[libvirt] [PATCH 06/12] virInterface: Expose link state & speed

[Michal Privoznik]

On 30.05.2014 14:35, Daniel P. Berrange wrote:
> On Fri, May 30, 2014 at 01:41:08PM +0200, Michal Privoznik wrote:
>> On 30.05.2014 10:56, Daniel P. Berrange wrote:
>>> On Thu, May 29, 2014 at 10:32:40AM +0200, Michal Privoznik wrote:
>>>> Currently it is not possible to determine the speed of an interface
>>>> and whether a link is actually detected from the API. Orchestrating
>>>> platforms want to be able to determine when the link has failed and
>>>> where multiple speeds may be available which one the interface is
>>>> actually connected at. This commit introduces an extension to our
>>>> interface XML (without implementation to interface driver backends):
>>>>
>>>>    <interface type='ethernet' name='eth0'>
>>>>      <start mode='none'/>
>>>>      <mac address='aa:bb:cc:dd:ee:ff'/>
>>>>      <link speed='1000' state='up'/>
>>>>      <mtu size='1492'/>
>>>>      ...
>>>>    </interface>
>>>>
>>>> Where @speed is negotiated link speed in Mbits per second, and state
>>>> is the current NIC state (can be one of the following:  "unknown",
>>>> "notpresent", "down", "lowerlayerdown","testing", "dormant", "up").
>>>
>>> This is fine for the the <interface> objects, but it is limited
>>> in usefulness for SRIOV use cases. The <interface> objects only
>>> exist for interfaces which are configured for the host. With
>>> SRIOV passthrough some of the interfaces we're interested in
>>> are not going to be configured - they're just bare devices
>>> waiting to be given to a guest.
>>
>> I hear what you're saying, but unless a PCI device is given interface name I
>> am afraid we can't do anything. For instance, if you have a NIC but detach
>> it from the driver (echo ${PCI_ADDR} >
>> /sys/bus/pci/drivers/<driver>/unbind), kernel still sees the PCI device
>> (it's shown in lspci output for instance), but it's not configured anymore -
>> kernel doesn't know device link state, hence it's not aware if NIC's link
>> speed, etc. So tools like ethtool, ip, ifconfing won't show the device.
>
> IIUC, We have three classes of device
>
>   1 Devices not bound - no NIC visible in the host OS
>
>   2 Devices bound but not configured. NIC visible in host OS, but no
>     /etc/sysconfig/networking/ifcfg-XXX file
>
>   3 Devices bound and configured. NIC visible in host OS, and has a
>     /etc/sysconfig/networking/ifcfg-XXX file
>
> The <interface> configs only let you deal with NIC devices in class 3.
>
> The <nodedev> XML / APIs let you see NIC devices in class 2 + 3.
>

Right. The netcf world. Okay, makes sense now. In udev we have 2nd and 
3rd classes merged into one.

Michal