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[2a01:cb05:8918:ce00:dd1a:5a4f:9908:f2d5]) by smtp.gmail.com with ESMTPSA id r10sm5996504wrq.17.2021.06.25.06.33.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Jun 2021 06:33:10 -0700 (PDT) Date: Fri, 25 Jun 2021 15:33:08 +0200 From: Guillaume Nault To: David Miller , Jakub Kicinski Cc: netdev@vger.kernel.org, Hideaki YOSHIFUJI , David Ahern , Simon Horman Subject: [PATCH net-next 3/6] sit: allow redirecting ip6ip, ipip and mplsip packets to eth devices Message-ID: <741ee403015d9241d8005978fc71309930d921ce.1624572003.git.gnault@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Even though sit transports L3 data (IPv6, IPv4 or MPLS) packets, it needs to reset the mac_header pointer, so that other parts of the stack don't mistakenly access the outer header after the packet has been decapsulated. There are two rx handlers to modify: ipip6_rcv() for the ip6ip mode and sit_tunnel_rcv() which is used to re-implement the ipip and mplsip modes of ipip.ko. This allows to push an Ethernet header to sit packets and redirect them to an Ethernet device: $ tc filter add dev sit0 ingress matchall \ action vlan push_eth dst_mac 00:00:5e:00:53:01 \ src_mac 00:00:5e:00:53:00 \ action mirred egress redirect dev eth0 Without this patch, push_eth refuses to add an ethernet header because the skb appears to already have a MAC header. Signed-off-by: Guillaume Nault --- net/ipv6/sit.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index e0a39b0bb4c1..df5bea818410 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -710,6 +710,8 @@ static int ipip6_rcv(struct sk_buff *skb) * old iph is no longer valid */ iph = (const struct iphdr *)skb_mac_header(skb); + skb_reset_mac_header(skb); + err = IP_ECN_decapsulate(iph, skb); if (unlikely(err)) { if (log_ecn_error) @@ -780,6 +782,8 @@ static int sit_tunnel_rcv(struct sk_buff *skb, u8 ipproto) tpi = &ipip_tpi; if (iptunnel_pull_header(skb, 0, tpi->proto, false)) goto drop; + skb_reset_mac_header(skb); + return ip_tunnel_rcv(tunnel, skb, tpi, NULL, log_ecn_error); }