netdev - [PATCH v2] ip6_tunnel: Clear IP6CB in ip6_tnl

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Message-Id: <20161028015241.23258-1-elicooper@gmx.com>
Date:   Fri, 28 Oct 2016 09:52:41 +0800
From:   Eli Cooper <elicooper@....com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>
Subject: [PATCH v2] ip6_tunnel: Clear IP6CB in ip6_tnl_xmit() after encapsulation

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 clears the control buffer for the next layer, after an IPv6
header is installed.

Signed-off-by: Eli Cooper <elicooper@....com>
---
v2: clears the whole IP6CB altogether and does it after encapsulation

 net/ipv6/ip6_tunnel.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 202d16a..1487e17 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1174,6 +1174,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,

 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
+	memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
 	ipv6h = ipv6_hdr(skb);
 	ip6_flow_hdr(ipv6h, INET_ECN_encapsulate(0, dsfield),
 		     ip6_make_flowlabel(net, skb, fl6->flowlabel, true, fl6));
-- 
2.10.1