vfio: Change the way the driver is fetched

Instead of using ethtool for getting the driver for network
devices, use sysfs instead. This is because in case of virtio
devices, ethtool returns virtio-net instead of virtio-pci for
virtio network devices. We need to bind/unbind from virtio-pci
driver in case of virtio-net devices.

Fixes #612

Signed-off-by: Archana Shinde <archana.m.shinde@intel.com>

virtcontainers/physical_endpoint.go

@@ -8,6 +8,7 @@ package virtcontainers
 import (
 	"fmt"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strings"
 
@@ -143,12 +144,15 @@ func createPhysicalEndpoint(netInfo NetworkInfo) (*PhysicalEndpoint, error) {
 		return nil, err
 	}
 
-	// Get Driver
-	driver, err := ethHandle.DriverName(netInfo.Iface.Name)
+	// Get driver by following symlink /sys/bus/pci/devices/$bdf/driver
+	driverPath := filepath.Join(sysPCIDevicesPath, bdf, "driver")
+	link, err := os.Readlink(driverPath)
 	if err != nil {
 		return nil, err
 	}
 
+	driver := filepath.Base(link)
+
 	// Get vendor and device id from pci space (sys/bus/pci/devices/$bdf)
 
 	ifaceDevicePath := filepath.Join(sysPCIDevicesPath, bdf, "device")