Re: [PATCH] net/bonding: send arp in interval if no active slave

[Jarod Wilson]

On 2015-08-17 12:55 PM, Veaceslav Falico wrote:
> On Mon, Aug 17, 2015 at 12:23:03PM -0400, Jarod Wilson wrote:
> > From: Uwe Koziolek <uwe.koziolek@xxxxxxxxxxx>
> >
> > With some very finicky switch hardware, active backup bonding can get
> > into
> > a situation where we play ping-pong between interfaces, trying to get one
> > to come up as the active slave. There seems to be an issue with the
> > switch's arp replies either taking too long, or simply getting lost,
> > so we
> > wind up unable to get any interface up and active. Sometimes, the issue
> > sorts itself out after a while, sometimes it doesn't.
> >
> > Testing with num_grat_arp has proven fruitless, but sending an additional
> > arp on curr_arp_slave if we're still in the arp_interval timeslice in
> > bond_ab_arp_probe(), has shown to produce 100% reliability in testing
> > with
> > this hardware combination.
>
> Sorry, I don't understand the logic of why it works, and what exactly are
> we fixiing here.
>
> It also breaks completely the logic for link state management in case of no
> current active slave for 2*arp_interval.
>
> Could you please elaborate what exactly is fixed here, and how it works? :)

I can either duplicate some information from the bug, or Uwe can, to 
illustrate the exact nature of the problem.

> p.s. num_grat_arp maybe could help?

That was my thought as well, but as I understand it, that route was 
explored, and it didn't help any. I don't actually have a reproducer 
setup of my own, unfortunately, so I'm kind of caught in the middle here...

Uwe, can you perhaps further enlighten us as to what num_grat_arp 
settings were tried that didn't help? I'm still of the mind that if 
num_grat_arp *didn't* help, we probably need to do something keyed off 
num_grat_arp.


> > [jarod: manufacturing of changelog]
> > CC: Jay Vosburgh <j.vosburgh@xxxxxxxxx>
> > CC: Veaceslav Falico <vfalico@xxxxxxxxx>
> > CC: Andy Gospodarek <gospo@xxxxxxxxxxxxxxxxxxx>
> > CC: netdev@xxxxxxxxxxxxxxx
> > Signed-off-by: Uwe Koziolek <uwe.koziolek@xxxxxxxxxxx>
> > Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
> > ---
> > drivers/net/bonding/bond_main.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/net/bonding/bond_main.c
> > b/drivers/net/bonding/bond_main.c
> > index 0c627b4..60b9483 100644
> > --- a/drivers/net/bonding/bond_main.c
> > +++ b/drivers/net/bonding/bond_main.c
> > @@ -2794,6 +2794,11 @@ static bool bond_ab_arp_probe(struct bonding
> > *bond)
> >             return should_notify_rtnl;
> >     }
> >
> > +    if (bond_time_in_interval(bond, curr_arp_slave->last_link_up, 2)) {
> > +        bond_arp_send_all(bond, curr_arp_slave);
> > +        return should_notify_rtnl;
> > +    }
> > +
> >     bond_set_slave_inactive_flags(curr_arp_slave,
> > BOND_SLAVE_NOTIFY_LATER);
> >
> >     bond_for_each_slave_rcu(bond, slave, iter) {
> > --
> > 1.8.3.1


--
Jarod Wilson
jarod@xxxxxxxxxx
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