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[net-next,5/6] ip6_tunnel: allow redirecting ip6gre and ipxip6 packets to eth devices

Message ID 0d7669824973cb3825c00553ca912997e4a1f2be.1624572003.git.gnault@redhat.com
State New
Headers show
Series net: reset MAC header consistently across L3 virtual devices | expand

Commit Message

Guillaume Nault June 25, 2021, 1:33 p.m. UTC 
Reset the mac_header pointer even when the tunnel transports only L3
data (in the ARPHRD_ETHER case, this is already done by eth_type_trans).
This prevents other parts of the stack from mistakenly accessing the
outer header after the packet has been decapsulated.

In practice, this allows to push an Ethernet header to ipip6, ip6ip6,
mplsip6 or ip6gre packets and redirect them to an Ethernet device:

  $ tc filter add dev ip6tnl0 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>
---
 net/ipv6/ip6_tunnel.c | 1 +
 1 file changed, 1 insertion(+)
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Patch

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 288bafded998..0b8a38687ce4 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -837,6 +837,7 @@  static int __ip6_tnl_rcv(struct ip6_tnl *tunnel, struct sk_buff *skb,
 		skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
 	} else {
 		skb->dev = tunnel->dev;
+		skb_reset_mac_header(skb);
 	}
 
 	skb_reset_network_header(skb);