[PATCH 3.12 091/103] ip_tunnel: Set network header properly for IP_ECN_decapsulate()

[Jiri Slaby]

From: Ying Cai <ycai@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit e96f2e7c430014eff52c93cabef1ad4f42ed0db1 ]

In ip_tunnel_rcv(), set skb->network_header to inner IP header
before IP_ECN_decapsulate().

Without the fix, IP_ECN_decapsulate() takes outer IP header as
inner IP header, possibly causing error messages or packet drops.

Note that this skb_reset_network_header() call was in this spot when
the original feature for checking consistency of ECN bits through
tunnels was added in eccc1bb8d4b4 ("tunnel: drop packet if ECN present
with not-ECT"). It was only removed from this spot in 3d7b46cd20e3
("ip_tunnel: push generic protocol handling to ip_tunnel module.").

Fixes: 3d7b46cd20e3 ("ip_tunnel: push generic protocol handling to ip_tunnel module.")
Reported-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Ying Cai <ycai@xxxxxxxxxx>
Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 net/ipv4/ip_tunnel.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 3bedb26cfb53..d626d4059a42 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -433,6 +433,8 @@ int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
 		tunnel->i_seqno = ntohl(tpi->seq) + 1;
 	}
 
+	skb_reset_network_header(skb);
+
 	err = IP_ECN_decapsulate(iph, skb);
 	if (unlikely(err)) {
 		if (log_ecn_error)
-- 
1.9.3

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