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package fuse
import (
"fmt"
"log"
"net"
"os"
"os/exec"
"strings"
"sync"
"syscall"
)
func handleFusermountStderr(errCh chan<- error) func(line string) (ignore bool) {
return func(line string) (ignore bool) {
if line == `fusermount: failed to open /etc/fuse.conf: Permission denied` {
// Silence this particular message, it occurs way too
// commonly and isn't very relevant to whether the mount
// succeeds or not.
return true
}
const (
noMountpointPrefix = `fusermount: failed to access mountpoint `
noMountpointSuffix = `: No such file or directory`
)
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
}
}
// isBoringFusermountError returns whether the Wait error is
// uninteresting; exit status 1 is.
func isBoringFusermountError(err error) bool {
if err, ok := err.(*exec.ExitError); ok && err.Exited() {
if status, ok := err.Sys().(syscall.WaitStatus); ok && status.ExitStatus() == 1 {
return true
}
}
return false
}
func mount(dir string, conf *mountConfig, ready chan<- struct{}, errp *error) (fusefd *os.File, err error) {
// linux mount is never delayed
close(ready)
fds, err := syscall.Socketpair(syscall.AF_FILE, syscall.SOCK_STREAM, 0)
if err != nil {
return nil, fmt.Errorf("socketpair error: %v", err)
}
writeFile := os.NewFile(uintptr(fds[0]), "fusermount-child-writes")
defer writeFile.Close()
readFile := os.NewFile(uintptr(fds[1]), "fusermount-parent-reads")
defer readFile.Close()
cmd := exec.Command(
"fusermount",
"-o", conf.getOptions(),
"--",
dir,
)
cmd.Env = append(os.Environ(), "_FUSE_COMMFD=3")
cmd.ExtraFiles = []*os.File{writeFile}
var wg sync.WaitGroup
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, fmt.Errorf("setting up fusermount stderr: %v", err)
}
stderr, err := cmd.StderrPipe()
if err != nil {
return nil, fmt.Errorf("setting up fusermount stderr: %v", err)
}
if err := cmd.Start(); err != nil {
return nil, fmt.Errorf("fusermount: %v", err)
}
helperErrCh := make(chan error, 1)
wg.Add(2)
go lineLogger(&wg, "mount helper output", neverIgnoreLine, stdout)
go lineLogger(&wg, "mount helper error", handleFusermountStderr(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 !isBoringFusermountError(err) {
log.Printf("mount helper failed: %v", err)
}
// and now return what we grabbed from stderr as the real
// error
return nil, helperErr
default:
// nope, fall back to generic message
}
return nil, fmt.Errorf("fusermount: %v", err)
}
c, err := net.FileConn(readFile)
if err != nil {
return nil, fmt.Errorf("FileConn from fusermount socket: %v", err)
}
defer c.Close()
uc, ok := c.(*net.UnixConn)
if !ok {
return nil, fmt.Errorf("unexpected FileConn type; expected UnixConn, got %T", c)
}
buf := make([]byte, 32) // expect 1 byte
oob := make([]byte, 32) // expect 24 bytes
_, oobn, _, _, err := uc.ReadMsgUnix(buf, oob)
scms, err := syscall.ParseSocketControlMessage(oob[:oobn])
if err != nil {
return nil, fmt.Errorf("ParseSocketControlMessage: %v", err)
}
if len(scms) != 1 {
return nil, fmt.Errorf("expected 1 SocketControlMessage; got scms = %#v", scms)
}
scm := scms[0]
gotFds, err := syscall.ParseUnixRights(&scm)
if err != nil {
return nil, fmt.Errorf("syscall.ParseUnixRights: %v", err)
}
if len(gotFds) != 1 {
return nil, fmt.Errorf("wanted 1 fd; got %#v", gotFds)
}
f := os.NewFile(uintptr(gotFds[0]), "/dev/fuse")
return f, nil
}