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Date: Sat, 21 Feb 2015 17:59:45 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jay Vosburgh <jay.vosburgh@...onical.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>, davem@...emloft.net,
vfalico@...il.com, andy@...yhouse.net, netdev@...r.kernel.org
Subject: Re: [PATCH] bonding: ban stacked bonding support
Sat, Feb 21, 2015 at 12:14:00AM CET, jay.vosburgh@...onical.com wrote:
>Alexey Dobriyan <adobriyan@...il.com> wrote:
>
>>Does Linux support it at all?
>>
>>In short: if you add bonding master as a slave, and then release it,
>>it will no longer be a IFF_BONDING creating problems like described at
>>https://bugzilla.kernel.org/show_bug.cgi?id=89541
>>
>> echo +bond1 >/sys/class/net/bonding_masters
>> echo 1 >/sys/class/net/bond1/bonding/mode
>> echo +bond2 >/sys/class/net/bonding_masters
>> echo +bond2 >/sys/class/net/bond1/bonding/slaves
>> echo -bond2 >/sys/class/net/bond1/bonding/slaves
>> echo -bond2 >/sys/class/net/bonding_masters
>>
>> cat /proc/net/bonding/bond2 # should not exist
>> [oops]
>>
>>Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
>
> I think it's time to disallow stacking like this; it never
>really worked quite right as far as I can remember, and I thought it was
>disallowed at some point in the past. I don't believe the stacked bonds
>function correctly for receive in the current kernel, either, although
>I'd have to test it again to confirm that.
>
> The usual case for desiring to stack bonds is an active-backup
>pair of LACP / 802.3ad bonds (such as the bugzilla referenced above),
>but the 802.3ad mode handles this situation internally, so no stack is
>necessary.
Exactly. There is no real use-case for stacked bonding.
>
>>---
>>
>> drivers/net/bonding/bond_main.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>>--- a/drivers/net/bonding/bond_main.c
>>+++ b/drivers/net/bonding/bond_main.c
>>@@ -1248,6 +1248,11 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>> slave_dev->name);
>> }
>>
>>+ if (slave_dev->flags & IFF_MASTER) {
>>+ netdev_dbg(bond_dev, "stacked bonding not supported\n");
>>+ return -EBUSY;
>>+ }
>>+
>> /* already enslaved */
>> if (slave_dev->flags & IFF_SLAVE) {
>> netdev_dbg(bond_dev, "Error: Device was already enslaved\n");
>
> Instead of a separate block for IFF_MASTER, the IFF_SLAVE line
>could be replaced with something like:
>
> if (netif_is_bond_slave(slave_dev) || netif_is_bond_master(slave_dev)) {
> netdev_dbg(bond_dev, "Error: Device is bond slave or master\n");
>
> With that caveat:
>
>Signed-off-by: Jay Vosburgh <jay.vosburgh@...onical.com>
>
> This is probably a good candidate for -stable as well.
>
> -J
>
>---
> -Jay Vosburgh, jay.vosburgh@...onical.com
>--
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