linux-kernel - Re: [Intel-wired-lan] [RFC PATCH net] e1000e: keep vlan interfaces functional after rxvlan off

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Date:	Wed, 1 Jun 2016 15:27:24 -0400
From:	Jarod Wilson <jarod@...hat.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Netdev <netdev@...r.kernel.org>,
	intel-wired-lan <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [Intel-wired-lan] [RFC PATCH net] e1000e: keep vlan interfaces
 functional after rxvlan off

On Wed, Jun 01, 2016 at 07:31:53AM -0700, Alexander Duyck wrote:
> On Tue, May 17, 2016 at 12:03 PM, Jarod Wilson <jarod@...hat.com> wrote:
> > I've got a bug report about an e1000e interface, where a vlan interface is
> > set up on top of it:
> >
> > $ ip link add link ens1f0 name ens1f0.99 type vlan id 99
> > $ ip link set ens1f0 up
> > $ ip link set ens1f0.99 up
> > $ ip addr add 192.168.99.92 dev ens1f0.99
> >
> > At this point, I can ping another host on vlan 99, ip 192.168.99.91.
> > However, if I do the following:
> >
> > $ ethtool -K ens1f0 rxvlan off
> >
> > Then no traffic passes on ens1f0.99. It comes back if I toggle rxvlan on
> > again. I'm not sure if this is actually intended behavior, or if there's a
> > lack of software vlan stripping fallback, or what, but things continue to
> > work if I simply don't call e1000e_vlan_strip_disable() if there are
> > active vlans (plagiarizing a function from the e1000 driver here) on the
> > interface.
> >
> > Also slipped a related-ish fix to the kerneldoc text for
> > e1000e_vlan_strip_disable here...
> >
> > CC: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> > CC: intel-wired-lan@...ts.osuosl.org
> > CC: netdev@...r.kernel.org
> > Signed-off-by: Jarod Wilson <jarod@...hat.com>
> > ---
> >  drivers/net/ethernet/intel/e1000e/netdev.c | 15 +++++++++++++--
> >  1 file changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> > index 75e6089..73f7452 100644
> > --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> > +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> > @@ -154,6 +154,16 @@ void __ew32(struct e1000_hw *hw, unsigned long reg, u32 val)
> >         writel(val, hw->hw_addr + reg);
> >  }
> >
> > +static bool e1000e_vlan_used(struct e1000_adapter *adapter)
> > +{
> > +       u16 vid;
> > +
> > +       for_each_set_bit(vid, adapter->active_vlans, VLAN_N_VID)
> > +               return true;
> > +
> 
> I'm pretty sure this is always going to return true if 8021q is loaded
> because VLAN 0 is always added to the device even if no other VLANs
> are in use.

Ah, hadn't considered that, I just plucked it straight from e1000.

> > +       return false;
> > +}
> > +
> >  /**
> >   * e1000_regdump - register printout routine
> >   * @hw: pointer to the HW structure
> > @@ -2789,7 +2799,7 @@ static void e1000e_vlan_filter_enable(struct e1000_adapter *adapter)
> >  }
> >
> >  /**
> > - * e1000e_vlan_strip_enable - helper to disable HW VLAN stripping
> > + * e1000e_vlan_strip_disable - helper to disable HW VLAN stripping
> >   * @adapter: board private structure to initialize
> >   **/
> >  static void e1000e_vlan_strip_disable(struct e1000_adapter *adapter)
> > @@ -3443,7 +3453,8 @@ static void e1000e_set_rx_mode(struct net_device *netdev)
> >
> >         ew32(RCTL, rctl);
> >
> > -       if (netdev->features & NETIF_F_HW_VLAN_CTAG_RX)
> > +       if (netdev->features & NETIF_F_HW_VLAN_CTAG_RX ||
> > +           e1000e_vlan_used(adapter))
> >                 e1000e_vlan_strip_enable(adapter);
> >         else
> >                 e1000e_vlan_strip_disable(adapter);
> 
> So if the VLAN tag stripping is disabled what happens that is causing
> the VLAN test to fail?  It sounds like this might be working around a
> kernel bug where a VLAN created on a device that supports hardware tag
> stripping only supports hardware tag stripping.  Maybe a better fix
> would be to add a fall back so if the VLAN tag is in the frame instead
> of stripped it still makes it to the correct spot.

That's the main reason I labeled it as an RFC -- I wasn't sure exactly how
things were intended to work when the hardware stripping was disabled. It
seems quite plausible to me that this patch simply papers over the real
bug: lack of a functional software fallback. I'm not particularly up on
the vlan code just yet though, so I'm not yet sure where to poke next.
Suggestions welcomed. :)

-- 
Jarod Wilson
jarod@...hat.com