internal/app: modularise outcome finalise

This is the initial effort of splitting up host and container side of finalisation for params to shim. The new layout also enables much finer grained unit testing of each step, as well as partition access to per-app state for each step.

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

internal/app/process.go

@@ -41,6 +41,7 @@ type mainState struct {
 	k *outcome
 	container.Msg
 	uintptr
+	*finaliseProcess
 }
 
 const (
@@ -78,15 +79,9 @@ func (ms mainState) beforeExit(isFault bool) {
 	// this also handles wait for a non-fault termination
 	if ms.cmd != nil && ms.cmdWait != nil {
 		waitDone := make(chan struct{})
-		// TODO(ophestra): enforce this limit early so it does not have to be done twice
-		shimTimeoutCompensated := shimWaitTimeout
-		if ms.k.waitDelay > MaxShimWaitDelay {
-			shimTimeoutCompensated += MaxShimWaitDelay
-		} else {
-			shimTimeoutCompensated += ms.k.waitDelay
-		}
+
 		// this ties waitDone to ctx with the additional compensated timeout duration
-		go func() { <-ms.k.ctx.Done(); time.Sleep(shimTimeoutCompensated); close(waitDone) }()
+		go func() { <-ms.k.ctx.Done(); time.Sleep(ms.waitDelay); close(waitDone) }()
 
 		select {
 		case err := <-ms.cmdWait:
@@ -137,9 +132,9 @@ func (ms mainState) beforeExit(isFault bool) {
 	}
 
 	if ms.uintptr&mainNeedsRevert != 0 {
-		if ok, err := ms.store.Do(ms.k.user.identity.unwrap(), func(c state.Cursor) {
+		if ok, err := ms.store.Do(ms.identity.unwrap(), func(c state.Cursor) {
 			if ms.uintptr&mainNeedsDestroy != 0 {
-				if err := c.Destroy(ms.k.id.unwrap()); err != nil {
+				if err := c.Destroy(ms.id.unwrap()); err != nil {
 					perror(err, "destroy state entry")
 				}
 			}
@@ -216,23 +211,45 @@ func (ms mainState) fatal(fallback string, ferr error) {
 	os.Exit(1)
 }
 
+// finaliseProcess contains information collected during outcome.finalise used in outcome.main.
+type finaliseProcess struct {
+	// Supplementary group ids.
+	supp []string
+
+	// Copied from [hst.ContainerConfig], without exceeding [MaxShimWaitDelay].
+	waitDelay time.Duration
+
+	// Copied from the RunDirPath field of [hst.Paths].
+	runDirPath *container.Absolute
+
+	// Copied from outcomeState.
+	identity *stringPair[int]
+
+	// Copied from outcomeState.
+	id *stringPair[state.ID]
+}
+
 // main carries out outcome and terminates. main does not return.
 func (k *outcome) main(msg container.Msg) {
 	if !k.active.CompareAndSwap(false, true) {
 		panic("outcome: attempted to run twice")
 	}
 
+	if k.proc == nil {
+		panic("outcome: did not finalise")
+	}
+
 	// read comp value early for early failure
 	hsuPath := internal.MustHsuPath()
 
 	// ms.beforeExit required beyond this point
-	ms := &mainState{Msg: msg, k: k}
+	ms := &mainState{Msg: msg, k: k, finaliseProcess: k.proc}
 
 	if err := k.sys.Commit(); err != nil {
 		ms.fatal("cannot commit system setup:", err)
 	}
 	ms.uintptr |= mainNeedsRevert
-	ms.store = state.NewMulti(msg, k.runDirPath.String())
+	ms.store = state.NewMulti(msg, ms.runDirPath.String())
 
 	ctx, cancel := context.WithCancel(k.ctx)
 	defer cancel()
@@ -253,14 +270,14 @@ func (k *outcome) main(msg container.Msg) {
 			// passed through to shim by hsu
 			shimEnv + "=" + strconv.Itoa(fd),
 			// interpreted by hsu
-			"HAKUREI_IDENTITY=" + k.user.identity.String(),
+			"HAKUREI_IDENTITY=" + ms.identity.String(),
 		}
 	}
 
-	if len(k.user.supp) > 0 {
-		msg.Verbosef("attaching supplementary group ids %s", k.user.supp)
+	if len(ms.supp) > 0 {
+		msg.Verbosef("attaching supplementary group ids %s", ms.supp)
 		// interpreted by hsu
-		ms.cmd.Env = append(ms.cmd.Env, "HAKUREI_GROUPS="+strings.Join(k.user.supp, " "))
+		ms.cmd.Env = append(ms.cmd.Env, "HAKUREI_GROUPS="+strings.Join(ms.supp, " "))
 	}
 
 	msg.Verbosef("setuid helper at %s", hsuPath)
@@ -282,8 +299,8 @@ func (k *outcome) main(msg container.Msg) {
 		go func() {
 			setupErr <- e.Encode(&shimParams{
 				os.Getpid(),
-				k.waitDelay,
-				k.container,
+				ms.waitDelay,
+				&k.container,
 				msg.IsVerbose(),
 			})
 		}()
@@ -300,9 +317,9 @@ func (k *outcome) main(msg container.Msg) {
 	}
 
 	// shim accepted setup payload, create process state
-	if ok, err := ms.store.Do(k.user.identity.unwrap(), func(c state.Cursor) {
+	if ok, err := ms.store.Do(ms.identity.unwrap(), func(c state.Cursor) {
 		if err := c.Save(&state.State{
-			ID:   k.id.unwrap(),
+			ID:   ms.id.unwrap(),
 			PID:  ms.cmd.Process.Pid,
 			Time: *ms.Time,
 		}, k.ct); err != nil {