ipv6: do not send RTM_DELADDR for tentative addresses

RTM_NEWADDR notification is sent when IFA_F_TENTATIVE is cleared from
the address. So if the address is added and deleted before DAD probes
completes, the RTM_DELADDR will be sent for which there was no
RTM_NEWADDR causing asymmetry in notification. However if the same
logic is used while sending RTM_DELADDR notification, this asymmetry
can be avoided.

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
CC: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
CC: Patrick McHardy <kaber@trash.net>
CC: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -4888,6 +4888,13 @@ static void inet6_ifa_notify(int event, struct inet6_ifaddr *ifa)
 	struct net *net = dev_net(ifa->idev->dev);
 	int err = -ENOBUFS;
 
+	/* Don't send DELADDR notification for TENTATIVE address,
+	 * since NEWADDR notification is sent only after removing
+	 * TENTATIVE flag.
+	 */
+	if (ifa->flags & IFA_F_TENTATIVE && event == RTM_DELADDR)
+		return;
+
 	skb = nlmsg_new(inet6_ifaddr_msgsize(), GFP_ATOMIC);
 	if (!skb)
 		goto errout;