Merge changes Ic85cab22,I97791a80,I521eb50c

* changes:
  Add support for concurrent data sources.
  Make NetworkTraceHandler thread safe
  Refactor Network Tracing into separate data source

service-t/native/libs/libnetworkstats/NetworkTraceHandler.cpp

@@ -55,13 +55,12 @@ void NetworkTraceHandler::InitPerfettoTracing() {
   NetworkTraceHandler::RegisterDataSource();
 }
 
-NetworkTraceHandler::NetworkTraceHandler()
-    : NetworkTraceHandler([this](const PacketTrace& pkt) {
-        NetworkTraceHandler::Trace(
-            [this, pkt](NetworkTraceHandler::TraceContext ctx) {
-              Fill(pkt, *ctx.NewTracePacket());
-            });
-      }) {}
+// static
+NetworkTracePoller NetworkTraceHandler::sPoller([](const PacketTrace& pkt) {
+  NetworkTraceHandler::Trace([pkt](NetworkTraceHandler::TraceContext ctx) {
+    NetworkTraceHandler::Fill(pkt, *ctx.NewTracePacket());
+  });
+});
 
 void NetworkTraceHandler::OnSetup(const SetupArgs& args) {
   const std::string& raw = args.config->network_packet_trace_config_raw();
@@ -75,21 +74,27 @@ void NetworkTraceHandler::OnSetup(const SetupArgs& args) {
 }
 
 void NetworkTraceHandler::OnStart(const StartArgs&) {
-  if (!Start()) return;
-  mTaskRunner = perfetto::Platform::GetDefaultPlatform()->CreateTaskRunner({});
-  Loop();
+  mStarted = sPoller.Start(mPollMs);
 }
 
 void NetworkTraceHandler::OnStop(const StopArgs&) {
-  Stop();
-  mTaskRunner.reset();
+  if (mStarted) sPoller.Stop();
+  mStarted = false;
 }
 
-void NetworkTraceHandler::Loop() {
-  mTaskRunner->PostDelayedTask([this]() { Loop(); }, mPollMs);
-  ConsumeAll();
+void NetworkTracePoller::SchedulePolling() {
+  // Schedules another run of ourselves to recursively poll periodically.
+  mTaskRunner->PostDelayedTask(
+      [this]() {
+        mMutex.lock();
+        SchedulePolling();
+        ConsumeAllLocked();
+        mMutex.unlock();
+      },
+      mPollMs);
 }
 
+// static class method
 void NetworkTraceHandler::Fill(const PacketTrace& src, TracePacket& dst) {
   dst.set_timestamp(src.timestampNs);
   auto* event = dst.set_network_packet();
@@ -113,9 +118,23 @@ void NetworkTraceHandler::Fill(const PacketTrace& src, TracePacket& dst) {
   }
 }
 
-bool NetworkTraceHandler::Start() {
+bool NetworkTracePoller::Start(uint32_t pollMs) {
   ALOGD("Starting datasource");
 
+  std::scoped_lock<std::mutex> lock(mMutex);
+  if (mSessionCount > 0) {
+    if (mPollMs != pollMs) {
+      // Nothing technical prevents mPollMs from changing, it's just unclear
+      // what the right behavior is. Taking the min of active values could poll
+      // too frequently giving some sessions too much data. Taking the max could
+      // be too infrequent. For now, do nothing.
+      ALOGI("poll_ms can't be changed while running, ignoring poll_ms=%d",
+            pollMs);
+    }
+    mSessionCount++;
+    return true;
+  }
+
   auto status = mConfigurationMap.init(PACKET_TRACE_ENABLED_MAP_PATH);
   if (!status.ok()) {
     ALOGW("Failed to bind config map: %s", status.error().message().c_str());
@@ -136,24 +155,41 @@ bool NetworkTraceHandler::Start() {
     return false;
   }
 
+  // Start a task runner to run ConsumeAll every mPollMs milliseconds.
+  mTaskRunner = perfetto::Platform::GetDefaultPlatform()->CreateTaskRunner({});
+  mPollMs = pollMs;
+  SchedulePolling();
+
+  mSessionCount++;
   return true;
 }
 
-bool NetworkTraceHandler::Stop() {
+bool NetworkTracePoller::Stop() {
   ALOGD("Stopping datasource");
 
+  std::scoped_lock<std::mutex> lock(mMutex);
+  if (mSessionCount == 0) return false;  // This should never happen
+
+  // If this isn't the last session, don't clean up yet.
+  if (--mSessionCount > 0) return true;
+
   auto res = mConfigurationMap.writeValue(0, false, BPF_ANY);
   if (!res.ok()) {
     ALOGW("Failed to disable tracing: %s", res.error().message().c_str());
-    return false;
   }
 
+  mTaskRunner.reset();
   mRingBuffer.reset();
 
-  return true;
+  return res.ok();
 }
 
-bool NetworkTraceHandler::ConsumeAll() {
+bool NetworkTracePoller::ConsumeAll() {
+  std::scoped_lock<std::mutex> lock(mMutex);
+  return ConsumeAllLocked();
+}
+
+bool NetworkTracePoller::ConsumeAllLocked() {
   if (mRingBuffer == nullptr) {
     ALOGW("Tracing is not active");
     return false;

service-t/native/libs/libnetworkstats/NetworkTraceHandlerTest.cpp

@@ -39,6 +39,9 @@ using ::testing::Test;
 
 namespace android {
 namespace bpf {
+// Use uint32 max to cause the handler to never Loop. Instead, the tests will
+// manually drive things by calling ConsumeAll explicitly.
+constexpr uint32_t kNeverPoll = std::numeric_limits<uint32_t>::max();
 
 __be16 bindAndListen(int s) {
   sockaddr_in sin = {.sin_family = AF_INET};
@@ -83,7 +86,7 @@ struct PacketPrinter {
   }
 };
 
-class NetworkTraceHandlerTest : public testing::Test {
+class NetworkTracePollerTest : public testing::Test {
  protected:
   void SetUp() {
     if (access(PACKET_TRACE_RINGBUF_PATH, R_OK)) {
@@ -95,31 +98,49 @@ class NetworkTraceHandlerTest : public testing::Test {
   }
 };
 
-TEST_F(NetworkTraceHandlerTest, PollWhileInactive) {
-  NetworkTraceHandler handler([&](const PacketTrace& pkt) {});
+TEST_F(NetworkTracePollerTest, PollWhileInactive) {
+  NetworkTracePoller handler([&](const PacketTrace& pkt) {});
 
   // One succeed after start and before stop.
   EXPECT_FALSE(handler.ConsumeAll());
-  ASSERT_TRUE(handler.Start());
+  ASSERT_TRUE(handler.Start(kNeverPoll));
   EXPECT_TRUE(handler.ConsumeAll());
   ASSERT_TRUE(handler.Stop());
   EXPECT_FALSE(handler.ConsumeAll());
 }
 
-TEST_F(NetworkTraceHandlerTest, TraceTcpSession) {
+TEST_F(NetworkTracePollerTest, ConcurrentSessions) {
+  // Simulate two concurrent sessions (two starts followed by two stops). Check
+  // that tracing is stopped only after both sessions finish.
+  NetworkTracePoller handler([&](const PacketTrace& pkt) {});
+
+  ASSERT_TRUE(handler.Start(kNeverPoll));
+  EXPECT_TRUE(handler.ConsumeAll());
+
+  ASSERT_TRUE(handler.Start(kNeverPoll));
+  EXPECT_TRUE(handler.ConsumeAll());
+
+  ASSERT_TRUE(handler.Stop());
+  EXPECT_TRUE(handler.ConsumeAll());
+
+  ASSERT_TRUE(handler.Stop());
+  EXPECT_FALSE(handler.ConsumeAll());
+}
+
+TEST_F(NetworkTracePollerTest, TraceTcpSession) {
   __be16 server_port = 0;
   std::vector<PacketTrace> packets;
 
   // Record all packets with the bound address and current uid. This callback is
   // involked only within ConsumeAll, at which point the port should have
   // already been filled in and all packets have been processed.
-  NetworkTraceHandler handler([&](const PacketTrace& pkt) {
+  NetworkTracePoller handler([&](const PacketTrace& pkt) {
     if (pkt.sport != server_port && pkt.dport != server_port) return;
     if (pkt.uid != getuid()) return;
     packets.push_back(pkt);
   });
 
-  ASSERT_TRUE(handler.Start());
+  ASSERT_TRUE(handler.Start(kNeverPoll));
   const uint32_t kClientTag = 2468;
   const uint32_t kServerTag = 1357;
 

service-t/native/libs/libnetworkstats/include/netdbpf/NetworkTraceHandler.h

@@ -22,6 +22,7 @@
 #include <string>
 #include <unordered_map>
 
+#include "android-base/thread_annotations.h"
 #include "bpf/BpfMap.h"
 #include "bpf/BpfRingbuf.h"
 
@@ -31,6 +32,56 @@
 namespace android {
 namespace bpf {
 
+// NetworkTracePoller is responsible for interactions with the BPF ring buffer
+// including polling. This class is an internal helper for NetworkTraceHandler,
+// it is not meant to be used elsewhere.
+class NetworkTracePoller {
+ public:
+  // Testonly: initialize with a callback capable of intercepting data.
+  NetworkTracePoller(std::function<void(const PacketTrace&)> callback)
+      : mCallback(std::move(callback)) {}
+
+  // Starts tracing with the given poll interval.
+  bool Start(uint32_t pollMs) EXCLUDES(mMutex);
+
+  // Stops tracing and release any held state.
+  bool Stop() EXCLUDES(mMutex);
+
+  // Consumes all available events from the ringbuffer.
+  bool ConsumeAll() EXCLUDES(mMutex);
+
+ private:
+  void SchedulePolling() REQUIRES(mMutex);
+  bool ConsumeAllLocked() REQUIRES(mMutex);
+
+  std::mutex mMutex;
+
+  // Records the number of successfully started active sessions so that only the
+  // first active session attempts setup and only the last cleans up. Note that
+  // the session count will remain zero if Start fails. It is expected that Stop
+  // will not be called for any trace session where Start fails.
+  int mSessionCount GUARDED_BY(mMutex);
+
+  // How often to poll the ring buffer, defined by the trace config.
+  uint32_t mPollMs GUARDED_BY(mMutex);
+
+  // The function to process PacketTrace, typically a Perfetto sink.
+  std::function<void(const PacketTrace&)> mCallback GUARDED_BY(mMutex);
+
+  // The BPF ring buffer handle.
+  std::unique_ptr<BpfRingbuf<PacketTrace>> mRingBuffer GUARDED_BY(mMutex);
+
+  // The packet tracing config map (really a 1-element array).
+  BpfMap<uint32_t, bool> mConfigurationMap GUARDED_BY(mMutex);
+
+  // This must be the last member, causing it to be the first deleted. If it is
+  // not, members required for callbacks can be deleted before it's stopped.
+  std::unique_ptr<perfetto::base::TaskRunner> mTaskRunner GUARDED_BY(mMutex);
+};
+
+// NetworkTraceHandler implements the android.network_packets data source. This
+// class is registered with Perfetto and is instantiated when tracing starts and
+// destroyed when tracing ends. There is one instance per trace session.
 class NetworkTraceHandler : public perfetto::DataSource<NetworkTraceHandler> {
  public:
   // Registers this DataSource.
@@ -39,45 +90,19 @@ class NetworkTraceHandler : public perfetto::DataSource<NetworkTraceHandler> {
   // Connects to the system Perfetto daemon and registers the trace handler.
   static void InitPerfettoTracing();
 
-  // Initialize with the default Perfetto callback.
-  NetworkTraceHandler();
-
-  // Testonly: initialize with a callback capable of intercepting data.
-  NetworkTraceHandler(std::function<void(const PacketTrace&)> callback)
-      : mCallback(std::move(callback)) {}
-
-  // Testonly: standalone functions without perfetto dependency.
-  bool Start();
-  bool Stop();
-  bool ConsumeAll();
-
   // perfetto::DataSource overrides:
-  void OnSetup(const SetupArgs&) override;
+  void OnSetup(const SetupArgs& args) override;
   void OnStart(const StartArgs&) override;
   void OnStop(const StopArgs&) override;
 
-  // Convert a PacketTrace into a Perfetto trace packet.
-  void Fill(const PacketTrace& src,
-            ::perfetto::protos::pbzero::TracePacket& dst);
-
  private:
-  void Loop();
+  // Convert a PacketTrace into a Perfetto trace packet.
+  static void Fill(const PacketTrace& src,
+                   ::perfetto::protos::pbzero::TracePacket& dst);
 
-  // How often to poll the ring buffer, defined by the trace config.
+  static NetworkTracePoller sPoller;
   uint32_t mPollMs;
-
-  // The function to process PacketTrace, typically a Perfetto sink.
-  std::function<void(const PacketTrace&)> mCallback;
-
-  // The BPF ring buffer handle.
-  std::unique_ptr<BpfRingbuf<PacketTrace>> mRingBuffer;
-
-  // The packet tracing config map (really a 1-element array).
-  BpfMap<uint32_t, bool> mConfigurationMap;
-
-  // This must be the last member, causing it to be the first deleted. If it is
-  // not, members required for callbacks can be deleted before it's stopped.
-  std::unique_ptr<perfetto::base::TaskRunner> mTaskRunner;
+  bool mStarted;
 };
 
 }  // namespace bpf