From 79bd67a6c4e0c4b69b9d47cef888e7df56dd1d8c Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Wed, 11 Jan 2023 09:53:56 +0800
Subject: [PATCH] fix: dns cache index out of range

---
 dns/util.go | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/dns/util.go b/dns/util.go
index 8259f22e..e53abab0 100644
--- a/dns/util.go
+++ b/dns/util.go
@@ -29,9 +29,11 @@ const (
 
 func putMsgToCache(c *cache.LruCache[string, *D.Msg], key string, msg *D.Msg) {
 	// skip dns cache for acme challenge
-	if q := msg.Question[0]; q.Qtype == D.TypeTXT && strings.HasPrefix(q.Name, "_acme-challenge") {
-		log.Debugln("[DNS] dns cache ignored because of acme challenge for: %s", q.Name)
-		return
+	if len(msg.Question) != 0 {
+		if q := msg.Question[0]; q.Qtype == D.TypeTXT && strings.HasPrefix(q.Name, "_acme-challenge") {
+			log.Debugln("[DNS] dns cache ignored because of acme challenge for: %s", q.Name)
+			return
+		}
 	}
 	var ttl uint32
 	switch {