Use temporary name for netdevice when moving in/out of NS

Today, it is not possible to use host-device CNI to move a
host device to container namespace if a device already exists
in that namespace.

e.g when a delegate plugin (such as multus) is used to provide
multiple networks to a container, CNI Add call will fail if
the targeted host device name already exists in container network
namespace.

to overcome this, we use a temporary name for the interface before
moving it in/out of container network namespace.

Signed-off-by: adrianc <adrianc@nvidia.com>

plugins/main/host-device/host-device_test.go

@@ -1149,6 +1149,114 @@ var _ = Describe("base functionality", func() {
 				return nil
 			})
 		})
+
+		It(fmt.Sprintf("Test CmdAdd/Del when additioinal interface alreay exists in container ns with same name. %s config", ver), func() {
+			var (
+				origLink      netlink.Link
+				containerLink netlink.Link
+			)
+
+			hostIfname := "eth0"
+			containerAdditionalIfname := "eth0"
+
+			// prepare host device in original namespace
+			_ = originalNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				err := netlink.LinkAdd(&netlink.Dummy{
+					LinkAttrs: netlink.LinkAttrs{
+						Name: hostIfname,
+					},
+				})
+				Expect(err).NotTo(HaveOccurred())
+				origLink, err = netlink.LinkByName(hostIfname)
+				Expect(err).NotTo(HaveOccurred())
+				err = netlink.LinkSetUp(origLink)
+				Expect(err).NotTo(HaveOccurred())
+				return nil
+			})
+
+			// prepare device in container namespace with same name as host device
+			_ = targetNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				err := netlink.LinkAdd(&netlink.Dummy{
+					LinkAttrs: netlink.LinkAttrs{
+						Name: containerAdditionalIfname,
+					},
+				})
+				Expect(err).NotTo(HaveOccurred())
+				containerLink, err = netlink.LinkByName(containerAdditionalIfname)
+				Expect(err).NotTo(HaveOccurred())
+				err = netlink.LinkSetUp(containerLink)
+				Expect(err).NotTo(HaveOccurred())
+				return nil
+			})
+
+			// call CmdAdd
+			cniName := "net1"
+			conf := fmt.Sprintf(`{
+				"cniVersion": "%s",
+				"name": "cni-plugin-host-device-test",
+				"type": "host-device",
+				"device": %q
+			}`, ver, hostIfname)
+			args := &skel.CmdArgs{
+				ContainerID: "dummy",
+				Netns:       targetNS.Path(),
+				IfName:      cniName,
+				StdinData:   []byte(conf),
+			}
+			var resI types.Result
+			err := originalNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				var err error
+				resI, _, err = testutils.CmdAddWithArgs(args, func() error { return cmdAdd(args) })
+				return err
+			})
+			Expect(err).NotTo(HaveOccurred())
+
+			// check that the result was sane
+			t := newTesterByVersion(ver)
+			t.expectInterfaces(resI, cniName, origLink.Attrs().HardwareAddr.String(), targetNS.Path())
+
+			// assert that host device is now in the target namespace and is up
+			_ = targetNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				link, err := netlink.LinkByName(cniName)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(link.Attrs().HardwareAddr).To(Equal(origLink.Attrs().HardwareAddr))
+				Expect(link.Attrs().Flags & net.FlagUp).To(Equal(net.FlagUp))
+				return nil
+			})
+
+			// call CmdDel, expect it to succeed
+			_ = originalNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				err = testutils.CmdDelWithArgs(args, func() error {
+					return cmdDel(args)
+				})
+				Expect(err).ToNot(HaveOccurred())
+				return nil
+			})
+
+			// assert container interface "eth0" still exists in target namespace and is up
+			err = targetNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				link, err := netlink.LinkByName(containerAdditionalIfname)
+				Expect(err).NotTo(HaveOccurred())
+				Expect(link.Attrs().HardwareAddr).To(Equal(containerLink.Attrs().HardwareAddr))
+				Expect(link.Attrs().Flags & net.FlagUp).To(Equal(net.FlagUp))
+				return nil
+			})
+			Expect(err).NotTo(HaveOccurred())
+
+			// assert that host device is now back in the original namespace
+			_ = originalNS.Do(func(ns.NetNS) error {
+				defer GinkgoRecover()
+				_, err := netlink.LinkByName(hostIfname)
+				Expect(err).NotTo(HaveOccurred())
+				return nil
+			})
+		})
 	}
 })