From f0a5af78b530ab5616d6fcde79d28ad57ecaea3e Mon Sep 17 00:00:00 2001
From: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Date: Wed, 13 Sep 2017 19:30:51 -0600
Subject: udpv6: Fix the checksum computation when HW checksum does not apply

[ Upstream commit 63ecc3d9436f8012e49dc846d6cb0a85a3433517 ]

While trying an ESP transport mode encryption for UDPv6 packets of
datagram size 1436 with MTU 1500, checksum error was observed in
the secondary fragment.

This error occurs due to the UDP payload checksum being missed out
when computing the full checksum for these packets in
udp6_hwcsum_outgoing().

Fixes: d39d938c8228 ("ipv6: Introduce udpv6_send_skb()")
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2497f62..4db5f54 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -915,6 +915,7 @@ static void udp6_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
 		 */
 		offset = skb_transport_offset(skb);
 		skb->csum = skb_checksum(skb, offset, skb->len - offset, 0);
+		csum = skb->csum;
 
 		skb->ip_summed = CHECKSUM_NONE;
 
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