Fix DNS servers with same tag wrongly merged

infra/conf/merge/merge_test.go

@@ -194,6 +194,108 @@ func TestMergeTagDeep(t *testing.T) {
 	assertResult(t, m, expected)
 }
 
+func TestNoMergeDnsServers(t *testing.T) {
+	json1 := `
+	{
+		"dns": {
+			"queryStrategy": "UseIPv4",
+			"fallbackStrategy": "disabled-if-any-match",
+			"domainMatcher": "mph",
+			"servers": [
+				{
+					"address": "aaa.bbb.ccc.ddd",
+					"port": 53,
+					"domains": [
+						"geosite:cn"
+					],
+					"tag": "dns-domestic"
+				},
+				{
+					"address": "114.114.114.114",
+					"port": 53,
+					"domains": [
+						"geosite:cn"
+					],
+					"tag": "dns-domestic"
+				},
+				{
+					"address": "https://1.1.1.1/dns-query",
+					"tag": "dns-international"
+				}
+			]
+		},
+		"routing": {
+			"domainStrategy": "IPIfNonMatch",
+			"domainMatcher": "mph",
+			"rules": [
+				{
+					"type": "field",
+					"inboundTag": "dns-domestic",
+					"outboundTag": "direct"
+				},
+				{
+					"type": "field",
+					"inboundTag": "dns-international",
+					"outboundTag": "proxy"
+				}
+			]
+		}
+	}
+`
+	expected := `
+	{
+		"dns": {
+			"queryStrategy": "UseIPv4",
+			"fallbackStrategy": "disabled-if-any-match",
+			"domainMatcher": "mph",
+			"servers": [
+				{
+					"address": "aaa.bbb.ccc.ddd",
+					"port": 53,
+					"domains": [
+						"geosite:cn"
+					],
+					"tag": "dns-domestic"
+				},
+				{
+					"address": "114.114.114.114",
+					"port": 53,
+					"domains": [
+						"geosite:cn"
+					],
+					"tag": "dns-domestic"
+				},
+				{
+					"address": "https://1.1.1.1/dns-query",
+					"tag": "dns-international"
+				}
+			]
+		},
+		"routing": {
+			"domainStrategy": "IPIfNonMatch",
+			"domainMatcher": "mph",
+			"rules": [
+				{
+					"type": "field",
+					"inboundTag": "dns-domestic",
+					"outboundTag": "direct"
+				},
+				{
+					"type": "field",
+					"inboundTag": "dns-international",
+					"outboundTag": "proxy"
+				}
+			]
+		}
+	}
+`
+	m, err := merge.JSONs([][]byte{[]byte(json1)})
+	if err != nil {
+		t.Error(err)
+	}
+	assertResult(t, m, expected)
+}
+
 func assertResult(t *testing.T, value []byte, expected string) {
 	v := make(map[string]interface{})
 	err := serial.DecodeJSON(bytes.NewReader(value), &v)

infra/conf/merge/rules.go

@@ -4,6 +4,8 @@
 
 package merge
 
+import "fmt"
+
 const (
 	priorityKey string = "_priority"
 	tagKey      string = "_tag"
@@ -11,7 +13,7 @@ const (
 
 // ApplyRules applies merge rules according to _tag, _priority fields, and remove them
 func ApplyRules(m map[string]interface{}) error {
-	err := sortMergeSlices(m)
+	err := sortMergeSlices(m, "")
 	if err != nil {
 		return err
 	}
@@ -20,22 +22,22 @@ func ApplyRules(m map[string]interface{}) error {
 }
 
 // sortMergeSlices enumerates all slices in a map, to sort by priority and merge by tag
-func sortMergeSlices(target map[string]interface{}) error {
+func sortMergeSlices(target map[string]interface{}, path string) error {
 	for key, value := range target {
 		if slice, ok := value.([]interface{}); ok {
 			sortByPriority(slice)
-			s, err := mergeSameTag(slice)
+			s, err := mergeSameTag(slice, fmt.Sprintf("%s.%s", path, key))
 			if err != nil {
 				return err
 			}
 			target[key] = s
-			for _, item := range s {
+			for i, item := range s {
 				if m, ok := item.(map[string]interface{}); ok {
-					sortMergeSlices(m)
+					sortMergeSlices(m, fmt.Sprintf("%s.%s.%d", path, key, i))
 				}
 			}
 		} else if field, ok := value.(map[string]interface{}); ok {
-			sortMergeSlices(field)
+			sortMergeSlices(field, fmt.Sprintf("%s.%s", path, key))
 		}
 	}
 	return nil

infra/conf/merge/tag.go

@@ -4,12 +4,18 @@
 
 package merge
 
-func getTag(v map[string]interface{}) string {
+import (
+	"strings"
+)
+
+func getTag(v map[string]interface{}, tagKeyOnly bool) string {
+	if !tagKeyOnly {
 		if field, ok := v["tag"]; ok {
 			if t, ok := field.(string); ok {
 				return t
 			}
 		}
+	}
 	if field, ok := v[tagKey]; ok {
 		if t, ok := field.(string); ok {
 			return t
@@ -18,16 +24,21 @@ func getTag(v map[string]interface{}) string {
 	return ""
 }
 
-func mergeSameTag(s []interface{}) ([]interface{}, error) {
+func mergeSameTag(s []interface{}, path string) ([]interface{}, error) {
 	// from: [a,"",b,"",a,"",b,""]
 	// to: [a,"",b,"",merged,"",merged,""]
 	merged := &struct{}{}
+	tagKeyOnly := false
+	// See https://github.com/v2fly/v2ray-core/issues/2981
+	if strings.HasPrefix(path, ".dns.servers") {
+		tagKeyOnly = true
+	}
 	for i, item1 := range s {
 		map1, ok := item1.(map[string]interface{})
 		if !ok {
 			continue
 		}
-		tag1 := getTag(map1)
+		tag1 := getTag(map1, tagKeyOnly)
 		if tag1 == "" {
 			continue
 		}
@@ -36,7 +47,7 @@ func mergeSameTag(s []interface{}) ([]interface{}, error) {
 			if !ok {
 				continue
 			}
-			tag2 := getTag(map2)
+			tag2 := getTag(map2, tagKeyOnly)
 			if tag1 == tag2 {
 				s[j] = merged
 				err := mergeMaps(map1, map2)