From: Andrea Mayer <andrea.mayer@uniroma2.it>
Date: Tue, 12 Jul 2022 19:58:37 +0200
Subject: seg6: bpf: fix skb checksum in bpf_push_seg6_encap()
Patch-mainline: v5.19-rc7
Git-commit: 4889fbd98deaf243c3baadc54e296d71c6af1eb0
References: jsc#PED-1377

Both helper functions bpf_lwt_seg6_action() and bpf_lwt_push_encap() use
the bpf_push_seg6_encap() to encapsulate the packet in an IPv6 with Segment
Routing Header (SRH) or insert an SRH between the IPv6 header and the
payload.
To achieve this result, such helper functions rely on bpf_push_seg6_encap()
which, in turn, leverages seg6_do_srh_{encap,inline}() to perform the
required operation (i.e. encap/inline).

This patch removes the initialization of the IPv6 header payload length
from bpf_push_seg6_encap(), as it is now handled properly by
seg6_do_srh_{encap,inline}() to prevent corruption of the skb checksum.

Fixes: fe94cc290f53 ("bpf: Add IPv6 Segment Routing helpers")
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 net/core/filter.c |    1 -
 1 file changed, 1 deletion(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6158,7 +6158,6 @@ static int bpf_push_seg6_encap(struct sk
 	if (err)
 		return err;
 
-	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
 	return seg6_lookup_nexthop(skb, NULL, 0);