[SRU][Trusty][PATCH 1/2] unregister_netdevice : move RTM_DELLINK to until after ndo_uninit

[Joseph Salisbury]

From: Roopa Prabhu <roopa at cumulusnetworks.com>

BugLink: http://bugs.launchpad.net/bugs/1525324

This patch fixes ordering of rtnl notifications during unregister_netdevice
by moving RTM_DELLINK notification to until after ndo_uninit.

The problem was seen with unregistering bond netdevices.

bond ndo_uninit callback generates a few RTM_NEWLINK notifications for
NETDEV_CHANGEADDR and NETDEV_FEAT_CHANGE. This is seen mostly when the
bond is deleted with slaves still enslaved to the bond.

During unregister netdevice (rollback_registered_many to be specific)
bond ndo_uninit is called after RTM_DELLINK notification goes out.
This results in userspace seeing RTM_DELLINK followed by a couple of
RTM_NEWLINK's.

In userspace problem was seen with libnl. libnl cache deletes the bond
when it sees RTM_DELLINK and re-adds the bond with the following
RTM_NEWLINK. Resulting in a stale bond entry in libnl cache when the kernel
has already deleted the bond.

This patch has been tested for bond, bridges and vlan devices.

Signed-off-by: Roopa Prabhu <roopa at cumulusnetworks.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit 56bfa7ee7c8892f1aa61797e4b8fec84b31d29b3)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 net/core/dev.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 31f1f68..69cd1cb 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5625,10 +5625,6 @@ static void rollback_registered_many(struct list_head *head)
 		*/
 		call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
 
-		if (!dev->rtnl_link_ops ||
-		    dev->rtnl_link_state == RTNL_LINK_INITIALIZED)
-			rtmsg_ifinfo(RTM_DELLINK, dev, ~0U, GFP_KERNEL);
-
 		/*
 		 *	Flush the unicast and multicast chains
 		 */
@@ -5638,6 +5634,10 @@ static void rollback_registered_many(struct list_head *head)
 		if (dev->netdev_ops->ndo_uninit)
 			dev->netdev_ops->ndo_uninit(dev);
 
+		if (!dev->rtnl_link_ops ||
+		    dev->rtnl_link_state == RTNL_LINK_INITIALIZED)
+			rtmsg_ifinfo(RTM_DELLINK, dev, ~0U, GFP_KERNEL);
+
 		/* Notifier chain MUST detach us all upper devices. */
 		WARN_ON(netdev_has_any_upper_dev(dev));
 
-- 
1.9.1