ipv6: dad: don't remove dynamic addresses if link is down

Currently, when the link for $DEV is down, this command succeeds but the
address is removed immediately by DAD (1):

    ip addr add 1111::12/64 dev $DEV valid_lft 3600 preferred_lft 1800

In the same situation, this will succeed and not remove the address (2):

    ip addr add 1111::12/64 dev $DEV
    ip addr change 1111::12/64 dev $DEV valid_lft 3600 preferred_lft 1800

The comment in addrconf_dad_begin() when !IF_READY makes it look like
this is the intended behavior, but doesn't explain why:

     * If the device is not ready:
     * - keep it tentative if it is a permanent address.
     * - otherwise, kill it.

We clearly cannot prevent userspace from doing (2), but we can make (1)
work consistently with (2).

addrconf_dad_stop() is only called in two cases: if DAD failed, or to
skip DAD when the link is down. In that second case, the fix is to avoid
deleting the address, like we already do for permanent addresses.

Fixes: 3c21edbd1137 ("[IPV6]: Defer IPv6 device initialization until the link becomes ready.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 5bea601aa3f59c2f974781f1ca6243e6d0f6086f..114fb64cf176c2c148d53c67c6dafa7891ae84aa 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1927,15 +1927,7 @@ static void addrconf_dad_stop(struct inet6_ifaddr *ifp, int dad_failed)
        if (dad_failed)
                ifp->flags |= IFA_F_DADFAILED;
 
-       if (ifp->flags&IFA_F_PERMANENT) {
-               spin_lock_bh(&ifp->lock);
-               addrconf_del_dad_work(ifp);
-               ifp->flags |= IFA_F_TENTATIVE;
-               spin_unlock_bh(&ifp->lock);
-               if (dad_failed)
-                       ipv6_ifa_notify(0, ifp);
-               in6_ifa_put(ifp);
-       } else if (ifp->flags&IFA_F_TEMPORARY) {
+       if (ifp->flags&IFA_F_TEMPORARY) {
                struct inet6_ifaddr *ifpub;
                spin_lock_bh(&ifp->lock);
                ifpub = ifp->ifpub;
@@ -1948,6 +1940,14 @@ static void addrconf_dad_stop(struct inet6_ifaddr *ifp, int dad_failed)
                        spin_unlock_bh(&ifp->lock);
                }
                ipv6_del_addr(ifp);
+       } else if (ifp->flags&IFA_F_PERMANENT || !dad_failed) {
+               spin_lock_bh(&ifp->lock);
+               addrconf_del_dad_work(ifp);
+               ifp->flags |= IFA_F_TENTATIVE;
+               spin_unlock_bh(&ifp->lock);
+               if (dad_failed)
+                       ipv6_ifa_notify(0, ifp);
+               in6_ifa_put(ifp);
        } else {
                ipv6_del_addr(ifp);
        }