From 192db9b925b664c39a04baa9f865f8ca64743f86 Mon Sep 17 00:00:00 2001
From: Eli Cooper <elicooper@gmx.com>
Date: Tue, 1 Nov 2016 23:45:12 +0800
Subject: [PATCH] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit()

commit 23f4ffedb7d751c7e298732ba91ca75d224bc1a6 upstream.

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 <elicooper@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: apply to ip6_tnl_xmit2()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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