usbnet: add new flag FLAG_NOARP for usb net devices

We do have some USB net devices, which cannot do ARP.
so we can introduce a new flag FLAG_NOARP, then client drivers
can easily handle this kind of devices
Signed-off-by: NWei Shuai <cpuwolf@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -1448,6 +1448,10 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 		if ((dev->driver_info->flags & FLAG_WWAN) != 0)
 			strcpy(net->name, "wwan%d");
 
+		/* devices that cannot do ARP */
+		if ((dev->driver_info->flags & FLAG_NOARP) != 0)
+			net->flags |= IFF_NOARP;
+
 		/* maybe the remote can't receive an Ethernet MTU */
 		if (net->mtu > (dev->hard_mtu - net->hard_header_len))
 			net->mtu = dev->hard_mtu - net->hard_header_len;

include/linux/usb/usbnet.h

@@ -100,6 +100,7 @@ struct driver_info {
 #define FLAG_LINK_INTR	0x0800		/* updates link (carrier) status */
 
 #define FLAG_POINTTOPOINT 0x1000	/* possibly use "usb%d" names */
+#define FLAG_NOARP	0x2000		/* device can't do ARP */
 
 /*
  * Indicates to usbnet, that USB driver accumulates multiple IP packets.