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Groups > linux.kernel > #1691553

[PATCH 3.18 04/28] ipv6: dad: dont remove dynamic addresses if link is down

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3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sabrina Dubroca <sd@queasysnail.net>

commit ec8add2a4c9df723c94a863b8fcd6d93c472deed upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/ipv6/addrconf.c |   22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1613,17 +1613,7 @@ struct inet6_ifaddr *ipv6_get_ifaddr(str
 
 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_dad_work(ifp);
-		ifp->flags |= IFA_F_TENTATIVE;
-		if (dad_failed)
-			ifp->flags |= IFA_F_DADFAILED;
-		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;
@@ -1636,6 +1626,16 @@ static void addrconf_dad_stop(struct ine
 			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;
+		if (dad_failed)
+			ifp->flags |= IFA_F_DADFAILED;
+		spin_unlock_bh(&ifp->lock);
+		if (dad_failed)
+			ipv6_ifa_notify(0, ifp);
+		in6_ifa_put(ifp);
 	} else {
 		ipv6_del_addr(ifp);
 	}

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[PATCH 3.18 00/28] 3.18.62-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:20 +0200
  [PATCH 3.18 22/28] crypto: atmel - only treat EBUSY as transient if backlog Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:20 +0200
  [PATCH 3.18 25/28] sched/topology: Optimize build_group_mask() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:20 +0200
  [PATCH 3.18 16/28] fs/dcache.c: fix spin lockup issue on nlru->lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:20 +0200
  [PATCH 3.18 19/28] vt: fix unchecked __put_user() in tioclinux ioctls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:20 +0200
  [PATCH 3.18 12/28] parisc: DMA API: return error instead of BUG_ON for dma ops on non dma devs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:20 +0200
  [PATCH 3.18 08/28] cfg80211: Check if PMKID attribute is of expected size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 09/28] irqchip/gic-v3: Fix out-of-bound access in gic_set_affinity Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 03/28] net: prevent sign extension in dev_get_stats() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 14/28] tools/lib/lockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain/: Depth Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 23/28] crypto: sha1-ssse3 - Disable avx2 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 07/28] cfg80211: Validate frequencies nested in NL80211_ATTR_SCAN_FREQUENCIES Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 01/28] ipv6: avoid unregistering inet6_dev for loopback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 04/28] ipv6: dad: dont remove dynamic addresses if link is down Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  [PATCH 3.18 11/28] parisc: use compat_sys_keyctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 13:30 +0200
  Re: [PATCH 3.18 00/28] 3.18.62-stable review Guenter Roeck <linux@roeck-us.net> - 2017-07-19 22:40 +0200
  Re: [PATCH 3.18 00/28] 3.18.62-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-07-20 01:50 +0200
    Re: [PATCH 3.18 00/28] 3.18.62-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-20 07:10 +0200

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