exporter: support source-date-epoch for tar exporter

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

client/client_test.go

@@ -170,6 +170,7 @@ func TestIntegration(t *testing.T) {
 		testSourceDateEpochClamp,
 		testSourceDateEpochReset,
 		testSourceDateEpochLocalExporter,
+		testSourceDateEpochTarExporter,
 	)
 	tests = append(tests, diffOpTestCases()...)
 	integration.Run(t, tests, mirrors)
@@ -2333,7 +2334,6 @@ func testSourceDateEpochReset(t *testing.T, sb integration.Sandbox) {
 }
 
 func testSourceDateEpochLocalExporter(t *testing.T, sb integration.Sandbox) {
-	integration.SkipIfDockerd(t, sb, "oci exporter")
 	requiresLinux(t)
 	c, err := New(sb.Context(), sb.Address())
 	require.NoError(t, err)
@@ -2382,6 +2382,62 @@ func testSourceDateEpochLocalExporter(t *testing.T, sb integration.Sandbox) {
 	checkAllReleasable(t, c, sb, true)
 }
 
+func testSourceDateEpochTarExporter(t *testing.T, sb integration.Sandbox) {
+	requiresLinux(t)
+	c, err := New(sb.Context(), sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	busybox := llb.Image("busybox:latest")
+	st := llb.Scratch()
+
+	run := func(cmd string) {
+		st = busybox.Run(llb.Shlex(cmd), llb.Dir("/wd")).AddMount("/wd", st)
+	}
+
+	run(`sh -c "echo -n first > foo"`)
+	run(`sh -c "echo -n second > bar"`)
+
+	def, err := st.Marshal(sb.Context())
+	require.NoError(t, err)
+
+	destDir, err := os.MkdirTemp("", "buildkit")
+	require.NoError(t, err)
+	defer os.RemoveAll(destDir)
+
+	out := filepath.Join(destDir, "out.tar")
+	outW, err := os.Create(out)
+	require.NoError(t, err)
+
+	tm := time.Date(2015, time.October, 21, 7, 28, 0, 0, time.UTC)
+
+	_, err = c.Solve(sb.Context(), def, SolveOpt{
+		FrontendAttrs: map[string]string{
+			"build-arg:SOURCE_DATE_EPOCH": fmt.Sprintf("%d", tm.Unix()),
+		},
+		Exports: []ExportEntry{
+			{
+				Type:   ExporterTar,
+				Output: fixedWriteCloser(outW),
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	dt, err := os.ReadFile(out)
+	require.NoError(t, err)
+
+	m, err := testutil.ReadTarToMap(dt, false)
+	require.NoError(t, err)
+
+	require.Equal(t, len(m), 2)
+
+	require.Equal(t, tm.Format(time.RFC3339), m["foo"].Header.ModTime.Format(time.RFC3339))
+	require.Equal(t, tm.Format(time.RFC3339), m["bar"].Header.ModTime.Format(time.RFC3339))
+
+	checkAllReleasable(t, c, sb, true)
+}
+
 func testFrontendMetadataReturn(t *testing.T, sb integration.Sandbox) {
 	requiresLinux(t)
 	c, err := New(sb.Context(), sb.Address())

exporter/tar/export.go

@@ -10,6 +10,7 @@ import (
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/moby/buildkit/cache"
 	"github.com/moby/buildkit/exporter"
+	"github.com/moby/buildkit/exporter/util/epoch"
 	"github.com/moby/buildkit/session"
 	"github.com/moby/buildkit/session/filesync"
 	"github.com/moby/buildkit/snapshot"
@@ -43,6 +44,12 @@ func New(opt Opt) (exporter.Exporter, error) {
 func (e *localExporter) Resolve(ctx context.Context, opt map[string]string) (exporter.ExporterInstance, error) {
 	li := &localExporterInstance{localExporter: e}
 
+	tm, _, err := epoch.ParseAttr(opt)
+	if err != nil {
+		return nil, err
+	}
+	li.epoch = tm
+
 	v, ok := opt[preferNondistLayersKey]
 	if ok {
 		b, err := strconv.ParseBool(v)
@@ -58,6 +65,7 @@ func (e *localExporter) Resolve(ctx context.Context, opt map[string]string) (exp
 type localExporterInstance struct {
 	*localExporter
 	preferNonDist bool
+	epoch         *time.Time
 }
 
 func (e *localExporterInstance) Name() string {
@@ -77,6 +85,14 @@ func (e *localExporterInstance) Export(ctx context.Context, inp exporter.Source,
 		}
 	}()
 
+	if e.epoch == nil {
+		if tm, ok, err := epoch.ParseSource(inp); err != nil {
+			return nil, err
+		} else if ok {
+			e.epoch = tm
+		}
+	}
+
 	getDir := func(ctx context.Context, k string, ref cache.ImmutableRef) (*fsutil.Dir, error) {
 		var src string
 		var err error
@@ -106,9 +122,10 @@ func (e *localExporterInstance) Export(ctx context.Context, inp exporter.Source,
 		}
 
 		walkOpt := &fsutil.WalkOpt{}
+		var idMapFunc func(p string, st *fstypes.Stat) fsutil.MapResult
 
 		if idmap != nil {
-			walkOpt.Map = func(p string, st *fstypes.Stat) fsutil.MapResult {
+			idMapFunc = func(p string, st *fstypes.Stat) fsutil.MapResult {
 				uid, gid, err := idmap.ToContainer(idtools.Identity{
 					UID: int(st.Uid),
 					GID: int(st.Gid),
@@ -122,12 +139,28 @@ func (e *localExporterInstance) Export(ctx context.Context, inp exporter.Source,
 			}
 		}
 
+		walkOpt.Map = func(p string, st *fstypes.Stat) fsutil.MapResult {
+			res := fsutil.MapResultKeep
+			if idMapFunc != nil {
+				res = idMapFunc(p, st)
+			}
+			if e.epoch != nil {
+				st.ModTime = e.epoch.UnixNano()
+			}
+			return res
+		}
+
+		st := fstypes.Stat{
+			Mode: uint32(os.ModeDir | 0755),
+			Path: strings.Replace(k, "/", "_", -1),
+		}
+		if e.epoch != nil {
+			st.ModTime = e.epoch.UnixNano()
+		}
+
 		return &fsutil.Dir{
-			FS: fsutil.NewFS(src, walkOpt),
-			Stat: fstypes.Stat{
-				Mode: uint32(os.ModeDir | 0755),
-				Path: strings.Replace(k, "/", "_", -1),
-			},
+			FS:   fsutil.NewFS(src, walkOpt),
+			Stat: st,
 		}, nil
 	}