container: remove setup pipe helper

The API forces use of finalizer to close the read end of the setup pipe, which is no longer considered acceptable. Exporting this as part of package container also imposes unnecessary maintenance burden.

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

cmd/sharefs/fuse.go

@@ -19,7 +19,6 @@ import (
 	"encoding/gob"
 	"errors"
 	"fmt"
-	"io"
 	"log"
 	"os"
 	"os/exec"
@@ -470,13 +469,14 @@ func _main(s ...string) (exitCode int) {
 			os.NewFile(uintptr(C.fuse_session_fd(se)), "fuse"),
 		))
 
-		var setupWriter io.WriteCloser
-		if fd, w, err := container.Setup(&z.ExtraFiles); err != nil {
+		var setupPipe [2]*os.File
+		if r, w, err := os.Pipe(); err != nil {
 			log.Println(err)
 			return 5
 		} else {
-			z.Args = append(z.Args, "-osetup="+strconv.Itoa(fd))
-			setupWriter = w
+			z.Args = append(z.Args, "-osetup="+strconv.Itoa(3+len(z.ExtraFiles)))
+			z.ExtraFiles = append(z.ExtraFiles, r)
+			setupPipe[0], setupPipe[1] = r, w
 		}
 
 		if err := z.Start(); err != nil {
@@ -487,6 +487,9 @@ func _main(s ...string) (exitCode int) {
 			}
 			return 5
 		}
+		if err := setupPipe[0].Close(); err != nil {
+			log.Println(err)
+		}
 		if err := z.Serve(); err != nil {
 			if m, ok := message.GetMessage(err); ok {
 				log.Println(m)
@@ -496,10 +499,10 @@ func _main(s ...string) (exitCode int) {
 			return 5
 		}
 
-		if err := gob.NewEncoder(setupWriter).Encode(&setup); err != nil {
+		if err := gob.NewEncoder(setupPipe[1]).Encode(&setup); err != nil {
 			log.Println(err)
 			return 5
-		} else if err = setupWriter.Close(); err != nil {
+		} else if err = setupPipe[1].Close(); err != nil {
 			log.Println(err)
 		}
 

container/container.go

@@ -53,7 +53,7 @@ type (
 		ExtraFiles []*os.File
 
 		// Write end of a pipe connected to the init to deliver [Params].
-		setup *os.File
+		setup [2]*os.File
 		// Cancels the context passed to the underlying cmd.
 		cancel context.CancelFunc
 		// Closed after Wait returns. Keeps the spawning thread alive.
@@ -287,14 +287,16 @@ func (p *Container) Start() error {
 	}
 
 	// place setup pipe before user supplied extra files, this is later restored by init
-	if fd, f, err := Setup(&p.cmd.ExtraFiles); err != nil {
+	if r, w, err := os.Pipe(); err != nil {
 		return &StartError{
 			Fatal: true,
 			Step:  "set up params stream",
 			Err:   err,
 		}
 	} else {
-		p.setup = f
+		fd := 3 + len(p.cmd.ExtraFiles)
+		p.cmd.ExtraFiles = append(p.cmd.ExtraFiles, r)
+		p.setup[0], p.setup[1] = r, w
 		p.cmd.Env = []string{setupEnv + "=" + strconv.Itoa(fd)}
 	}
 	p.cmd.ExtraFiles = append(p.cmd.ExtraFiles, p.ExtraFiles...)
@@ -428,14 +430,30 @@ func (p *Container) Start() error {
 // Serve serves [Container.Params] to the container init.
 //
 // Serve must only be called once.
-func (p *Container) Serve() error {
-	if p.setup == nil {
+func (p *Container) Serve() (err error) {
+	if p.setup[0] == nil || p.setup[1] == nil {
 		panic("invalid serve")
 	}
+	defer func() {
+		if closeErr := p.setup[1].Close(); err == nil {
+			err = closeErr
+		}
 
-	setup := p.setup
-	p.setup = nil
-	if err := setup.SetDeadline(time.Now().Add(initSetupTimeout)); err != nil {
+		if err != nil {
+			p.cancel()
+		}
+		p.setup[0], p.setup[1] = nil, nil
+	}()
+	if err = p.setup[0].Close(); err != nil {
+		return &StartError{
+			Fatal:       true,
+			Step:        "close read end of init pipe",
+			Err:         err,
+			Passthrough: true,
+		}
+	}
+
+	if err = p.setup[1].SetDeadline(time.Now().Add(initSetupTimeout)); err != nil {
 		return &StartError{
 			Fatal:       true,
 			Step:        "set init pipe deadline",
@@ -445,7 +463,6 @@ func (p *Container) Serve() error {
 	}
 
 	if p.Path == nil {
-		p.cancel()
 		return &StartError{
 			Step:   "invalid executable pathname",
 			Err:    EINVAL,
@@ -461,18 +478,13 @@ func (p *Container) Serve() error {
 		p.SeccompRules = make([]std.NativeRule, 0)
 	}
 
-	err := gob.NewEncoder(setup).Encode(&initParams{
+	return gob.NewEncoder(p.setup[1]).Encode(&initParams{
 		p.Params,
 		Getuid(),
 		Getgid(),
 		len(p.ExtraFiles),
 		p.msg.IsVerbose(),
 	})
-	_ = setup.Close()
-	if err != nil {
-		p.cancel()
-	}
-	return err
 }
 
 // Wait blocks until the container init process to exit and releases any

container/params.go

@@ -8,17 +8,6 @@ import (
 	"syscall"
 )
 
-// Setup appends the read end of a pipe for setup params transmission and returns its fd.
-func Setup(extraFiles *[]*os.File) (int, *os.File, error) {
-	if r, w, err := os.Pipe(); err != nil {
-		return -1, nil, err
-	} else {
-		fd := 3 + len(*extraFiles)
-		*extraFiles = append(*extraFiles, r)
-		return fd, w, nil
-	}
-}
-
 var (
 	ErrReceiveEnv = errors.New("environment variable not set")
 )

container/params_test.go

@@ -1,10 +1,8 @@
 package container_test
 
 import (
-	"encoding/gob"
 	"errors"
 	"os"
-	"slices"
 	"strconv"
 	"syscall"
 	"testing"
@@ -52,74 +50,4 @@ func TestSetupReceive(t *testing.T) {
 			t.Errorf("Receive: error = %v, want %v", err, syscall.EDOM)
 		}
 	})
-
-	t.Run("setup receive", func(t *testing.T) {
-		check := func(t *testing.T, useNilFdp bool) {
-			const key = "TEST_SETUP_RECEIVE"
-			payload := []uint64{syscall.MS_MGC_VAL, syscall.MS_MGC_MSK, syscall.MS_ASYNC, syscall.MS_ACTIVE}
-
-			encoderDone := make(chan error, 1)
-			extraFiles := make([]*os.File, 0, 1)
-			deadline, _ := t.Deadline()
-			if fd, f, err := container.Setup(&extraFiles); err != nil {
-				t.Fatalf("Setup: error = %v", err)
-			} else if fd != 3 {
-				t.Fatalf("Setup: fd = %d, want 3", fd)
-			} else {
-				if err = f.SetDeadline(deadline); err != nil {
-					t.Fatal(err.Error())
-				}
-				go func() { encoderDone <- gob.NewEncoder(f).Encode(payload) }()
-			}
-
-			if len(extraFiles) != 1 {
-				t.Fatalf("extraFiles: len = %v, want 1", len(extraFiles))
-			}
-
-			var dupFd int
-			if fd, err := syscall.Dup(int(extraFiles[0].Fd())); err != nil {
-				t.Fatalf("Dup: error = %v", err)
-			} else {
-				syscall.CloseOnExec(fd)
-				dupFd = fd
-				t.Setenv(key, strconv.Itoa(fd))
-			}
-
-			var (
-				gotPayload []uint64
-				fdp        *uintptr
-			)
-			if !useNilFdp {
-				fdp = new(uintptr)
-			}
-			var closeFile func() error
-			if f, err := container.Receive(key, &gotPayload, fdp); err != nil {
-				t.Fatalf("Receive: error = %v", err)
-			} else {
-				closeFile = f
-
-				if !slices.Equal(payload, gotPayload) {
-					t.Errorf("Receive: %#v, want %#v", gotPayload, payload)
-				}
-			}
-			if !useNilFdp {
-				if int(*fdp) != dupFd {
-					t.Errorf("Fd: %d, want %d", *fdp, dupFd)
-				}
-			}
-
-			if err := <-encoderDone; err != nil {
-				t.Errorf("Encode: error = %v", err)
-			}
-
-			if closeFile != nil {
-				if err := closeFile(); err != nil {
-					t.Errorf("Close: error = %v", err)
-				}
-			}
-		}
-
-		t.Run("fp", func(t *testing.T) { check(t, false) })
-		t.Run("nil", func(t *testing.T) { check(t, true) })
-	})
 }

internal/outcome/process.go

@@ -13,7 +13,6 @@ import (
 	"time"
 
 	"hakurei.app/check"
-	"hakurei.app/container"
 	"hakurei.app/fhs"
 	"hakurei.app/hst"
 	"hakurei.app/internal/info"
@@ -372,17 +371,18 @@ func (k *outcome) start(ctx context.Context, msg message.Msg,
 	// shim runs in the same session as monitor; see shim.go for behaviour
 	cmd.Cancel = func() error { return cmd.Process.Signal(syscall.SIGCONT) }
 
-	var shimPipe *os.File
-	if fd, w, err := container.Setup(&cmd.ExtraFiles); err != nil {
+	var shimPipe [2]*os.File
+	if r, w, err := os.Pipe(); err != nil {
 		return cmd, nil, &hst.AppError{Step: "create shim setup pipe", Err: err}
 	} else {
-		shimPipe = w
 		cmd.Env = []string{
 			// passed through to shim by hsu
-			shimEnv + "=" + strconv.Itoa(fd),
+			shimEnv + "=" + strconv.Itoa(3+len(cmd.ExtraFiles)),
 			// interpreted by hsu
 			"HAKUREI_IDENTITY=" + k.state.identity.String(),
 		}
+		cmd.ExtraFiles = append(cmd.ExtraFiles, r)
+		shimPipe[0], shimPipe[1] = r, w
 	}
 
 	if len(k.supp) > 0 {
@@ -393,12 +393,16 @@ func (k *outcome) start(ctx context.Context, msg message.Msg,
 
 	msg.Verbosef("setuid helper at %s", hsuPath)
 	if err := cmd.Start(); err != nil {
+		_, _ = shimPipe[0].Close(), shimPipe[1].Close()
 		msg.Resume()
-		return cmd, shimPipe, &hst.AppError{Step: "start setuid wrapper", Err: err}
+		return cmd, nil, &hst.AppError{Step: "start setuid wrapper", Err: err}
+	}
+	if err := shimPipe[0].Close(); err != nil {
+		msg.Verbose(err)
 	}
 
 	*startTime = time.Now().UTC()
-	return cmd, shimPipe, nil
+	return cmd, shimPipe[1], nil
 }
 
 // serveShim serves outcomeState through the shim setup pipe.
@@ -411,11 +415,11 @@ func serveShim(msg message.Msg, shimPipe *os.File, state *outcomeState) error {
 		msg.Verbose(err.Error())
 	}
 	if err := gob.NewEncoder(shimPipe).Encode(state); err != nil {
+		_ = shimPipe.Close()
 		msg.Resume()
 		return &hst.AppError{Step: "transmit shim config", Err: err}
 	}
-	_ = shimPipe.Close()
-	return nil
+	return shimPipe.Close()
 }
 
 // printMessageError prints the error message according to [message.GetMessage],