netdev - [PATCH net] xfrm: Fix eth_hdr(skb)->h_proto to reflect inner IP version

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Date:   Tue, 23 Jan 2018 00:16:21 +0200
From:   yossiku@...lanox.com
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Yossi Kuperman <yossiku@...lanox.com>
Subject: [PATCH net] xfrm: Fix eth_hdr(skb)->h_proto to reflect inner IP version

From: Yossi Kuperman <yossiku@...lanox.com>

IPSec tunnel mode supports encapsulation of IPv4 over IPv6 and vice-versa.

The outer IP header is stripped and the inner IP inherits the original
Ethernet header. Tcpdump fails to properly decode the inner packet in
case that h_proto is different than the inner IP version.

Fix h_proto to reflect the inner IP version.

Signed-off-by: Yossi Kuperman <yossiku@...lanox.com>
---
 net/ipv4/xfrm4_mode_tunnel.c | 1 +
 net/ipv6/xfrm6_mode_tunnel.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/net/ipv4/xfrm4_mode_tunnel.c b/net/ipv4/xfrm4_mode_tunnel.c
index e6265e2..20ca486 100644
--- a/net/ipv4/xfrm4_mode_tunnel.c
+++ b/net/ipv4/xfrm4_mode_tunnel.c
@@ -92,6 +92,7 @@ static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 
 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);
+	eth_hdr(skb)->h_proto = skb->protocol;
 
 	err = 0;
 
diff --git a/net/ipv6/xfrm6_mode_tunnel.c b/net/ipv6/xfrm6_mode_tunnel.c
index 02556e3..dc93002 100644
--- a/net/ipv6/xfrm6_mode_tunnel.c
+++ b/net/ipv6/xfrm6_mode_tunnel.c
@@ -92,6 +92,7 @@ static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 
 	skb_reset_network_header(skb);
 	skb_mac_header_rebuild(skb);
+	eth_hdr(skb)->h_proto = skb->protocol;
 
 	err = 0;
 
-- 
2.8.1