When prevResults are not returned to loopback plugin, create results to return based on

the lo interface and IP address assigned inside container.

Signed-off-by: Michael Cambria <mcambria@redhat.com>

plugins/main/loopback/loopback.go

@@ -55,6 +55,8 @@ func cmdAdd(args *skel.CmdArgs) error {
 		return err
 	}
 
+	var v4Addr, v6Addr *net.IPNet
+
 	args.IfName = "lo" // ignore config, this only works for loopback
 	err = ns.WithNetNSPath(args.Netns, func(_ ns.NetNS) error {
 		link, err := netlink.LinkByName(args.IfName)
@@ -66,6 +68,33 @@ func cmdAdd(args *skel.CmdArgs) error {
 		if err != nil {
 			return err // not tested
 		}
+		v4Addrs, err := netlink.AddrList(link, netlink.FAMILY_V4)
+		if err != nil {
+			return err // not tested
+		}
+		if len(v4Addrs) != 0 {
+			v4Addr = v4Addrs[0].IPNet
+			// sanity check that this is a loopback address
+			for _, addr := range v4Addrs {
+				if !addr.IP.IsLoopback() {
+					return fmt.Errorf("loopback interface found with non-loopback address %q", addr.IP)
+				}
+			}
+		}
+
+		v6Addrs, err := netlink.AddrList(link, netlink.FAMILY_V6)
+		if err != nil {
+			return err // not tested
+		}
+		if len(v6Addrs) != 0 {
+			v6Addr = v6Addrs[0].IPNet
+			// sanity check that this is a loopback address
+			for _, addr := range v4Addrs {
+				if !addr.IP.IsLoopback() {
+					return fmt.Errorf("loopback interface found with non-loopback address %q", addr.IP)
+				}
+			}
+		}
 
 		return nil
 	})
@@ -79,7 +108,26 @@ func cmdAdd(args *skel.CmdArgs) error {
 		// loopback should pass it transparently
 		result = conf.PrevResult
 	} else {
-		result = &current.Result{}
+		loopbackInterface := &current.Interface{Name: args.IfName, Mac: "00:00:00:00:00:00", Sandbox: args.Netns}
+		r := &current.Result{CNIVersion: conf.CNIVersion, Interfaces: []*current.Interface{loopbackInterface}}
+
+		if v4Addr != nil {
+			r.IPs = append(r.IPs, &current.IPConfig{
+				Version:   "4",
+				Interface: current.Int(0),
+				Address:   *v4Addr,
+			})
+		}
+
+		if v6Addr != nil {
+			r.IPs = append(r.IPs, &current.IPConfig{
+				Version:   "6",
+				Interface: current.Int(0),
+				Address:   *v6Addr,
+			})
+		}
+
+		result = r
 	}
 
 	return types.PrintResult(result, conf.CNIVersion)

plugins/main/loopback/loopback_test.go

@@ -49,7 +49,7 @@ var _ = Describe("Loopback", func() {
 			fmt.Sprintf("CNI_ARGS=%s", "none"),
 			fmt.Sprintf("CNI_PATH=%s", "/some/test/path"),
 		}
-		command.Stdin = strings.NewReader(`{ "cniVersion": "0.1.0" }`)
+		command.Stdin = strings.NewReader(`{ "name": "loopback-test", "cniVersion": "0.1.0" }`)
 	})
 
 	AfterEach(func() {
@@ -59,8 +59,6 @@ var _ = Describe("Loopback", func() {
 
 	Context("when given a network namespace", func() {
 		It("sets the lo device to UP", func() {
-
-			Skip("TODO: add network name")
 			command.Env = append(environ, fmt.Sprintf("CNI_COMMAND=%s", "ADD"))
 
 			session, err := gexec.Start(command, GinkgoWriter, GinkgoWriter)
@@ -81,8 +79,6 @@ var _ = Describe("Loopback", func() {
 		})
 
 		It("sets the lo device to DOWN", func() {
-
-			Skip("TODO: add network name")
 			command.Env = append(environ, fmt.Sprintf("CNI_COMMAND=%s", "DEL"))
 
 			session, err := gexec.Start(command, GinkgoWriter, GinkgoWriter)