util_linux.go

// +build linux

package shared

import (
	"bufio"
	"fmt"
	"os"
	"path/filepath"
	"reflect"
	"strings"
	"syscall"
	"unsafe"

	"golang.org/x/sys/unix"

	"github.com/lxc/lxd/shared/units"
)

// --- pure Go functions ---

func GetFileStat(p string) (uid int, gid int, major uint32, minor uint32, inode uint64, nlink int, err error) {
	var stat unix.Stat_t
	err = unix.Lstat(p, &stat)
	if err != nil {
		return
	}
	uid = int(stat.Uid)
	gid = int(stat.Gid)
	inode = uint64(stat.Ino)
	nlink = int(stat.Nlink)
	if stat.Mode&unix.S_IFBLK != 0 || stat.Mode&unix.S_IFCHR != 0 {
		major = unix.Major(stat.Rdev)
		minor = unix.Minor(stat.Rdev)
	}

	return
}

// GetPathMode returns a os.FileMode for the provided path
func GetPathMode(path string) (os.FileMode, error) {
	fi, err := os.Stat(path)
	if err != nil {
		return os.FileMode(0000), err
	}

	mode, _, _ := GetOwnerMode(fi)
	return mode, nil
}

func parseMountinfo(name string) int {
	// In case someone uses symlinks we need to look for the actual
	// mountpoint.
	actualPath, err := filepath.EvalSymlinks(name)
	if err != nil {
		return -1
	}

	f, err := os.Open("/proc/self/mountinfo")
	if err != nil {
		return -1
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := scanner.Text()
		tokens := strings.Fields(line)
		if len(tokens) < 5 {
			return -1
		}
		cleanPath := filepath.Clean(tokens[4])
		if cleanPath == actualPath {
			return 1
		}
	}

	return 0
}

func IsMountPoint(name string) bool {
	// If we find a mount entry, it is obviously a mount point.
	ret := parseMountinfo(name)
	if ret == 1 {
		return true
	}

	// Get the stat details.
	stat, err := os.Stat(name)
	if err != nil {
		return false
	}

	rootStat, err := os.Lstat(name + "/..")
	if err != nil {
		return false
	}

	// If the directory has the same device as parent, then it's not a mountpoint.
	if stat.Sys().(*syscall.Stat_t).Dev == rootStat.Sys().(*syscall.Stat_t).Dev {
		return false
	}

	// Btrfs annoyingly uses a different Dev id for different subvolumes on the same mount.
	// So for btrfs, we require a matching mount entry in mountinfo.
	fs := unix.Statfs_t{}
	err = unix.Statfs(name, &fs)
	if err == nil && fs.Type == filesystemSuperMagicBtrfs {
		return false
	}

	return true
}

func SetSize(fd int, width int, height int) (err error) {
	var dimensions [4]uint16
	dimensions[0] = uint16(height)
	dimensions[1] = uint16(width)

	if _, _, err := unix.Syscall6(unix.SYS_IOCTL, uintptr(fd), uintptr(unix.TIOCSWINSZ), uintptr(unsafe.Pointer(&dimensions)), 0, 0, 0); err != 0 {
		return err
	}
	return nil
}

// This uses ssize_t llistxattr(const char *path, char *list, size_t size); to
// handle symbolic links (should it in the future be possible to set extended
// attributed on symlinks): If path is a symbolic link the extended attributes
// associated with the link itself are retrieved.
func llistxattr(path string, list []byte) (sz int, err error) {
	var _p0 *byte
	_p0, err = unix.BytePtrFromString(path)
	if err != nil {
		return
	}
	var _p1 unsafe.Pointer
	if len(list) > 0 {
		_p1 = unsafe.Pointer(&list[0])
	} else {
		_p1 = unsafe.Pointer(nil)
	}
	r0, _, e1 := unix.Syscall(unix.SYS_LLISTXATTR, uintptr(unsafe.Pointer(_p0)), uintptr(_p1), uintptr(len(list)))
	sz = int(r0)
	if e1 != 0 {
		err = e1
	}
	return
}

// GetAllXattr retrieves all extended attributes associated with a file,
// directory or symbolic link.
func GetAllXattr(path string) (xattrs map[string]string, err error) {
	e1 := fmt.Errorf("Extended attributes changed during retrieval")

	// Call llistxattr() twice: First, to determine the size of the buffer
	// we need to allocate to store the extended attributes, second, to
	// actually store the extended attributes in the buffer. Also, check if
	// the size/number of extended attributes hasn't changed between the two
	// calls.
	pre, err := llistxattr(path, nil)
	if err != nil || pre < 0 {
		return nil, err
	}
	if pre == 0 {
		return nil, nil
	}

	dest := make([]byte, pre)

	post, err := llistxattr(path, dest)
	if err != nil || post < 0 {
		return nil, err
	}
	if post != pre {
		return nil, e1
	}

	split := strings.Split(string(dest), "\x00")
	if split == nil {
		return nil, fmt.Errorf("No valid extended attribute key found")
	}
	// *listxattr functions return a list of  names  as  an unordered array
	// of null-terminated character strings (attribute names are separated
	// by null bytes ('\0')), like this: user.name1\0system.name1\0user.name2\0
	// Since we split at the '\0'-byte the last element of the slice will be
	// the empty string. We remove it:
	if split[len(split)-1] == "" {
		split = split[:len(split)-1]
	}

	xattrs = make(map[string]string, len(split))

	for _, x := range split {
		xattr := string(x)
		// Call Getxattr() twice: First, to determine the size of the
		// buffer we need to allocate to store the extended attributes,
		// second, to actually store the extended attributes in the
		// buffer. Also, check if the size of the extended attribute
		// hasn't changed between the two calls.
		pre, err = unix.Getxattr(path, xattr, nil)
		if err != nil || pre < 0 {
			return nil, err
		}

		dest = make([]byte, pre)
		post := 0
		if pre > 0 {
			post, err = unix.Getxattr(path, xattr, dest)
			if err != nil || post < 0 {
				return nil, err
			}
		}

		if post != pre {
			return nil, e1
		}

		xattrs[xattr] = string(dest)
	}

	return xattrs, nil
}

var ObjectFound = fmt.Errorf("Found requested object")

func LookupUUIDByBlockDevPath(diskDevice string) (string, error) {
	uuid := ""
	readUUID := func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if (info.Mode() & os.ModeSymlink) == os.ModeSymlink {
			link, err := os.Readlink(path)
			if err != nil {
				return err
			}

			// filepath.Join() will call Clean() on the result and
			// thus resolve those ugly "../../" parts that make it
			// hard to compare the strings.
			absPath := filepath.Join("/dev/disk/by-uuid", link)
			if absPath == diskDevice {
				uuid = path
				// Will allows us to avoid needlessly travers
				// the whole directory.
				return ObjectFound
			}
		}
		return nil
	}

	err := filepath.Walk("/dev/disk/by-uuid", readUUID)
	if err != nil && err != ObjectFound {
		return "", fmt.Errorf("Failed to detect UUID: %s", err)
	}

	if uuid == "" {
		return "", fmt.Errorf("Failed to detect UUID")
	}

	lastSlash := strings.LastIndex(uuid, "/")
	return uuid[lastSlash+1:], nil
}

// Detect whether err is an errno.
func GetErrno(err error) (errno error, iserrno bool) {
	sysErr, ok := err.(*os.SyscallError)
	if ok {
		return sysErr.Err, true
	}

	pathErr, ok := err.(*os.PathError)
	if ok {
		return pathErr.Err, true
	}

	tmpErrno, ok := err.(unix.Errno)
	if ok {
		return tmpErrno, true
	}

	return nil, false
}

// Utsname returns the same info as unix.Utsname, as strings
type Utsname struct {
	Sysname    string
	Nodename   string
	Release    string
	Version    string
	Machine    string
	Domainname string
}

// Uname returns Utsname as strings
func Uname() (*Utsname, error) {
	/*
	 * Based on: https://groups.google.com/forum/#!topic/golang-nuts/Jel8Bb-YwX8
	 * there is really no better way to do this, which is
	 * unfortunate. Also, we ditch the more accepted CharsToString
	 * version in that thread, since it doesn't seem as portable,
	 * viz. github issue #206.
	 */

	uname := unix.Utsname{}
	err := unix.Uname(&uname)
	if err != nil {
		return nil, err
	}

	return &Utsname{
		Sysname:    intArrayToString(uname.Sysname),
		Nodename:   intArrayToString(uname.Nodename),
		Release:    intArrayToString(uname.Release),
		Version:    intArrayToString(uname.Version),
		Machine:    intArrayToString(uname.Machine),
		Domainname: intArrayToString(uname.Domainname),
	}, nil
}

func intArrayToString(arr interface{}) string {
	slice := reflect.ValueOf(arr)
	s := ""
	for i := 0; i < slice.Len(); i++ {
		val := slice.Index(i)
		valInt := int64(-1)

		switch val.Kind() {
		case reflect.Int:
		case reflect.Int8:
			valInt = int64(val.Int())
		case reflect.Uint:
		case reflect.Uint8:
			valInt = int64(val.Uint())
		default:
			continue
		}

		if valInt == 0 {
			break
		}

		s += string(byte(valInt))
	}

	return s
}

func Statvfs(path string) (*unix.Statfs_t, error) {
	var st unix.Statfs_t

	err := unix.Statfs(path, &st)
	if err != nil {
		return nil, err
	}

	return &st, nil
}

func DeviceTotalMemory() (int64, error) {
	// Open /proc/meminfo
	f, err := os.Open("/proc/meminfo")
	if err != nil {
		return -1, err
	}
	defer f.Close()

	// Read it line by line
	scan := bufio.NewScanner(f)
	for scan.Scan() {
		line := scan.Text()

		// We only care about MemTotal
		if !strings.HasPrefix(line, "MemTotal:") {
			continue
		}

		// Extract the before last (value) and last (unit) fields
		fields := strings.Split(line, " ")
		value := fields[len(fields)-2] + fields[len(fields)-1]

		// Feed the result to units.ParseByteSizeString to get an int value
		valueBytes, err := units.ParseByteSizeString(value)
		if err != nil {
			return -1, err
		}

		return valueBytes, nil
	}

	return -1, fmt.Errorf("Couldn't find MemTotal")
}