remove dependency on /sbin/ip binary

[AkihiroSuda]

[Zyqsempai]

@AkihiroSuda Is this still actual?

[AkihiroSuda]

yes, we should still do this ideally (but tricky because of nsenter stuff)

[Zyqsempai]

@AkihiroSuda What do you think about using those packages: For netlink operations we can use https://godoc.org/github.com/vishvananda/netlink and for nsenter https://godoc.org/github.com/kata-containers/runtime/virtcontainers/pkg/nsenter

By the end we will get something like this

funcToRun := func() error {
	err := netlink.LinkSetUp(tap)
	if err != nil {
		return err
	}

	return nil
}

err = nsenter.NsEnter(nsList, funcToRun)

[AkihiroSuda]

You can't nsenter userns in Go.

[AkihiroSuda]

So, we should have IPC across the parent and the child process to remove nsenter dependency.