ipip: allow redirecting ipip and mplsip packets to eth devices

Even though ipip transports 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.

This allows to push an Ethernet header to ipip or mplsip packets and
redirect them to an Ethernet device:

  $ tc filter add dev ipip0 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 <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index d5bfa087c23ad71ff7ea54c849034a3953100377..266c65577ba68b1fbb4045ae80fe5409c657c125 100644 (file)
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -242,6 +242,8 @@ static int ipip_tunnel_rcv(struct sk_buff *skb, u8 ipproto)
                        if (!tun_dst)
                                return 0;
                }
+               skb_reset_mac_header(skb);
+
                return ip_tunnel_rcv(tunnel, skb, tpi, tun_dst, log_ecn_error);
        }