From 730eed2772e740c30229d03e3d578cc00a5ae304 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:08 +0200 Subject: [PATCH] sit: allow redirecting ip6ip, ipip and mplsip packets to eth devices 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 Signed-off-by: David S. Miller --- 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--- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -710,6 +710,8 @@ static int ipip6_rcv(struct sk_buff *skb) * old iph is no longer valid */ iph = (const struct iphdr *)skb_mac_header(skb); + skb_reset_mac_header(skb); + err = IP_ECN_decapsulate(iph, skb); if (unlikely(err)) { if (log_ecn_error)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); }