feat: add queryStrategy option for DNS

features/dns/client.go

@@ -21,7 +21,35 @@ type Client interface {
 	features.Feature
 
 	// LookupIP returns IP address for the given domain. IPs may contain IPv4 and/or IPv6 addresses.
-	LookupIP(domain string, option IPOption) ([]net.IP, error)
+	LookupIP(domain string) ([]net.IP, error)
+}
+
+// IPv4Lookup is an optional feature for querying IPv4 addresses only.
+//
+// xray:api:beta
+type IPv4Lookup interface {
+	LookupIPv4(domain string) ([]net.IP, error)
+}
+
+// IPv6Lookup is an optional feature for querying IPv6 addresses only.
+//
+// xray:api:beta
+type IPv6Lookup interface {
+	LookupIPv6(domain string) ([]net.IP, error)
+}
+
+// ClientWithIPOption is an optional feature for querying DNS information.
+//
+// xray:api:beta
+type ClientWithIPOption interface {
+	// GetIPOption returns IPOption for the DNS client.
+	GetIPOption() *IPOption
+
+	// SetQueryOption sets IPv4Enable and IPv6Enable for the DNS client.
+	SetQueryOption(isIPv4Enable, isIPv6Enable bool)
+
+	// SetFakeDNSOption sets FakeEnable option for DNS client.
+	SetFakeDNSOption(isFakeEnable bool)
 }
 
 // ClientType returns the type of Client interface. Can be used for implementing common.HasType.

features/dns/localdns/client.go

@@ -20,41 +20,59 @@ func (*Client) Start() error { return nil }
 func (*Client) Close() error { return nil }
 
 // LookupIP implements Client.
-func (*Client) LookupIP(host string, option dns.IPOption) ([]net.IP, error) {
+func (*Client) LookupIP(host string) ([]net.IP, error) {
 	ips, err := net.LookupIP(host)
 	if err != nil {
 		return nil, err
 	}
 	parsedIPs := make([]net.IP, 0, len(ips))
-	ipv4 := make([]net.IP, 0, len(ips))
-	ipv6 := make([]net.IP, 0, len(ips))
 	for _, ip := range ips {
 		parsed := net.IPAddress(ip)
 		if parsed != nil {
 			parsedIPs = append(parsedIPs, parsed.IP())
 		}
+	}
+	if len(parsedIPs) == 0 {
+		return nil, dns.ErrEmptyResponse
+	}
+	return parsedIPs, nil
+}
+
+// LookupIPv4 implements IPv4Lookup.
+func (c *Client) LookupIPv4(host string) ([]net.IP, error) {
+	ips, err := c.LookupIP(host)
+	if err != nil {
+		return nil, err
+	}
+	ipv4 := make([]net.IP, 0, len(ips))
+	for _, ip := range ips {
 		if len(ip) == net.IPv4len {
 			ipv4 = append(ipv4, ip)
 		}
+	}
+	if len(ipv4) == 0 {
+		return nil, dns.ErrEmptyResponse
+	}
+	return ipv4, nil
+}
+
+// LookupIPv6 implements IPv6Lookup.
+func (c *Client) LookupIPv6(host string) ([]net.IP, error) {
+	ips, err := c.LookupIP(host)
+	if err != nil {
+		return nil, err
+	}
+	ipv6 := make([]net.IP, 0, len(ips))
+	for _, ip := range ips {
 		if len(ip) == net.IPv6len {
 			ipv6 = append(ipv6, ip)
 		}
 	}
-	switch {
-	case option.IPv4Enable && option.IPv6Enable:
-		if len(parsedIPs) > 0 {
-			return parsedIPs, nil
-		}
-	case option.IPv4Enable:
-		if len(ipv4) > 0 {
-			return ipv4, nil
-		}
-	case option.IPv6Enable:
-		if len(ipv6) > 0 {
-			return ipv6, nil
-		}
+	if len(ipv6) == 0 {
+		return nil, dns.ErrEmptyResponse
 	}
-	return nil, dns.ErrEmptyResponse
+
+	return ipv6, nil
 }
 
 // New create a new dns.Client that queries localhost for DNS.

features/routing/dns/context.go

@@ -26,11 +26,35 @@ func (ctx *ResolvableContext) GetTargetIPs() []net.IP {
 	}
 
 	if domain := ctx.GetTargetDomain(); len(domain) != 0 {
-		ips, err := ctx.dnsClient.LookupIP(domain, dns.IPOption{
+		var lookupFunc func(string) ([]net.IP, error) = ctx.dnsClient.LookupIP
+		ipOption := &dns.IPOption{
 			IPv4Enable: true,
 			IPv6Enable: true,
-			FakeEnable: false,
-		})
+		}
+
+		if c, ok := ctx.dnsClient.(dns.ClientWithIPOption); ok {
+			ipOption = c.GetIPOption()
+			c.SetFakeDNSOption(false) // Skip FakeDNS.
+		} else {
+			newError("ctx.dnsClient doesn't implement ClientWithIPOption").AtDebug().WriteToLog()
+		}
+
+		switch {
+		case ipOption.IPv4Enable && !ipOption.IPv6Enable:
+			if lookupIPv4, ok := ctx.dnsClient.(dns.IPv4Lookup); ok {
+				lookupFunc = lookupIPv4.LookupIPv4
+			} else {
+				newError("ctx.dnsClient doesn't implement IPv4Lookup. Use LookupIP instead.").AtDebug().WriteToLog()
+			}
+		case !ipOption.IPv4Enable && ipOption.IPv6Enable:
+			if lookupIPv6, ok := ctx.dnsClient.(dns.IPv6Lookup); ok {
+				lookupFunc = lookupIPv6.LookupIPv6
+			} else {
+				newError("ctx.dnsClient doesn't implement IPv6Lookup. Use LookupIP instead.").AtDebug().WriteToLog()
+			}
+		}
+
+		ips, err := lookupFunc(domain)
 		if err == nil {
 			ctx.resolvedIPs = ips
 			return ips