netdev - Re: [net-next-2.6 PATCH 0/6 v4] macvlan: MAC Address filtering support for passthru mode

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Message-ID: <4EC68EBB.3080303@intel.com>
Date:	Fri, 18 Nov 2011 08:58:35 -0800
From:	Greg Rose <gregory.v.rose@...el.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	Roopa Prabhu <roprabhu@...co.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"chrisw@...hat.com" <chrisw@...hat.com>,
	"sri@...ibm.com" <sri@...ibm.com>,
	"dragos.tatulea@...il.com" <dragos.tatulea@...il.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"arnd@...db.de" <arnd@...db.de>, "mst@...hat.com" <mst@...hat.com>,
	"mchan@...adcom.com" <mchan@...adcom.com>,
	"dwang2@...co.com" <dwang2@...co.com>,
	"shemminger@...tta.com" <shemminger@...tta.com>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"benve@...co.com" <benve@...co.com>
Subject: Re: [net-next-2.6 PATCH 0/6 v4] macvlan: MAC Address filtering support
 for passthru mode


On 11/17/2011 4:44 PM, Ben Hutchings wrote:
> On Thu, 2011-11-17 at 16:32 -0800, Greg Rose wrote:
>> On 11/17/2011 4:15 PM, Ben Hutchings wrote:
>>> Sorry to come to this rather late.
>>>
>>> On Tue, 2011-11-08 at 23:55 -0800, Roopa Prabhu wrote:
>>> [...]
>>>> v2 ->   v3
>>>> - Moved set and get filter ops from rtnl_link_ops to netdev_ops
>>>> - Support for SRIOV VFs.
>>>>           [Note: The get filters msg (in the way current get rtnetlink handles
>>>>           it) might get too big for SRIOV vfs. This patch follows existing sriov
>>>>           vf get code and tries to accomodate filters for all VF's in a PF.
>>>>           And for the SRIOV case I have only tested the fact that the VF
>>>>           arguments are getting delivered to rtnetlink correctly. The code
>>>>           follows existing sriov vf handling code so rest of it should work fine]
>>> [...]
>>>
>>> This is already broken for large numbers of VFs, and increasing the
>>> amount of information per VF is going to make the situation worse.  I am
>>> no netlink expert but I think that the current approach of bundling all
>>> information about an interface in a single message may not be
>>> sustainable.
>>>
>>> Also, I'm unclear on why this interface is to be used to set filtering
>>> for the (PF) net device as well as for related VFs.  Doesn't that
>>> duplicate the functionality of ndo_set_rx_mode and
>>> ndo_vlan_rx_{add,kill}_vid?
>>
>> Functionally yes but contextually no.  This allows the PF driver to know
>> that it is setting these filters in the context of the existence of VFs,
>> allowing it to take appropriate action.  The other two functions may be
>> called without the presence of SR-IOV enablement and the existence of VFs.
>>
>> Anyway, that's why I asked Roopa to add that capability.
>
> I don't follow.  The PF driver already knows whether it has enabled VFs.
>
> How do filters set this way interact with filters set through the
> existing operations?  Should they override promiscuous mode?  None of
> this has been specified.

Promiscuous mode is exactly the issue this feature is intended for.  I'm 
not familiar with the solarflare device but Intel HW promiscuous mode is 
only promiscuous on the physical port, not on the VEB.  So a packet sent 
from a VF will not be captured by the PF across the VEB unless the MAC 
and VLAN filters have been programmed into the HW.  So you may not need 
the feature for your devices but it is required for Intel devices.  And 
it's a fairly simple request, just allow -1 to indicate that the target 
of the filter requests is for the PF itself.  Using the already existing 
set_rx_mode function wont' work because the PF driver will look at it 
and figure it's in promiscuous mode anyway, so it won't set the filters 
into the HW.  At least that is how it is in the case of our HW and 
driver.  Again, the behavior of your HW and driver is unknown to me and 
thus you may not require this feature.

- Greg
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