--- zzzz-none-000/linux-4.4.60/net/ipv6/addrconf.c	2017-04-08 07:53:53.000000000 +0000
+++ dragonfly-4020-701/linux-4.4.60/net/ipv6/addrconf.c	2018-11-08 13:36:17.000000000 +0000
@@ -1768,6 +1768,35 @@
 	return result;
 }
 
+/* ipv6_dev_find()
+ *	Find (and hold) net device that has the given address.
+ *	Or NULL on failure.
+ */
+struct net_device *ipv6_dev_find(struct net *net, struct in6_addr *addr,
+				 int strict)
+{
+	struct inet6_ifaddr *ifp;
+	struct net_device *dev;
+
+	ifp = ipv6_get_ifaddr(net, addr, NULL, strict);
+	if (!ifp)
+		return NULL;
+
+	if (!ifp->idev) {
+		in6_ifa_put(ifp);
+		return NULL;
+	}
+
+	dev = ifp->idev->dev;
+	if (dev)
+		dev_hold(dev);
+
+	in6_ifa_put(ifp);
+
+	return dev;
+}
+EXPORT_SYMBOL(ipv6_dev_find);
+
 /* Gets referenced address, destroys ifaddr */
 
 static void addrconf_dad_stop(struct inet6_ifaddr *ifp, int dad_failed)