From: Sean Tranchetti <stranche@codeaurora.org>
Date: Mon, 30 Apr 2018 18:01:02 -0600
Subject: udp: Complement partial checksum for GSO packet
Patch-mainline: v4.18-rc1
Git-commit: 6c035ba7e73aba4536a1112f9a0901ab40aab460
References: bsc#1109837

Using the udp_v4_check() function to calculate the pseudo header
for the newly segmented UDP packets results in assigning the complement
of the value to the UDP header checksum field.

Always undo the complement the partial checksum value in order to
match the case where GSO is not used on the UDP transmit path.

Fixes: ee80d1ebe5ba ("udp: add udp gso")
Signed-off-by: Sean Tranchetti <stranche@codeaurora.org>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/ipv4/udp_offload.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -223,6 +223,7 @@ struct sk_buff *__udp_gso_segment(struct
 			csum_replace2(&uh->check, htons(mss),
 				      htons(seg->len - hdrlen - sizeof(*uh)));
 
+		uh->check = ~uh->check;
 		seg->destructor = sock_wfree;
 		seg->sk = sk;
 		sum_truesize += seg->truesize;