return []Sys{
		&InterfaceMetrics{
			Type: int(m.raw[m.extOff]),
			MTU:  int(nativeEndian.Uint32(m.raw[m.extOff+8 : m.extOff+12])),
		},
	}
}

func probeRoutingStack() (int, map[int]*wireFormat) {
	rtm := &wireFormat{extOff: 36, bodyOff: sizeofRtMsghdrDarwin15}
	rtm.parse = rtm.parseRouteMessage
	rtm2 := &wireFormat{extOff: 36, bodyOff: sizeofRtMsghdr2Darwin15}
	rtm2.parse = rtm2.parseRouteMessage

	return []Sys{
		&InterfaceMetrics{
			Type: int(m.raw[m.extOff]),
			MTU:  int(nativeEndian.Uint32(m.raw[m.extOff+8 : m.extOff+12])),
		},
	}
}

func probeRoutingStack() (int, map[int]*wireFormat) {
	rtm := &wireFormat{extOff: 40, bodyOff: sizeofRtMsghdrNetBSD7}
	rtm.parse = rtm.parseRouteMessage
	ifm := &wireFormat{extOff: 16, bodyOff: sizeofIfMsghdrNetBSD7}
	ifm.parse = ifm.parseInterfaceMessage

	var extOff, bodyOff int
	if typ == syscall.NET_RT_IFLISTL {
		if len(b) < 20 {
			return nil, errMessageTooShort
		}
		extOff = int(nativeEndian.Uint16(b[18:20]))
		bodyOff = int(nativeEndian.Uint16(b[16:18]))
	} else {
		extOff = w.extOff
		bodyOff = w.bodyOff
	}
	if len(b) < extOff || len(b) < bodyOff {
		return nil, errInvalidMessage
	}

	if compatFreeBSD32 {
		rtm = &wireFormat{extOff: sizeofRtMsghdrFreeBSD10Emu - sizeofRtMetricsFreeBSD10Emu, bodyOff: sizeofRtMsghdrFreeBSD10Emu}
		ifm = &wireFormat{extOff: 16}
		ifam = &wireFormat{extOff: sizeofIfaMsghdrFreeBSD10Emu, bodyOff: sizeofIfaMsghdrFreeBSD10Emu}
		ifmam = &wireFormat{extOff: sizeofIfmaMsghdrFreeBSD10Emu, bodyOff: sizeofIfmaMsghdrFreeBSD10Emu}

func probeRoutingStack() (int, map[int]*wireFormat) {
	var p uintptr
	rtm := &wireFormat{extOff: -1, bodyOff: -1}
	rtm.parse = rtm.parseRouteMessage
	ifm := &wireFormat{extOff: -1, bodyOff: -1}
	ifm.parse = ifm.parseInterfaceMessage
	ifam := &wireFormat{extOff: -1, bodyOff: -1}
	ifam.parse = ifam.parseInterfaceAddrMessage
	ifanm := &wireFormat{extOff: -1, bodyOff: -1}
	ifanm.parse = ifanm.parseInterfaceAnnounceMessage

		Type:    int(b[3]),
		Flags:   int(nativeEndian.Uint32(b[8:12])),
		Index:   int(nativeEndian.Uint16(b[4:6])),
		ID:      uintptr(nativeEndian.Uint32(b[16:20])),
		Seq:     int(nativeEndian.Uint32(b[20:24])),
		extOff:  w.extOff,
		raw:     b[:l],
	}
	errno := syscall.Errno(nativeEndian.Uint32(b[28:32]))
	if errno != 0 {
		m.Err = errno
	}
	var err error

	}
	m := &InterfaceMessage{
		Version: int(b[2]),
		Type:    int(b[3]),
		Addrs:   make([]Addr, syscall.RTAX_MAX),
		Flags:   int(nativeEndian.Uint32(b[8:12])),
		Index:   int(nativeEndian.Uint16(b[12:14])),
		extOff:  w.extOff,
		raw:     b[:l],
	}
	a, err := parseLinkAddr(b[w.bodyOff:])
	if err != nil {
		return nil, err
	}
	m.Addrs[syscall.RTAX_IFP] = a
	m.Name = a.(*LinkAddr).Name
	return m, nil
}

	kernelAlign, wireFormats = probeRoutingStack()
}

func roundup(l int) int {
	if l == 0 {
		return kernelAlign
	}
	return (l + kernelAlign - 1) &^ (kernelAlign - 1)
}

type wireFormat struct {
	extOff  int // offset of header extension
	bodyOff int // offset of message body
	parse   func(RIBType, []byte) (Message, error)

	Version int    // message version
	Type    int    // message type
	Flags   int    // interface flags
	Index   int    // interface index
	Name    string // interface name
	Addrs   []Addr // addresses

	extOff int    // offset of header extension
	raw    []byte // raw message
}

// An InterfaceAddrMessage represents an interface address message.
type InterfaceAddrMessage struct {
	Version int    // message version

	ID      uintptr // sender's identifier; usually process ID
	Seq     int     // sequence number
	Err     error   // error on requested operation
	Addrs   []Addr  // addresses

	extOff int    // offset of header extension
	raw    []byte // raw message
}

// Marshal returns the binary encoding of m.
func (m *RouteMessage) Marshal() ([]byte, error) {
	return m.marshal()
}