Re: Vlan EVENT patch

On Wed, Jun 11, 2008 at 12:33 AM, Pyun YongHyeon <pyunyh_at_gmail.com> wrote:
> On Tue, Jun 10, 2008 at 09:51:53AM -0700, Jack Vogel wrote:
>  > This is a small patch that Sam came up with for me, it will allow
>  > drivers to know
>  > when a vlan attaches.
>  >
>  > It is transparent to any code that doesn't want to change, but this
>  > will allow my
>  > drivers to finally utilize the vlan hardware filter (something Linux has had for
>  > ever but we lacked).
>  >
>
> Just curious, is there any rule how to use that new capability?
> Because drivers will receive events whenever VLAN tags are
> added/removed they would know how to act for these events. If
> promiscuous mode is on for interface, driver should not filter any
> VLAN tagged frames, right?
> If users want to disable VLAN hardware filtering feature what is
> best way to perform this? Introducing a new flag like
> IFCAP_VLAN_HWFILT or add a new sysctl that control this feature?
> I guess VIA Rhine III also have VLAN hardware filtering capability
> so it would be even better if we have a way to share common part.

All the patch does is have the vlan driver generate events when it attaches
or detaches from a NIC, there are no rules, however I can tell you what
I'm coding into this in the Intel drivers.

The way it works is the driver registers a callback for each event, I will
call that [igb,em,ixgbe]_register_vlan(), and unregister obviously.

Right now, the drivers just generically enable VLAN capability because
there is never a trigger to know IF and WHEN you need to do so, but
with this change the VLAN capability will only get turned on by the
registration routine.

Most significantly, now when the pseudo device it gives the driver
the VLAN tag, this will mean the driver will be able from the start
to use the VFTA, the hardware filter, for each vlan attach the driver
will add the ID into this table.

The unregister event will turn the table entry off, and if this is the
last VLAN being detached it will then disable the features.

Oh yes, these routines will also take care of the size change of
the frame due to the tag. I already have the changes in place in
the igb drive, and they are working great.

I do not understand why you think you need a flag to disable this,
yes it could be done, but why? If you need to do some sort of
debugging won't a system not using vlans and in promiscuous
mode do just fine?

It just seems to violate the whole reason for doing vlans in the
first place, however perhaps I am missing something? I do not
believe the Linux driver has some way to disable use of the table
but I'll double check on that.

Remember, this change requires NO driver changes unless they
wish to take advantage of the ability.

Cheers,

Jack