feat: DNS. Add the ability to disable version 6 address resolution (#240

)

Co-authored-by: Andrey Semenov <[email protected]>

dns/dns.go

@@ -26,18 +26,25 @@ type Dns struct {
 	systemClient  Resolver
 	generalClient Resolver
 	dohClient     Resolver
+	qTypes        []uint16
 }
 
 func NewDns(config *util.Config) *Dns {
 	addr := config.DnsAddr
 	port := strconv.Itoa(config.DnsPort)
-
+	var qTypes []uint16
+	if config.DnsIPv4Only {
+		qTypes = []uint16{dns.TypeA}
+	} else {
+		qTypes = []uint16{dns.TypeAAAA, dns.TypeA}
+	}
 	return &Dns{
 		host:          config.DnsAddr,
 		port:          port,
 		systemClient:  resolver.NewSystemResolver(),
 		generalClient: resolver.NewGeneralResolver(net.JoinHostPort(addr, port)),
 		dohClient:     resolver.NewDOHResolver(addr),
+		qTypes:        qTypes,
 	}
 }
 
@@ -57,7 +64,7 @@ func (d *Dns) ResolveHost(ctx context.Context, host string, enableDoh bool, useS
 
 	t := time.Now()
 
-	addrs, err := clt.Resolve(ctx, host, []uint16{dns.TypeAAAA, dns.TypeA})
+	addrs, err := clt.Resolve(ctx, host, d.qTypes)
 	// addrs, err := clt.Resolve(ctx, host, []uint16{dns.TypeAAAA})
 	if err != nil {
 		return "", fmt.Errorf("%s: %w", clt, err)

util/args.go

@@ -13,6 +13,7 @@ type Args struct {
 	Port           uint16
 	DnsAddr        string
 	DnsPort        uint16
+	DnsIPv4Only    bool
 	EnableDoh      bool
 	Debug          bool
 	Silent         bool
@@ -57,6 +58,7 @@ fragmentation for the first data packet and the rest
 		"pattern",
 		"bypass DPI only on packets matching this regex pattern; can be given multiple times",
 	)
+	flag.BoolVar(&args.DnsIPv4Only, "dns-ipv4-only", false, "resolve only version 4 addresses")
 
 	flag.Parse()
 

util/config.go

@@ -13,6 +13,7 @@ type Config struct {
 	Port            int
 	DnsAddr         string
 	DnsPort         int
+	DnsIPv4Only     bool
 	EnableDoh       bool
 	Debug           bool
 	Silent          bool
@@ -36,6 +37,7 @@ func (c *Config) Load(args *Args) {
 	c.Port = int(args.Port)
 	c.DnsAddr = args.DnsAddr
 	c.DnsPort = int(args.DnsPort)
+	c.DnsIPv4Only = args.DnsIPv4Only
 	c.Debug = args.Debug
 	c.EnableDoh = args.EnableDoh
 	c.Silent = args.Silent