From a64df3f0487069c0af532075dacc203ce4e8121d Mon Sep 17 00:00:00 2001
From: Star Brilliant <coder@poorlab.com>
Date: Mon, 2 Jul 2018 13:49:59 +0800
Subject: [PATCH] Preserve TransactionID

---
 doh-server/ietf.go   | 8 +++++---
 doh-server/server.go | 1 +
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/doh-server/ietf.go b/doh-server/ietf.go
index 25c2f8a..9ca39f3 100644
--- a/doh-server/ietf.go
+++ b/doh-server/ietf.go
@@ -95,6 +95,7 @@ func (s *Server) parseRequestIETF(w http.ResponseWriter, r *http.Request) *DNSRe
 		fmt.Printf("%s - - [%s] \"%s %s %s\"\n", r.RemoteAddr, time.Now().Format("02/Jan/2006:15:04:05 -0700"), questionName, questionClass, questionType)
 	}
 
+	transactionID := msg.Id
 	msg.Id = dns.Id()
 	opt := msg.IsEdns0()
 	if opt == nil {
@@ -137,14 +138,15 @@ func (s *Server) parseRequestIETF(w http.ResponseWriter, r *http.Request) *DNSRe
 	}
 
 	return &DNSRequest{
-		request:    msg,
-		isTailored: isTailored,
+		request:       msg,
+		transactionID: transactionID,
+		isTailored:    isTailored,
 	}
 }
 
 func (s *Server) generateResponseIETF(w http.ResponseWriter, r *http.Request, req *DNSRequest) {
 	respJSON := jsonDNS.Marshal(req.response)
-	req.response.Id = 0
+	req.response.Id = req.transactionID
 	respBytes, err := req.response.Pack()
 	if err != nil {
 		log.Println(err)
diff --git a/doh-server/server.go b/doh-server/server.go
index 404a8cb..0de19e4 100644
--- a/doh-server/server.go
+++ b/doh-server/server.go
@@ -48,6 +48,7 @@ type Server struct {
 type DNSRequest struct {
 	request         *dns.Msg
 	response        *dns.Msg
+	transactionID   uint16
 	currentUpstream string
 	isTailored      bool
 	errcode         int