117 lines
2.9 KiB
Go
117 lines
2.9 KiB
Go
package fuseshim
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import (
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"bufio"
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"fmt"
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"io"
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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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"sync"
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"syscall"
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)
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// Maximum file write size we are prepared to receive from the kernel. Linux
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// appears to limit writes to 128 KiB.
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const maxWrite = 128 * 1024
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func lineLogger(wg *sync.WaitGroup, prefix string, r io.ReadCloser) {
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defer wg.Done()
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scanner := bufio.NewScanner(r)
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for scanner.Scan() {
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switch line := scanner.Text(); line {
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case `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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continue
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default:
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log.Printf("%s: %s", prefix, line)
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}
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}
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if err := scanner.Err(); err != nil {
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log.Printf("%s, error reading: %v", prefix, err)
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}
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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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wg.Add(2)
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go lineLogger(&wg, "mount helper output", stdout)
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go lineLogger(&wg, "mount helper error", stderr)
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wg.Wait()
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if err := cmd.Wait(); err != nil {
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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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