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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 7D15FC64E7C for ; Wed, 2 Dec 2020 23:44:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 31BD822201 for ; Wed, 2 Dec 2020 23:44:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729227AbgLBXoU (ORCPT ); Wed, 2 Dec 2020 18:44:20 -0500 Received: from www62.your-server.de ([213.133.104.62]:57536 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728021AbgLBXoU (ORCPT ); Wed, 2 Dec 2020 18:44:20 -0500 Received: from sslproxy06.your-server.de ([78.46.172.3]) by www62.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1kkbmb-0006N9-Ba; Thu, 03 Dec 2020 00:43:37 +0100 Received: from [85.7.101.30] (helo=pc-9.home) by sslproxy06.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kkbmb-000GPi-10; Thu, 03 Dec 2020 00:43:37 +0100 Subject: Re: [PATCH bpf-next V8 5/8] bpf: drop MTU check when doing TC-BPF redirect to ingress To: Jesper Dangaard Brouer , 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 References: <160650034591.2890576.1092952641487480652.stgit@firesoul> <160650040292.2890576.17040975200628427127.stgit@firesoul> From: Daniel Borkmann Message-ID: Date: Thu, 3 Dec 2020 00:43:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <160650040292.2890576.17040975200628427127.stgit@firesoul> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.4/26006/Wed Dec 2 14:14:18 2020) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 11/27/20 7:06 PM, Jesper Dangaard Brouer wrote: > The use-case for dropping the MTU check when TC-BPF does redirect to > ingress, is described by Eyal Birger in email[0]. The summary is the > ability to increase packet size (e.g. with IPv6 headers for NAT64) and > ingress redirect packet and let normal netstack fragment packet as needed. > > [0] https://lore.kernel.org/netdev/CAHsH6Gug-hsLGHQ6N0wtixdOa85LDZ3HNRHVd0opR=19Qo4W4Q@mail.gmail.com/ > > V4: > - Keep net_device "up" (IFF_UP) check. > - Adjustment to handle bpf_redirect_peer() helper > > Signed-off-by: Jesper Dangaard Brouer > --- > include/linux/netdevice.h | 31 +++++++++++++++++++++++++++++-- > net/core/dev.c | 19 ++----------------- > net/core/filter.c | 14 +++++++++++--- > 3 files changed, 42 insertions(+), 22 deletions(-) > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > index 7ce648a564f7..4a854e09e918 100644 > --- a/include/linux/netdevice.h > +++ b/include/linux/netdevice.h > @@ -3917,11 +3917,38 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb); > bool is_skb_forwardable(const struct net_device *dev, > const struct sk_buff *skb); > > +static __always_inline bool __is_skb_forwardable(const struct net_device *dev, > + const struct sk_buff *skb, > + const bool check_mtu) > +{ > + const u32 vlan_hdr_len = 4; /* VLAN_HLEN */ > + unsigned int len; > + > + if (!(dev->flags & IFF_UP)) > + return false; > + > + if (!check_mtu) > + return true; > + > + len = dev->mtu + dev->hard_header_len + vlan_hdr_len; > + if (skb->len <= len) > + return true; > + > + /* if TSO is enabled, we don't care about the length as the packet > + * could be forwarded without being segmented before > + */ > + if (skb_is_gso(skb)) > + return true; > + > + return false; > +} > + > static __always_inline int ____dev_forward_skb(struct net_device *dev, > - struct sk_buff *skb) > + struct sk_buff *skb, > + const bool check_mtu) > { > if (skb_orphan_frags(skb, GFP_ATOMIC) || > - unlikely(!is_skb_forwardable(dev, skb))) { > + unlikely(!__is_skb_forwardable(dev, skb, check_mtu))) { > atomic_long_inc(&dev->rx_dropped); > kfree_skb(skb); > return NET_RX_DROP; > diff --git a/net/core/dev.c b/net/core/dev.c > index 60d325bda0d7..6ceb6412ee97 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -2189,28 +2189,13 @@ static inline void net_timestamp_set(struct sk_buff *skb) > > bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb) > { > - unsigned int len; > - > - if (!(dev->flags & IFF_UP)) > - return false; > - > - len = dev->mtu + dev->hard_header_len + VLAN_HLEN; > - if (skb->len <= len) > - return true; > - > - /* if TSO is enabled, we don't care about the length as the packet > - * could be forwarded without being segmented before > - */ > - if (skb_is_gso(skb)) > - return true; > - > - return false; > + return __is_skb_forwardable(dev, skb, true); > } > EXPORT_SYMBOL_GPL(is_skb_forwardable); Only user of is_skb_forwardable() that is left after this patch is bridge, maybe the whole thing should be moved into the header? > int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb) > { > - int ret = ____dev_forward_skb(dev, skb); > + int ret = ____dev_forward_skb(dev, skb, true); > > if (likely(!ret)) { > skb->protocol = eth_type_trans(skb, dev); > diff --git a/net/core/filter.c b/net/core/filter.c > index d6125cfc49c3..4673afe59533 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2083,13 +2083,21 @@ static const struct bpf_func_proto bpf_csum_level_proto = { > > static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb) > { > - return dev_forward_skb(dev, skb); > + int ret = ____dev_forward_skb(dev, skb, false); > + > + if (likely(!ret)) { > + skb->protocol = eth_type_trans(skb, dev); > + skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN); > + ret = netif_rx(skb); Why netif_rx() and not netif_rx_internal() as in dev_forward_skb() originally? One extra call otherwise. > + } > + > + return ret; > } > > static inline int __bpf_rx_skb_no_mac(struct net_device *dev, > struct sk_buff *skb) > { > - int ret = ____dev_forward_skb(dev, skb); > + int ret = ____dev_forward_skb(dev, skb, false); > > if (likely(!ret)) { > skb->dev = dev; > @@ -2480,7 +2488,7 @@ int skb_do_redirect(struct sk_buff *skb) > goto out_drop; > dev = ops->ndo_get_peer_dev(dev); > if (unlikely(!dev || > - !is_skb_forwardable(dev, skb) || > + !__is_skb_forwardable(dev, skb, false) || If we only use __is_skb_forwardable() with false directly here, maybe then lets just have the !(dev->flags & IFF_UP) test here instead.. > net_eq(net, dev_net(dev)))) > goto out_drop; > skb->dev = dev; > >