ipv6: Send netlink notification when DAD fails

If we are managing IPv6 addresses using DHCP, it would be nice
for user-space to be notified if an address configured through
DHCP fails DAD.  Otherwise user-space would have to poll to see
whether DAD succeeds.

This patch uses the existing notification mechanism and simply
hooks it into the DAD failure code path.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -1380,6 +1380,8 @@ static void addrconf_dad_stop(struct inet6_ifaddr *ifp, int dad_failed)
 		if (dad_failed)
 			ifp->flags |= IFA_F_DADFAILED;
 		spin_unlock_bh(&ifp->lock);
+		if (dad_failed)
+			ipv6_ifa_notify(0, ifp);
 		in6_ifa_put(ifp);
 #ifdef CONFIG_IPV6_PRIVACY
 	} else if (ifp->flags&IFA_F_TEMPORARY) {