Feature/dns-server (#537)

Adding DNS server for client

Updated the API with new fields

Added custom zone object for peer's DNS resolution

client/internal/dns/local_test.go

@@ -0,0 +1,86 @@
+package dns
+
+import (
+	"github.com/miekg/dns"
+	nbdns "github.com/netbirdio/netbird/dns"
+	"strings"
+	"testing"
+)
+
+func TestLocalResolver_ServeDNS(t *testing.T) {
+	recordA := nbdns.SimpleRecord{
+		Name:  "peera.netbird.cloud.",
+		Type:  1,
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "1.2.3.4",
+	}
+
+	recordCNAME := nbdns.SimpleRecord{
+		Name:  "peerb.netbird.cloud.",
+		Type:  5,
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "www.netbird.io",
+	}
+
+	testCases := []struct {
+		name                string
+		inputRecord         nbdns.SimpleRecord
+		inputMSG            *dns.Msg
+		responseShouldBeNil bool
+	}{
+		{
+			name:        "Should Resolve A Record",
+			inputRecord: recordA,
+			inputMSG:    new(dns.Msg).SetQuestion(recordA.Name, dns.TypeA),
+		},
+		{
+			name:        "Should Resolve CNAME Record",
+			inputRecord: recordCNAME,
+			inputMSG:    new(dns.Msg).SetQuestion(recordCNAME.Name, dns.TypeCNAME),
+		},
+		{
+			name:                "Should Not Write When Not Found A Record",
+			inputRecord:         recordA,
+			inputMSG:            new(dns.Msg).SetQuestion("not.found.com", dns.TypeA),
+			responseShouldBeNil: true,
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			resolver := &localResolver{
+				registeredMap: make(registrationMap),
+			}
+			_ = resolver.registerRecord(testCase.inputRecord)
+			var responseMSG *dns.Msg
+			responseWriter := &mockResponseWriter{
+				WriteMsgFunc: func(m *dns.Msg) error {
+					responseMSG = m
+					return nil
+				},
+			}
+
+			resolver.ServeDNS(responseWriter, testCase.inputMSG)
+
+			if responseMSG == nil {
+				if testCase.responseShouldBeNil {
+					return
+				}
+				t.Fatalf("should write a response message")
+			}
+
+			answerString := responseMSG.Answer[0].String()
+			if !strings.Contains(answerString, testCase.inputRecord.Name) {
+				t.Fatalf("answer doesn't contain the same domain name: \nWant: %s\nGot:%s", testCase.name, answerString)
+			}
+			if !strings.Contains(answerString, dns.Type(testCase.inputRecord.Type).String()) {
+				t.Fatalf("answer doesn't contain the correct type: \nWant: %s\nGot:%s", dns.Type(testCase.inputRecord.Type).String(), answerString)
+			}
+			if !strings.Contains(answerString, testCase.inputRecord.RData) {
+				t.Fatalf("answer doesn't contain the same address: \nWant: %s\nGot:%s", testCase.inputRecord.RData, answerString)
+			}
+		})
+	}
+}