Subject: Re: [PATCH net-next] bonding: permit enslaving interfaces without set_mac support

From: Jay Vosburgh <[email-masked]>
Date: Thu, 17 Jul 2014 12:21:31 -0700

Veaceslav Falico <[email-masked]> wrote:

>Currently we exit if the slave isn't the first slave, doesn't support mac
>address setting and fail_over_mac isn't FOM_ACTIVE. It's wrong because we
>only require ndo_set_mac_address in case bonding is in active-backup mode
>and FOM isn't FOM_ACTIVE.
>
>To fix this - only exit with an error if we're in a/b mode and have
>fail_over_mac != FOM_ACTIVE.
>
>Also, maintain current behaviour on the first slave (forcibly change fom to
>FOM_ACTIVE) to not break anyone's configuration.

	I'm just catching up on this, so I apologize for being late to
the party here, but the main point of that test was to prohibit slaves
that cannot change their MAC from joining a bond whose mode requires
changing the MAC (which is all of them except for active-backup).

	It looks like the new code path will still fail when
bond_enslave() later on attempts to change the MAC, as long as
fail_over_mac is not set.  If f_o_m is set, the enslave will succeed,
after bypassing the dev_set_mac_address call.  That in turn would seem
to allow creating a bond of any mode, setting fail_over_mac, then
filling it with, e.g., ipoib devices.  That bond won't function
correctly in the modes other than active-backup.

	Am I missing something here?

	-J

>CC: Jay Vosburgh <[email-masked]>
>CC: Andy Gospodarek <[email-masked]>
>Signed-off-by: Veaceslav Falico <[email-masked]>
>---
> drivers/net/bonding/bond_main.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 09dc3ef..e0a33b5 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -1298,19 +1298,20 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
> 	}
> 
> 	if (slave_ops->ndo_set_mac_address == NULL) {
>-		if (!bond_has_slaves(bond)) {
>-			pr_warn("%s: Warning: The first slave device specified does not support setting the MAC address\n",
>-				bond_dev->name);
>-			if (BOND_MODE(bond) == BOND_MODE_ACTIVEBACKUP) {
>+		pr_warn("%s: Warning: The slave device specified does not support setting the MAC address\n",
>+			bond_dev->name);
>+		if (BOND_MODE(bond) == BOND_MODE_ACTIVEBACKUP &&
>+		    bond->params.fail_over_mac != BOND_FOM_ACTIVE) {
>+			if (!bond_has_slaves(bond)) {
> 				bond->params.fail_over_mac = BOND_FOM_ACTIVE;
> 				pr_warn("%s: Setting fail_over_mac to active for active-backup mode\n",
> 					bond_dev->name);
>+			} else {
>+				pr_err("%s: Error: The slave device specified does not support setting the MAC address, but fail_over_mac is not set to active\n",
>+				       bond_dev->name);
>+				res = -EOPNOTSUPP;
>+				goto err_undo_flags;
> 			}
>-		} else if (bond->params.fail_over_mac != BOND_FOM_ACTIVE) {
>-			pr_err("%s: Error: The slave device specified does not support setting the MAC address, but fail_over_mac is not set to active\n",
>-			       bond_dev->name);
>-			res = -EOPNOTSUPP;
>-			goto err_undo_flags;
> 		}
> 	}
> 
>-- 
>1.8.4
>

---
	-Jay Vosburgh, [email-masked]