xfrm: Release dst if this dst is improper for vti tunnel

After searching rt by the vti tunnel dst/src parameter,
if this rt has neither attached to any transformation
nor the transformation is not tunnel oriented, this rt
should be released back to ip layer.

otherwise causing dst memory leakage.
Signed-off-by: NFan Du <fan.du@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_vti.c

@@ -126,6 +126,7 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (!rt->dst.xfrm ||
 	    rt->dst.xfrm->props.mode != XFRM_MODE_TUNNEL) {
 		dev->stats.tx_carrier_errors++;
+		ip_rt_put(rt);
 		goto tx_error_icmp;
 	}
 	tdev = rt->dst.dev;