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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 2B984C4363A for ; Wed, 21 Oct 2020 18:51:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BFEC822456 for ; Wed, 21 Oct 2020 18:51:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437113AbgJUSvH (ORCPT ); Wed, 21 Oct 2020 14:51:07 -0400 Received: from smtp.uniroma2.it ([160.80.6.22]:47193 "EHLO smtp.uniroma2.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2437233AbgJUSvH (ORCPT ); Wed, 21 Oct 2020 14:51:07 -0400 Received: from localhost.localdomain ([160.80.103.126]) by smtp-2015.uniroma2.it (8.14.4/8.14.4/Debian-8) with ESMTP id 09LIga9g005673 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Wed, 21 Oct 2020 20:42:38 +0200 From: Andrea Mayer To: "David S. Miller" , David Ahern , Alexey Kuznetsov , Hideaki YOSHIFUJI , Jakub Kicinski , Shuah Khan , Shrijeet Mukherjee , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Stefano Salsano , Paolo Lungaroni , Ahmed Abdelsalam , Andrea Mayer Subject: [RFC,net-next, 1/4] vrf: push mac header for tunneled packets when sniffer is attached Date: Wed, 21 Oct 2020 20:41:13 +0200 Message-Id: <20201021184116.2722-2-andrea.mayer@uniroma2.it> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201021184116.2722-1-andrea.mayer@uniroma2.it> References: <20201021184116.2722-1-andrea.mayer@uniroma2.it> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Virus-Scanned: clamav-milter 0.100.0 at smtp-2015 X-Virus-Status: Clean Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Before this patch, a sniffer attached to a VRF used as the receiving interface of L3 tunneled packets detects them as malformed packets and it complains about that (i.e.: tcpdump shows bogus packets). The reason is that a tunneled L3 packet does not carry any L2 information and when the VRF is set as the receiving interface of a decapsulated L3 packet, no mac header is currently set or valid. Therefore the purpose of this patch consists of adding a MAC header to any packet which is directly received on the VRF interface ONLY IF: i) a sniffer is attached on the VRF and ii) the mac header is not set. In this case, the mac address of the VRF is copied in both the destination and the source address of the ethernet header. The protocol type is set either to IPv4 or IPv6, depending on which L3 packet is received. Signed-off-by: Andrea Mayer --- drivers/net/vrf.c | 78 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 72 insertions(+), 6 deletions(-) diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c index 60c1aadece89..abb09c6036a6 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -1263,6 +1263,61 @@ static void vrf_ip6_input_dst(struct sk_buff *skb, struct net_device *vrf_dev, skb_dst_set(skb, &rt6->dst); } +static int vrf_prepare_mac_header(struct sk_buff *skb, + struct net_device *vrf_dev, u16 proto) +{ + struct ethhdr *eth; + int err; + + /* in general, we do not know if there is enough space in the head of + * the packet for hosting the mac header. + */ + err = skb_cow_head(skb, LL_RESERVED_SPACE(vrf_dev)); + if (unlikely(err)) + /* no space in the skb head */ + return -ENOBUFS; + + __skb_push(skb, ETH_HLEN); + eth = (struct ethhdr *)skb->data; + + skb_reset_mac_header(skb); + + /* we set the ethernet destination and the source addresses to the + * address of the VRF device. + */ + ether_addr_copy(eth->h_dest, vrf_dev->dev_addr); + ether_addr_copy(eth->h_source, vrf_dev->dev_addr); + eth->h_proto = htons(proto); + + /* the destination address of the Ethernet frame corresponds to the + * address set on the VRF interface; therefore, the packet is intended + * to be processed locally. + */ + skb->protocol = eth->h_proto; + skb->pkt_type = PACKET_HOST; + + skb_postpush_rcsum(skb, skb->data, ETH_HLEN); + + skb_pull_inline(skb, ETH_HLEN); + + return 0; +} + +/* prepare and add the mac header to the packet if it was not previously set. + * In this way, packet sniffers such as tcpdump can parse the packet correctly. + * If the mac header was previously set, the original mac header is left + * untouched and the function returns immediately. + */ +static int vrf_add_mac_header_if_unset(struct sk_buff *skb, + struct net_device *vrf_dev, + u16 proto) +{ + if (skb_mac_header_was_set(skb)) + return 0; + + return vrf_prepare_mac_header(skb, vrf_dev, proto); +} + static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev, struct sk_buff *skb) { @@ -1289,9 +1344,15 @@ static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev, skb->skb_iif = vrf_dev->ifindex; if (!list_empty(&vrf_dev->ptype_all)) { - skb_push(skb, skb->mac_len); - dev_queue_xmit_nit(skb, vrf_dev); - skb_pull(skb, skb->mac_len); + int err; + + err = vrf_add_mac_header_if_unset(skb, vrf_dev, + ETH_P_IPV6); + if (likely(!err)) { + skb_push(skb, skb->mac_len); + dev_queue_xmit_nit(skb, vrf_dev); + skb_pull(skb, skb->mac_len); + } } IP6CB(skb)->flags |= IP6SKB_L3SLAVE; @@ -1334,9 +1395,14 @@ static struct sk_buff *vrf_ip_rcv(struct net_device *vrf_dev, vrf_rx_stats(vrf_dev, skb->len); if (!list_empty(&vrf_dev->ptype_all)) { - skb_push(skb, skb->mac_len); - dev_queue_xmit_nit(skb, vrf_dev); - skb_pull(skb, skb->mac_len); + int err; + + err = vrf_add_mac_header_if_unset(skb, vrf_dev, ETH_P_IP); + if (likely(!err)) { + skb_push(skb, skb->mac_len); + dev_queue_xmit_nit(skb, vrf_dev); + skb_pull(skb, skb->mac_len); + } } skb = vrf_rcv_nfhook(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, vrf_dev); -- 2.20.1