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From:   Andrea Mayer <andrea.mayer@uniroma2.it>
To:     "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Lebrun <dav.lebrun@gmail.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Andrea Mayer <andrea.mayer@uniroma2.it>
Subject: [net, 2/2] seg6: fix skb transport_header after decap_and_validate()
Date:   Sat, 16 Nov 2019 16:05:53 +0100
Message-Id: <20191116150553.17497-3-andrea.mayer@uniroma2.it>
In-Reply-To: <20191116150553.17497-1-andrea.mayer@uniroma2.it>
References: <20191116150553.17497-1-andrea.mayer@uniroma2.it>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

in the receive path (more precisely in ip6_rcv_core()) the
skb->transport_header is set to skb->network_header + sizeof(*hdr). As a
consequence, after routing operations, destination input expects to find
skb->transport_header correctly set to the next protocol (or extension
header) that follows the network protocol. However, decap behaviors (DX*,
DT*) remove the outer IPv6 and SRH extension and do not set again the
skb->transport_header pointer correctly. For this reason, the patch sets
the skb->transport_header to the skb->network_header + sizeof(hdr) in each
DX* and DT* behavior.

Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
---
 net/ipv6/seg6_local.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 5e3d7004d431..e70567446f28 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -341,6 +341,8 @@ static int input_action_end_dx6(struct sk_buff *skb,
 	if (!ipv6_addr_any(&slwt->nh6))
 		nhaddr = &slwt->nh6;
 
+	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
+
 	seg6_lookup_nexthop(skb, nhaddr, 0);
 
 	return dst_input(skb);
@@ -370,6 +372,8 @@ static int input_action_end_dx4(struct sk_buff *skb,
 
 	skb_dst_drop(skb);
 
+	skb_set_transport_header(skb, sizeof(struct iphdr));
+
 	err = ip_route_input(skb, nhaddr, iph->saddr, 0, skb->dev);
 	if (err)
 		goto drop;
@@ -390,6 +394,8 @@ static int input_action_end_dt6(struct sk_buff *skb,
 	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 		goto drop;
 
+	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
+
 	seg6_lookup_nexthop(skb, NULL, slwt->table);
 
 	return dst_input(skb);
-- 
2.20.1