Subject: Re: [PATCH] bonding: Allow tun-interfaces as slaves

From: Jörn Engel <[email-masked]>
Date: Tue, 9 Aug 2016 14:10:59 -0700

On Tue, Aug 09, 2016 at 12:06:36PM -0700, David Miller wrote:
> > On Tue, Aug 09, 2016 at 09:28:45PM +0800, Ding Tianhong wrote:
> > 
> > Simply not checking errors when setting the mac address solves the
> > problem for me.  No new features needed.
> 
> But it only works in certain modes.
> 
> So the best we can do is enforce the MAC address setting in the
> modes that absolutely require it.  We cannot ignore the MAC
> address setting unilaterally.

Something like this?

[PATCH] bonding: Allow tun-interfaces as slaves in balance-rr mode

Up until 00503b6f702e (part of 3.14-rc1), the bonding driver could be
used to enslave tun-interfaces.  00503b6f702e broke that behaviour,
afaics as an unintended side-effect.

For the purpose of bond-over-tun in balance-rr mode, simply ignoring the
error from dev_set_mac_address() is good enough.

Signed-off-by: Joern Engel <[email-masked]>
---
 drivers/net/bonding/bond_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 1f276fa30ba6..2f686bfe4304 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1490,7 +1490,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 		memcpy(addr.sa_data, bond_dev->dev_addr, bond_dev->addr_len);
 		addr.sa_family = slave_dev->type;
 		res = dev_set_mac_address(slave_dev, &addr);
-		if (res) {
+		/* round-robin mode works fine without a mac address */
+		if (res && BOND_MODE(bond) != BOND_MODE_ROUNDROBIN) {
 			netdev_dbg(bond_dev, "Error %d calling set_mac_address\n", res);
 			goto err_restore_mtu;
 		}
-- 
2.1.4