From c4b2236cf9ac6cdf9e8e08991efc407b225a77b3 Mon Sep 17 00:00:00 2001
From: Star Brilliant <coder@poorlab.com>
Date: Thu, 26 Apr 2018 10:17:14 +0800
Subject: [PATCH] Do not respond to network error, silently fail to prevent
 caching of SERVFAIL

Hopefully we can improve the availability of DoH under unstable network environments.
---
 doh-client/doh-client.conf | 2 +-
 doh-client/ietf.go         | 6 ++----
 doh-client/version.go      | 6 ++++--
 doh-server/version.go      | 6 ++++--
 4 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/doh-client/doh-client.conf b/doh-client/doh-client.conf
index 413b490..7d67ca7 100644
--- a/doh-client/doh-client.conf
+++ b/doh-client/doh-client.conf
@@ -47,7 +47,7 @@ bootstrap = [
 ]
 
 # Timeout for upstream request
-timeout = 10
+timeout = 30
 
 # Disable HTTP Cookies
 #
diff --git a/doh-client/ietf.go b/doh-client/ietf.go
index bc4e625..5615737 100644
--- a/doh-client/ietf.go
+++ b/doh-client/ietf.go
@@ -134,9 +134,8 @@ func (c *Client) generateRequestIETF(w dns.ResponseWriter, r *dns.Msg, isTCP boo
 	if len(requestURL) < 2048 {
 		req, err = http.NewRequest("GET", requestURL, nil)
 		if err != nil {
+			// Do not respond, silently fail to prevent caching of SERVFAIL
 			log.Println(err)
-			reply.Rcode = dns.RcodeServerFailure
-			w.WriteMsg(reply)
 			return &DNSRequest{
 				err: err,
 			}
@@ -144,9 +143,8 @@ func (c *Client) generateRequestIETF(w dns.ResponseWriter, r *dns.Msg, isTCP boo
 	} else {
 		req, err = http.NewRequest("POST", upstream, bytes.NewReader(requestBinary))
 		if err != nil {
+			// Do not respond, silently fail to prevent caching of SERVFAIL
 			log.Println(err)
-			reply.Rcode = dns.RcodeServerFailure
-			w.WriteMsg(reply)
 			return &DNSRequest{
 				err: err,
 			}
diff --git a/doh-client/version.go b/doh-client/version.go
index 1a90665..9edb98b 100644
--- a/doh-client/version.go
+++ b/doh-client/version.go
@@ -23,5 +23,7 @@
 
 package main
 
-const VERSION = "1.3.3"
-const USER_AGENT = "DNS-over-HTTPS/" + VERSION + " (+https://github.com/m13253/dns-over-https)"
+const (
+	VERSION    = "1.3.3"
+	USER_AGENT = "DNS-over-HTTPS/" + VERSION + " (+https://github.com/m13253/dns-over-https)"
+)
diff --git a/doh-server/version.go b/doh-server/version.go
index 1a90665..9edb98b 100644
--- a/doh-server/version.go
+++ b/doh-server/version.go
@@ -23,5 +23,7 @@
 
 package main
 
-const VERSION = "1.3.3"
-const USER_AGENT = "DNS-over-HTTPS/" + VERSION + " (+https://github.com/m13253/dns-over-https)"
+const (
+	VERSION    = "1.3.3"
+	USER_AGENT = "DNS-over-HTTPS/" + VERSION + " (+https://github.com/m13253/dns-over-https)"
+)