From 45ca063a7e0678ab32ba209164abc649945d56e6 Mon Sep 17 00:00:00 2001
From: wweir <wweir@foxmail.com>
Date: Tue, 19 Mar 2019 13:29:06 +0800
Subject: [PATCH] Add timeout for dns exchange

---
 dns/dns.go | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/dns/dns.go b/dns/dns.go
index 7027937..0de3fb9 100644
--- a/dns/dns.go
+++ b/dns/dns.go
@@ -1,6 +1,7 @@
 package dns
 
 import (
+	"context"
 	"net"
 	"strings"
 	"sync/atomic"
@@ -73,7 +74,10 @@ func matchAndServe(w dns.ResponseWriter, r *dns.Msg, domain, listenIP, dnsServer
 		return
 	}
 
-	msg, err := dns.Exchange(r, dnsServer)
+	ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
+	defer cancel()
+
+	msg, err := dns.ExchangeContext(ctx, r, dnsServer)
 	if err != nil {
 		if dhcpCh != nil {
 			select {
@@ -81,9 +85,10 @@ func matchAndServe(w dns.ResponseWriter, r *dns.Msg, domain, listenIP, dnsServer
 			default:
 			}
 		}
+		glog.V(1).Infof("get dns of %s fail: %s", domain, err)
 		return
 	} else if msg == nil { // expose any response except nil
-		glog.V(1).Infof("get dns of %s fail: %s", domain, err)
+		glog.V(1).Infof("get dns of %s return empty", domain)
 		return
 	}