From 3bac814ea9f8468499c65c9b2b0a6f023e23d35e Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher <jakobunt@gmail.com>
Date: Sat, 22 Jan 2022 12:40:24 +0100
Subject: [PATCH] tests: add TestRenameWhiteout, TestRenameExchange

f
---
 tests/defaults/overlayfs_test.go | 109 +++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 tests/defaults/overlayfs_test.go

diff --git a/tests/defaults/overlayfs_test.go b/tests/defaults/overlayfs_test.go
new file mode 100644
index 0000000..1a3298d
--- /dev/null
+++ b/tests/defaults/overlayfs_test.go
@@ -0,0 +1,109 @@
+// +build linux
+
+package defaults
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
+	"github.com/rfjakob/gocryptfs/v2/tests/test_helpers"
+)
+
+// https://github.com/rfjakob/gocryptfs/issues/641
+//
+// I was trying to run the Docker daemon with the recommended overlay2 storage driver, and encrypt its `/var/lib/docker` directory using gocryptfs. overlay2 was giving me the following errors:
+// ```
+// Jan 21 19:09:43 friedhelm.rankenste.in kernel: overlayfs: upper fs does not support tmpfile.
+// Jan 21 19:09:43 friedhelm.rankenste.in kernel: overlayfs: upper fs does not support RENAME_WHITEOUT.
+// Jan 21 19:09:43 friedhelm.rankenste.in kernel: overlayfs: upper fs missing required features.
+// ```
+
+func TestRenameWhiteout(t *testing.T) {
+	short := t.Name() + ".short"
+	long := t.Name() + strings.Repeat(".long", 200/len(".long"))
+
+	names := [][]string{
+		// short to short
+		{short + "s2s", short + "s2s2"},
+		// short to long
+		{short + "s2l", long + "s2l2"},
+		// long to short
+		{long + "l2s", short + "l2s2"},
+		// long to long
+		{long + "l2l", short + "l2l2"},
+	}
+
+	for _, flags := range []uint{syscallcompat.RENAME_WHITEOUT, syscallcompat.RENAME_WHITEOUT | syscallcompat.RENAME_NOREPLACE} {
+		for _, n := range names {
+			pSrc := test_helpers.DefaultPlainDir + "/" + n[0]
+			pDst := test_helpers.DefaultPlainDir + "/" + n[1]
+			if err := ioutil.WriteFile(pSrc, nil, 0200); err != nil {
+				t.Fatalf("creating empty file failed: %v", err)
+			}
+			err := unix.Renameat2(-1, pSrc, -1, pDst, flags)
+			if err != nil {
+				t.Error(err)
+			}
+			// readdir should not choke on leftover or missing .name files
+			_, err = os.ReadDir(test_helpers.DefaultPlainDir)
+			if err != nil {
+				t.Error(err)
+			}
+			// pSrc should now be a character device 0 file
+			var st unix.Stat_t
+			err = unix.Stat(pSrc, &st)
+			if err != nil {
+				t.Error(err)
+			}
+			if !(st.Mode&unix.S_IFMT == unix.S_IFCHR) {
+				t.Error("not a device file")
+			}
+			if st.Rdev != 0 {
+				t.Errorf("want device 0, have %d", st.Rdev)
+			}
+			unix.Unlink(pSrc)
+			unix.Unlink(pDst)
+		}
+	}
+}
+
+func TestRenameExchange(t *testing.T) {
+	short := t.Name() + ".short"
+	long := t.Name() + strings.Repeat(".long", 200/len(".long"))
+
+	names := [][]string{
+		// short to short
+		{short + "s2s", short + "s2s2"},
+		// short to long
+		{short + "s2l", long + "s2l2"},
+		// long to short
+		{long + "l2s", short + "l2s2"},
+		// long to long
+		{long + "l2l", short + "l2l2"},
+	}
+
+	for _, n := range names {
+		pSrc := test_helpers.DefaultPlainDir + "/" + n[0]
+		pDst := test_helpers.DefaultPlainDir + "/" + n[1]
+		if err := ioutil.WriteFile(pSrc, nil, 0200); err != nil {
+			t.Fatalf("creating empty file failed: %v", err)
+		}
+		if err := ioutil.WriteFile(pDst, nil, 0200); err != nil {
+			t.Fatalf("creating empty file failed: %v", err)
+		}
+		err := unix.Renameat2(-1, pSrc, -1, pDst, unix.RENAME_EXCHANGE)
+		if err != nil {
+			t.Error(err)
+		}
+		// readdir should not choke on leftover or missing .name files
+		_, err = os.ReadDir(test_helpers.DefaultPlainDir)
+		if err != nil {
+			t.Error(err)
+		}
+	}
+}