986f076276
Add a new generic container registry client via a new `container` package. Use this to create a command line utility as well as a new upload target for container registries. The code uses the github.com/containers/* project and packages to interact with container registires that is also used by skopeo, podman et al. One if the dependencies is `proglottis/gpgme` that is using cgo to bind libgpgme, so we have to add the corresponding devel package to the BuildRequires as well as installing it on CI. Checks will follow later via an integration test.
101 lines
3 KiB
Go
101 lines
3 KiB
Go
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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// MountedFast is a method of detecting a mount point without reading
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// mountinfo from procfs. A caller can only trust the result if no error
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// and sure == true are returned. Otherwise, other methods (e.g. parsing
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// /proc/mounts) have to be used. If unsure, use Mounted instead (which
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// uses MountedFast, but falls back to parsing mountinfo if needed).
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//
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// If a non-existent path is specified, an appropriate error is returned.
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// In case the caller is not interested in this particular error, it should
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// be handled separately using e.g. errors.Is(err, os.ErrNotExist).
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//
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// This function is only available on Linux. When available (since kernel
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// v5.6), openat2(2) syscall is used to reliably detect all mounts. Otherwise,
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// the implementation falls back to using stat(2), which can reliably detect
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// normal (but not bind) mounts.
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func MountedFast(path string) (mounted, sure bool, err error) {
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// Root is always mounted.
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if path == string(os.PathSeparator) {
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return true, true, nil
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}
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path, err = normalizePath(path)
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if err != nil {
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return false, false, err
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}
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mounted, sure, err = mountedFast(path)
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return
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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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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 { //nolint:errorlint // unix errors are bare
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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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}
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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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// mountedFast is similar to MountedFast, except it expects a normalized path.
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func mountedFast(path string) (mounted, sure bool, err error) {
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// Root is always mounted.
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if path == string(os.PathSeparator) {
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return true, true, nil
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}
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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, true, 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 true, true, nil
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}
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return
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}
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func mounted(path string) (bool, error) {
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path, err := normalizePath(path)
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if err != nil {
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return false, err
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}
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mounted, sure, err := mountedFast(path)
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if sure && 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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