runsc: Support job control signals for the root container.

Now containers run with "docker run -it" support control characters like ^C and
^Z.

This required refactoring our signal handling a bit. Signals delivered to the
"runsc boot" process are turned into loader.Signal calls with the appropriate
delivery mode. Previously they were always sent directly to PID 1.

PiperOrigin-RevId: 217566770
Change-Id: I5b7220d9a0f2b591a56335479454a200c6de8732

1 files changed, 452 insertions, 0 deletions

diff --git a/runsc/container/console_test.go b/runsc/container/console_test.go
new file mode 100644
index 000000000..82adcbb7d
--- /dev/null
+++ b/runsc/container/console_test.go
@@ -0,0 +1,452 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package container
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/kr/pty"
+	"golang.org/x/sys/unix"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/control"
+	"gvisor.googlesource.com/gvisor/pkg/unet"
+	"gvisor.googlesource.com/gvisor/pkg/urpc"
+	"gvisor.googlesource.com/gvisor/runsc/test/testutil"
+)
+
+// createConsoleSocket creates a socket that will receive a console fd from the
+// sandbox. If no error occurs, it returns the server socket and a cleanup
+// function.
+func createConsoleSocket(socketPath string) (*unet.ServerSocket, func() error, error) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return nil, nil, fmt.Errorf("error getting cwd: %v", err)
+	}
+	// We use a relative path to avoid overflowing the unix path length
+	// limit (108 chars).
+	socketRelPath, err := filepath.Rel(cwd, socketPath)
+	if err != nil {
+		return nil, nil, fmt.Errorf("error getting relative path for %q from cwd %q: %v", socketPath, cwd, err)
+	}
+	if len(socketRelPath) > len(socketPath) {
+		socketRelPath = socketPath
+	}
+	srv, err := unet.BindAndListen(socketRelPath, false)
+	if err != nil {
+		return nil, nil, fmt.Errorf("error binding and listening to socket %q: %v", socketPath, err)
+	}
+
+	cleanup := func() error {
+		if err := srv.Close(); err != nil {
+			return fmt.Errorf("error closing socket %q: %v", socketRelPath, err)
+		}
+		if err := os.Remove(socketPath); err != nil {
+			return fmt.Errorf("error removing socket %q: %v", socketRelPath, err)
+		}
+		return nil
+	}
+
+	return srv, cleanup, nil
+}
+
+// receiveConsolePTY accepts a connection on the server socket and reads fds.
+// It fails if more than one FD is received, or if the FD is not a PTY. It
+// returns the PTY master file.
+func receiveConsolePTY(srv *unet.ServerSocket) (*os.File, error) {
+	sock, err := srv.Accept()
+	if err != nil {
+		return nil, fmt.Errorf("error accepting socket connection: %v", err)
+	}
+
+	// Allow 3 fds to be received.  We only expect 1.
+	r := sock.Reader(true /* blocking */)
+	r.EnableFDs(1)
+
+	// The socket is closed right after sending the FD, so EOF is
+	// an allowed error.
+	b := [][]byte{{}}
+	if _, err := r.ReadVec(b); err != nil && err != io.EOF {
+		return nil, fmt.Errorf("error reading from socket connection: %v", err)
+	}
+
+	// We should have gotten a control message.
+	fds, err := r.ExtractFDs()
+	if err != nil {
+		return nil, fmt.Errorf("error extracting fds from socket connection: %v", err)
+	}
+	if len(fds) != 1 {
+		return nil, fmt.Errorf("got %d fds from socket, wanted 1", len(fds))
+	}
+
+	// Verify that the fd is a terminal.
+	if _, err := unix.IoctlGetTermios(fds[0], unix.TCGETS); err != nil {
+		return nil, fmt.Errorf("fd is not a terminal (ioctl TGGETS got %v)", err)
+	}
+
+	return os.NewFile(uintptr(fds[0]), "pty_master"), nil
+}
+
+// Test that an pty FD is sent over the console socket if one is provided.
+func TestConsoleSocket(t *testing.T) {
+	for _, conf := range configs(all...) {
+		t.Logf("Running test with conf: %+v", conf)
+		spec := testutil.NewSpecWithArgs("true")
+		rootDir, bundleDir, err := testutil.SetupContainer(spec, conf)
+		if err != nil {
+			t.Fatalf("error setting up container: %v", err)
+		}
+		defer os.RemoveAll(rootDir)
+		defer os.RemoveAll(bundleDir)
+
+		socketPath := filepath.Join(bundleDir, "socket")
+		srv, cleanup, err := createConsoleSocket(socketPath)
+		if err != nil {
+			t.Fatalf("error creating socket at %q: %v", socketPath, err)
+		}
+		defer cleanup()
+
+		// Create the container and pass the socket name.
+		id := testutil.UniqueContainerID()
+		c, err := Create(id, spec, conf, bundleDir, socketPath, "", "")
+		if err != nil {
+			t.Fatalf("error creating container: %v", err)
+		}
+		defer c.Destroy()
+
+		// Make sure we get a console PTY.
+		ptyMaster, err := receiveConsolePTY(srv)
+		if err != nil {
+			t.Fatalf("error receiving console FD: %v", err)
+		}
+		ptyMaster.Close()
+	}
+}
+
+// Test that job control signals work on a console created with "exec -ti".
+func TestJobControlSignalExec(t *testing.T) {
+	spec := testutil.NewSpecWithArgs("/bin/sleep", "10000")
+	conf := testutil.TestConfig()
+
+	rootDir, bundleDir, err := testutil.SetupContainer(spec, conf)
+	if err != nil {
+		t.Fatalf("error setting up container: %v", err)
+	}
+	defer os.RemoveAll(rootDir)
+	defer os.RemoveAll(bundleDir)
+
+	// Create and start the container.
+	c, err := Create(testutil.UniqueContainerID(), spec, conf, bundleDir, "", "", "")
+	if err != nil {
+		t.Fatalf("error creating container: %v", err)
+	}
+	defer c.Destroy()
+	if err := c.Start(conf); err != nil {
+		t.Fatalf("error starting container: %v", err)
+	}
+
+	// Create a pty master/slave. The slave will be passed to the exec
+	// process.
+	ptyMaster, ptySlave, err := pty.Open()
+	if err != nil {
+		t.Fatalf("error opening pty: %v", err)
+	}
+	defer ptyMaster.Close()
+	defer ptySlave.Close()
+
+	// Exec bash and attach a terminal.
+	args := &control.ExecArgs{
+		Filename: "/bin/bash",
+		// Don't let bash execute from profile or rc files, otherwise
+		// our PID counts get messed up.
+		Argv: []string{"/bin/bash", "--noprofile", "--norc"},
+		// Pass the pty slave as FD 0, 1, and 2.
+		FilePayload: urpc.FilePayload{
+			Files: []*os.File{ptySlave, ptySlave, ptySlave},
+		},
+		StdioIsPty: true,
+	}
+
+	pid, err := c.Execute(args)
+	if err != nil {
+		t.Fatalf("error executing: %v", err)
+	}
+	if pid != 2 {
+		t.Fatalf("exec got pid %d, wanted %d", pid, 2)
+	}
+
+	// Make sure all the processes are running.
+	expectedPL := []*control.Process{
+		// Root container process.
+		{PID: 1, Cmd: "sleep"},
+		// Bash from exec process.
+		{PID: 2, Cmd: "bash"},
+	}
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Error(err)
+	}
+
+	// Execute sleep.
+	ptyMaster.Write([]byte("sleep 100\n"))
+
+	// Wait for it to start. Sleep's PPID is bash's PID.
+	expectedPL = append(expectedPL, &control.Process{PID: 3, PPID: 2, Cmd: "sleep"})
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Error(err)
+	}
+
+	// Send a SIGTERM to the foreground process for the exec PID. Note that
+	// although we pass in the PID of "bash", it should actually terminate
+	// "sleep", since that is the foreground process.
+	if err := c.Sandbox.SignalProcess(c.ID, pid, syscall.SIGTERM, true /* fgProcess */); err != nil {
+		t.Fatalf("error signaling container: %v", err)
+	}
+
+	// Sleep process should be gone.
+	expectedPL = expectedPL[:len(expectedPL)-1]
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Error(err)
+	}
+
+	// Sleep is dead, but it may take more time for bash to notice and
+	// change the foreground process back to itself. We know it is done
+	// when bash writes "Terminated" to the pty.
+	if err := testutil.WaitUntilRead(ptyMaster, "Terminated", nil, 5*time.Second); err != nil {
+		t.Fatalf("bash did not take over pty: %v", err)
+	}
+
+	// Send a SIGKILL to the foreground process again. This time "bash"
+	// should be killed. We use SIGKILL instead of SIGTERM or SIGINT
+	// because bash ignores those.
+	if err := c.Sandbox.SignalProcess(c.ID, pid, syscall.SIGKILL, true /* fgProcess */); err != nil {
+		t.Fatalf("error signaling container: %v", err)
+	}
+	expectedPL = expectedPL[:1]
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Error(err)
+	}
+
+	// Make sure the process indicates it was killed by a SIGKILL.
+	ws, err := c.WaitPID(pid, true)
+	if err != nil {
+		t.Errorf("waiting on container failed: %v", err)
+	}
+	if !ws.Signaled() {
+		t.Error("ws.Signaled() got false, want true")
+	}
+	if got, want := ws.Signal(), syscall.SIGKILL; got != want {
+		t.Errorf("ws.Signal() got %v, want %v", got, want)
+	}
+}
+
+// Test that job control signals work on a console created with "run -ti".
+func TestJobControlSignalRootContainer(t *testing.T) {
+	conf := testutil.TestConfig()
+	// Don't let bash execute from profile or rc files, otherwise our PID
+	// counts get messed up.
+	spec := testutil.NewSpecWithArgs("/bin/bash", "--noprofile", "--norc")
+	spec.Process.Terminal = true
+
+	rootDir, bundleDir, err := testutil.SetupContainer(spec, conf)
+	if err != nil {
+		t.Fatalf("error setting up container: %v", err)
+	}
+	defer os.RemoveAll(rootDir)
+	defer os.RemoveAll(bundleDir)
+
+	socketPath := filepath.Join(bundleDir, "socket")
+	srv, cleanup, err := createConsoleSocket(socketPath)
+	if err != nil {
+		t.Fatalf("error creating socket at %q: %v", socketPath, err)
+	}
+	defer cleanup()
+
+	// Create the container and pass the socket name.
+	id := testutil.UniqueContainerID()
+	c, err := Create(id, spec, conf, bundleDir, socketPath, "", "")
+	if err != nil {
+		t.Fatalf("error creating container: %v", err)
+	}
+	defer c.Destroy()
+
+	// Get the PTY master.
+	ptyMaster, err := receiveConsolePTY(srv)
+	if err != nil {
+		t.Fatalf("error receiving console FD: %v", err)
+	}
+	defer ptyMaster.Close()
+
+	// Bash output as well as sandbox output will be written to the PTY
+	// file. Writes after a certain point will block unless we drain the
+	// PTY, so we must continually copy from it.
+	//
+	// We log the output to stdout for debugabilitly, and also to a buffer,
+	// since we wait on particular output from bash below. We use a custom
+	// blockingBuffer which is thread-safe and also blocks on Read calls,
+	// which makes this a suitable Reader for WaitUntilRead.
+	ptyBuf := newBlockingBuffer()
+	tee := io.TeeReader(ptyMaster, ptyBuf)
+	go io.Copy(os.Stdout, tee)
+
+	// Start the container.
+	if err := c.Start(conf); err != nil {
+		t.Fatalf("error starting container: %v", err)
+	}
+
+	// Start waiting for the container to exit in a goroutine. We do this
+	// very early, otherwise it might exit before we have a chance to call
+	// Wait.
+	var (
+		ws syscall.WaitStatus
+		wg sync.WaitGroup
+	)
+	wg.Add(1)
+	go func() {
+		var err error
+		ws, err = c.Wait()
+		if err != nil {
+			t.Errorf("error waiting on container: %v", err)
+		}
+		wg.Done()
+	}()
+
+	// Wait for bash to start.
+	expectedPL := []*control.Process{
+		{PID: 1, Cmd: "bash"},
+	}
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Fatal(err)
+	}
+
+	// Execute sleep via the terminal.
+	ptyMaster.Write([]byte("sleep 100\n"))
+
+	// Wait for sleep to start.
+	expectedPL = append(expectedPL, &control.Process{PID: 2, PPID: 1, Cmd: "sleep"})
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Fatal(err)
+	}
+
+	// Reset the pty buffer, so there is less output for us to scan later.
+	ptyBuf.Reset()
+
+	// Send a SIGTERM to the foreground process. We pass PID=0, indicating
+	// that the root process should be killed. However, by setting
+	// fgProcess=true, the signal should actually be sent to sleep.
+	if err := c.Sandbox.SignalProcess(c.ID, 0 /* PID */, syscall.SIGTERM, true /* fgProcess */); err != nil {
+		t.Fatalf("error signaling container: %v", err)
+	}
+
+	// Sleep process should be gone.
+	expectedPL = expectedPL[:len(expectedPL)-1]
+	if err := waitForProcessList(c, expectedPL); err != nil {
+		t.Error(err)
+	}
+
+	// Sleep is dead, but it may take more time for bash to notice and
+	// change the foreground process back to itself. We know it is done
+	// when bash writes "Terminated" to the pty.
+	if err := testutil.WaitUntilRead(ptyBuf, "Terminated", nil, 5*time.Second); err != nil {
+		t.Fatalf("bash did not take over pty: %v", err)
+	}
+
+	// Send a SIGKILL to the foreground process again. This time "bash"
+	// should be killed. We use SIGKILL instead of SIGTERM or SIGINT
+	// because bash ignores those.
+	if err := c.Sandbox.SignalProcess(c.ID, 0 /* PID */, syscall.SIGKILL, true /* fgProcess */); err != nil {
+		t.Fatalf("error signaling container: %v", err)
+	}
+
+	// Wait for the sandbox to exit. It should exit with a SIGKILL status.
+	wg.Wait()
+	if !ws.Signaled() {
+		t.Error("ws.Signaled() got false, want true")
+	}
+	if got, want := ws.Signal(), syscall.SIGKILL; got != want {
+		t.Errorf("ws.Signal() got %v, want %v", got, want)
+	}
+}
+
+// blockingBuffer is a thread-safe buffer that blocks when reading if the
+// buffer is empty.  It implements io.ReadWriter.
+type blockingBuffer struct {
+	// A send to readCh indicates that a previously empty buffer now has
+	// data for reading.
+	readCh chan struct{}
+
+	// mu protects buf.
+	mu  sync.Mutex
+	buf bytes.Buffer
+}
+
+func newBlockingBuffer() *blockingBuffer {
+	return &blockingBuffer{
+		readCh: make(chan struct{}, 1),
+	}
+}
+
+// Write implements Writer.Write.
+func (bb *blockingBuffer) Write(p []byte) (int, error) {
+	bb.mu.Lock()
+	defer bb.mu.Unlock()
+	l := bb.buf.Len()
+	n, err := bb.buf.Write(p)
+	if l == 0 && n > 0 {
+		// New data!
+		bb.readCh <- struct{}{}
+	}
+	return n, err
+}
+
+// Read implements Reader.Read. It will block until data is available.
+func (bb *blockingBuffer) Read(p []byte) (int, error) {
+	for {
+		bb.mu.Lock()
+		n, err := bb.buf.Read(p)
+		if n > 0 || err != io.EOF {
+			if bb.buf.Len() == 0 {
+				// Reset the readCh.
+				select {
+				case <-bb.readCh:
+				default:
+				}
+			}
+			bb.mu.Unlock()
+			return n, err
+		}
+		bb.mu.Unlock()
+
+		// Wait for new data.
+		<-bb.readCh
+	}
+}
+
+// Reset resets the buffer.
+func (bb *blockingBuffer) Reset() {
+	bb.mu.Lock()
+	defer bb.mu.Unlock()
+	bb.buf.Reset()
+	// Reset the readCh.
+	select {
+	case <-bb.readCh:
+	default:
+	}
+}