esp32 lock-app mdns server start at connectivity change

[DamKast]

Problem

What is being fixed? Examples:

• Fixes chip-device-ctrl - resolve command hangs with lock-app  #7705 chip-device-ctrl - resolve command hangs with lock-app.

Change overview

esp32 lock-app mdns server start at connectivity change

Testing

How was this tested? (at least one bullet point required)

• using lock-app on esp32

[CLAassistant]

All committers have signed the CLA.

[dhrishi]

Hi @DamKast Thanks for the fix! The same issue is also seen with examples/temperature-measurement-app/esp32 as well. Would you mind making the exact same changes there?

[msandstedt]

Would it be simpler or clearer to place all chip::app::Mdns::StartServer(); calls in DeviceEventCallback?

[DamKast]

This is how it is done for the all-clusters-app example. So I am not sure that moving it in DeviceEventCallback would be clearer.

[msandstedt]

Sure, OK. I mean it's just moving the calls one function deeper.

No problem.

[kklem0]

Me and @DamKast are looking into if it makes more sense to move it into src/app/server/Server.cpp or even src/app/server/Mdns.cpp to be more generic.
Probably an #elsif in

// 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

Or in app::Mdns::StartServer().

Thoughts?

[kklem0]

To elaborate my last comment, what do you guys think of this approach instead?
I can get @DamKast to polish it for this PR if it's good.

diff --git a/src/app/server/Mdns.cpp b/src/app/server/Mdns.cpp
index 3bab44a9..157c4b5d 100644
--- a/src/app/server/Mdns.cpp
+++ b/src/app/server/Mdns.cpp
@@ -272,6 +272,21 @@ void StartServer()
     }
 }
 
+void NetworkChangeEventHandler(const chip::DeviceLayer::ChipDeviceEvent * event, intptr_t)
+{
+    VerifyOrReturn(event->Type == chip::DeviceLayer::DeviceEventType::kInternetConnectivityChange);
+
+    if (event->InternetConnectivityChange.IPv4 == chip::DeviceLayer::kConnectivity_Established || event->InternetConnectivityChange.IPv6 == chip::DeviceLayer::kConnectivity_Established)
+    {
+        chip::app::Mdns::StartServer();
+    }
+}
+
+void StartServerOnNetworkChange()
+{
+    chip::DeviceLayer::PlatformMgr().AddEventHandler(NetworkChangeEventHandler, {});
+}
+
 #if CHIP_ENABLE_ROTATING_DEVICE_ID
 CHIP_ERROR GenerateRotatingDeviceId(char rotatingDeviceIdHexBuffer[], size_t rotatingDeviceIdHexBufferSize)
 {
diff --git a/src/app/server/Mdns.h b/src/app/server/Mdns.h
index 7c13968f..e6f1ad15 100644
--- a/src/app/server/Mdns.h
+++ b/src/app/server/Mdns.h
@@ -40,6 +40,9 @@ CHIP_ERROR Advertise(bool commissionableNode);
 /// (Re-)starts the minmdns server
 void StartServer();
 
+/// (Re-)starts the minmdns server on Network change
+void StartServerOnNetworkChange();
+
 CHIP_ERROR GenerateRotatingDeviceId(char rotatingDeviceIdHexBuffer[], size_t rotatingDeviceIdHexBufferSize);
 
 } // namespace Mdns
diff --git a/src/app/server/Server.cpp b/src/app/server/Server.cpp
index 4198882d..b6e6bdf8 100644
--- a/src/app/server/Server.cpp
+++ b/src/app/server/Server.cpp
@@ -527,9 +527,10 @@ void InitServer(AppDelegate * delegate)
 #endif
     }
 
-// ESP32 examples have a custom logic for enabling DNS-SD
 #if CHIP_DEVICE_CONFIG_ENABLE_MDNS && !CHIP_DEVICE_LAYER_TARGET_ESP32
     app::Mdns::StartServer();
+#elif CHIP_DEVICE_CONFIG_ENABLE_MDNS && CHIP_DEVICE_LAYER_TARGET_ESP32
+    app::Mdns::StartServerOnNetworkChange();
 #endif
 
     gCallbacks.SetSessionMgr(&gSessions);