1 files changed, 172 insertions, 0 deletions
diff --git a/dns-server.go b/dns-server.go
new file mode 100644
index 0000000..197a17b
--- /dev/null
+++ b/dns-server.go
@@ -0,0 +1,172 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"net"
+	"os"
+	"regexp"
+	"strings"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+type dnsMistake struct{}
+
+func (*dnsMistake) ServeDNS(w dns.ResponseWriter, r *dns.Msg) {
+	msg := dns.Msg{}
+	msg.SetReply(r)
+	switch r.Question[0].Qtype {
+	case dns.TypeA:
+		msg.Authoritative = true
+		domain := msg.Question[0].Name
+		address, ok := haveIT(domain)
+		if ok {
+			msg.Answer = append(msg.Answer, &dns.A{
+				Hdr: dns.RR_Header{Name: domain, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 60},
+				A:   net.ParseIP(address),
+			})
+		}
+	}
+	w.WriteMsg(&msg)
+}
+
+var (
+	upStrdns *string
+	upStrcon *string
+)
+
+func flushCH(name string) {
+	for {
+		<-flush
+		log.Printf("dropping memory cache .... %v recored", len(dataCH))
+		dataCH = make(map[string]string)
+		fileCheck(name)
+
+	}
+
+}
+
+func askUpstr(s string) (string, bool) {
+	r := &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			d := net.Dialer{
+				Timeout: time.Millisecond * time.Duration(10000),
+			}
+			return d.DialContext(ctx, *upStrcon, *upStrdns)
+		},
+	}
+
+	ip, err := r.LookupHost(context.Background(), s)
+	if err != nil {
+		return "err", false
+	}
+	return ip[0], true
+
+}
+
+const regIPPORT string = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]):()([1-9]|[1-5]?[0-9]{2,4}|6[1-4][0-9]{3}|65[1-4][0-9]{2}|655[1-2][0-9]|6553[1-5])$"
+const regTCPUDP string = "^(tcp|udp)$"
+const ipONLY string = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$"
+
+var dataCH = make(map[string]string)
+var fakeAdd *string
+
+func timeCh() {
+	for {
+		time.Sleep(time.Second*time.Duration(rand.Intn(120)) + 90)
+		flush <- struct{}{}
+	}
+}
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+	upStrdns = flag.String("upaddr", "1.1.1.1:53", "upsteam dns server to connect <ipaddr:port>")
+	listenAddr := flag.String("loaddr", "0.0.0.0:53", "dns server listen address <ipaddr:port>")
+	upStrcon = flag.String("upconn", "udp", "upsteam dns connection type <udp|tcp>")
+	listenCon := flag.String("loconn", "udp", "dns server connection type <udp|tcp>")
+	fakeAdd = flag.String("fakeadd", "127.0.0.1", "an ip to send back for filtered domains <ipaddr>")
+	filter := flag.String("filter", "noacc.txt", "filtered domains <filename> - regex is supported")
+
+	flag.Parse()
+	if match, _ := regexp.MatchString(regIPPORT, *upStrdns); !match {
+		flag.Usage()
+		os.Exit(1)
+	}
+	if match, _ := regexp.MatchString(ipONLY, *fakeAdd); !match {
+		flag.Usage()
+		os.Exit(1)
+	}
+	if match, _ := regexp.MatchString(regIPPORT, *listenAddr); !match {
+		flag.Usage()
+		os.Exit(1)
+	}
+	if match, _ := regexp.MatchString(regTCPUDP, *upStrcon); !match {
+		flag.Usage()
+		os.Exit(1)
+	}
+	if match, _ := regexp.MatchString(regTCPUDP, *listenCon); !match {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	fileCheck(*filter)
+	go flushCH(*filter)
+	go timeCh()
+	go memCH()
+	srv := &dns.Server{Addr: *listenAddr, Net: *listenCon}
+	srv.Handler = &dnsMistake{}
+	log.Printf("upstream dns: %v connection %v", *upStrdns, *upStrcon)
+	log.Printf("dns listen on: %v connection %v", *listenAddr, *listenCon)
+	log.Printf("load banned domains from: %v", *filter)
+	if err := srv.ListenAndServe(); err != nil {
+		log.Fatalf("fatal: failed to set udp|tcp listener %s\n", err.Error())
+	}
+}
+
+func fileCheck(name string) {
+	content, err := os.OpenFile(name, os.O_RDONLY|os.O_CREATE, 0666)
+	if err != nil {
+		log.Fatal("fatal: can not access or create the file", err.Error())
+	}
+	ready, err := ioutil.ReadAll(content)
+	if err != nil {
+		log.Fatal("fatal: unknow error", err.Error())
+	}
+	stringArr := strings.Fields(string(ready))
+	for _, v := range stringArr {
+		dataCH[v] = *fakeAdd
+	}
+
+}
+
+var flush = make(chan struct{})
+
+func haveIT(domain string) (string, bool) {
+	for k, v := range dataCH {
+		if ok, _ := regexp.MatchString(k, domain); ok {
+			return v, true
+		}
+	}
+
+	if addr, ok := askUpstr(domain); ok {
+		dataCH[domain] = addr
+		return addr, true
+	}
+	return "err", false
+}
+
+func memCH() {
+	for {
+		time.Sleep(time.Millisecond * 100)
+		if len(dataCH) > 900000 {
+			flush <- struct{}{}
+		}
+
+	}
+}