netdev - Re: Cannot move macvlan interface on top of bonding device

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Message-ID: <5419F17D.2090409@gmail.com>
Date:	Wed, 17 Sep 2014 16:39:25 -0400
From:	Vlad Yasevich <vyasevich@...il.com>
To:	Florian Westphal <fw@...len.de>, Cong Wang <cwang@...pensource.com>
CC:	Francesco Ruggeri <fruggeri@...sta.com>,
	netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Weilong Chen <chenweilong@...wei.com>
Subject: Re: Cannot move macvlan interface on top of bonding device

On 09/17/2014 03:06 PM, Florian Westphal wrote:
> Cong Wang <cwang@...pensource.com> wrote:
>> On Wed, Sep 17, 2014 at 8:56 AM, Francesco Ruggeri <fruggeri@...sta.com> wrote:
>>> This used to work in older releases.
>>> The problem seems to be that commit f939981492 sets NETIF_F_NETNS_LOCAL
>>> on bonding interfaces, and commit 797f87f83 causes macvlan interfaces
>>> to inherit its features from the lower device.
>>>
>>> Is there a reason why NETIF_F_NETNS_LOCAL should be inherited from the
>>> lower device
>>> by macvlan interfaces?
>>
>> commit 797f87f83 looks wrong, it should not inherit NETIF_F_NETNS_LOCAL,
>> so just clear this flag. Please submit a patch.
> 
> Under which conditions would NETIF_F_NETNS_LOCAL have to be inherited?
> (i.e., why is it inheritable in the first place?)

macvlan code calls
        features = netdev_increment_features(vlan->lowerdev->features,
                                             features,
                                             mask);

where lowerdev->features contains the NETIF_F_NETNS_LOCAL bit.  That
bit is not set in features or in mask.  It is also not one of the ALL_FOR_ALL
bits so it's not turned off.

As an example, here are the values from a quit test I ran:

bond features = 0x400f3888
features = 0x3b5a09  (mask is the same).
incremented features = 0x41bf389

NETIF_F_NETNS_LOCAL is still on.

May be a better solution is:

        features = netdev_increment_features(vlan->lowerdev->features & MACVLAN_FEATURS,
                                             features,
                                             mask);

This way we start with only the feature MACVLAN is interested in.

-vlad

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