hv_netvsc: avoid repeated updates of packet filter

The netvsc driver can get repeated calls to netvsc_rx_mode during
network setup; each of these calls ends up scheduling the lower
layers to update tha packet filter. This update requires an
request/response to the host. So avoid doing this if we already
know that the correct packet filter value is set.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -173,6 +173,7 @@ struct rndis_device {
 	struct list_head req_list;
 
 	struct work_struct mcast_work;
+	u32 filter;
 
 	bool link_state;        /* 0 - link up, 1 - link down */
 

drivers/net/hyperv/rndis_filter.c

@@ -825,13 +825,15 @@ static int rndis_filter_set_packet_filter(struct rndis_device *dev,
 	struct rndis_set_request *set;
 	int ret;
 
+	if (dev->filter == new_filter)
+		return 0;
+
 	request = get_rndis_request(dev, RNDIS_MSG_SET,
 			RNDIS_MESSAGE_SIZE(struct rndis_set_request) +
 			sizeof(u32));
 	if (!request)
 		return -ENOMEM;
 
-
 	/* Setup the rndis set */
 	set = &request->request_msg.msg.set_req;
 	set->oid = RNDIS_OID_GEN_CURRENT_PACKET_FILTER;
@@ -842,8 +844,10 @@ static int rndis_filter_set_packet_filter(struct rndis_device *dev,
 	       &new_filter, sizeof(u32));
 
 	ret = rndis_filter_send_request(dev, request);
-	if (ret == 0)
+	if (ret == 0) {
 		wait_for_completion(&request->wait_event);
+		dev->filter = new_filter;
+	}
 
 	put_rndis_request(dev, request);