linux-kernel - Re: [PATCH net] bonding/802.3ad: fix slave link initialization transition states

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Date:   Fri, 24 May 2019 15:38:46 -0700
From:   Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
To:     Jay Vosburgh <jay.vosburgh@...onical.com>
Cc:     Jarod Wilson <jarod@...hat.com>, linux-kernel@...r.kernel.org,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>,
        linux-netdev <netdev@...r.kernel.org>,
        Heesoon Kim <Heesoon.Kim@...atus.com>
Subject: Re: [PATCH net] bonding/802.3ad: fix slave link initialization
 transition states

On Fri, May 24, 2019 at 2:17 PM Jay Vosburgh <jay.vosburgh@...onical.com> wrote:
>
> Jarod Wilson <jarod@...hat.com> wrote:
>
> >Once in a while, with just the right timing, 802.3ad slaves will fail to
> >properly initialize, winding up in a weird state, with a partner system
> >mac address of 00:00:00:00:00:00. This started happening after a fix to
> >properly track link_failure_count tracking, where an 802.3ad slave that
> >reported itself as link up in the miimon code, but wasn't able to get a
> >valid speed/duplex, started getting set to BOND_LINK_FAIL instead of
> >BOND_LINK_DOWN. That was the proper thing to do for the general "my link
> >went down" case, but has created a link initialization race that can put
> >the interface in this odd state.
>
Are there any notification consequences because of this change?

>        Reading back in the git history, the ultimate cause of this
> "weird state" appears to be devices that assert NETDEV_UP prior to
> actually being able to supply sane speed/duplex values, correct?
>
>         Presuming that this is the case, I don't see that there's much
> else to be done here, and so:
>
> Acked-by: Jay Vosburgh <jay.vosburgh@...onical.com>
>
> >The simple fix is to instead set the slave link to BOND_LINK_DOWN again,
> >if the link has never been up (last_link_up == 0), so the link state
> >doesn't bounce from BOND_LINK_DOWN to BOND_LINK_FAIL -- it hasn't failed
> >in this case, it simply hasn't been up yet, and this prevents the
> >unnecessary state change from DOWN to FAIL and getting stuck in an init
> >failure w/o a partner mac.
> >
> >Fixes: ea53abfab960 ("bonding/802.3ad: fix link_failure_count tracking")
> >CC: Jay Vosburgh <j.vosburgh@...il.com>
> >CC: Veaceslav Falico <vfalico@...il.com>
> >CC: Andy Gospodarek <andy@...yhouse.net>
> >CC: "David S. Miller" <davem@...emloft.net>
> >CC: netdev@...r.kernel.org
> >Tested-by: Heesoon Kim <Heesoon.Kim@...atus.com>
> >Signed-off-by: Jarod Wilson <jarod@...hat.com>
>
>
>
> >---
> > drivers/net/bonding/bond_main.c | 15 ++++++++++-----
> > 1 file changed, 10 insertions(+), 5 deletions(-)
> >
> >diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> >index 062fa7e3af4c..407f4095a37a 100644
> >--- a/drivers/net/bonding/bond_main.c
> >+++ b/drivers/net/bonding/bond_main.c
> >@@ -3122,13 +3122,18 @@ static int bond_slave_netdev_event(unsigned long event,
> >       case NETDEV_CHANGE:
> >               /* For 802.3ad mode only:
> >                * Getting invalid Speed/Duplex values here will put slave
> >-               * in weird state. So mark it as link-fail for the time
> >-               * being and let link-monitoring (miimon) set it right when
> >-               * correct speeds/duplex are available.
> >+               * in weird state. Mark it as link-fail if the link was
> >+               * previously up or link-down if it hasn't yet come up, and
> >+               * let link-monitoring (miimon) set it right when correct
> >+               * speeds/duplex are available.
> >                */
> >               if (bond_update_speed_duplex(slave) &&
> >-                  BOND_MODE(bond) == BOND_MODE_8023AD)
> >-                      slave->link = BOND_LINK_FAIL;
> >+                  BOND_MODE(bond) == BOND_MODE_8023AD) {
> >+                      if (slave->last_link_up)
> >+                              slave->link = BOND_LINK_FAIL;
> >+                      else
> >+                              slave->link = BOND_LINK_DOWN;
> >+              }
> >
> >               if (BOND_MODE(bond) == BOND_MODE_8023AD)
> >                       bond_3ad_adapter_speed_duplex_changed(slave);
> >--
> >2.20.1
> >