> On 21 Mar 2019, at 14:57, Michael S. Tsirkin <m...@redhat.com> wrote:
> On Thu, Mar 21, 2019 at 02:47:50PM +0200, Liran Alon wrote:
>>> 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.
>> -Liran
> OK. Now what happens if master is moved to another namespace? Do we need
> to move the slaves too?

No. Why would we move the slaves? The whole point is to make most customer 
ignore the net-failover slaves and remain them “hidden” in their dedicated 
We won’t prevent customer from explicitly moving the net-failover slaves out of 
this netns, but we will not move them out of there automatically.

> Also siwei's patch is then kind of extraneous right?
> Attempts to rename a slave will now fail as it's in a namespace…

I’m not sure actually. Isn't udev/systemd netns-aware?
I would expect it to be able to provide names also to netdevs in netns 
different than default netns.
If that’s the case, Si-Wei patch to be able to rename a net-failover slave when 
it is already open is still required. As the race-condition still exists.


>>> -- 
>>> MST

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