From c4994d642963c825b1070dc19d63511bbe536fc8 Mon Sep 17 00:00:00 2001
From: Dreamacro <305009791@qq.com>
Date: Tue, 25 Feb 2020 21:51:48 +0800
Subject: [PATCH] Fix: dns not cache RcodeServerFailure

---
 dns/resolver.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/dns/resolver.go b/dns/resolver.go
index fefdafdc..b6dfc733 100644
--- a/dns/resolver.go
+++ b/dns/resolver.go
@@ -168,7 +168,13 @@ func (r *Resolver) batchExchange(clients []dnsClient, m *D.Msg) (msg *D.Msg, err
 	for _, client := range clients {
 		r := client
 		fast.Go(func() (interface{}, error) {
-			return r.ExchangeContext(ctx, m)
+			m, err := r.ExchangeContext(ctx, m)
+			if err != nil {
+				return nil, err
+			} else if m.Rcode == D.RcodeServerFailure {
+				return nil, errors.New("server failure")
+			}
+			return m, nil
 		})
 	}