Init the gre_key from tuninfo->key.tun_id and init the mark
from the skb->mark, set the oif to zero in the collect metadata
mode.
Fixes: cfc7381b3002 ("ip_tunnel: add collect_md mode to IPIP tunnel") Signed-off-by: wenxu <wenxu@ucloud.cn> Signed-off-by: David S. Miller <davem@davemloft.net>