Copied mount_linux.go.

mount_linux.go

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