internal/outcome: rename from app

This is less ambiguous, and more accurately describes the purpose of the package.

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

internal/outcome/process.go

@@ -0,0 +1,321 @@
+package outcome
+
+import (
+	"context"
+	"encoding/gob"
+	"errors"
+	"log"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+
+	"hakurei.app/container"
+	"hakurei.app/container/fhs"
+	"hakurei.app/hst"
+	"hakurei.app/internal"
+	"hakurei.app/internal/state"
+	"hakurei.app/message"
+	"hakurei.app/system"
+)
+
+// Duration to wait for shim to exit on top of container WaitDelay.
+const shimWaitTimeout = 5 * time.Second
+
+// mainState holds persistent state bound to outcome.main.
+type mainState struct {
+	// done is whether beforeExit has been called already.
+	done bool
+
+	// Time is the exact point in time where the process was created.
+	// Location must be set to UTC.
+	//
+	// Time is nil if no process was ever created.
+	Time *time.Time
+
+	store   state.Store
+	cancel  context.CancelFunc
+	cmd     *exec.Cmd
+	cmdWait chan error
+
+	k *outcome
+	message.Msg
+	uintptr
+}
+
+const (
+	// mainNeedsRevert indicates the call to Commit has succeeded.
+	mainNeedsRevert uintptr = 1 << iota
+	// mainNeedsDestroy indicates the instance state entry is present in the store.
+	mainNeedsDestroy
+)
+
+// beforeExit must be called immediately before a call to [os.Exit].
+func (ms mainState) beforeExit(isFault bool) {
+	if ms.done {
+		panic("attempting to call beforeExit twice")
+	}
+	ms.done = true
+	defer ms.BeforeExit()
+
+	if isFault && ms.cancel != nil {
+		ms.cancel()
+	}
+
+	var hasErr bool
+	// updates hasErr but does not terminate
+	perror := func(err error, message string) {
+		hasErr = true
+		printMessageError("cannot "+message+":", err)
+	}
+	exitCode := 1
+	defer func() {
+		if hasErr {
+			os.Exit(exitCode)
+		}
+	}()
+
+	// this also handles wait for a non-fault termination
+	if ms.cmd != nil && ms.cmdWait != nil {
+		waitDone := make(chan struct{})
+
+		// this ties waitDone to ctx with the additional compensated timeout duration
+		go func() { <-ms.k.ctx.Done(); time.Sleep(ms.k.state.Shim.WaitDelay + shimWaitTimeout); close(waitDone) }()
+
+		select {
+		case err := <-ms.cmdWait:
+			wstatus, ok := ms.cmd.ProcessState.Sys().(syscall.WaitStatus)
+			if ok {
+				if v := wstatus.ExitStatus(); v != 0 {
+					hasErr = true
+					exitCode = v
+				}
+			}
+
+			if ms.IsVerbose() {
+				if !ok {
+					if err != nil {
+						ms.Verbosef("wait: %v", err)
+					}
+				} else {
+					switch {
+					case wstatus.Exited():
+						ms.Verbosef("process %d exited with code %d", ms.cmd.Process.Pid, wstatus.ExitStatus())
+
+					case wstatus.CoreDump():
+						ms.Verbosef("process %d dumped core", ms.cmd.Process.Pid)
+
+					case wstatus.Signaled():
+						ms.Verbosef("process %d got %s", ms.cmd.Process.Pid, wstatus.Signal())
+
+					default:
+						ms.Verbosef("process %d exited with status %#x", ms.cmd.Process.Pid, wstatus)
+					}
+				}
+			}
+
+		case <-waitDone:
+			ms.Resume()
+			// this is only reachable when shim did not exit within shimWaitTimeout, after its WaitDelay has elapsed.
+			// This is different from the container failing to terminate within its timeout period, as that is enforced
+			// by the shim. This path is instead reached when there is a lockup in shim preventing it from completing.
+			log.Printf("process %d did not terminate", ms.cmd.Process.Pid)
+		}
+
+		ms.Resume()
+	}
+
+	if ms.uintptr&mainNeedsRevert != 0 {
+		if ok, err := ms.store.Do(ms.k.state.identity.unwrap(), func(c state.Cursor) {
+			if ms.uintptr&mainNeedsDestroy != 0 {
+				if err := c.Destroy(ms.k.state.id.unwrap()); err != nil {
+					perror(err, "destroy state entry")
+				}
+			}
+
+			var rt hst.Enablement
+			if states, err := c.Load(); err != nil {
+				// it is impossible to continue from this point;
+				// revert per-process state here to limit damage
+				ec := system.Process
+				if revertErr := ms.k.sys.Revert((*system.Criteria)(&ec)); revertErr != nil {
+					var joinError interface {
+						Unwrap() []error
+						error
+					}
+					if !errors.As(revertErr, &joinError) || joinError == nil {
+						perror(revertErr, "revert system setup")
+					} else {
+						for _, v := range joinError.Unwrap() {
+							perror(v, "revert system setup step")
+						}
+					}
+				}
+				perror(err, "load instance states")
+			} else {
+				ec := system.Process
+				if l := len(states); l == 0 {
+					ec |= system.User
+				} else {
+					ms.Verbosef("found %d instances, cleaning up without user-scoped operations", l)
+				}
+
+				// accumulate enablements of remaining launchers
+				for i, s := range states {
+					if s.Config != nil {
+						rt |= s.Config.Enablements.Unwrap()
+					} else {
+						log.Printf("state entry %d does not contain config", i)
+					}
+				}
+
+				ec |= rt ^ (hst.EWayland | hst.EX11 | hst.EDBus | hst.EPulse)
+				if ms.IsVerbose() {
+					if ec > 0 {
+						ms.Verbose("reverting operations scope", system.TypeString(ec))
+					}
+				}
+
+				if err = ms.k.sys.Revert((*system.Criteria)(&ec)); err != nil {
+					perror(err, "revert system setup")
+				}
+			}
+		}); err != nil {
+			if ok {
+				perror(err, "unlock state store")
+			} else {
+				perror(err, "open state store")
+			}
+		}
+	} else if ms.uintptr&mainNeedsDestroy != 0 {
+		panic("unreachable")
+	}
+}
+
+// fatal calls printMessageError, performs necessary cleanup, followed by a call to [os.Exit](1).
+func (ms mainState) fatal(fallback string, ferr error) {
+	printMessageError(fallback, ferr)
+	ms.beforeExit(true)
+	os.Exit(1)
+}
+
+// main carries out outcome and terminates. main does not return.
+func (k *outcome) main(msg message.Msg) {
+	if !k.active.CompareAndSwap(false, true) {
+		panic("outcome: attempted to run twice")
+	}
+
+	if k.ctx == nil || k.sys == nil || k.state == 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}
+
+	if err := k.sys.Commit(); err != nil {
+		ms.fatal("cannot commit system setup:", err)
+	}
+	ms.uintptr |= mainNeedsRevert
+	ms.store = state.NewMulti(msg, k.state.sc.RunDirPath)
+
+	ctx, cancel := context.WithCancel(k.ctx)
+	defer cancel()
+	ms.cancel = cancel
+
+	ms.cmd = exec.CommandContext(ctx, hsuPath.String())
+	ms.cmd.Stdin, ms.cmd.Stdout, ms.cmd.Stderr = os.Stdin, os.Stdout, os.Stderr
+	ms.cmd.Dir = fhs.Root // container init enters final working directory
+	// 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 {
+		ms.fatal("cannot create shim setup pipe:", err)
+	} else {
+		e = encoder
+		ms.cmd.Env = []string{
+			// passed through to shim by hsu
+			shimEnv + "=" + strconv.Itoa(fd),
+			// interpreted by hsu
+			"HAKUREI_IDENTITY=" + k.state.identity.String(),
+		}
+	}
+
+	if len(k.supp) > 0 {
+		msg.Verbosef("attaching supplementary group ids %s", k.supp)
+		// interpreted by hsu
+		ms.cmd.Env = append(ms.cmd.Env, "HAKUREI_GROUPS="+strings.Join(k.supp, " "))
+	}
+
+	msg.Verbosef("setuid helper at %s", hsuPath)
+	msg.Suspend()
+	if err := ms.cmd.Start(); err != nil {
+		ms.fatal("cannot start setuid wrapper:", err)
+	}
+	startTime := time.Now().UTC()
+	ms.cmdWait = make(chan error, 1)
+	// this ties context back to the life of the process
+	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 {
+			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 state.Cursor) {
+		if err := c.Save(&hst.State{
+			ID:      k.state.id.unwrap(),
+			PID:     os.Getpid(),
+			ShimPID: ms.cmd.Process.Pid,
+			Config:  k.config,
+			Time:    *ms.Time,
+		}); err != nil {
+			ms.fatal("cannot save state entry:", err)
+		}
+	}); err != nil {
+		if ok {
+			ms.uintptr |= mainNeedsDestroy
+			ms.fatal("cannot unlock state store:", err)
+		} else {
+			ms.fatal("cannot open state store:", err)
+		}
+	}
+	// state in store at this point, destroy defunct state entry on termination
+	ms.uintptr |= mainNeedsDestroy
+
+	// beforeExit ties shim process to context
+	ms.beforeExit(false)
+	os.Exit(0)
+}
+
+// printMessageError prints the error message according to [message.GetMessage],
+// or fallback prepended to err if an error message is not available.
+func printMessageError(fallback string, err error) {
+	m, ok := message.GetMessage(err)
+	if !ok {
+		log.Println(fallback, err)
+		return
+	}
+
+	log.Print(m)
+}