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[Xen-devel] RE: incompatibility of netfront driver with bonding module

To: "Yosuke Iwamatsu" <y-iwamatsu@xxxxxxxxxxxxx>
Subject: [Xen-devel] RE: incompatibility of netfront driver with bonding module
From: "Masroor Vettuparambil" <Masroor.Vettuparambil@xxxxxxxxxxxx>
Date: Fri, 4 Apr 2008 06:25:45 -0400
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Thread-topic: incompatibility of netfront driver with bonding module
Thanks for your work.
I could manage the live migration using a simple check in netfront while
resuming on destination.

if (!(netdev->flags & IFF_SLAVE))
        memcpy(netdev->dev_addr, info->mac, ETH_ALEN);
But this will work only if the interface is enslaved.

In your patch, should we let to change the MAC while interface is up? 
I need to include the support for arp link monitoring to netfront.


-----Original Message-----
From: Yosuke Iwamatsu [mailto:y-iwamatsu@xxxxxxxxxxxxx] 
Sent: Thursday, April 03, 2008 12:00 PM
To: Masroor Vettuparambil
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: incompatibility of netfront driver with bonding module


Masroor Vettuparambil wrote:
> 1. Normally, bonding will inherit the mac from the first slave and 
> assign it to all the other slaves added later. So the mac of vif will 
> be updated. But during migration, the mac of vif is getting updated 
> from xenstore(/vm/). So how about having a set_mac_address entry in 
> netfront that update the xenstore?

> So I need help, especially on #1. Is it ok to update the xenstore /vm/

> keys from domU? how to do this?

I tried a bit to find out the way to update /vm/ keys from frontend, but
didn't succeed. Either way, I don't think it is a good idea to update
the xenstore key of the vif mac address, because the original mac will
be lost and we won't be able to reset it e.g. after the guest reboot.

So the attached patch adds set mac_address() support to netfront.
It doesn't touch xenstore at all, but just preserves the modified mac
address in netfront_info structure and keeps using it after migration.

Yosuke Iwamatsu
         NEC Corporation

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