swarm/api: support mounting manifests via FUSE (#3690)

vendor/bazil.org/fuse/mount_darwin.go

@@ -0,0 +1,208 @@
+package fuse
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+	"strconv"
+	"strings"
+	"sync"
+	"syscall"
+)
+
+var (
+	errNoAvail   = errors.New("no available fuse devices")
+	errNotLoaded = errors.New("osxfuse is not loaded")
+)
+
+func loadOSXFUSE(bin string) error {
+	cmd := exec.Command(bin)
+	cmd.Dir = "/"
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err := cmd.Run()
+	return err
+}
+
+func openOSXFUSEDev(devPrefix string) (*os.File, error) {
+	var f *os.File
+	var err error
+	for i := uint64(0); ; i++ {
+		path := devPrefix + strconv.FormatUint(i, 10)
+		f, err = os.OpenFile(path, os.O_RDWR, 0000)
+		if os.IsNotExist(err) {
+			if i == 0 {
+				// not even the first device was found -> fuse is not loaded
+				return nil, errNotLoaded
+			}
+
+			// we've run out of kernel-provided devices
+			return nil, errNoAvail
+		}
+
+		if err2, ok := err.(*os.PathError); ok && err2.Err == syscall.EBUSY {
+			// try the next one
+			continue
+		}
+
+		if err != nil {
+			return nil, err
+		}
+		return f, nil
+	}
+}
+
+func handleMountOSXFUSE(helperName string, errCh chan<- error) func(line string) (ignore bool) {
+	var noMountpointPrefix = helperName + `: `
+	const noMountpointSuffix = `: No such file or directory`
+	return func(line string) (ignore bool) {
+		if strings.HasPrefix(line, noMountpointPrefix) && strings.HasSuffix(line, noMountpointSuffix) {
+			// re-extract it from the error message in case some layer
+			// changed the path
+			mountpoint := line[len(noMountpointPrefix) : len(line)-len(noMountpointSuffix)]
+			err := &MountpointDoesNotExistError{
+				Path: mountpoint,
+			}
+			select {
+			case errCh <- err:
+				return true
+			default:
+				// not the first error; fall back to logging it
+				return false
+			}
+		}
+
+		return false
+	}
+}
+
+// isBoringMountOSXFUSEError returns whether the Wait error is
+// uninteresting; exit status 64 is.
+func isBoringMountOSXFUSEError(err error) bool {
+	if err, ok := err.(*exec.ExitError); ok && err.Exited() {
+		if status, ok := err.Sys().(syscall.WaitStatus); ok && status.ExitStatus() == 64 {
+			return true
+		}
+	}
+	return false
+}
+
+func callMount(bin string, daemonVar string, dir string, conf *mountConfig, f *os.File, ready chan<- struct{}, errp *error) error {
+	for k, v := range conf.options {
+		if strings.Contains(k, ",") || strings.Contains(v, ",") {
+			// Silly limitation but the mount helper does not
+			// understand any escaping. See TestMountOptionCommaError.
+			return fmt.Errorf("mount options cannot contain commas on darwin: %q=%q", k, v)
+		}
+	}
+	cmd := exec.Command(
+		bin,
+		"-o", conf.getOptions(),
+		// Tell osxfuse-kext how large our buffer is. It must split
+		// writes larger than this into multiple writes.
+		//
+		// OSXFUSE seems to ignore InitResponse.MaxWrite, and uses
+		// this instead.
+		"-o", "iosize="+strconv.FormatUint(maxWrite, 10),
+		// refers to fd passed in cmd.ExtraFiles
+		"3",
+		dir,
+	)
+	cmd.ExtraFiles = []*os.File{f}
+	cmd.Env = os.Environ()
+	// OSXFUSE <3.3.0
+	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_CALL_BY_LIB=")
+	// OSXFUSE >=3.3.0
+	cmd.Env = append(cmd.Env, "MOUNT_OSXFUSE_CALL_BY_LIB=")
+
+	daemon := os.Args[0]
+	if daemonVar != "" {
+		cmd.Env = append(cmd.Env, daemonVar+"="+daemon)
+	}
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return fmt.Errorf("setting up mount_osxfusefs stderr: %v", err)
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("setting up mount_osxfusefs stderr: %v", err)
+	}
+
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("mount_osxfusefs: %v", err)
+	}
+	helperErrCh := make(chan error, 1)
+	go func() {
+		var wg sync.WaitGroup
+		wg.Add(2)
+		go lineLogger(&wg, "mount helper output", neverIgnoreLine, stdout)
+		helperName := path.Base(bin)
+		go lineLogger(&wg, "mount helper error", handleMountOSXFUSE(helperName, helperErrCh), stderr)
+		wg.Wait()
+		if err := cmd.Wait(); err != nil {
+			// see if we have a better error to report
+			select {
+			case helperErr := <-helperErrCh:
+				// log the Wait error if it's not what we expected
+				if !isBoringMountOSXFUSEError(err) {
+					log.Printf("mount helper failed: %v", err)
+				}
+				// and now return what we grabbed from stderr as the real
+				// error
+				*errp = helperErr
+				close(ready)
+				return
+			default:
+				// nope, fall back to generic message
+			}
+
+			*errp = fmt.Errorf("mount_osxfusefs: %v", err)
+			close(ready)
+			return
+		}
+
+		*errp = nil
+		close(ready)
+	}()
+	return nil
+}
+
+func mount(dir string, conf *mountConfig, ready chan<- struct{}, errp *error) (*os.File, error) {
+	locations := conf.osxfuseLocations
+	if locations == nil {
+		locations = []OSXFUSEPaths{
+			OSXFUSELocationV3,
+			OSXFUSELocationV2,
+		}
+	}
+	for _, loc := range locations {
+		if _, err := os.Stat(loc.Mount); os.IsNotExist(err) {
+			// try the other locations
+			continue
+		}
+
+		f, err := openOSXFUSEDev(loc.DevicePrefix)
+		if err == errNotLoaded {
+			err = loadOSXFUSE(loc.Load)
+			if err != nil {
+				return nil, err
+			}
+			// try again
+			f, err = openOSXFUSEDev(loc.DevicePrefix)
+		}
+		if err != nil {
+			return nil, err
+		}
+		err = callMount(loc.Mount, loc.DaemonVar, dir, conf, f, ready, errp)
+		if err != nil {
+			f.Close()
+			return nil, err
+		}
+		return f, nil
+	}
+	return nil, ErrOSXFUSENotFound
+}