fix darwin calculate correct tunIndex

listener/sing_tun/server.go

@@ -24,6 +24,7 @@ import (
 	E "github.com/sagernet/sing/common/exceptions"
 	F "github.com/sagernet/sing/common/format"
 	"github.com/sagernet/sing/common/ranges"
+	"golang.org/x/exp/slices"
 )
 
 var InterfaceName = "Mihomo"
@@ -60,19 +61,21 @@ func CalculateInterfaceName(name string) (tunName string) {
 		return
 	}
 	tunIndex := 0
-	indexSet := make(map[int]struct{})
+	indexArr := make([]int, 0, len(interfaces))
 	for _, netInterface := range interfaces {
 		if strings.HasPrefix(netInterface.Name, tunName) {
 			index, parseErr := strconv.ParseInt(netInterface.Name[len(tunName):], 10, 16)
 			if parseErr == nil {
-				indexSet[int(index)] = struct{}{}
+				indexArr = append(indexArr, int(index))
 			}
 		}
 	}
-	for index := range indexSet {
+	slices.Sort(indexArr)
+	indexArr = slices.Compact(indexArr)
+	for _, index := range indexArr {
 		if index == tunIndex {
 			tunIndex += 1
-		} else { // indexSet already sorted and distinct, so this tunIndex nobody used
+		} else { // indexArr already sorted and distinct, so this tunIndex nobody used
 			break
 		}
 	}