Re: [PATCH net] net/bonding: Enforce active-backup policy for IPoIB bonds

[Andy Gospodarek <gospo@cumulusnetworks.com>]

On Wed, Jul 20, 2016 at 05:44:20PM +0300, Saeed Mahameed wrote:
> From: Mark Bloch <markb@mellanox.com>
> 
> When using an IPoIB bond currently only active-backup mode is a valid
> use case and this commit strengthens it.
> 
> Since commit 2ab82852a270 ("net/bonding: Enable bonding to enslave
> netdevices not supporting set_mac_address()") was introduced till
> 4.7-rc1, IPoIB didn't support the set_mac_address ndo, and hence
> the fail over mac policy always applied to IPoIB bonds.
> 
> With the introduction of commit 492a7e67ff83 ("IB/IPoIB: Allow setting
> the device address"), that doesn't hold and practically IPoIB bonds are
> broken as of that. To fix it, lets go to fail over mac if the device
> doesn't support the ndo OR this is IPoIB device.
> 
> As a by-product, this commit also prevents a stack corruption which
> occurred when trying to copy 20 bytes (IPoIB) device address
> to a sockaddr struct that has only 16 bytes of storage.
> 
> Signed-off-by: Mark Bloch <markb@mellanox.com>
> Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
> ---
>  drivers/net/bonding/bond_main.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index a2afa3b..ccd4003 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1422,7 +1422,15 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>  		return -EINVAL;
>  	}
>  
> -	if (slave_ops->ndo_set_mac_address == NULL) {
> +	if (slave_dev->type == ARPHRD_INFINIBAND &&
> +	    BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP) {
> +		netdev_warn(bond_dev, "Type (%d) supports only active-backup mode\n",
> +			    slave_dev->type);

Seems like we should propagate the failure back to the caller.
Something like this?

		return -EOPNOTSUPP;
> +		goto err_undo_flags;
> +	}
> +
> +	if (!slave_ops->ndo_set_mac_address ||
> +	    slave_dev->type == ARPHRD_INFINIBAND) {
>  		netdev_warn(bond_dev, "The slave device specified does not support setting the MAC address\n");
>  		if (BOND_MODE(bond) == BOND_MODE_ACTIVEBACKUP &&
>  		    bond->params.fail_over_mac != BOND_FOM_ACTIVE) {

The rest of the patch seems logical, so I'm fine with it.