Replace blocking invokes with PostTask in AndroidNetworkMonitor

Use PendingTaskSafetyFlag for safe Stop. Followup to
https://webrtc-review.googlesource.com/c/src/+/209181.

Also fix rtc::scoped_refptr to work with RTC_PT_GUARDED_BY.

Bug: webrtc:12339
Change-Id: Ic0e3ecb17049f1a0e6af887ba5f97a5b48a32d98
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/211351
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Taylor <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33447}

api/scoped_refptr.h

@@ -104,6 +104,7 @@ class scoped_refptr {
 
   T* get() const { return ptr_; }
   operator T*() const { return ptr_; }
+  T& operator*() const { return *ptr_; }
   T* operator->() const { return ptr_; }
 
   // Returns the (possibly null) raw pointer, and makes the scoped_refptr hold a

sdk/android/BUILD.gn

@@ -141,7 +141,10 @@ if (is_android) {
 
     suppressed_configs += [ "//build/config/android:hide_all_but_jni_onload" ]
     configs += [ "//build/config/android:hide_all_but_jni" ]
-    ldflags = [ "-lEGL", "-Wl,--build-id" ]
+    ldflags = [
+      "-lEGL",
+      "-Wl,--build-id",
+    ]
 
     deps = [
       ":libjingle_peerconnection_jni",
@@ -565,6 +568,8 @@ if (current_os == "linux" || is_android) {
       "../../rtc_base:ip_address",
       "../../rtc_base:rtc_base_approved",
       "../../rtc_base:threading",
+      "../../rtc_base/task_utils:pending_task_safety_flag",
+      "../../rtc_base/task_utils:to_queued_task",
       "../../system_wrappers:field_trial",
       "../../system_wrappers:metrics",
     ]

sdk/android/native_unittests/android_network_monitor_unittest.cc

@@ -51,11 +51,16 @@ class AndroidNetworkMonitorTest : public ::testing::Test {
         std::make_unique<jni::AndroidNetworkMonitor>(env, context);
   }
 
-  void SetUp() {
+  void SetUp() override {
     // Reset network monitor states.
     network_monitor_->Stop();
   }
 
+  void TearDown() override {
+    // The network monitor must be stopped, before it is destructed.
+    network_monitor_->Stop();
+  }
+
  protected:
   std::unique_ptr<jni::AndroidNetworkMonitor> network_monitor_;
 };

sdk/android/src/jni/android_network_monitor.cc

@@ -21,6 +21,7 @@
 #include "rtc_base/ip_address.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/strings/string_builder.h"
+#include "rtc_base/task_utils/to_queued_task.h"
 #include "sdk/android/generated_base_jni/NetworkChangeDetector_jni.h"
 #include "sdk/android/generated_base_jni/NetworkMonitor_jni.h"
 #include "sdk/android/native_api/jni/java_types.h"
@@ -228,9 +229,12 @@ AndroidNetworkMonitor::AndroidNetworkMonitor(
     : android_sdk_int_(Java_NetworkMonitor_androidSdkInt(env)),
       j_application_context_(env, j_application_context),
       j_network_monitor_(env, Java_NetworkMonitor_getInstance(env)),
-      network_thread_(rtc::Thread::Current()) {}
+      network_thread_(rtc::Thread::Current()),
+      safety_flag_(PendingTaskSafetyFlag::Create()) {}
 
-AndroidNetworkMonitor::~AndroidNetworkMonitor() = default;
+AndroidNetworkMonitor::~AndroidNetworkMonitor() {
+  RTC_DCHECK(!started_);
+}
 
 void AndroidNetworkMonitor::Start() {
   RTC_DCHECK_RUN_ON(network_thread_);
@@ -246,6 +250,9 @@ void AndroidNetworkMonitor::Start() {
   bind_using_ifname_ =
       webrtc::field_trial::IsEnabled("WebRTC-BindUsingInterfaceName");
 
+  // Needed for restart after Stop().
+  safety_flag_->SetAlive();
+
   JNIEnv* env = AttachCurrentThreadIfNeeded();
   Java_NetworkMonitor_startMonitoring(
       env, j_network_monitor_, j_application_context_, jlongFromPointer(this));
@@ -259,6 +266,10 @@ void AndroidNetworkMonitor::Stop() {
   started_ = false;
   find_network_handle_without_ipv6_temporary_part_ = false;
 
+  // Cancel any pending tasks. We should not call SignalNetworksChanged when the
+  // monitor is stopped.
+  safety_flag_->SetNotAlive();
+
   JNIEnv* env = AttachCurrentThreadIfNeeded();
   Java_NetworkMonitor_stopMonitoring(env, j_network_monitor_,
                                      jlongFromPointer(this));
@@ -571,11 +582,11 @@ AndroidNetworkMonitorFactory::CreateNetworkMonitor() {
 void AndroidNetworkMonitor::NotifyConnectionTypeChanged(
     JNIEnv* env,
     const JavaRef<jobject>& j_caller) {
-  network_thread_->Invoke<void>(RTC_FROM_HERE, [this] {
+  network_thread_->PostTask(ToQueuedTask(safety_flag_, [this] {
     RTC_LOG(LS_INFO)
         << "Android network monitor detected connection type change.";
     SignalNetworksChanged();
-  });
+  }));
 }
 
 void AndroidNetworkMonitor::NotifyOfActiveNetworkList(
@@ -594,18 +605,19 @@ void AndroidNetworkMonitor::NotifyOfNetworkConnect(
     const JavaRef<jobject>& j_network_info) {
   NetworkInformation network_info =
       GetNetworkInformationFromJava(env, j_network_info);
-  network_thread_->Invoke<void>(RTC_FROM_HERE, [this, &network_info] {
+  network_thread_->PostTask(ToQueuedTask(
+      safety_flag_, [this, network_info = std::move(network_info)] {
         OnNetworkConnected_n(network_info);
-  });
+      }));
 }
 
 void AndroidNetworkMonitor::NotifyOfNetworkDisconnect(
     JNIEnv* env,
     const JavaRef<jobject>& j_caller,
     jlong network_handle) {
-  network_thread_->Invoke<void>(RTC_FROM_HERE, [this, network_handle] {
+  network_thread_->PostTask(ToQueuedTask(safety_flag_, [this, network_handle] {
     OnNetworkDisconnected_n(static_cast<NetworkHandle>(network_handle));
-  });
+  }));
 }
 
 void AndroidNetworkMonitor::NotifyOfNetworkPreference(
@@ -617,9 +629,9 @@ void AndroidNetworkMonitor::NotifyOfNetworkPreference(
   rtc::NetworkPreference preference =
       static_cast<rtc::NetworkPreference>(jpreference);
 
-  network_thread_->Invoke<void>(RTC_FROM_HERE, [this, type, preference] {
-    OnNetworkPreference_n(type, preference);
-  });
+  network_thread_->PostTask(ToQueuedTask(
+      safety_flag_,
+      [this, type, preference] { OnNetworkPreference_n(type, preference); }));
 }
 
 }  // namespace jni

sdk/android/src/jni/android_network_monitor.h

@@ -12,6 +12,7 @@
 #define SDK_ANDROID_SRC_JNI_ANDROID_NETWORK_MONITOR_H_
 
 #include <stdint.h>
+
 #include <map>
 #include <string>
 #include <vector>
@@ -19,6 +20,7 @@
 #include "absl/types/optional.h"
 #include "rtc_base/network_monitor.h"
 #include "rtc_base/network_monitor_factory.h"
+#include "rtc_base/task_utils/pending_task_safety_flag.h"
 #include "rtc_base/thread.h"
 #include "rtc_base/thread_annotations.h"
 #include "sdk/android/src/jni/jni_helpers.h"
@@ -147,6 +149,8 @@ class AndroidNetworkMonitor : public rtc::NetworkMonitorInterface {
   // This applies to adapter_type_by_name_, vpn_underlying_adapter_type_by_name_
   // and FindNetworkHandleFromIfname.
   bool bind_using_ifname_ RTC_GUARDED_BY(network_thread_) = true;
+  const rtc::scoped_refptr<PendingTaskSafetyFlag> safety_flag_
+      RTC_PT_GUARDED_BY(network_thread_);
 };
 
 class AndroidNetworkMonitorFactory : public rtc::NetworkMonitorFactory {