cri/server: use containerd/oci instead of libcontainer/devices

Looks like we had our own copy of the "getDevices" code already, so use
that code (which also matches the code that's used to _generate_ the spec,
so a better match).

Moving the code to a separate file, I also noticed that the _unix and _linux
code was _exactly_ the same (baring some `//nolint:` comments), so also
removing the duplicated code.

With this patch applied, we removed the dependency on the libcontainer/devices
package (leaving only libcontainer/user).

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

oci/utils_unix.go

@@ -0,0 +1,137 @@
+// +build !windows
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package oci
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+)
+
+var errNotADevice = errors.New("not a device node")
+
+// HostDevices returns all devices that can be found under /dev directory.
+func HostDevices() ([]specs.LinuxDevice, error) {
+	return getDevices("/dev", "")
+}
+
+func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
+	stat, err := os.Stat(path)
+	if err != nil {
+		return nil, errors.Wrap(err, "error stating device path")
+	}
+
+	if !stat.IsDir() {
+		dev, err := deviceFromPath(path)
+		if err != nil {
+			return nil, err
+		}
+		if containerPath != "" {
+			dev.Path = containerPath
+		}
+		return []specs.LinuxDevice{*dev}, nil
+	}
+
+	files, err := ioutil.ReadDir(path)
+	if err != nil {
+		return nil, err
+	}
+	var out []specs.LinuxDevice
+	for _, f := range files {
+		switch {
+		case f.IsDir():
+			switch f.Name() {
+			// ".lxc" & ".lxd-mounts" added to address https://github.com/lxc/lxd/issues/2825
+			// ".udev" added to address https://github.com/opencontainers/runc/issues/2093
+			case "pts", "shm", "fd", "mqueue", ".lxc", ".lxd-mounts", ".udev":
+				continue
+			default:
+				var cp string
+				if containerPath != "" {
+					cp = filepath.Join(containerPath, filepath.Base(f.Name()))
+				}
+				sub, err := getDevices(filepath.Join(path, f.Name()), cp)
+				if err != nil {
+					return nil, err
+				}
+
+				out = append(out, sub...)
+				continue
+			}
+		case f.Name() == "console":
+			continue
+		}
+		device, err := deviceFromPath(filepath.Join(path, f.Name()))
+		if err != nil {
+			if err == errNotADevice {
+				continue
+			}
+			if os.IsNotExist(err) {
+				continue
+			}
+			return nil, err
+		}
+		if containerPath != "" {
+			device.Path = filepath.Join(containerPath, filepath.Base(f.Name()))
+		}
+		out = append(out, *device)
+	}
+	return out, nil
+}
+
+func deviceFromPath(path string) (*specs.LinuxDevice, error) {
+	var stat unix.Stat_t
+	if err := unix.Lstat(path, &stat); err != nil {
+		return nil, err
+	}
+
+	var (
+		devNumber = uint64(stat.Rdev) //nolint: unconvert // the type is 32bit on mips.
+		major     = unix.Major(devNumber)
+		minor     = unix.Minor(devNumber)
+	)
+	if major == 0 {
+		return nil, errNotADevice
+	}
+
+	var (
+		devType string
+		mode    = stat.Mode
+	)
+	switch {
+	case mode&unix.S_IFBLK == unix.S_IFBLK:
+		devType = "b"
+	case mode&unix.S_IFCHR == unix.S_IFCHR:
+		devType = "c"
+	}
+	fm := os.FileMode(mode &^ unix.S_IFMT)
+	return &specs.LinuxDevice{
+		Type:     devType,
+		Path:     path,
+		Major:    int64(major),
+		Minor:    int64(minor),
+		FileMode: &fm,
+		UID:      &stat.Uid,
+		GID:      &stat.Gid,
+	}, nil
+}