netdev - [PATCH 3/4] xfrm: Fix eth_hdr(skb)->h_proto to reflect inner IP version

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Message-ID: <20180124094713.27913-4-steffen.klassert@secunet.com>
Date:   Wed, 24 Jan 2018 10:47:12 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH 3/4] 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>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.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 e6265e2c274e..20ca486b3cad 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 02556e356f87..dc93002ff9d1 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;
 
-- 
2.14.1