linux-kernel - [net 2/3] seg6: fix skb checksum in SRv6 End.B6 and End.B6.Encaps behaviors

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Date:   Tue, 12 Jul 2022 19:58:36 +0200
From:   Andrea Mayer <andrea.mayer@...roma2.it>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        David Lebrun <david.lebrun@...ouvain.be>,
        Mathieu Xhonneux <m.xhonneux@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Stefano Salsano <stefano.salsano@...roma2.it>,
        Paolo Lungaroni <paolo.lungaroni@...roma2.it>,
        Ahmed Abdelsalam <ahabdels.dev@...il.com>,
        Anton Makarov <anton.makarov11235@...il.com>,
        Andrea Mayer <andrea.mayer@...roma2.it>
Subject: [net 2/3] seg6: fix skb checksum in SRv6 End.B6 and End.B6.Encaps behaviors

The SRv6 End.B6 and End.B6.Encaps behaviors rely on functions
seg6_do_srh_{encap,inline}() to, respectively: i) encapsulate the
packet within an outer IPv6 header with the specified Segment Routing
Header (SRH); ii) insert the specified SRH directly after the IPv6
header of the packet.

This patch removes the initialization of the IPv6 header payload length
from the input_action_end_b6{_encap}() functions, as it is now handled
properly by seg6_do_srh_{encap,inline}() to avoid corruption of the skb
checksum.

Fixes: 140f04c33bbc ("ipv6: sr: implement several seg6local actions")
Signed-off-by: Andrea Mayer <andrea.mayer@...roma2.it>
---
 net/ipv6/seg6_local.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 98a34287439c..2cd4a8d3b30a 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -826,7 +826,6 @@ static int input_action_end_b6(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 	if (err)
 		goto drop;
 
-	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
 	seg6_lookup_nexthop(skb, NULL, 0);
@@ -858,7 +857,6 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
 	if (err)
 		goto drop;
 
-	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
 	seg6_lookup_nexthop(skb, NULL, 0);
-- 
2.20.1