bonding: register slave pointer for rx_handler

Register slave pointer as rx_handler data. That would eventually prevent
need to loop over slave devices to find the right slave.

Use synchronize_net to ensure that bond_handle_frame does not get slave
structure freed when working with that.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index c4e2343..ff9af31 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -266,6 +266,9 @@
 #endif /* CONFIG_DEBUG_FS */
 };
 
+#define bond_slave_get_rcu(dev) \
+	((struct slave *) rcu_dereference(dev->rx_handler_data))
+
 /**
  * Returns NULL if the net_device does not belong to any of the bond's slaves
  *