router: on linux add a mutex around the queue (#6709)

UDP reception happens on an other thread, avoid data races and potential data corruption issues.

src/mesh/Router.h

@@ -8,6 +8,9 @@
 #include "PointerQueue.h"
 #include "RadioInterface.h"
 #include "concurrency/OSThread.h"
+#ifdef ARCH_PORTDUINO
+#include <mutex>
+#endif
 
 /**
  * A mesh aware router that supports multiple interfaces.
@@ -19,6 +22,12 @@ class Router : protected concurrency::OSThread, protected PacketHistory
     /// forwarded to the phone.
     PointerQueue<meshtastic_MeshPacket> fromRadioQueue;
 
+#ifdef ARCH_PORTDUINO
+    /// linux calls enqueueReceivedMessage from an other thread when receiving UDP packets,
+    /// to avoid a data race with LoRa, lock that method.
+    std::mutex queueMutex;
+#endif
+
   protected:
     RadioInterface *iface = NULL;