Add network metrics

[ZeroMagic]

When we use containerd to run our applications, we can not collect the network metrics about containers. Can we add the network metrics into metrics.proto?

type NetworkInterface struct {
	// Name is the name of the network interface.
	Name string

	RxBytes uint64
	RxPackets uint64
	RxErrors uint64
	RxDropped uint64
	TxBytes uint64
	TxPackets uint64
	TxErrors uint64
	TxDropped uint64
}

ping @crosbymichael

[crosbymichael]

Where are these metrics going to come from?

[ZeroMagic]

Where are these metrics going to come from?

@crosbymichael
Currently KataContainers collect the metrics from libcontainer Stats() API.

The libcontainer Stats() API has collected the network metrics. However KataContainers do not transfer the network metrics now. I will propose a similar issue in KataContainers community.

Then the network metrics will come from shimV2 Stats() API.

[crosbymichael]

The reason why I kept network stats out of this pkg is because a lot of the network stats come from /sys and not cgroups

[ZeroMagic]

I got it. Where do you think I should add network stats?
Sincerely looking forward to some guidance.

[thaJeztah]

@ZeroMagic with #81 merged; is this one ready to close?