Shutdown host sockets on internal shutdown

This is required to make the shutdown visible to peers outside the
sandbox.

The readClosed / writeClosed fields were dropped, as they were
preventing a shutdown socket from reading the remainder of queued bytes.
The host syscalls will return the appropriate errors for shutdown.

The control message tests have been split out of socket_unix.cc to make
the (few) remaining tests accessible to testing inherited host UDS,
which don't support sending control messages.

Updates #273

PiperOrigin-RevId: 251763060

2 files changed, 28 insertions, 190 deletions

diff --git a/pkg/sentry/fs/host/socket.go b/pkg/sentry/fs/host/socket.go
index 3ed137006..e4ec0f62c 100644
--- a/pkg/sentry/fs/host/socket.go
+++ b/pkg/sentry/fs/host/socket.go
@@ -15,6 +15,7 @@
 package host
 
 import (
+	"fmt"
 	"sync"
 	"syscall"
 
@@ -51,20 +52,6 @@ type ConnectedEndpoint struct {
 	// ref keeps track of references to a connectedEndpoint.
 	ref refs.AtomicRefCount
 
-	// mu protects fd, readClosed and writeClosed.
-	mu sync.RWMutex `state:"nosave"`
-
-	// file is an *fd.FD containing the FD backing this endpoint. It must be
-	// set to nil if it has been closed.
-	file *fd.FD `state:"nosave"`
-
-	// readClosed is true if the FD has read shutdown or if it has been closed.
-	readClosed bool
-
-	// writeClosed is true if the FD has write shutdown or if it has been
-	// closed.
-	writeClosed bool
-
 	// If srfd >= 0, it is the host FD that file was imported from.
 	srfd int `state:"wait"`
 
@@ -78,6 +65,13 @@ type ConnectedEndpoint struct {
 	// prevent lots of small messages from filling the real send buffer
 	// size on the host.
 	sndbuf int `state:"nosave"`
+
+	// mu protects the fields below.
+	mu sync.RWMutex `state:"nosave"`
+
+	// file is an *fd.FD containing the FD backing this endpoint. It must be
+	// set to nil if it has been closed.
+	file *fd.FD `state:"nosave"`
 }
 
 // init performs initialization required for creating new ConnectedEndpoints and
@@ -208,9 +202,6 @@ func newSocket(ctx context.Context, orgfd int, saveable bool) (*fs.File, error)
 func (c *ConnectedEndpoint) Send(data [][]byte, controlMessages transport.ControlMessages, from tcpip.FullAddress) (uintptr, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return 0, false, syserr.ErrClosedForSend
-	}
 
 	if !controlMessages.Empty() {
 		return 0, false, syserr.ErrInvalidEndpointState
@@ -244,8 +235,13 @@ func (c *ConnectedEndpoint) SendNotify() {}
 // CloseSend implements transport.ConnectedEndpoint.CloseSend.
 func (c *ConnectedEndpoint) CloseSend() {
 	c.mu.Lock()
-	c.writeClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_WR); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed write shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // CloseNotify implements transport.ConnectedEndpoint.CloseNotify.
@@ -255,9 +251,7 @@ func (c *ConnectedEndpoint) CloseNotify() {}
 func (c *ConnectedEndpoint) Writable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventOut)&waiter.EventOut != 0
 }
 
@@ -285,9 +279,6 @@ func (c *ConnectedEndpoint) EventUpdate() {
 func (c *ConnectedEndpoint) Recv(data [][]byte, creds bool, numRights uintptr, peek bool) (uintptr, uintptr, transport.ControlMessages, bool, tcpip.FullAddress, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return 0, 0, transport.ControlMessages{}, false, tcpip.FullAddress{}, false, syserr.ErrClosedForReceive
-	}
 
 	var cm unet.ControlMessage
 	if numRights > 0 {
@@ -344,31 +335,34 @@ func (c *ConnectedEndpoint) RecvNotify() {}
 // CloseRecv implements transport.Receiver.CloseRecv.
 func (c *ConnectedEndpoint) CloseRecv() {
 	c.mu.Lock()
-	c.readClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_RD); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed read shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // Readable implements transport.Receiver.Readable.
 func (c *ConnectedEndpoint) Readable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventIn)&waiter.EventIn != 0
 }
 
 // SendQueuedSize implements transport.Receiver.SendQueuedSize.
 func (c *ConnectedEndpoint) SendQueuedSize() int64 {
-	// SendQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): SendQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
 // RecvQueuedSize implements transport.Receiver.RecvQueuedSize.
 func (c *ConnectedEndpoint) RecvQueuedSize() int64 {
-	// RecvQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): RecvQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
diff --git a/pkg/sentry/fs/host/socket_test.go b/pkg/sentry/fs/host/socket_test.go
index 06392a65a..bc3ce5627 100644
--- a/pkg/sentry/fs/host/socket_test.go
+++ b/pkg/sentry/fs/host/socket_test.go
@@ -198,20 +198,6 @@ func TestListen(t *testing.T) {
 	}
 }
 
-func TestSend(t *testing.T) {
-	e := ConnectedEndpoint{writeClosed: true}
-	if _, _, err := e.Send(nil, transport.ControlMessages{}, tcpip.FullAddress{}); err != syserr.ErrClosedForSend {
-		t.Errorf("Got %#v.Send() = %v, want = %v", e, err, syserr.ErrClosedForSend)
-	}
-}
-
-func TestRecv(t *testing.T) {
-	e := ConnectedEndpoint{readClosed: true}
-	if _, _, _, _, _, _, err := e.Recv(nil, false, 0, false); err != syserr.ErrClosedForReceive {
-		t.Errorf("Got %#v.Recv() = %v, want = %v", e, err, syserr.ErrClosedForReceive)
-	}
-}
-
 func TestPasscred(t *testing.T) {
 	e := ConnectedEndpoint{}
 	if got, want := e.Passcred(), false; got != want {
@@ -244,20 +230,6 @@ func TestQueuedSize(t *testing.T) {
 	}
 }
 
-func TestReadable(t *testing.T) {
-	e := ConnectedEndpoint{readClosed: true}
-	if got, want := e.Readable(), true; got != want {
-		t.Errorf("Got %#v.Readable() = %t, want = %t", e, got, want)
-	}
-}
-
-func TestWritable(t *testing.T) {
-	e := ConnectedEndpoint{writeClosed: true}
-	if got, want := e.Writable(), true; got != want {
-		t.Errorf("Got %#v.Writable() = %t, want = %t", e, got, want)
-	}
-}
-
 func TestRelease(t *testing.T) {
 	f, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
@@ -272,131 +244,3 @@ func TestRelease(t *testing.T) {
 		t.Errorf("got = %#v, want = %#v", c, want)
 	}
 }
-
-func TestClose(t *testing.T) {
-	type testCase struct {
-		name  string
-		cep   *ConnectedEndpoint
-		addFD bool
-		f     func()
-		want  *ConnectedEndpoint
-	}
-
-	var tests []testCase
-
-	// nil is the value used by ConnectedEndpoint to indicate a closed file.
-	// Non-nil files are used to check if the file gets closed.
-
-	f, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c := &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f)}
-	tests = append(tests, testCase{
-		name:  "First CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true}
-	tests = append(tests, testCase{
-		name:  "Second CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f)}
-	tests = append(tests, testCase{
-		name:  "First CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Second CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "CloseSend then CloseRecv",
-		cep:   c,
-		addFD: true,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true}
-	tests = append(tests, testCase{
-		name:  "CloseRecv then CloseSend",
-		cep:   c,
-		addFD: true,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true, writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Full close then CloseRecv",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseRecv,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	f, err = syscall.Socket(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
-	if err != nil {
-		t.Fatal("Creating socket:", err)
-	}
-	c = &ConnectedEndpoint{queue: &waiter.Queue{}, file: fd.New(f), readClosed: true, writeClosed: true}
-	tests = append(tests, testCase{
-		name:  "Full close then CloseSend",
-		cep:   c,
-		addFD: false,
-		f:     c.CloseSend,
-		want:  &ConnectedEndpoint{queue: c.queue, file: c.file, readClosed: true, writeClosed: true},
-	})
-
-	for _, test := range tests {
-		if test.addFD {
-			fdnotifier.AddFD(int32(test.cep.file.FD()), nil)
-		}
-		if test.f(); !reflect.DeepEqual(test.cep, test.want) {
-			t.Errorf("%s: got = %#v, want = %#v", test.name, test.cep, test.want)
-		}
-	}
-}