net/ipv6: Bail early if user only wants cloned entries

Similar to IPv4, IPv6 fib no longer contains cloned routes. If a user
requests a route dump for only cloned entries, no sense walking the FIB
and returning everything.
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ip6_fib.c

@@ -586,10 +586,13 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 	} else if (nlmsg_len(nlh) >= sizeof(struct rtmsg)) {
 		struct rtmsg *rtm = nlmsg_data(nlh);
 
-		if (rtm->rtm_flags & RTM_F_PREFIX)
-			arg.filter.flags = RTM_F_PREFIX;
+		arg.filter.flags = rtm->rtm_flags & (RTM_F_PREFIX|RTM_F_CLONED);
 	}
 
+	/* fib entries are never clones */
+	if (arg.filter.flags & RTM_F_CLONED)
+		return skb->len;
+
 	w = (void *)cb->args[2];
 	if (!w) {
 		/* New dump: