From 4e68b6cd3d7c7e4cbc5f71ef78cbf06414486f4f Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Thu, 1 Apr 2021 18:03:30 +0800
Subject: [PATCH] Fix: don't resolve AAAA record when ipv6 is false and use go
 dns resolver

---
 component/resolver/resolver.go | 33 +++++++++++++++++----------------
 dns/resolver.go                |  2 +-
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/component/resolver/resolver.go b/component/resolver/resolver.go
index 61258898..356bc660 100644
--- a/component/resolver/resolver.go
+++ b/component/resolver/resolver.go
@@ -1,9 +1,11 @@
 package resolver
 
 import (
+	"context"
 	"errors"
 	"net"
 	"strings"
+	"time"
 
 	"github.com/Dreamacro/clash/component/trie"
 )
@@ -18,6 +20,9 @@ var (
 
 	// DefaultHosts aim to resolve hosts
 	DefaultHosts = trie.New()
+
+	// DefaultDNSTimeout defined the default dns request timeout
+	DefaultDNSTimeout = time.Second * 5
 )
 
 var (
@@ -52,18 +57,16 @@ func ResolveIPv4(host string) (net.IP, error) {
 		return DefaultResolver.ResolveIPv4(host)
 	}
 
-	ipAddrs, err := net.LookupIP(host)
+	ctx, cancel := context.WithTimeout(context.Background(), DefaultDNSTimeout)
+	defer cancel()
+	ipAddrs, err := net.DefaultResolver.LookupIP(ctx, "ip4", host)
 	if err != nil {
 		return nil, err
+	} else if len(ipAddrs) == 0 {
+		return nil, ErrIPNotFound
 	}
 
-	for _, ip := range ipAddrs {
-		if ip4 := ip.To4(); ip4 != nil {
-			return ip4, nil
-		}
-	}
-
-	return nil, ErrIPNotFound
+	return ipAddrs[0], nil
 }
 
 // ResolveIPv6 with a host, return ipv6
@@ -90,18 +93,16 @@ func ResolveIPv6(host string) (net.IP, error) {
 		return DefaultResolver.ResolveIPv6(host)
 	}
 
-	ipAddrs, err := net.LookupIP(host)
+	ctx, cancel := context.WithTimeout(context.Background(), DefaultDNSTimeout)
+	defer cancel()
+	ipAddrs, err := net.DefaultResolver.LookupIP(ctx, "ip6", host)
 	if err != nil {
 		return nil, err
+	} else if len(ipAddrs) == 0 {
+		return nil, ErrIPNotFound
 	}
 
-	for _, ip := range ipAddrs {
-		if ip.To4() == nil {
-			return ip, nil
-		}
-	}
-
-	return nil, ErrIPNotFound
+	return ipAddrs[0], nil
 }
 
 // ResolveIP with a host, return ip
diff --git a/dns/resolver.go b/dns/resolver.go
index d110aa34..0db6855d 100644
--- a/dns/resolver.go
+++ b/dns/resolver.go
@@ -145,7 +145,7 @@ func (r *Resolver) exchangeWithoutCache(m *D.Msg) (msg *D.Msg, err error) {
 }
 
 func (r *Resolver) batchExchange(clients []dnsClient, m *D.Msg) (msg *D.Msg, err error) {
-	fast, ctx := picker.WithTimeout(context.Background(), time.Second*5)
+	fast, ctx := picker.WithTimeout(context.Background(), resolver.DefaultDNSTimeout)
 	for _, client := range clients {
 		r := client
 		fast.Go(func() (interface{}, error) {