net: allow vlan traffic to be received under bond

The following configuration used to work as I expected. At least
we could use the fcoe interfaces to do MPIO and the bond0 iface
to do load balancing or failover.

       ---eth2.228-fcoe
       |
eth2 -----|
          |
          |---- bond0
          |
eth3 -----|
       |
       ---eth3.228-fcoe

This worked because of a change we added to allow inactive slaves
to rx 'exact' matches. This functionality was kept intact with the
rx_handler mechanism. However now the vlan interface attached to the
active slave never receives traffic because the bonding rx_handler
updates the skb->dev and goto's another_round. Previously, the
vlan_do_receive() logic was called before the bonding rx_handler.

Now by the time vlan_do_receive calls vlan_find_dev() the
skb->dev is set to bond0 and it is clear no vlan is attached
to this iface. The vlan lookup fails.

This patch moves the VLAN check above the rx_handler. A VLAN
tagged frame is now routed to the eth2.228-fcoe iface in the
above schematic. Untagged frames continue to the bond0 as
normal. This case also remains intact,

eth2 --> bond0 --> vlan.228

Here the skb is VLAN tagged but the vlan lookup fails on eth2
causing the bonding rx_handler to be called. On the second
pass the vlan lookup is on the bond0 iface and completes as
expected.

Putting a VLAN.228 on both the bond0 and eth2 device will
result in eth2.228 receiving the skb. I don't think this is
completely unexpected and was the result prior to the rx_handler
result.

Note, the same setup is also used for other storage traffic that
MPIO is used with eg. iSCSI and similar setups can be contrived
without storage protocols.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Reviewed-by: Jiri Pirko <jpirko@redhat.com>
Tested-by: Hans Schillstrom <hams.schillstrom@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>