Sorry, I should have read more about goto, I understand now, And it should work now.

src/netsukuku.c

                             if(tmp->ifa_addr && tmp->ifa_addr->sa_family == AF_PACKET)
                                     ifs = tmp->ifa_name;
                             
-                            printf("One");
-                            
-                            goto Check_Active;
-                            
-                            printf("Two");
-                            
                                 if(strncmp(ifs, "lo", 2) == 0 || strncmp(ifs, "tunl0", 5) == 0 || strncmp(ifs, "tunl1", 5) == 0 || strcmp(ifs, optarg) == 0)
                                     goto Check_Active;
                                     
                             Check_Active:
+                            
                             a_ifs = ifs;
                             if(a_ifs->ifr_name != IFF_UP) {
                                 tmp = tmp->ifa_next;
                                 if(tmp->ifa_addr && tmp->ifa_addr->sa_family == AF_PACKET)
                                             ifs = tmp->ifa_name;
                             }
+                            
                             tmp = tmp->ifa_next;
 			    if(strcmp(old_tmp, ifs) == 0)
 					break;