[PATCH v2] net: thunderbolt: Fix TCPv6 GSO checksum calculation

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Alex reported that running ssh over IPv6 does not work with
Thunderbolt/USB4 networking driver. The reason for that is that driver
should call skb_is_gso() before calling skb_is_gso_v6(), and it should
not return false after calculates the checksum successfully. This probably
was a copy paste error from the original driver where it was done properly.

Reported-by: Alex Balcanquall <alex@alexbal.com>
Fixes: e69b6c02b4c3 ("net: Add support for networking over Thunderbolt cable")
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
Previous version of the patch:

https://lore.kernel.org/netdev/20230911095039.3611113-1-mika.westerberg@linux.intel.com/

Changes from v1:

  * Drop UDP v6 GSO checksum
  * Add Fixes tag

 drivers/net/thunderbolt/main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
index 0c1e8970ee58..0a53ec293d04 100644
--- a/drivers/net/thunderbolt/main.c
+++ b/drivers/net/thunderbolt/main.c
@@ -1049,12 +1049,11 @@ static bool tbnet_xmit_csum_and_map(struct tbnet *net, struct sk_buff *skb,
 		*tucso = ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
 					    ip_hdr(skb)->daddr, 0,
 					    ip_hdr(skb)->protocol, 0);
-	} else if (skb_is_gso_v6(skb)) {
+	} else if (skb_is_gso(skb) && skb_is_gso_v6(skb)) {
 		tucso = dest + ((void *)&(tcp_hdr(skb)->check) - data);
 		*tucso = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
 					  &ipv6_hdr(skb)->daddr, 0,
 					  IPPROTO_TCP, 0);
-		return false;
 	} else if (protocol == htons(ETH_P_IPV6)) {
 		tucso = dest + skb_checksum_start_offset(skb) + skb->csum_offset;
 		*tucso = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
-- 
2.40.1