netdev - Re: Bonding problem

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Date:	Mon, 8 Aug 2011 13:31:02 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	Jay Vosburgh <fubar@...ibm.com>
Cc:	Andy Gospodarek <andy@...yhouse.net>,
	Eduard Sinelnikov <eduard.sinelnikov@...il.com>,
	netdev@...r.kernel.org
Subject: Re: Bonding problem

On Mon, Aug 08, 2011 at 10:06:05AM -0700, Jay Vosburgh wrote:
> 
> Andy Gospodarek <andy@...yhouse.net> wrote:
> 
> >On Sun, Aug 07, 2011 at 03:00:30PM +0300, Eduard Sinelnikov wrote:
> >> Hi,
> >> 
> >> In the kernel 2.6.39.3 ( /drivers/net/bond/bond_main.c).
> >> In the function  ‘bond_xmit_roundrobin’
> >> The code check if the bond is active via
> >> ‘bond_is_active_slave(slave)’ Function call.
> >> Which actually checks if the slave is backup or active
> >> What is the meaning of slave being  backup in round robin mode?
> >> Correct me if I wrong but in round robin every slave should send a
> >> packet, regardless of being active or backup.
> >> 
> >> Thank you,
> >>            Eduard
> >
> >There probably is not a compelling reason to continue to have it.  There
> >may be a reason historically, but I'm not aware what that might be at
> >this point.  For modes other than active-backup, the value of
> >slave->link and slave->backup should always contain a value that
> >indicates the slave is up and available for transmit.
> 
> 	If you read Eduard's other posts regarding this, the actual
> issue is that when changing from another mode into round-robin,
> occasionally slaves will still be marked as "backup" and won't be used:
> 

I did notice that one after I sent this first response.

> >Date: 	Mon, 8 Aug 2011 11:16:39 +0300
> >Subject: On line Bonding configuration change fails
> >From: Eduard Sinelnikov <eduard.sinelnikov@...il.com>
> >To: netdev@...r.kernel.org
> >Sender: netdev-owner@...r.kernel.org
> >
> >Hi,
> >
> >My configuration is a follows:
> >
> >             | eth0 -------------->
> >Ububntu | eth1 -------------->    Swith ------------> Other computer
> >
> >Scenario:
> >• change the bond mode to active/backup
> >• unplug some of the cable
> >• plug-in the unplugged cable
> >• change bond mode to round robin
> >
> >I can see that only one eth1 is sending data. When I unplug it the ping stops.
> >
> >Is it a bug or some mis-configuration?
> >
> >In the kernel ( /drivers/net/bond/bond_main.c).
> >In the function  ‘bond_xmit_roundrobin
> >’
> >The code check if the bond is active via
> >‘bond_is_active_slave(slave)’ Function call.
> >Which actually checks if the slave is backup or active
> >What is the meaning of backup in round robin?
> >Correct me if I wrong but in round robin every slave should send a
> >packet, regardless of being active or backup.
> 
> 	So from looking at the code, it seems that the actual problem is
> that when transitioning to round-robin mode, one or more slaves can
> remain marked as "backup," and in round-robin mode, that won't ever
> change.  We could probably work around that by removing the "is_active"
> test (essentially declaring that "is_active" is only valid in
> active-backup mode).  That might produce a few odd messages here and
> there (when removing a slave or during a link failure, for example).
> 
> 	From inspection, the bond_xmit_xor function likely has this same
> problem.
> 

Agreed.

> 	-J
> 
> ---
> 	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
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