hst: configurable wait delay

This is useful for programs that take a long time to clean up.

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

cmd/hakurei/print_test.go

@@ -256,7 +256,7 @@ App
     ],
     "container": {
       "hostname": "localhost",
-      "immediate_termination": true,
+      "wait_delay": -1,
       "seccomp_flags": 1,
       "seccomp_presets": 1,
       "seccomp_compat": true,
@@ -384,7 +384,7 @@ App
   ],
   "container": {
     "hostname": "localhost",
-    "immediate_termination": true,
+    "wait_delay": -1,
     "seccomp_flags": 1,
     "seccomp_presets": 1,
     "seccomp_compat": true,
@@ -566,7 +566,7 @@ func Test_printPs(t *testing.T) {
       ],
       "container": {
         "hostname": "localhost",
-        "immediate_termination": true,
+        "wait_delay": -1,
         "seccomp_flags": 1,
         "seccomp_presets": 1,
         "seccomp_compat": true,

hst/container.go

@@ -1,6 +1,8 @@
 package hst
 
 import (
+	"time"
+
 	"hakurei.app/container/seccomp"
 )
 
@@ -10,8 +12,10 @@ type (
 		// container hostname
 		Hostname string `json:"hostname,omitempty"`
 
-		// do not interrupt and wait for initial process during termination
-		ImmediateTermination bool `json:"immediate_termination,omitempty"`
+		// duration to wait for after interrupting a container's initial process in nanoseconds;
+		// a negative value causes the container to be terminated immediately on cancellation
+		WaitDelay time.Duration `json:"wait_delay,omitempty"`
+
 		// extra seccomp flags
 		SeccompFlags seccomp.ExportFlag `json:"seccomp_flags"`
 		// extra seccomp presets

hst/template.go

@@ -57,18 +57,18 @@ func Template() *Config {
 		Groups:   []string{"video", "dialout", "plugdev"},
 
 		Container: &ContainerConfig{
-			Hostname:             "localhost",
-			Devel:                true,
-			Userns:               true,
-			Net:                  true,
-			Device:               true,
-			ImmediateTermination: true,
-			SeccompFlags:         seccomp.AllowMultiarch,
-			SeccompPresets:       seccomp.PresetExt,
-			SeccompCompat:        true,
-			Tty:                  true,
-			Multiarch:            true,
-			MapRealUID:           true,
+			Hostname:       "localhost",
+			Devel:          true,
+			Userns:         true,
+			Net:            true,
+			Device:         true,
+			WaitDelay:      -1,
+			SeccompFlags:   seccomp.AllowMultiarch,
+			SeccompPresets: seccomp.PresetExt,
+			SeccompCompat:  true,
+			Tty:            true,
+			Multiarch:      true,
+			MapRealUID:     true,
 			// example API credentials pulled from Google Chrome
 			// DO NOT USE THESE IN A REAL BROWSER
 			Env: map[string]string{

hst/template_test.go

@@ -80,7 +80,7 @@ func TestTemplate(t *testing.T) {
 	],
 	"container": {
 		"hostname": "localhost",
-		"immediate_termination": true,
+		"wait_delay": -1,
 		"seccomp_flags": 1,
 		"seccomp_presets": 1,
 		"seccomp_compat": true,

internal/app/container_linux.go

@@ -35,7 +35,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, uid, gid *int) (*contain
 
 		// the container is canceled when shim is requested to exit or receives an interrupt or termination signal;
 		// this behaviour is implemented in the shim
-		ForwardCancel: !s.ImmediateTermination,
+		ForwardCancel: s.WaitDelay >= 0,
 	}
 
 	{

internal/app/process_linux.go

@@ -123,7 +123,15 @@ func (seal *outcome) Run(rs *RunState) error {
 	// this prevents blocking forever on an early failure
 	waitErr, setupErr := make(chan error, 1), make(chan error, 1)
 	go func() { waitErr <- cmd.Wait(); cancel() }()
-	go func() { setupErr <- e.Encode(&shimParams{os.Getpid(), seal.container, seal.user.data, hlog.Load()}) }()
+	go func() {
+		setupErr <- e.Encode(&shimParams{
+			os.Getpid(),
+			seal.waitDelay,
+			seal.container,
+			seal.user.data,
+			hlog.Load(),
+		})
+	}()
 
 	select {
 	case err := <-setupErr:

internal/app/seal_linux.go

@@ -15,6 +15,7 @@ import (
 	"strings"
 	"sync/atomic"
 	"syscall"
+	"time"
 
 	"hakurei.app/container"
 	"hakurei.app/hst"
@@ -79,6 +80,7 @@ type outcome struct {
 	sys  *system.I
 	ctx  context.Context
 
+	waitDelay time.Duration
 	container *container.Params
 	env       map[string]string
 	sync      *os.File
@@ -281,6 +283,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		var uid, gid int
 		var err error
 		seal.container, seal.env, err = newContainer(config.Container, sys, &uid, &gid)
+		seal.waitDelay = config.Container.WaitDelay
 		if err != nil {
 			return hlog.WrapErrSuffix(err,
 				"cannot initialise container configuration:")

internal/app/shim_linux.go

@@ -28,6 +28,10 @@ type shimParams struct {
 	// monitor pid, checked against ppid in signal handler
 	Monitor int
 
+	// duration to wait for after interrupting a container's initial process before the container is killed;
+	// zero value defaults to [DefaultShimWaitDelay], values exceeding [MaxShimWaitDelay] becomes [MaxShimWaitDelay]
+	WaitDelay time.Duration
+
 	// finalised container params
 	Container *container.Params
 	// path to outer home directory
@@ -43,9 +47,8 @@ const (
 	// ShimExitOrphan is returned when the shim is orphaned before monitor delivers a signal.
 	ShimExitOrphan = 3
 
-	// ShimWaitDelay is the duration to wait after interrupting a container's initial process
-	// before the container is fully killed off.
-	ShimWaitDelay = 5 * time.Second
+	DefaultShimWaitDelay = 5 * time.Second
+	MaxShimWaitDelay     = 30 * time.Second
 )
 
 // ShimMain is the main function of the shim process and runs as the unconstrained target user.
@@ -163,7 +166,14 @@ func ShimMain() {
 	z := container.New(ctx, name)
 	z.Params = *params.Container
 	z.Stdin, z.Stdout, z.Stderr = os.Stdin, os.Stdout, os.Stderr
-	z.WaitDelay = ShimWaitDelay
+
+	z.WaitDelay = params.WaitDelay
+	if z.WaitDelay == 0 {
+		z.WaitDelay = DefaultShimWaitDelay
+	}
+	if z.WaitDelay > MaxShimWaitDelay {
+		z.WaitDelay = MaxShimWaitDelay
+	}
 
 	if err := z.Start(); err != nil {
 		hlog.PrintBaseError(err, "cannot start container:")

nixos.nix

@@ -128,7 +128,7 @@ in
 
                     container = {
                       inherit (app)
-                        immediate_termination
+                        wait_delay
                         devel
                         userns
                         net

options.nix

@@ -76,6 +76,7 @@ in
         type =
           let
             inherit (types)
+              int
               ints
               str
               bool
@@ -195,7 +196,16 @@ in
                 '';
               };
 
-              immediate_termination = mkEnableOption "immediate termination of the container on interrupt";
+              wait_delay = mkOption {
+                type = nullOr int;
+                default = null;
+                description = ''
+                  Duration to wait for after interrupting a container's initial process in nanoseconds.
+                  A negative value causes the container to be terminated immediately on cancellation.
+                  Setting this to null defaults to five seconds.
+                '';
+              };
+
               devel = mkEnableOption "debugging-related kernel interfaces";
               userns = mkEnableOption "user namespace creation";
               tty = mkEnableOption "access to the controlling terminal";

test/configuration.nix

@@ -132,7 +132,7 @@
         identity = 1;
         shareUid = true;
         verbose = true;
-        immediate_termination = true;
+        wait_delay = -1;
         share = pkgs.foot;
         packages = [ ];
         command = "foot";