[dns-sd] Fix operational advertising

After project-chip#5337 has been merged, operational advertising no
longer works since at the time the advertising is started
nodeID stored in the admin table is not yet initialized.

Start operational advertising when the device is assigned
an IP address. In the future, e2e commissioning flow will
probably take care of that in a different way.

examples/all-clusters-app/esp32/main/main.cpp

@@ -311,7 +311,7 @@ class SetupListModel : public ListScreen::Model
         }
         else if (i == 2)
         {
-            app::Mdns::AdvertiseCommisioning();
+            app::Mdns::AdvertiseCommisionable();
             OpenDefaultPairingWindow(ResetAdmins::kNo, PairingWindowAdvertisement::kMdns);
         }
     }

examples/all-clusters-app/linux/main.cpp

@@ -65,9 +65,6 @@ int main(int argc, char * argv[])
     // Init ZCL Data Model and CHIP App Server
     InitServer();
 
-    // Init Mdns Server
-    app::Mdns::StartServer();
-
     chip::DeviceLayer::PlatformMgr().RunEventLoop();
 
 exit:

src/app/server/Mdns.cpp

@@ -111,9 +111,8 @@ CHIP_ERROR AdvertiseOperational()
 }
 
 /// Set MDNS commisioning advertisement
-CHIP_ERROR AdvertiseCommisioning()
+CHIP_ERROR AdvertiseCommisionable()
 {
-
     auto advertiseParameters = chip::Mdns::CommissionAdvertisingParameters().SetPort(CHIP_PORT).EnableIpV4(true);
 
     uint8_t mac[8];
@@ -171,7 +170,7 @@ void StartServer()
 // so configuraton should be added to enable commissioning advertising based on supported
 // Rendezvous methods.
 #if !CHIP_DEVICE_CONFIG_ENABLE_THREAD
-        err = app::Mdns::AdvertiseCommisioning();
+        err = app::Mdns::AdvertiseCommisionable();
 #endif
     }
 

src/app/server/Mdns.h

@@ -23,11 +23,11 @@ namespace chip {
 namespace app {
 namespace Mdns {
 
-/// Set MDNS operational advertisement
+/// Start operational advertising
 CHIP_ERROR AdvertiseOperational();
 
-/// Set MDNS commisioning advertisement
-CHIP_ERROR AdvertiseCommisioning();
+/// Start commisionable node advertising
+CHIP_ERROR AdvertiseCommisionable();
 
 /// (Re-)starts the minmdns server
 void StartServer();

src/app/server/Server.cpp

@@ -276,17 +276,6 @@ class ServerRendezvousAdvertisementDelegate : public RendezvousAdvertisementDele
         return CHIP_NO_ERROR;
     }
 
-#if CHIP_DEVICE_CONFIG_ENABLE_MDNS
-    void RendezvousComplete() const override
-    {
-        // Once rendezvous completed, assume we are operational
-        if (app::Mdns::AdvertiseOperational() != CHIP_NO_ERROR)
-        {
-            ChipLogError(Discovery, "Failed to start advertising operational state at rendezvous completion time.");
-        }
-    }
-#endif
-
     void SetDelegate(AppDelegate * delegate) { mDelegate = delegate; }
     void SetBLE(bool ble) { isBLE = ble; }
     void SetAdminId(AdminId id) { mAdmin = id; }
@@ -465,6 +454,33 @@ CHIP_ERROR OpenDefaultPairingWindow(ResetAdmins resetAdmins, chip::PairingWindow
     return gRendezvousServer.WaitForPairing(std::move(params), &gExchangeMgr, &gTransports, &gSessions, adminInfo);
 }
 
+#if CHIP_DEVICE_CONFIG_ENABLE_MDNS && !CHIP_DEVICE_LAYER_TARGET_ESP32
+static void ChipEventHandler(const DeviceLayer::ChipDeviceEvent * event, intptr_t)
+{
+    const auto advertise = [] {
+        CHIP_ERROR err = app::Mdns::AdvertiseOperational();
+        if (err != CHIP_NO_ERROR)
+            ChipLogError(AppServer, "Failed to start operational advertising: %s", chip::ErrorStr(err));
+    };
+
+    switch (event->Type)
+    {
+    case DeviceLayer::DeviceEventType::kInternetConnectivityChange:
+        VerifyOrReturn(event->InternetConnectivityChange.IPv4 == DeviceLayer::kConnectivity_Established);
+        advertise();
+        break;
+#if CHIP_DEVICE_CONFIG_ENABLE_THREAD
+    case DeviceLayer::DeviceEventType::kThreadStateChange:
+        VerifyOrReturn(event->ThreadStateChange.AddressChanged);
+        advertise();
+        break;
+#endif
+    default:
+        break;
+    }
+}
+#endif
+
 // The function will initialize datamodel handler and then start the server
 // The server assumes the platform's networking has been setup already
 void InitServer(AppDelegate * delegate)
@@ -537,11 +553,10 @@ void InitServer(AppDelegate * delegate)
 #endif
     }
 
-// Starting mDNS server only for Thread devices due to problem reported in issue #5076.
-#if CHIP_DEVICE_CONFIG_ENABLE_THREAD
-#if CHIP_DEVICE_CONFIG_ENABLE_MDNS
+// ESP32 examples have a custom logic for enabling DNS-SD
+#if CHIP_DEVICE_CONFIG_ENABLE_MDNS && !CHIP_DEVICE_LAYER_TARGET_ESP32
     app::Mdns::StartServer();
-#endif
+    PlatformMgr().AddEventHandler(ChipEventHandler, {});
 #endif
 
     gCallbacks.SetSessionMgr(&gSessions);