1 files changed, 47 insertions, 0 deletions
diff --git a/tests/cluster/poc_test.go b/tests/cluster/poc_test.go
new file mode 100644
index 0000000..4d7182a
--- /dev/null
+++ b/tests/cluster/poc_test.go
@@ -0,0 +1,47 @@
+package cluster
+
+// poc_test.go contains proof of concept tests for the byte-range locking logic.
+// This goes directly to an underlying filesystem without going through gocryptfs.
+
+import (
+	"syscall"
+	"testing"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/rfjakob/gocryptfs/v2/tests/test_helpers"
+)
+
+// Check that byte-range locks work on an empty file
+func TestPoCFcntlFlock(t *testing.T) {
+	path := test_helpers.TmpDir + "/" + t.Name()
+
+	fd1, err := syscall.Open(path, syscall.O_CREAT|syscall.O_WRONLY|syscall.O_EXCL, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer syscall.Close(fd1)
+
+	// F_OFD_SETLK locks on the same fd always succeed, so we have to
+	// open a 2nd time.
+	fd2, err := syscall.Open(path, syscall.O_RDWR, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer syscall.Close(fd2)
+
+	lk := unix.Flock_t{
+		Type:   unix.F_WRLCK,
+		Whence: unix.SEEK_SET,
+		Start:  0,
+		Len:    0,
+	}
+	err = unix.FcntlFlock(uintptr(fd1), unix.F_OFD_SETLK, &lk)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = unix.FcntlFlock(uintptr(fd2), unix.F_OFD_SETLK, &lk)
+	if err == nil {
+		t.Fatal("double-lock succeeded but should have failed")
+	}
+}