Or Gerlitz [off-list ref] wrote:
[...]
+	bond->dev->mtu		    = new_active->dev->mtu;

	This won't generate a NETDEV_CHANGEMTU notifier event.

[...]

+		/* bonding netdevices are created with ether_setup, so when the
+		 * slave type is not ARPHRD_ETHER there is a need to override
+		 * some of the type dependent attributes/functions
+		 */
+		if (new_active && new_active->dev->type != ARPHRD_ETHER)
+			bond_setup_by_slave(bond, new_active);
+

	In this case, if the bond has one slave that's ARPHRD_ETHER and
one that's not, when the active changes from the non-ARPHRD_ETHER slave
to the ARPHRD_ETHER slave, it won't call bond_setup_by_slave() to switch
the hard_header, rebuild_header, et al, back to the ARPHRD_ETHER
settings.

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com