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