From 7cea5305e1377b8e26e14deccaf789c334dcd237 Mon Sep 17 00:00:00 2001
From: Cuong Manh Le <cuong@windscribe.com>
Date: Tue, 10 Jun 2025 19:13:46 +0700
Subject: [PATCH] all: fix a regression causing invalid reloading timeout

In v1.4.3, ControlD bootstrap DNS is used again for bootstrapping
process. When this happened, the default system nameservers will be
retrieved first, then ControlD DNS will be used if none available.

However, getting default system nameservers process may take longer than
reloading command timeout, causing invalid error message printed.

To fix this, ensuring default system nameservers is retrieved once.
---
 resolver.go | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/resolver.go b/resolver.go
index c20f1f5..27c0108 100644
--- a/resolver.go
+++ b/resolver.go
@@ -542,11 +542,26 @@ func (d dummyResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, err
 // LookupIP looks up domain using current system nameservers settings.
 // It returns a slice of that host's IPv4 and IPv6 addresses.
 func LookupIP(domain string) []string {
-	return lookupIP(domain, -1, defaultNameservers())
+	nss := initDefaultOsResolver()
+	return lookupIP(domain, -1, nss)
+}
+
+// initDefaultOsResolver initializes the default OS resolver with system's default nameservers if it hasn't been initialized yet.
+// It returns the combined list of LAN and public nameservers currently held by the resolver.
+func initDefaultOsResolver() []string {
+	resolverMutex.Lock()
+	defer resolverMutex.Unlock()
+	if or == nil {
+		ProxyLogger.Load().Debug().Msgf("Initialize new OS resolver with default nameservers")
+		or = newResolverWithNameserver(defaultNameservers())
+	}
+	nss := *or.lanServers.Load()
+	nss = append(nss, *or.publicServers.Load()...)
+	return nss
 }
 
 // lookupIP looks up domain with given timeout and bootstrapDNS.
-// If timeout is negative, default timeout 2000 ms will be used.
+// If the timeout is negative, default timeout 2000 ms will be used.
 // It returns nil if bootstrapDNS is nil or empty.
 func lookupIP(domain string, timeout int, bootstrapDNS []string) (ips []string) {
 	if net.ParseIP(domain) != nil {
@@ -650,13 +665,7 @@ func NewBootstrapResolver(servers ...string) Resolver {
 //
 // This is useful for doing PTR lookup in LAN network.
 func NewPrivateResolver() Resolver {
-	resolverMutex.Lock()
-	if or == nil {
-		ProxyLogger.Load().Debug().Msgf("Initialize new OS resolver in NewPrivateResolver")
-		or = newResolverWithNameserver(defaultNameservers())
-	}
-	nss := *or.lanServers.Load()
-	resolverMutex.Unlock()
+	nss := initDefaultOsResolver()
 	resolveConfNss := currentNameserversFromResolvconf()
 	localRfc1918Addrs := Rfc1918Addresses()
 	n := 0