Don't do anything if there are no netlink interfaces

If a pci device allocated to a container by SR-IOV device plugin is of
vfio type then it doesn't have a netlink representation, so moving the
interface into container namespace is useless and actually breaks the
CNI plugin.

We could perhaps go with a separate noop CNI plugin to do the same but
there are plans to, in the future, allocate IPAM info for the device
and expose it by one means or another (it could be a fake veth pair to
carry the information: see issue k8snetworkplumbingwg#37; or some other mechanism).

Fixes k8snetworkplumbingwg#63

pkg/utils/utils.go

@@ -15,6 +15,8 @@ var (
 	NetDirectory = "/sys/class/net"
 	// SysBusPci is sysfs pci device directory
 	SysBusPci = "/sys/bus/pci/devices"
+	// UserspaceDrivers is a list of driver names that don't have netlink representation for their devices
+	UserspaceDrivers = []string{"vfio-pci", "uio_pci_generic"}
 )
 
 // GetSriovNumVfs takes in a PF name(ifName) as string and returns number of VF configured as int
@@ -138,20 +140,47 @@ func GetSharedPF(ifName string) (string, error) {
 	return pfName, fmt.Errorf("Shared PF not found")
 }
 
+// ShouldHaveNetlink determines whether VF is expected to have a netlink interface
+func ShouldHaveNetlink(pfName string, vfID int) (bool, error) {
+	driverLink := filepath.Join(NetDirectory, pfName, "device", fmt.Sprintf("virtfn%d", vfID), "driver")
+	driverPath, err := filepath.EvalSymlinks(driverLink)
+	if err != nil {
+		return false, err
+	}
+	driverStat, err := os.Stat(driverPath)
+	if err != nil {
+		return false, err
+	}
+	driverName := driverStat.Name()
+	for _, drv := range UserspaceDrivers {
+		if driverName == drv {
+			return false, nil
+		}
+	}
+	return true, nil
+}
+
 // GetVFLinkNames returns VF's network interface name given it's PF name as string and VF id as int
 func GetVFLinkNames(pfName string, vfID int) ([]string, error) {
-	var names []string
+	var names = make([]string, 0)
+
 	vfDir := filepath.Join(NetDirectory, pfName, "device", fmt.Sprintf("virtfn%d", vfID), "net")
 	if _, err := os.Lstat(vfDir); err != nil {
-		return nil, err
+		netlinkExpected, shouldHaveNetlinkErr := ShouldHaveNetlink(pfName, vfID)
+		if shouldHaveNetlinkErr != nil {
+			return nil, shouldHaveNetlinkErr
+		}
+		if netlinkExpected {
+			return nil, err
+		}
+		return names, nil
 	}
 
 	fInfos, err := ioutil.ReadDir(vfDir)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read the virtfn%d dir of the device %q: %v", vfID, pfName, err)
 	}
 
-	names = make([]string, 0)
 	for _, f := range fInfos {
 		names = append(names, f.Name())
 	}

sriov/main.go

@@ -11,6 +11,7 @@ import (
 	"github.com/containernetworking/cni/pkg/types"
 	"github.com/containernetworking/cni/pkg/version"
 	"github.com/intel/sriov-cni/pkg/config"
+	"github.com/intel/sriov-cni/pkg/utils"
 	"github.com/vishvananda/netlink"
 )
 
@@ -78,9 +79,14 @@ func cmdAdd(args *skel.CmdArgs) error {
 		return fmt.Errorf("VF information are not available to invoke setupVF()")
 	}
 
+	vfLinks, err := utils.GetVFLinkNames(n.Master, n.DeviceInfo.Vfid)
+	if err != nil {
+		return err
+	}
+
 	// skip the IPAM allocation for the DPDK and L2 mode
 	var result *types.Result
-	if n.DPDKMode || n.L2Mode {
+	if n.DPDKMode || n.L2Mode || len(vfLinks) == 0 {
 		return result.Print()
 	}
 

sriov/sriov.go

@@ -114,6 +114,10 @@ func setupVF(conf *sriovtypes.NetConf, podifName string, cid string, netns ns.Ne
 		return err
 	}
 
+	if len(vfLinks) == 0 {
+		return nil
+	}
+
 	if conf.Vlan != 0 {
 		if err = netlink.LinkSetVfVlan(m, conf.DeviceInfo.Vfid, conf.Vlan); err != nil {
 			return fmt.Errorf("failed to set vf %d vlan: %v", conf.DeviceInfo.Vfid, err)
@@ -201,6 +205,14 @@ func releaseVF(conf *sriovtypes.NetConf, podifName string, cid string, netns ns.
 		return nil
 	}
 
+	netlinkExpected, err := utils.ShouldHaveNetlink(conf.Master, conf.DeviceInfo.Vfid)
+	if err != nil {
+		return fmt.Errorf("failed to determine if interface should have netlink device: %v", err)
+	}
+	if !netlinkExpected {
+		return nil
+	}
+
 	initns, err := ns.GetCurrentNS()
 	if err != nil {
 		return fmt.Errorf("failed to get init netns: %v", err)