/* If this is the first and only packet and device
* supports checksum offloading, let's use it.
+ * Use transhdrlen, same as IPv4, because partial
+ * sums only work when transhdrlen is set.
*/
- if (!skb && sk->sk_protocol == IPPROTO_UDP &&
+ if (transhdrlen && sk->sk_protocol == IPPROTO_UDP &&
length + fragheaderlen < mtu &&
rt->dst.dev->features & NETIF_F_V6_CSUM &&
!exthdrlen)