container/params: pass fd instead of file

The file is very difficult to stub. Pass fd instead as it is the value that is actually useful.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/dispatcher.go

@@ -45,7 +45,7 @@ type syscallDispatcher interface {
 	// isatty provides [Isatty].
 	isatty(fd int) bool
 	// receive provides [Receive].
-	receive(key string, e any, v **os.File) (closeFunc func() error, err error)
+	receive(key string, e any, fdp *uintptr) (closeFunc func() error, err error)
 
 	// bindMount provides procPaths.bindMount.
 	bindMount(source, target string, flags uintptr, eq bool) error
@@ -152,8 +152,8 @@ func (direct) capBoundingSetDrop(cap uintptr) error            { return capBound
 func (direct) capAmbientClearAll() error                       { return capAmbientClearAll() }
 func (direct) capAmbientRaise(cap uintptr) error               { return capAmbientRaise(cap) }
 func (direct) isatty(fd int) bool                              { return Isatty(fd) }
-func (direct) receive(key string, e any, v **os.File) (func() error, error) {
-	return Receive(key, e, v)
+func (direct) receive(key string, e any, fdp *uintptr) (func() error, error) {
+	return Receive(key, e, fdp)
 }
 
 func (direct) bindMount(source, target string, flags uintptr, eq bool) error {

container/dispatcher_test.go

@@ -356,12 +356,12 @@ func (k *kstub) isatty(fd int) bool {
 	return expect.ret.(bool)
 }
 
-func (k *kstub) receive(key string, e any, v **os.File) (closeFunc func() error, err error) {
+func (k *kstub) receive(key string, e any, fdp *uintptr) (closeFunc func() error, err error) {
 	expect := k.expect("receive")
 	return expect.ret.(func() error), expect.error(
 		checkArg(k, "key", key, 0),
 		checkArgReflect(k, "e", e, 1),
-		checkArg(k, "v", v, 2))
+		checkArg(k, "fdp", fdp, 2))
 }
 
 func (k *kstub) bindMount(source, target string, flags uintptr, eq bool) error {

container/init.go

@@ -99,10 +99,10 @@ func initEntrypoint(k syscallDispatcher, prepareLogger func(prefix string), setV
 	var (
 		params      initParams
 		closeSetup  func() error
-		setupFile   *os.File
+		setupFd     uintptr
 		offsetSetup int
 	)
-	if f, err := k.receive(setupEnv, &params, &setupFile); err != nil {
+	if f, err := k.receive(setupEnv, &params, &setupFd); err != nil {
 		if errors.Is(err, EBADF) {
 			k.fatal("invalid setup descriptor")
 		}
@@ -122,7 +122,7 @@ func initEntrypoint(k syscallDispatcher, prepareLogger func(prefix string), setV
 		setVerbose(params.Verbose)
 		k.verbose("received setup parameters")
 		closeSetup = f
-		offsetSetup = int(setupFile.Fd() + 1)
+		offsetSetup = int(setupFd + 1)
 	}
 
 	// write uid/gid map here so parent does not need to set dumpable

container/params.go

@@ -25,7 +25,7 @@ func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
 }
 
 // Receive retrieves setup fd from the environment and receives params.
-func Receive(key string, e any, v **os.File) (func() error, error) {
+func Receive(key string, e any, fdp *uintptr) (func() error, error) {
 	var setup *os.File
 
 	if s, ok := os.LookupEnv(key); !ok {
@@ -38,8 +38,8 @@ func Receive(key string, e any, v **os.File) (func() error, error) {
 			if setup == nil {
 				return nil, syscall.EBADF
 			}
-			if v != nil {
-				*v = setup
+			if fdp != nil {
+				*fdp = setup.Fd()
 			}
 		}
 	}

container/params_test.go

@@ -53,7 +53,7 @@ func TestSetupReceive(t *testing.T) {
 	})
 
 	t.Run("setup receive", func(t *testing.T) {
-		check := func(t *testing.T, useNilFp bool) {
+		check := func(t *testing.T, useNilFdp bool) {
 			const key = "TEST_SETUP_RECEIVE"
 			payload := []int{syscall.MS_MGC_VAL, syscall.MS_MGC_MSK, syscall.MS_ASYNC, syscall.MS_ACTIVE}
 
@@ -82,13 +82,13 @@ func TestSetupReceive(t *testing.T) {
 
 			var (
 				gotPayload []int
-				fp         **os.File
+				fdp        *uintptr
 			)
-			if !useNilFp {
-				fp = new(*os.File)
+			if !useNilFdp {
+				fdp = new(uintptr)
 			}
 			var closeFile func() error
-			if f, err := container.Receive(key, &gotPayload, fp); err != nil {
+			if f, err := container.Receive(key, &gotPayload, fdp); err != nil {
 				t.Fatalf("Receive: error = %v", err)
 			} else {
 				closeFile = f
@@ -97,12 +97,9 @@ func TestSetupReceive(t *testing.T) {
 					t.Errorf("Receive: %#v, want %#v", gotPayload, payload)
 				}
 			}
-			if !useNilFp {
-				if name := (*fp).Name(); name != "setup" {
-					t.Errorf("Name: %s, want setup", name)
-				}
-				if fd := int((*fp).Fd()); fd != dupFd {
-					t.Errorf("Fd: %d, want %d", fd, dupFd)
+			if !useNilFdp {
+				if int(*fdp) != dupFd {
+					t.Errorf("Fd: %d, want %d", *fdp, dupFd)
 				}
 			}