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{
-			p.Params,
-			Getuid(),
-			Getgid(),
-			len(p.ExtraFiles),
-			p.msg.IsVerbose(),
-		},
-	)
+	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)