Add Fake DNS support (#309)

Co-authored-by: Xiaokang Wang <xiaokangwang@outlook.com>
Co-authored-by: loyalsoldier <10487845+Loyalsoldier@users.noreply.github.com>
Co-authored-by: kslr <kslrwang@gmail.com>

infra/conf/fakedns.go

@@ -0,0 +1,65 @@
+package conf
+
+import (
+	"github.com/golang/protobuf/proto"
+	"github.com/xtls/xray-core/app/dns/fakedns"
+)
+
+type FakeDNSConfig struct {
+	IPPool  string `json:"ipPool"`
+	LruSize int64  `json:"poolSize"`
+}
+
+func (f FakeDNSConfig) Build() (proto.Message, error) {
+	return &fakedns.FakeDnsPool{
+		IpPool:  f.IPPool,
+		LruSize: f.LruSize,
+	}, nil
+}
+
+type FakeDNSPostProcessingStage struct{}
+
+func (FakeDNSPostProcessingStage) Process(conf *Config) error {
+	var fakeDNSInUse bool
+
+	if conf.DNSConfig != nil {
+		for _, v := range conf.DNSConfig.Servers {
+			if v.Address.Family().IsDomain() {
+				if v.Address.Domain() == "fakedns" {
+					fakeDNSInUse = true
+				}
+			}
+		}
+	}
+
+	if fakeDNSInUse {
+		if conf.FakeDNS == nil {
+			// Add a Fake DNS Config if there is none
+			conf.FakeDNS = &FakeDNSConfig{
+				IPPool:  "240.0.0.0/8",
+				LruSize: 65535,
+			}
+		}
+		found := false
+		// Check if there is a Outbound with necessary sniffer on
+		var inbounds []InboundDetourConfig
+
+		if len(conf.InboundConfigs) > 0 {
+			inbounds = append(inbounds, conf.InboundConfigs...)
+		}
+		for _, v := range inbounds {
+			if v.SniffingConfig != nil && v.SniffingConfig.Enabled && v.SniffingConfig.DestOverride != nil {
+				for _, dov := range *v.SniffingConfig.DestOverride {
+					if dov == "fakedns" {
+						found = true
+					}
+				}
+			}
+		}
+		if !found {
+			newError("Defined Fake DNS but haven't enabled fake dns sniffing at any inbound.").AtWarning().WriteToLog()
+		}
+	}
+
+	return nil
+}

infra/conf/init.go

@@ -0,0 +1,5 @@
+package conf
+
+func init() {
+	RegisterConfigureFilePostProcessingStage("FakeDNS", &FakeDNSPostProcessingStage{})
+}

infra/conf/lint.go

@@ -0,0 +1,23 @@
+package conf
+
+type ConfigureFilePostProcessingStage interface {
+	Process(conf *Config) error
+}
+
+var configureFilePostProcessingStages map[string]ConfigureFilePostProcessingStage
+
+func RegisterConfigureFilePostProcessingStage(name string, stage ConfigureFilePostProcessingStage) {
+	if configureFilePostProcessingStages == nil {
+		configureFilePostProcessingStages = make(map[string]ConfigureFilePostProcessingStage)
+	}
+	configureFilePostProcessingStages[name] = stage
+}
+
+func PostProcessConfigureFile(conf *Config) error {
+	for k, v := range configureFilePostProcessingStages {
+		if err := v.Process(conf); err != nil {
+			return newError("Rejected by Postprocessing Stage ", k).AtError().Base(err)
+		}
+	}
+	return nil
+}

infra/conf/xray.go

@@ -62,6 +62,7 @@ type SniffingConfig struct {
 	Enabled         bool        `json:"enabled"`
 	DestOverride    *StringList `json:"destOverride"`
 	DomainsExcluded *StringList `json:"domainsExcluded"`
+	MetadataOnly    bool        `json:"metadataOnly"`
 }
 
 // Build implements Buildable.
@@ -74,6 +75,8 @@ func (c *SniffingConfig) Build() (*proxyman.SniffingConfig, error) {
 				p = append(p, "http")
 			case "tls", "https", "ssl":
 				p = append(p, "tls")
+			case "fakedns":
+				p = append(p, "fakedns")
 			default:
 				return nil, newError("unknown protocol: ", protocol)
 			}
@@ -91,6 +94,7 @@ func (c *SniffingConfig) Build() (*proxyman.SniffingConfig, error) {
 		Enabled:             c.Enabled,
 		DestinationOverride: p,
 		DomainsExcluded:     d,
+		MetadataOnly:        c.MetadataOnly,
 	}, nil
 }
 
@@ -395,6 +399,7 @@ type Config struct {
 	API             *APIConfig             `json:"api"`
 	Stats           *StatsConfig           `json:"stats"`
 	Reverse         *ReverseConfig         `json:"reverse"`
+	FakeDNS         *FakeDNSConfig         `json:"fakeDns"`
 }
 
 func (c *Config) findInboundTag(tag string) int {
@@ -448,6 +453,10 @@ func (c *Config) Override(o *Config, fn string) {
 		c.Reverse = o.Reverse
 	}
 
+	if o.FakeDNS != nil {
+		c.FakeDNS = o.FakeDNS
+	}
+
 	// deprecated attrs... keep them for now
 	if o.InboundConfig != nil {
 		c.InboundConfig = o.InboundConfig
@@ -519,6 +528,10 @@ func applyTransportConfig(s *StreamConfig, t *TransportConfig) {
 
 // Build implements Buildable.
 func (c *Config) Build() (*core.Config, error) {
+	if err := PostProcessConfigureFile(c); err != nil {
+		return nil, err
+	}
+
 	config := &core.Config{
 		App: []*serial.TypedMessage{
 			serial.ToTypedMessage(&dispatcher.Config{}),
@@ -585,6 +598,14 @@ func (c *Config) Build() (*core.Config, error) {
 		config.App = append(config.App, serial.ToTypedMessage(r))
 	}
 
+	if c.FakeDNS != nil {
+		r, err := c.FakeDNS.Build()
+		if err != nil {
+			return nil, err
+		}
+		config.App = append(config.App, serial.ToTypedMessage(r))
+	}
+
 	var inbounds []InboundDetourConfig
 
 	if c.InboundConfig != nil {