diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..e69de29
diff --git a/cmd/root.go b/cmd/root.go
new file mode 100644
index 0000000..6597d83
--- /dev/null
+++ b/cmd/root.go
@@ -0,0 +1,46 @@
+/*
+Copyright © 2023 NAME HERE <EMAIL ADDRESS>
+*/
+package cmd
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+// rootCmd represents the base command when called without any subcommands
+var rootCmd = &cobra.Command{
+	Use:   "dtool",
+	Short: "dns resolver probing tool",
+	Long: `A tool for probing open resolvers for various purpose. The following modules are implemented.
+
+Modules:
+	upstream	probe to get the upstream recursive resolvers of the given resolver as many as possible
+	ttl			probe to test if resolvers on the resolution path change the authoritative TTL value
+	cache		probe to enumerate the cache`,
+	// Uncomment the following line if your bare application
+	// has an action associated with it:
+	// Run: func(cmd *cobra.Command, args []string) { },
+}
+
+// Execute adds all child commands to the root command and sets flags appropriately.
+// This is called by main.main(). It only needs to happen once to the rootCmd.
+func Execute() {
+	err := rootCmd.Execute()
+	if err != nil {
+		os.Exit(1)
+	}
+}
+
+func init() {
+	// Here you will define your flags and configuration settings.
+	// Cobra supports persistent flags, which, if defined here,
+	// will be global for your application.
+
+	// rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.dtool.yaml)")
+
+	// Cobra also supports local flags, which will only run
+	// when this action is called directly.
+	rootCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
+}
diff --git a/cmd/upstream.go b/cmd/upstream.go
new file mode 100644
index 0000000..e7d4071
--- /dev/null
+++ b/cmd/upstream.go
@@ -0,0 +1,32 @@
+package cmd
+
+import (
+	_ "dtool/prober"
+	"dtool/utils"
+
+	"github.com/spf13/cobra"
+)
+
+var filename string
+var thread_num int
+var upstreamCmd = &cobra.Command{
+	Use: "upstream",
+	//Aliases: []string{"up", "stream"},
+	Short: "probe upstream recursive resolvers",
+	Long: `get the upstream recursive resolvers of the input resolvers
+input target can be added as an argument or as a file
+
+	-f	input file with limited ip addresses (limit=50)
+	-t	number of goroutine`,
+	Args: cobra.ExactArgs(1),
+	Run: func(cmd *cobra.Command, args []string) {
+		//prober.Get_upstream_ip(args[0])
+		utils.SendTencentHttpdnsQuery()
+	},
+}
+
+func init() {
+	upstreamCmd.Flags().StringVarP(&filename, "file", "f", "", "input filename")
+	upstreamCmd.Flags().IntVarP(&thread_num, "threads", "t", 10, "number of concurrent threads")
+	rootCmd.AddCommand(upstreamCmd)
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..c08d21e
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,15 @@
+module dtool
+
+go 1.20
+
+require github.com/spf13/cobra v1.7.0
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/miekg/dns v1.1.54 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	golang.org/x/mod v0.7.0 // indirect
+	golang.org/x/net v0.2.0 // indirect
+	golang.org/x/sys v0.2.0 // indirect
+	golang.org/x/tools v0.3.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..7fa2eff
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,20 @@
+github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/miekg/dns v1.1.54 h1:5jon9mWcb0sFJGpnI99tOMhCPyJ+RPVz5b63MQG0VWI=
+github.com/miekg/dns v1.1.54/go.mod h1:uInx36IzPl7FYnDcMeVWxj9byh7DutNykX4G9Sj60FY=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/cobra v1.7.0 h1:hyqWnYt1ZQShIddO5kBpj3vu05/++x6tJ6dg8EC572I=
+github.com/spf13/cobra v1.7.0/go.mod h1:uLxZILRyS/50WlhOIKD7W6V5bgeIt+4sICxh6uRMrb0=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+golang.org/x/mod v0.7.0 h1:LapD9S96VoQRhi/GrNTqeBJFrUjs5UHCAtTlgwA5oZA=
+golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/net v0.2.0 h1:sZfSu1wtKLGlWI4ZZayP0ck9Y73K1ynO6gqzTdBVdPU=
+golang.org/x/net v0.2.0/go.mod h1:KqCZLdyyvdV855qA2rE3GC2aiw5xGR5TEjj8smXukLY=
+golang.org/x/sys v0.2.0 h1:ljd4t30dBnAvMZaQCevtY0xLLD0A+bRZXbgLMLU1F/A=
+golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/tools v0.3.0 h1:SrNbZl6ECOS1qFzgTdQfWXZM9XBkiA6tkFrH9YSTPHM=
+golang.org/x/tools v0.3.0/go.mod h1:/rWhSS2+zyEVwoJf8YAX6L2f0ntZ7Kn/mGgAWcipA5k=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..e422189
--- /dev/null
+++ b/main.go
@@ -0,0 +1,11 @@
+/*
+Copyright © 2023 NAME HERE <EMAIL ADDRESS>
+
+*/
+package main
+
+import "dtool/cmd"
+
+func main() {
+	cmd.Execute()
+}
diff --git a/prober/rdns_prober.go b/prober/rdns_prober.go
new file mode 100644
index 0000000..08d500c
--- /dev/null
+++ b/prober/rdns_prober.go
@@ -0,0 +1,133 @@
+package prober
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"dtool/utils"
+)
+
+type Data struct {
+	target string
+	dict   map[string]bool
+}
+
+var dataset map[string][]string
+
+func retrieve_ip(pool chan string, filename string) {
+	cnt := 0
+	f, err := os.Open(filename)
+	if err != nil {
+		fmt.Printf("cannot open file %s\n", filename)
+		return
+	}
+	fmt.Println("sending msg ...")
+	reader := bufio.NewReader(f)
+	for {
+		s, err := reader.ReadString('\n')
+		if err == io.EOF {
+			break
+		}
+		s = strings.Trim(s, "\n")
+		pool <- s
+		cnt++
+		if cnt%10 == 0 {
+			fmt.Println(cnt)
+		}
+	}
+	close(pool)
+}
+
+func active_probe(n int, addr string) Data {
+	target_ip := addr[:len(addr)-3]
+	data := Data{target_ip, make(map[string]bool)}
+	stop := 0
+	timestamp := strconv.FormatInt(time.Now().Unix(), 10)
+	for i := 0; i < n; i++ {
+		subdomain := strings.Join([]string{strings.Replace(target_ip, ".", "-", -1), "echo", strconv.Itoa(i), timestamp}, "-")
+		rdns_ip, err := utils.SendQuery(addr, subdomain)
+		if err == nil {
+			data.dict[rdns_ip] = true
+		} else {
+			stop += 1
+		}
+		if stop == 3 {
+			break
+		}
+	}
+	return data
+}
+
+func upstream_prober(ip_pool chan string, data_pool chan Data, wg *sync.WaitGroup) {
+	for {
+		if s, ok := <-ip_pool; ok {
+			addr := s + ":53"
+			data := active_probe(20, addr)
+			if data.dict != nil {
+				data_pool <- data
+			}
+		} else {
+			break
+		}
+	}
+	wg.Done()
+}
+
+func create_probers(num int, ip_pool chan string, data_pool chan Data, wg *sync.WaitGroup) {
+	for i := 0; i < num; i++ {
+		wg.Add(1)
+		go upstream_prober(ip_pool, data_pool, wg)
+	}
+}
+
+func store_data(pool chan Data, wg *sync.WaitGroup) {
+	wg.Add(1)
+	for {
+		var temp []string
+		if data, ok := <-pool; ok {
+			if len(data.dict) > 0 {
+				for rdns := range data.dict {
+					temp = append(temp, rdns)
+				}
+				dataset[data.target] = temp
+			}
+		} else {
+			break
+		}
+	}
+	wg.Done()
+}
+
+func Get_upstream_file(filename string, prober_num int) {
+	dataset = map[string][]string{}
+	ip_pool := make(chan string, 500)
+	data_pool := make(chan Data, 200)
+	var probe_tasks sync.WaitGroup
+	var store_task sync.WaitGroup
+
+	go retrieve_ip(ip_pool, filename)
+	create_probers(prober_num, ip_pool, data_pool, &probe_tasks)
+	go store_data(data_pool, &store_task)
+	probe_tasks.Wait()
+	close(data_pool)
+	store_task.Wait()
+	utils.OutputJSON(dataset)
+}
+
+func Get_upstream_ip(ip string) {
+	dataset = make(map[string][]string)
+	var temp []string
+	addr := ip + ":53"
+	data := active_probe(10, addr)
+	for rdns := range data.dict {
+		temp = append(temp, rdns)
+	}
+	dataset[data.target] = temp
+	utils.OutputJSON(dataset)
+}
diff --git a/utils/dns_utils.go b/utils/dns_utils.go
new file mode 100644
index 0000000..f6d4578
--- /dev/null
+++ b/utils/dns_utils.go
@@ -0,0 +1,55 @@
+package utils
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+type WrongAnswerError struct {
+	Message string
+}
+
+func (e *WrongAnswerError) Error() string {
+	return fmt.Sprintf("Wrong Answer: %s", e.Message)
+}
+
+func SendQuery(addr string, dn string) (string, error) {
+	var (
+		domain  string
+		rdns_ip string
+	)
+	if dn == "timestamp" {
+		timestamp := strconv.FormatInt(time.Now().UnixNano(), 10)
+		domain = strings.Join([]string{timestamp, "-scan.echodns.xyz."}, "")
+	} else {
+		domain = strings.Join([]string{dn, ".echodns.xyz."}, "")
+	}
+	//fmt.Println(domain)
+	m := new(dns.Msg)
+	m.SetQuestion(domain, dns.TypeA)
+	m.RecursionDesired = true
+
+	res, err := dns.Exchange(m, addr)
+	if err == nil {
+		if len(res.Answer) == 1 {
+			if a, ok := res.Answer[0].(*dns.A); ok {
+				rdns_ip = a.A.String()
+			} else {
+				rdns_ip = ""
+				err = &WrongAnswerError{
+					Message: "Wrong Record Type",
+				}
+			}
+		} else {
+			rdns_ip = ""
+			err = &WrongAnswerError{
+				Message: "Wrong Answer Section",
+			}
+		}
+	}
+	return rdns_ip, err
+}
diff --git a/utils/httpdns_utils.go b/utils/httpdns_utils.go
new file mode 100644
index 0000000..11c891d
--- /dev/null
+++ b/utils/httpdns_utils.go
@@ -0,0 +1,112 @@
+package utils
+
+import (
+	"bytes"
+	"crypto/des"
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+)
+
+func pkcs5Padding(plaintext []byte, blocksize int) []byte {
+	padding := blocksize - len(plaintext)%blocksize
+	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
+	return append(plaintext, padtext...)
+}
+
+func pkcs5Unpadding(plaintext []byte) []byte {
+	padding := plaintext[len(plaintext)-1]
+	return plaintext[:len(plaintext)-int(padding)]
+}
+
+func encryptDES(plaintext, key []byte) ([]byte, error) {
+	block, err := des.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	blocksize := block.BlockSize()
+	plaintext = pkcs5Padding(plaintext, blocksize)
+
+	ciphertext := make([]byte, len(plaintext))
+	for i := 0; i < len(plaintext); i += blocksize {
+		block.Encrypt(ciphertext[i:], plaintext[i:i+blocksize])
+	}
+
+	return ciphertext, nil
+}
+
+func decryptDES(ciphertext, key []byte) ([]byte, error) {
+	block, err := des.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	blocksize := block.BlockSize()
+	decryptedtext := make([]byte, len(ciphertext))
+	for i := 0; i < len(ciphertext); i += blocksize {
+		block.Decrypt(decryptedtext[i:], ciphertext[i:i+blocksize])
+	}
+	decryptedtext = pkcs5Unpadding(decryptedtext)
+	return decryptedtext, nil
+}
+
+func SendTencentHttpdnsQuery() {
+	client := &http.Client{}
+	domain := []byte("echo.echodns.xyz")
+	key := []byte("046Ju3Cw")
+	encrypted_bytes, err := encryptDES(domain, key)
+	if err != nil {
+		return
+	}
+	encrypted_domain := hex.EncodeToString(encrypted_bytes)
+	url := fmt.Sprintf("http://119.29.29.98/d?dn=%s&id=61188", encrypted_domain)
+	fmt.Println(url)
+
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		fmt.Printf("create new request failed. Error: %s\n", err)
+	}
+
+	resp, err := client.Do(req)
+	if err != nil {
+		fmt.Printf("request went wrong. Error: %s\n", err)
+		return
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		fmt.Printf("read content failed. Error: %s\n", err)
+		return
+	}
+	encrypted_response, _ := hex.DecodeString(string(body))
+	decrypted_response, err := decryptDES(encrypted_response, key)
+	if err != nil {
+		return
+	}
+	fmt.Println(string(decrypted_response))
+}
+
+func SendAlicloudHttpdnsQurey() {
+	client := &http.Client{}
+	req, err := http.NewRequest("GET", "http://203.107.1.33/149702/d?host=echo.echodns.xyz", nil)
+	if err != nil {
+		fmt.Printf("create new request failed. Error: %s\n", err)
+	}
+
+	resp, err := client.Do(req)
+	if err != nil {
+		fmt.Printf("request went wrong. Error: %s\n", err)
+		return
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		fmt.Printf("read content failed. Error: %s\n", err)
+		return
+	}
+
+	fmt.Println(string(body))
+}
diff --git a/utils/output_utils.go b/utils/output_utils.go
new file mode 100644
index 0000000..88a649c
--- /dev/null
+++ b/utils/output_utils.go
@@ -0,0 +1,15 @@
+package utils
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+func OutputJSON(data map[string][]string) {
+	jsonstr, err := json.MarshalIndent(data, "", "    ")
+	if err != nil {
+		fmt.Println("JSON encoding error:", err)
+		return
+	}
+	fmt.Println(string(jsonstr))
+}