ipv6: resend MLD report if a link-local address completes DAD

RFC3590/RFC3810 specifies we should resend MLD reports as soon as a
valid link-local address is available.

We now use the valid_ll_addr_cnt to check if it is necessary to resend
a new report.

Changes since Flavio Leitner's version:
a) adapt for valid_ll_addr_cnt
b) resend first reports directly in the path and just arm the timer for
   mc_qrv-1 resends.

Reported-by: Flavio Leitner <fleitner@redhat.com>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: David Stevens <dlstevens@us.ibm.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -3277,7 +3277,7 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
 {
 	struct net_device *dev = ifp->idev->dev;
 	struct in6_addr lladdr;
-	bool send_rs;
+	bool send_rs, send_mld;
 
 	addrconf_del_dad_timer(ifp);
 
@@ -3293,14 +3293,21 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
 
 	read_lock_bh(&ifp->idev->lock);
 	spin_lock(&ifp->lock);
-	send_rs = ipv6_accept_ra(ifp->idev) &&
+	send_mld = ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL &&
+		   ifp->idev->valid_ll_addr_cnt == 1;
+	send_rs = send_mld &&
+		  ipv6_accept_ra(ifp->idev) &&
 		  ifp->idev->cnf.rtr_solicits > 0 &&
-		  (dev->flags&IFF_LOOPBACK) == 0 &&
-		  ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL &&
-		  ifp->idev->valid_ll_addr_cnt == 1;
+		  (dev->flags&IFF_LOOPBACK) == 0;
 	spin_unlock(&ifp->lock);
 	read_unlock_bh(&ifp->idev->lock);
 
+	/* While dad is in progress mld report's source address is in6_addrany.
+	 * Resend with proper ll now.
+	 */
+	if (send_mld)
+		ipv6_mc_dad_complete(ifp->idev);
+
 	if (send_rs) {
 		/*
 		 *	If a host as already performed a random delay