Feature: add custom DNS support (#56)

dns/util.go

@@ -0,0 +1,85 @@
+package dns
+
+import (
+	"encoding/json"
+	"errors"
+	"time"
+
+	"github.com/Dreamacro/clash/common/cache"
+	"github.com/Dreamacro/clash/log"
+	yaml "gopkg.in/yaml.v2"
+
+	D "github.com/miekg/dns"
+)
+
+var (
+	// EnhancedModeMapping is a mapping for EnhancedMode enum
+	EnhancedModeMapping = map[string]EnhancedMode{
+		FAKEIP.String():  FAKEIP,
+		MAPPING.String(): MAPPING,
+	}
+)
+
+const (
+	FAKEIP EnhancedMode = iota
+	MAPPING
+)
+
+type EnhancedMode int
+
+// UnmarshalYAML unserialize EnhancedMode with yaml
+func (e *EnhancedMode) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var tp string
+	if err := unmarshal(&tp); err != nil {
+		return err
+	}
+	mode, exist := EnhancedModeMapping[tp]
+	if !exist {
+		return errors.New("invalid mode")
+	}
+	*e = mode
+	return nil
+}
+
+// MarshalYAML serialize EnhancedMode with yaml
+func (e EnhancedMode) MarshalYAML() ([]byte, error) {
+	return yaml.Marshal(e.String())
+}
+
+// UnmarshalJSON unserialize EnhancedMode with json
+func (e *EnhancedMode) UnmarshalJSON(data []byte) error {
+	var tp string
+	json.Unmarshal(data, &tp)
+	mode, exist := EnhancedModeMapping[tp]
+	if !exist {
+		return errors.New("invalid mode")
+	}
+	*e = mode
+	return nil
+}
+
+// MarshalJSON serialize EnhancedMode with json
+func (e EnhancedMode) MarshalJSON() ([]byte, error) {
+	return json.Marshal(e.String())
+}
+
+func (e EnhancedMode) String() string {
+	switch e {
+	case FAKEIP:
+		return "fakeip"
+	case MAPPING:
+		return "redir-host"
+	default:
+		return "unknown"
+	}
+}
+
+func putMsgToCache(c *cache.Cache, key string, msg *D.Msg) {
+	if len(msg.Answer) == 0 {
+		log.Debugln("[DNS] answer length is zero: %#v", msg)
+		return
+	}
+
+	ttl := time.Duration(msg.Answer[0].Header().Ttl) * time.Second
+	c.Put(key, msg, ttl)
+}