Correctly handle named pipe host mounts for Windows

Signed-off-by: Deep Debroy <ddebroy@docker.com>

pkg/kubelet/kubelet_pods.go

@@ -215,14 +215,15 @@ func makeMounts(pod *v1.Pod, podDir string, container *v1.Container, hostName, h
 			}
 		}
 
-		// Docker Volume Mounts fail on Windows if it is not of the form C:/
+		// Docker Volume Mounts fail on Windows if it is not of the form C:/ nor a named pipe starting with \\.\pipe\
 		containerPath := mount.MountPath
 		if runtime.GOOS == "windows" {
-			if (strings.HasPrefix(hostPath, "/") || strings.HasPrefix(hostPath, "\\")) && !strings.Contains(hostPath, ":") {
+			if !volumeutil.IsWindowsNamedPipe(runtime.GOOS, hostPath) && (strings.HasPrefix(hostPath, "/") || strings.HasPrefix(hostPath, "\\")) && !strings.Contains(hostPath, ":") {
 				hostPath = "c:" + hostPath
 			}
 		}
-		if !filepath.IsAbs(containerPath) {
+		// IsAbs returns false for named pipes (\\.\pipe\...) in Windows. So check for it specifically and skip MakeAbsolutePath
+		if !volumeutil.IsWindowsNamedPipe(runtime.GOOS, containerPath) && !filepath.IsAbs(containerPath) {
 			containerPath = volumeutil.MakeAbsolutePath(runtime.GOOS, containerPath)
 		}
 

pkg/volume/util/util.go

@@ -945,6 +945,13 @@ func CheckPersistentVolumeClaimModeBlock(pvc *v1.PersistentVolumeClaim) bool {
 	return utilfeature.DefaultFeatureGate.Enabled(features.BlockVolume) && pvc.Spec.VolumeMode != nil && *pvc.Spec.VolumeMode == v1.PersistentVolumeBlock
 }
 
+func IsWindowsNamedPipe(goos, path string) bool {
+	if goos == "windows" && strings.HasPrefix(path, `\\.\pipe\`) {
+		return true
+	}
+	return false
+}
+
 // MakeAbsolutePath convert path to absolute path according to GOOS
 func MakeAbsolutePath(goos, path string) string {
 	if goos != "windows" {

pkg/volume/util/util_test.go

@@ -2373,6 +2373,47 @@ func TestGetWindowsPath(t *testing.T) {
 	}
 }
 
+func TestIsWindowsNamedPipe(t *testing.T) {
+	tests := []struct {
+		goos        string
+		path        string
+		isNamedPipe bool
+	}{
+		{
+			goos:        "linux",
+			path:        `/usr/bin`,
+			isNamedPipe: false,
+		},
+		{
+			goos:        "linux",
+			path:        `\\.\pipe\foo`,
+			isNamedPipe: false,
+		},
+		{
+			goos:        "windows",
+			path:        `C:\foo`,
+			isNamedPipe: false,
+		},
+		{
+			goos:        "windows",
+			path:        `\\.\invalid`,
+			isNamedPipe: false,
+		},
+		{
+			goos:        "windows",
+			path:        `\\.\pipe\valid_pipe`,
+			isNamedPipe: true,
+		},
+	}
+
+	for _, test := range tests {
+		result := IsWindowsNamedPipe(test.goos, test.path)
+		if result != test.isNamedPipe {
+			t.Errorf("IsWindowsNamedPipe(%v) returned (%v), expected (%v)", test.path, result, test.isNamedPipe)
+		}
+	}
+}
+
 func TestMakeAbsolutePath(t *testing.T) {
 	tests := []struct {
 		goos         string