[Issue #3145] ESP8266mDNS: Improve compliance with DNS-SD RFC6763

- When the "_services._dns_sd._udp.local" meta-query is received, an
enumeration of services types is now returned (e.g. "_http._tcp.local")
instead of an enumeration of instances (e.g.
"MyService._http._tcp.local").  This is consistent with Section 9 of the
RFC.

- When a response is sent, the response records are now properly
partitioned as either answers or additional records.  Only response
records that were explicitly requested as a result of the questions
should be treated as answers.  This is consistent with Section 12 of the
RFC.

- The "MDNSResponder::advertiseServices()" method has been removed as it
was declared as "private" and is no longer being called.  This method
was sending a response on multiple interfaces when available, but this
wasn't really necessary since the interface from which the request was
received that caused it to be invoked is known.

libraries/ESP8266mDNS/ESP8266mDNS.cpp

@@ -450,6 +450,21 @@ uint16_t MDNSResponder::_getServicePort(char *name, char *proto){
   return 0;
 }
 
+IPAddress MDNSResponder::_getRequestMulticastInterface(){
+  struct ip_info ip_info;
+  bool match_ap = false;
+  if (wifi_get_opmode() & SOFTAP_MODE) {
+    struct ip_info remote_ip_info;
+    remote_ip_info.ip.addr = _conn->getRemoteAddress();
+    wifi_get_ip_info(SOFTAP_IF, &ip_info);
+    if (ip_info.ip.addr && ip_addr_netcmp(&remote_ip_info.ip, &ip_info.ip, &ip_info.netmask))
+      match_ap = true;
+  }
+  if (!match_ap)
+    wifi_get_ip_info(STATION_IF, &ip_info);
+  return IPAddress(ip_info.ip.addr);
+}
+
 void MDNSResponder::_parsePacket(){
   int i;
   char tmp;
@@ -759,7 +774,8 @@ void MDNSResponder::_parsePacket(){
       protoParsed = true;
     } else if(strcmp("services", serviceName) == 0 && strcmp("_dns-sd", protoName) == 0){
       _conn->flush();
-      advertiseServices();
+      IPAddress interface = _getRequestMulticastInterface();
+      _replyToTypeEnumRequest(interface);
       return;
     } else {
 #ifdef MDNS_DEBUG_ERR
@@ -854,28 +870,26 @@ void MDNSResponder::_parsePacket(){
     Serial.printf("\n");
 #endif
   }
+  uint8_t questionMask = 0;
   uint8_t responseMask = 0;
   for(i=0;i<question;i++){
-    if(questions[i] == MDNS_TYPE_A) responseMask |= 0x1;
+    if(questions[i] == MDNS_TYPE_A) {
-    else if(questions[i] == MDNS_TYPE_SRV) responseMask |= 0x3;
+      questionMask |= 0x1;
-    else if(questions[i] == MDNS_TYPE_TXT) responseMask |= 0x4;
+      responseMask |= 0x1;
-    else if(questions[i] == MDNS_TYPE_PTR) responseMask |= 0xF;
+    } else if(questions[i] == MDNS_TYPE_SRV) {
+      questionMask |= 0x2;
+      responseMask |= 0x3;
+    } else if(questions[i] == MDNS_TYPE_TXT) {
+      questionMask |= 0x4;
+      responseMask |= 0x4;
+    } else if(questions[i] == MDNS_TYPE_PTR) {
+      questionMask |= 0x8;
+      responseMask |= 0xF;
+    }
   }
 
-  struct ip_info ip_info;
+  IPAddress interface = _getRequestMulticastInterface();
-  bool match_ap = false;
+  return _replyToInstanceRequest(questionMask, responseMask, serviceName, protoName, servicePort, interface);
-  if (wifi_get_opmode() & SOFTAP_MODE) {
-    struct ip_info remote_ip_info;
-    remote_ip_info.ip.addr = _conn->getRemoteAddress();
-    wifi_get_ip_info(SOFTAP_IF, &ip_info);
-    if (ip_info.ip.addr && ip_addr_netcmp(&remote_ip_info.ip, &ip_info.ip, &ip_info.netmask))
-      match_ap = true;
-  }
-  if (!match_ap)
-    wifi_get_ip_info(STATION_IF, &ip_info);
-  uint32_t ip = ip_info.ip.addr;
-
-  return _reply(responseMask, serviceName, protoName, servicePort, ip);
 }
 
 void MDNSResponder::enableArduino(uint16_t port, bool auth){
@@ -887,35 +901,103 @@ void MDNSResponder::enableArduino(uint16_t port, bool auth){
   addServiceTxt("arduino", "tcp", "auth_upload", (auth) ? "yes":"no");
 }
 
-size_t MDNSResponder::advertiseServices(){
+void MDNSResponder::_replyToTypeEnumRequest(IPAddress multicastInterface) {
   MDNSService* servicePtr;
-  struct ip_info ip_info;
-  uint32_t ip;
-  size_t i = 0;
   for (servicePtr = _services; servicePtr; servicePtr = servicePtr->_next) {
     if(servicePtr->_port > 0){
-      wifi_get_ip_info(SOFTAP_IF, &ip_info);
+      char *service = servicePtr->_name;
-      ip = ip_info.ip.addr;
+      char *proto = servicePtr->_proto;
-      if (ip)
+      uint16_t port = servicePtr->_port;
-        _reply(0x0F, servicePtr->_name, servicePtr->_proto, servicePtr->_port, ip);
-
-      wifi_get_ip_info(STATION_IF, &ip_info);
-      ip = ip_info.ip.addr;
-      if (ip)
-        _reply(0x0F, servicePtr->_name, servicePtr->_proto, servicePtr->_port, ip);
-
-      i++;
-    }
-  }
-  return i;
-}
-
-void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint16_t port, uint32_t ip) {
-  int i;
-  if(replyMask == 0) return;
 
 #ifdef MDNS_DEBUG_TX
-    Serial.printf("TX: mask:%01X, service:%s, proto:%s, port:%u\n", replyMask, service, proto, port);
+      Serial.printf("TX: service:%s, proto:%s\n", service, proto);
+#endif
+
+      char sdHostName[] = "_services";
+      size_t sdHostNameLen = 9;
+      char sdServiceName[] = "_dns-sd";
+      size_t sdServiceNameLen = 7;
+      char sdProtoName[] = "_udp";
+      size_t sdProtoNameLen = 4;
+
+      char underscore[]  = "_";
+
+      // build service name with _
+      char serviceName[os_strlen(service) + 2];
+      os_strcpy(serviceName, underscore);
+      os_strcat(serviceName, service);
+      size_t serviceNameLen = os_strlen(serviceName);
+
+      //build proto name with _
+      char protoName[5];
+      os_strcpy(protoName, underscore);
+      os_strcat(protoName, proto);
+      size_t protoNameLen = 4;
+
+      //local string
+      char localName[] = "local";
+      size_t localNameLen = 5;
+
+      //terminator
+      char terminator[] = "\0";
+
+      //Write the header
+      _conn->flush();
+      uint8_t head[12] = {
+        0x00, 0x00, //ID = 0
+        0x84, 0x00, //Flags = response + authoritative answer
+        0x00, 0x00, //Question count
+        0x00, 0x01, //Answer count
+        0x00, 0x00, //Name server records
+        0x00, 0x00, //Additional records
+      };
+      _conn->append(reinterpret_cast<const char*>(head), 12);
+
+      // Send the Name field (ie. "_services._dns-sd._udp.local")
+      _conn->append(reinterpret_cast<const char*>(&sdHostNameLen), 1);         // length of "_services"
+      _conn->append(reinterpret_cast<const char*>(sdHostName), sdHostNameLen); // "_services"
+      _conn->append(reinterpret_cast<const char*>(&sdServiceNameLen), 1);      // length of "_dns-sd"
+      _conn->append(reinterpret_cast<const char*>(sdServiceName), sdServiceNameLen);// "_dns-sd"
+      _conn->append(reinterpret_cast<const char*>(&sdProtoNameLen), 1);        // length of "_udp"
+      _conn->append(reinterpret_cast<const char*>(sdProtoName), sdProtoNameLen); // "_udp"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
+      _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
+      _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
+
+      //Send the type, class, ttl and rdata length
+      uint8_t ptrDataLen = serviceNameLen + protoNameLen + localNameLen + 4;   // 4 is three label sizes and the terminator
+      uint8_t ptrAttrs[10] = {
+        0x00, 0x0c,             //PTR record query
+        0x00, 0x01,             //Class IN
+        0x00, 0x00, 0x11, 0x94, //TTL 4500
+        0x00, ptrDataLen,       //RData length
+      };
+      _conn->append(reinterpret_cast<const char*>(ptrAttrs), 10);
+
+      //Send the RData (ie. "_http._tcp.local")
+      _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);        // length of "_http"
+      _conn->append(reinterpret_cast<const char*>(serviceName), serviceNameLen); // "_http"
+      _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);          // length of "_tcp"
+      _conn->append(reinterpret_cast<const char*>(protoName), protoNameLen);   // "_tcp"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
+      _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
+      _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
+
+      ip_addr_t ifaddr;
+      ifaddr.addr = multicastInterface;
+      _conn->setMulticastInterface(ifaddr);
+      _conn->send();
+    }
+  }
+}
+
+void MDNSResponder::_replyToInstanceRequest(uint8_t questionMask, uint8_t responseMask, char * service, char *proto, uint16_t port, IPAddress multicastInterface) {
+  int i;
+  if(questionMask == 0) return;
+  if(responseMask == 0) return;
+
+#ifdef MDNS_DEBUG_TX
+    Serial.printf("TX: qmask:%01X, rmask:%01X, service:%s, proto:%s, port:%u\n", questionMask, responseMask, service, proto, port);
 #endif
 
 
@@ -946,9 +1028,13 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
   //terminator
   char terminator[] = "\0";
 
+  uint8_t answerMask = responseMask & questionMask;
   uint8_t answerCount = 0;
+  uint8_t additionalMask = responseMask & ~questionMask;
+  uint8_t additionalCount = 0;
   for(i=0;i<4;i++){
-    if(replyMask & (1 << i)) answerCount++;
+    if(answerMask & (1 << i)) answerCount++;
+    if(additionalMask & (1 << i)) additionalCount++;
   }
 
 
@@ -960,18 +1046,20 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
     0x00, 0x00, //Question count
     0x00, answerCount, //Answer count
     0x00, 0x00, //Name server records
-    0x00, 0x00, //Additional records
+    0x00, additionalCount, //Additional records
   };
   _conn->append(reinterpret_cast<const char*>(head), 12);
 
+  for(int responseSection = 0; responseSection < 2; ++responseSection) {
+
     // PTR Response
-  if(replyMask & 0x8){
+    if((responseSection == 0 ? answerMask : additionalMask) & 0x8){
       // Send the Name field (ie. "_http._tcp.local")
-    _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);          // lenght of "_http"
+      _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);        // length of "_http"
       _conn->append(reinterpret_cast<const char*>(serviceName), serviceNameLen); // "_http"
-    _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);            // lenght of "_tcp"
+      _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);          // length of "_tcp"
       _conn->append(reinterpret_cast<const char*>(protoName), protoNameLen);   // "_tcp"
-    _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);            // lenght "local"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
       _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
       _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
 
@@ -980,33 +1068,33 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
       uint8_t ptrAttrs[10] = {
         0x00, 0x0c,             //PTR record query
         0x00, 0x01,             //Class IN
-      0x00, 0x00, 0x11, 0x94, //TTL 4500
+        0x00, 0x00, 0x00, 0x78, //TTL 120
         0x00, ptrDataLen,       //RData length
       };
       _conn->append(reinterpret_cast<const char*>(ptrAttrs), 10);
 
       //Send the RData (ie. "My IOT device._http._tcp.local")
-    _conn->append(reinterpret_cast<const char*>(&instanceNameLen), 1);         // lenght of "My IOT device"
+      _conn->append(reinterpret_cast<const char*>(&instanceNameLen), 1);       // length of "My IOT device"
       _conn->append(reinterpret_cast<const char*>(instanceName.c_str()), instanceNameLen);// "My IOT device"
-    _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);          // lenght of "_http"
+      _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);        // length of "_http"
       _conn->append(reinterpret_cast<const char*>(serviceName), serviceNameLen); // "_http"
-    _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);            // lenght of "_tcp"
+      _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);          // length of "_tcp"
       _conn->append(reinterpret_cast<const char*>(protoName), protoNameLen);   // "_tcp"
-    _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);            // lenght "local"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
       _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
       _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
     }
 
     //TXT Responce
-  if(replyMask & 0x4){
+    if((responseSection == 0 ? answerMask : additionalMask) & 0x4){
       //Send the name field (ie. "My IOT device._http._tcp.local")
-    _conn->append(reinterpret_cast<const char*>(&instanceNameLen), 1);         // lenght of "My IOT device"
+      _conn->append(reinterpret_cast<const char*>(&instanceNameLen), 1);       // length of "My IOT device"
       _conn->append(reinterpret_cast<const char*>(instanceName.c_str()), instanceNameLen);// "My IOT device"
-    _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);          // lenght of "_http"
+      _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);        // length of "_http"
       _conn->append(reinterpret_cast<const char*>(serviceName), serviceNameLen); // "_http"
-    _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);            // lenght of "_tcp"
+      _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);          // length of "_tcp"
       _conn->append(reinterpret_cast<const char*>(protoName), protoNameLen);   // "_tcp"
-    _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);            // lenght "local"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
       _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
       _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
 
@@ -1014,7 +1102,7 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
       uint8_t txtDataLen = _getServiceTxtLen(service,proto);
       uint8_t txtAttrs[10] = {
         0x00, 0x10,             //TXT record query
-      0x00, 0x01,             //Class IN
+        0x80, 0x01,             //Class IN, with cache flush
         0x00, 0x00, 0x11, 0x94, //TTL 4500
         0x00, txtDataLen,       //RData length
       };
@@ -1024,7 +1112,7 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
       MDNSTxt * txtPtr = _getServiceTxt(service,proto);
       while(txtPtr !=0){
         uint8_t txtLen = txtPtr->_txt.length();
-      _conn->append(reinterpret_cast<const char*>(&txtLen), 1);                  // lenght of txt
+        _conn->append(reinterpret_cast<const char*>(&txtLen), 1);                  // length of txt
         _conn->append(reinterpret_cast<const char*>(txtPtr->_txt.c_str()), txtLen);// the txt
         txtPtr = txtPtr->_next;
       }
@@ -1032,15 +1120,15 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
 
 
     //SRV Responce
-  if(replyMask & 0x2){
+    if((responseSection == 0 ? answerMask : additionalMask) & 0x2){
       //Send the name field (ie. "My IOT device._http._tcp.local")
-    _conn->append(reinterpret_cast<const char*>(&instanceNameLen), 1);         // lenght of "My IOT device"
+      _conn->append(reinterpret_cast<const char*>(&instanceNameLen), 1);       // length of "My IOT device"
       _conn->append(reinterpret_cast<const char*>(instanceName.c_str()), instanceNameLen);// "My IOT device"
-    _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);          // lenght of "_http"
+      _conn->append(reinterpret_cast<const char*>(&serviceNameLen), 1);        // length of "_http"
       _conn->append(reinterpret_cast<const char*>(serviceName), serviceNameLen); // "_http"
-    _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);            // lenght of "_tcp"
+      _conn->append(reinterpret_cast<const char*>(&protoNameLen), 1);          // length of "_tcp"
       _conn->append(reinterpret_cast<const char*>(protoName), protoNameLen);   // "_tcp"
-    _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);            // lenght "local"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
       _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
       _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
 
@@ -1063,20 +1151,20 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
       };
       _conn->append(reinterpret_cast<const char*>(srvRData), 6);
       //Send the RData (ie. "esp8266.local")
-    _conn->append(reinterpret_cast<const char*>(&hostNameLen), 1);             // lenght of "esp8266"
+      _conn->append(reinterpret_cast<const char*>(&hostNameLen), 1);           // length of "esp8266"
       _conn->append(reinterpret_cast<const char*>(hostName.c_str()), hostNameLen);// "esp8266"
-    _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);            // lenght "local"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
       _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
       _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
 
     }
 
     // A Response
-  if(replyMask & 0x1){
+    if((responseSection == 0 ? answerMask : additionalMask) & 0x1){
       //Send the RData (ie. "esp8266.local")
-    _conn->append(reinterpret_cast<const char*>(&hostNameLen), 1);             // lenght of "esp8266"
+      _conn->append(reinterpret_cast<const char*>(&hostNameLen), 1);           // length of "esp8266"
       _conn->append(reinterpret_cast<const char*>(hostName.c_str()), hostNameLen);// "esp8266"
-    _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);            // lenght "local"
+      _conn->append(reinterpret_cast<const char*>(&localNameLen), 1);          // length "local"
       _conn->append(reinterpret_cast<const char*>(localName), localNameLen);   // "local"
       _conn->append(reinterpret_cast<const char*>(&terminator), 1);            // terminator
 
@@ -1089,6 +1177,7 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
       _conn->append(reinterpret_cast<const char*>(aaaAttrs), 10);
 
       // Send RData
+      uint32_t ip = multicastInterface;
       uint8_t aaaRData[4] = {
         (uint8_t)(ip & 0xFF),         //IP first octet
         (uint8_t)((ip >> 8) & 0xFF),  //IP second octet
@@ -1097,9 +1186,10 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
       };
       _conn->append(reinterpret_cast<const char*>(aaaRData), 4);
     }
+  }
 
   ip_addr_t ifaddr;
-  ifaddr.addr = ip;
+  ifaddr.addr = multicastInterface;
   _conn->setMulticastInterface(ifaddr);
   _conn->send();
 }

libraries/ESP8266mDNS/ESP8266mDNS.h

@@ -125,9 +125,10 @@ private:
   uint16_t _getServicePort(char *service, char *proto);
   MDNSTxt * _getServiceTxt(char *name, char *proto);
   uint16_t _getServiceTxtLen(char *name, char *proto);
+  IPAddress _getRequestMulticastInterface();
   void _parsePacket();
-  void _reply(uint8_t replyMask, char * service, char *proto, uint16_t port, uint32_t ip);
+  void _replyToTypeEnumRequest(IPAddress multicastInterface);
-  size_t advertiseServices(); // advertise all hosted services
+  void _replyToInstanceRequest(uint8_t questionMask, uint8_t responseMask, char * service, char *proto, uint16_t port, IPAddress multicastInterface);
   MDNSAnswer* _getAnswerFromIdx(int idx);
   int _getNumAnswers();
   bool _listen();