hyperv: Add support for vNIC hot removal

This patch adds proper handling of the vNIC hot removal event, which includes
a rescind-channel-offer message from the host side that triggers vNIC close and
removal. In this case, the notices to the host during close and removal is not
necessary because the channel is rescinded. This patch blocks these unnecessary
messages, and lets vNIC removal process complete normally.

Signed-off-by: Haiyang Zhang <[e-mail]>
Reviewed-by: K. Y. Srinivasan <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/hv/channel_mgmt.c

···
 		/* Just return here, no channel found */
 		return;
 
+	channel->rescind = true;
+
 	/* work is initialized for vmbus_process_rescind_offer() from
 	 * vmbus_process_offer() where the channel got created */
 	queue_work(channel->controlwq, &channel->work);

drivers/net/hyperv/netvsc.c

···
 		out_channel = device->channel;
 	packet->channel = out_channel;
 
+	if (out_channel->rescind)
+		return -ENODEV;
+
 	if (packet->page_buf_cnt) {
 		ret = vmbus_sendpacket_pagebuffer(out_channel,
 						  packet->page_buf,

drivers/net/hyperv/rndis_filter.c

···
 		return 0;
 
 	ret = rndis_filter_set_packet_filter(dev, 0);
+	if (ret == -ENODEV)
+		ret = 0;
+
 	if (ret == 0)
 		dev->state = RNDIS_DEV_INITIALIZED;
 

include/linux/hyperv.h

···
 	u8 monitor_grp;
 	u8 monitor_bit;
 
+	bool rescind; /* got rescind msg */
+
 	u32 ringbuffer_gpadlhandle;
 
 	/* Allocated memory for ring buffer */