nativeEndian.PutUint32(b[16:20], uint32(m.Flags))
	nativeEndian.PutUint16(b[6:8], uint16(m.Index))
	nativeEndian.PutUint32(b[24:28], uint32(m.ID))
	nativeEndian.PutUint32(b[28:32], uint32(m.Seq))
	attrs, err := marshalAddrs(b[sizeofRtMsghdr:], m.Addrs)
	if err != nil {
		return nil, err
	}
	if attrs > 0 {
		nativeEndian.PutUint32(b[12:16], uint32(attrs))
	}
	return b, nil
}

	nativeEndian.PutUint32(b[8:12], uint32(m.Flags))
	nativeEndian.PutUint16(b[4:6], uint16(m.Index))
	nativeEndian.PutUint32(b[16:20], uint32(m.ID))
	nativeEndian.PutUint32(b[20:24], uint32(m.Seq))
	attrs, err := marshalAddrs(b[w.bodyOff:], m.Addrs)
	if err != nil {
		return nil, err
	}
	if attrs > 0 {
		nativeEndian.PutUint32(b[12:16], uint32(attrs))
	}
	return b, nil
}

			_, ll := a.lenAndSpace()
			l += ll
		case *DefaultAddr:
			_, ll := a.lenAndSpace()
			l += ll
		}
	}
	return l
}

// marshalAddrs marshals as and returns a bitmap indicating which
// address is stored in b.
func marshalAddrs(b []byte, as []Addr) (uint, error) {
	var attrs uint
	for i, a := range as {
		switch a := a.(type) {
		case *LinkAddr:
			l, err := a.marshal(b)