netdev - Re: [patch net-next] bonding: allow to add vlans on top of empty bond

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Date:	Fri, 27 Jun 2014 09:08:50 -0700
From:	Jay Vosburgh <jay.vosburgh@...onical.com>
To:	Tom Gundersen <teg@...m.no>
cc:	Jiri Pirko <jiri@...nulli.us>, netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>, vfalico@...il.com,
	andy@...yhouse.net
Subject: Re: [patch net-next] bonding: allow to add vlans on top of empty bond

Tom Gundersen <teg@...m.no> wrote:

>Hi Jiri,
>
>On Fri, Jun 27, 2014 at 4:13 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>> This limitation maybe had some reason in the past, but now there is not
>> one -> removing this.
>
>If this restriction is really no longer needed, it would be very
>helpful if we could drop it. See for instnace
><https://bugs.freedesktop.org/show_bug.cgi?id=76077#c5>.

	The reason for the restriction is that, in the past, the bond
did not have a MAC address until the first slave was added, so adding a
VLAN wouldn't work properly.

	Currently, a random MAC is assigned to the bond when there are
no slaves, so that problem is no longer an issue (as presumably the VLAN
can handle the MAC change when the first slave goes in to the bond).

	While you're at it, you might want to also check and possibly
remove some of the MAC-related warnings related to removing the last
slave, e.g.,

        if (!bond_has_slaves(bond)) {
                bond_set_carrier(bond);
                eth_hw_addr_random(bond_dev);

                if (vlan_uses_dev(bond_dev)) {
                        pr_warn("%s: Warning: clearing HW address of %s while it still has VLANs\n",
                                bond_dev->name, bond_dev->name);
                        pr_warn("%s: When re-adding slaves, make sure the bond's HW address matches its VLANs\n",
                                bond_dev->name);
                }
        }

	This warning may not be useful any longer, since the MAC should
update correctly without user action when re-adding the first slave.

	-J


>Cheers,
>
>Tom
>
>> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
>> ---
>>  drivers/net/bonding/bond_main.c | 13 -------------
>>  1 file changed, 13 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 3a451b6..ffefb70 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -1001,12 +1001,6 @@ static netdev_features_t bond_fix_features(struct net_device *dev,
>>         netdev_features_t mask;
>>         struct slave *slave;
>>
>> -       if (!bond_has_slaves(bond)) {
>> -               /* Disable adding VLANs to empty bond. But why? --mq */
>> -               features |= NETIF_F_VLAN_CHALLENGED;
>> -               return features;
>> -       }
>> -
>>         mask = features;
>>         features &= ~NETIF_F_ONE_FOR_ALL;
>>         features |= NETIF_F_ALL_FOR_ALL;
>> @@ -3956,13 +3950,6 @@ void bond_setup(struct net_device *bond_dev)
>>         bond_dev->priv_flags |= IFF_BONDING | IFF_UNICAST_FLT;
>>         bond_dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE | IFF_TX_SKB_SHARING);
>>
>> -       /* At first, we block adding VLANs. That's the only way to
>> -        * prevent problems that occur when adding VLANs over an
>> -        * empty bond. The block will be removed once non-challenged
>> -        * slaves are enslaved.
>> -        */
>> -       bond_dev->features |= NETIF_F_VLAN_CHALLENGED;
>> -
>>         /* don't acquire bond device's netif_tx_lock when
>>          * transmitting */
>>         bond_dev->features |= NETIF_F_LLTX;
>> --
>> 1.9.0

---
	-Jay Vosburgh, jay.vosburgh@...onical.com
--
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