use custom resolver for always 1.1.1.1 dns

server.go

@@ -15,20 +15,37 @@ import (
 
 type Server struct {
 	Transport http.RoundTripper
+	resolver  *net.Resolver
 	limiter   *rate.Limiter
 	Timeout   time.Duration
 }
 
 func NewServer(c *Config) *Server {
+	resolver := &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			d := net.Dialer{Timeout: time.Second * 10}
+			return d.DialContext(ctx, network, "1.1.1.1:53")
+		},
+	}
 	transport := &http.Transport{}
 	transport.TLSClientConfig = &tls.Config{
 		InsecureSkipVerify: c.TLSInsecure,
 	}
-	return &Server{
+	s := &Server{
 		limiter:   c.Limiter,
 		Transport: transport,
 		Timeout:   c.Timeout,
+		resolver:  resolver,
 	}
+	transport.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+		addr, err := s.dig(ctx, addr)
+		if err != nil {
+			return nil, err
+		}
+		return (&net.Dialer{}).DialContext(ctx, network, addr)
+	}
+	return s
 }
 
 func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -48,7 +65,13 @@ func (s *Server) Error(w http.ResponseWriter, err error) {
 }
 
 func (s *Server) Connect(w http.ResponseWriter, r *http.Request) {
-	dest, err := net.DialTimeout("tcp", r.Host, 30*time.Second)
+	host, err := s.dig(r.Context(), r.Host)
+	if err != nil {
+		s.Error(w, err)
+		return
+	}
+
+	dest, err := net.DialTimeout("tcp", host, 30*time.Second)
 	if err != nil {
 		s.Error(w, err)
 		return
@@ -81,7 +104,7 @@ func (s *Server) Serve(w http.ResponseWriter, r *http.Request) {
 	defer resp.Body.Close()
 
 	for k, v := range resp.Header {
-		log.Println(k, v)
+		//log.Println(k, v)
 		for _, s := range v {
 			w.Header().Add(k, s)
 		}
@@ -101,3 +124,19 @@ func (s *Server) xfer(ctx context.Context, w io.Writer, r io.ReadCloser) {
 		r,
 	)
 }
+
+func (s *Server) dig(ctx context.Context, host string) (string, error) {
+	port := ""
+	if splithost, splitport, err := net.SplitHostPort(host); err == nil {
+		host = splithost
+		port = ":" + splitport
+	}
+	ip, err := s.resolver.LookupHost(ctx, host)
+	if err != nil {
+		return "", err
+	}
+	if len(ip) == 0 {
+		return "", errors.New("name does not resolve")
+	}
+	return ip[0] + port, nil
+}