ipv6: Add IFA_F_DADFAILED flag

Add IFA_F_DADFAILED flag to denote an IPv6 address that has
failed Duplicate Address Detection, that way tools like
/sbin/ip can be more informative.

3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 2001:db8::1/64 scope global tentative dadfailed
       valid_lft forever preferred_lft forever

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/if_addr.h

@@ -41,6 +41,7 @@ enum
 
 #define	IFA_F_NODAD		0x02
 #define IFA_F_OPTIMISTIC	0x04
+#define IFA_F_DADFAILED		0x08
 #define	IFA_F_HOMEADDRESS	0x10
 #define IFA_F_DEPRECATED	0x20
 #define IFA_F_TENTATIVE		0x40

net/ipv6/addrconf.c

@@ -1371,12 +1371,14 @@ struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, const struct in6_addr *add
 
 /* Gets referenced address, destroys ifaddr */
 
-static void addrconf_dad_stop(struct inet6_ifaddr *ifp)
+static void addrconf_dad_stop(struct inet6_ifaddr *ifp, int dad_failed)
 {
 	if (ifp->flags&IFA_F_PERMANENT) {
 		spin_lock_bh(&ifp->lock);
 		addrconf_del_timer(ifp);
 		ifp->flags |= IFA_F_TENTATIVE;
+		if (dad_failed)
+			ifp->flags |= IFA_F_DADFAILED;
 		spin_unlock_bh(&ifp->lock);
 		in6_ifa_put(ifp);
 #ifdef CONFIG_IPV6_PRIVACY
@@ -1422,7 +1424,7 @@ void addrconf_dad_failure(struct inet6_ifaddr *ifp)
 		}
 	}
 
-	addrconf_dad_stop(ifp);
+	addrconf_dad_stop(ifp, 1);
 }
 
 /* Join to solicited addr multicast group. */
@@ -2778,7 +2780,7 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp, u32 flags)
 	    idev->cnf.accept_dad < 1 ||
 	    !(ifp->flags&IFA_F_TENTATIVE) ||
 	    ifp->flags & IFA_F_NODAD) {
-		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC);
+		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC|IFA_F_DADFAILED);
 		spin_unlock_bh(&ifp->lock);
 		read_unlock_bh(&idev->lock);
 
@@ -2795,7 +2797,7 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp, u32 flags)
 		 * - otherwise, kill it.
 		 */
 		in6_ifa_hold(ifp);
-		addrconf_dad_stop(ifp);
+		addrconf_dad_stop(ifp, 0);
 		return;
 	}
 
@@ -2829,7 +2831,7 @@ static void addrconf_dad_timer(unsigned long data)
 		 * DAD was successful
 		 */
 
-		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC);
+		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC|IFA_F_DADFAILED);
 		spin_unlock_bh(&ifp->lock);
 		read_unlock_bh(&idev->lock);