vrf: prevent adding upper devices

VRF devices don't work with upper devices. Currently, it's possible to
add a VRF device to a bridge or team, and to create macvlan, macsec, or
ipvlan devices on top of a VRF (bond and vlan are prevented respectively
by the lack of an ndo_set_mac_address op and the NETIF_F_VLAN_CHALLENGED
feature flag).

Fix this by setting the IFF_NO_RX_HANDLER flag (introduced in commit
f5426250a6 ("net: introduce IFF_NO_RX_HANDLER")).

Cc: David Ahern <dsahern@gmail.com>
Fixes: 193125dbd8 ("net: Introduce VRF device driver")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vrf.c

@@ -1273,6 +1273,7 @@ static void vrf_setup(struct net_device *dev)
 
 	/* default to no qdisc; user can add if desired */
 	dev->priv_flags |= IFF_NO_QUEUE;
+	dev->priv_flags |= IFF_NO_RX_HANDLER;
 
 	dev->min_mtu = 0;
 	dev->max_mtu = 0;