Add BlockIP dns responder, update ZeroIP responder

nameserver/nameserver.go

@@ -197,7 +197,7 @@ func handleRequest(ctx context.Context, w dns.ResponseWriter, request *dns.Msg)
 			return reply(nsutil.NxDomain("nxdomain: " + err.Error()))
 		case errors.Is(err, resolver.ErrBlocked):
 			tracer.Tracef("nameserver: %s", err)
-			return reply(nsutil.ZeroIP("blocked: " + err.Error()))
+			return reply(nsutil.BlockIP("blocked: " + err.Error()))
 		case errors.Is(err, resolver.ErrLocalhost):
 			tracer.Tracef("nameserver: returning localhost records")
 			return reply(nsutil.Localhost())

nameserver/nsutil/nsutil.go

@@ -45,50 +45,42 @@ func (rf ResponderFunc) ReplyWithDNS(ctx context.Context, request *dns.Msg) *dns
 	return rf(ctx, request)
 }
 
+// BlockIP is a ResponderFunc than replies with either 0.0.0.17 or ::17 for
+// each A or AAAA question respectively. If there is no A or AAAA question, it
+// defaults to replying with NXDomain.
+func BlockIP(msgs ...string) ResponderFunc {
+	return createResponderFunc(
+		"blocking",
+		"0.0.0.17",
+		"::17",
+		msgs...,
+	)
+}
+
 // ZeroIP is a ResponderFunc than replies with either 0.0.0.0 or :: for each A
 // or AAAA question respectively. If there is no A or AAAA question, it
 // defaults to replying with NXDomain.
 func ZeroIP(msgs ...string) ResponderFunc {
-	return func(ctx context.Context, request *dns.Msg) *dns.Msg {
+	return createResponderFunc(
-		reply := new(dns.Msg)
+		"zero ip",
-		hasErr := false
+		"0.0.0.0",
-
+		"::",
-		for _, question := range request.Question {
+		msgs...,
-			var rr dns.RR
+	)
-			var err error
-
-			switch question.Qtype {
-			case dns.TypeA:
-				rr, err = dns.NewRR(question.Name + " 1 IN A 0.0.0.17")
-			case dns.TypeAAAA:
-				rr, err = dns.NewRR(question.Name + " 1 IN AAAA ::17")
-			}
-
-			switch {
-			case err != nil:
-				log.Tracer(ctx).Errorf("nameserver: failed to create zero-ip response for %s: %s", question.Name, err)
-				hasErr = true
-			case rr != nil:
-				reply.Answer = append(reply.Answer, rr)
-			}
-		}
-
-		switch {
-		case hasErr || len(reply.Answer) == 0:
-			reply.SetRcode(request, dns.RcodeServerFailure)
-		default:
-			reply.SetRcode(request, dns.RcodeSuccess)
-		}
-
-		AddMessagesToReply(ctx, reply, log.InfoLevel, msgs...)
-
-		return reply
-	}
 }
 
 // Localhost is a ResponderFunc than replies with localhost IP addresses.
 // If there is no A or AAAA question, it defaults to replying with NXDomain.
 func Localhost(msgs ...string) ResponderFunc {
+	return createResponderFunc(
+		"localhost",
+		"127.0.0.1",
+		"::1",
+		msgs...,
+	)
+}
+
+func createResponderFunc(responderName, aAnswer, aaaaAnswer string, msgs ...string) ResponderFunc {
 	return func(ctx context.Context, request *dns.Msg) *dns.Msg {
 		reply := new(dns.Msg)
 		hasErr := false
@@ -99,14 +91,14 @@ func Localhost(msgs ...string) ResponderFunc {
 
 			switch question.Qtype {
 			case dns.TypeA:
-				rr, err = dns.NewRR("localhost. 1 IN A 127.0.0.1")
+				rr, err = dns.NewRR(question.Name + " 1 IN A " + aAnswer)
 			case dns.TypeAAAA:
-				rr, err = dns.NewRR("localhost. 1 IN AAAA ::1")
+				rr, err = dns.NewRR(question.Name + " 1 IN AAAA " + aaaaAnswer)
 			}
 
 			switch {
 			case err != nil:
-				log.Tracer(ctx).Errorf("nameserver: failed to create localhost response for %s: %s", question.Name, err)
+				log.Tracer(ctx).Errorf("nameserver: failed to create %s response for %s: %s", responderName, question.Name, err)
 				hasErr = true
 			case rr != nil:
 				reply.Answer = append(reply.Answer, rr)
@@ -114,8 +106,10 @@ func Localhost(msgs ...string) ResponderFunc {
 		}
 
 		switch {
-		case hasErr || len(reply.Answer) == 0:
+		case hasErr && len(reply.Answer) == 0:
 			reply.SetRcode(request, dns.RcodeServerFailure)
+		case len(reply.Answer) == 0:
+			reply.SetRcode(request, dns.RcodeNameError)
 		default:
 			reply.SetRcode(request, dns.RcodeSuccess)
 		}

network/dns.go

@@ -103,11 +103,11 @@ func (conn *Connection) ReplyWithDNS(ctx context.Context, request *dns.Msg) *dns
 	// Select request responder.
 	switch conn.Verdict {
 	case VerdictBlock:
-		return nsutil.ZeroIP().ReplyWithDNS(ctx, request)
+		return nsutil.BlockIP().ReplyWithDNS(ctx, request)
 	case VerdictDrop:
 		return nil // Do not respond to request.
 	case VerdictFailed:
-		return nsutil.ZeroIP().ReplyWithDNS(ctx, request)
+		return nsutil.BlockIP().ReplyWithDNS(ctx, request)
 	default:
 		reply := nsutil.ServerFailure().ReplyWithDNS(ctx, request)
 		nsutil.AddMessagesToReply(ctx, reply, log.ErrorLevel, "INTERNAL ERROR: incorrect use of Connection DNS Responder")