staging: hv: Fix GARP not sent after Quick Migration

After Quick Migration, the network is not immediately operational in the
current context when receiving RNDIS_STATUS_MEDIA_CONNECT event. So, I added
another netif_notify_peers() into a scheduled work, otherwise GARP packet will
not be sent after quick migration, and cause network disconnection.

Thanks to Mike Surcouf <mike@surcouf.co.uk> for reporting the bug and
testing the patch.
Reported-by: Mike Surcouf <mike@surcouf.co.uk>
Tested-by: Mike Surcouf <mike@surcouf.co.uk>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Abhishek Kane <v-abkane@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/netvsc_drv.c

@@ -46,6 +46,7 @@ struct net_device_context {
 	/* point back to our device context */
 	struct hv_device *device_ctx;
 	unsigned long avail;
+	struct work_struct work;
 };
 
 
@@ -219,6 +220,7 @@ static void netvsc_linkstatus_callback(struct hv_device *device_obj,
 				       unsigned int status)
 {
 	struct net_device *net = dev_get_drvdata(&device_obj->device);
+	struct net_device_context *ndev_ctx;
 
 	if (!net) {
 		DPRINT_ERR(NETVSC_DRV, "got link status but net device "
@@ -230,6 +232,8 @@ static void netvsc_linkstatus_callback(struct hv_device *device_obj,
 		netif_carrier_on(net);
 		netif_wake_queue(net);
 		netif_notify_peers(net);
+		ndev_ctx = netdev_priv(net);
+		schedule_work(&ndev_ctx->work);
 	} else {
 		netif_carrier_off(net);
 		netif_stop_queue(net);
@@ -328,6 +332,25 @@ static const struct net_device_ops device_ops = {
 	.ndo_set_mac_address =		eth_mac_addr,
 };
 
+/*
+ * Send GARP packet to network peers after migrations.
+ * After Quick Migration, the network is not immediately operational in the
+ * current context when receiving RNDIS_STATUS_MEDIA_CONNECT event. So, add
+ * another netif_notify_peers() into a scheduled work, otherwise GARP packet
+ * will not be sent after quick migration, and cause network disconnection.
+ */
+static void netvsc_send_garp(struct work_struct *w)
+{
+	struct net_device_context *ndev_ctx;
+	struct net_device *net;
+
+	msleep(20);
+	ndev_ctx = container_of(w, struct net_device_context, work);
+	net = dev_get_drvdata(&ndev_ctx->device_ctx->device);
+	netif_notify_peers(net);
+}
+
+
 static int netvsc_probe(struct device *device)
 {
 	struct hv_driver *drv =
@@ -353,6 +376,7 @@ static int netvsc_probe(struct device *device)
 	net_device_ctx->device_ctx = device_obj;
 	net_device_ctx->avail = ring_size;
 	dev_set_drvdata(device, net);
+	INIT_WORK(&net_device_ctx->work, netvsc_send_garp);
 
 	/* Notify the netvsc driver of the new device */
 	ret = net_drv_obj->base.dev_add(device_obj, &device_info);