Fix resolving chained symlinks with the WinFSP VFS

MODULE.bazel

@@ -23,7 +23,7 @@ git_override(
 
 git_override(
     module_name = "com_github_buildbarn_bb_storage",
-    commit = "6002cad335378bbdcdda4225d47c7dc2c08a6d94",
+    commit = "6d689475d039c4ac5984f977066cb5249f6a9c6f",
     remote = "https://github.com/buildbarn/bb-storage.git",
 )
 

cmd/bb_noop_worker/BUILD.bazel

@@ -18,6 +18,7 @@ go_library(
         "@com_github_buildbarn_bb_storage//pkg/global",
         "@com_github_buildbarn_bb_storage//pkg/program",
         "@com_github_buildbarn_bb_storage//pkg/util",
+        "@com_github_buildbarn_bb_storage//pkg/zstd",
         "@org_golang_google_grpc//codes",
         "@org_golang_google_grpc//status",
     ],

cmd/bb_noop_worker/main.go

@@ -16,6 +16,7 @@ import (
 	"github.com/buildbarn/bb-storage/pkg/global"
 	"github.com/buildbarn/bb-storage/pkg/program"
 	"github.com/buildbarn/bb-storage/pkg/util"
+	bb_zstd "github.com/buildbarn/bb-storage/pkg/zstd"
 
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
@@ -48,7 +49,8 @@ func main() {
 			configuration.ContentAddressableStorage,
 			blobstore_configuration.NewCASBlobAccessCreator(
 				grpcClientFactory,
-				int(configuration.MaximumMessageSizeBytes)))
+				int(configuration.MaximumMessageSizeBytes),
+				bb_zstd.NewPoolFromConfiguration(nil)))
 		if err != nil {
 			return util.StatusWrap(err, "Failed to create Content Adddressable Storage")
 		}

cmd/bb_scheduler/BUILD.bazel

@@ -50,6 +50,7 @@ go_library(
         "@com_github_buildbarn_bb_storage//pkg/proto/iscc",
         "@com_github_buildbarn_bb_storage//pkg/random",
         "@com_github_buildbarn_bb_storage//pkg/util",
+        "@com_github_buildbarn_bb_storage//pkg/zstd",
         "@com_github_google_uuid//:uuid",
         "@com_github_gorilla_mux//:mux",
         "@org_golang_google_grpc//:grpc",

cmd/bb_scheduler/main.go

@@ -28,6 +28,7 @@ import (
 	"github.com/buildbarn/bb-storage/pkg/proto/iscc"
 	"github.com/buildbarn/bb-storage/pkg/random"
 	"github.com/buildbarn/bb-storage/pkg/util"
+	bb_zstd "github.com/buildbarn/bb-storage/pkg/zstd"
 	"github.com/google/uuid"
 	"github.com/gorilla/mux"
 
@@ -63,7 +64,8 @@ func main() {
 			configuration.ContentAddressableStorage,
 			blobstore_configuration.NewCASBlobAccessCreator(
 				grpcClientFactory,
-				int(configuration.MaximumMessageSizeBytes)))
+				int(configuration.MaximumMessageSizeBytes),
+				bb_zstd.NewPoolFromConfiguration(nil)))
 		if err != nil {
 			return util.StatusWrap(err, "Failed to create Content Adddressable Storage")
 		}

cmd/bb_worker/BUILD.bazel

@@ -35,6 +35,7 @@ go_library(
         "@com_github_buildbarn_bb_storage//pkg/program",
         "@com_github_buildbarn_bb_storage//pkg/random",
         "@com_github_buildbarn_bb_storage//pkg/util",
+        "@com_github_buildbarn_bb_storage//pkg/zstd",
         "@com_github_google_uuid//:uuid",
         "@io_opentelemetry_go_otel//:otel",
         "@org_golang_google_grpc//codes",

cmd/bb_worker/main.go

@@ -38,6 +38,7 @@ import (
 	"github.com/buildbarn/bb-storage/pkg/program"
 	"github.com/buildbarn/bb-storage/pkg/random"
 	"github.com/buildbarn/bb-storage/pkg/util"
+	bb_zstd "github.com/buildbarn/bb-storage/pkg/zstd"
 	"github.com/google/uuid"
 
 	"golang.org/x/sync/semaphore"
@@ -88,7 +89,8 @@ func main() {
 			dependenciesGroup,
 			configuration.Blobstore,
 			grpcClientFactory,
-			int(configuration.MaximumMessageSizeBytes))
+			int(configuration.MaximumMessageSizeBytes),
+			bb_zstd.NewPoolFromConfiguration(nil))
 		if err != nil {
 			return err
 		}

go.mod

@@ -16,7 +16,7 @@ require (
 	github.com/bazelbuild/buildtools v0.0.0-20260211083412-859bfffeef82
 	github.com/bazelbuild/remote-apis v0.0.0-20260216160025-715b73f3f9e4
 	github.com/bazelbuild/rules_go v0.59.0
-	github.com/buildbarn/bb-storage v0.0.0-20260303071613-6002cad33537
+	github.com/buildbarn/bb-storage v0.0.0-20260316192935-6d689475d039
 	github.com/buildbarn/go-xdr v0.0.0-20240702182809-236788cf9e89
 	github.com/golang/protobuf v1.5.4
 	github.com/google/uuid v1.6.0

go.sum

@@ -79,8 +79,8 @@ github.com/bazelbuild/rules_go v0.59.0/go.mod h1:Pn30cb4M513fe2rQ6GiJ3q8QyrRsgC7
 github.com/benbjohnson/clock v1.1.0/go.mod h1:J11/hYXuz8f4ySSvYwY0FKfm+ezbsZBKZxNJlLklBHA=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
-github.com/buildbarn/bb-storage v0.0.0-20260303071613-6002cad33537 h1:81k5KiFlYyaQaheb5pe9p/nz4Ao8jGWcNK5LC9z+8vE=
-github.com/buildbarn/bb-storage v0.0.0-20260303071613-6002cad33537/go.mod h1:96kqnkrdkHHi94Agje3NM8qwrYMxJRSkAqsb7oXRhNI=
+github.com/buildbarn/bb-storage v0.0.0-20260316192935-6d689475d039 h1:vqWwW9H2R6ACSWkJisorYsSn9qsAbv9nbjqMM0BJhyI=
+github.com/buildbarn/bb-storage v0.0.0-20260316192935-6d689475d039/go.mod h1:96kqnkrdkHHi94Agje3NM8qwrYMxJRSkAqsb7oXRhNI=
 github.com/buildbarn/go-sha256tree v0.0.0-20250310211320-0f70f20e855b h1:IKUxixGBm9UxobU7c248z0BF0ojG19uoSLz8MFZM/KA=
 github.com/buildbarn/go-sha256tree v0.0.0-20250310211320-0f70f20e855b/go.mod h1:e7g3/yWApcg+PpDqd4eQEEV8pexQmfCgK3frP+1Wuvk=
 github.com/buildbarn/go-xdr v0.0.0-20240702182809-236788cf9e89 h1:Wtpgk4CIkoEJ7Qx3BwjaMp3TOVv834heqyCC9jMKStM=

pkg/filesystem/virtual/BUILD.bazel

@@ -26,6 +26,8 @@ go_library(
         "leaf.go",
         "linkable_leaf.go",
         "named_attributes_factory.go",
+        "native_symlink_target_unix.go",
+        "native_symlink_target_windows.go",
         "nfs_handle_allocator.go",
         "node.go",
         "permissions.go",

pkg/filesystem/virtual/base_symlink_factory.go

@@ -32,7 +32,7 @@ func (f symlink) readlinkParser() (path.Parser, error) {
 	if !utf8.Valid(f.target) {
 		return nil, status.Error(codes.InvalidArgument, "Symbolic link contents are not valid UTF-8")
 	}
-	return path.UNIXFormat.NewParser(string(f.target)), nil
+	return path.LocalFormat.NewParser(string(f.target)), nil
 }
 
 func (f symlink) readlinkString() (string, error) {

pkg/filesystem/virtual/cas_initial_contents_fetcher.go

@@ -110,7 +110,14 @@ func (icf *casInitialContentsFetcher) fetchContentsUnwrapped(fileReadMonitorFact
 			return nil, status.Errorf(codes.InvalidArgument, "Directory contains multiple children named %#v", entry.Name)
 		}
 
-		leaf := icf.options.symlinkFactory.LookupSymlink([]byte(entry.Target))
+		// REv2 symlink targets use UNIX path separators. Convert
+		// to the native platform format so that the stored bytes
+		// can be returned verbatim by VirtualReadlink.
+		target, err := nativeSymlinkTarget(entry.Target)
+		if err != nil {
+			return nil, util.StatusWrapf(err, "Failed to normalize target of symlink %#v", entry.Name)
+		}
+		leaf := icf.options.symlinkFactory.LookupSymlink(target)
 		children[component] = InitialChild{}.FromLeaf(leaf)
 		leavesToUnlink = append(leavesToUnlink, leaf)
 	}

pkg/filesystem/virtual/native_symlink_target_unix.go

@@ -0,0 +1,10 @@
+//go:build !windows
+
+package virtual
+
+// nativeSymlinkTarget converts a REv2 symlink target (UNIX format)
+// to the native platform format. On UNIX this is a no-op, as REv2
+// already uses UNIX path separators.
+func nativeSymlinkTarget(target string) ([]byte, error) {
+	return []byte(target), nil
+}

pkg/filesystem/virtual/native_symlink_target_windows.go

@@ -0,0 +1,22 @@
+//go:build windows
+
+package virtual
+
+import "github.com/buildbarn/bb-storage/pkg/filesystem/path"
+
+// nativeSymlinkTarget converts a REv2 symlink target (UNIX format)
+// to the native platform format. On Windows this converts forward
+// slashes to backslashes and strips trailing directory separators
+// that would cause issues in reparse point substitute names.
+func nativeSymlinkTarget(target string) ([]byte, error) {
+	targetParser := path.UNIXFormat.NewParser(target)
+	targetPath, scopeWalker := path.EmptyBuilder.Join(path.VoidScopeWalker)
+	if err := path.Resolve(targetParser, scopeWalker); err != nil {
+		return nil, err
+	}
+	s, err := targetPath.GetWindowsString(path.WindowsPathFormatStandard)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(s), nil
+}

pkg/filesystem/virtual/winfsp/BUILD.bazel

@@ -68,12 +68,17 @@ go_test(
     tags = ["manual"],
     deps = select({
         "@rules_go//go/platform:windows": [
+            "//pkg/cas",
             "//pkg/filesystem/pool",
             "//pkg/filesystem/virtual",
             "//pkg/filesystem/virtual/configuration",
             "//pkg/proto/configuration/filesystem/virtual",
+            "@bazel_remote_apis//build/bazel/remote/execution/v2:remote_execution_go_proto",
             "@com_github_buildbarn_bb_storage//pkg/blockdevice",
             "@com_github_buildbarn_bb_storage//pkg/clock",
+            "@com_github_buildbarn_bb_storage//pkg/digest",
+            "@com_github_buildbarn_bb_storage//pkg/filesystem",
+            "@com_github_buildbarn_bb_storage//pkg/filesystem/path",
             "@com_github_buildbarn_bb_storage//pkg/program",
             "@com_github_buildbarn_bb_storage//pkg/util",
             "@com_github_stretchr_testify//require",

pkg/filesystem/virtual/winfsp/file_system.go

@@ -1352,17 +1352,17 @@ func getReparsePointForLeaf(ctx context.Context, leaf virtual.Leaf, buffer []byt
 		return 0, nil
 	}
 
-	// Parse the path to determine if it's absolute
+	// Symlink targets are stored in native (Windows) format, so
+	// we can pass them directly to FillSymlinkReparseBuffer.
 	w := relativePathChecker{}
 	if err := path.Resolve(path.LocalFormat.NewParser(string(target)), &w); err != nil {
 		return 0, err
 	}
-	var flags int
+	var flags uint32
 	if w.isRelative {
-		flags = windowsext.SYMLINK_FLAG_RELATIVE
+		flags = uint32(windowsext.SYMLINK_FLAG_RELATIVE)
 	}
-
-	return FillSymlinkReparseBuffer(string(target), uint32(flags), buffer)
+	return FillSymlinkReparseBuffer(string(target), flags, buffer)
 }
 
 func (fs *FileSystem) GetReparsePoint(ref *ffi.FileSystemRef, file uintptr, name string, buffer []byte) (int, error) {