ESP8266mDNS: support AP and STA interfaces at once

Bind the UDP connection to IP_ADDR_ANY rather than a specific interface
IP, so that it can receive queries from all interfaces at once.

When processing a query, detect which interface it was received on, and
pass this information to the reply code. Set the IP multicast interface
before each transmission, so that we can route each packet to a
different interface if required. These changes enable the code to
respond correctly on both AP and STA interfaces at once. The original
code only worked correctly for the STA interface if both were enabled.

When advertizing all services, do it on both AP and STA interfaces if
they're both enabled.

Provide an API for the application to notify the MDNS code if the AP
configuration changes (enabled, disabled, IP changed). Ideally, the WiFi
core would provide an event callback for this purpose, as it does for
STA changes, but it does not appear to, so the application must provide
this information.

libraries/ESP8266mDNS/ESP8266mDNS.cpp

@@ -170,6 +170,10 @@ bool MDNSResponder::begin(const char* hostname){
   return _listen();
 }
 
+void MDNSResponder::notifyAPChange() {
+  _restart();
+}
+
 void MDNSResponder::_restart() {
   if (_conn) {
     _conn->unref();
@@ -181,23 +185,13 @@ void MDNSResponder::_restart() {
 bool MDNSResponder::_listen() {
   // Open the MDNS socket if it isn't already open.
   if (!_conn) {
-    uint32_t ourIp = _getOurIp();
-    if(ourIp == 0){
-      #ifdef MDNS_DEBUG_RX
-      Serial.println("MDNS: no IP address to listen on");
-      #endif
-      return false;
-    }
     #ifdef MDNS_DEBUG_RX
-    Serial.print("MDNS listening on IP: ");
+    Serial.println("MDNS listening");
-    Serial.println(IPAddress(ourIp));
     #endif
-    ip_addr_t ifaddr;
-    ifaddr.addr = ourIp;
     ip_addr_t multicast_addr;
     multicast_addr.addr = (uint32_t) MDNS_MULTICAST_ADDR;
 
-    if (igmp_joingroup(&ifaddr, &multicast_addr)!= ERR_OK) {
+    if (igmp_joingroup(IP_ADDR_ANY, &multicast_addr)!= ERR_OK) {
       return false;
     }
 
@@ -207,7 +201,6 @@ bool MDNSResponder::_listen() {
     if (!_conn->listen(*IP_ADDR_ANY, MDNS_PORT)) {
       return false;
     }
-    _conn->setMulticastInterface(ifaddr);
     _conn->setMulticastTTL(MDNS_MULTICAST_TTL);
     _conn->onRx(std::bind(&MDNSResponder::update, this));
     _conn->connect(multicast_addr, MDNS_PORT);
@@ -444,24 +437,6 @@ uint16_t MDNSResponder::_getServicePort(char *name, char *proto){
   return 0;
 }
 
-uint32_t MDNSResponder::_getOurIp(){
-  int mode = wifi_get_opmode();
-  if(mode & STATION_MODE){
-    struct ip_info staIpInfo;
-    wifi_get_ip_info(STATION_IF, &staIpInfo);
-    return staIpInfo.ip.addr;
-  } else if (mode & SOFTAP_MODE) {
-    struct ip_info staIpInfo;
-    wifi_get_ip_info(SOFTAP_IF, &staIpInfo);
-    return staIpInfo.ip.addr;
-  } else {
-#ifdef MDNS_DEBUG_ERR
-    Serial.printf("ERR_NO_LOCAL_IP\n");
-#endif
-    return 0;
-  }
-}
-
 void MDNSResponder::_parsePacket(){
   int i;
   char tmp;
@@ -868,7 +843,20 @@ void MDNSResponder::_parsePacket(){
     else if(questions[i] == MDNS_TYPE_PTR) responseMask |= 0xF;
   }
 
-  return _reply(responseMask, serviceName, protoName, servicePort);
+  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);
+  uint32_t ip = ip_info.ip.addr;
+
+  return _reply(responseMask, serviceName, protoName, servicePort, ip);
 }
 
 void MDNSResponder::enableArduino(uint16_t port, bool auth){
@@ -882,17 +870,28 @@ void MDNSResponder::enableArduino(uint16_t port, bool auth){
 
 size_t MDNSResponder::advertiseServices(){
   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){
-      _reply(0x0F, servicePtr->_name, servicePtr->_proto, servicePtr->_port);
+      wifi_get_ip_info(SOFTAP_IF, &ip_info);
+      ip = ip_info.ip.addr;
+      if (ip)
+        _reply(0x0F, servicePtr->_name, servicePtr->_proto, servicePtr->_port, ip);
+
+      wifi_get_ip_info(SOFTAP_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){
+void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint16_t port, uint32_t ip) {
   int i;
   if(replyMask == 0) return;
 
@@ -1062,7 +1061,6 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
     _conn->append(reinterpret_cast<const char*>(localName), localNameLen);     // "local"
     _conn->append(reinterpret_cast<const char*>(&terminator), 1);              // terminator
 
-    uint32_t ip = _getOurIp();
     uint8_t aaaAttrs[10] = {
       0x00, 0x01,             //TYPE A
       0x80, 0x01,             //Class IN, with cache flush
@@ -1081,7 +1079,10 @@ void MDNSResponder::_reply(uint8_t replyMask, char * service, char *proto, uint1
     _conn->append(reinterpret_cast<const char*>(aaaRData), 4);
   }
 
- _conn->send();
+  ip_addr_t ifaddr;
+  ifaddr.addr = ip;
+  _conn->setMulticastInterface(ifaddr);
+  _conn->send();
 }
 
 #if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_MDNS)

libraries/ESP8266mDNS/ESP8266mDNS.h

@@ -66,6 +66,8 @@ public:
   bool begin(const char* hostName, IPAddress ip, uint32_t ttl=120){
     return begin(hostName);
   }
+  /* Application should call this whenever AP is configured/disabled */
+  void notifyAPChange();
   void update();
 
   void addService(char *service, char *proto, uint16_t port);
@@ -118,12 +120,11 @@ private:
   WiFiEventHandler _gotIPHandler;
   
 
-  uint32_t _getOurIp();
   uint16_t _getServicePort(char *service, char *proto);
   MDNSTxt * _getServiceTxt(char *name, char *proto);
   uint16_t _getServiceTxtLen(char *name, char *proto);
   void _parsePacket();
-  void _reply(uint8_t replyMask, char * service, char *proto, uint16_t port);
+  void _reply(uint8_t replyMask, char * service, char *proto, uint16_t port, uint32_t ip);
   size_t advertiseServices(); // advertise all hosted services
   MDNSAnswer* _getAnswerFromIdx(int idx);
   int _getNumAnswers();