ipv6: Send unsolicited neighbour advertismements when notified

The NETDEV_NOTIFY_PEERS notifier is a request to send such
advertisements following migration to a different physical link,
e.g. virtual machine migration.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ndisc.c

@@ -611,6 +611,29 @@ static void ndisc_send_na(struct net_device *dev, struct neighbour *neigh,
 		     inc_opt ? ND_OPT_TARGET_LL_ADDR : 0);
 }
 
+static void ndisc_send_unsol_na(struct net_device *dev)
+{
+	struct inet6_dev *idev;
+	struct inet6_ifaddr *ifa;
+	struct in6_addr mcaddr;
+
+	idev = in6_dev_get(dev);
+	if (!idev)
+		return;
+
+	read_lock_bh(&idev->lock);
+	list_for_each_entry(ifa, &idev->addr_list, if_list) {
+		addrconf_addr_solict_mult(&ifa->addr, &mcaddr);
+		ndisc_send_na(dev, NULL, &mcaddr, &ifa->addr,
+			      /*router=*/ !!idev->cnf.forwarding,
+			      /*solicited=*/ false, /*override=*/ true,
+			      /*inc_opt=*/ true);
+	}
+	read_unlock_bh(&idev->lock);
+
+	in6_dev_put(idev);
+}
+
 void ndisc_send_ns(struct net_device *dev, struct neighbour *neigh,
 		   const struct in6_addr *solicit,
 		   const struct in6_addr *daddr, const struct in6_addr *saddr)
@@ -1723,6 +1746,9 @@ static int ndisc_netdev_event(struct notifier_block *this, unsigned long event,
 		neigh_ifdown(&nd_tbl, dev);
 		fib6_run_gc(~0UL, net);
 		break;
+	case NETDEV_NOTIFY_PEERS:
+		ndisc_send_unsol_na(dev);
+		break;
 	default:
 		break;
 	}