netdev - Re: [RFC PATCH] core: Add ioctls to control device unicast hw addresses

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Message-ID: <BECD8E8A1B550B48A1BF97C13991F60E2D2E1A@avmb2.qlogic.org>
Date:	Wed, 27 Feb 2013 05:42:21 +0000
From:	Jitendra Kalsaria <jitendra.kalsaria@...gic.com>
To:	John Fastabend <john.r.fastabend@...el.com>,
	"vyasevic@...hat.com" <vyasevic@...hat.com>
CC:	John Fastabend <john.fastabend@...il.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH] core: Add ioctls to control device unicast hw
 addresses



On 2/26/13 9:01 PM, "John Fastabend" <john.r.fastabend@...el.com> wrote:

>On 2/26/2013 6:27 PM, Vlad Yasevich wrote:
>> On 02/26/2013 09:07 PM, John Fastabend wrote:
>>> On Tue, Feb 26, 2013 at 05:15:03PM -0500, David Miller wrote:
>>>> From: John Fastabend <john.r.fastabend@...el.com>
>>>> Date: Tue, 26 Feb 2013 13:58:39 -0800
>>>>
>>>>> [...]
>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> [RFC PATCH] rtnetlink: Add support for adding/removing additional
>>>>>>>>hw
>>>>>>>> addresses.
>>>>>>>>
>>>>>>>> Add an ability to add and remove HW addresses to the device
>>>>>>>> unicast and multicast address lists.  Right now, we only have
>>>>>>>> an ioctl() to manage the multicast addresses and there is no
>>>>>>>> way the manage the unicast list.
>>>>>>>>
>>>>>>>> Signed-off-by: Vlad Yasevich <vyasevic@...hat.com>
>>>>>>>
>>>>>>> This is a step in the right direction, and you're right that there
>>>>>>>is
>>>>>>> a difficulty in detecting whether support exists or not.
>>>>>>>
>>>>>>> I am so surprised that we've have ->set_rx_mode() support for
>>>>>>> multiple
>>>>>>> unicast MAC addresses in so many drivers all this time, yet no way
>>>>>>> outside of FDB to make use of it at all.
>>>>>>
>>>>>> And even that is not always available.  In most drivers it requires
>>>>>> module parameters or other explicit configuration steps.  Meanwhile
>>>>>> set_rx_mode() doesn't seem to depend on any of those and just does
>>>>>>the
>>>>>> right thing.
>>>>>>
>>>>>> For what I was trying to do ioctl() was a really easy way out for
>>>>>>both
>>>>>> kernel and user space implementation, so I gave is shot.
>>>>>>
>>>>>> -vlad
>>>>>>
>>>>>
>>>>> Don't we already support this with
>>>>
>>>> The whole point is that these multiple-unicast-address configuration
>>>> facilities are inaccessible without FDB, and there is no reason
>>>> whatsoever for that.
>>>
>>> Yes I see now sorry I was behind the thread.
>>>
>>> We could just use the fdb hooks and add a dflt routine to handle the
>>> case where the netdev doesn't provide a specific ndo_op for us. This
>>> boils down to calling set_rx_mode anyways through this call chain,
>>>
>>>     ndo_fdb_add
>>>     dev_uc_add_excl
>>>         __dev_set_rx_mode
>>>             ndo_set_rx_mode
>>>
>>> As long as folks don't think this is too much of an abuse of the fdb
>>> hooks. Here's an example I only compile tested this so take it as
>>> an example only. It probably needs some cleanups and the dump routine
>>> needs some thought not sure you want to dump all MACs always.
>>
>> I thought about doing, but this becomes broken on the drivers that
>> support ndo_fdb_* functions.  Those drivers mainly require additional
>> configuration that is not necessary for dev_uc_add_excl() to work.
>>
>> For example, ixgbe and melanox requires VF to be on, qlogic needs a
>> module parameter, macvlan has to be in passthrough.  However,
>> ndo_set_rx_mode() in most cases doesn't care about those settings and
>> just works.
>>
>
>The ixgbe piece could just use the dflt routines I put below. The
>SR-IOV check is only there because when I wrote that I didn't consider
>adding additional addresses without VFs. This was a poor example.
>
>The mlx4 card is checking if the device is a slave or master before
>adding/removing addresses. My guess is this is the same type of check
>as ixgbe and would work just fine without it.
>
>I'm not sure macvlan supports unicast hw addresses either way but
>there is no reason we couldn't. The idea was we would come back and
>write it later. Like many things I haven't got to it yet.
>
>Calling set_rx_mode() on qlcnic doesn't look to help you at all either
>it appears to ignore the uc_list either way.

Even though we use module parameter for fdb but it would be good it have
set_rx_mode().
We don't ignore uc_list but it never called set_rx_mode() when I use
dev_uc_add_excl when added support and thought that's how it might
designed.
  
-Jiten
>
>is that all the callers? looks like it.
>
>> So fdb will not always work even if the driver has proper support for
>> IFF_UNICAST_FLT.
>>
>
>The fdb could work if we fix the drivers it seems to me most
>the cases where it wouldn't work are just lack of foresight or the code
>isn't there yet. I think it might be valuable to have a single API for
>both use cases.
>
>.John
>
>> -vlad
>>
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