[PATCH] arp_notify: generate arp_notify event on NETDEV_CHANGE too

[Ian Campbell <ian.campbell@citrix.com>]

One of the use cases of the arp_notify functionality added in commit
eefef1 "net: add ARP notify option for devices" is to enable faster
network recovery after a virtual machine migration.

However a migration appears to the network subsystem as a temporary
loss of carrier rather than a down/up pair or an address change etc
therefore no gratuitous ARP is sent. Send one in the NETDEV_CHANGE
(generated by netif_carrier_{on,off}) case too. This catches carrier
down events too but that should be harmless.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: stable@kernel.org
---
 net/ipv4/devinet.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index e26f723..5b04124 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1081,6 +1081,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 		}
 		ip_mc_up(in_dev);
 		/* fall through */
+	case NETDEV_CHANGE:
 	case NETDEV_CHANGEADDR:
 		/* Send gratuitous ARP to notify of link change */
 		if (IN_DEV_ARP_NOTIFY(in_dev)) {
-- 
1.5.6.5