Implements Windows volume/mount support

Based on WSL2 9p support: remaps windows paths to /mnt/<drive> locations for
both podman and Docker API clients.

Signed-off-by: Jason T. Greene <jason.greene@redhat.com>

5 files changed, 158 insertions, 2 deletions

diff --git a/pkg/specgen/volumes.go b/pkg/specgen/volumes.go
index eca8c0c35..b26666df3 100644
--- a/pkg/specgen/volumes.go
+++ b/pkg/specgen/volumes.go
@@ -65,7 +65,7 @@ func GenVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*Na
 			err     error
 		)
 
-		splitVol := strings.Split(vol, ":")
+		splitVol := SplitVolumeString(vol)
 		if len(splitVol) > 3 {
 			return nil, nil, nil, errors.Wrapf(volumeFormatErr, vol)
 		}
@@ -93,7 +93,7 @@ func GenVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*Na
 			}
 		}
 
-		if strings.HasPrefix(src, "/") || strings.HasPrefix(src, ".") {
+		if strings.HasPrefix(src, "/") || strings.HasPrefix(src, ".") || isHostWinPath(src) {
 			// This is not a named volume
 			overlayFlag := false
 			chownFlag := false
@@ -152,3 +152,26 @@ func GenVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*Na
 
 	return mounts, volumes, overlayVolumes, nil
 }
+
+// Splits a volume string, accounting for Win drive paths
+// when running as a WSL linux guest or Windows client
+func SplitVolumeString(vol string) []string {
+	parts := strings.Split(vol, ":")
+	if !shouldResolveWinPaths() {
+		return parts
+	}
+
+	// Skip extended marker prefix if present
+	n := 0
+	if strings.HasPrefix(vol, `\\?\`) {
+		n = 4
+	}
+
+	if hasWinDriveScheme(vol, n) {
+		first := parts[0] + ":" + parts[1]
+		parts = parts[1:]
+		parts[0] = first
+	}
+
+	return parts
+}
diff --git a/pkg/specgen/winpath.go b/pkg/specgen/winpath.go
new file mode 100644
index 000000000..f4249fab1
--- /dev/null
+++ b/pkg/specgen/winpath.go
@@ -0,0 +1,59 @@
+package specgen
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+
+	"github.com/pkg/errors"
+)
+
+func isHostWinPath(path string) bool {
+	return shouldResolveWinPaths() && strings.HasPrefix(path, `\\`) || hasWinDriveScheme(path, 0) || winPathExists(path)
+}
+
+func hasWinDriveScheme(path string, start int) bool {
+	if len(path) < start+2 || path[start+1] != ':' {
+		return false
+	}
+
+	drive := rune(path[start])
+	return drive < unicode.MaxASCII && unicode.IsLetter(drive)
+}
+
+// Converts a Windows path to a WSL guest path if local env is a WSL linux guest or this is a Windows client.
+func ConvertWinMountPath(path string) (string, error) {
+	if !shouldResolveWinPaths() {
+		return path, nil
+	}
+
+	if strings.HasPrefix(path, "/") {
+		// Handle /[driveletter]/windows/path form (e.g. c:\Users\bar == /c/Users/bar)
+		if len(path) > 2 && path[2] == '/' && shouldResolveUnixWinVariant(path) {
+			drive := unicode.ToLower(rune(path[1]))
+			if unicode.IsLetter(drive) && drive <= unicode.MaxASCII {
+				return fmt.Sprintf("/mnt/%c/%s", drive, path[3:]), nil
+			}
+		}
+
+		// unix path - pass through
+		return path, nil
+	}
+
+	// Convert remote win client relative paths to absolute
+	path = resolveRelativeOnWindows(path)
+
+	// Strip extended marker prefix if present
+	path = strings.TrimPrefix(path, `\\?\`)
+
+	// Drive installed via wsl --mount
+	if strings.HasPrefix(path, `\\.\`) {
+		path = "/mnt/wsl/" + path[4:]
+	} else if len(path) > 1 && path[1] == ':' {
+		path = "/mnt/" + strings.ToLower(path[0:1]) + path[2:]
+	} else {
+		return path, errors.New("unsupported UNC path")
+	}
+
+	return strings.ReplaceAll(path, `\`, "/"), nil
+}
diff --git a/pkg/specgen/winpath_linux.go b/pkg/specgen/winpath_linux.go
new file mode 100644
index 000000000..f42ac7639
--- /dev/null
+++ b/pkg/specgen/winpath_linux.go
@@ -0,0 +1,24 @@
+package specgen
+
+import (
+	"os"
+
+	"github.com/containers/common/pkg/machine"
+)
+
+func shouldResolveWinPaths() bool {
+	return machine.MachineHostType() == "wsl"
+}
+
+func shouldResolveUnixWinVariant(path string) bool {
+	_, err := os.Stat(path)
+	return err != nil
+}
+
+func resolveRelativeOnWindows(path string) string {
+	return path
+}
+
+func winPathExists(path string) bool {
+	return false
+}
diff --git a/pkg/specgen/winpath_unsupported.go b/pkg/specgen/winpath_unsupported.go
new file mode 100644
index 000000000..4cd008fdd
--- /dev/null
+++ b/pkg/specgen/winpath_unsupported.go
@@ -0,0 +1,20 @@
+//go:build !linux && !windows
+// +build !linux,!windows
+
+package specgen
+
+func shouldResolveWinPaths() bool {
+	return false
+}
+
+func shouldResolveUnixWinVariant(path string) bool {
+	return false
+}
+
+func resolveRelativeOnWindows(path string) string {
+	return path
+}
+
+func winPathExists(path string) bool {
+	return false
+}
diff --git a/pkg/specgen/winpath_windows.go b/pkg/specgen/winpath_windows.go
new file mode 100644
index 000000000..c6aad314a
--- /dev/null
+++ b/pkg/specgen/winpath_windows.go
@@ -0,0 +1,30 @@
+package specgen
+
+import (
+	"github.com/sirupsen/logrus"
+	"os"
+	"path/filepath"
+)
+
+func shouldResolveUnixWinVariant(path string) bool {
+	return true
+}
+
+func shouldResolveWinPaths() bool {
+	return true
+}
+
+func resolveRelativeOnWindows(path string) string {
+	ret, err := filepath.Abs(path)
+	if err != nil {
+		logrus.Debugf("problem resolving possible relative path %q: %s", path, err.Error())
+		return path
+	}
+
+	return ret
+}
+
+func winPathExists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}