, neigh, dev); + return bpf_fib_set_fwd_params(params, neigh, dev, mtu); } #endif @@ -5426,7 +5430,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct net_device *dev, struct flowi6 fl6; int strict = 0; int oif, err; - u32 mtu; + u32 mtu = 0; /* link local addresses are never forwarded */ if (rt6_need_strict(dst) || rt6_need_strict(src)) @@ -5497,8 +5501,10 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct net_device *dev, if (check_mtu) { mtu = ipv6_stub->ip6_mtu_from_fib6(&res, dst, src); - if (params->tot_len > mtu) + if (params->tot_len > mtu) { + params->mtu_result = mtu; /* union with tot_len */ return BPF_FIB_LKUP_RET_FRAG_NEEDED; + } } if (res.nh->fib_nh_lws) @@ -5518,7 +5524,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct net_device *dev, if (!neigh) return BPF_FIB_LKUP_RET_NO_NEIGH; - return bpf_fib_set_fwd_params(params, neigh, dev); + return bpf_fib_set_fwd_params(params, neigh, dev, mtu); } #endif @@ -5601,6 +5607,8 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, */ if (!is_skb_forwardable(dev, skb)) rc = BPF_FIB_LKUP_RET_FRAG_NEEDED; + + params->mtu_result = dev->mtu; /* union with tot_len */ } return rc; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index c001766adcbc..05bfc8c843dc 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2231,6 +2231,9 @@ union bpf_attr { * * > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the * packet is not forwarded or needs assist from full stack * + * If lookup fails with BPF_FIB_LKUP_RET_FRAG_NEEDED, then the MTU + * was exceeded and output params->mtu_result contains the MTU. + * * long bpf_sock_hash_update(struct bpf_sock_ops *skops, struct bpf_map *map, void *key, u64 flags) * Description * Add an entry to, or update a sockhash *map* referencing sockets. @@ -4981,9 +4984,13 @@ struct bpf_fib_lookup { __be16 sport; __be16 dport; - /* total length of packet from network header - used for MTU check */ - __u16 tot_len; + union { /* used for MTU check */ + /* input to lookup */ + __u16 tot_len; /* L3 length from network hdr (iph->tot_len) */ + /* output: MTU value */ + __u16 mtu_result; + }; /* input: L3 device index for lookup * output: device index from FIB lookup */