container/params: expose pipe deadline

This allows more graceful handling of unresponsive process.

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

container/container.go

@@ -25,6 +25,9 @@ const (
 	// CancelSignal is the signal expected by container init on context cancel.
 	// A custom [Container.Cancel] function must eventually deliver this signal.
 	CancelSignal = SIGUSR2
+
+	// Timeout from setup pipe creation to when initParams is fully written.
+	initSetupTimeout = 5 * time.Second
 )
 
 type (
@@ -228,7 +231,7 @@ func (p *Container) Start() error {
 	}
 
 	// place setup pipe before user supplied extra files, this is later restored by init
-	if fd, e, err := Setup(&p.cmd.ExtraFiles); err != nil {
+	if fd, e, err := Setup(time.Now().Add(initSetupTimeout), &p.cmd.ExtraFiles); err != nil {
 		return &StartError{true, "set up params stream", err, false, false}
 	} else {
 		p.setup = e
@@ -324,15 +327,13 @@ func (p *Container) Serve() error {
 		p.SeccompRules = make([]seccomp.NativeRule, 0)
 	}
 
-	err := setup.Encode(
-		&initParams{
+	err := setup.Encode(&initParams{
 		p.Params,
 		Getuid(),
 		Getgid(),
 		len(p.ExtraFiles),
 		p.msg.IsVerbose(),
-		},
-	)
+	})
 	if err != nil {
 		p.cancel()
 	}

container/params.go

@@ -6,13 +6,18 @@ import (
 	"os"
 	"strconv"
 	"syscall"
+	"time"
 )
 
 // Setup appends the read end of a pipe for setup params transmission and returns its fd.
-func Setup(extraFiles *[]*os.File) (int, *gob.Encoder, error) {
+func Setup(deadline time.Time, extraFiles *[]*os.File) (int, *gob.Encoder, error) {
 	if r, w, err := os.Pipe(); err != nil {
 		return -1, nil, err
 	} else {
+		if err = w.SetDeadline(deadline); err != nil {
+			return -1, nil, err
+		}
+
 		fd := 3 + len(*extraFiles)
 		*extraFiles = append(*extraFiles, r)
 		return fd, gob.NewEncoder(w), nil

container/params_test.go

@@ -59,7 +59,8 @@ func TestSetupReceive(t *testing.T) {
 
 			encoderDone := make(chan error, 1)
 			extraFiles := make([]*os.File, 0, 1)
-			if fd, encoder, err := container.Setup(&extraFiles); err != nil {
+			deadline, _ := t.Deadline()
+			if fd, encoder, err := container.Setup(deadline, &extraFiles); err != nil {
 				t.Fatalf("Setup: error = %v", err)
 			} else if fd != 3 {
 				t.Fatalf("Setup: fd = %d, want 3", fd)

internal/outcome/process.go

@@ -20,8 +20,12 @@ import (
 	"hakurei.app/system"
 )
 
+const (
 	// Duration to wait for shim to exit on top of container WaitDelay.
-const shimWaitTimeout = 5 * time.Second
+	shimWaitTimeout = 5 * time.Second
+	// Timeout from setup pipe creation to when outcomeState is fully written.
+	shimSetupTimeout = 5 * time.Second
+)
 
 // mainState holds persistent state bound to outcome.main.
 type mainState struct {
@@ -214,7 +218,7 @@ func (k *outcome) main(msg message.Msg) {
 	hsuPath := internal.MustHsuPath()
 
 	// ms.beforeExit required beyond this point
-	ms := &mainState{Msg: msg, k: k}
+	ms := mainState{Msg: msg, k: k}
 
 	if err := k.sys.Commit(); err != nil {
 		ms.fatal("cannot commit system setup:", err)
@@ -232,11 +236,12 @@ func (k *outcome) main(msg message.Msg) {
 	// shim runs in the same session as monitor; see shim.go for behaviour
 	ms.cmd.Cancel = func() error { return ms.cmd.Process.Signal(syscall.SIGCONT) }
 
-	var e *gob.Encoder
-	if fd, encoder, err := container.Setup(&ms.cmd.ExtraFiles); err != nil {
+	var outcomeStateEncoder *gob.Encoder
+	if fd, encoder, err := container.Setup(time.Now().Add(shimSetupTimeout), &ms.cmd.ExtraFiles); err != nil {
 		ms.fatal("cannot create shim setup pipe:", err)
+		panic("unreachable")
 	} else {
-		e = encoder
+		outcomeStateEncoder = encoder
 		ms.cmd.Env = []string{
 			// passed through to shim by hsu
 			shimEnv + "=" + strconv.Itoa(fd),
@@ -262,24 +267,11 @@ func (k *outcome) main(msg message.Msg) {
 	go func() { ms.cmdWait <- ms.cmd.Wait(); cancel() }()
 	ms.Time = &startTime
 
-	// unfortunately the I/O here cannot be directly canceled;
-	// the cancellation path leads to fatal in this case so that is fine
-	select {
-	case err := <-func() (setupErr chan error) {
-		setupErr = make(chan error, 1)
-		go func() { setupErr <- e.Encode(k.state) }()
-		return
-	}():
-		if err != nil {
+	if err := outcomeStateEncoder.Encode(k.state); err != nil {
 		msg.Resume()
 		ms.fatal("cannot transmit shim config:", err)
 	}
 
-	case <-ctx.Done():
-		msg.Resume()
-		ms.fatal("shim context canceled:", newWithMessageError("shim setup canceled", ctx.Err()))
-	}
-
 	// shim accepted setup payload, create process state
 	if ok, err := ms.store.Do(k.state.identity.unwrap(), func(c store.Cursor) {
 		if err := c.Save(&hst.State{