host-device: set link up after moving host device to pod namespace

[zshi-redhat]

Currently host-device plugin only moves the host-device to pod namespace.

But sometimes, when moving the host device to pod, user wants to use that device as an interface for running real network traffic, it would be good to set the device link up in the pod namespace and perhaps even further to add the ability for host-device to run ipam configuration.

one possible use case: pod running in a virtual machine wants to use one of the virtual interfaces in the VM(in this case, the virtual interfaces can be seen as host-device for the pod).

[dpward]

While IPAM can now be used with the host-device plugin, this doesn't help if the interface is being used at layer 2.

This issue seems unique to the host-device plugin. The interface-creating plugins will bring the new interface up automatically. When an interface gets moved into another namespace, though, the kernel automatically brings it down. (The plugin also ensures it is down after it is moved, so that it can be renamed.)

[zshi-redhat]

While IPAM can now be used with the host-device plugin, this doesn't help if the interface is being used at layer 2.

We probably want to have a similar code piece like sriov-cni to explicitly set the interface link up.

[jayunit100]

generally curious about what is meant by "use that device as an interface for running real network traffic" :)