Fix registration socket removal on windows.

- Until the bug - golang/go#33357 is fixed, os.stat wouldn't return the
  right mode(socket) on windows. Hence deleting the file, without checking whether
  its a socket, on windows.

- Place os specific logic into util_{linux, windows} files.

cmd/csi-node-driver-registrar/node_register.go

@@ -36,16 +36,8 @@ func nodeRegister(
 	// pluginswatcher infrastructure. Node labeling is done by kubelet's csi code.
 	registrar := newRegistrationServer(csiDriverName, *kubeletRegistrationPath, supportedVersions)
 	socketPath := fmt.Sprintf("/registration/%s-reg.sock", csiDriverName)
-	fi, err := os.Stat(socketPath)
-	if err == nil && (fi.Mode()&os.ModeSocket) != 0 {
-		// Remove any socket, stale or not, but fall through for other files
-		if err := os.Remove(socketPath); err != nil {
-			klog.Errorf("failed to remove stale socket %s with error: %+v", socketPath, err)
-			os.Exit(1)
-		}
-	}
-	if err != nil && !os.IsNotExist(err) {
-		klog.Errorf("failed to stat the socket %s with error: %+v", socketPath, err)
+	if err := cleanupSocketFile(socketPath); err != nil {
+		klog.Errorf("%+v", err)
 		os.Exit(1)
 	}
 

cmd/csi-node-driver-registrar/util_linux.go

@@ -19,9 +19,26 @@ limitations under the License.
 package main
 
 import (
+	"fmt"
+	"os"
+
 	"golang.org/x/sys/unix"
 )
 
 func umask(mask int) (int, error) {
 	return unix.Umask(mask), nil
 }
+
+func cleanupSocketFile(socketPath string) error {
+	fi, err := os.Stat(socketPath)
+	if err == nil && (fi.Mode()&os.ModeSocket) != 0 {
+		// Remove any socket, stale or not, but fall through for other files
+		if err := os.Remove(socketPath); err != nil {
+			return fmt.Errorf("failed to remove stale socket %s with error: %+v", socketPath, err)
+		}
+	}
+	if err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("failed to stat the socket %s with error: %+v", socketPath, err)
+	}
+	return nil
+}

cmd/csi-node-driver-registrar/util_windows.go

@@ -20,8 +20,28 @@ package main
 
 import (
 	"errors"
+	"fmt"
+	"os"
 )
 
 func umask(mask int) (int, error) {
 	return -1, errors.New("umask not supported in Windows")
 }
+
+func cleanupSocketFile(socketPath string) error {
+	if _, err := os.Lstat(socketPath); err != nil {
+		// If the file does not exist, then the cleanup can be considered successful.
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("failed to lstat the socket %s with error: %+v", socketPath, err)
+	}
+
+	// TODO: Until the bug - https://github.com/golang/go/issues/33357 is fixed, os.stat wouldn't return the
+	// right mode(socket) on windows. Hence deleting the file, without checking whether
+	// its a socket, on windows.
+	if err := os.Remove(socketPath); err != nil {
+		return fmt.Errorf("failed to remove stale socket %s with error: %+v", socketPath, err)
+	}
+	return nil
+}