> On 21 Mar 2019, at 14:37, Michael S. Tsirkin <m...@redhat.com> wrote:
> On Thu, Mar 21, 2019 at 12:07:57PM +0200, Liran Alon wrote:
>>>>>> 2) It brings non-intuitive customer experience. For example, a customer 
>>>>>> may attempt to analyse connectivity issue by checking the connectivity
>>>>>> on a net-failover slave (e.g. the VF) but will see no connectivity when 
>>>>>> in-fact checking the connectivity on the net-failover master netdev 
>>>>>> shows correct connectivity.
>>>>>> The set of changes I vision to fix our issues are:
>>>>>> 1) Hide net-failover slaves in a different netns created and managed by 
>>>>>> the kernel. But that user can enter to it and manage the netdevs there 
>>>>>> if wishes to do so explicitly.
>>>>>> (E.g. Configure the net-failover VF slave in some special way).
>>>>>> 2) Match the virtio-net and the VF based on a PV attribute instead of 
>>>>>> MAC. (Similar to as done in NetVSC). E.g. Provide a virtio-net interface 
>>>>>> to get PCI slot where the matching VF will be hot-plugged by hypervisor.
>>>>>> 3) Have an explicit virtio-net control message to command hypervisor to 
>>>>>> switch data-path from virtio-net to VF and vice-versa. Instead of 
>>>>>> relying on intercepting the PCI master enable-bit
>>>>>> as an indicator on when VF is about to be set up. (Similar to as done in 
>>>>>> NetVSC).
>>>>>> Is there any clear issue we see regarding the above suggestion?
>>>>>> -Liran
>>>>> The issue would be this: how do we avoid conflicting with namespaces
>>>>> created by users?
>>>> This is kinda controversial, but maybe separate netns names into 2 groups: 
>>>> hidden and normal.
>>>> To reference a hidden netns, you need to do it explicitly. 
>>>> Hidden and normal netns names can collide as they will be maintained in 
>>>> different namespaces (Yes I’m overloading the term namespace here…).
>>> Maybe it's an unnamed namespace. Hidden until userspace gives it a name?
>> This is also a good idea that will solve the issue. Yes.
>>>> Does this seems reasonable?
>>>> -Liran
>>> Reasonable I'd say yes, easy to implement probably no. But maybe I
>>> missed a trick or two.
>> BTW, from a practical point of view, I think that even until we figure out a 
>> solution on how to implement this,
>> it was better to create an kernel auto-generated name (e.g. 
>> “kernel_net_failover_slaves")
>> that will break only userspace workloads that by a very rare-chance have a 
>> netns that collides with this then
>> the breakage we have today for the various userspace components.
>> -Liran
> It seems quite easy to supply that as a module parameter. Do we need two
> namespaces though? Won't some userspace still be confused by the two
> slaves sharing the MAC address?

That’s one reasonable option.
Another one is that we will indeed change the mechanism by which we determine a 
VF should be bonded with a virtio-net device.
i.e. Expose a new virtio-net property that specify the PCI slot of the VF to be 
bonded with.

The second seems cleaner but I don’t have a strong opinion on this. Both seem 
reasonable to me and your suggestion is faster to implement from current state 
of things.


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