pkg/ns: introduce error types indicate NS verification

plugins: don't require CNI_NETNS for DEL command

pkg/ns/ns.go

@@ -81,11 +81,23 @@ const (
 	PROCFS_MAGIC = 0x9fa0
 )
 
-func IsNS(nspath string) (isNS bool, msg string, err error) {
+type NSPathNotExistErr struct{ msg string }
+
+func (e NSPathNotExistErr) Error() string { return e.msg }
+
+type NSPathNotNSErr struct{ msg string }
+
+func (e NSPathNotNSErr) Error() string { return e.msg }
+
+func IsNSorErr(nspath string) error {
 	stat := syscall.Statfs_t{}
-	if err = syscall.Statfs(nspath, &stat); err != nil {
-		err = fmt.Errorf("failed to Statfs %s: %v", nspath, err)
-		return
+	if err := syscall.Statfs(nspath, &stat); err != nil {
+		if os.IsNotExist(err) {
+			err = NSPathNotExistErr{msg: fmt.Sprintf("failed to Statfs %q: %v", nspath, err)}
+		} else {
+			err = fmt.Errorf("failed to Statfs %q: %v", nspath, err)
+		}
+		return err
 	}
 
 	switch stat.Type {
@@ -95,33 +107,29 @@ func IsNS(nspath string) (isNS bool, msg string, err error) {
 		validPathContent := "ns/"
 		validName := strings.Contains(nspath, validPathContent)
 		if !validName {
-			msg = fmt.Sprintf("path doesn't contain %q", validPathContent)
-			return
+			return NSPathNotNSErr{msg: fmt.Sprintf("path %q doesn't contain %q", nspath, validPathContent)}
 		}
-		isNS = true
+
+		return nil
 	case NSFS_MAGIC:
 		// Kernel >= 3.19
 
-		isNS = true
+		return nil
 	default:
-		msg = fmt.Sprintf("unknown FS magic: %x", stat.Type)
+		return NSPathNotNSErr{msg: fmt.Sprintf("unknown FS magic on %q: %x", nspath, stat.Type)}
 	}
-	return
 }
 
 // Returns an object representing the namespace referred to by @path
 func GetNS(nspath string) (NetNS, error) {
-	isNS, msg, err := IsNS(nspath)
+	err := IsNSorErr(nspath)
 	if err != nil {
 		return nil, err
 	}
-	if !isNS {
-		return nil, fmt.Errorf("no network namespace detected on %s: %s", nspath, msg)
-	}
 
 	fd, err := os.Open(nspath)
 	if err != nil {
-		return nil, fmt.Errorf("Failed to open %v: %v", nspath, err)
+		return nil, err
 	}
 
 	return &netNS{file: fd}, nil

pkg/ns/ns_test.go

@@ -181,8 +181,8 @@ var _ = Describe("Linux namespace operations", func() {
 
 				_, err = ns.GetNS(nspath)
 				Expect(err).To(HaveOccurred())
-				errString := fmt.Sprintf("%v", err)
-				Expect(errString).To(HavePrefix("no network namespace detected on %s", nspath))
+				Expect(err).To(BeAssignableToTypeOf(ns.NSPathNotNSErr{}))
+				Expect(err).NotTo(BeAssignableToTypeOf(ns.NSPathNotExistErr{}))
 			})
 		})
 
@@ -214,13 +214,11 @@ var _ = Describe("Linux namespace operations", func() {
 		})
 	})
 
-	Describe("IsNS", func() {
+	Describe("IsNSorErr", func() {
 		It("should detect a namespace", func() {
 			createdNetNS, err := ns.NewNS()
-			isNSFS, msg, err := ns.IsNS(createdNetNS.Path())
+			err = ns.IsNSorErr(createdNetNS.Path())
 			Expect(err).NotTo(HaveOccurred())
-			Expect(msg).To(Equal(""))
-			Expect(isNSFS).To(Equal(true))
 		})
 
 		It("should refuse other paths", func() {
@@ -231,9 +229,17 @@ var _ = Describe("Linux namespace operations", func() {
 			nspath := tempFile.Name()
 			defer os.Remove(nspath)
 
-			isNSFS, _, err := ns.IsNS(nspath)
-			Expect(err).NotTo(HaveOccurred())
-			Expect(isNSFS).To(Equal(false))
+			err = ns.IsNSorErr(nspath)
+			Expect(err).To(HaveOccurred())
+			Expect(err).To(BeAssignableToTypeOf(ns.NSPathNotNSErr{}))
+			Expect(err).NotTo(BeAssignableToTypeOf(ns.NSPathNotExistErr{}))
+		})
+
+		It("should error on non-existing paths", func() {
+			err := ns.IsNSorErr("/tmp/IDoNotExist")
+			Expect(err).To(HaveOccurred())
+			Expect(err).To(BeAssignableToTypeOf(ns.NSPathNotExistErr{}))
+			Expect(err).NotTo(BeAssignableToTypeOf(ns.NSPathNotNSErr{}))
 		})
 	})
 })

pkg/skel/skel.go

@@ -36,28 +36,72 @@ type CmdArgs struct {
 	StdinData   []byte
 }
 
+type reqForCmdEntry map[string]bool
+
 // PluginMain is the "main" for a plugin. It accepts
 // two callback functions for add and del commands.
 func PluginMain(cmdAdd, cmdDel func(_ *CmdArgs) error) {
 	var cmd, contID, netns, ifName, args, path string
 
 	vars := []struct {
-		name string
-		val  *string
-		req  bool
+		name      string
+		val       *string
+		reqForCmd reqForCmdEntry
 	}{
-		{"CNI_COMMAND", &cmd, true},
-		{"CNI_CONTAINERID", &contID, false},
-		{"CNI_NETNS", &netns, true},
-		{"CNI_IFNAME", &ifName, true},
-		{"CNI_ARGS", &args, false},
-		{"CNI_PATH", &path, true},
+		{
+			"CNI_COMMAND",
+			&cmd,
+			reqForCmdEntry{
+				"ADD": true,
+				"DEL": true,
+			},
+		},
+		{
+			"CNI_CONTAINERID",
+			&contID,
+			reqForCmdEntry{
+				"ADD": false,
+				"DEL": false,
+			},
+		},
+		{
+			"CNI_NETNS",
+			&netns,
+			reqForCmdEntry{
+				"ADD": true,
+				"DEL": false,
+			},
+		},
+		{
+			"CNI_IFNAME",
+			&ifName,
+			reqForCmdEntry{
+				"ADD": true,
+				"DEL": true,
+			},
+		},
+		{
+			"CNI_ARGS",
+			&args,
+			reqForCmdEntry{
+				"ADD": false,
+				"DEL": false,
+			},
+		},
+		{
+			"CNI_PATH",
+			&path,
+			reqForCmdEntry{
+				"ADD": true,
+				"DEL": true,
+			},
+		},
 	}
 
 	argsMissing := false
 	for _, v := range vars {
 		*v.val = os.Getenv(v.name)
-		if v.req && *v.val == "" {
+		if v.reqForCmd[cmd] && *v.val == "" {
 			log.Printf("%v env variable missing", v.name)
 			argsMissing = true
 		}

pkg/skel/skel_test.go

@@ -71,5 +71,14 @@ var _ = Describe("Skel", func() {
 		// 	Expect(err).NotTo(HaveOccurred())
 		// 	PluginMain(fErr, nil)
 		// })
+
+		It("should not fail with DEL and no NETNS and noop callback", func() {
+			err := os.Setenv("CNI_COMMAND", "DEL")
+			Expect(err).NotTo(HaveOccurred())
+			err = os.Unsetenv("CNI_NETNS")
+			Expect(err).NotTo(HaveOccurred())
+			PluginMain(nil, fNoop)
+		})
+
 	})
 })

plugins/main/bridge/bridge.go

@@ -289,6 +289,10 @@ func cmdDel(args *skel.CmdArgs) error {
 		return err
 	}
 
+	if args.Netns == "" {
+		return nil
+	}
+
 	var ipn *net.IPNet
 	err = ns.WithNetNSPath(args.Netns, func(_ ns.NetNS) error {
 		var err error

plugins/main/ipvlan/ipvlan.go

@@ -152,6 +152,10 @@ func cmdDel(args *skel.CmdArgs) error {
 		return err
 	}
 
+	if args.Netns == "" {
+		return nil
+	}
+
 	return ns.WithNetNSPath(args.Netns, func(_ ns.NetNS) error {
 		return ip.DelLinkByName(args.IfName)
 	})

plugins/main/macvlan/macvlan.go

@@ -170,6 +170,10 @@ func cmdDel(args *skel.CmdArgs) error {
 		return err
 	}
 
+	if args.Netns == "" {
+		return nil
+	}
+
 	return ns.WithNetNSPath(args.Netns, func(_ ns.NetNS) error {
 		return ip.DelLinkByName(args.IfName)
 	})

plugins/main/ptp/ptp.go

@@ -199,6 +199,10 @@ func cmdDel(args *skel.CmdArgs) error {
 		return err
 	}
 
+	if args.Netns == "" {
+		return nil
+	}
+
 	var ipn *net.IPNet
 	err := ns.WithNetNSPath(args.Netns, func(_ ns.NetNS) error {
 		var err error