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.
Cc: sta...@vger.kernel.org
Signed-off-by: Eli Cooper <elicoo...@gmx.com>
---
v3: moves to ip6tunnel_xmit() and clears IP6CB unconditionally
v2: clears the whole IP6CB altogether and does it after encapsulation
include/net/ip6_tunnel.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/net/ip6_tunnel.h b/include/net/ip6_tunnel.h
index 20ed969..1b1cf33 100644
--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -146,6 +146,7 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct
sk_buff *skb,
{
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);
if (unlikely(net_xmit_eval(err)))
--
2.10.1
