ipv6: Log the explicit address that triggered DAD failure

If an interface has multiple addresses, the current message for DAD
failure isn't really helpful, so this patch adds the address itself to
the printk.
Signed-off-by: NJens Rosenboom <jens@mcbone.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ndisc.c

@@ -955,8 +955,8 @@ static void ndisc_recv_na(struct sk_buff *skb)
 		 */
 		if (skb->pkt_type != PACKET_LOOPBACK)
 			ND_PRINTK1(KERN_WARNING
-			   "ICMPv6 NA: someone advertises our address on %s!\n",
-			   ifp->idev->dev->name);
+			   "ICMPv6 NA: someone advertises our address %pI6 on %s!\n",
+			   &ifp->addr, ifp->idev->dev->name);
 		in6_ifa_put(ifp);
 		return;
 	}