vxlan: using pskb_may_pull as early as possible
vxlan: using pskb_may_pull as early as possible

pskb_may_pull should be used to check if skb->data has enough space,
skb->len can not ensure that.

Cc: Cong Wang <0f114804888b88d50037b04b42e57b858d851b87@gmail.com>
Signed-off-by: Li RongQing <81c2f95e9d1350da984a3ef03e964ca9a6cbc5c2@gmail.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs