[IPV6] NDISC: Ensure to send redirects.

rt6_lookup() is inappropriate because it cannot lookup
route to the source node of the original packet if
we don't have specific route to it.
Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>

net/ipv6/ndisc.c

@@ -1344,10 +1344,9 @@ void ndisc_send_redirect(struct sk_buff *skb, struct neighbour *neigh,
 
 	ndisc_flow_init(&fl, NDISC_REDIRECT, &saddr_buf, &skb->nh.ipv6h->saddr);
 
-	rt = rt6_lookup(&skb->nh.ipv6h->saddr, NULL, dev->ifindex, 1);
-	if (rt == NULL)
+	dst = ip6_route_output(NULL, &fl);
+	if (dst == NULL)
 		return;
-	dst = &rt->u.dst;
 
 	err = xfrm_lookup(&dst, &fl, NULL, 0);
 	if (err) {