Add --device flag to ctr

Closes #3066

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

oci/spec_opts_unix.go

@@ -0,0 +1,63 @@
+// +build !linux,!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 (
+	"os"
+
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+	"golang.org/x/sys/unix"
+)
+
+func deviceFromPath(path, permissions 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)
+		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)
+	return &specs.LinuxDevice{
+		Type:     devType,
+		Path:     path,
+		Major:    int64(major),
+		Minor:    int64(minor),
+		FileMode: &fm,
+		UID:      &stat.Uid,
+		GID:      &stat.Gid,
+	}, nil
+}