return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen)
}

func (h *Cmsghdr) data(offset uintptr) unsafe.Pointer {
	return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)) + offset)
}

// SocketControlMessage represents a socket control message.
type SocketControlMessage struct {
	Header Cmsghdr
	Data   []byte
}

// ParseSocketControlMessage parses b as an array of socket control

	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
	h.Level = SOL_IP
	h.Type = IP_PKTINFO
	h.SetLen(CmsgLen(SizeofInet4Pktinfo))
	*(*Inet4Pktinfo)(h.data(0)) = *info
	return b
}

// PktInfo6 encodes Inet6Pktinfo into a socket control message of type IPV6_PKTINFO.
func PktInfo6(info *Inet6Pktinfo) []byte {
	b := make([]byte, CmsgSpace(SizeofInet6Pktinfo))
	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
	h.Level = SOL_IPV6

}

type IPv6Mreq struct {
	Multiaddr [16]byte /* in6_addr */
	Interface uint32
}

type Msghdr struct {
	Name       *byte
	Iov        *Iovec
	Control    *byte
	Flags      int32
	Namelen    int32
	Iovlen     int32
	Controllen int32
}

type Cmsghdr struct {
	Len   int32
	Level int32
	Type  int32
}

type Inet4Pktinfo struct {
	Addr    [4]byte /* in_addr */

	Pad  [96]int8
}

type Iovec struct {
	Base *byte
	Len  uint64
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint64
	Control    *byte
	Controllen uint64
	Flags      int32
	_          [4]byte
}

type Cmsghdr struct {
	Len   uint64
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte

	Addr RawSockaddr
	Pad  [96]int8
}

type Iovec struct {
	Base *byte
	Len  uint32
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint32
	Control    *byte
	Controllen uint32
	Flags      int32
}

type Cmsghdr struct {
	Len   uint32
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte
	Ifru [16]byte

	Pad  [96]int8
}

type Iovec struct {
	Base *byte
	Len  uint64
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint64
	Control    *byte
	Controllen uint64
	Flags      int32
	_          [4]byte
}

type Cmsghdr struct {
	Len   uint64
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte

	Addr RawSockaddr
	Pad  [96]int8
}

type Iovec struct {
	Base *byte
	Len  uint32
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint32
	Control    *byte
	Controllen uint32
	Flags      int32
}

type Cmsghdr struct {
	Len   uint32
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte
	Ifru [16]byte

	Pad  [96]uint8
}

type Iovec struct {
	Base *byte
	Len  uint64
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint64
	Control    *byte
	Controllen uint64
	Flags      int32
	_          [4]byte
}

type Cmsghdr struct {
	Len   uint64
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte

	Addr RawSockaddr
	Pad  [96]uint8
}

type Iovec struct {
	Base *byte
	Len  uint32
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint32
	Control    *byte
	Controllen uint32
	Flags      int32
}

type Cmsghdr struct {
	Len   uint32
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte
	Ifru [16]byte

	Pad  [96]uint8
}

type Iovec struct {
	Base *byte
	Len  uint64
}

type Msghdr struct {
	Name       *byte
	Namelen    uint32
	Iov        *Iovec
	Iovlen     uint64
	Control    *byte
	Controllen uint64
	Flags      int32
	_          [4]byte
}

type Cmsghdr struct {
	Len   uint64
	Level int32
	Type  int32
}

type ifreq struct {
	Ifrn [16]byte