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Subject[PATCH 4.4 05/37] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()
4.4-stable review patch.  If anyone has any objections, please let me know.


From: Eli Cooper <>

[ Upstream commit 23f4ffedb7d751c7e298732ba91ca75d224bc1a6 ]

skb->cb may contain data from previous layers. In the observed scenario,
the garbage data were misinterpreted as IP6CB(skb)->frag_max_size, so
that small packets sent through the tunnel are mistakenly fragmented.

This patch unconditionally clears the control buffer in ip6tunnel_xmit(),
which affects ip6_tunnel, ip6_udp_tunnel and ip6_gre. Currently none of
these tunnels set IP6CB(skb)->flags, otherwise it needs to be done earlier.

Signed-off-by: Eli Cooper <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>
include/net/ip6_tunnel.h | 1 +
1 file changed, 1 insertion(+)

--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -86,6 +86,7 @@ static inline void ip6tunnel_xmit(struct
struct net_device_stats *stats = &dev->stats;
int pkt_len, err;

+ memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
pkt_len = skb->len - skb_inner_network_offset(skb);
err = ip6_local_out(dev_net(skb_dst(skb)->dev), sk, skb);

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