add dnsserver

dns/dnsserver.go

@@ -0,0 +1,66 @@
+package dns
+
+import (
+	"fmt"
+	miekgdns "github.com/miekg/dns"
+	log "github.com/sirupsen/logrus"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/cache"
+	"strings"
+)
+
+type server struct {
+	// todo using cache to speed up dns resolve process
+	dnsCache   *cache.LRUExpireCache
+	forwardDNS string
+	namespace  string
+}
+
+func NewDNSServer(network, address, forwardDNS, namespace string) error {
+	if len(namespace) == 0 {
+		namespace = v1.NamespaceDefault
+	}
+	return miekgdns.ListenAndServe(address, network, &server{
+		dnsCache: cache.NewLRUExpireCache(1000), forwardDNS: forwardDNS, namespace: namespace,
+	})
+}
+
+// ServeDNS consider using a cache
+func (s *server) ServeDNS(w miekgdns.ResponseWriter, r *miekgdns.Msg) {
+	q := r.Question
+	r.Question = make([]miekgdns.Question, 0, len(q))
+	question := q[0]
+	name := question.Name
+	switch strings.Count(question.Name, ".") {
+	case 1:
+		question.Name = question.Name + s.namespace + ".svc.cluster.local."
+	case 2:
+		question.Name = question.Name + "svc.cluster.local."
+	case 3:
+		question.Name = question.Name + "cluster.local."
+	case 4:
+		question.Name = question.Name + "local."
+	case 5:
+	}
+	r.Question = []miekgdns.Question{question}
+	fmt.Println(r.Question)
+	answer, err := miekgdns.Exchange(r, s.forwardDNS)
+	if err != nil {
+		log.Warnln(err)
+		err = w.WriteMsg(r)
+		if err != nil {
+			log.Warnln(err)
+		}
+	} else {
+		if len(answer.Answer) != 0 {
+			answer.Answer[0].Header().Name = name
+		}
+		if len(answer.Question) != 0 {
+			answer.Question[0].Name = name
+		}
+		err = w.WriteMsg(answer)
+		if err != nil {
+			log.Warnln(err)
+		}
+	}
+}

dns/dnsserver_test.go

@@ -0,0 +1,16 @@
+package dns
+
+import (
+	log "github.com/sirupsen/logrus"
+	"strconv"
+	"testing"
+)
+
+func TestName(t *testing.T) {
+	//port := util.GetAvailableUDPPortOrDie()
+	port := 58477
+	err := NewDNSServer("udp", "127.0.0.1:"+strconv.Itoa(port), "172.20.135.131:53", "test")
+	if err != nil {
+		log.Warnln(err)
+	}
+}

util/util.go

@@ -104,6 +104,19 @@ func GetAvailablePortOrDie() int {
 	return listener.Addr().(*net.TCPAddr).Port
 }
 
+func GetAvailableUDPPortOrDie() int {
+	address, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:0", "0.0.0.0"))
+	if err != nil {
+		log.Fatal(err)
+	}
+	listener, err := net.ListenUDP("udp", address)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer listener.Close()
+	return listener.LocalAddr().(*net.UDPAddr).Port
+}
+
 func WaitPod(clientset *kubernetes.Clientset, namespace string, list metav1.ListOptions, checker func(*v1.Pod) bool) error {
 	return WaitResource(
 		clientset,