[PATCH] Hyperv: Trigger DHCP renew after host hibernation

[Yue Zhang <yuezha@microsoft.com>]

From: Yue Zhang <yuezha@microsoft.com>

This patch addresses the comment from Olaf Hering and Greg KH
for a previous commit 3a494e710367 ("hyperv: Add handler for
RNDIS_STATUS_NETWORK_CHANGE event")

In previous solution, the driver calls "network restart" to
force a DHCP renew when the host is back from hibernation.

In this fix, the driver will keep network carrier offline for
10 seconds and then bring it back. So that ifplugd daemon will
notice this change and refresh DHCP lease.

Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>

Signed-off-by: Yue Zhang <yuezha@microsoft.com>
---
 drivers/net/hyperv/netvsc_drv.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index a9c5eaa..559c97d 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -33,6 +33,7 @@
 #include <linux/if_vlan.h>
 #include <linux/in.h>
 #include <linux/slab.h>
+#include <linux/delay.h>
 #include <net/arp.h>
 #include <net/route.h>
 #include <net/sock.h>
@@ -792,8 +793,7 @@ static void netvsc_link_change(struct work_struct *w)
 	struct netvsc_device *net_device;
 	struct rndis_device *rdev;
 	bool notify, refresh = false;
-	char *argv[] = { "/etc/init.d/network", "restart", NULL };
-	char *envp[] = { "HOME=/", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL };
+	int delay;
 
 	rtnl_lock();
 
@@ -816,8 +816,21 @@ static void netvsc_link_change(struct work_struct *w)
 
 	rtnl_unlock();
 
-	if (refresh)
-		call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+	if (refresh) {
+		/*
+		 * Keep the carrier offline for 10 seconds
+		 * to notify ifplugd daemon network change
+		 */
+		for (delay = 0; delay < 10; delay++) {
+			rtnl_lock();
+			netif_carrier_off(net);
+			rtnl_unlock();
+			ssleep(1);
+		}
+		rtnl_lock();
+		netif_carrier_on(net);
+		rtnl_unlock();
+	}
 
 	if (notify)
 		netdev_notify_peers(net);
-- 
1.9.1