[PATCH net-next] udp: Complement partial checksum for GSO packet

[Sean Tranchetti <stranche@codeaurora.org>]

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>
---
 net/ipv4/udp_offload.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index f78fb36..0062570 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -223,6 +223,7 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 			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;
-- 
1.9.1