mirror of https://github.com/docker/cli.git
59 lines
1.5 KiB
Go
59 lines
1.5 KiB
Go
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package mountinfo
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import (
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"os"
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"path/filepath"
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"golang.org/x/sys/unix"
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)
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// mountedByOpenat2 is a method of detecting a mount that works for all kinds
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// of mounts (incl. bind mounts), but requires a recent (v5.6+) linux kernel.
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func mountedByOpenat2(path string) (bool, error) {
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dir, last := filepath.Split(path)
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dirfd, err := unix.Openat2(unix.AT_FDCWD, dir, &unix.OpenHow{
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Flags: unix.O_PATH | unix.O_CLOEXEC,
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})
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if err != nil {
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if err == unix.ENOENT { // not a mount
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return false, nil
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}
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return false, &os.PathError{Op: "openat2", Path: dir, Err: err}
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}
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fd, err := unix.Openat2(dirfd, last, &unix.OpenHow{
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Flags: unix.O_PATH | unix.O_CLOEXEC | unix.O_NOFOLLOW,
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Resolve: unix.RESOLVE_NO_XDEV,
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})
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_ = unix.Close(dirfd)
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switch err {
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case nil: // definitely not a mount
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_ = unix.Close(fd)
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return false, nil
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case unix.EXDEV: // definitely a mount
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return true, nil
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case unix.ENOENT: // not a mount
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return false, nil
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}
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// not sure
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return false, &os.PathError{Op: "openat2", Path: path, Err: err}
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}
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func mounted(path string) (bool, error) {
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// Try a fast path, using openat2() with RESOLVE_NO_XDEV.
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mounted, err := mountedByOpenat2(path)
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if err == nil {
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return mounted, nil
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}
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// Another fast path: compare st.st_dev fields.
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mounted, err = mountedByStat(path)
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// This does not work for bind mounts, so false negative
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// is possible, therefore only trust if return is true.
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if mounted && err == nil {
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return mounted, nil
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}
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// Fallback to parsing mountinfo
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return mountedByMountinfo(path)
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}
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